Blogs: How battery storage is going to help us fight climate change

22 Nov 2019

More renewable energy on the electricity system creates a demand for battery storage. In our latest blog on Ireland’s electricity system Bobby Smith, IWEA’s senior policy adviser, explains how batteries work, what they do and – perhaps most importantly – what they can’t do.

Battery Energy Storage (BES), already operational in the US, Australia, Germany and Britain, is set to grow rapidly in Ireland as a flexible provider of a range of valuable services to the electricity system.

Most of the Battery Energy Storage systems planned here will use rechargeable lithium ion battery technology. This is actually very similar to the batteries in your smartphone or in an electric car but just much bigger in order to store far larger amounts of electricity.

There are different types of battery-based energy storage systems but these are predominantly at an early development stage so the batteries planned for Ireland in the coming years will very likely be lithium ion based.

Batteries will be essential to manage our electricity system with growing amounts of wind energy but what exactly do they do? Ironically, to clear up a common misunderstanding, it might be easiest to start with what they are not designed to do!

What batteries don’t do

Battery systems generally discharge all their stored energy over 30 mins to two hours before needing to recharge. But there will often be periods with low levels of wind energy lasting many hours, even days, so batteries are not intended to be used to provide power for these longer periods without wind energy.

To get to net-zero emissions by 2050 we will need longer-duration storage that can provide energy over several days when wind generation is low. One potential technology is hydrogen electrolysis, where excess wind energy is converted into zero-emissions hydrogen gas. It is then stored and transported via the existing gas network and used for electricity, heat or transport.

In December, IWEA will be publishing an all-island storage roadmap for policymakers that aims to address the commercial and technical barriers to storage development, including longer-duration storage technologies. 

So if batteries primarily aren’t there to be used for periods when the wind isn’t blowing, why do we need them? There are three main reasons – system stability, cutting electricity prices and supporting the transmission network. We’re going to look at them in turn.

System Stability

The electricity system runs at a stable frequency of 50Hz where supply (electricity generation) and demand are perfectly balanced. If the frequency becomes unbalanced this can destabilise the system and even lead to blackouts.

This can happen if a large fossil fuel generator unexpectedly stops generating or when there is a sudden change in wind generation and the amount of electricity being generated does not match demand.

To protect the electricity system, we use back-up generators that can provide extra power when needed at a moment’s notice, but today these are almost all fossil fuel generators.

This means that fossil fuel generators are often turned on or run inefficiently just so they are available to provide this immediate reserve back up.

But batteries can replace these fossil fuel generators in providing this reserve back up. They are low-carbon, available nearly all the time and can respond to tiny frequency deviations in milliseconds, thus helping to manage system stability. This means we can cut the emissions currently produced by back-up oil, gas or coal generation.

Analysis by energy market specialists Baringa shows that if we replaced the fossil fuel back-up with battery storage we would cut our CO2 emissions by half a million tonnes annually.

By 2030, if we hit our 70 per cent renewable electricity target, we hope to have cut electricity emissions from 12 million tonnes every year to 4-5 million tonnes. So batteries could be saving around 10 per cent of our total power sector emissions by 2030.  

Cutting electricity prices

Electricity demand every day tends to follow the same pattern. Demand is lowest at night but there is a gradual ramp up in the morning as people wake up and get ready for work or school.

There is another fairly steep increase in demand in the early evening as people get home from work, switch on the TV, cook dinner and do the washing. Demand then tails off for the night as people go to bed before the cycle starts again the next morning.

20191122 Blog on batteries

This means peak electricity demand happens at more or less the same time every day, between 5pm and 9pm. Because more power is needed the price of electricity tends to be highest at this time as expensive gas or diesel generators are brought on for just a couple of hours to meet this evening demand.

This is where batteries can step in. They generally charge their batteries when wind generation is high and the price of electricity lowest.

This means they can provide power during the peak demand period for far less than the fossil fuel generators saving money and cutting our CO2 emissions.

Supporting the transmission network

In other countries we are also seeing batteries being used to store and transport electricity to support the electricity network. Wind farms tend to be located away from large electricity demand centres such as Dublin, which means that the transmission network of overhead lines and underground cables is used to get the electricity where it needs to be.

But this can create problems as our transmission grid – which badly needs to be expanded – struggles sometimes to move power from the west coast, where most wind farms are located, to the east coast when there is high electricity demand.

This is another way batteries can help. If they are charged up at times of low demand and are located close to where the power is needed, then they can supply electricity instead of needing to transport it across the island, helping to reduce congestion on the network at times of high demand.

This alleviates the pressure on the transmission network, reduces congestion and can help reduce – but not eliminate – the need to expand the electricity grid.

So how much battery storage do we need?

In October 2018 Baringa released their 70by30 report which projected up to 1,200MW of large-scale battery storage would be needed to meet the 70 per cent renewable electricity target for 2030.

Recently, EirGrid announced that 110MW of low-cost battery storage secured contracts to provide reserve back up and are likely to be operational between 2020/2021. These are short duration half-hour batteries that will help manage system stability with increasing levels of renewables.

Several larger battery storage projects, primarily based in Dublin, also recently won support contracts to help manage electricity supply and are expected to become operational in 2022/23.

The more of these batteries we see connecting to the system the more stable our electricity system, the less CO2 we produce and the lower our electricity prices.