Off grid
Isolated homes with no mains electricity supply either have to make do without electricity, or generate their own. For these houses, a renewable electricity generation system - using wind, water or solar power to generate power - could be the answer.
Living with an off-grid system is never like living on the mains, but it can be cheaper than getting a mains connection, and is much cheaper and quieter than running a diesel generator all day and night.
Minimising power use
The first step in setting up an off-grid renewable system is to minimise your electricity use. This is important for all home renewables systems, but if you’re off the grid it's vital. In particular, try to avoid using electricity for high-demand tasks, such as cooking and heating water, that could use another energy source. This will dramatically reduce the cost of your generation system.
Batteries
The heart of most off-grid systems is the battery store. A bank of deep-cycle batteries will store electricity when it is generated, to provide power for when it is needed. With proper controls and system design, a battery bank may last five years or more, but it will not last for ever, so you should budget to replace the batteries several times during the life of a system.
Most deep-cycle batteries are lead-acid batteries, like car batteries but with thick solid plates to cope with the deep charging cycle. Batteries with liquid acid in them require care, as they give off hydrogen gas when charging, and they may lose water over time, which will need replacing. More expensive AGM batteries do not contain liquid, and are much easier to look after.
Batteries can be charged by more than one generation technology: you might have an exposed site with a wind turbine, some photovoltaic panels to provide input during windless spells, and a diesel generator as backup and for running high-power appliances for short periods.
A hydro resource may be reliable enough for you to do without batteries or back-up generator, but this depends very much on the site (and on the needs of the household).
Inverters
Electricity from the batteries can be used directly to run low-voltage lighting and perhaps other direct-current (DC) appliances. However, most systems include an inverter to produce mains voltage alternating current (AC), which can be used to run standard appliances.
The inverter may act as a battery charger, as well as looking after the batteries and controlling the system, or you may have several separate boxes for these different functions.
Feed-In Tariff payments
All renewable electricity generated by an eligible installation can receive payments under the Feed in Tariff for every unit of electricity produced. This is true for off-grid systems as well as on-grid ones – you will get the same generation tariff, though obviously you can’t get export payments.
To qualify for FIT payments, the installer and the generation equipment must be registered under the Microgeneration Certification Scheme. Off-grid systems are complicated, and it is important that they operate safely and effectively, without damaging the generators, batteries and household appliances. We would strongly recommend that you find an MCS installer who is experienced in off-grid installations, and that you ask them to design the complete system.
More information
Find out more about setting up an off-grid renewable electricity system at the Centre for Alternative Technology website.
