Balancing the grid using energy storage technology increases efficiency and reduces costs
Britain’s transition towards becoming a low-carbon economy is an exciting journey. Over the last two decades, thousands of jobs have been created in a rapidly maturing renewable energy sector. Today, renewable energy installations generate green power for millions of UK households and businesses, whilst costs have fallen dramatically. So far, so good.
However a switch to renewables brings its own challenges. For example, when it’s around noon on a sunny day in the South West and the region’s solar farms are working at full capacity, power generation often exceeds consumers’ needs. A similar imbalance occurs a couple of hours later, when kettles and TVs are put on at night when the sun has set.
With the aim of solving these issues, storage became a buzz word in the energy sector. Following on from the global boom in renewable energy deployment, energy storage technology developed quickly and has now reached commercial viability. One company making headway in this emerging market is storage system developer Green Hedge. Their product Energy Barn (literally a shed filled with lithium ion batteries totalling an installed capacity of 10MW) works as a battery hub which has been designed to help correct grid imbalances. Managing Director Dr Niels Kroninger commented:
“The Energy Barn stores excess electricity off the grid or feeds back into it, whatever is called for. Within a fraction of a second it can start exporting or importing power, stabilising the network frequency. This is a huge step forward in bridging the gaps between supply and demand which have become more common following the sharp increase in renewable energy generation.”
Critics of renewable energy installations such as wind turbines and solar PV have always maintained that due to their variability they cannot be relied on to provide a stable network baseload. Where weather forecasting does play a part, it is generally accepted that coal and nuclear power are better placed to provide the grid’s base load and that gas and smaller scale renewables installations are better suited to deal with spikes in demand.
But coal pollutes, and as they come to the end of their lifetimes, coal fired power stations are being phased out. Nuclear is a very costly option and is controversial because of its perceived safety, stability and waste issues. Although the UK Government have now bitten the bullet and have recently agreed to guarantee the power price for EDF’s Hinkley Point C, public opposition remains strong. Renewables, particularly onshore wind and solar, provide a cheaper solution for the UK bill payer, but can grid issues be fixed?
According to Mr Kroninger, energy storage provides the missing piece of the jigsaw:
“Energy storage has been the missing link. If renewable energy projects such as wind farms and solar parks work together with energy storage systems and backup gas generation, we have a decentralised, low carbon power network that can function at costs much lower than new nuclear. We have calculated that using an adequate combination of renewables, energy storage and backup gas instead of new nuclear would save the UK bill payer £25bn over 35 years, in today’s prices[i].”
Energy storage is popular with the National Grid as it addresses a couple of challenges that the network operators have to deal with. One such challenge is ‘response’: balancing the frequency of the electricity grid in a split second. National Grid forecasts peaks in supply and demand for electricity. If it gets this wrong, for example because of irregularities in renewable energy generation or an unplanned outage of a power plant, any imbalances between demand and generation need to be addressed immediately in order to avoid blackouts. Batteries can respond within a split second, importing or exporting power, whichever is necessary to balance the system.
The other thing batteries are good at is ‘reserve’. Batteries are well suited to deal with over-generation of renewable energy systems, i.e. generation exceeding demand. Storing renewable electricity in batteries can make existing wind farms and solar parks much more efficient as the power that is generated in excess can be stored and used at times of greater demand.
While providing evidence to the Energy and Climate Change Committee, National Grid’s Director of System Operations Phil Sheppard said:
“The types of services we can get are vast, from providing response services in milliseconds, rather than in seconds, to moving peak demand around. If there is a surplus of energy on a bright, sunny bank holiday when there is not a lot of demand, then it is about storing that, and then reinjecting it on the Monday morning when demand peaks. Those sorts of services, from a balancing perspective, including balancing of suppliers, are going to be very valuable to us.”
A Green Hedge Energy Barn comprises a new, steel-framed building with a concrete foundation and measures about 150 x 65ft. It can be made to look like a farm shed, but also comes as a container which may be more appropriate for industrial settings. The Barn contains inverters which convert the electricity from AC to DC, in which it is stored, and DC back to AC. The air conditioning units keep the inside temperature at 23 degrees Celsius and a transformer is used to bring the voltage up to the grid level of 33kV. A small substation houses the switchgear for its grid network connection. With a lifespan of 25 years, the Energy Barn is a straightforward affair and it is likely that there will be many installed over the next couple of years.
Mr Kroninger added:
“The UK is lagging behind in energy storage deployment. Other advanced economies such as Japan, South Korea, Germany and the US have already implemented high numbers of energy storage systems. But as battery cost is coming down and the UK energy sector is similar to the ones in these countries, I am certain that solutions such as our Energy Barn will be commonplace in the foreseeable future.”
[i] Hinkley Point through the looking glass, Lebrun, Stone & Kroninger, April 2016