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  • Solar Energy Battery Storage

    Solar Energy Battery Storage

Solar Energy Battery Storage

Battery storage systems allow surplus solar electrical energy to be stored locally and used later rather than being exported to the grid.

Systems all comprise a controller that detects when to store rather than use or export the energy and one or more battery packs. Most systems can be expanded, by adding in more storage, which the controller then manages.

We install battery storage systems as part of a new Solar PV installation or as a Retro-fit to existing Solar PV systems.

Standard installations are usually completed in one day and include hanging the battery – which in the case of the Tesla weighs 100kg!, mounting the controller nearby, setting up the monitoring and linking into the existing / new solar cabling and the house AC.

Batteries are DC devices i.e. they store the energy and deliver it as direct Current rather than Alternating Current (AC) that the electricity grid is based on. The majority of currently available storage systems, such as Tesla’s Powerwall, SMA’s integrated battery systems, Growatt etc. are linked to the DC side of a solar or wind inverter but an AC system is available from Enphase.

If you already have an inverter we will probably have to use that manufacturer’s storage system as they are not yet really cross compatible.  

Tesla, who do not manufacturer inverters have so far integrated with SolarEdge, and will build other alliances.

The returns are currently relatively modest and for a typical domestic property all of them will take longer to pay back than the life of the system. The best returns are around the 20 year mark with the life of the system around 10 years – but pricing is predicted to fall as demand and the installed base grows. 

Savings are based on storing electricity that you would otherwise have exported. So even the above modest returns require that you have either a 3 kW plus Solar PV system or have very low consumption (or both).

It is also worth considering that the battery will introduce losses – they have a typical ‘round-trip’ efficiency of about 85% to you will lose some energy before it is metered for the Feed-in-Tariff (FIT).

So anyone with a pre-April 2012 FIT registered Solar PV system who is now benefitting from effective FIT rates of about 50p per kWh is unlikely to be able to benefit from a DC side battery system.

For those with 3 kW plus Solar PV systems installed after April 2012 the benefits will be better.

At the moment there is only one ‘time-of-use’ electricity tariff in the UK where ‘Economy 7’ allows cheaper power to be used overnight. The AC Enphase system is the only one that could possibly take advantage of this, because the others, on the DC side, have no way to generate DC from the inverters – which only convert DC to AC. At the moment Enphase do not offer a way to charge from the grid, selling it only as an add-on to solar systems, but in principle it can be done as it is only software in their controller.

Get in touch and we’ll be happy to advise you on how a battery storage system could be of benefit to you.

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