The energy storage question

Marco Clemente | 22 Oct 2015 | Comments

The UK has significant technology and policy gaps that need closing if it is to deliver on the legislated 15% electricity from renewables by 2020, and 80% by 2050. The lack of suitable planned energy storage capability is at the top of this list.

Cracking Energy Storage is therefore one of the ultimate ambitions for engineers working in the Power and Renewables sector today. Whilst gas, coal and other traditional fuels can be stored conventionally (via open air, pressure vessels or (salt) caverns); figuring out a way to balance supply and demand from a growing scale of intermittent generation sources is much trickier.

The drive to develop a useful way of storing excess electricity is being made all the more urgent as more renewable generators come online around the world. This is a global effort – countries across Europe and the Middle East are steadily increasing the amount of renewables that are connected to the grid and the huge onshore wind farms in China and the USA add gigawatts to domestic production. Grid connected wind farms, both onshore and offshore, can now meet about 10% of the UK’s energy demand and in December 2014 set a record for supplying 14% of the country’s electricity.

However, we can’t control when the wind blows or when the sun shines. Frequently, peak production occurs when demand is low and there is nowhere for the electricity to go, so the wind farms are disconnected as their power is not needed. If we could increase the energy storage capacity on the grid, this would enable us to offset the peak generation of renewables and store this green electricity for use during peak demand. This in turn would offer a number of benefits and reduce the need to use electricity generated from more carbon intensive plant; not least reducing harmful greenhouse emissions.

So what’s being done to try and crack this nut? There are a number of proposed solutions that could provide the answer:

Pumped hydro is currently the world’s largest form of grid energy storage available, representing more than 99% of bulk storage capacity worldwide. In Scotland, the current energy storage capacity of 745MW is delivered through Foyers and Cruachan pumped storage, yet almost 3000MW of capacity is estimated to be required by 2020 (IMECHE). There are now limited natural sites suitable for the expansion of pumped hydro in the UK, so this compels engineers to look for innovative alternative solutions.

Hot of the press is the launch of the TESLA lithium-ion batteries in the UK. Lithium ion batteries have been around since the 1990s, but only recently improved efficiency (up to 90%) and lower costs have driven commercial viability. Containerised solutions have been deployed in China, South America and the US to complement the expansion of wind power and help to increase grid stability and provide load balancing. The major disadvantage of the Li-ion solution is cooling and the parasitic losses that can impact efficiency, especially in hotter climates.

Flow batteries presents another solution. Using an electro-chemical process, flow batteries can be scaled up and benefit from high power to energy ratios. In the UK, a DECC funded demonstrator will deploy a containerised 105kW system that would provide 12 hours of storage.

Atkins has been involved as an official advisor to DECC for the energy storage Innovation Competition. This initiative offered £17 million to UK businesses to develop and demonstrate innovative energy storage technologies; which can address grid-scale storage and balancing needs in the UK electricity network in the run up to 2020. The successful projects included smart grid technology Moixa technology, REDT UK flow battery and Viridor-Highview liquid air energy storage.

Other, perhaps less publicised technologies include a whole host of exciting concepts. These include large scale ‘hydraulic hydro storage’; where a piston of rock is used to drive high pressure water through a turbine. Offshore wind energy storage is also readily being discussed, with possible underwater compressed air storage in giant balloons or integrating thermal storage into the floating structure. Other solutions combine existing hydrogen creation through electrolysis with fuel cells; one solution looks at capturing CO2 from air and combining with hydrogen for electricity production.

Clearly there is some way to go to develop each of these concepts into something that will have tangible benefits in the real world. Over the coming months we will see more energy storage projects being constructed with many novel and interesting technologies being tested. It’s unlikely that there will be one clear winner – and perhaps a one size fits all approach just won’t work here – so in the next decade expect to see different ideas deployed addressing particular requirements.

Our Energy Storage business is exploring how we can best help push forward some of these options. By combining and utilising existing expertise across Atkins we are looking to develop our capability and be a front runner in this field. Currently, we are working closely with our clients to learn from recent demonstrator deployments, and how the regulatory drivers might present opportunities for them. The changes that are already taking place across the UK national grid present an exciting opportunity and one that Atkins must be adaptable and innovative to seize.