No longer the preserve of the alternative lifestyle seeker, renewable energy sources are gaining popularity throughout the country, and for ‘ordinary’ homes and commercial buildings.

 

Solar, wind and groundsource energy is entirely renewable, and produces no exhaust pollutants in its consumption. Many products are available to install at early construction stage or can be retro-fitted to reduce your property’s carbon footprint, and can give homes the power to reduce, and produce, energy.

 

Renewable alternative energy has a wide remit of products available, giving the property owner the option of, over time, becoming pound- as well as carbon- neutral!

 

Solar Photovoltaics (PV) convert solar radiation in to electricity. A 1kw system will provide approximately 30% of an average household’s electricity requirements, and covers around 8m2 of a roof surface. If the look of the panels is considered off-putting, you can also get PV integrated roof tiles, slates or shingles. With a life expectancy of 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 DC (direct current), 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 goods in the property.

 

Solar Thermal Systems work by pre-heating water, thereby reducing the power needed to bring it up to required temperature. Flat Plate 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.

 

In the UK the ground below the frost line is a fairly constant average 10-12oC. Working on a thermal transfer principle, the fluid in Geothermal Ground Collectors circulates via a Groundsource 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 15-100metres deep) are more expensive than a horizontally laid system, but require less land. To supply approximately 1kW of energy, ten metres of spiral would need to be laid, whilst 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 heat is absorbed by the household heating system, it cools, reverts back to a liquid, and is re-circulated.

 

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 fifty year life span can be expected for the ground loop, and around twenty 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.

 

Possibly the simplest way for the home or business owner to convert to renewable energy would be to change their electricity supply to one from 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 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 (airplane ‘propeller’ type), 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 (metres per second), recommended turbine sizes would be, for an average household, 2.5kW (producing 4,282kWh per year), with a 15kW turbine for commercial building use producing 29,054kWh per year.

 

Turbines have a life of around 20-30 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!

 

So, the question is - to embrace off-grid living, are you willing, in effect, to pay up-front for (up to) the next decade’s power?