Thermal Response Test for Underground Thermal Energy Storages (Annex 21)
Thermal 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
If you have related topics, publications, applications or projects which could be included in the work of this Annex, please contact Manfred Reuß
Thermal Energy Storage Applications in Closed Greenhouses (Annex 22)
Increasing attention is being paid to thermal energy storage (TES) in greenhouse systems as a means of enhancing crop production while reducing primary energy (fossil fuel) use and operational impacts to soil, water and air. TES leads to the ‘closed or nearly closed’ greenhouse concept, which subsequently allows for active environmental control, avoiding the need to control of environmental variables by opening and closing windows – an act which also unintentionally releases CO2.
Thermal energy storage has an important contribution to make to the viability and sustainability of horticultural greenhouse systems because it allows for a renew-able, continuous, and adaptable supply of heating, cooling, and dehumidification. The nature of this contribution is cardinal in light of concerns of increasing fossil fuel expenses and climate change.
The industries which provide us with food and plants (i.e. potted plants, flowers, sod, trees) strive to maximize the outputs of their greenhouse system while simul-taneously minimizing their inputs. They do this to meet ever-increasing demands for competitive pricing as well as product quality and security assurances. There are three key ways in which the integration of TES simultaneously addresses the system’s outputs and inputs:
- Energy savings
- Controlled CO2 and humidity
- Fewer chemicals
If you are interested in this new Annex activity please contact Frank Cruickshanks .
Applying Energy Storage in Ultra-low Energy Buildings (Annex 23)
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.
Responsible for this proposal of a new Annex is Fariborz Haghighat .
Annex 23 Subtask A-B Final Report is available here
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.
For more information contact Andreas Hauer .
Surplus Heat Management using Advanced TES for CO2 mitigation (Annex 25)
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:
- 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).
- The potential for advanced TES to cost-effectively increase waste heat driven power generation in industrial applications.
- The potential for advanced TES to enable external use of heat from industrial-scale processes through effective thermal energy distribution.
- The potential for advanced TES to increase the utilization of waste heat in vehicles like on-board cooling and minimization of cold-start.
- 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).
Electric Energy Storage: Future Energy Storage Demand (Annex 26)
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.
If you are interested in this new Annex activity, please contact Christian Doetsch .