Storing the rays from rooftop solar

Sensemaking / Storing the rays from rooftop solar

A battery system to store energy from photovoltaics reaches UK domestic market after success in Germany.

By Jon Turney / 03 Apr 2013

A battery system to store energy from photovoltaics reaches UK domestic market after success in Germany.

Solar PV systems can make electricity on your roof, but not necessarily when you want it. The mismatch can be fixed by selling any surplus via the grid, and taking power back when you need it. This isn’t great for homeowners weighing up an investment in solar panels. Feed-in tariffs can change, and future energy bills are hard to estimate.

One answer is to store electricity on site, an option that has been open to German enthusiasts for domestic PV for a while. Now it is coming to market in the UK, with the first system tailored to the single phase electricity supply used in this country.

SunBat, on offer from SolarENLES Ltd, monitors power production and use, and diverts excess solar electricity to battery storage. It can store 9.6kWh with a lead-gel battery, and nearly 16kWh with a costlier lithium-ion battery. The company reckons this will allow an average home user to take the share of their electricity coming from a solar installation up to 75%.

Will this encourage more people to take the plunge and put panels up on the roof? The upfront costs may still be a problem, for now. This kind of storage can only even out daily, not seasonal, fluctuations in solar input; users will still be drawing on the grid more heavily in the winter, thus limiting their savings over the year.

The higher capacity of the lithium-ion batteries give them the edge. Similar batteries for use in cars currently cost £300 per kWh, putting the price of a 16kWh unit at nearly £5,000. That, with the control systems needed, is a pretty big addition to a solar PV installation, which typically comes in at under £10,000.

However, analysts at McKinsey forecast that lithium ion costs will drop by more than half within a decade, so the sums may soon be more clearly in favour of home storage. – Jon Turney

Photo: iStockphoto / thinkstock

What might the implications of this be? What related articles have you seen?

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