Here we give you a description of how renewable energy products work. It is not a definitive guide as this would be to in depth and long winded, so what we have here is the lay mans version, which should we hope give you enough information to help you on your way to produce renewable and green energy. In doing so you will help to reduce the amount of green house gases produced every year.


Solar photovoltaic (PV) modules

Use energy from the sun to create electricity to run small appliances and lighting circuits. PV modules only require daylight - not direct sunlight - to generate electricity. Photovoltaic systems use cells to convert solar radiation into electricity. The PV cell consists of one or two very thin layers of a semi conducting material, usually silicon. When light shines on the cell it creates an electric field across the layers, thus causing electricity to flow. The greater the intensity of the light, the greater the flow of electricity. (All PV modules generate DC electricity and are fitted with a blocking diode to prevent battery discharge)

PV systems generate no greenhouse gases, saving approximately 325kg of carbon dioxide emissions per year - for each kilowatt peak of energy they generate in full sun light, therefor a typical 5 kilowatt PV array will save around 1.6 tonnes of carbon dioxide per year.

You can install PV modules on a roof, wall or create a PV array in your garden as long as it faces not more than 90 degrees of south. You should also consider if the location is free from shadows (remember that the angle of the sun changes from winter to summer, this should be also considered.) as this will reduce the output from the PV modules,

Solar panels are not light and the roof must be strong enough to take their weight, especially if the panel is placed on top of existing tiles. Prices for PV systems vary, depending on the size of the system to be installed, type of PV cell used and the nature of the actual building on which the PV is mounted. The size of the system is dictated by the amount of electricity required.

Grid connected systems require very little maintenance, generally limited to ensuring that the panels are kept relatively clean and that shade from trees has not become a problem. The wiring and components of the system should however be checked regularly by a qualified technician. Stand-alone systems, i.e. those not connected to the grid, need maintenance on other system components, such as battery packs.

Some local authorities require planning permission to allow you to fit a PV system, especially in conservation areas or on listed buildings. Always check with your local authority FIRST about planning issues before you have a system installed. Obtaining retrospective planning permission can be difficult and costly

Modern wind turbines

Use the wind's lift forces to turn aerodynamic blades which are connected to a rotor (normally high grade permanent magnets) which creates electricity. In the UK we have around 40% of all Europe's total wind energy, but it's still an untapped source and only around 0.5% of our electricity requirements are currently generated by wind power.

Our turbines vary in size and power output, from a few hundred watts to two or three megawatts (as a guide, a typical domestic system would be 2.5 - 6 kilowatts, depending on your life style and size of the home). Typical uses range from very small turbines supplying energy for battery charging systems (e.g. on boats, sheds, outbuildings or in homes), to turbines grouped together on wind farms supplying electricity to the grid.

Wind speed increases with height so it's best to have the turbine high on a mast or tower. Generally speaking the ideal siting is a smooth-top hill with a flat, clear exposure, free from excessive turbulence and obstructions such as large trees, houses or other buildings. Wind power is proportional to the cube of the wind's speed, so relatively minor increases in speed result in large changes in potential output, and with low start up or cut in wind speeds, generating electricity is possible on almost calm days.

However, small-scale building-integrated wind turbines suitable for urban locations are currently available and new systems are being constantly developed which will be more attractive for homes and other buildings. Knowledge of the local wind is critical to designing a wind energy system and predicting output. For domestic installations a good source of information on local wind speeds is the NOABL database which can be accessed from the British Wind Energy Association.

Stand-alone or grid-connected system?

Small-scale wind power is particularly suitable for remote off-grid locations where conventional methods of supply are expensive or impractical. Most small wind turbines generate direct current (DC) electricity. Off-grid systems require battery storage and an inverter to convert DC electricity to AC (alternating current - mains electricity). You can also use a controller to divert power to another useful source (e.g. space and/or water heaters) when the battery is fully charged.

Wind systems can also be installed where there is a grid connection. A special inverter and controller converts DC electricity to AC at a quality and standard acceptable to the grid. No battery storage is required. Any unused or excess electricity can be exported to the grid and sold to the local electricity supply company. (A great idea when you are not at home or away on holiday)

Planning permission
Planning issues such as visual impact, noise and conservation issues also have to be considered. System installation normally requires permission from the local authority. Obtaining retrospective planning permission can be difficult and costly.

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