Solar Water Systems
Frequently Asked Questions
Why Solar Hot Water?
The energy requirements of the world are escalating, so energy costs are rising as demand increases. More fossil fuels are needed to provide this energy. This causes more pollution.
By using solar energy to heat our water, we are using the only truly clean fuel and it is totally free. On average, every square metre of the British Isles receives 1000kWh of solar energy each year. The average household requires approximately 300kWh of energy to heat its hot water annually.
Vacuum tube collectors
As solar technology has advanced during recent year, vacuum tubes have come to replace the older flat plate collectors. The problem with the flat plate collectors is that they make extremely good radiators, so in the winter months they are very inefficient. Vacuum tube collectors are less affected by wind or cold temperatures and work well in N. Europe.
Vacuum tube collectors still absorb solar energy in winter months and help to heat the water. In the summer, they can supply sufficient hot water for the household for months on end, without the need for the conventional water heating from the boiler or immersion heater.
How do vacuum tubes work?
A vacuum tube collector consists of an insulated copper header pipe through which water flows. Into this are fitted the vacuum tubes themselves.
The vacuum tube is a glass (Pyrex) twin walled tube with a vacuum between the walls. In the centre of this is the heat transfer element, which absorbs the solar energy and transfers it as heat to the header pipe.
There is no water in the tubes only in the header pipe. Once fitted, the tubes are not fragile as they are securely fixed at both ends. So in the rare event of a breakage, the system operates as normal. Any or all of the tubes can be removed and replaced whilst the system is in operation.
How heavy are the collectors?
A 20 tube collector panel is just 48kg. When you consider this is spread over 2.2 square metres of your roof, the loading is perfectly acceptable.
How big a system would I need?
This depends upon the size of your household and your hot water demand. A 20 tube panel delivers up to 7 kWh daily and is required for hot water cylinder up to 175 litres. A 30 tube panel delivers about 11kWh daily and is used for cylinder between 175 and 260 litres. For larger capacity cylinders, a combination of 20 and 30 tube panels can be linked together easily.
Do I need to change my hot water cylinder?
We recommend the replacement of existing hot water cylinders with twin coil cylinders, designed specifically for solar hot water installations. They are fitted with 50mm of moulded on insulation compared to the 25mm of insulation (or even a poorly insulating cylinder jacket).
However, it is possible to fit a small secondary heating coil to an existing cylinder in place of the immersion heater element. They are much less efficient than a twin coil cylinder installation, but do offer a low budget option.
Can I use it for my central heating?
Unfortunately not. The problem is that in the winter, when we want the heating, the solar energy is at its lowest. So the energy collected is very low, definitely not enough to warm a house.
Can I use solar heating with a combi-boiler?
Combi boilers use cold water, while solar systems use hot water, so most combi boilers are not suitable for solar water heating. There are new combi boilers appearing, however, which could be suitable for a solar heating system.
Where can I fit the collector?
The collectors can be fitted to a pitch or flat roof even to a vertical wall. They should be site facing south, but in reality, they can face anywhere between south-east and south-west. If restricted to an East-West location, then two panels would need to be fitted, one facing east, the other west. A special controller is required to operate this system.
Can I DIY fit this system?
Yes you can, provided you have the necessary plumbing and electrical skills. Many companies can supply a kit of the major components as well as providing advice and assistance with any installation problems. You will need to supply your own copper pipe and fittings to most kits.
Due to the high temperatures involved in the solar circuit, copper pipe with soldered or compression fittings must be used. Push fit fittings with plastic pipe are totally unsuitable.
Do I need planning approval?
Not normally. However it is advisable to contact your local council Planning Department to verify this. You may require Building Regulations approval, so again it is advisable to contact your council regarding this.
