Related EU Projects

This research project aimed to determine the heating and cooling potential of aquifer thermal energy storage (ATES) systems in the Mediterranean climatic zone. The project was carried out in greenhouses at the Cukurova University, Adana, during 2005-2006. For this purpose, two plastic greenhouses, each having an area of 360 m², were used. One of them was heated and cooled by an ATES system. In the second one, conventional heating and cooling systems were used. The inside and outside temperatures of the greenhouses, as well as ground water and exchanger water temperatures were recorded throughout the experimental period. Tomato crop was grown in both greenhouses and plant growth and fruit yield were measured. Energy costs of the greenhouses (fuel oil for the conventionally heated greenhouse and electricity for the ATES system) were also calculated. Consequently, these two systems were technically and economically compared.

The collected data showed that ATES systems have good potential for climatisation, both for heating and cooling, of greenhouses in the Mediterranean climatic zone. Between October 20^th and April 10^th, the inside temperature of the ATES system heated greenhouse was never below critical level (120 ℃) and thanks to this performance, the ATES greenhouse never used any fuel oil. On the other hand, temperature fluctuations in the ATES greenhouse were less than the conventionally heated one. The energy cost saving with ATES for heating was about 70% in comparison with the conventionally heated (with fuel-oil) greenhouse. With respect to tomato yield, the greenhouse that was heated by the ATES system resulted in approximately 20% more yield than that in the conventionally climatised one.

Turgut, B., Dasgan, H., Abak, K., Paksoy, H., Evliya, H. and Bozdag, S. (2009). AQUIFER THERMAL ENERGY STORAGE APPLICATION IN GREENHOUSE CLIMATIZATION. Acta Horticulturae, (807), pp.143-148.

In the year 2000, a system that uses solar energy in combination with Aquifer Thermal Energy Storage (ATES) was being designed. Its aim was to conserve a major part of the oil and electricity used for heating or cooling the Cukurova University, Balcali Hospital in Adana, Turkey. The general objective of the system was to provide heating and cooling to the hospital by storing solar heat underground in summer and cold in winter. As the main source of cold energy, ventilation air at the hospital and surface water from the nearby Seyhan Lake was to be used.

Paksoy, H., Andersson, O., Abaci, S., Evliya, H. and Turgut, B. (2000). Heating and cooling of a hospital using solar energy coupled with seasonal thermal energy storage in an aquifer. Renewable Energy, 19(1-2), pp.117-122.

The project aim was to demonstrate that space heating by means of solar energy and aquifer storage is technically feasible and capable of primary energy savings +/- 50%. The project was built in Bunnik for the company Bredero. The office building to be heated consisted in three units of 9,000 m² total floor surface with an annual heat demand of 660 MWh. The building was not equipped with a cooling system except for the computer room.
The heating system contained: flat plate solar collectors, short term energy storage, long term thermal energy aquifer storage (with an estimated injection and extraction of about 18,000 m³), a gas engine driven heat pump and a conventional gas boiler. For space heating, the waste heat of the computer room cooling system was used (95 MWh/yr). The annual gas consumption of the heating system was estimated to be 392 MWh. There were three operating modes of the plant:
Summer: heat from the collectors and the computer cooling system is injected into the Aquifer

Spring/Autumn: space heating by a heat pump with heat supply from solar collectors and cooling system waste heat

Winter: space heating by heat pumps with heat supply from an aquifer and a cooling system and additional heating by a gas boiler at low outside temperatures. The solar system is not in operation in the wintertime.

The project’s aim was to demonstrate how a school of 16 classrooms (7,500 m³) can be heated from solar energy which is stored in an aquifer (aquifer des sables de Fontainebleu) during summer and is extracted by an intermediary heat pump in winter. Apart from showing that the energy collected in summer can be used in winter, the optimum system management was investigated. The process could have been reproduced using an industrial waste heat source, if successful. It was expected that about 200 MWh could be extracted from the aquifer giving a payback of 18 years.
Bearing in mind the intermittent use of the classrooms, the most appropriate form of heating appeared to be pulsed air. Since a certain level of ventilation is necessary, a static recuperator was used to recover heat from the exhausted air. Total heat requirements were 260 MWh per year of which 55 were furnished by the recuperator. The remaining, were extracted from the hot water store in the Fontainebleau sands, which is found beneath the school. This storage was charged during summer. Solar panels, functioning as a cold source for a heat pump, supplied heat to the underground "nappe"; water was extracted by way of a "cold" well and its temperature increased from 12°C (first year) to 50°C by passing through the heatpump’s condensor before being re-injected into the nappe through the hot well. The heat pump allowed the reinjection temperature to be maintained at a constant level thereby guaranteeing higher efficiency. In winter, the warm water was pumped out and heat was transferred to air. The storage was dimensioned to cover all the needs of an average year, however if the temperature of the nappe is too low the water can be used as the cold source of the heat exchanger.

The aims of this project were:

• To obtain practical experience from the establishment and operation of a low temperature heat storage system in a limestone aquifer, in connection with a district heating system; and
• To demonstrate the possibilities of commercial use of this type of aquifer in heating systems in combination with heat pumps.

The waste heat from a nuclear research reactor was used as a heat source for a 2.2 MW heat pump that was connected to a district heating system. The temperature of this waste heat was between 40°C and 45°C. However during normal operation, approximately three times as much waste heat was available as it could have been utilised by the heat pump. The nuclear reactor used to close down for 5 days every 4 weeks and during this period heat was being supplied by the combustion of oil. The idea was to store surplus heat from the reactor in a limestone aquifer and extract this heat during periods of reactor shutdown. Two main wells 100 metres apart were used, one for injection of the heated water, and the other one for extraction. The extracted water was expected to be at a temperature of around 30 °C. Two further wells were drilled for measurement purposes and equipped with temperature and pressure transducers that were connected to a computer system.

In this project, the extension of the existing cooling capacity was realised with an Aquifer Thermal Energy Storage (ATES) instead of a conventional chiller. Compared with a chiller, the use of ATES reduced the electricity consumption for cooling by 50%. Moreover, the heat that was extracted from the ventilation supply air in summer was stored in the aquifer to be utilised in winter for (pre)heating ventilation air. The integration of the ATES system in the installation with 2 chillers enabled also short-term cold storage in summer. Therefore, the risk of cold shortage due to climatic influences (warm summer and/or mild winter), was compensated for without costly investments in extra chiller capacity. Furthermore, the combined use of the aquifer system for seasonal cold and heat storage, as well as short-term cold storage made the system more profitable. Consequently ATES can also be attractive for smaller projects with existing cooling systems that have to be extended. Therefore, this will enlarge the market potential for ATES. For instance, in the first half of summer 1994 (April, May, June and July) the storage delivered 256 MWhth (megawatt hours of heat) cold and 82,000 kWhe (kilowatt hours of electricity) were saved. No additional cooling was applied thanks to the lower temperature in the cold storage.

The project demonstrated:

- That the required extension of the cooling capacity in the hospital can be realised by storage or "winter cold" in a sand-layer (aquifer) in the soil, and that such a storage system can be integrated in the existing cooling system.

- The technical and economical feasibility of combined seasonal cold and heat storage in an aquifer for cooling and (pre)heating ventilation supply air.

- And the advantages of using the aquifer for short time storage of cold that is loaded at night with the available chillers, thus creating extra facilities for energy management and compensating for risks of cold shortage due to climatic influences.

This project was an innovative system for the storage of residual heat in an aquifer at the University of Utrecht. By using heat storage, the number of operating hours of the heat and power installations during the summer period was increased as the heat produced was usefully employed. The stored heat was used during winter for space heating. As a consequence, less gas had to be used for space heating during the winter months and during summer less electricity had to be purchased. The degree of utilisation of the heat and power installations was increased, while the primary energy consumption was reduced.

The aim of the project was to demonstrate a practical applicability of heat storage in aquifers, in combination with combined heat and power installations in order to augment the useful exploitation of these installations. These installations were regulated on the basis of the heat requirements of the buildings of the university complex, which meant that at a reduced heat demand during summer, the installations were run at part load to avoid unprofitable production of excess heat. This led to a lower total yield of the heat and power installations and additional electricity also had to be purchased. As a result, residual heat in the form of water at a temperature of 90°C was stored in an aquifer and then used to produce electricity, which was used by the university complex. The stored residual heat was used in winter for the heating of a few buildings of the complex. In the feasibility study it was estimated that a thermal result (the heat stored which was then retrieved) of about 65% to 75% in the third year was achieved. At the realisation of the heat storage, additional data of the soil structure was obtained, thus soil structure could be represented better diagrammatically.