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Your guide to renewable energy

a lightbulb made out of a plantIn the second of our three-part series aimed at helping you make your home more environmentally friendly, we’ve teamed up with Home Building & Renovating Magazine to look at the alternative energy sources available to UK households. 

Solar Power

Solar panels produce energy from daylight, rather than direct sunlight, so they still produce energy on cloudy or overcast days.

An inverter converts the electricity from direct to alternating current, which can be used in the home. Panels require minimal maintenance and can reduce annual fuel bills quite significantly as well as saving around 325kg/CO2. Exactly where you situate the panels does make a difference and you will have to consider the orientation of the roof and the roof pitch to obtain the best performance. 

Solar Space Heating

Solar Space Heating has to be the most cost-effective system that a self-builder can install. Depending on how cleverly they are designed, houses can use south-, east- and west-facing windows as solar collectors to provide up to 100 per cent of their space-heating needs (if you include heat gains from people and equipment). To avoid over-heating, do not make the windows too large and remember to provide some form of sunshading during the summer when no heat gains are needed. 

Heat Pumps

As the name suggests, heat pumps are designed to pump heat — that is to move heat from one place to another. The key issue is the coefficient of performance (COP), which is a method of rating the heat pump’s efficiency. A COP of four means that for every 1kW of electricity consumed, the heat pump will produce 4kW of heat energy. It runs on electricity so is not renewable energy, but at 4:1 it is very efficient. 

Different types of heat pump 

Water Source: Usually the most efficient, water-source heat pumps draw energy from a body of water such as a stream and often have a COP of five or more. If you have access to running water this system is probably viable; if not, at least one borehole will be needed. 

Ground Source: Heat pumps that use energy drawn from the ground are the most commonly installed machines, with a COP of four quite achievable. A complete system including the heat pump, ground pipes, and controls will cost £5,000-£6,000 on average. Installation will vary with ground conditions, but allow £2,000-£3,000.

Air Source: Those heat pumps that draw energy from the air tend to be the lowest cost. But a COP of 3.5 is about the best that can be expected, falling in winter. 

Wind Turbines

In the UK it is estimated we have 40 per cent of Europe’s total wind energy; but this is still largely untapped and only 0.5 per cent of our electricity requirements are currently generated by wind power.

A wind turbine (without battery storage) can provide highly efficient space or water heating or it can be linked to the national grid, with most of the output being used directly in the home. This allows you to feed the grid and also draw from it when there is insufficient wind.

Wind speed increases with height so it’s best to have the turbine high on a mast or tower. The ideal place to home a turbine is a smooth-top hill with a flat, clear exposure, free from excessive turbulence and obstructions such as large trees. However, small-scale building-integrated wind turbines suitable for urban locations are currently being developed and will be available to install in homes and other buildings within the next few years. 

Water Recycling

There are two forms of water recycling — greywater recycling and rainwater harvesting. Greywater recycling gathers the used water from showers, baths and washbasins and, after treating, reuses it for purposes that do not require drinking-water quality — such as flushing toilets and watering gardens. Rainwater harvesting systems, as the name suggests, gather the rainwater from the roof and use it for non-drinking-water-quality purposes inside or out. 

Most households’ water bills are generally pretty low, so any system costing £2,000 or more is unlikely to produce a satisfactory payback. However, rainwater harvesting schemes are useful in other ways — not least in helping compliance with a local authority’s sustainable drainage system requirement. Both systems save between 30-50 per cent of water usage and can be essential kit for keen gardeners. 

For more information on renewable energy options visit www.homebuilding.co.uk/green .