How to store your solar generated electricity to use in the evening
Posted by Chris Rudge on 11 May 2011 at 9:28 am
Q: I have installed solar panels and am amazed at the power I am creating. This is great in sunlight hours - but has anything been produced to store this power so I can use it in the evenings? This is such a waste of free power, surely someone somewhere must have this on board. It's not rocket science!!
A: Storing all that 'free power' is something our customers often bring up. There are a couple of cost-effective of ways to do this:
1) You can consider using the excess generated power to run the immersion heater in your hot water cylinder. This device is usually installed for emergency use if your boiler broke down. However we have put in a couple of units to customers' solar PV inverters that know when the output power goes over 1kW and switches on a relay.
Wired to a standard 3kW immersion heater through one of our power reduction units, the immersion runs at 1kW and gently heats the water. Over a whole sunny day, you will get a full tank of hot water, at other times it will effectively pre-heat your hot water tank so the gas boiler does not have to run for long.
2) Battery backup. This option can be as simple or as complicated (expensive), as your budget & requirements stretch. A couple of our more experimental customers have installed their own twilight changeover systems that charge a large set of renewable energy lead acid batteries during the day, (on the free to use electricity), then at night the lighting circuits in the house switch over to using these batteries through a pure sine inverter. This can be extended to powering other devices in the house as well, and is dependent on your power requirements during the evening.
However, decent batteries cost quite a lot of money and will need maintaining, plus replacing every 5 to 10 years, so is not an option to be taken lightly.
In rural areas, the battery backup option has real advantages that your house will have the option of backup power during power cuts. There are some quite sophisticated systems, such as Sunny Backup units, that do everything automatically, down to simple changeover switches.
There are a number of systems on the market that claim to maintain and manage your renewable power generation, but only batteries or the heating suggestion really do actually 'store' the power for you to use overnight.
Photo by Hepburn Wind
About the author: Chris Rudge is a qualified electrician who specialises in renewable energy.
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