Completed Annexes

Annex 1, Large Scale Thermal Storage Systems Evaluation
Annex 1 was a technical and economic evaluation of various storage concepts presented by the participating countries. The results of this work formed the basis for subsequent Annexes. The final report was published in October 1981.The Annex was formally closed at the Executive Committee Meeting in April 1983. Participating countries: Switzerland (OpA), Belgium, CEC, Denmark, Germany, Sweden, USA.

Annex 2, Lake Storage Demonstration Plant in Mannheim
Annex 2 had the objective of developing a seasonal lake storage and to demonstrate the feasibility by the construction of a large scale pilot plant in Mannheim, Germany. Construction of the plant was canceled after failing to achieve an economic design.

Annex 3, Aquifer Storage Demonstration Plant in Lausanne Dorigny
Annex 3 involved the design, construction and operation of a high temperature aquifer storage in Lausanne Dorigny. The storage consisted of a vertical well with horizontal drains. The project was commonly called SPEOS. Waste heat from a municipal facility was stored in summer and used for space heating and domestic hot water of a gymnasium. Collaboration involved seven countries and terminated in 1989. Participating countries: Switzerland (OpA), Denmark, USA, Sweden.

Annex 4, Short Term Water Heat Storage Systems
Annex 4 reviewed the theory, techniques and application of hot water storage systems and produced a state of the art report. It focused on various measures to maintain thermal stratification. The Annex was closed in 1988. Participating countries: The Netherlands (OpA), Germany, Sweden, USA

Annex 5, Full Scale Latent Heat Storage Installations
Annex 5 involved the installation and monitoring of latent energy storage installations with the objective of evaluating their technical and economic feasibility. The Executive Committee recommended reviewing the state-of-the-art of latent heat stores and a workshop was held in 1984 sponsored by the German Ministry for Research and Technology. As a result of the workshop recommendation to concentrate on monitoring pilot and demonstration plants to provide reliable performance data, an Annex on Full-scale Latent Heat Storage Installations was initiated in 1988. Germany has provided the Operating Agent. The Annex was terminated in 1992. Participating countries: Germany (Op.A), Sweden, USA.

Annex 6, Environmental and Chemical aspects of Thermal Energy Storage in Aquifers and Research and Development of Water Treatment Methods
Annex 6 dealt with the chemical and environmental aspects of thermal energy storage in aquifers. A major potential problem of aquifer energy storage is the scaling an clogging of wells and heat exchangers. To avoid these problems reliable and ecologically sound methods of water treatment are required. The development and testing of the chemical, microbiological and environmental effects of ground-water treatment methods were the objectives of Annex 6. The work was initiated in 1987 and extended through twelve experts meetings into 1993. The Netherlands provided the Operating Agent and nine countries are participating. The Annex was formally closed by the Executive Committee in 1996. Participating countries: The Netherlands (Op.A), Canada, Denmark, Finland, Germany, Sweden, Switzerland, USA.

Annex 7, Innovative and Cost Effective Seasonal Cold Storage Applications
Annex 7 aimed to demonstrate innovative, energy efficient and cost effective cold storage design for a variety of building types and industrial applications to encourage the adoption of cold storage as a standard design option. More specifically, it evaluated effective storage control and operating strategies; evaluated combined hot and cold storage for increased energy efficiency and cost effectiveness; and conducted national market studies for the developed technologies. A planning workshop in Sweden initiated the work in January 1989 and the activities extended through eight experts meeting into 1993. The Annex was formally closed by the Executive Committee in 1996. Participating countries: Canada (Op.A), Germany, Holland, Sweden.

Annex 8, Implementing Underground Thermal Energy Storage Systems
Annex 8 aims to speed the introduction of Underground Thermal Energy Storage in the building, industrial and agricultural sectors. It will encourage the adoption of energy storage in standard project designs by developing procedures and tools based upon documented applications in various energy efficient systems. Screening and decision tools will be provided to ensure ecologically sensitive applications. The first experts meeting was held May 1994 in Sweden. Participating countries: Sweden (Op.A), Belgium, Canada, Germany, The Netherlands, Turkey, USA, (Japan).

Final Report of Annex 8

Annex 9, Electrical Energy Storage Technologies for Utility Network Optimization
Annex 9 will examine the potential role of electrical storage technologies in optimizing electricity supply and utilization It will identify and overcome barriers to widespread adoption of electrical energy storage technologies through successful demonstration projects. It was proposed by EA Technology Limited in UK as a result of the recommendations of the Energy Storage Strategy Workshop held in Montreal during January 1995. The annex started July 1996. Participating countries: Canada, Germany, Netherlands, UK (OpA), USA. A few more countries are expected to join within the near future.

- Final Report of Annex 9 - 134 kB

Annex 10, Phase Change Materials and Chemical Reactions for Thermal Energy Storage
The general objectives of Annex 10 are to solve technical and market problems for a better market opportunity for thermal energy storage systems utilizing PCM or chemical reactions in the building system, the agricultural and industrial sector and to broaden the knowledgebase and disseminate information. The annex started in 1997. Particiapting countries are: Canada, Finland, Germany, Japan, Poland, Sweden (OpA), Switzerland, United Kingdom, and Turkey. Further members could be Bulgaria and Australia. Click here to visit Annex 10 Homepage

Annex 12, High-Temperature Underground Thermal Energy Storage (HT UTES)
The objectives of this task are to demonstrate that HT-UTES can be attractive to achieve more efficient economical and environmentally benign energy systems, and to disclose requirements and find problem solutions for reliable long-term ope-ration. The type of UTES-systems concerned shall be confined to Aquifer Storage (ATES) and Duct/Borehole Storage (DTES). This annex was started at the end 1997 with Germany as Operating Agent. For more information on Annex 12 please click here .

Annex 13, Design, Construction and Maintenance of UTES Wells and Boreholes
Annex 13 is a result of the Energy Storage Strategy Workshop held in Montreal during January
1995. The annex was approved by the ECES IA at the end of 1997 with Sweden as Operating Agent. For more information on Annex 13 please click here .

Annex 14. Cooling with TES in all Climates
Annex 14 was decided at XC46 in Luleå (14-15 June 1999) as a result of the Antalya kick-off Workshop (4-5 June 1999) and years of discussions within the Executive Committee. The overall objective of Annex 14 is to employ research, development and feasibility studies to advance the prospects of cooling with TES technologies for applications within a variety of energy systems and climate conditions and to encourage their use as a standard design option. The Annex, will rely heavily on the activities and results of Annexes 6, 7, 8, 10 and 13 to encourage energy efficiency and increased sustainability of the global energy resource by stimulating the expanded use of TES in innovative, energy efficient and cost-effective projects in participating countries. Operating Agent: Turkey. For more information please visit Annex 14 Homepage

Annex 17, Advanced Thermal Energy Storage Techniques – Feasibility Studies and Demonstration Projects
The objectives of this Annex is to overcome technical and market barriers for introduction of long- (seasonal) or short-term phase change and chemical reaction thermal energy storage for energy savings and for reduction of peak demand of energy in buildings, agricultural and industrial applications. Operating Agent: Sweden. For more information please visit Annex 17 Homepage

Annex 18, Transportation of Thermal Energy Utilizing Thermal Energy Storage Technology
A key component in a sustainable energy system is to be able to use thermal energy from various sources at a consumer located at a distance from theses sources. For this purpose, the thermal energy has to be transported from one place to another. This could be achieved by using thermal energy storage technology. Depending on the distance, the storage medium could either be pumped through pipelines or for longer distances the TES itself could be transported on a truck or a train. The crucial properties of the TES for the technical and economical feasibility are the storage capacity per volume and weight and the possible charging and discharging power, which affects the possible number of storage cycles per time.

The Annex 18 homepage can be found here.

The final report is available here .

Annex 19, Optimised Industrial Process Heat and Power Generation with Thermal Energy Storage
Previous activities in the IEA Implementing Agreement “Energy Conservation through Energy Storage” has achieved significant progress in thermal energy storage technologies for energy savings and for reduction of peak demand of energy in buildings and in advancing the prospects of cooling with TES technologies.
The potential for thermal energy storage and regenerative heat transfer for the industrial process heat sector for efficient energy utilisation, heat recovery and storage of high temperature waste heat as well as the need for energy storage for power generation based on new conversion techniques and renewable energy resources (RES) is a concern of several national and international research strategies. Both areas are directed to applications and processes at high temperature. In this context “High Temperature” is defined to be higher than 120 °C as required for comfort heating and where water cannot be applied as heat transfer fluid.

The final report is available here .

Annex 20, Sustainable Cooling with Thermal Energy Storage
Renewable and natural energy sources, main components of sustainable energy systems, can only be made continuously available to users through thermal energy storage (TES). In addition to heating TES provides several flexible alternatives for cooling systems. Recent discussions on topics like global warming and heat waves have brought attention once again to energy efficient cooling systems utilizing renewable energy sources. Cooling demand has already been increasing due to the evolving comfort expectations and technological development around the world. Climate change has brought additional challenges for cooling systems designers. New cooling systems must use less and less electricity generated by fossil fuel based systems and still be able to meet the ever increasing and varying demand.

- Final Report of Annex 20 - 7 MB

Annex 21, Thermal Response Test for Underground Thermal Energy Storages
hermal Response Test (TRT) is a measurement method to determine the heat transfer properties of a borehole heat exchanger and its surrounding ground in order to predict the thermal performance of a ground-source energy system. The two most vital parameters are the effective thermal conductivity of the ground and thermal resistance within the borehole. These measurement results are important for proper BTES design but also for commissioning and failure analysis. This method has significantly supported the rapid spreading of BTES systems and the introduction of this technology in “new” countries.

The overall objectives of Annex 21 are to compile TRT experiences worldwide in order to identify problems, carry out further research and development, disseminate gained knowledge, and promote the technology. Based on the overview, a TRT state of the art, new developments and further work are studied.

Official members of Annex 21 are currently: Canada, Finland, Germany, Japan, Korea, Sweden, Norway, Turkey and Spain. Further, the following countries participate as observers: Argentina, Austria, Belgium, China, Italy, Switzerland, The Netherlands and USA. Seven experts meetings were held so far. The Annex will expire in summer 2011.

Information on the outcome of the Annex 21 experts meetings can be found at
For more information contact Manfred Reuß
Annex 21 final reports are available here.

Annex 23, Applying Energy Storage in Ultra-low Energy Buildings
Sustainable buildings will need to be energy efficient well beyond current levels of energy use. They will need to take advantage of renewable and waste energy to approach ultra-low energy buildings1. Such buildings will need to apply thermal and electrical energy storage techniques customized for smaller loads, more dis-tributed electrical sources and community based thermal sources. Lower exergy heating and cooling sources will be more common. This will require that energy storage be intimately integrated into sustainable building design. Many past appli-cations simply responded to conventional heating and cooling loads. Recent re-sults from low energy demonstrations, distributed generation trials and results from other Annexes and IAs such as Annex 37 of the ECBCS IA, Low Exergy Sys-tems for Heating and Cooling need to be evaluated. Although the ECES IA has treated energy storage in the earth, in groundwater, with and without heat pumps and storing waste and naturally occurring energy sources, it is still not clear how these can best be integrated into ultra-low energy buildings capable of being rep-licated generally in a variety of climates and technical capabilities.

Energy storage has often been applied in standard buildings that happened to be available. The objective was to demonstrate that the energy storage techniques could be successfully applied rather than to optimize the building performance. Indeed the design of the building and the design of the energy storage were often not coordinated and energy storage simply supplied the building demand what-ever it might be.

For more information contact Fariborz Haghighat

Annex 23 Final Report is available here.

Best Practice for Architects and Engineers Report is available here.

Annex 24, Material Development for Improved Thermal Energy Storage Systems

For the performance of thermal energy storage systems their thermal energy and power density are crucial. Both criteria are strongly depending, beside other factors, on the materials used in the systems. This can be the storage medium itself, but also materials responsible for the heat (and mass) transfer or for the insulation of the storage container.

After a number of thermal energy storage technologies have reached the state of prototypes or demonstration systems a further improvement is necessary to bring theses systems into the market. The development of improved materials for TES systems is an appropriate way to achieve this. The material solutions have to be cost effective at the same time. Otherwise the state of the existing technologies can not be brought closer to the market.

The world wide R&D activities on novel materials for TES applications are not sufficiently linked at the moment. A lot of projects are focusing on the material problems related to their special application and not towards a wider approach for TES in general. The proposed Annex should help to bundle the ongoing R&D activities in the different TES technologies.

Annex 24 final reports are available here.

For more information contact Andreas Hauer .

Annex 25, Surplus Heat Management using Advanced TES for CO2 mitigation

The world’s total energy supply is 136500 TWh/year whereas the energy use is approximately 94000 TWh/year (IEA Key Statistics, 2008). By inspecting these figures, one can see that close to 1/3 of the world’s energy supply is “wasted” in energy conversion. In reality, the number is even larger, perhaps as much as 50%, since for example the tank-to-wheel efficiency of engine driven transportation is only 20%, and boiler efficiencies seldom are above 90%. From a sustainability perspective, increasing the efficiency in many energy conversion processes is crucial. As the demand for energy increases in all sectors, and all over the world, waste heat management will be a cost-effective way of securing the supply of energy and power while mitigating the emissions of CO2. Such management is most effectively done in cases where the waste heat flow are large, like industrial processes, or in cases where the value of increases waste heat utilization is large, like in the vehicles and transporting goods sector. Recent advances in compact thermal energy storage has encouraged this initiative to explore solutions where waste heat management can be enhanced, facilitated and even enabled by integrating thermal energy storage technology.
The general objective of this Annex is to identify and demonstrate cost-effective strategies for waste heat management using advanced TES. New knowledge will be generated with regards to:

  1. The potential for advanced TES to minimize process waste heat through better process integration, enabling the use of waste heat for internal heating demands or cooling demands (via heat driven cooling).
  2. The potential for advanced TES to cost-effectively increase waste heat driven power generation in industrial applications.
  3. The potential for advanced TES to enable external use of heat from industrial-scale processes through effective thermal energy distribution.
  4. The potential for advanced TES to increase the utilization of waste heat in vehicles like on-board cooling and minimization of cold-start.
  5. The potential for advanced TES to increase the use of waste cooling (e.g., the large cooling potential associated with LNG regasification) and free cooling for comfort cooling applications.

Thus, a sub-goal of this proposed annex is to really dig into the waste heat utilization issue from a very broad perspective, and show the great potential for using advanced TES towards reaching a resource efficient energy system where waste heat (and cold) is minimized. This has a good potential for attracting a large number of participants from a variety of disciplines and levels of R&D (basic research to commercial systems).

For more information contact Luisa Cabeza .
Annex 25 final reports are available here

Annex 26, Electric Energy Storage: Future Energy Storage Demand

The future of electricity network involves a massive penetration of unpredictable renewable energies. For insuring network stability as well as for maximizing the energy efficiency of such networks, storage is a key issue. Up to now, the integration of renewable energies did not take into account the demand side and was performed in a “fit and forget” way. The optimum evolution in an economic perspective is in the future to have an integration that is respecting the needs. One solution – beneath demand side management and grid extension – is the use of energy storages. The main purpose of adding energy storage systems in the electricity grid is to collect and store overproduced, unused energy and be able to reuse it during times when it is actually needed. Essentially the system will balance the disparity between energy supply and energy demand. Worldwide between 2% and 7% of the installed power plants are backed up by energy storage systems (99% pumped hydro systems). The future demand of energy storage devices is actually unknown. Only the main influence factors on this demand are known.
The overall objective of this task is to develop a method or approach to calculate the regional energy balancing demand and to derive regional storage demand rasterizing the area and taking into account that there are competitive technical solutions. This objective can be subdivided into ten specific objectives:

  • To rasterize the whole area to typical small self-similar elements,
  • to identify and characterize typical fluctuating energy demand for different elements which stands for different regions and grid situations (e.g. intermeshing),
  • to identify and characterize typical fluctuating energy production (wind, PV) for different elements which stand for different regions and renewable energy potential (e.g. wind velocity),
  • to identify and characterize typical conventional energy production (gas turbine, nuclear power plant) for different elements which stand for different regions and conventional energy production,
  • to reduce different grid structures to a fistful typical systems and to simulate their inner intermeshing and their exterior connectivity (transport, import, export),
  • to derive balancing demand for each typical region,
  • to derive energy storage demand as a share of the total balancing demand, taken into account that the most successful economic solution will be realized,
  • to develop a method or model to transfer these results to other countries and regions,
  • to assess the technical and economical impact of energy storages on the performance of the energy system, and
  • to disseminate the knowledge and experience acquired in this task.

A secondary objective of this task is to create an active and effective research network in which researchers and industry working in the field of electric energy storage can collaborate.

Annex 26 final report is available here
2-pager on Annex 26 is available here