Ziel
To demonstrate that 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 the Summer and is extracted by an intermediary heat pump during the Winter. Apart from showing that energy collected in the summer can be used in the Winter, the optimum system management is to be investigated. If successful the process could be reproduced using an industrial waste heat source. It is expected that about 200 mw/h (17.5 TOE) can be extracted from the aquifer giving a payback of 18 years.
The test bore hole which was drilled permitted all objectives to be attained. It has been clearly shown that clayous portion increased with depth, and this will permit to limit depth of final works. Characteristics of the well are quite suitable for its final use, (control piezometer) and information on difficulties to avoid at the time of definitive works (development, injection problems, ...) were identified. Calculated hydrodynamic characteristics are coherent with those generaly admitted concerning Fontainebleau sands. Nevertheless, an important contrast of permeability between upper and lower part of the aquifer can be observed; the flow velocity, in the upper part of the sands, is greater than foreseen. Particular attention will be given to this factor at the time of study and realization of the storage device.
The school in question is a building of 7 500 m3. Bearing in mind the intermittent use of the classrooms the most appropriate form of heating appeared to be pulsed air. As a certain level of ventilation is necessary, a static recuperator is used to recover heat from the exhaust air. Total heat requirements are 260 mwh per year of which 55 will be furnished by the recuperator. The remainder will be extracted from the hot water store in the Fontainebleau sands found beneath the school.
This storage will be charged during the Summer. Solar panels, functioning as a cold source for a heat pump will supply heat to the underground "nappe"; water will be extracted by way of a "cold" well and its temperature increased from 12 deg C (first year) to 50 deg C by passing through the heatpump's condensor before being reinjected into the nappe through the hot well. The heat pump allows the reinjection temperature to be maintained at a constant level thereby guaranteeing a higher efficiency.
In Winter the warm water is pumped out and heat is transferred to air. The storage is 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 total required storage is about 14 000 m3 at a temperature of 50 deg C corresponding to ca 500 mwh. To charge this storage the following will be installed:"- 2 heat pumps 122 kwth capacity;
- 53 deg C condensor;
- 10 deg C evaporator;
- 250 m2 of collectors.
Storage is in the Fontainebleau sands found to the South and West of Paris having the following characteristics:
- homogeneous structure
- static level at 25 m depth
- depth of strata 30 m.
The wells will therefore be 60 m deep and 80 m apart. Cost of wells 8 000 000 FF; collectors and heat pumps 9 000 000 FF (1983).
Regarding the heating system it has now been decided to use a mixed air-water system. Air for ventilation only and water as the heating medium. Ventilation air is preheated by the hot water circuit.
Thema/Themen
Aufforderung zur Vorschlagseinreichung
Data not availableFinanzierungsplan
DEM - Demonstration contractsKoordinator
78180 MONTIGNY-LE-BRETONNEUX
Frankreich