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How easy is it to use renewable energy 'off-grid'?

Posted by David Hunt on 6 May 2011 at 9:38 am

Q: A friend owns a remote property and has been quoted approx £60k to have his 4 bed house connected to the mains network. He was wondering if he would be better off investing in solar panels or wind generation but he needs a constant supply. Will solar panels cope or would he need a generator too. Do you think he would be better off with mains power?

A: Fortunately this is a problem we have recently solved for the owner of a remote island. He was quoted £750,000 for a grid connection. However, as with most questions about renewables, there are many variables to consider.

The simple answer is that yes, you can go 'off-grid' and for the sort of money your friend has been quoted for a grid supply. With the added benefits of receiving feed-in tariffs.

The first thing to establish is how much electricity the home uses. As is ever the case, it is sensible to reduce your energy use wherever you can. Once you know how much you use, you know how much you need to generate. Then you can look at the best way to generate your required amount of electricity.

The island was exceptionally windy, so we installed a 3.2kW Proven Energy P7 wind turbine and a 2kWp Sanyo solar pv array.

However, there are two big issues to consider.
Firstly, batteries. The installation will need a battery back up.  And we are talking big, heavy batteries. You will need to take up a large part of a garage for example. They also require regular maintenance and weekly checks. The amount of batteries will depend on the amount of electricity the home uses.

Batteries will be quite a large part of the overall installation costs, and will usually have a shorter life-span than the solar or wind turbine systems. So they will need replacing.

Secondly, redundancy. There will be times when there are days with little sun or wind. Depending on the electricity usage in the home you could quickly be without any power at all. So you need to build in some over-capacity, in so doing you also need to have a control mechanism to cope if you are generating in excess of your requirements and your batteries are fully charged.

In light of all this it is pretty essential to have another form of electricity generation that isn't dependent on the sun or wind. This would typically be a diesel/kerosene generator.  A control system would then automatically kick in the generator if generation is weak and the batteries are flat.

So, space is another important factor. Do you have the room for a battery bank and a generator?

Wind is very location specific. Do you have a suitable site for wind? Some space for a stand alone wind turbine with a clean flow of air? Planning permission will also be required.
If not, and your home is more urban, then you are probably limited to solar pv and the generator.

So, to conclude: yes, is it possible to be off-grid if you have the right location and space. And yes, it could be done for £60,000-£80,000. Probably!

But, choose your supplier carefully. The control system and integration of the technologies is key. As is the response and warranty arrangement you have with your installer. You don't to be left long without electricity if something goes wrong.

Photo: Proven Energy

About the author: David Hunt was Head of Commercial for Renewable Solutions UK Ltd. He no longer works in the renewable energy sector.

If you have a question about anything in the above blog, please ask it in the comments section below.

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3 comments - read them below or add one


nigelpensarnComment left on: 18 November 2011 at 2:04 pm

I used to run an off grid windpowered system 30 years ago with two small lucas freelights producing only 600 watts each and had a relatively very small bank of lead acid batteries from a telephone exchange. In those days we had no inverters and were wired to 12 volts only. We live 1000 feet up a Welsh mountain and have an average windspeed of 6.7mps. The system worked perfectly except in prolonged windless summer conditions in which case you just sit out and enjoy the sun. Seriously though if you manage your consumption and only use greedy appliances when its windy you dont need a vast array of expensive batteries. We had a capacity of 500 amp hours.

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Cathy Debenham

Cathy DebenhamComment left on: 26 May 2011 at 9:36 am

Yes, you can get the feed-in tariff for an off-grid installation. You will receive the generation tariff, as long as it's installed by an MCS accredited installer. Of course you won't get the (much lower) export tariff.

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GreenMikeComment left on: 26 May 2011 at 9:07 am

Is it correct that you will still receive the feed-in tariff when the installation is off-grid? 

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