GMCR currently offers schools and community centres hosting our panels clean electricity at a discounted rate compared to their main supplier.

When the solar array is generating, the school has first call on the solar electricity, but if they don’t need electricity at that moment, the electricity is exported and GMCR sells it to an energy company at a lower price.

Installing a battery would mean that we could save some of the electricity being generated when the school didn’t need it so they could use it later. And if the school uses more solar electricity, it would mean GMCR’s income increases and the school’s electricity bill reduces. Win win!

So, we applied for a grant from the Government’s Community Energy Fund to explore the feasibility of installing batteries at our solar sites and to learn how to assess this ourselves for potential new sites.

We selected a range of our existing solar sites to assess, especially those in our portfolio with lower onsite usage, who we thought would benefit the most from a battery. We engaged Red Co-op to tell us if batteries would be viable (from both a financial and environmental perspective) at these selected sites and help us build battery storage into our site viability assessment tool.

What did we find out?
Unfortunately, the report concludes that:
– It is not financially viable to install community-owned batteries at the selected sites UNLESS battery prices fall.
– The main reason the installation of a battery does not provide a significant improvement is that the timing of the solar electricity generation is already quite well matched to the time when the electricity is needed (i.e. during the daytime).
– If the schools paid for the battery themselves, the payback periods would be 8-15 years. This needs to be considered in the context of the lifespan of a battery, which we understand is around 15 years.

The report provides the outcome of the feasibility assessments for each site, and how this has been built into GMCR’s site viability model. It starts by taking hypothetical scenarios as if each site was buying a brand new solar array and battery with its own funds and then applies GMCR’s model afterwards.

What’s the carbon impact of batteries?
The carbon intensity of electricity from the grid varies throughout the day, depending on the weather and the level of demand. For example, more electricity is needed from fossil fuel power stations during the evening peak than at night when demand is relatively low.

Batteries can help to reduce carbon emissions by shifting demand, for example by storing solar electricity during the day and using it in the evening. The report estimates that a 100 kWh battery at one of our sites could save up to 2 tonnes of carbon emissions per year.

However, there is also a substantial amount of embodied carbon from the manufacture of batteries. For example, a 100 kWh battery with a 15-year life could have a carbon footprint of between 5-50 tonnes, depending on production, processing and the raw materials used.

So if we did install batteries in the future, we’d have to be careful about how we procure them if we want to deliver carbon savings as well as financial benefits.

What did we conclude?
From GMCR’s perspective, we learned that assessing the viability of batteries at sites is much more complex than a solar PV site viability assessment. We hoped there would be some trends or rough estimates we could use to assess whether to install batteries at future sites, but we learned that each site has to be modelled in detail individually in order to generate the inputs needed for our model. Thanks to the work from Red Co-op, we have a comprehensive spreadsheet to use for this now (and instructions!)

We will keep both the financial and environmental sustainability in mind in future when deciding whether to invest in batteries, should prices come down.