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Alternative Energy | Storage

Cropped battery interior (uk power networks)

The latest capacity market auction has generated some exciting news. While that may sound like an oxymoron, in this case it is justified as it marks a milestone for new storage technology.

The capacity market is designed to ensure that electricity is available during times of high demand – for example during the winter months.

It allows the government to buy capacity in advance, making sure we have enough electricity infrastructure to cope with peaks in demand.

The capacity market has its flaws and has been criticised because of the number of diesel powered projects bidding for contracts.

Cropped gigafactory (tesla)

Cropped gigafactory (tesla)

Giga factory storage facility in the Nevada desert

But December’s auction resulted in the award of the first ever contracts to battery storage projects, showing that energy storage technology is breaking into the mainstream.

So why has storage become such an important issue?

As traditional thermal generation plants – such as high carbon coal-powered stations – come off the grid, they are being replaced by renewable technologies including solar photovoltaic and onshore and offshore wind farms.

Renewables uncertainty

While this is good for the government’s aim of achieving a 34% reduction in carbon emissions by 2020 (based on 1990 levels), the intermittent capacity of these renewables means that a level of uncertainty has been introduced into the National Grid.

And with renewable generation accounting for nearly a quarter of the UK’s electricity supply in 2015, storing energy when demand is low so it can be released at peak times would provide some stability.

Cropped pilsworth 5mw pre commercial demonstrator in manchester (highview power storage)

Cropped pilsworth 5mw pre commercial demonstrator in manchester (highview power storage)

HPS’s Manchester demonstration plant, utilises cryogenics

The government recognises that storage has a key part to play in the transition to a low-carbon economy. In November it published a consultation document on the development of a smarter energy system, which included a focus on removing barriers to storage.

Progress is already happening – a recently published report from the Renewable Energy Association (REA) shows that the UK has at least 453MW of new, largely battery based storage capacity planned or in development.

“Storage, in the context of renewables, becomes really interesting because the technology is fascinating,” says UK Power Networks (UKPN) low carbon technology and customer engagement manager Adriana Laguna.

If you had a bunch of houses with solar panels and batteries, is there any way that those can support the network? They could help us manage the network better

Adriana Laguna, UK Power Networks

Regional distribution companies like UKPN then distribute the electricity to homes and businesses at a lower voltage. Finally, customers pay bills to an electricity supplier.

But the volatility introduced by renewables has disrupted that system, and the network is being forced to adapt.

“For the last, probably six years, we’ve been very focused on, ‘how do we prepare the network for that energy transition?’” says Laguna.

Leighton Buzzard battery

That question is being answered in the Bedfordshire town of Leighton Buzzard, where the largest grid-scale battery in the UK has been powering residents’ homes for nearly two hours each day.

UKPN first conceived the £13M project four years ago, and it has recently finished a two-year trial operation to prove that energy storage can be commercially viable.  

The 6MW/10MWh battery is the size of three tennis courts and looks a little like a data centre. It has been powering 6,000 homes in the town during its peak consumption time and will continue to do so, as UKPN is still running the battery.

The technology is not new – we carry batteries in our phones every day – but using it to support the Grid is novel.

“For the electricity system, it’s really exciting,” says Laguna.

Home storage

With more decentralised generation becoming the norm, battery storage for the home is another area to watch.

“If you have more renewables, if you have a lot of electric vehicles, does it get to a point where people are exporting back to the Grid from their houses?” asks Laguna.

UKPN is now investigating home battery storage, potentially trialling homes which already have solar panels to monitor the impact of small-scale batteries on household consumption.

“If you had a bunch of houses with solar panels and batteries, is there any way that those can support the network? They could help us manage the network better,” she says.

Ahead of the curve

US entrepreneur Elon Musk and his electric car and energy storage company Tesla are ahead of the curve, selling home batteries which can power an average two-bedroom house with solar panels for a full day. Tesla also advertises a commercial scale battery, highlighting the freedom it brings to create a localised grid, independent of the main network.

But its giant car battery factory, known as the Gigafactory and housed in a massive building in the Nevada desert is arguably more impressive.

The company’s mission is to speed up the global transition to sustainable energy. Tesla forecasts a production rate of roughly 500,000 electric cars per year in the near future, meaning it will require a significant portion of the world’s current supply of lithium ion batteries.

The Gigafactory’s purpose is to supply enough batteries to meet the demand.

Nevada Gigafactory

Construction started in Nevada in 2014, and the company expects the Gigafactory to reach full capacity in 2018. When finished it will make more lithium ion batteries annually than were produced worldwide in 2013.

There are plans for the factory to produce 35GWh of battery capacity each year, which, considering the scale of production, is expected to lower costs of its battery pack per kilowatt hour by 30%.

Most impressively the giant factory will be powered by renewable energy, which the company hopes will achieve its goal of being self sufficient in energy terms.

Cryogenic energy storage

Of course, batteries are not the only form of storage with the potential to bring stability to renewable energy generation. A storage facility is being commissioned in Manchester which will store energy using cryogenics – a term more closely associated with science fiction.

“It does conjure up the image of lab coats,” admits Highview Power Storage (HPS) business development director Matt Barnett.

“I think generally there is a misconception as to what cryogenic is, it makes it sound much more complicated than it is.”

A storage facility is being commissioned in Manchester which will store energy using cryogenics – a term more closely associated with science fiction

HPS’s liquid air energy storage process freezes air to -196°C using off-peak or excess electricity. This produces liquid air, which is stored in insulated tanks at low pressure. To generate power, the air is then pumped at a high pressure, heated and evaporated, causing a 700-fold expansion in volume. The high pressure gas then drives a turbine, generating electricity.

It is a similar concept to  hydroelectric energy storage, although without some of the downsides such as location constraints.

Less damaging than hydro-electric schemes

“You can build this on a nice patch of land and you don’t need to go and ruin the landscape and the mountains by flooding lots of villages away,” says Barnett.

The technology used in the process is around 110 years old, meaning it is already well established. The next challenge is to prove its scalability.

The demonstration plant in Manchester – which will only emit clean air and which can incorporate industrial waste heat from other plants – has an expected lifespan of 30 years and a capacity of 5MW/15MWh.

Design work has already begun on a new plant, which could have a capacity of 200MW/1.2GWh. But before this becomes a reality demand has to catch up, as most interest is currently aimed at the 20MW to 25MW scale.

“I think there’s definitely the interest there,” says Barnett.

“I think most of the types of folks we’re talking to for this technology are looking at problems in the next 10, 20 years, so they want to be comfortable with the technology now.”

Mainstream in 10 years

It is hoped that the technology will become mainstream within the next 10 years, and Barnett has received some enquiries for 100MW systems which have several hours’ capacity.

But with cryogenics’ high storage potential, where does that leave batteries?

Barnett thinks the two are compatible. Cryogenic storage currently has a better cost value as it scales up and it can support the Grid for a longer duration at a higher power than batteries. However, as batteries can turn on and start working in milliseconds they are better suited to frequency response.

Whatever the storage mix, the rise of renewables means that solutions will be needed with increasing urgency. As Barnett says, “The problem on the Grid is only going to get worse.”

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