Renewable Energy Technologies

What could be better than knowing that the energy you use in your home is simply the by-product of the earth's own natural forces? Renewable energy, such as solar and wind power, can be used without depleting natural resources and with minimal pollution.

And better still, if you produce excess energy you can sell it back to the national grid, saving you even more money.

There are several different kinds of microgeneration (energy created on a bite-sized basis), some better for domestic use than others. But, whatever gives you a buzz, it's usually best to get it installed by professionals - and do be realistic about its energy output. In some cases you'll be looking at 20 years plus to recoup your costs. Also, check out any building restrictions and rules with your local authority, and while you're at it, ask them (or your power suppliers) about any grants available.

HERE COMES THE SUN

There are basically two kinds of solar power: solar water heating system, which simply heats a tank of water; and solar photovoltaic (PV), which uses sunlight to create electricity to run appliances and lighting.

The easiest for most householders is a solar water heating system, which is very low maintenance and can provide about half of your domestic hot water needs over the year. You'll need a back-up system in the winter, though, probably from your existing central heating boiler.

Roof-mounted solar panels collect heat from the sun's radiation; this heat is transferred into a hot water system, which is stored in a tank. The system you end up with depends on factors such as the area of south facing roof, the existing water heating system and, of course, your budget.

Solar photovoltaic (PV) requires only daylight - not direct sunlight - to generate electricity, and uses cells made of a semi-conducting material, usually silicon, to convert solar radiation into electricity. PV systems generate no greenhouse gases and can be used on any building with a strong enough roof or wall that faces within 90 degrees of south, as long as no other buildings or large trees overshadow it. Prices for PV systems vary, depending on the size of the system to be installed, the type of PV cell used and the nature of the building which houses the PV. The more juice you want, the bigger the system.

MICRO WIND TURBINES

There has been a lot of hype around micro wind turbines, although the idea is straightforward enough: they use the wind's forces to spin aerodynamic blades that turn a rotor to create electricity. But to generate plentiful power and recoup your costs they need to sit in a consistently windy spot, preferably in a remote rural area with no buildings or trees nearby that might interfere with the wind force.

To determine your home's potential you would ideally assess the speed and direction of the wind over a period, perhaps up to a year. Not something to be undertaken lightly! Planning issues such as visual impact, noise and conservation rules also have to be considered.

SMALL SCALE HYDRO

Using the flow of water around a turbine (water wheel) to generate energy is probably the oldest form of renewable energy. Hydropower produces no waste products during operation and once up and running it's free. Suitable sites include mountainous spots where there are fast-fl owing streams, and lowland areas with wide rivers. Small hydro systems can supply electricity directly to the homes or can be used to charge batteries or as a back up to a diesel generator.

GROUND SOURCE HEAT PUMPS

Ground source heat pumps (GSHPs) make use of energy stored in the earth through a series of pumps and pipes. The only energy used by GSHP systems is electricity for the pumps, but this should easily be outweighed by the thermal energy or heat generated. GSHP systems can be pricey to install but they have very low maintenance costs and should last at least 20 years. They work best with heating systems designed to run at a lower water temperatures, for example, underfloor heating.


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