Security of electricity supply is one of the main reasons that people install their own solar panels or wind turbine. However, a system that is connected to the national grid currently doesn't afford total control.

The benefit of grid connection is that you can sell any excess you generate to the grid, and import electricity if there's not enough sun or wind to make your own. But, your system is automatically shut down whenever there is a power failure on the grid - which is arguably when you need it most - to protect anyone working on the grid.

Until now, that is. The Centre for Alternative Technology (CAT) has just announced a "ground-breaking way of enabling communities to take control of their energy use". Developed at their site in Machynlleth, Wales, where they generate electricity using wind, hydro and solar PV, they have developed an intelligent control system to connect and disconnect to the grid whenever they need to. Called island generation, it is the first system of its kind in the UK.

If grid power fails, the CAT system will be isolated from the national grid, and can continue generating electricity for immediate use, and to charge the battery bank. The back up batteries mean that even if there is no wind, sun, water or biomass there is power for at least three hours.

CAT will use this island system in its training courses and consultancy as a model for Zero Carbon CAT. It will also be a demonstration project for small communities that are interested in an island grid system.

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