Battering the battery option

Battering the battery option

by Paul Spare
article from Monday 2, July, 2018

RENEWABLE POWER, particularly wind turbines, offer a very unreliable and unpredictable means of generating electricity.  Their output can vary over a range of 100 over two days ie from 5000 MW down to 50 MW.  The idea has been proposed to use large battery systems to store the surplus from days of high output and release it on the calm days.  A thorough study of this technology reveals unimaginable costs and challenges.

Firstly, whatever the cost of this technology, it has to beaddedto the cost of renewables –  in contrast to coal, gas-fired and nuclear plants that can operate all year round without such backup. It is a parasitic cost.  The costs of batteries have fallen by 50 per cent, in recent years, but  the Li-Ion assemblies of Tesla cars are still in the range £5,000 to £10,000.   

Time magazine published an article showing the largest 90kWh battery in a Tesla, as one example, can store enough electricity to power the average American home for more than three days…that could be one week with the UK’s lower consumption.  That is a valid period of time over which wind power output is very low for several times per year.  Grid storage would demand much larger batteries than in the Tesla, but indicates the unit costs to supply just one household.   Considering that there are some ten million households, even allowing for mass production reducing the cost of batteries, tens of billions of pounds of investment would be required.  

Most people are more familiar with the rechargeable batteries in the mobile phones. These may be rated at 3000 or 5000mAh.  To store the thousand, million kWh of electricity generated in the UK on a cold day would require each of us to have one thousand phone batteries.

As another indication of the costs, researchers at Warwick and Birmingham universities and Cenex, have concluded that using lithium-ion batteries for energy storage residential solar systems in the UK would cost about £400 per annum per installation.

Battery lifetime is also a very serious concern and will be familiar to most owners of laptop computers, smart phones or other portable gadgets. Gas-fired power stations may have a life of thirty years at close to full output.  Many nuclear plants are reaching fifty years before retirement. Rechargeable batteries in contrast often struggle to achieve five years and degrade within months loosing storage capacity progressively.  Not only would there be an enormous investment in a new technology, but there would have to be a programme of continuous replacement to maintain the storage performance.

It is also necessary to look at the generation implications. When conditions are most favourable, wind power produces only about 6,000MW – 10 per cent of peak electrical demand (60 GW) so it would be necessary to multiply the ten thousand turbines by ten to meet the peak.  Of course, since we would be attempting to meet the peak demand, but also produce a surplus for storage, the factor of ten would have to increase to more than twenty to be able to obtain surplus power for a low-wind week in the coldest time of the year.  Even this is probably too low because the high-wind speed, low pressure weather systems tend to be localised.  There could be gales in Scotland but low wind speeds in the south, necessitating even more turbines.

The demand for the raw materials would increase enormously and be in addition to the demand for batteries for the increasing fleet of electric vehicles, since all the other countries that did not have low carbon hydro-electric or nuclear plants would want to follow the same route.  

There will also be complex technical and engineering issues with the siting of the battery storage facilities.   They would need to be located close to the points of power generation to reduce the power losses between the wind parks and the batteries. This would point to them being located in the uplands or close to the coasts where industrial developments would be very obtrusive.  Unfortunately the concentration of turbines is very different from the areas of high demand. The power is needed in the Midlands and South East of England. Very complex control systems would be needed to feed the power into the transmission and distribution systems so as not to overload the local circuits. stabilising the whole grid system could be impossible with so much DC power coupled to all the wind turbine induction generators.

Finally, there are the environmental considerations.  These batteries are complex mixtures of toxic chemicals and use rare earth metals that are found in few locations and small quantities.  The recovery and extraction of the metals will be undertaken in countries with lower standards than are applied in Europe and the USA.  Since battery lives are short compared with other power plant equipment, recycling and disposal will have to be undertaken on a massive scale requiring elaborate and costly precautions.

Brian RL Catt  CEng, CPhys, MBA, MCIM and Paul Spare CEng FEI FIMechE

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