No longer the preserve of the alternative lifestyle seeker, renewable energy sources are gaining popularity throughout the country from ordinary home s to commercial buildings. Juliet Davies reports.

SOLAR, wind and ground source energy are entirely renewable and produce no exhaust pollutants in their consumption. Many products are available to install at early construction stage or can be retrofitted to reduce your property’s carbon footprint, and can give homes the power to reduce and produce energy.

Jane O’Brien, the Sustainable Energy Development Manager of Cheshire’s Energy Projects Plus, maintains that although renewable energy is a huge consideration in cutting greenhouse gases, most people do not address insulation sufficiently. “A poorly insulated building is almost impossible to control in terms of heat loss,” she says. “It is one way of really keeping your fuel use down.
Firstly, look at the standard of build, with renewables as the secondary environmental option.”

New and renewable
Renewable alternative energy has a wide remit of products available, giving the property owner the option of, over time, becoming “pound neutral”, as well as, carbonneutral.
Solar Photovoltaics (PV) convert solar radiation into electricity. A 1kw system will provide approximately 30% of an average household’s electricity requirements, and covers around 8m2 of roof surface. If the look of the panels is considered off-putting, PV can be integrated into roof tiles, slates or shingles. With a life expectancy upward of 50 years, it is a low maintenance option.

In the UK, monocrystalline, polycrystalline, amorphous (thin-film) and hybrid are the main types available.

The protective coating is transparent, through which light enters. Two layers of silicone, one positively charged, and one negatively charged, create a flow of electrons resulting in an electric current. As a PV system produces direct current (DC), an inverter is required to convert this to AC as commonly used in the UK.

A photovoltaic panel can produce 20% of its maximum output, even on very overcast days, and can contribute to the running of any electrically powered good in the property. Solar thermal systems work by pre-heating water, thereby reducing the power needed to bring it up to the required temperature. Flatplate collectors contain copper or aluminium tubing behind a glazed absorber plate, whilst evacuated tube collectors have parallel rows of transparent glass tubes containing a vacuum-insulated solar absorber. Within the tubes, sealed liquid is circulated from the collectors to the water tank, transferring the heat.

Combi boilers are not compatible with this system, as the warmed water needs a tank. Planning permission is not usually required for domestic solar panels, if the silhouette of the building is not changed.

O’Brien says, “If you have a southerly aspect on which to fit panels, solar water heating is probably one of the most costeffective ways to use an alternative energy source.”

Going underground
In the UK the ground below the frost line is a fairly constant average between 10OC and 12OC. Working on a thermal transfer principle, the fluid in geothermal ground collectors circulates via a ground source heat pump, in to the property, contributing heat to under-floor heating systems and household water.

Below-ground pipework can be sunk in a borehole, on in a trench as a straight or spiral (“coiled” or “slinky”) horizontal. Boreholes from 15m to 100m deep are more expensive than a horizontally laid system, but require less land. To supply approximately 1kW of energy, 10 metres of spiral would need to be laid, while the vertically installed borehole pipe makes greater use of the higher temperatures found at depth.

Within the heat pump are four main parts:
An evaporator, a compressor, a condenser and an expansion valve. Reversing the principles of a fridge, the contained fluid is converted to a gas by evaporation, which is then heated by compression. As the household heating system absorbs the heat, it cools, reverts back to a liquid, and is recirculated.

A “monovalent” system relies solely on the heat pump itself, whilst a “bivalent” system includes an additional heater, such as an immersion, for top-up, necessary in very cold weather.

A 50-year life span can be expected forthe ground loop, and around 20 for the heat pump.

Although the ground source heat pump that draws the fluid from the ground loop circuit requires power, it is claimed that for every unit of electricity used, they can generate four or five units. If this power is supplied from your own renewable energy system, PV or wind turbine, the pump could be considered fully sustainable. Benefits also include no fuel storage, no exhaust flue, and a home free of combustion gases.

Going greener
Possibly the simplest way for the home or business owner to convert to renewable energy would be to change their electricity supply to a “green” tariff, whereby for every unit used, the supplying company pledges to buy a corresponding amount from renewable sources, as electricity produced from coal, oil or gas releases 0.5kg of carbon dioxide per 1kw used.

But supply companies have a government Renewables Obligation (RO) to provide 5% renewable energy – some use their “green” tariff to meet this, meaning that whilst those who sign for the scheme buy the feel-good factor, those on a “standard” tariff receive less renewable energy than they otherwise would through this legislation.

Wind farms across the country are extending and increasing in number. Scottish Power is expanding its production of wind power, including Whitelee Wind Farm near Glasgow which is projected to have a capacity of 322 MW from its 140 turbines, sufficient for approximately 200,000 homes.

But the private domestic wind turbine is the most visible way of showing your green credentials.

A horizontal turbine with its main rotor and generator at the top of a tall shaft, can rotate with the winds; the vertical turbine has its rotor shaft fixed vertically, making it somewhat less efficient. Both require secure fixing to firm foundations. Building-mounted turbines, although quicker and easier to install, will increase loadings and vibrations, and may have a detrimental effect on some structures.
Calculated at a wind speed of 5m/s recommended turbine sizes would be, for an average household, 2.5kW, which produces 4,282kWh a year. A 15kW turbine for a commercial building produces 29,054kWh a year.

Turbines have a life of between 20 and 30 years, and require servicing at 24-month intervals. Connected to the National Grid, a wind turbine can supply excess output back in to the system during periods of high winds, allowing you to draw energy at calmer periods without losing power or your green status.

Commenting on the installation costs of many alternative energy sources, O’Brien points out: “The ‘pay-back’ period of any energy source is very important. Although costs are falling with their increase in popularity, it is worth the individual property owner being aware that the renewables market is changing all the time.”

An end to fuel poverty?
Housing associations vary in their decisions to include sustainable energy in to their designs. O’Brien explains: “Some are very enthusiastic, with fuel poverty being a big issue, and any way of reducing tenants’ energy bills is a big benefit. Unfortunately it is very much a piecemeal approach and it is down to individual planning officers. We organise workshops to explain how to comply with new legislation, and the Decent Home Standard also brings this issue to the forefront.”

To reach the UK target of cutting carbon dioxide emissions by 60% by 2050, one of the influences on new builds will be the government’s Renewables Obligation, aiming for 10% of the UK’s electricity to come from renewable energy by 2010 and 20% by 2020. The Community Renewables Initiative will encourage local production schemes to get off the ground.

“New property developers tend to treat homes powered by renewable energy as a niche market, and currently, only bring in alternative sources as an option,” O’Brien says, “but with both the
Building Research Establishment and the Department for Environment, Food and Rural Affairs pushing for a stronger sustainability approach, they need to start looking into it more seriously. “Although we work with many architects, requests for sustainable energy sources tend to be customer driven.”

It is estimated that between 70,000 and 120,000 extra new homes need to be built each year in the UK to cope with demand. The impact on emission reduction if these renewable schemes were fully adopted in each development would be phenomenal.

To embrace off-grid living, is the homeowner willing, in effect, to pay up-front for up to the next decade’s power? And should the new-home buyer be given no option, with their alternative power supply being built-in as standard? We await the verdict.

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