Final Report Summary - HEAT SAVER (Development of a heat storage system to improve energy efficiency in CHP power plants and in solar driven industrial applications with high relevance to SME) The overall objective of the HEAT SAVER project and the related work is the development of a novel and portable form of thermo-chemical storage to be used for a wide area of applications like combined heat and power (CHP) systems, solar thermal energy sources and others. This technology should help to save energy by allowing otherwise wasted heat to be stored and used at another time and if necessary place. The storage principle has significant advantages compared to other technologies in terms of heat storage density, flexible temperature levels and avoiding losses at long storage periods. To realise this technology five European small and medium sized enterprises (SMEs), two research institutes and one large enterprise (LE) from five European countries formed the consortium of the research for the benefit of SMEs project HEAT SAVER funded by the European Commission (EC). The project started with an intensive scientific / technological characterisation and a laboratory test phase. Storage materials were characterised, the thermodynamics were described, system components were developed, a 15 litre test system was build and various heat exchanger concepts were tested. A second phase followed when the knowledge and results achieved were used to develop and build an up-scaled, containerised and transportable heat storage system with approximately 1000 litre storage capacity. A complete heat storage integrated in a 10 feet standard container was realised including all sub-systems such as tanks, pumps, piping, external heat exchangers, sensors and the control system. This system is used to test and demonstrate the developed thermo-chemical heat storage technology in a relevant scale and - due to the flexible nature of the containerised system - at different test sites within and also beyond the project duration. The testing of the containerised system showed very promising results that the very good values in terms of storage density and process behaviour could also be achieved with up-scaled systems. The HEAT SAVER project has successfully achieved a number of valuable scientific and technological results in the field of storage material parameterisation, process control, heat exchange in/out of the bulk material, gas flow conditions and overall process design. The dissemination activities within the project showed the relevance of the new technology, e.g. for re-usage of waste heat, balancing fluctuating energy demands and increasing the efficiency of industrial processes. A number of customers and business contacts of the SME partners expressed their interest in the heat storage technology. In the following months, the container system can be used for tests with the specific requirements of the potential customers, when needed onsite at their facilities. Efficient heat energy storage technologies will contribute to the international efforts to reduce the use of fossil fuels as well as intensify energy efficiency and the usage of renewable energy sources. It is the aim of the HEAT SAVER consortium that the newly developed technology will become an important element in this market in the near future. Project context and objectives: Scope of the HEAT SAVER project and objectives Approximately 50 % of Europe's energy demand is for heating purposes and anything that can reduce the amount of fossil fuel used can only be for the good. In an age of spiralling demand for fossil fuels, with its associated environmental and geo-political ramifications, the HEAT SAVER system will help reduce Europe's demand for fossil fuels. This will lead to a more sustainable and environmentally friendly energy supply. The overall objective of the HEAT SAVER project is the creation of a novel and transportable form of closed thermo-chemical heat storage. Compatibility with both, existing CHP systems and also with solar heat energy sources is intended. It will comprise, within a containerised body, a zeolite-based thermo-chemical heat store, modular heat exchanger system, a small water store and its associated control systems. By operating alongside a CHP or solar thermal energy system, the HEAT SAVER technology will allow otherwise wasted heat to be stored and used later. By putting the system into a portable container, the stored heat can also be transported by truck or rail to another location where the energy is required. The addition of such a transportable heat storage system will make these two environmentally friendly energy sources even more efficient and thus more economical and cheaper to run, making them more attractive to users. Why thermo-chemical heat storage? Due to the physical principle of thermo-chemical heat storage, the technology has potentially important advantages compared to state of the art systems. Currently, available industrially manufactured thermal storage systems regularly only store sensible heat. They usually use water as a storage medium thus restraining the storage density and limiting the storage temperature level to 100 °C at the most. Latent-heat storage units which may achieve slightly better storage density values regularly lack the required flexibility due to their defined operating temperature. The disadvantage of both systems is their permanent heat loss due to the temperature difference between the medium and its environment. Insulation can reduce this effect, but only to a limited extent. Thermo-chemical heat storage systems are relatively new, promising technology approaches with considerable benefits compared to both the sensible and the latent-heat storage systems. Here, storage densities can theoretically be several times above those of the medium water; i.e. these systems can store much more energy without requiring a bigger construction volume. This energy is bound by means of physicochemical processes thus almost eliminating thermal loss. The combination of both advantages facilitates the efficient time-based storage of thermal energy and its transport. How does it work? For heat storage, a physico-sorptive bond between the reaction pair adsorbent (A) - adsorptive (B) with a preferably high energy turnover is utilised. This principle is reversible: A + B <-> AB + heat. When charging the storage medium, heat is added to substance AB which then dissociates into A and B components. To recover the heat the A and B components have to react with each other again. As long as a reaction between A and B is prevented, the heat which is stored by way of chemical energy cannot be released. The preferred adsorptive is water. It possesses a high phase transition enthalpy, is economic and harmless at the same time. The adsorbent (e.g. zeolite) has to bind the highest amount of water possible by adsorption. Project progress During the first 12 months, the consortium worked intensively at the realisation of the project by a scientific / technological characterisation and a laboratory test phase. A detailed scientific elaboration of the technology and its applications was the basis for the practical work. The thermodynamics and chemistry of the processes have been described and modelled. Laboratory tests with different storage materials were performed and analysed. In combination with the adsorption theory, characteristic curves for multiple materials were set-up. By this, suitable materials based on zeolites were identified and parameterised for different applications. A system for optimal process control was developed and was optimised in the further project progress. A laboratory prototype for the heat storage tank and the heat exchanger system has been set up. Tests followed to evaluate an optimal heat storage tank design. During the second phase of the project, the consortium transferred the results achieved in the laboratory environment into an up-scaled, containerised and transportable heat storage system with approximately 1000 litre storage capacity. This system is used to test and demonstrate the developed thermo-chemical heat storage technology in a relevant scale and - due to the flexible nature of the containerised system - at different test sites within and also beyond the project duration. A complete heat storage system integrated in a 10 feet standard container was developed, designed and build. All sub-systems such as tanks, pumps, piping, external heat exchangers, sensors and the control system were specially designed for this new and innovative thermo-chemical heat storage which is not available on the market, yet. One of the main challenges is the heat transfer in and out of the storage material. An efficient solution will lead to significantly higher heat storage capacities compared to state of the art (sensible) water heat storages. The new storage principle has the potential to achieve 3 to 10 times higher specific storage densities than water stores. Therefore - as one of the innovations - a new heat exchanger system was developed for the up-scaled system (1000 litre storage volume) that reflects the requirements to the heat storage system and the special behaviour of the adsorption process used to store the heat. The heat exchanger is designed to efficiently transfer the heat in and out of the storage material (zeolite, silica gel or other porous materials). At the same time, the heat exchanger system is relatively cheap and simple constructed. The commissioning and testing of the containerised system showed very promising results. It is possible to control the storage process and to adopt the heat store to different temperature levels regarding the heat source as well as the heat consumer. The short testing phase at the end of the project will be continued afterwards to get more practical experience and results with as many different process parameters as possible. It is planned to test the heat storage container at different test sites of project partners and potential customers. Project results: The HEAT SAVER project has successfully achieved a number of valuable scientific and technological results. The initial literature and laboratory work enables a deeper understanding of the storage material characteristics, the thermo-dynamics and the physical background of the heat storage principle with regard to a real technological application. The limiting factors and the main challenges were identified and technical measures to overcome these were taken. Innovative new concepts were developed. The thematic priority of this work was in the field of the storage material parameterisation, the process control, the heat exchange in/out of the bulk material, the gas flow conditions and the overall process design. Within the project, material data of suitable heat storage materials was gathered by experiments and evaluation of literature. This information is exclusive and specifically on the usage of zeolites and zeolite-like materials in thermo-chemical heat storage systems and (as secondary market) in absorption heat pumps. The control system and algorithms are especially developed for thermo-chemical heat storage systems. Various ways of process control are tested to be able to adopt the heat storage behaviour to the needed characteristics of the used heat sources and heat consumers. A totally new concept of a bulk material heat exchanger including also measures to enhance the water vapour flow through the storage material bulk was developed and successfully tested. It improves the process dynamics and efficiency, in specific the heat conduction though the (rather low conductive) storage material. At the same time it uses significantly less material and less storage volume is occupied compared to other heat exchangers like for example finned tube heat exchangers. The new heat and mass flow system contains of standard, semi-finished components what makes it cost efficient and easy to manufacture. Further on, the system is very easy scalable to different heat storage reactor sizes and shapes. As part of the process development, the overall design of thermo-chemical heat storage was improved and integrated on a containerised system. Since no thermo-chemical heat storage systems are on the market yet and the number of research activities was low this represents a significant step forward compared to the state of the art. As a result a transportable, containerised storage system with a storage volume of 1000 litres is available for testing at different test sites and also with different heat storage materials. Further concepts for simplifying and economising the complete system by reducing the number of expensive system components like pumps and valves were also developed. Potential impact: An important contribution to the achievement of climate protection targets is an improved utilisation ratio for both fossil and regenerative primary energy sources. This is done by secondary usage of energy which was not used during its first application. A case in point is the utilisation of waste heat created by combustion engines during the generation of power from in CHP plants. In addition, there are many more processes in commerce, energy supply and manufacturing industry which generate large amounts of waste heat. Against the backdrop that about 50 % of the EU energy requirements are needed for heat production it becomes apparent that there is great potential for optimising energy use. To optimise energy efficiency of processes, there is a need for compact and flexible storage systems to decouple or compensate the supply and demand for heat in terms of location through mobility and with regard to time through minimisation of heat loss. Currently available industrially manufactured thermal storage systems regularly only store sensible heat. They usually use water as a storage medium thus restraining the storage density and limiting the storage temperature level to 100 °C at the most. Latent-heat storage units which may achieve slightly better storage density values regularly lack the required flexibility due to their defined operating temperature. The disadvantage of both systems is their permanent heat loss based on the fact that the driving gradient in both systems is the temperature difference between the medium and its environment. Insulation can reduce this effect, but only to a limited extent. Within the project, it has been experienced that the HEAT SAVER technology has a high potential to be used for efficient heat storage for various applications. Here storage densities can theoretically be multiple (up to 10 times) above those of the medium water; i.e. these systems can store much more energy without requiring a bigger construction volume. Temperature levels for charging and discharging are more flexible. The energy is bound by means of physicochemical processes thus almost eliminating thermal loss over the time. The combination of these advantages facilitates the efficient time-based storage of thermal energy and its transport. Numerous customers of the HEAT SAVER SME partners expressed their interest to enable the re-usage of waste heat, balance fluctuating energy demands or increase the efficiency of industrial processes. According to the project results, 1 m3 of storage volume could store and reuse about 40 MWh per year assuming 250 charging / discharging cycles which are realistic for CHP plants or industrial solar systems. With the heat storage energy and costs can be saved. The necessity of new heat storage concepts and technologies as an elementary part of a future energy supply becomes especially obvious with regard to the before mentioned fact that about half of the energy consumed in the EU is used as heat. It is obvious that efficient heat energy storage technologies will contribute to the international efforts to reduce the use of fossil fuels as well as intensify energy efficiency and the usage of renewable energy sources. It is the aim of the HEAT SAVER consortium that the newly developed technology will become an important element in this market in the future. In parallel to the technical work, dissemination activities took place and the involved SMEs had meetings with almost 20 different companies that are interested in the HEAT SAVER heat storage system to be used in their specific applications. Workshops and presentations show that such systems are needed for re-usage of waste heat, balance fluctuating energy demands and increase the efficiency of industrial processes. In the following months, the container system can be used to test the technology with the specific requirements of these applications and, if needed, onsite at the interested companies. Further activities regarding a follow-up demonstration project are planned. Project website: http://www.heat-saver.eu Contact data coordinator: Fraunhofer IGB Mike Blicker Mike.Blicker@igb.fraunhofer.de Phone: +49-711-9703539
