ENERGY


Batteries are a global industry worth tens of billions of dollars, but over the next 10 to 20 years it will probably grow to many hundreds of billions


Gregory Offer Imperial College London


density.’ Yet another option is sodium


ion batteries. ‘People are looking at sodium ion as an alternative because it is a lot cheaper. It needs more R&D, but a few companies are looking to commercialise this technology,’ says Wu. UK battery manufacturer Faradion showcased its sodium ion technology in an electric bike as a proof of concept in 2015. The company’s sodium ion batteries are claimed to have higher energy densities than lithium ion batteries. They can also be manufacturing using existing Li ion manufacturing lines, the company says.


Sodium potential Some battery scientists are sceptical over the potential for sodium ion battery technology in car applications. ‘The performance isn’t as good as lithium,’ in Wu’s view, ‘[but] you might use sodium ion for grid applications,’ he says. The UK recently launched new


rules to make it easier for people to generate their own power with solar panels, store it in batteries and sell it to the National Grid. UK regulator Ofgem said the rules will apply from 2018 and should save consumers up to £40bn by 2050. For now, Li ion is an obvious


choice for grid storage in terms of batteries, since it’s a proven technology. University of Oxford battery engineer, David Howey has been testing batteries such as sodium ion batteries; he says sodium ion will hopefully ‘lower costs, be a little more robust and discharge down to zero volts’, making it easier to safely transport. Solar and wind energy, however,


bring problems of unpredictability and intermittent supply. So far, few battery packs are capable of smoothing out the peaks and troughs, but this will change as the technology advances.


In September 2017, Tesla announced the world’s largest Li ion battery was half completed: a 129-megawatt hour behemoth for South Australia’s electricity system. ‘Lithium ion is still a contender for grid, but costs might be prohibitive,’ says Howey. ‘Lead acid is a contender because weight and size doesn’t matter so much, and cost-wise it is so cheap and almost 100% recyclable.’ The problem is that its cycle life is limited – it doesn’t last very long. Howey says the technology’s longevity can be improved if we continue to understand it better and model it. However, some in the field believe


electrochemical storage does not yet make sense. ‘Wind and solar are accelerating at a massive rate, but at the moment it is not really economical to store it,’ says Wu. Alternative storage solutions include thermal storage, pumped hydro, compressed air and redox flow batteries. ‘We already have sufficient flexibility on the grid at the current penetration levels of renewables,’ says Offer. ‘Moving forward, though, to manage the variability of renewables, storage will become essential.’ Householders, meanwhile, are an emerging market for battery storage. In Germany, for example, homeowners are offered a subsidy to meet the initial costs of a battery to store the electricity from solar panels.


Futuristic chemistries For electric cars, the ultimate technology in terms of energy density is rechargeable metal-air batteries. These work by oxidising metals such as lithium, zinc or aluminium with oxygen from the air. ‘Making a rechargeable air breathing electrode is really hard,’ warns Offer. ‘To get the metal to give up the oxygen over and over again, it’s difficult.’ ‘I don’t see solid state, lithium sulfur and sodium ion as competing


£246m


against each other, other than for headlines,’ he continues. ‘They are very different technologies: lithium sulfur is good for energy density; solid state for safety; sodium ion for cost.’ Graphene and carbon nanotubes


UK government investment in battery technology R&D announced in July 2017


ca$200


Cost per kilowatt hour of stored energy from today’s Li ion batteries, down from around $1000/kilowatt-hour in 2010


Li sulfur has a theoretical energy density five times higher than Li ion. In September 2017, US space agency NASA said it will work with Oxis Energy in Oxford, UK, to evaluate its Li sulfur cells for applications where weight is crucial, such as drones, high- altitude aircraft and planetary missions


129 MWh


also offer exciting possibilities for future batteries, because of their inherent high electrical conductivity. The challenge is to make graphene in large enough quantities that the material becomes economical. But manufacture is also an issue. ‘Lots of papers in Science and Nature report extremely impressive energy densities, but typically they introduce a new nanostructure. You can make grams of materials in the lab but some of these material innovations do not scale up well,’ says Wu. In the case of graphene, Offer


predicts it will be used as an anode material in a small working device within five years, with ‘someone actually making these devices in another five years, though they’ll be expensive’. Whatever pans out, the UK wants


to nurture battery-focused SMEs and forward-thinking research groups in universities. The latest investment plan envisages support that links across research, innovation and scale-up, Walport advised the government. ‘Whilst UK research funding has


Capacity of the world’s largest Li ion battery when completed; it is currently being designed by Tesla for the electricity system of South Australia, the country’s most wind- dependent state


previously been applied at all three of these levels, there has never been a programme that is explicitly and formally linked across these levels and scaled to address a specific industrial challenge,’ Walport wrote. ‘Doing so would drive improved efficiency of translation of UK science excellence into desirable economic outcomes; would leverage significant industrial investment in the form of a “deal” with industry; and would send a strong investment signal globally.’


10 | 2017 25


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52