F.A.Q – Solar Thermal
Q: Can solar water heating provide central heating?
A: No. Unfortunately in the UK it does not make any sense to use a solar water heating system to drive the central heating. In the summer when the sun is warm enough to provide sufficient energy there is no need for central heating, and in the winter when the central heating is switched on, there is nowhere near enough energy from the sun to provide the volume of hot water required by a central heating system. In some European countries it is common practice to install a very large array of solar panels and generate sufficient energy to supply a central heating system. This is because, in countries such as Austria and Germany, although the ambient winter temperatures are cold, the sunlight is still strong enough to provide sufficient energy. However, in the UK the sunlight is much weaker in the winter, partly because of cloud cover and partly because we are further north.
Q: Can I use solar water heating and a wood pellet heating system together?
A: Yes, absolutely. Solar water heating and central heating boilers are a perfect match. In the winter, when the sun does not provide sufficient energy to ensure a supply of hot water, it is no problem for the boiler to take on this demand because it is already running and providing central heating. And in the summer months when the boiler is normally switched off because the central heating is not in use, very often the sun will provide sufficient hot water for your shower, bath, washing machine and dish washing needs.
Q: Can I use my existing boiler with a solar water heating system?
A: Yes, normally they will work together very well. In the winter, when the sun does not provide sufficient energy to ensure a supply of hot water, it is no problem for the boiler to take on this demand because it is already running and providing central heating. And in the summer months when the boiler is normally switched off because the central heating is not in use, very often the sun will provide sufficient hot water for your shower, bath, washing machine and dish washing needs.
Q: I have a combi boiler: can I still use solar water heating?
A: Yes, provided you have sufficient space for a hot water cylinder. The combi boiler itself is normally not a problem, but all solar water heating systems must have a hot water storage tank at least as large as a conventional hot water cylinder.
Q: Do solar panels generate electricity?
A: There are two types of ’solar panels’ and they are based on completely different technologies. Solar Water Heating systems, also known as Solar Thermal systems, supply only hot water. Solar Photovoltaic or Solar PV systems generate only electricity.
We supply the former: solar hot water systems are very cost-effective, efficient, practical and inexpensive compared to solar PV systems – a solar water heating system can pay for itself in financial terms in as little as ten years. They integrate perfectly with our automatic wood pellet heating systems and with many existing heating systems. A solar water heating system is probably the single most practical and worthwhile renewable energy technology for most people in the UK.
Solar PV systems are expensive and complex. As well as the panels themselves, they normally require an inverter system and either a bank of batteries or a connection to the electric grid. A solar PV system will typically cost tens of thousands of pounds and will not repay its installation cost for 30 years or more.
Q: My roof is in the shade or north facing. Can I still use solar water heating?
A: Realistically, no. In order to be both energy- and cost-effective a solar panel must have full sunlight whenever it is available. However, a number of alternatives are available for people who do not have a south-facing roof in direct sunlight. Solar panels can be mounted on an inclined frame attached to an east or west facing roof in order to ensure that the panels themselves face south-east or south-west. If no suitable roof is available at all, panels can be installed on a free standing frame which can be situated adjacent to the building, or even a small distance away from it in order to capture maximum sunlight.
Q: I have heard that evacuated tubes are better than flat plate solar panels. Is this true?
A: There are broadly speaking two types of solar water heating panels: flat plate collectors and evacuated tube collectors. It is often claimed that evacuated tubes are more efficient than flat plates. Whilst it may be true that some poorly designed flat plate systems are worse than evacuated tubes, in our ten years of experience at the Organic Energy company we have found that a properly specified, well-built European flat plate system such as Gasokol is typically more efficient than an evacuated tube-based design. Evacuated tube systems are also inherently more fragile than flat plate systems, being made of very thin glass – a bit like an insulated thermos flask. Unfortunately they completely rely on their evacuated nature to work: any breakage or damage will result in a loss in vacuum will render that tube ineffective. Indeed, some of our installers are now returning to previous evacuated tube installations to replace them with Gasokol flat plate systems.
The level of research and development which goes into solar water heating technology in Austria, both at university and commercial level, is infinitely higher than in the UK. Through working with Gasokol we have found that the efficiency of a solar water heating system depends less on the flat plate versus evacuated tube debate, and much more on factors such as the proper design and sizing of the system relative to the heat load and demand, the level of care and attention paid to the installation, and above all on the build quality of the product itself. Special rust-proof alloy connectors and pipes, the use of all-metal components thoughout, and Gasokol’s special non-ferrous glass which is both highly transmissive of solar radiation and very tough all ensure that this flat plate system is not only as efficient as an evacuated tube system, but in a real world situation is also far more dependable and longer-lived. In fact, we invite customers to stand on the demonstration Gasokol solar panels in Organic Energy’s Welshpool showroom, 4 or 5 people at a time to prove the resilience and strength of the material!