Solar PV Battery Storage – A Case Study.

Mike Bartlett from Winchester shares his thoughts on how he came to install a battery storage system.

We have had a solar pv system since August 2011. We were able to get on the original FIT tariffs which were pretty generous although the kit was expensive back then.

Our solar PV system paid for itself after just 7 years. For the last couple of years I had been interested in battery storage. The original setups with lead acid batteries did not really appeal to me as there seemed to be a lot of space needed, a lot of weight and significant maintenance, not to mention the possibility of fumes. In addition the amount of storage that could be used seemed limited by small DoD (depth of discharge) needed to preserve the batteries.

At the early stages lithium battery storage seemed too expensive and they also seemed a bit sensitive in terms of management and usage to get a reasonable number of cycles / life. Recently however the cost of lithium batteries seemed to have dropped and many of the technical issues were removed by intelligent, modular storage systems.

• The Pylontech battery range seemed to address all the life and management issues and had a good warranty.
• At the same time charge controller technology became simpler to implement and integrate with the batteries.
• Lastly the costs have recently reduced to the point where my interest became serious.

It is hard to cost justify battery storage in its own right, let’s be honest, it is expensive. If you just want the battery storage to pay for itself by using the spare solar export, this can be difficult. However, you may also want to add in the TOU (time of use tariffs such as Agile Octopus from Octopus Energy) to store energy when it is cheap (typically overnight) and use it at expensive times (typically early evening).

The addition of this TOU helps in the cost justification and for me was enough to explore further. The lightbulb moment for me was when I looked at it as part of an overall solar pv and battery storage package. As my solar pv system had paid for itself and continued to provide a return, I added in the cost of the battery storage and looked at the costs and returns overall for the complete setup. At this moment it became a fully viable option so I decided to proceed. A “no brainer” as they say.

I also have to confess that I like the technical side and the challenge of getting the best out of the systems. For many it will be the ambition of increasing the use of renewables and reducing their carbon footprint. For others it will be the challenge of reducing the import from the grid to as near zero as possible and believe me, it is just about possible.

Having decided to proceed I contacted The Solar People to get options and costs. I spoke to Andy who some provided some options at competitive prices for an installed system comprising a Luxpower LX3600ACS Inverter/charger and 3 x 2.4kWh Pylontech batteries. This was installed in early May and so far is performing seamlessly and well.

Andy advised to start small as I could always add another battery once I had collated some data. This I did and I now have 4 batteries for a total 9.6Kwh capacity.

The next step is to start to look at the TOU tariffs and time shifting the charging and loads. I will update as time goes on.

One month of live data