What is a solar thermal roof?
A solar thermal roof, also called an energy roof, is a roof with pipes in or directly beneath the top layer of roof covering, through which a fluid circulates to collect heat from the sun. That heat usually goes to a heat pump, which turns it into hot water or space heating. In effect, the whole roof works as a large, invisible solar collector.
How does it work?
- Sun and outside air warm up the roof covering.
- A mixture of water and antifreeze in the pipes absorbs that heat.
- A pump carries the fluid to a heat pump, a buffer tank or ground storage.
- In summer the system can extract and store surplus heat, so that it is available as a source in winter.
Because a heat pump also works with low source temperatures, the roof still delivers usable energy on cloudy days, although the yield is lower.
Advantages
- No separate panels or collectors on the roof, so the roof keeps a calm appearance.
- Suitable as a heat source for a heat pump or for heating a swimming pool.
- Can help keep the heat and cold balance of ground storage in check.
Disadvantages and points to watch
- Cost: a solar thermal roof is usually more expensive than ordinary roof covering with separate solar collectors. Always ask for a comparative quote.
- Design from the start: standard dimensions are often needed, so the roof has to be designed around the system.
- Heat only: unlike solar panels, it does not generate electricity. PVT panels, which combine both, do exist.
- Watertight and frost-proof: the pipes must not freeze or leak inside the roof build-up. The system needs topping up with water and antifreeze from time to time.
- Maintenance and repairs: anyone working on the roof covering must know where the pipes run.
Related terms
- Flat roof
- Roof Covering
- Ground Heat Exchanger
- Ground Source Energy
- Home battery
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