Storage system for domestic solar electricity launched
Posted by Cathy Debenham on 16 October 2012 at 9:48 am
With a large discrepancy between the cost of buying and selling electricity, the owners of domestic solar PV systems are always asking how they can use more of it on site. So it was exciting to speak with the inventors of the first fully integrated storage system for domestic Solar PV at Solar Power UK earlier this month.
SunBat stores electricity when it is produced during the day, and allows homeowners to use it when the sun isn't shining. The makers estimate that it will enable domestic users to meet around 75% or their electrical needs from solar PV.
The system comes in a range of storage capacities from 9.6kWh to 15.8kWh. It has a 6kW inverter which means that it can cope with high demand when running on battery mode. For example, if you have the oven, TV and lights on in the evening, you will still be able to boil a kettle.
The idea is not new. Systems like this have been available in Germany for some time. However, there domestic electricity supply is 3-phase, whereas here it's single phase. SunBat is the first single phase system.
The SunBat will also act as a standby power unit if there is a power cut. This is useful because solar panels automatically shut down when there is a power cut, to ensure the safety of people working on the lines.
The system has an intelligent energy management controller, which lets users control how their stored energy is used, by giving priority to different appliances (for example you could prioritise the immersion). Users can monitor it through a web server. If there is a power cut, these priorities are over-ridden, and the power goes to whatever needs it.
The SunBat comes with a choice of batteries. Standard is a 9.6kW lead-gel battery. This can be discharged to 50%, which means there is up to 4.5kW of energy to use in the evenings. There also is an option to have a more expensive lithium-ion battery. This can be discharged to 70-75% making 6kW of power available for evening use. It also lasts significantly longer. The controller also manages the charging cycles to prolong battery life.
I was interested to hear that in Germany the more expensive lithium-ion battery is fitted as standard, with the cheaper alternative as an option. An interesting illustration of our focus on price in the short term, rather than value over the long term, perhaps.
The SunBat can be fitted to new and existing solar PV installations. As it was only launched at the beginning of the month it's not clear yet what price it will be marketed at. The SunBat stall at Solar Power UK was constantly busy over the three days, and if all the interest turns into demand, the manufacturers hope that they will be able to produce them more economically. Watch this space.
More information about solar electricity from YouGenCathy Debenham
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