Final Report Summary - REFRESH (Green technology for fresh water sea-transportation based on a flexible containers system)
Executive summary:
50 million European citizens, 18% of the European population, live in countries affected by water stress problems. The forecasted variations in rainfall pattern trends, due to global climate change, aggravate this already serious situation. According to the EEA, 16 to 44 million additional people will suffer water scarcity in Southern Europe by 2070.
Project Context and Objectives:
The context: water scarcity, an increasingly serious problem
Water scarcity already affects every continent. Around 1.2 billion people, or almost one-fifth of the world´s population, live in areas of physical scarcity, and 500 million people are approaching this situation. An increasing number of regions are chronically short of water. This is both a natural and a human-made phenomenon. There is enough freshwater on the planet for six billion people but it is distributed unevenly and too much of it is wasted, polluted and unsustainably managed. Water scarcity issues severely impact on the successful achievement of most of the United Nations Millenium Development Goals regarding population access to water supply and sanitation.
The acuteness of the problem is recognised at the European Level, as it was stated in the last 6th World Water Forum in Mareseille in March 2012. Climate change is slowly but steadily turning the Mediterranean coastline into a semi-arid region, with hotter and drier summers and more frequent droughts, adversely affecting water availability. Population growth and increasing average consumption due to extensive agriculture and tourism build up the climatic factors, yielding an increase of the areas subject to water stress; Spain, Italy, Greece, Malta, Cyprus and Turkey are among the most affected countries.
Situation is especially severe in Mediterranean coastal areas and islands. Growing urbanisation and tourism demand are leading to over-exploitation of existing aquifers and reservoirs. Sea water intrusion in coastal aquifers due to over-pumping is already a major issue for a large part of Europe´s coastline.
Mediterranean coast and islands is one of the most popular tourist destinations in the world, with locations doubling the resident population in holyday season. The average tourist consumes 300 litres of water per day, double of the average household consumption. More than 3000 small coastal cities and over 400 inhabited islands are logistically isolated from the mainland water reservoirs, thus making fresh water supply harder. Different approaches have been considered in order to assure water supply for these communities.
Desalination is a process that removes dissolved salts from seawater. Desalination plants require high initial investments (around 15-20 million EUROS for a 10.000 m3/desalination plant) and require operation and maintenance costs. It is estimated that desalination water cost range between 0,40-0,60 EUROS per m3 depending on plant production capacity. However desalination plants pose several critical concerns about their high environmental impact regarding brine disposal in the natural medium and their contribution to the increase of CO2 emissions due to high energy consumption.
Everywhere in the world fresh water is considered a public resource. It is assumed that fresh water in its natural state cannot be considered as a good or product subjected to international trade law rules. This is because water is bulky, transferring or storing (by pipeline, artificial canal, bulk shipment, etc.) is quite costly, requiring large infrastructure.
Water pipelines are systems of canals used to transport water. This type of system has high costs of design, construction and maintenance and it is suitable only in case of constant need of very large quantities of water. In the case of water supply to islands development of underwater pipelines are even more expensive due to the need of pumps and related energy. Thus water pipelines require permanent infrastructure, high investment costs and energy consumption. Also high maintenance costs that are not acceptable for small-medium communities and for temporary or seasonal water supply.
Tank vessels are an alternative solution for water supply to coastal areas and islands. There are different types of ships utilized for water transportation. Tankers transport typically around 50.000 m3 of water. New water tankers cost around 30 million EUROS and recently old single hulled oil-tankers (that could not be used anymore for oil transportation) have been converted to water transport. These second-hand tankers cost around 10 million EUROS and in addition to the high initial capital cost, they require high cost of reclamation and deep cleaning of holds. Moreover the transportation of water by very large tankers involves the necessity of very large port facilities and deep draft to accommodate these huge ships and enable the loading and discharging operations. Vessels ´engines consume high polluting fuels in large quantity, around 300 kg/km for a 200.000 tons tanker. As a result water transported by tanker ships is expensive with a final cost that ranges from 8 to 12 EUROS per m3.
Water bags
Because of the limitations described in the previous section, the transportation of bulk fresh water by sea using huge plastic bags has been conceived. The first concept of large bag transportation was contrived by the inventor Barnes Wallis in the 1930´s, but the first practical manifestation was the Dunlop Dracone, invented at Cambridge in 1958 by Sir William Hawthorne. The system concept was revamped in the 1980s and 1990s when research, development and continued adaptation were explored by a few companies around the world, namely Terry Spragg and Nordic Water Supply.
Terry Sprag (US) has focused his efforts on developing the idea of linking multiple bags together in a "train" to greatly increase the total volume moved at one time. The "Spragg Bags" were each approximately 9 m in diameter and 75 m long. Italian company Ziplast was involved in the manufacturing of high resistance zippers for the connection system among the bags. This zipper is not watertight because its function was only to string together the bags in order to allow the transport of bags in series. Spragg produced a couple of bags and conducted some tests on them but eventually the bags failed due to high stresses.
Nordic Water Supply developed its 10.800 m3 bag in 1997. The company tested numerous bags, which reportedly failed due to towing stresses. The Turkish Government was interested in using the system to deliver water from Turkey to the proclaimed Turkish Republic of Northern Cyprus. Within two years at least 7million m3 of water had to be delivered annually at a cost of 2.7 million EUROS per year, with volumes growing over time but the actual transport only amounted to 4 million m3 in four years due to the frequent bag bread, notably in case of adverse marine conditions, so that the Turkish Government discontinued the contract in 2001. Besides the solution of transporting huge bulk water in a single oversize bag has not been successful owing to their hard handling both full and empty. The enormous bags indeed need special facilities during the operations of discharge and storage for the next water trip. The use of big winches in order to rewind the bags for the empty transportation is also an issue because it harms the bag material due to the induced stress.
The Monohakobi Research Centre in Japan has taken over Nordic Water Supply's waterbag technology in 2004, but up to now with scarce results. One demonstration voyage with a scaled-down prototype was organised in 2007, but since then no notable development has been reported.
REFRESH modular flexible containers system
The aim of REFRESH project has been to develop a cost effective and energy-efficient solution for the sea transport of fresh water based on a modular system of interlinked flexible containers towed by a tugboat. REFRESH approach show lower environmental impact with respect to competing fresh water supply technologies such as desalinators, and has a clear cost-effective advantage with respect to alternative tanker ships.
The breakthrough offered by REFRESH system relies on the fact that each single module is kept sufficiently small to be easily managed, but the entire system is large enough to be cost-effective as allows a flexible service adjusting the total payload to the actual needs of the receiver.
The idea to develop sea transport of freshwater using water bags in not entirely new, but the proposed solutions mentioned never encountered total success due to various technical barriers. In previous attempts the design focused on realising the biggest bag achievable in order to maximise the payload. This approach failed due to structural limitations of plastic materials used, poor design due to lack of knowledge about strength loads, extreme bulkiness and difficulty of handling of such large plastic structures.
REFRESH approach has taken advantage of the proven experience of the companies within the project consortium in order to offer the most suitable materials for the manufacture of the flexible containers.
The Spanish company INDUSTRIAL SEDO has a wide experience in the manufacturing of PVC coated fabrics for different applications. PVC coated polyester fabrics are widely used in several applications (tarpaulins, shelters, tents, canopies, liquid flexible tanks, etc.) due to low cost and optimal performance with a good combination of flexibility, toughness, extensibility and high ratio of strength to weight. They offer good chemical and weathering properties.
Within the scope of the project, INDUSTRIAL SEDO has developed reinforcing textiles based on polyester fibres with specific woven architecture in order to withstand the high demanding requirements of tensile and tear strength foreseen for the towed water bag (700 daN/5cm). In addition to this, PVC coated fabrics are able to be welded by means of high frequency method, offering an outstanding welding resistance. This feature enables the manufacture of flexible containers joining different layers of PVC coated fabrics and also joining PVC coated fabrics with tapes of zipper system.
ZIPLAST, from Italy, is a highly specialized company active in design and manufacturing of special fasteners and zippers for industrial worldwide applications. Its production is focused on custom zippers for chemical protection, fumigation, industrial applications, air-water sealing.
The zipper, produced by ZIPLAST, is the key element in REFRESH system. Connecting singles modules while retaining watertightness of the whole system is only possible through the use of a watertight zipper, which has also to be extremely strong to resist the towing load.
The zipper developed within the REFRESH project exhibited a cross-tensional strength of 24 t/m, making it the strongest watertight zipper existing in the world.
The Prague-based company SAFIBRA was founded in 1999 as a private company and has since established itself as a leader in the field of development, production, sales and applications of state of art optical systems and optical fibre sensors.
The strain monitoring system produced by SAFIBRA exploits the Fibre Bragg Grating technology to measure elongations of the fibre in an extremely precise (resolution of tenths of millimetres over one metre of fibre). Data are sent in real time to the tugboat's bridge deck as a reference for the Captain. In the REFRESH test, the sensors confirmed that deformations are well below the breaking strength of fabric even at full speed.
SPANOPOULOS, coordinating company within the Project, is a maritime Enterprise located in the island of Salamis, Greece, and active in a wide range of maritime services in the Mediterranean Sea and other areas in Europe, including vessel construction and maintenance, construction of harbours and marinas, salvage and towage with its fleet of tugboats.
SPANOPOULOS has guided design and prototyping decisions to comply with maritime regulations and ensure máximum operability of the system at sea. The company is looking forward to commercially exploit the REFRESH system for water transportation towards the Greek islands in conjunction with its fleet of tugboats.
The commitment of all the companies in the project consortium lead to the successful integration of all the elements in the REFRESH system and make possible the manufacture of a medium-size prototype in order to test the performance of the materials in real conditions.
As a main outcome of REFRESH project, a medium-size prototype was manufactured with the aim of assessing the feasibility of the proposed design and the performance of the selected materials to withstand the requirements foreseen.
REFRESH prototype consisted in two single modules connected by zippers. The prototype features 4.1 m diameter and 20 m length. Total load capacity was 200 m3. It is expected that large size prototype for commercial scale to be 10 times larger enabling 2000 m3 water load capacity.
Trials were carried out in Crete (Greece) in November 2012. Flexible container modules were deployed and assembled in the harbor by few operators. A crane helped to place the water bag into the sea in order to start the filling operations. Fresh water was pumped into water bag until roughly full capacity was reached. Once filled, REFRESH prototype float in the sea showing no instabilities thanks to floaters fitted to the water bag.
A tugboat with a main engine propulsion of approximately 2.000 HP was used for towing REFRESH water bag. Several trials were performed in order to assess the hydrodynamic performance of the flexible container. As a main outcome the REFRESH water bag was able to withstand the rough towing conditions tested; PVC coated fabric show no break or deformations and no tear or delamination was noticed in the welding lines.
Project Results:
The main exploitable results obtained by the project can be summarised as follows:
- Development of mono- and multi-material coated recyclable fabrics
- Development of a high-strength watertight zip with a resistance to lateral pull above 20 t/m
- Definition of a Fibre optics-based strain monitoring system and its application to a flexible fabric structure
- Development of a waterbag, with the following sub-objectives:
--Design of a modular waterbag overcoming the issues known from previous waterbag attempts;
--Design of a suitable towage connection transferring the towing load to the fabric without causing stress concentration;
--Fabrication of a 20 m long, 4 m diameter waterbag according to the design;
--Full scale tests with a sea voyage transporting a payload of 200 tons of fresh water
--Establishment of operational procedures and verification of their fulfillment.
1.1.3.1 Development of mono- and multi-material coated recyclable fabrics
Coated fabrics find an important place among technical textiles and are one of the most important technological processes in modern industry due the wide range of applications: protective clothing, shelters, covers, liquid containers, etc. The properties of a coated fabric depend on the type of polymer used and its formulation, the nature of textile substrate, and the coating method employed. PVC coated polyester fabrics are widely used due to low cost and optimal performance with a good combination of flexibility, toughness, extensibility and high ratio of strength to weight. In order to enhance recyclability of coated fabrics, laminates of polypropylene fabrics with thermoplastic polyolefins coating and polyester fabrics with thermoplastic polyester elastomers are proposedfor achieving homogeneous structures. In a first approach, state-of-the-art coated fabrics manufactured with polyester fabrics and PVC coating offer good mechanical properties to meet the requirements foreseen for water bags for bulk water sea transport.
PVC coated polyester fabrics are widely used in several applications due to low cost and optimal performance with a good combination of flexibility, toughness, extensibility and high ratio of strength to weight. They offer good chemical and weathering properties.
The industrial manufacturing process is based on a coating method that applies a PVC solution or plastisol onto the polyester fabric. The polymeric material is applied on the substrate and then metered. The coated fabric pass through a drying oven where the solvents are evaporated and the polymeric material forms a solidified and cured layer.
This process is well established at industrial level and allows for efficient production rates. PVC coating on both sides of the polyester fabric can be achieved in a continuous process. PVC coated fabrics are delivered in reels to be used in different applications: tarpaulins, shelters, tents, canopies, liquid flexible tanks, etc.
Recycling of PVC coated polyester fabrics is not an easy or a common since the family of the polymer used in manufacturing the fiber and the coating compound are heterogeneous, hence their physical mixing to regenerate in the form of recyclable goods is not possible even by applying high temperature or pressure.
Coated PVC polyester fabrics are manufactured in standard width and lengths reels. Individual applications demand specific size and shape, depending on the process of manufacturing, so that joining techniques with adhesives, stitching, heat welding, and high frequency welding are employed.
In order to overcome the recyclability issues of PVC coated polyester fabrics and to enhance environmental behavior of reinforced laminates, two different alternative homogeneous laminates have been proposed combining thermoplastics extruded sheets and fibers from the same polymeric material:
- Homogeneous structure of polyolefin based laminate: TPO thermoplastics liners and PP fiber reinforcing fabric.
- Homogeneous structure of polyester based laminate: TEEE thermoplastics liners and polyester fiber reinforcing fabric.
Thermoplastic polyolefin (TPO) coatings are gaining relevance in engineering applications due to their advantage over PVC coated fabrics.
TPO refers to polymer blends consisting of some fraction of polypropylene (PP), polyethylene (PE), block copolymer polypropylene (BCPP), rubber and a reinforcing filler. TPOs do not contain plasticizers, therefore the problem of plasticizer loss associated with some plasticized polymers (as PVC) is eliminated.
TPO are basically inert towards chemical and microorganism attack. The finished products have good resistance towards oxygen and ozone and are flexible at very low temperature (-60ºC). The products are odorless and do not give out toxic gases on burning. TPOs liners are lighter that PVC or PU since polyolefins are lower in density, this feature enhances buoyancy of flexible tanks for sea transport.
In order to achieve multilayer homogeneous laminates combining fibres and polymeric coating of similar and compatible materials, a search task has been done for selecting appropriate TPO grades and PP fibre fabric to manufacture laminates with more favourable environmental characteristics and fully recyclability after use and through disposal since the coating and the reinforcing fabric are homogeneous polymers hence are melt recyclable, which is not possible in the case of PVC coated polyester fabrics.
TPO resin flexible polypropylene Hifax CA 10 A has been chosen as polymeric coating. This material is typically used in geomembranes and liners for waste water treatment reservoirs, floating covers, aquaculture ponds, storage reservoirs, etc. According to technical data provided by resin manufacturer, Hifax CA 10 A exhibit excellent resistance to puncture, mechanical toughness and high tear strength. Chemical resistance is also a main advantage.
Polypropylene high toughness fiber fabric Murafil provided by INDUSTRIAS MURTRA has been chosen due to commercial availability and good performance regarding low specific density, good thermal resistance, low water sorption, high abrasion resistance and good weatherability.
Main drawback of polyolefin sheets and fibers rely on low surface tension, offering poor adhesion properties. This fact will be addressed in the trials for manufacturing reinforced laminates selecting appropriate adhesion promoter for enhancing adhesion between sheets and fabrics.
Thermoplastic polymers are processed by extrusion melting the material in a heated barrel while a rotating screw transport the solid granulates. This melt is extruded through a flat die vertically downward into a nip of the coating roll and over the fabric. This method, known as extrusion coating, differs from the fluid platisol coating method used for PVC coating fabrics.
Thermoplastic polyester elastomers are block copolymers consisting of a hard (crystalline) segment of polybutylene terephtalate and a soft (amorphous) segment based on long-chain polyether glycols. They are also referred as thermoplastic elastomer ether ester (TEEE). Properties are determined by the ratio of hard to soft segments and by the make-up of the segments.
This type of polymeric materials combines many of the most desirable characteristics of high-performance elastomers and flexible plastics. It features: exceptional toughness and resilience, high resistance to creep, impact, tear and flex fatigue; flexibility at low temperatures and good retention of properties at elevated temperatures (up to 165ºC). In addition, it resists many industrial chemicals, oils and solvents.
The excellent properties of TEEE qualify it for a number of demanding applications where mechanical strength and durability are required in a flexible component. Main drawback relies on high price of this type of resins which limits its use for high value products, mainly in the automotive industry, electronic appliances and sporting goods.
In order to achieve multilayer homogeneous laminates combining fibers and polimeric coating of similar and compatible materials, a search task has been done for selecting appropriate polyester thermoplastic elastomer grades and poliester fibre fabric to manufacture laminates with more favourable environmental characteristics and fully recyclability after use and through disposal since the coating and the reinforcing fabric are homogeneous polymers hence are melt recyclable, which is not possible in the case of PVC coated polyester fabrics.
TEEE resin Hytrel 4056 has been chosen as polymeric coating. This material is typically used in hoses, cable coatings, sport apparel and other industrial applications. According to technical data provided by resin manufacturer, Hytrel 4056 is a plasticizer free compound that exhibits excellent flexibility, high resilience and excellent flex crack resistance.
Polyester fiber fabric provided by INDUSTRIAL SEDO has been chosen due to commercial availability and good performance regarding high thermal resistance, low water sorption, high abrasion resistance and high mechanical strength.
Thermoplastic polymers are processed by extrusion melting the material in a heated barrel while a rotating screw transport the solid granulates. This melt is extruded through a flat die vertically downward into a nip of the coating roll and over the fabric. This method, known as extrusion coating, differs from the fluid platisol coating method used for PVC coating fabrics.
A pilot production of the new TPO and TPEE laminate was started at AIMPLAS. In order to simulate the extrusion coating process at pilot plant level and obtain appropriate samples for further mechanical characterization, a two-stage process was carried out at AIMPLAS facilities:
- First stage consisted in thermoplastic sheet extrusion.
- Second stage consisted in coating of reinforcing fabric using a manual method in hot platen press.
1.1.3.2 Development of a high-strength watertight zip with a resistance to lateral pull above 20 t/m
A zip fastener is a commonly used device to temporarily join together two strips of textile. It basically consists of two half-chains of elements, or teeth, attached to two strips or pieces of fabric. When the teeth half-chains are forced to interlock by means of a cursor, they join together the two fabrics.
Zips are used in all kinds of garments as an alternative to buttons; in the last decades, the availability of high performing materials for teeth opened up new market segments for zips as alternatives to conventional means of fixing or adjoining textile or net structures.
An example of this is the use of high strength zips to assemble the large nets used in aquaculture. Those zips are able to withstand tensional loads up to the order of 10 tons per linear meter. Passage of water through the zip teeth is not an issue in this case, as both sides of it are immersed in sea water.
In other applications, such as scuba diving suits, water-sealing zippers have been conceived, which are able to separate a dry side on the inside from an outer wet side. These zips usually achieve the sealing effect by adding a tiny gum strip on tooth profile, so that when teeth are joined together, the gum strips effectively form a gasket. This configuration only holds when no considerable tearing force acts on the zip, as any relative displacement of the half-chains would break the seal.
One of the basic innovations of the REFRESH zipper approach is decoupling of the tensional strength function from the water tightness function, achieving both functions through the use of independent (yet coupled) elements.
All the load is taken by interlocking teeth, which feature a U-shaped profile. Each of the teeth has two side prongs interlocking in between the "bellies" of adjacent U-shaped teeth, thus obtaining mutual engagement.
This coplanar configuration, symmetrical with respect to the tensional force plane, was chosen so that all tensile loads are distributed on the tangent plane; this avoids out-of-plane normal reactions possibly leading to unlocking of the zip.
The weakest point of the chain is located at the end of the straight part of the tooth, at the root of the curved part. This is where the load from side prongs of the other half-chain of teeth is applied, moreover here a geometrical discontinuity is observed (passing from straight to curved geometry).
Finite Elements simulations were carried out on the chain model to assess its resistance to lateral pull: the first partial results from simulations confirm this mode of failure as the preferential one.
The first prototype of the zip was made according to this design: teeth chains were made in polyoxymethylene (POM) loaded with glass fibres for higher resistance. The chain was formed by injection moulding, which required design and fabrication of a dedicated mould.
The pre-prototype chains were sewn to a Vectran-based side tape. Vectran was used on weft, while warp, not taking significant loads, was made in polyethylene.
A tear strength test was performed on the zip, obtaining breakage at 800 kg/5 cm, which corresponds to 16 t/m.
The test was performed at ZIPLAST facilities by fixing one side of the zip pre-prototype in a vice, while subjecting the other to a lateral pull increasing up to 800 kg over a length of 5 cm. This is a standard test used to evaluate the tear resistance of textiles and zip closures.
This first prototype featured an asymmetric section, i.e. the sealing membrane was set on a different plane with respect to the teeth interlocking plane. While this configuration is suitable from the mechanical point of view, there was concern that it could facilitate decoupling of the teeth during use. The shape of the tooth was then changed to accommodate the sealing membrane in half position. The second zip prototype is shown below.
The second prototype exhibited a breaking strength exceeding 24 t/m. after the successful outcome of this test, mass production for the full scale prototype begun. 24 m of zip were included in the prototype.
Water tightness tests were performed by closing a pressure vessel with a sheet of fabric sealed by a zip sample. Water inside the container was then put under increasing pressure until witnessing the formation of bubbles. At a pressure of 0.6 bars, bubbles started forming on the welding line between zip tape and fabric, but not between the teeth.
The zip fastener developed by the REFRESH project was able to resist to a lateral pull of 24 t /m, making it the strongest watertight zip fastener existing to date.
1.1.3.3 Definition of a fibre optics-based strain monitoring system and its application to a flexible fabric structure
The selected sensing technology is based on the use of Fibre Optics. Fibre optic sensors act on the principle of transmitting a light signal through the fibre and measuring the status of the returning or transmitted signal. The change in signal properties is then translated into appropriate quantities that allow the measurement of a wide range of mechanical, physical, and chemical quantities. Fibre Bragg Grating (FBG) is a short segment of an optical fibre with a periodically varying refractive index in the core of the fibre. Such segments then act as a mirror reflecting only a specific wavelength of light propagating through the fibre and which is incident on this segment. The rest of the spectrum is transmitted.
A Bragg Grating is a local modification to the internal structure of the fibre that causes it to reflect light of essentially one wavelength while allowing all other wavelengths to pass. The perturbation of the grating by the measure and causes an extension of the fibre and, with that, the increased separation of the grating elements and a change in the characteristic wavelength observed. The wavelength reflected varies, depending on the temperature or strain to which the fibre in the region of the grating is subjected. This wavelength change is detected by means of optical spectroscopy and is interpreted as a change of corresponding physical quantity measured.
Bragg gratings are powerful tools for the sensor designer, as they are versatile, they can be multiplexed to create a series of quasi-distributed sensors along a fibre network
The partner SAFIBRA has selected as suitable optical monitoring system for the REFRESH system the use FBG glass fibre. The choice is supported by the following characteristics, which generally match very well with the system requirements:
- EMI resistent, dielectrical, passive fibre installation;
- already in use in other applications with proved reliability, robustness and resistance to harsh environment, long-life and maintenance-free;
- ability to measure linearly without hysteresis (based on elasticity of glass fibres);
- ability to measure elongation of the glass fibre up to 5%;
- static or dynamic measurements are possible;
- high precision: submicron resolution for 1m sensor resolution 1,0000001 (at 7 Hz sampling rate)
- high sampling rate for dynamic measurements
The first prototype of the REFRESH fibre monitoring system consisted essentially in a "naked" optical fibre enclosed in a fibreglass tube. This setup worked well in the laboratory, demonstrating the viability of the technology, but proved to be too fragile in the first trial at sea with a small waterbag, carried out at SPAN premises at Salamina, Greece.
The anchoring points were covered with a patch of fabric, glued to the surface with the epoxy glue. A supplementary layer of tape was added to seal the perimeter; however the tape did not perform well in water. Epoxy held well in water; however after the test it was easy to peel off the patches to expose again the fibre, perhaps due to a too thick layer of epoxy used. This could become dangerous in case of accidental sliding contact of patch edges.
The electronic box is waterproof, thus for this test it was just anchored to the surface of the bag with tape. It proved to be a good solution which survived well the test. When it was removed after the test, no water was found inside the box, apart some small droplets on the cover, despite it being completely submerged for long time.
The prototype was lifted down to the sea and filled.
The optical fibre broke when lowering the prototype in the sea due to excess bending of the container. Even if the operation was performed as carefully as possible, the weight of the bag caused sharp bending of the fabric between the two lifting points. The fibre was damaged during lifting down, before the prototype actually entered the water. Since it is not possible to avoid bending (moreover it is not realistic to require the crew to perform too precise or careful handling of such equipment), a re-thinking of the design was necessary to protect the fibre from excess bending.
After this first trial, it was decided to fabricate a new batch of sensors with an additional layer of protection. The fibre was enclosed in two concentric tubes, a spiralled metallic one and an external rubber one.
Also the anchoring mechanism was changed: in the first version was realised by means of epoxy glue, but it proved to be impractical in the event of having to remove it, for maintenance or for the storage of the system. The new version of the anchoring system was realised by means of bolts and screws: a faster, firmer and much more elegant connection system.
The monitoring system prototype was tested at Cambrils, Spain. It was composed by a 70 centimeters long sensor and an electronics box. The fiber and box were covered by plastic pockets prepared by SEDO.
The small waterbag with the fibre system installed was towed by a boat. Signals recorded by the monitoring system during towage are reported in the graph below.
The fibre optics system performed well in this trial, so the same scheme was kept for the final prototype.
1.1.3.4 Design of a modular waterbag overcoming the issues known from previous waterbag attempts (confidential)
The REFRESH concept consists of an evolution of the so-called "waterbag" technology transporting bulk quantities of water across the sea by means of large flexible barges towed by tugboats, examples of which exist since the 1980s. Such systems can be used to transfer water from water-rich to water-poor areas even at long distance; however, despite the research efforts, none of the proposed waterbag concepts has up to now reached a commercial product phase.
Two main categories of waterbags had been proposed in the past, either being based on huge monolithic containers or on trains of smaller containers, each one being sealed on itself, connected via ropes or fabric sleeves. Each of the conventional designs despite being technically sound has intrinsic drawbacks that have prevented all past waterbag projects from reaching commercial success.
The key innovation introduced by REFRESH is the use of open modular containers.
This new structure, enabled by the use of a unique watertight high-strength zip closure (one of the most notable results of the research project), has improved handling, reliability and time-efficiency by orders of magnitude with respect to previous waterbag attempts.
The REFRESH modular concept
Each module is open on itself, it is closed by the adjoining one
A train of modules is formed and each compartment is loaded
After discharge, the train of modules is unzipped
Handling and retrieval is performed at the level of single modules
The "open modules" concept has four fundamental advantages over monolithic designs and trains of separate modules, exploiting the strong points and avoiding the weak points of both approaches:
1. Unlike monolithic designs, it allows compartmentalisation, so that if one module is damaged only a fraction of the payload is lost and the rest remains intact; moreover, when not in operation the system can be managed at the single module level, enabling much easier handling and minimising logistic problems;
2. When assembled, the full system behaves "as one", avoiding snaking and excess bending problems that may arise when towing trains of separate containers linked by ropes or fabric sleeves;
3. Upon discharge, the small fraction of the payload that cannot be retrieved by pumps (a fraction that may weigh several tons) can flow through the open side. Sealed modules (either in a "monolithic" or in a "train" configuration) wouldn't allow this and the weight of the remnant water would require large cranes to lift the system off water. In comparison, a REFRESH module can be lifted using the small crane present as standard equipment on every tugboat;
4. The open side allows easy access to the interior of the modules for cleaning and sanitising, a huge issue in sealed systems.
1.1.3.5 Design of a suitable towage connection transferring the towing load to the fabric without causing stress concentration
One of the main issues related with the towage connection system was the effective distribution of stresses.
As a general rule, moreover valid when dealing with flexible structures, concentration of stresses should be avoided. A further problem is potentially represented by friction between the textiles and the metallic parts of the connection. One of the earliest ideas to overcome this issue was to devise a non-metallic (e.g. plastic) connection; this idea was soon discarded because of the problems posed by non-metallic elements in the maritime environment in terms of performance, corrosion and generally lifetime.
Three early conceptual designs of the towage connection, proposed by DAPP to the project partners, are reported in the following:
A flat metallic flange is used to restrain the bow part. A bundle of secondary towing cables is departing from the primary one; they are fixed to the flange, either in its front face or on the side circumference. Having multiple circumferentially-disposed fixing points, instead of a single one in the middle, is helpful in avoiding spinning.
There are two ways in which the fabric can be adjusted to the flange: either it is cut to the precise shape of the bow leaving a free circular edge to be clamped between the two faces of the flange, or it is folded and clamped.
The fabric is wrapped around a transversal bar and then clamped or fixed by a further strap. This design option would give the bow section of the prototype a flattened shape, which could be beneficial for stability; however, the folded fabric would create preferential force propagation lines, which could lead to high stress concentration. With this option, two cables would depart from the primary towing cable and would be fixed to the sides of the bar.
In the third option, the reinforcing belts running longitudinally on the prototype are directly connected to the secondary towing cables. With this method, the towing load is directly transferred to the belts: in principle the fabric does not sustain any load. In the real case, a fraction of load is transferred to it by the seams linking belts and fabric, but only as a second order effect.
Since the reinforcing belts were in the end excluded from the final design of the container, this design option was discarded. The chosen option for detailed design and prototyping was number 1, featuring a metallic flange.
Towage trials with the small prototype showed evidence of the effect of a completely submerged conical bow, tending to cause immersion of the prototype when crossing the ship's wake.
It was argued that the conical bow, featuring an equal upwards and downwards water flow when moving in still water, is strongly affected by any turbulence.
In particular, when the conical bow impinges on a water front which is moving upwards (e.g. when entering the wake), the upward water flow over the cone pushes the cone downwards; the opposite happens when impinging over a water front which is moving downwards (e.g. exiting the wake).
This fact led the project group to devise a modification in the design of the bow, proposing a lifted bow.
DAPP performed numerical simulations on both front module designs to assess their behaviour under towage, highlighting the best performance of the "lifted nose" solution.
Two designs of the towage connection were proposed by DAPP. In the first version, the clamp is realised in the perpendicular plane with respect to towing, requiring that the fabric be folded over the inner plate.
The second and final version of the towing connection flange counteracts the potential risks tied to folding the fabric over the metallic flange. The purpose of this flange design is to transfer clamping from the perpendicular to the parallel plane with respect to the towing line; this in turn avoids the need to fold the fabric over the metallic part.
1.1.3.6 Fabrication of a 20 m long, 4 m diameter waterbag according to the design
The prototype has been designed with modular elements, joined by zippers.
The conceptual design originally foresaw the possibility of including reinforcing belts running along the length of the prototype.
These items would prove particularly helpful to relieve stress from the textile by taking the direct towing load, but have the drawback of creating preferential loading lines: if the loading line propagates up to the vicinity of the zipper, it could cause load concentration on a small section of the zipper, potentially leading to unzipping. These considerations were taken into account at the final design stage: the outcome of the tensile strength tests on textiles proved that it will be possible for them to sustain the towing load, making it possible to avoid the use of reinforcing belts; in the final design, the belts were not included.
1.1.3.7 Full scale tests with a sea voyage transporting a payload of 200 tons of fresh water
The final outcome of the REFRESH project was the development and successful testing of a 20 m long, 4 m wide prototype (around 200 m3 of payload) featuring the "open module" scheme. The technological feasibility of the concept was proven with the successful delivery of a 200 m3 freshwater payload with a 16 nautical miles sea voyage in the gulf of Souda, Crete, hosting one of the operational bases of Spanopoulos Group's fleet of tugboats.
The bay of Souda is protected from northern winds by the Akrotiri peninsula; the port is quite busy in the summer season but it does not feature a lot of traffic in other periods; it has plenty of space available on the docks and is equipped with 2 inch hoses for filling freshwater in boat tanks: all these factors contributed to make it an ideal location for the tests.
The route established by SPAN's Captain foresaw a length of 8 nautical miles from the harbour of Souda to the mouth of the bay,to be covered twice (back and forth) for a total of 16 nautical miles.
The first part of the voyage was used by the tugboat crew to gain confidence with the prototype. Speed was kept at a limited pace (2-3 knots) and the towing line was limited to 30 m until exiting the port area.
In order to acquire experience with the behaviour of the prototype under manoeuvring, the Captain made a series of turns, each between 30 and 45 degrees.
In this first phase, it was observed that the prototype tended to snake under its own inertia, not being able to follow the tugboat movement correctly. Even when the tugboat followed a straight line (always keeping a moderate speed), the snaking movement continued.
The towing line was then elongated up to 100 m and the behaviour of the prototype changed completely. No snaking effect was observed at this time, making it possible to increase the speed of the tugboat towards cruise speed.
The prototype continued to behave nicely and the elongation reported by the sensors continued to be well below the ultimate breaking strength of the material: this prompted the consortium to ask the crew to continue acceleration above the foreseen speed. The speed was then brought to 6 knots, without noticing any change in the behaviour of the prototype.
The Captain stopped acceleration before reaching the 7 knots mark, which is the maximum limit conventionally respected for boat towage.
The ramp from nearly zero speed to 6 knots was performed in less than 15 minutes. This acceleration was much faster than initially foreseen when designing the system.
When reaching the mouth of the bay, the tugboat considerably decreased speed until stopping. The prototype decelerated smoothly and stopped in a short space (less than the length of the towing line). The tugboat made a 180° turn at low speed and the prototype followed, finding alignment with the new direction in a short time (around two minutes).
The tugboat then ramped up speed to 6 knots for the return leg. Again, none of the snaking behaviour experienced with the short towing line was observed.
When reaching the harbour area, the tugboat stopped and the towing line was shortened to less than 5 m. The tugboat approached the dock at low speed, allowing the prototype in tow to come alongside the dock in a smooth manner
1.1.3.8 Establishment of operational procedures and verification of their fulfillment
A handbook for operation of the REFRESH waterbag system was prepared by DAPP and SPAN. This document is a guidance for the use of the system, providing directions to the tugboat crew for transporting, assembling, deploying, using and retrieving the system.
The module assembling procedure can be carried out in two different ways: relatively short waterbags can be assembled in one single step directly on the dock, then lowered in the sea; this system is unpractical for larger waterbags: in this case, the modules are joined continuously as the bag is lowered.
Potential Impact:
1.1.4.1 Wider impact and correspondence to EU policies
Water scarcity is a global problem and is not confined to "poor" nations. Considering Europe alone, REFRESH represents a cost effective and flexible technology for supplying fresh-water to coastal small cities and island with less than 300.000 inhabitants where live about 45 million of European citizens . 65% of these communities, that double in size during summer with tourist presences , are affected by growing water scarcity due to several factors as climate change, growing urbanisation of coasts, tourism, sea water intrusion in aquifers.
Water scarcity is also a major concern in the Middle East, where most countries have only less than 500m3/capita/year of water available. The annual volume of actual renewable water resources per capita is 261m3 in Israel, approximately 90m3 in Palestine, and 164m3 in Jordan, while water-rich countries such as the United States have more than 10,000m3.
One of biggest challenge in the Arabic Gulf region is water, which may be everywhere in the Gulf but is undrinkable without desalination. Desalination plants produce emissions of carbon dioxide that have helped give Dubai and the other United Arab Emirates one of the world's largest carbon footprints. They also generated enormous amounts of heated sludge which is regrettably pumped back into the sea.
For these communities REFRESH will represent the most effective solution for fresh-water supply service because traditional technologies as water pipelines, desalinisation plants and large water vessels are not a feasible solutions due to financial, environmental and technical barriers.
REFRESH would enable the low cost transport of large amounts of fresh water from regions where it was abundant to regions where it was scarce. Some potential water transport routes are given in the table below. Clean fresh water is vital for agriculture, industry, and personal use. A consumption rate on the order of 600 cubic meters per person per year of fresh water is needed for an adequate living standard. The continuing depletion of aquifers and the growing world population will require increased sources of fresh water in the future. By 2050 AD, world population is expected to grow to 9 billion people, with an annual fresh water deficit of 2x1012 cubic meters (2000 cubic kilometers) per year. Much of this deficit will be in China, the Mid-East, and Africa. REFRESH can help to mitigate this water deficit.
The results of REFRESH encompass different fields and applications, each leading to a substantial impact on the European industrial scenario. These impacts are both direct, due to the use of components developed within the project, and indirect, exploiting REFRESH technological solutions in different fields:
- Reduce environmental cost of water industry: REFRESH water supply system, consuming low energy and with practically no environmental impact due the use of solar energy and recyclable materials is an important improvement on developing a low environmental impact European industry, fully supporting the competitiveness of water sector on the international market.
- Support the Tourism Industry, one of the leading sectors in Europe, especially in Mediterranean seaside locations with an estimate of 235 million tourists per year and an occupation of 4 million people, will benefit from increased water availability without environmental drawbacks thanks to the application of the REFRESH water supply paradigm, increasing the touristic appeal and marketability of European coasts and helping overcome the competition from extra European destinations;
- Support the European Textile sector, that in the latest years suffered by Far Est competition on low value products. The Textile sector will greatly benefit by the project innovative products as high recyclable strength multilayer laminates combined with high performance zippers in the growing sector of tensile architectural structures, overcoming the limitations caused by current hook and loop joints and allowing a substantial expansion of the textile architecture market, currently estimated at 13 billion EUROS;
- Increase safety of European workers and citizens because they will benefit by the development of the flexible fibre optics monitoring systems that could dramatically increase the possibility to continuous in-service monitoring of critical structures.
In particular, we envisage the REFRESH innovation will have an impact on different applications:
- Fresh water for agricultural and industrial use: this is clearly the area where REFRESH will have a direct impact. We will target both seasonal needs (i.e. the case of a small isle where in Summer the tourist presence is high and the request for fresh water is far higher than the quantity required by the local inhabitants) as well as the case of a continuous delivery of fresh water all year round, as is the case of water for industrial use.
- Fresh water for areas of crisis: In case of disasters such as earthquakes, tsunamis, and others happening in coastal regions the first and most urgent need after rescue operations are finished is usually clean water. The system being modular offers the possibility to assemble the train of bags which would fit best the particular need and disaster scenario. The modular bags and they can be made any size can be pre-positioned throughout the world, folded and stored. In a disaster, they can be immediately filled with freshwater from any safe source, such as surviving municipal systems, rivers etc. and towed through the oceans to places of need or they can be driven or flown, empty, to the site of a disaster and filled locally
- Real Estate: even though the profits to be generated from the implementation of a REFRESH waterbag transport system are significant, the profits to be generated from the increase in the value of the land to which the water is to be delivered will be even more significant. The introduction of a viable and reliable water supply will significantly increase the value of real estate where ever waterbag water is delivered.
In the context of water supply, sustainability means developing water sources that are cost-effective and that can be maintained in the long term without compromising important social and environmental parameters. Actual methodologies for fresh water supply are not fully sustainable:
- Desalination is not an ideal solution as there are many potential environmental, social and economic risks associated with seawater desalination. Desalination plants pose several critical concerns about their high environmental impact due to the operation of desalination stations, they being related mainly to brine disposal in the natural medium. A major constraint to this system is the energy consumption per m3 produced (between 0.3-0.5 million EUROS per 10.000 m3/day desalination plant)Error! Bookmark not defined. That account for 30 to 60 percent of the operational costs. In summary desalination contribute in the increase of CO2 emissions: one cubic meter of desalinated water consuming 5.3 kWh of electricity and emits nearly 5 kg of CO2.
- Water pipelines require permanent infrastructure, high investment costs, high energy consumption, difficult maintenance that are not acceptable for small-medium communities and for temporary water supply. Building an underwater pipeline results in an irreparable damage of sea bed along the whole length of the pipeline.
- Tank vessel consume high polluting fuels in large quantity, around 300 kilos/km for a 200.000 tons tanker.
REFRESH, on the other hand, will have a low impact on the environment, thanks to the null infrastructure requirements and low fuel consumption of the tugboat (around 20 times less than a tanker ship). The modularity and readiness of use of REFRESH allows a full compatibility with all existing tugboat classes, hence not requiring the building of new ships and allowing a more effective use of the existing naval resources. Compared to actual water barges, towing using tugboat is more energy efficient when it is considered that in the return way both are unloaded; moreover, recent progresses on tugboat design demonstrate that it is possible to further cut emission by 20 to 30 per cent and allow for fuel saving in the range of 35 per cent.
A preliminary LCA performed during the original REFRESH project yielded a lifecycle environmental fingerprint two orders of magnitude lower than a tanker barge of comparable size.
Assuring that all its citizens have access to safe, good quality water according to their needs is a major concern for the European Union. The first legislative actions to harmonise and regulate the water supply framework throughout Europe dates back to the very origins of the Union, in the 1970s, with the 1975 Surface Water Directive, its 1979 Daughter Directive on Sampling and Analysis, the 1977 Decision on Exchange of Information on Surface Waters and finally the Drinking Water Directive , issued in 1980 and revised in 1998; the issue of water availability is one of the hot topics of European policy action today, as demonstrated by the strong message conveyed by the President of the Parliamentary Assembly of the Council of Europe (PACE), Mr. Lluís Maria de Puig, at the Fifth World Water Forum, held in Istanbul in March 2009. Mr. de Puig stated that "access to water should be recognised as a fundamental human right. A rights-based approach to water would be a very important means for civil society to hold their governments accountable for ensuring access to an adequate quantity of good quality water as well as sanitation".
In view of the forum, the European Parliament issued a resolution stating that "water is a shared resource of mankind" and "access to drinking water should constitute a fundamental and universal right". The same resolution calls the Parliament and Commission to make an additional effort to guarantee access to water for the most deprived populations by 2015.
The major challenge provided by water scarcity and droughts has been recognised in a communication from the European Commission in which it is estimated that at least 11% of Europe's population and 17% of its territory have been affected by water scarcity to date, with the cost of droughts in Europe over the past thirty years amounting to 100 billion EUROS.
1.1.4.2 Foreseen economic impact for the SME participants
The price of fresh-water supply with current tanker ship services ranges from 5 to 8 EUROS per m3 in Greek islands and around 7 EUROS per m3 in Italy. Based on these values, a detailed estimation of REFRESH costs and final water price has been performed by SPAN on the basis of its experience with water supply by tanker barge and tug boat operation and considering a trip distance of 60 km.
Tugboat maximum consumption is around 10 l/km of fuel at full towage and 4 l/km when no-towing, which gives a total fuel expense of 1000 EUROS with current fuel prices. The daily personnel cost of a 3 men crew accounts approximately for other 1000 EUROS. The cost of freshwater at the source amounts to 0.30 EUROS per m3; an estimation of the cost of electricity required to operate the pumps for load and unload of water is around 0.10 EUROS per m3. The total costs of operating REFRESH for supply on a 60 km route amount thus to 4000 EUROS.
This commercial scenario allows fixing the final price of water at 2 EUROS per m3, with an important reduction compare to actual prices in order to gain quickly important market share, yielding to a profit per voyage of 6000 EUROS.
REFRESH will be also competitive with seawater desalination, which is the directly competing technology, whose final water price is around 4 EUROS per m3. Brackish water desalination can yield lower prices, around 1 EUROS per m3, but the environmental and logistic concerns and high capital costs make it inconvenient for a small coastal community. Moreover, an abundant brackish water source is not easily found in Mediterranean islands.
On the basis of the considerations reported above as well as considering the collateral markets, the overall foreseen economic impact for the SME participants of REFRESH can be summarised as follows:
SPAN, the end user within the project, will highly benefit from the project outcome. Its activities already include the supply of fresh water in small to medium quantities to military ships, which is currently performed using a self propelled water barge. REFRESH gives them the opportunity to enlarge this business and extending it to different - and larger - end users such as island communities, both for household and agricultural consumption, touristic locations and emergency supply to drought-stricken coastlines. Its locations, indicated by the star symbol in the map on the right, in Salamis (island in the Saronic gulf, in front of Athens) and in Crete represent a strategic crossroad enabling easy reach of all Saronic, Cyclades and Southern Aegean islands, which have the biggest market potential in south-eastern Mediterranean due to their geographic position and the high demand in summer months caused by massive tourism: the total potential market for fresh water supply to the Greek islands is estimated at more than 100 million EUROS per year. Considering a conservative market penetration of 2% in three years after project completion, SPAN will increase its annual turnover by 2 M EUROS.
SAFIBRA will exploit the development of the stress/strain monitoring system for application to flexible structures and marine structures a growing market segment that until now has been generally addressed by standard sensing technologies were application of fibre optics technologies is so far limited. The new miniaturised sensing device with Wi-Fi transmission capabilities developed by SAFIBRA within REFRESH represents a significant step forward with respect to the state of the art of fibre optic technologies, and open new markets for SAFIBRA in addition to the REFRESH application. Laboratory trials and sea trials of the REFRESH system in Chania, Crete, demonstrated that the signal can be reliable transmitted for distances up to 500 metres, which was significantly far better than the 100 metres limit targeted in this application.
Several thousands of waterbags would be required to cover a small amount of the total request of freshwater in the selected routes. For instance, considering a 10.000 m3 REFRESH configuration, the delivery of about 400 waterbags per year will be required to cover just the 5% of the total request of freshwater needed by Cyprus. Considering that each waterbag will have at least one monitoring unit provided by SAFIBRA, and a cost for each single unit of the order of 5.000 Euros, the expectation for this company is to increase its turnover of about 2,0 M EUROS per year.
SEDO will be in charge of the production of the material for the manufacture of the waterbag itself, with the required mechanical properties and stringent requirements in terms of resistance to the harsh marine conditions, UV rays and, at the same time, compliant for transportation of water for human consumption.
Apart from main water tankers use, secondary applications for this new product include:
- large flexible liquid container for food and beverages, but also for chemical products, fuel, water for irrigation or fireguard reservoirs;
- textile components for all kinds of marine applications, for instance aquaculture, thanks to the high resistance to saltwater corrosion and environmental compatibility of the material;
- tensile structures and the like in technical textile architecture, thanks to the high resistance to stress and UV rays.
Considering the targeted production of 400 waterbags/year as described above, the total quantity of material needed amounts to about 500.000 square meters of coated fabric. Considering a unit price for square metres of material of about 1,7 EUROS per sqm, the total increase in revenue for SEDO would sum up to about of 850.000 k EUROS per year.
ZIPLAST will enlarge its business opportunities by exploiting the unique watertight high strength zipper, having unparalleled performance by competitors. Zip closures are the fastest and easiest way of connecting adjoining textile parts: the enhanced properties of the REFRESH zipper will boost its use over competitor in field where zipper closures are already used and enable applications that are up to now precluded to zippers by their low resistance and/or water tightness:
- in high performance sectors as aerospace, automotive, underwater engineering, the combined strength and water resistance properties of the zip will enable it use in a wide range of products and applications;
- in architecture, the REFRESH zipper can replace hook and loop connections in tensile structures, a huge market worth 1.3 billion EUROS per year. Both permanent and temporary structures will be built based on this fast and reliable connection method, enabling also the construction of bigger structures;
ZIPLAST plans to sell after two year from the end of the project about 24.000 m of REFRESH zippers, for a total increase in revenue of 1,2 M EUROS.
List of Websites:
http://www.REFRESH-fp7.eu
http://www.spanopoulos-group.com
http://www.ziplast.it
http://www.industrialsedo.com
http://www.safibra.cz
http://www.dappolonia.it/
http://www.aimplas.es
50 million European citizens, 18% of the European population, live in countries affected by water stress problems. The forecasted variations in rainfall pattern trends, due to global climate change, aggravate this already serious situation. According to the EEA, 16 to 44 million additional people will suffer water scarcity in Southern Europe by 2070.
Project Context and Objectives:
The context: water scarcity, an increasingly serious problem
Water scarcity already affects every continent. Around 1.2 billion people, or almost one-fifth of the world´s population, live in areas of physical scarcity, and 500 million people are approaching this situation. An increasing number of regions are chronically short of water. This is both a natural and a human-made phenomenon. There is enough freshwater on the planet for six billion people but it is distributed unevenly and too much of it is wasted, polluted and unsustainably managed. Water scarcity issues severely impact on the successful achievement of most of the United Nations Millenium Development Goals regarding population access to water supply and sanitation.
The acuteness of the problem is recognised at the European Level, as it was stated in the last 6th World Water Forum in Mareseille in March 2012. Climate change is slowly but steadily turning the Mediterranean coastline into a semi-arid region, with hotter and drier summers and more frequent droughts, adversely affecting water availability. Population growth and increasing average consumption due to extensive agriculture and tourism build up the climatic factors, yielding an increase of the areas subject to water stress; Spain, Italy, Greece, Malta, Cyprus and Turkey are among the most affected countries.
Situation is especially severe in Mediterranean coastal areas and islands. Growing urbanisation and tourism demand are leading to over-exploitation of existing aquifers and reservoirs. Sea water intrusion in coastal aquifers due to over-pumping is already a major issue for a large part of Europe´s coastline.
Mediterranean coast and islands is one of the most popular tourist destinations in the world, with locations doubling the resident population in holyday season. The average tourist consumes 300 litres of water per day, double of the average household consumption. More than 3000 small coastal cities and over 400 inhabited islands are logistically isolated from the mainland water reservoirs, thus making fresh water supply harder. Different approaches have been considered in order to assure water supply for these communities.
Desalination is a process that removes dissolved salts from seawater. Desalination plants require high initial investments (around 15-20 million EUROS for a 10.000 m3/desalination plant) and require operation and maintenance costs. It is estimated that desalination water cost range between 0,40-0,60 EUROS per m3 depending on plant production capacity. However desalination plants pose several critical concerns about their high environmental impact regarding brine disposal in the natural medium and their contribution to the increase of CO2 emissions due to high energy consumption.
Everywhere in the world fresh water is considered a public resource. It is assumed that fresh water in its natural state cannot be considered as a good or product subjected to international trade law rules. This is because water is bulky, transferring or storing (by pipeline, artificial canal, bulk shipment, etc.) is quite costly, requiring large infrastructure.
Water pipelines are systems of canals used to transport water. This type of system has high costs of design, construction and maintenance and it is suitable only in case of constant need of very large quantities of water. In the case of water supply to islands development of underwater pipelines are even more expensive due to the need of pumps and related energy. Thus water pipelines require permanent infrastructure, high investment costs and energy consumption. Also high maintenance costs that are not acceptable for small-medium communities and for temporary or seasonal water supply.
Tank vessels are an alternative solution for water supply to coastal areas and islands. There are different types of ships utilized for water transportation. Tankers transport typically around 50.000 m3 of water. New water tankers cost around 30 million EUROS and recently old single hulled oil-tankers (that could not be used anymore for oil transportation) have been converted to water transport. These second-hand tankers cost around 10 million EUROS and in addition to the high initial capital cost, they require high cost of reclamation and deep cleaning of holds. Moreover the transportation of water by very large tankers involves the necessity of very large port facilities and deep draft to accommodate these huge ships and enable the loading and discharging operations. Vessels ´engines consume high polluting fuels in large quantity, around 300 kg/km for a 200.000 tons tanker. As a result water transported by tanker ships is expensive with a final cost that ranges from 8 to 12 EUROS per m3.
Water bags
Because of the limitations described in the previous section, the transportation of bulk fresh water by sea using huge plastic bags has been conceived. The first concept of large bag transportation was contrived by the inventor Barnes Wallis in the 1930´s, but the first practical manifestation was the Dunlop Dracone, invented at Cambridge in 1958 by Sir William Hawthorne. The system concept was revamped in the 1980s and 1990s when research, development and continued adaptation were explored by a few companies around the world, namely Terry Spragg and Nordic Water Supply.
Terry Sprag (US) has focused his efforts on developing the idea of linking multiple bags together in a "train" to greatly increase the total volume moved at one time. The "Spragg Bags" were each approximately 9 m in diameter and 75 m long. Italian company Ziplast was involved in the manufacturing of high resistance zippers for the connection system among the bags. This zipper is not watertight because its function was only to string together the bags in order to allow the transport of bags in series. Spragg produced a couple of bags and conducted some tests on them but eventually the bags failed due to high stresses.
Nordic Water Supply developed its 10.800 m3 bag in 1997. The company tested numerous bags, which reportedly failed due to towing stresses. The Turkish Government was interested in using the system to deliver water from Turkey to the proclaimed Turkish Republic of Northern Cyprus. Within two years at least 7million m3 of water had to be delivered annually at a cost of 2.7 million EUROS per year, with volumes growing over time but the actual transport only amounted to 4 million m3 in four years due to the frequent bag bread, notably in case of adverse marine conditions, so that the Turkish Government discontinued the contract in 2001. Besides the solution of transporting huge bulk water in a single oversize bag has not been successful owing to their hard handling both full and empty. The enormous bags indeed need special facilities during the operations of discharge and storage for the next water trip. The use of big winches in order to rewind the bags for the empty transportation is also an issue because it harms the bag material due to the induced stress.
The Monohakobi Research Centre in Japan has taken over Nordic Water Supply's waterbag technology in 2004, but up to now with scarce results. One demonstration voyage with a scaled-down prototype was organised in 2007, but since then no notable development has been reported.
REFRESH modular flexible containers system
The aim of REFRESH project has been to develop a cost effective and energy-efficient solution for the sea transport of fresh water based on a modular system of interlinked flexible containers towed by a tugboat. REFRESH approach show lower environmental impact with respect to competing fresh water supply technologies such as desalinators, and has a clear cost-effective advantage with respect to alternative tanker ships.
The breakthrough offered by REFRESH system relies on the fact that each single module is kept sufficiently small to be easily managed, but the entire system is large enough to be cost-effective as allows a flexible service adjusting the total payload to the actual needs of the receiver.
The idea to develop sea transport of freshwater using water bags in not entirely new, but the proposed solutions mentioned never encountered total success due to various technical barriers. In previous attempts the design focused on realising the biggest bag achievable in order to maximise the payload. This approach failed due to structural limitations of plastic materials used, poor design due to lack of knowledge about strength loads, extreme bulkiness and difficulty of handling of such large plastic structures.
REFRESH approach has taken advantage of the proven experience of the companies within the project consortium in order to offer the most suitable materials for the manufacture of the flexible containers.
The Spanish company INDUSTRIAL SEDO has a wide experience in the manufacturing of PVC coated fabrics for different applications. PVC coated polyester fabrics are widely used in several applications (tarpaulins, shelters, tents, canopies, liquid flexible tanks, etc.) due to low cost and optimal performance with a good combination of flexibility, toughness, extensibility and high ratio of strength to weight. They offer good chemical and weathering properties.
Within the scope of the project, INDUSTRIAL SEDO has developed reinforcing textiles based on polyester fibres with specific woven architecture in order to withstand the high demanding requirements of tensile and tear strength foreseen for the towed water bag (700 daN/5cm). In addition to this, PVC coated fabrics are able to be welded by means of high frequency method, offering an outstanding welding resistance. This feature enables the manufacture of flexible containers joining different layers of PVC coated fabrics and also joining PVC coated fabrics with tapes of zipper system.
ZIPLAST, from Italy, is a highly specialized company active in design and manufacturing of special fasteners and zippers for industrial worldwide applications. Its production is focused on custom zippers for chemical protection, fumigation, industrial applications, air-water sealing.
The zipper, produced by ZIPLAST, is the key element in REFRESH system. Connecting singles modules while retaining watertightness of the whole system is only possible through the use of a watertight zipper, which has also to be extremely strong to resist the towing load.
The zipper developed within the REFRESH project exhibited a cross-tensional strength of 24 t/m, making it the strongest watertight zipper existing in the world.
The Prague-based company SAFIBRA was founded in 1999 as a private company and has since established itself as a leader in the field of development, production, sales and applications of state of art optical systems and optical fibre sensors.
The strain monitoring system produced by SAFIBRA exploits the Fibre Bragg Grating technology to measure elongations of the fibre in an extremely precise (resolution of tenths of millimetres over one metre of fibre). Data are sent in real time to the tugboat's bridge deck as a reference for the Captain. In the REFRESH test, the sensors confirmed that deformations are well below the breaking strength of fabric even at full speed.
SPANOPOULOS, coordinating company within the Project, is a maritime Enterprise located in the island of Salamis, Greece, and active in a wide range of maritime services in the Mediterranean Sea and other areas in Europe, including vessel construction and maintenance, construction of harbours and marinas, salvage and towage with its fleet of tugboats.
SPANOPOULOS has guided design and prototyping decisions to comply with maritime regulations and ensure máximum operability of the system at sea. The company is looking forward to commercially exploit the REFRESH system for water transportation towards the Greek islands in conjunction with its fleet of tugboats.
The commitment of all the companies in the project consortium lead to the successful integration of all the elements in the REFRESH system and make possible the manufacture of a medium-size prototype in order to test the performance of the materials in real conditions.
As a main outcome of REFRESH project, a medium-size prototype was manufactured with the aim of assessing the feasibility of the proposed design and the performance of the selected materials to withstand the requirements foreseen.
REFRESH prototype consisted in two single modules connected by zippers. The prototype features 4.1 m diameter and 20 m length. Total load capacity was 200 m3. It is expected that large size prototype for commercial scale to be 10 times larger enabling 2000 m3 water load capacity.
Trials were carried out in Crete (Greece) in November 2012. Flexible container modules were deployed and assembled in the harbor by few operators. A crane helped to place the water bag into the sea in order to start the filling operations. Fresh water was pumped into water bag until roughly full capacity was reached. Once filled, REFRESH prototype float in the sea showing no instabilities thanks to floaters fitted to the water bag.
A tugboat with a main engine propulsion of approximately 2.000 HP was used for towing REFRESH water bag. Several trials were performed in order to assess the hydrodynamic performance of the flexible container. As a main outcome the REFRESH water bag was able to withstand the rough towing conditions tested; PVC coated fabric show no break or deformations and no tear or delamination was noticed in the welding lines.
Project Results:
The main exploitable results obtained by the project can be summarised as follows:
- Development of mono- and multi-material coated recyclable fabrics
- Development of a high-strength watertight zip with a resistance to lateral pull above 20 t/m
- Definition of a Fibre optics-based strain monitoring system and its application to a flexible fabric structure
- Development of a waterbag, with the following sub-objectives:
--Design of a modular waterbag overcoming the issues known from previous waterbag attempts;
--Design of a suitable towage connection transferring the towing load to the fabric without causing stress concentration;
--Fabrication of a 20 m long, 4 m diameter waterbag according to the design;
--Full scale tests with a sea voyage transporting a payload of 200 tons of fresh water
--Establishment of operational procedures and verification of their fulfillment.
1.1.3.1 Development of mono- and multi-material coated recyclable fabrics
Coated fabrics find an important place among technical textiles and are one of the most important technological processes in modern industry due the wide range of applications: protective clothing, shelters, covers, liquid containers, etc. The properties of a coated fabric depend on the type of polymer used and its formulation, the nature of textile substrate, and the coating method employed. PVC coated polyester fabrics are widely used due to low cost and optimal performance with a good combination of flexibility, toughness, extensibility and high ratio of strength to weight. In order to enhance recyclability of coated fabrics, laminates of polypropylene fabrics with thermoplastic polyolefins coating and polyester fabrics with thermoplastic polyester elastomers are proposedfor achieving homogeneous structures. In a first approach, state-of-the-art coated fabrics manufactured with polyester fabrics and PVC coating offer good mechanical properties to meet the requirements foreseen for water bags for bulk water sea transport.
PVC coated polyester fabrics are widely used in several applications due to low cost and optimal performance with a good combination of flexibility, toughness, extensibility and high ratio of strength to weight. They offer good chemical and weathering properties.
The industrial manufacturing process is based on a coating method that applies a PVC solution or plastisol onto the polyester fabric. The polymeric material is applied on the substrate and then metered. The coated fabric pass through a drying oven where the solvents are evaporated and the polymeric material forms a solidified and cured layer.
This process is well established at industrial level and allows for efficient production rates. PVC coating on both sides of the polyester fabric can be achieved in a continuous process. PVC coated fabrics are delivered in reels to be used in different applications: tarpaulins, shelters, tents, canopies, liquid flexible tanks, etc.
Recycling of PVC coated polyester fabrics is not an easy or a common since the family of the polymer used in manufacturing the fiber and the coating compound are heterogeneous, hence their physical mixing to regenerate in the form of recyclable goods is not possible even by applying high temperature or pressure.
Coated PVC polyester fabrics are manufactured in standard width and lengths reels. Individual applications demand specific size and shape, depending on the process of manufacturing, so that joining techniques with adhesives, stitching, heat welding, and high frequency welding are employed.
In order to overcome the recyclability issues of PVC coated polyester fabrics and to enhance environmental behavior of reinforced laminates, two different alternative homogeneous laminates have been proposed combining thermoplastics extruded sheets and fibers from the same polymeric material:
- Homogeneous structure of polyolefin based laminate: TPO thermoplastics liners and PP fiber reinforcing fabric.
- Homogeneous structure of polyester based laminate: TEEE thermoplastics liners and polyester fiber reinforcing fabric.
Thermoplastic polyolefin (TPO) coatings are gaining relevance in engineering applications due to their advantage over PVC coated fabrics.
TPO refers to polymer blends consisting of some fraction of polypropylene (PP), polyethylene (PE), block copolymer polypropylene (BCPP), rubber and a reinforcing filler. TPOs do not contain plasticizers, therefore the problem of plasticizer loss associated with some plasticized polymers (as PVC) is eliminated.
TPO are basically inert towards chemical and microorganism attack. The finished products have good resistance towards oxygen and ozone and are flexible at very low temperature (-60ºC). The products are odorless and do not give out toxic gases on burning. TPOs liners are lighter that PVC or PU since polyolefins are lower in density, this feature enhances buoyancy of flexible tanks for sea transport.
In order to achieve multilayer homogeneous laminates combining fibres and polymeric coating of similar and compatible materials, a search task has been done for selecting appropriate TPO grades and PP fibre fabric to manufacture laminates with more favourable environmental characteristics and fully recyclability after use and through disposal since the coating and the reinforcing fabric are homogeneous polymers hence are melt recyclable, which is not possible in the case of PVC coated polyester fabrics.
TPO resin flexible polypropylene Hifax CA 10 A has been chosen as polymeric coating. This material is typically used in geomembranes and liners for waste water treatment reservoirs, floating covers, aquaculture ponds, storage reservoirs, etc. According to technical data provided by resin manufacturer, Hifax CA 10 A exhibit excellent resistance to puncture, mechanical toughness and high tear strength. Chemical resistance is also a main advantage.
Polypropylene high toughness fiber fabric Murafil provided by INDUSTRIAS MURTRA has been chosen due to commercial availability and good performance regarding low specific density, good thermal resistance, low water sorption, high abrasion resistance and good weatherability.
Main drawback of polyolefin sheets and fibers rely on low surface tension, offering poor adhesion properties. This fact will be addressed in the trials for manufacturing reinforced laminates selecting appropriate adhesion promoter for enhancing adhesion between sheets and fabrics.
Thermoplastic polymers are processed by extrusion melting the material in a heated barrel while a rotating screw transport the solid granulates. This melt is extruded through a flat die vertically downward into a nip of the coating roll and over the fabric. This method, known as extrusion coating, differs from the fluid platisol coating method used for PVC coating fabrics.
Thermoplastic polyester elastomers are block copolymers consisting of a hard (crystalline) segment of polybutylene terephtalate and a soft (amorphous) segment based on long-chain polyether glycols. They are also referred as thermoplastic elastomer ether ester (TEEE). Properties are determined by the ratio of hard to soft segments and by the make-up of the segments.
This type of polymeric materials combines many of the most desirable characteristics of high-performance elastomers and flexible plastics. It features: exceptional toughness and resilience, high resistance to creep, impact, tear and flex fatigue; flexibility at low temperatures and good retention of properties at elevated temperatures (up to 165ºC). In addition, it resists many industrial chemicals, oils and solvents.
The excellent properties of TEEE qualify it for a number of demanding applications where mechanical strength and durability are required in a flexible component. Main drawback relies on high price of this type of resins which limits its use for high value products, mainly in the automotive industry, electronic appliances and sporting goods.
In order to achieve multilayer homogeneous laminates combining fibers and polimeric coating of similar and compatible materials, a search task has been done for selecting appropriate polyester thermoplastic elastomer grades and poliester fibre fabric to manufacture laminates with more favourable environmental characteristics and fully recyclability after use and through disposal since the coating and the reinforcing fabric are homogeneous polymers hence are melt recyclable, which is not possible in the case of PVC coated polyester fabrics.
TEEE resin Hytrel 4056 has been chosen as polymeric coating. This material is typically used in hoses, cable coatings, sport apparel and other industrial applications. According to technical data provided by resin manufacturer, Hytrel 4056 is a plasticizer free compound that exhibits excellent flexibility, high resilience and excellent flex crack resistance.
Polyester fiber fabric provided by INDUSTRIAL SEDO has been chosen due to commercial availability and good performance regarding high thermal resistance, low water sorption, high abrasion resistance and high mechanical strength.
Thermoplastic polymers are processed by extrusion melting the material in a heated barrel while a rotating screw transport the solid granulates. This melt is extruded through a flat die vertically downward into a nip of the coating roll and over the fabric. This method, known as extrusion coating, differs from the fluid platisol coating method used for PVC coating fabrics.
A pilot production of the new TPO and TPEE laminate was started at AIMPLAS. In order to simulate the extrusion coating process at pilot plant level and obtain appropriate samples for further mechanical characterization, a two-stage process was carried out at AIMPLAS facilities:
- First stage consisted in thermoplastic sheet extrusion.
- Second stage consisted in coating of reinforcing fabric using a manual method in hot platen press.
1.1.3.2 Development of a high-strength watertight zip with a resistance to lateral pull above 20 t/m
A zip fastener is a commonly used device to temporarily join together two strips of textile. It basically consists of two half-chains of elements, or teeth, attached to two strips or pieces of fabric. When the teeth half-chains are forced to interlock by means of a cursor, they join together the two fabrics.
Zips are used in all kinds of garments as an alternative to buttons; in the last decades, the availability of high performing materials for teeth opened up new market segments for zips as alternatives to conventional means of fixing or adjoining textile or net structures.
An example of this is the use of high strength zips to assemble the large nets used in aquaculture. Those zips are able to withstand tensional loads up to the order of 10 tons per linear meter. Passage of water through the zip teeth is not an issue in this case, as both sides of it are immersed in sea water.
In other applications, such as scuba diving suits, water-sealing zippers have been conceived, which are able to separate a dry side on the inside from an outer wet side. These zips usually achieve the sealing effect by adding a tiny gum strip on tooth profile, so that when teeth are joined together, the gum strips effectively form a gasket. This configuration only holds when no considerable tearing force acts on the zip, as any relative displacement of the half-chains would break the seal.
One of the basic innovations of the REFRESH zipper approach is decoupling of the tensional strength function from the water tightness function, achieving both functions through the use of independent (yet coupled) elements.
All the load is taken by interlocking teeth, which feature a U-shaped profile. Each of the teeth has two side prongs interlocking in between the "bellies" of adjacent U-shaped teeth, thus obtaining mutual engagement.
This coplanar configuration, symmetrical with respect to the tensional force plane, was chosen so that all tensile loads are distributed on the tangent plane; this avoids out-of-plane normal reactions possibly leading to unlocking of the zip.
The weakest point of the chain is located at the end of the straight part of the tooth, at the root of the curved part. This is where the load from side prongs of the other half-chain of teeth is applied, moreover here a geometrical discontinuity is observed (passing from straight to curved geometry).
Finite Elements simulations were carried out on the chain model to assess its resistance to lateral pull: the first partial results from simulations confirm this mode of failure as the preferential one.
The first prototype of the zip was made according to this design: teeth chains were made in polyoxymethylene (POM) loaded with glass fibres for higher resistance. The chain was formed by injection moulding, which required design and fabrication of a dedicated mould.
The pre-prototype chains were sewn to a Vectran-based side tape. Vectran was used on weft, while warp, not taking significant loads, was made in polyethylene.
A tear strength test was performed on the zip, obtaining breakage at 800 kg/5 cm, which corresponds to 16 t/m.
The test was performed at ZIPLAST facilities by fixing one side of the zip pre-prototype in a vice, while subjecting the other to a lateral pull increasing up to 800 kg over a length of 5 cm. This is a standard test used to evaluate the tear resistance of textiles and zip closures.
This first prototype featured an asymmetric section, i.e. the sealing membrane was set on a different plane with respect to the teeth interlocking plane. While this configuration is suitable from the mechanical point of view, there was concern that it could facilitate decoupling of the teeth during use. The shape of the tooth was then changed to accommodate the sealing membrane in half position. The second zip prototype is shown below.
The second prototype exhibited a breaking strength exceeding 24 t/m. after the successful outcome of this test, mass production for the full scale prototype begun. 24 m of zip were included in the prototype.
Water tightness tests were performed by closing a pressure vessel with a sheet of fabric sealed by a zip sample. Water inside the container was then put under increasing pressure until witnessing the formation of bubbles. At a pressure of 0.6 bars, bubbles started forming on the welding line between zip tape and fabric, but not between the teeth.
The zip fastener developed by the REFRESH project was able to resist to a lateral pull of 24 t /m, making it the strongest watertight zip fastener existing to date.
1.1.3.3 Definition of a fibre optics-based strain monitoring system and its application to a flexible fabric structure
The selected sensing technology is based on the use of Fibre Optics. Fibre optic sensors act on the principle of transmitting a light signal through the fibre and measuring the status of the returning or transmitted signal. The change in signal properties is then translated into appropriate quantities that allow the measurement of a wide range of mechanical, physical, and chemical quantities. Fibre Bragg Grating (FBG) is a short segment of an optical fibre with a periodically varying refractive index in the core of the fibre. Such segments then act as a mirror reflecting only a specific wavelength of light propagating through the fibre and which is incident on this segment. The rest of the spectrum is transmitted.
A Bragg Grating is a local modification to the internal structure of the fibre that causes it to reflect light of essentially one wavelength while allowing all other wavelengths to pass. The perturbation of the grating by the measure and causes an extension of the fibre and, with that, the increased separation of the grating elements and a change in the characteristic wavelength observed. The wavelength reflected varies, depending on the temperature or strain to which the fibre in the region of the grating is subjected. This wavelength change is detected by means of optical spectroscopy and is interpreted as a change of corresponding physical quantity measured.
Bragg gratings are powerful tools for the sensor designer, as they are versatile, they can be multiplexed to create a series of quasi-distributed sensors along a fibre network
The partner SAFIBRA has selected as suitable optical monitoring system for the REFRESH system the use FBG glass fibre. The choice is supported by the following characteristics, which generally match very well with the system requirements:
- EMI resistent, dielectrical, passive fibre installation;
- already in use in other applications with proved reliability, robustness and resistance to harsh environment, long-life and maintenance-free;
- ability to measure linearly without hysteresis (based on elasticity of glass fibres);
- ability to measure elongation of the glass fibre up to 5%;
- static or dynamic measurements are possible;
- high precision: submicron resolution for 1m sensor resolution 1,0000001 (at 7 Hz sampling rate)
- high sampling rate for dynamic measurements
The first prototype of the REFRESH fibre monitoring system consisted essentially in a "naked" optical fibre enclosed in a fibreglass tube. This setup worked well in the laboratory, demonstrating the viability of the technology, but proved to be too fragile in the first trial at sea with a small waterbag, carried out at SPAN premises at Salamina, Greece.
The anchoring points were covered with a patch of fabric, glued to the surface with the epoxy glue. A supplementary layer of tape was added to seal the perimeter; however the tape did not perform well in water. Epoxy held well in water; however after the test it was easy to peel off the patches to expose again the fibre, perhaps due to a too thick layer of epoxy used. This could become dangerous in case of accidental sliding contact of patch edges.
The electronic box is waterproof, thus for this test it was just anchored to the surface of the bag with tape. It proved to be a good solution which survived well the test. When it was removed after the test, no water was found inside the box, apart some small droplets on the cover, despite it being completely submerged for long time.
The prototype was lifted down to the sea and filled.
The optical fibre broke when lowering the prototype in the sea due to excess bending of the container. Even if the operation was performed as carefully as possible, the weight of the bag caused sharp bending of the fabric between the two lifting points. The fibre was damaged during lifting down, before the prototype actually entered the water. Since it is not possible to avoid bending (moreover it is not realistic to require the crew to perform too precise or careful handling of such equipment), a re-thinking of the design was necessary to protect the fibre from excess bending.
After this first trial, it was decided to fabricate a new batch of sensors with an additional layer of protection. The fibre was enclosed in two concentric tubes, a spiralled metallic one and an external rubber one.
Also the anchoring mechanism was changed: in the first version was realised by means of epoxy glue, but it proved to be impractical in the event of having to remove it, for maintenance or for the storage of the system. The new version of the anchoring system was realised by means of bolts and screws: a faster, firmer and much more elegant connection system.
The monitoring system prototype was tested at Cambrils, Spain. It was composed by a 70 centimeters long sensor and an electronics box. The fiber and box were covered by plastic pockets prepared by SEDO.
The small waterbag with the fibre system installed was towed by a boat. Signals recorded by the monitoring system during towage are reported in the graph below.
The fibre optics system performed well in this trial, so the same scheme was kept for the final prototype.
1.1.3.4 Design of a modular waterbag overcoming the issues known from previous waterbag attempts (confidential)
The REFRESH concept consists of an evolution of the so-called "waterbag" technology transporting bulk quantities of water across the sea by means of large flexible barges towed by tugboats, examples of which exist since the 1980s. Such systems can be used to transfer water from water-rich to water-poor areas even at long distance; however, despite the research efforts, none of the proposed waterbag concepts has up to now reached a commercial product phase.
Two main categories of waterbags had been proposed in the past, either being based on huge monolithic containers or on trains of smaller containers, each one being sealed on itself, connected via ropes or fabric sleeves. Each of the conventional designs despite being technically sound has intrinsic drawbacks that have prevented all past waterbag projects from reaching commercial success.
The key innovation introduced by REFRESH is the use of open modular containers.
This new structure, enabled by the use of a unique watertight high-strength zip closure (one of the most notable results of the research project), has improved handling, reliability and time-efficiency by orders of magnitude with respect to previous waterbag attempts.
The REFRESH modular concept
Each module is open on itself, it is closed by the adjoining one
A train of modules is formed and each compartment is loaded
After discharge, the train of modules is unzipped
Handling and retrieval is performed at the level of single modules
The "open modules" concept has four fundamental advantages over monolithic designs and trains of separate modules, exploiting the strong points and avoiding the weak points of both approaches:
1. Unlike monolithic designs, it allows compartmentalisation, so that if one module is damaged only a fraction of the payload is lost and the rest remains intact; moreover, when not in operation the system can be managed at the single module level, enabling much easier handling and minimising logistic problems;
2. When assembled, the full system behaves "as one", avoiding snaking and excess bending problems that may arise when towing trains of separate containers linked by ropes or fabric sleeves;
3. Upon discharge, the small fraction of the payload that cannot be retrieved by pumps (a fraction that may weigh several tons) can flow through the open side. Sealed modules (either in a "monolithic" or in a "train" configuration) wouldn't allow this and the weight of the remnant water would require large cranes to lift the system off water. In comparison, a REFRESH module can be lifted using the small crane present as standard equipment on every tugboat;
4. The open side allows easy access to the interior of the modules for cleaning and sanitising, a huge issue in sealed systems.
1.1.3.5 Design of a suitable towage connection transferring the towing load to the fabric without causing stress concentration
One of the main issues related with the towage connection system was the effective distribution of stresses.
As a general rule, moreover valid when dealing with flexible structures, concentration of stresses should be avoided. A further problem is potentially represented by friction between the textiles and the metallic parts of the connection. One of the earliest ideas to overcome this issue was to devise a non-metallic (e.g. plastic) connection; this idea was soon discarded because of the problems posed by non-metallic elements in the maritime environment in terms of performance, corrosion and generally lifetime.
Three early conceptual designs of the towage connection, proposed by DAPP to the project partners, are reported in the following:
A flat metallic flange is used to restrain the bow part. A bundle of secondary towing cables is departing from the primary one; they are fixed to the flange, either in its front face or on the side circumference. Having multiple circumferentially-disposed fixing points, instead of a single one in the middle, is helpful in avoiding spinning.
There are two ways in which the fabric can be adjusted to the flange: either it is cut to the precise shape of the bow leaving a free circular edge to be clamped between the two faces of the flange, or it is folded and clamped.
The fabric is wrapped around a transversal bar and then clamped or fixed by a further strap. This design option would give the bow section of the prototype a flattened shape, which could be beneficial for stability; however, the folded fabric would create preferential force propagation lines, which could lead to high stress concentration. With this option, two cables would depart from the primary towing cable and would be fixed to the sides of the bar.
In the third option, the reinforcing belts running longitudinally on the prototype are directly connected to the secondary towing cables. With this method, the towing load is directly transferred to the belts: in principle the fabric does not sustain any load. In the real case, a fraction of load is transferred to it by the seams linking belts and fabric, but only as a second order effect.
Since the reinforcing belts were in the end excluded from the final design of the container, this design option was discarded. The chosen option for detailed design and prototyping was number 1, featuring a metallic flange.
Towage trials with the small prototype showed evidence of the effect of a completely submerged conical bow, tending to cause immersion of the prototype when crossing the ship's wake.
It was argued that the conical bow, featuring an equal upwards and downwards water flow when moving in still water, is strongly affected by any turbulence.
In particular, when the conical bow impinges on a water front which is moving upwards (e.g. when entering the wake), the upward water flow over the cone pushes the cone downwards; the opposite happens when impinging over a water front which is moving downwards (e.g. exiting the wake).
This fact led the project group to devise a modification in the design of the bow, proposing a lifted bow.
DAPP performed numerical simulations on both front module designs to assess their behaviour under towage, highlighting the best performance of the "lifted nose" solution.
Two designs of the towage connection were proposed by DAPP. In the first version, the clamp is realised in the perpendicular plane with respect to towing, requiring that the fabric be folded over the inner plate.
The second and final version of the towing connection flange counteracts the potential risks tied to folding the fabric over the metallic flange. The purpose of this flange design is to transfer clamping from the perpendicular to the parallel plane with respect to the towing line; this in turn avoids the need to fold the fabric over the metallic part.
1.1.3.6 Fabrication of a 20 m long, 4 m diameter waterbag according to the design
The prototype has been designed with modular elements, joined by zippers.
The conceptual design originally foresaw the possibility of including reinforcing belts running along the length of the prototype.
These items would prove particularly helpful to relieve stress from the textile by taking the direct towing load, but have the drawback of creating preferential loading lines: if the loading line propagates up to the vicinity of the zipper, it could cause load concentration on a small section of the zipper, potentially leading to unzipping. These considerations were taken into account at the final design stage: the outcome of the tensile strength tests on textiles proved that it will be possible for them to sustain the towing load, making it possible to avoid the use of reinforcing belts; in the final design, the belts were not included.
1.1.3.7 Full scale tests with a sea voyage transporting a payload of 200 tons of fresh water
The final outcome of the REFRESH project was the development and successful testing of a 20 m long, 4 m wide prototype (around 200 m3 of payload) featuring the "open module" scheme. The technological feasibility of the concept was proven with the successful delivery of a 200 m3 freshwater payload with a 16 nautical miles sea voyage in the gulf of Souda, Crete, hosting one of the operational bases of Spanopoulos Group's fleet of tugboats.
The bay of Souda is protected from northern winds by the Akrotiri peninsula; the port is quite busy in the summer season but it does not feature a lot of traffic in other periods; it has plenty of space available on the docks and is equipped with 2 inch hoses for filling freshwater in boat tanks: all these factors contributed to make it an ideal location for the tests.
The route established by SPAN's Captain foresaw a length of 8 nautical miles from the harbour of Souda to the mouth of the bay,to be covered twice (back and forth) for a total of 16 nautical miles.
The first part of the voyage was used by the tugboat crew to gain confidence with the prototype. Speed was kept at a limited pace (2-3 knots) and the towing line was limited to 30 m until exiting the port area.
In order to acquire experience with the behaviour of the prototype under manoeuvring, the Captain made a series of turns, each between 30 and 45 degrees.
In this first phase, it was observed that the prototype tended to snake under its own inertia, not being able to follow the tugboat movement correctly. Even when the tugboat followed a straight line (always keeping a moderate speed), the snaking movement continued.
The towing line was then elongated up to 100 m and the behaviour of the prototype changed completely. No snaking effect was observed at this time, making it possible to increase the speed of the tugboat towards cruise speed.
The prototype continued to behave nicely and the elongation reported by the sensors continued to be well below the ultimate breaking strength of the material: this prompted the consortium to ask the crew to continue acceleration above the foreseen speed. The speed was then brought to 6 knots, without noticing any change in the behaviour of the prototype.
The Captain stopped acceleration before reaching the 7 knots mark, which is the maximum limit conventionally respected for boat towage.
The ramp from nearly zero speed to 6 knots was performed in less than 15 minutes. This acceleration was much faster than initially foreseen when designing the system.
When reaching the mouth of the bay, the tugboat considerably decreased speed until stopping. The prototype decelerated smoothly and stopped in a short space (less than the length of the towing line). The tugboat made a 180° turn at low speed and the prototype followed, finding alignment with the new direction in a short time (around two minutes).
The tugboat then ramped up speed to 6 knots for the return leg. Again, none of the snaking behaviour experienced with the short towing line was observed.
When reaching the harbour area, the tugboat stopped and the towing line was shortened to less than 5 m. The tugboat approached the dock at low speed, allowing the prototype in tow to come alongside the dock in a smooth manner
1.1.3.8 Establishment of operational procedures and verification of their fulfillment
A handbook for operation of the REFRESH waterbag system was prepared by DAPP and SPAN. This document is a guidance for the use of the system, providing directions to the tugboat crew for transporting, assembling, deploying, using and retrieving the system.
The module assembling procedure can be carried out in two different ways: relatively short waterbags can be assembled in one single step directly on the dock, then lowered in the sea; this system is unpractical for larger waterbags: in this case, the modules are joined continuously as the bag is lowered.
Potential Impact:
1.1.4.1 Wider impact and correspondence to EU policies
Water scarcity is a global problem and is not confined to "poor" nations. Considering Europe alone, REFRESH represents a cost effective and flexible technology for supplying fresh-water to coastal small cities and island with less than 300.000 inhabitants where live about 45 million of European citizens . 65% of these communities, that double in size during summer with tourist presences , are affected by growing water scarcity due to several factors as climate change, growing urbanisation of coasts, tourism, sea water intrusion in aquifers.
Water scarcity is also a major concern in the Middle East, where most countries have only less than 500m3/capita/year of water available. The annual volume of actual renewable water resources per capita is 261m3 in Israel, approximately 90m3 in Palestine, and 164m3 in Jordan, while water-rich countries such as the United States have more than 10,000m3.
One of biggest challenge in the Arabic Gulf region is water, which may be everywhere in the Gulf but is undrinkable without desalination. Desalination plants produce emissions of carbon dioxide that have helped give Dubai and the other United Arab Emirates one of the world's largest carbon footprints. They also generated enormous amounts of heated sludge which is regrettably pumped back into the sea.
For these communities REFRESH will represent the most effective solution for fresh-water supply service because traditional technologies as water pipelines, desalinisation plants and large water vessels are not a feasible solutions due to financial, environmental and technical barriers.
REFRESH would enable the low cost transport of large amounts of fresh water from regions where it was abundant to regions where it was scarce. Some potential water transport routes are given in the table below. Clean fresh water is vital for agriculture, industry, and personal use. A consumption rate on the order of 600 cubic meters per person per year of fresh water is needed for an adequate living standard. The continuing depletion of aquifers and the growing world population will require increased sources of fresh water in the future. By 2050 AD, world population is expected to grow to 9 billion people, with an annual fresh water deficit of 2x1012 cubic meters (2000 cubic kilometers) per year. Much of this deficit will be in China, the Mid-East, and Africa. REFRESH can help to mitigate this water deficit.
The results of REFRESH encompass different fields and applications, each leading to a substantial impact on the European industrial scenario. These impacts are both direct, due to the use of components developed within the project, and indirect, exploiting REFRESH technological solutions in different fields:
- Reduce environmental cost of water industry: REFRESH water supply system, consuming low energy and with practically no environmental impact due the use of solar energy and recyclable materials is an important improvement on developing a low environmental impact European industry, fully supporting the competitiveness of water sector on the international market.
- Support the Tourism Industry, one of the leading sectors in Europe, especially in Mediterranean seaside locations with an estimate of 235 million tourists per year and an occupation of 4 million people, will benefit from increased water availability without environmental drawbacks thanks to the application of the REFRESH water supply paradigm, increasing the touristic appeal and marketability of European coasts and helping overcome the competition from extra European destinations;
- Support the European Textile sector, that in the latest years suffered by Far Est competition on low value products. The Textile sector will greatly benefit by the project innovative products as high recyclable strength multilayer laminates combined with high performance zippers in the growing sector of tensile architectural structures, overcoming the limitations caused by current hook and loop joints and allowing a substantial expansion of the textile architecture market, currently estimated at 13 billion EUROS;
- Increase safety of European workers and citizens because they will benefit by the development of the flexible fibre optics monitoring systems that could dramatically increase the possibility to continuous in-service monitoring of critical structures.
In particular, we envisage the REFRESH innovation will have an impact on different applications:
- Fresh water for agricultural and industrial use: this is clearly the area where REFRESH will have a direct impact. We will target both seasonal needs (i.e. the case of a small isle where in Summer the tourist presence is high and the request for fresh water is far higher than the quantity required by the local inhabitants) as well as the case of a continuous delivery of fresh water all year round, as is the case of water for industrial use.
- Fresh water for areas of crisis: In case of disasters such as earthquakes, tsunamis, and others happening in coastal regions the first and most urgent need after rescue operations are finished is usually clean water. The system being modular offers the possibility to assemble the train of bags which would fit best the particular need and disaster scenario. The modular bags and they can be made any size can be pre-positioned throughout the world, folded and stored. In a disaster, they can be immediately filled with freshwater from any safe source, such as surviving municipal systems, rivers etc. and towed through the oceans to places of need or they can be driven or flown, empty, to the site of a disaster and filled locally
- Real Estate: even though the profits to be generated from the implementation of a REFRESH waterbag transport system are significant, the profits to be generated from the increase in the value of the land to which the water is to be delivered will be even more significant. The introduction of a viable and reliable water supply will significantly increase the value of real estate where ever waterbag water is delivered.
In the context of water supply, sustainability means developing water sources that are cost-effective and that can be maintained in the long term without compromising important social and environmental parameters. Actual methodologies for fresh water supply are not fully sustainable:
- Desalination is not an ideal solution as there are many potential environmental, social and economic risks associated with seawater desalination. Desalination plants pose several critical concerns about their high environmental impact due to the operation of desalination stations, they being related mainly to brine disposal in the natural medium. A major constraint to this system is the energy consumption per m3 produced (between 0.3-0.5 million EUROS per 10.000 m3/day desalination plant)Error! Bookmark not defined. That account for 30 to 60 percent of the operational costs. In summary desalination contribute in the increase of CO2 emissions: one cubic meter of desalinated water consuming 5.3 kWh of electricity and emits nearly 5 kg of CO2.
- Water pipelines require permanent infrastructure, high investment costs, high energy consumption, difficult maintenance that are not acceptable for small-medium communities and for temporary water supply. Building an underwater pipeline results in an irreparable damage of sea bed along the whole length of the pipeline.
- Tank vessel consume high polluting fuels in large quantity, around 300 kilos/km for a 200.000 tons tanker.
REFRESH, on the other hand, will have a low impact on the environment, thanks to the null infrastructure requirements and low fuel consumption of the tugboat (around 20 times less than a tanker ship). The modularity and readiness of use of REFRESH allows a full compatibility with all existing tugboat classes, hence not requiring the building of new ships and allowing a more effective use of the existing naval resources. Compared to actual water barges, towing using tugboat is more energy efficient when it is considered that in the return way both are unloaded; moreover, recent progresses on tugboat design demonstrate that it is possible to further cut emission by 20 to 30 per cent and allow for fuel saving in the range of 35 per cent.
A preliminary LCA performed during the original REFRESH project yielded a lifecycle environmental fingerprint two orders of magnitude lower than a tanker barge of comparable size.
Assuring that all its citizens have access to safe, good quality water according to their needs is a major concern for the European Union. The first legislative actions to harmonise and regulate the water supply framework throughout Europe dates back to the very origins of the Union, in the 1970s, with the 1975 Surface Water Directive, its 1979 Daughter Directive on Sampling and Analysis, the 1977 Decision on Exchange of Information on Surface Waters and finally the Drinking Water Directive , issued in 1980 and revised in 1998; the issue of water availability is one of the hot topics of European policy action today, as demonstrated by the strong message conveyed by the President of the Parliamentary Assembly of the Council of Europe (PACE), Mr. Lluís Maria de Puig, at the Fifth World Water Forum, held in Istanbul in March 2009. Mr. de Puig stated that "access to water should be recognised as a fundamental human right. A rights-based approach to water would be a very important means for civil society to hold their governments accountable for ensuring access to an adequate quantity of good quality water as well as sanitation".
In view of the forum, the European Parliament issued a resolution stating that "water is a shared resource of mankind" and "access to drinking water should constitute a fundamental and universal right". The same resolution calls the Parliament and Commission to make an additional effort to guarantee access to water for the most deprived populations by 2015.
The major challenge provided by water scarcity and droughts has been recognised in a communication from the European Commission in which it is estimated that at least 11% of Europe's population and 17% of its territory have been affected by water scarcity to date, with the cost of droughts in Europe over the past thirty years amounting to 100 billion EUROS.
1.1.4.2 Foreseen economic impact for the SME participants
The price of fresh-water supply with current tanker ship services ranges from 5 to 8 EUROS per m3 in Greek islands and around 7 EUROS per m3 in Italy. Based on these values, a detailed estimation of REFRESH costs and final water price has been performed by SPAN on the basis of its experience with water supply by tanker barge and tug boat operation and considering a trip distance of 60 km.
Tugboat maximum consumption is around 10 l/km of fuel at full towage and 4 l/km when no-towing, which gives a total fuel expense of 1000 EUROS with current fuel prices. The daily personnel cost of a 3 men crew accounts approximately for other 1000 EUROS. The cost of freshwater at the source amounts to 0.30 EUROS per m3; an estimation of the cost of electricity required to operate the pumps for load and unload of water is around 0.10 EUROS per m3. The total costs of operating REFRESH for supply on a 60 km route amount thus to 4000 EUROS.
This commercial scenario allows fixing the final price of water at 2 EUROS per m3, with an important reduction compare to actual prices in order to gain quickly important market share, yielding to a profit per voyage of 6000 EUROS.
REFRESH will be also competitive with seawater desalination, which is the directly competing technology, whose final water price is around 4 EUROS per m3. Brackish water desalination can yield lower prices, around 1 EUROS per m3, but the environmental and logistic concerns and high capital costs make it inconvenient for a small coastal community. Moreover, an abundant brackish water source is not easily found in Mediterranean islands.
On the basis of the considerations reported above as well as considering the collateral markets, the overall foreseen economic impact for the SME participants of REFRESH can be summarised as follows:
SPAN, the end user within the project, will highly benefit from the project outcome. Its activities already include the supply of fresh water in small to medium quantities to military ships, which is currently performed using a self propelled water barge. REFRESH gives them the opportunity to enlarge this business and extending it to different - and larger - end users such as island communities, both for household and agricultural consumption, touristic locations and emergency supply to drought-stricken coastlines. Its locations, indicated by the star symbol in the map on the right, in Salamis (island in the Saronic gulf, in front of Athens) and in Crete represent a strategic crossroad enabling easy reach of all Saronic, Cyclades and Southern Aegean islands, which have the biggest market potential in south-eastern Mediterranean due to their geographic position and the high demand in summer months caused by massive tourism: the total potential market for fresh water supply to the Greek islands is estimated at more than 100 million EUROS per year. Considering a conservative market penetration of 2% in three years after project completion, SPAN will increase its annual turnover by 2 M EUROS.
SAFIBRA will exploit the development of the stress/strain monitoring system for application to flexible structures and marine structures a growing market segment that until now has been generally addressed by standard sensing technologies were application of fibre optics technologies is so far limited. The new miniaturised sensing device with Wi-Fi transmission capabilities developed by SAFIBRA within REFRESH represents a significant step forward with respect to the state of the art of fibre optic technologies, and open new markets for SAFIBRA in addition to the REFRESH application. Laboratory trials and sea trials of the REFRESH system in Chania, Crete, demonstrated that the signal can be reliable transmitted for distances up to 500 metres, which was significantly far better than the 100 metres limit targeted in this application.
Several thousands of waterbags would be required to cover a small amount of the total request of freshwater in the selected routes. For instance, considering a 10.000 m3 REFRESH configuration, the delivery of about 400 waterbags per year will be required to cover just the 5% of the total request of freshwater needed by Cyprus. Considering that each waterbag will have at least one monitoring unit provided by SAFIBRA, and a cost for each single unit of the order of 5.000 Euros, the expectation for this company is to increase its turnover of about 2,0 M EUROS per year.
SEDO will be in charge of the production of the material for the manufacture of the waterbag itself, with the required mechanical properties and stringent requirements in terms of resistance to the harsh marine conditions, UV rays and, at the same time, compliant for transportation of water for human consumption.
Apart from main water tankers use, secondary applications for this new product include:
- large flexible liquid container for food and beverages, but also for chemical products, fuel, water for irrigation or fireguard reservoirs;
- textile components for all kinds of marine applications, for instance aquaculture, thanks to the high resistance to saltwater corrosion and environmental compatibility of the material;
- tensile structures and the like in technical textile architecture, thanks to the high resistance to stress and UV rays.
Considering the targeted production of 400 waterbags/year as described above, the total quantity of material needed amounts to about 500.000 square meters of coated fabric. Considering a unit price for square metres of material of about 1,7 EUROS per sqm, the total increase in revenue for SEDO would sum up to about of 850.000 k EUROS per year.
ZIPLAST will enlarge its business opportunities by exploiting the unique watertight high strength zipper, having unparalleled performance by competitors. Zip closures are the fastest and easiest way of connecting adjoining textile parts: the enhanced properties of the REFRESH zipper will boost its use over competitor in field where zipper closures are already used and enable applications that are up to now precluded to zippers by their low resistance and/or water tightness:
- in high performance sectors as aerospace, automotive, underwater engineering, the combined strength and water resistance properties of the zip will enable it use in a wide range of products and applications;
- in architecture, the REFRESH zipper can replace hook and loop connections in tensile structures, a huge market worth 1.3 billion EUROS per year. Both permanent and temporary structures will be built based on this fast and reliable connection method, enabling also the construction of bigger structures;
ZIPLAST plans to sell after two year from the end of the project about 24.000 m of REFRESH zippers, for a total increase in revenue of 1,2 M EUROS.
List of Websites:
http://www.REFRESH-fp7.eu
http://www.spanopoulos-group.com
http://www.ziplast.it
http://www.industrialsedo.com
http://www.safibra.cz
http://www.dappolonia.it/
http://www.aimplas.es