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Content archived on 2022-12-27

ACTIVE SOLAR HEATING FOR UNDERFLOOR AND WATER HEATING

Objective

This project demonstrates an innovative combination of flat plate collectors, under floor heating and domestic hot water production for a single building containing 20 flats. A reference building with no solar collectors will be monitored thereby leading to a reliable comparison with the solar building. The 130 m2 of liquid solar collectors are expected to provide a total 3 TOE per year or ca 300 kwh/yr/m2. A payback of less than 20 yrs is expected.
The operation of the system can be considered successful from the technical point of view. It is demonstrated that the system, which is operated in winter time in a 'direct floor heating' mode and in summer time in a hot water (pre-) heating made, can cover a considerable part of the heating requirements.
Following quantitative results are obtained :
Winter time operating mode :
The energy recovered by the solar collectors and delivered to the floor heating system is a 235 kWh/m2 solar collector surface, which is equivalent to a 52 % efficiency of the solar system. This amount of energy has covered about 45 % of the total heating needs (which are low due to a high insulation level of the houses). The solar contribution is relatively important in the spring and autumn period and at that time the solar system covers nearly 60 to 80 % of the needs, while in winter time the solar coverage is only 20 to 30 %.
Summer time operating made :
The system delivers heat to the domestic hot water supply from half May to half October. The contribution of the solar system is 123 kWh/m2 solar collector surface. This is equivalent to 24 % collector efficiency. This result is lower than expected and is due to a bad design of the conventional part of the system (heat distribution and auxiliary heating).
The experience of this project confirms the technical validity of the 'direct floor heating' solar system. Modifications (simplifications) leading to a 25 % reduction of the solar system costs can be envisaged for the DHW pre-heating system.
From an economical point of view, the payback period is still rather long (estimated 15 to 20 years), although this value could change quickly if the fossil fuel prices change. Therefore, this technology should be considered successful on a medium to long term basis.
The system comprises 4 main elements:
- 130 m2 flat plate solar collectors through which a mixture of water and glycol is pumped. The panels are vertical, being attached to the building's south facing wall.
- concrete floor through which the heated liquid is passed when space heating is required. Beneath the floor, which acts as a low temperature radiant surface, insulation has been placed. Total floor area is 820 m2.
- during periods when no space heating is required, the heat collected is transferred by way of a second circuit into a 5,000 litre water storage tank. The preheated water is then heated to the desired temperature by individual (to each flat) electric heaters.
- a battery of electric convector heaters supply auxiliary heat for space heating.
The system control and design is such that either space heating or water heating may be supplied. The building design also incorporates passive energy design. The attraction of this system is that it is designed for ease of installation. This project will provide useful data regarding not only system performance but also how design improvements can further decrease costs below the present 430,000 FF. Of note is the fact that an identical building not equipped with a solar installation, will be monitored thereby providing a more reliable comparison with the "solar" building. Cost of the active solar
system - 760 000 FF.

Call for proposal

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Coordinator

SEMIB
EU contribution
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Address
RUE MAURICE RAVEL 15
33520 BRUGES
France

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Total cost
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