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Development of a tri-generation solar heating and COOLing System including the Use of the heat extracted from the adsorptioN chiller re-cooling circuit

Final Report Summary - COOLSUN (Development of a tri-generation solar heating and COOLing System including the Use of the heat extracted from the adsorptioN chiller re-cooling circuit)


Executive Summary:

The project challenge is to combine sanitary water heating, winter heat supply and summer cooling by one single solar thermal system, capable of providing the full thermal autonomy (except for cooking) to buildings at acceptable cost. This looks possible at least under the Mediterranean climate starting from the recently demonstrated EnerSun system. It employs vacuum solar collectors with direct circulation of a dedicated thermo-fluid heated up to 150°C within safe conditions in normal operation, a set of thermal storage tanks, and a single intelligent control system which satisfies the energy demand in real time either directly from the collectors or from thermal storage tanks. The project aims at making one more significant technological innovation step towards the thermal energy autonomy by including a state-of-the-art adsorption chiller.

Thus, the overall project ambition is to design, develop, build and validate tri-generation solar heating and cooling system including the valorisation of the heat extracted from the adsorption chiller re-cooling circuit, capable of achieving the thermal autonomy of buildings under a Mediterranean climate and a solar fraction above 50% in central Europe by using a heat transfer fluid having a boiling point above 170°C.

Project Context and Objectives:

Thermally driven solar cooling systems for building space have been developed for more than 15 years and tested in about 600 pilot applications throughout the World (87% in Europe). They use sorption or desiccation chillers to convert solar heat into chilled water, from which space cooling is obtained. On the one hand, solar cooling systems are still very expensive compared to classical electrically driven compression cooling systems, which is a clear barrier to massive investment decisions favourable to this renewable energy in the building sector. On the other hand, these systems raise a great interest because there is an obvious correlation between the solar irradiation in warm seasons and the cooling demand.

Absorption and adsorption chillers for cooling applications have been used for many years in the high power range. But in the low power range (< 30 kWcold), they have been commercialized only recently.

The IEA-SHC task 38 has made recently a rather exhaustive analysis of the existing low power solar cooling installations on the international scene8.

In Europe, the state-of-the-art in solar cooling is complemented by the SOLAIR initiative (http://www.solair-project.eu/) which gives an overview of the main projects and results obtained at European level in this field. Especially, the projects SolarCombi+ (http://www.solarcombiplus.eu) and HighCombi (http://www.highcombi.eu) are exploring the proposed triple combination of thermal uses, whereas the Medisco project (http://www.medisco.org/) has demonstrated the benefits of using a high temperature source to produce cold more efficiently.

The recently terminated European project DEARSUN has demonstrated the potential of a solar heating system, developed on the basis of the patent from Baldo & Chassin (i.e. using pure glycol9 heated up to 150°C with a boiling point above 170°C at ambient pressure, thermal storage tanks and a single control system), to achieve high solar fractions without the cooling function (fractional energy saving, fsav, of 84% for a 120 mÇ standard family house in Nice).

The European Solar Thermal Technology Platform (ESTTP) defines in its Strategic Research Agenda thermal storage and solar cooling as key topics for the years ahead: the solution proposed by COOLSUN is coherent with such perspectives.

At present, the technical solutions available to achieve the thermal autonomy target can hardly pay back within the lifetime of the system. Therefore, the project challenge is to combine sanitary water heating, winter heat supply and summer cooling by one single solar thermal system, capable of providing the full thermal autonomy (except for cooking) to buildings at acceptable cost. This looks possible at least under the Mediterranean climate starting from the recently demonstrated EnerSun system. It employs vacuum solar collectors with direct circulation of a dedicated thermo-fluid heated up to 150°C within safe conditions in normal operation, a set of thermal storage tanks, and a single intelligent control system which satisfies the energy demand in real time either directly from the collectors or from thermal storage tanks.

The proposed project aims at making one more significant technological innovation step towards the thermal energy autonomy by including a state-of-the-art adsorption chiller. This system is developed, dynamically simulated and demonstrated in a real building application in south-western France to highlight four main expected benefits:

• A solar thermal autonomy in the Mediterranean area at reasonable cost thanks to the wide use of off-the-shelf components and a state-of-the-art adsorption chiller,
• A significant solar fraction in other regions of central and southern Europe, where simple electrical heaters can play the role of auxiliary power,
• A low level of risk on health of the building occupants thanks to the absence of any wet cooling tower and hazardous materials,
• An environment preservation thanks to the CO2 emission avoidance, the very low noise level of the system, the use of only water and zeolite to convert heat into cold and the use of a bio-sourced thermo-fluid.

A single intelligent control system operates the entire system in an optimal way by:

• Managing the loading of a set of well insulated thermal storage tanks without costly stratification device,
• Conditioning the room temperatures and heating the sanitary water at the real demand levels, either from the thermal storage tanks or from the solar collectors directly,
• Switching from heating to cooling as easily as with a reversible compression chiller or heat pump,
• Interacting with the chiller controller in order to optimise the flows of the three machine circuits according to the demand at maximum COP levels.

Thus, the overall project ambition is:

To design, develop, build and validate a “triple-play” solar heating and cooling system including the valorisation of the heat extracted from the adsorption chiller re-cooling circuit, capable of achieving the thermal autonomy of buildings under a Mediterranean climate and a solar fraction above 50% in central Europe by using a heat transfer fluid having a boiling point above 170°C.

This ambition is supported by five main research objectives:

O1: To have identified, from simulations, the climate conditions and demand profiles for which the COOLSUN “triple-play” solar system concept is optimized to cover 100% of the needs in terms of sanitary hot water, space heating and space cooling in residential and tertiary buildings, and to have refined the numerical model from comparison to the field test measurements.
O2. To have designed the optimal adsorption chiller integration strategy in view of switching easily from heating to cooling and to have estimated the re-cooling energy to remove whilst avoiding a wet re-cooling tower.
O3. To have built a control system which allows an optimal use of the collected solar energy, its storage and its delivery to the loads according to the end user needs without compromising on comfort.
O4. To have built-up an integrated and optimized prototype system ready to run in an automatic mode in the medium range temperature – up to 170°C – in a real pilot application on the Mediterranean border.
O5. To have tested over a complete year the complete system under real life conditions, in order to demonstrate in the end that costs and benefits over a full life time will be competitive against alternative reference solutions (gas burner, wood burner, heat pumps) for applications in collective residential and tertiary buildings.

The coordinator, EnerSun, is a research SME, whose managers were already involved in a "Research for the benefit of SMEs" European project. Combined with industrial capacities of 2 manufacturing SMEs of the consortium and the market capacities of the 3 other SMES, the COOLSUN system has a high potential to meet the market within short time beyond the project.

Project Results:

3 types of results come out of the COOLSUN project:

→ Software
→ Hardware
→ Handbooks

• Software results are:
• A numerical model within TRNSYS environment enabling dynamic simulations of the overall system and its interaction with any building, under any climate;
• A sizing software tool as an Excel-compatible application, likely to be computed for online use at a later stage;
• Control algorithms, which will be embedded into the controller;

The Consortium started from a detailed functional specification of the COOLSUN system, in view of designing an optimal concept focused on the users’ comfort all around the year. The concept has been modeled within the TRNSYS environment by SWT and simulations have run in a standard 120 m² family house. First simulation results confirm the higher performances of the COOLSUN concept compared to the other commercial solutions already tested at SWT. Further simulations simulate the COOLSUN system integrated to the real building where the field tests is performed, near Bordeaux in the south-west of France. These simulations show that the COOLSUN system is likely to confer 90 % autonomy or higher to buildings located in the Mediterranean area with reasonable solar array and heat store sizes. Based on the last simulation, SWT had made the dimensioning of the COOLSUN system components according to the characteristics of the field test building.

The simulations and the sizing software are carried out by LNEG which replaced SWT (left the project in June). The simulation work is validated by field test and shows that CoolSun system is likely to confer 84 % autonomy or higher to buildings located in the Mediterranean area with reasonable solar array and heat store sizes (100% of the cooling demand in Tunis) . Although located in the southern part of France (south west), the same system located in the same building in Bordeaux provides a 64 % solar fraction (99,84% of the cooling demand).

A software application has been developed by LNEG: it works with the building simulated as an input data file with thermal load; but there is also the option to introduce the specifications of a new building total heat loss coefficient, total building heat capacity, occupancy load and windows surface oriented to south.

The design of a solar heating and cooling system is an iterative process. The total solar fraction is imposed, and then after a year simulation is done, changing the main parameters until the required solution is achieved.

• The hardware result is the prototype system indeed, comprising solar collectors, a heat storage subsystem, an 11 kW adsorption chiller, an automation subsystem and further equipment to complete the thermal power unit. The solar thermal generator will be connected to a low temperature floor emitter of 140 m² roughly and to a sanitary hot water distribution network from a 400 liter tank. The emitter will heat and cool the following functional spaces:
• An office (1st floor)
• A meeting room (1st floor)
• A parental suite (ground floor).

In parallel of the first simulations, the adsorption chiller and its testing facility at INVENSOR’s has been adapted to work with the COOLSUN system. Its viscosity and heat capacity being slightly different from those of a water-glycol mixture, the heat transfer from the fluid to the internal cycle of the machine operates differently. Thus some adaptations have been required in the hydraulics to recover the initial performance level of the chiller. The chiller was connected to the control system beginning of May 2013.

Through several workshops pooling the RTD Performers together, the control system has been almost fully specified. Relying on the preliminary control logic developed by ENERSUN, HONEYWELL has initiated the development of the control algorithms. Honeywell and Enersun checked the first version of the control system and first optimizations have been done from 8th to 12th April 2013. A second step of fine-tuning of the control system was done in August 2013 by Honeywell and Enersun.

The project also delivers 2 Handbooks aiming at supporting field workers (installers, maintenance operators, etc.), which will be distributed together with training courses mainly:

 Handbook for the Installation, Operation & Maintenance of the COOLSUN system;

 Handbook of Technology and Market recommendations issued from the results and lessons learned from field tests.

Potential Impact:

Potential impacts

The industrial partners own a unique autonomous solar heating and cooling system, which is not yet available on the market today although the demand is high. Over the last five years the market for solar cooling has increased by 40 to 70% per annum, mainly with cooling-only solutions.

This innovative system brings several intrinsic benefits when compared to existing heating and cooling offers:

 It avoids the use of fossil fuels to cover the whole heating and cooling needs of collective housings and several other end uses (like elder people houses and hotels) under Mediterranean climate conditions.
 It doubles the heating performances compared to standard solar combi systems by working at 100-170°C, and by matching in real time the demand to the energy production and storage.
 It brings a convenient alternative solution to a recurrent cooling demand without impacting the peak load on the electricity network, unlike compressor chillers do. The COOLSUN system consumes very limited electrical power (circulation pumps only whereas valves operate punctually)
 All the components are taken off-the-shelf, except the dedicated thermo-fluid and control system. Yet, their industrialization will not delay the market introduction of the system, since developed by a large industrial partner with a short lead time to mass production.
 It brings a solution to legionella growth encountered in open wet cooling towers of current solar cooling systems: working in closed loops annihilates any risk of pollution as shown in current systems to-day (see technical report published by CEN TC 164), and avoiding the wet re-cooling tower of the adsorption chiller also contributes to this prevention.

The SME participants in the COOLSUN project, which are all active in the solar heating business, will be able to improve their competitiveness by creating new markets and expanding existing markets. Moreover, the innovative COOLSUN product will generate additional downstream service activities for these SMEs: trainings. This secondary activity will offer a great potential both in terms of growth and employment for European SMEs involved in the project.

According to ESTIF, the long term trend is promising a growth acceleration to reach the coverage of up to 47% of the total thermal needs by 2050 if policy makers put an emphasis on research and development in the solar thermal sector, meaning close to 1.500 TWh of cumulated annual energy consumption for an installed capacity of 2.7 TW.

On the long term, recurrent turnover and employment related to the European market for Solar heating and cooling are expected to reach:

 5.000 MWth/year of annually installed solar thermal capacity (+5.000 MWth for water heaters)
 5 Billion € of annual turnover
 50.000 direct employments
 100.000 indirect employments

The COOLSUN technology has the potential to take 5% to 10% of this European market and to play an even more significant role on export markets.

In particular, the following markets segments will be addressed by the COOLSUN system.

• Primary targeted markets
 Hostels and hospitals are big consumers of heating, sanitary water heating and cooling all along the year. For instance, the annual energy consumption of the hospital segment in the EU is estimated at around 125 TWh/year, out of which 100 TWh/year for heating in average in Europe and 60 TWh/year for cooling under the Mediterranean climate. Therefore, they will be targeted markets by the COOLSUN system. This is coherent with the conclusions of the RoCoCo project.
 Office and administrative buildings are big consumers of heating and cooling but less sanitary hot water. In fact, they consume as much heating energy as households, but they have higher electricity consumption due to lighting and air conditioning. According to an analysis of a range of office buildings21, an average of 40 kWh/mÇa was obtained for southern climates, whereas 65 kWh/mÇa were measured in northern European building projects. They are well suited applications for the COOLSUN system since they call a working load all over the year. The agility of the COOLSUN system allows prioritizing space heating and cooling in front of water heating.
• Secondary targeted markets
Collective homes, made of apartments, as well as blocks of individual houses can have an interest in sharing an inter-seasonal storage to cover their heating (mainly), sanitary hot water and cooling demands. Then the high temperature unit is delocalised from in-house and the heating fluid can be distributed through a network at temperature much below 100°C. However, on these market segments, the COOLSUN system will have to compete with other technologies like CHP/CCHP, which can fulfil end users’ needs as well.
 Commercial buildings. In Europe, the cooling energy demand for such buildings varies between 3 and 30 MWh/year. Very little data is available for area-related cooling energy demand. Breembroek and Lazáro (1999) quote values between 20 kWh/mÇa for Sweden, 40–50 kWh/mÇa for China and 61 kWh/mÇa for Canada.

The COOLSUN system is attractive for applications running all along the year, which is the case of hostels and hospitals in warm countries, as well as most of office and administrative buildings. Moreover, these buildings show a real demand for cooling in summer. The explosion of heat pump sales the last decades demonstrates it. This is also why, education buildings have been excluded: they are mostly unoccupied in summer times. Residential buildings have been classified in a second order priority because it is harder to trigger the investment in this market segment and the need for heating and cooling will be much reduced in the next years due to the recent regulations pushing for the reduction of consumptions through better insulation and better strategies for and against direct sunrays.

In 2010, 47% of the final energy consumption in the EU 27 was for heating and cooling and mostly used in the residential sector.

By 2020, this share of the energy is expected to remain at the same level, 46%. Energy saving developments should have a strong impact towards lowering the heat demand, whereas the cooling demand will increase as a result of new expectations in terms of thermal comfort.

Facing climate change and in view of unpredictable prices for conventional fuels due to an end of fossil fuels in the near future, solar systems will gain in significance meeting the steadily increasing energy demand for the generation of energy for hot water, space heating and space cooling.

The simulations show that the Coolsun system covers 100% of the needs of cooling on the southern half of Europe.

Cost estimates show that the cost of primary energy saved thanks to Coolsun system rapidly approaching the cost of fossil fuels.

This trend will continue with the rising cost of fossil energy.

The market of the Coolsun system should be all building with high cooling demand in any country.

The first markets to be exploited are the south countries with high energy cost.

The Coolsun system should be a real opportunity to make a large step go to the energy autonomy.

1.4.2 Exploitation of foreground

The exploitation of the Foreground will be mainly based on the sales of physical COOLSUN components or systems and services delivered by sale influencers.

The COOLSUN Consortium has elaborated an exploitation plan of the project results that takes care of advantaging the COOLSUN SME Participants and of guaranteeing their return on investment.

The agreement is based on the following principles:

~ Each SME Participant must be paid back of its investment in the COOLSUN project out of the results exploitation.
~ The COOLSUN Foreground exploitation plans must take into account the remuneration of the inventors of the claimed Background one way or another (patent license, negotiated lump sum, exploitation rights counterpart, etc.) on fair and reasonable grounds of normal business practice.
~ The SME Participants will take advantage of a rapid and wide spread licensing mechanism or equivalent that will allow third parties to sell COOLSUN systems. It will be an accelerator of their return on investment in the European project.
~ When making profit out of the COOLSUN project results, the SME Participants must have a market competitive advantage on any other company granted by the SME Participants to sell the COOLSUN system.

Further investment for the production and commercialization of the COOLSUN components and system will be needed beyond the project to reach the market with competitive products. This amount is still to be estimated at this stage of the project. Yet, it will have to be added to the effort of the SMEs to be paid back by sales.

A whole exploitation scheme, including the description of the SME Partners’ roles and the working rules of the licensing scheme, has been developed in a way to open the business sharing with third parties.

Dissemination activities:

Scientific publication :

Title : the Coolsun triple play technology-Author: Jorge Facao-LNEG-Date : 24/09/2013 Freiburg SHS2013

Main publications and conferences:
Conference in BlueBat event in Paris 03/04/2012
Conference in Intersolar 2013 in Berlin 18/06/2013
conference in SHC 2013 in Freiburg 24/09/2013

List of Websites:

coolsunsystem.eu