Frequently Asked Questions I
Solar Water Heating
1) How do Solar Thermal Collectors work?
They absorb the energy in sunlight and use it to heat water. They do not produce electricity; for this purpose solar photovoltaic panels are used.
2) Is my roof suitable to mount a collector?
Provided that it is structurally sound, any sloping roof facing between SE and SW and inclined at 30-50 degrees to the horizontal is suitable in principle. East-West roofs can also be accommodated with two panels and a slightly more elaborate control system. A collector can also be mounted on a flat roof or on ground without shade by the use of an inclined stand.
3) Can a solar hot water system satisfy all of my daily hot water demands?
This is not possible in Northern Europe where solar systems are used to complement conventional systems. The usual design aim is to satisfy the demand almost completely in the summer months and by up to 55% when averaged over the whole year.
4) Will I need to replace my (vented) hot water cylinder?
For maximum frost resistance we recommend some form of indirect system. With an indirect system you usually need a twin-coil cylinder or a separate cylinder to hold the pre-heated water. However, if you use a device such as a solar siphon, you can still make use of your original cylinder.
5) What other additional equipment is required to form a solar system?
As a minimum, with a direct system you require a circulation pump and an electronic controller that also doubles as a freeze protection device. An indirect system requires some other additional inexpensive components, as described in detail by the installer manual that may be downloaded from the technical files.
6) Are solar hot water systems freeze resistant?
Evacuated tube heat pipe collectors are naturally freeze resistant. With an electronic controller with a freeze protection function even a directly connected system will withstand periods of moderate frost, such as are usual in most parts of the UK. There are various ways of constructing systems that are resistant to periods of prolonged severe frost. Indirect (closed loop) systems usually contain a solar grade antifreeze solution.
7) Can a solar hot water system be used with a combination boiler?
Renewable energy devices usually require an energy store, hence the need for some form of hot water tank. Older “combi” boilers would need to be replaced, but newer types may accept pre-heated water.
8) Can solar water heaters be used for space heating?
This is not normally feasible as there is insufficient solar radiation in the winter months. Arrays of solar water heaters can be used for larger buildings and projects such as swimming pools.
9) Will the solar collector heat water on a cloudy day?
During the summer months in the UK roughly 50% of the solar radiation is direct beam and 50% is diffuse, meaning radiation scattered from the sky and clouds. Therefore an overcast sky will still provide some heating, but how much will depend of course on the thickness of the cloud cover.
10) Is planning permission required for a domestic roof mounted solar water heater?
Planning permission is not normally required in the UK. It is advisable to check to find out if any special local regulations apply.
11) Are solar water heaters suitable for a DIY installation?
Basic plumbing and electrical skills are all that is required for a successful installation. Our collectors are sold with a comprehensive installer instruction manual.
12) What is the expected payback time for a solar water heater installation?
If an electric immersion heater has been used it is possible to recover the cost of a simple self installed system within five years.
13) How long will the solar collector last and what maintenance is required?
Our products have an expected working life of up to 25 years with a minimum of maintenance. We recommend that the heat pipes be replaced after 10 years of service.
14) Will the collector continue to function if one of the vacuum tubes is broken?
In the unlikely event of a broken tube the collector will continue to operate, but with slightly reduced efficiency. The vacuum tubes are non-leaking and replaceable without the need to interrupt the plumbing. A replacement tube can be purchased at very modest cost.
15) Has the collector been tested and does it conform to the relevant standards?
The collector has been performance and quality tested to EN 12975 parts 1 and 2 at one of the leading European laboratories, the Fraunhofer Institute for Solar Energy Systems. It has achieved the European Quality Standard SOLAR KEYMARK.
Domestic Wind Turbines
1) What use can I make of a small wind turbine?
The energy from a small turbine can be stored in a battery bank (and hence, via an inverter, used to power low current, mains voltage electrical devices such as lighting) or stored in the form of heat in a hot water tank. There are some systems that use a controller and grid tie inverter to feed electrical energy into the mains supply, but we consider these to be relatively uneconomic for small turbines (≤ 1kW).
2) How much energy can be expected over the course of a year?
The total energy harvested depends very much on the site. It depends not only upon the mean wind speed but also the variability and the amount of local turbulence at the particular location. As a rough guide, a 1KW rated system should provide more than 1000kWh per year on a site with a mean wind speed of 5.5 m/s.
3) How can the average wind speed be determined for a particular site?
Information about wind speeds can be obtained for any location in the UK by following the link to the British Wind Energy Association online database. As an alternative the Carbon Trust wind power estimator can be used.
4) In What type of location is it appropriate to site a wind turbine?
The ideal location is on a tower as high up as practicable (6-8 m) in an open space away from trees or buildings and exposed to the prevailing wind. A small turbine can be mounted on a high but grounded tower alongside a building of suitable structural strength and held in place by anti-vibration mountings. However higher turbulence will lead to reduced performance and lifespan. Turbines mounted on roofs or gable ends are not generally recommended since the long term effects of vibrations on the building structure are unknown; but there is no hard and fast rule.
5) Is planning permission required for a domestic wind turbine?
At the present time planning permission is still required in most areas of the UK, but it will usually be granted for suitable structures. Temporary structures do not normally require permission and a turbine on a tilt up tower can be regarded as temporary. Many people do not apply for planning permission, or they apply retrospectively if required to do so.
6) Are small wind turbines noisy? Will they interfere with a television signal?
Small wind turbines make a swishing sound as the blades cut through the air but this is often less than the ambient wind noise on trees and buildings. It is of course much less than the ambient noise of machinery and vehicles.
There is usually no problem of interference with television signals. The blades themselves are polymer composite and virtually transparent to electromagnetic waves.
7) What additional equipment is required for a complete wind turbine system?
The turbine is complete with a guyed mast and charge controller as a battery charging system. You will need to purchase the appropriate deep-cycle batteries and an inverter if required.
For the single phase A.C. water heating version the turbine is supplied with an electronic controller and a water heater conversion kit.
8) What is the expected working lifetime? How much maintenance is required?
Under appropriate conditions and with regular maintenance we expect a lifetime of at least 10 years and up to 20 years or more. In other words, we aim to step away from the trend towards complex, high price, low lifetime “junk” products. The user manual will advise on the maintenance schedule and spare parts will be available at an economical price.
9) Is a domestic wind turbine suitable for DIY installation?
Provided that you have the appropriate skills and general constructional and building knowledge, then two people can be expected to install the system in a day. The systems that we provide are not usually connected to the mains, but if you are planning a grid tie system then you should refer to Part P of the Wiring Regulations. This requires a mains connection to be made by a “competent” person.
10) What is the expected payback time for a domestic wind turbine?
Our aim is that savings on electricity costs will give a payback time of 5 years on basic equipment costs in appropriate circumstances. This does not cover the expense of an external installer or any additional equipment.
11) Under what range of environmental conditions will the turbine operate safely?
The systems are compliant with the relevant regulations that require safe operation between at least -10 deg C and +40 deg C and in wind speeds up to 35 m/s. At a wind speed of 15 m/s the mechanical auto-furling system begins to operate and the turbine begins to shut down. For wind speeds up to 15 m/s the turbine rotation is controlled electronically.
12) Has the turbine been tested and does it conform to the relevant standards?
Yes, the turbine conforms to the standards of the UK Microgeneration Certification Scheme and as such was, until recently, eligible for a grant. The current grant situation is in flux and can be found at the site of the Low Carbon Buildings Programme.