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Abstract

Why a big battery cannot stabilise an electrcity grid supplied by wind and solar alone. Most enthusiasts for wind and solar would love a technology that offered an electrical mega battery capable of storing renewable energy for a week, or even just a day. To a potential investor in the energy business a battery is a seductive idea-just put your surplus energy in and take it out when needed. This could then bridge between the times when energy is available from solar and wind and those when it is not. In this way the principal fault of these renewables could be overcome. There are two problems, the capacity of the battery and the ease with which you can get the energy out again. If you can store a large quantity of energy and get it out easily, then a battery is explosive. It does not need a detonator circuit because it's already wired. A look at the numbers. How much energy should a fully charged grid-scale battery hold? At 30 GW the UK grid provides an energy of one terawatt-hour per day. That is equivalent to the energy of a thousand bombs of the size that exploded recently in Beirut. Enthusiasts for grid-scale batteries should beware what they wish for. In practice do big batteries spontaneously explode or burn in this way?
Big batteries an explosive issue
Wade Allison, Physics Department, Oxford University wade.allison@physics.ox.ac.uk
Most enthusiasts for wind and solar would love a technology that offered an electrical
mega battery capable of storing renewable energy for a week, or even just a day. To a
potential investor in the energy business a battery is a seductive idea just put your
surplus energy in and take it out when needed. This could then bridge between the times
when energy is available from solar and wind and those when it is not. In this way the
principal fault of these renewables could be overcome.
There are two problems, the capacity of the battery and the ease with which you can get
the energy out again. If you can store a large quantity of energy and get it out easily,
then a battery is explosive. It does not need a detonator circuit because it’s already
wired. A look at the numbers. How much energy should a fully charged grid-scale
battery hold? At 30 GW the UK grid provides an energy of one terawatt-hour per day.
That is equivalent to the energy of a thousand bombs of the size that exploded recently
in Beirut. Enthusiasts for grid-scale batteries should beware what they wish for. In
practice do big batteries spontaneously explode or burn in this way?
Cautionary tales from South Korea, Arizona and Liverpool
The health and safety authorities do not yet seem aware of the dangers. Here is a recent
report from S Korea about twenty fires at energy storage units in the past year. The
Korean Government officials are said to have no clue as to what happened. They should
study the physical chemistry of batteries.
From The Korean Times, 7 Feb 2021:
Government officials have no clue as to the cause of fires that have destroyed more than 20
energy storage systems (ESSs) nationwide over the past year, the Ministry of Trade, Industry
and Energy said Thursday. ESS manufacturers who were ordered by the government to
suspend production have lost tens of billions of won while waiting for guidelines from
policymakers. The energy ministry said it will be able to announce the cause of the fires next
month, but did not suggest any clues as to what had caused them, despite the investigation
committee meeting more than 60 times since January. "Since the fires wholly destroyed the
ESS equipment, and parts from different firms were used in manufacturing, it is inevitable for
the investigation to take some time to find out the cause transparently and fairly," the ministry
said. From May 2 last year to Jan. 22, 21 ESS many fires were reported across the country. In
December, the government asked public institutions, large multi-purpose facilities and private
owners to stop using the ESSs. Following the recommendations, the government set up the
investigation committee in January and promised to find out the cause by March, but has yet
to do so. "The committee is conducting experiments to see what sets the ESSs on fire," the
ministry said. "The committee has listed 76 possible causes and tested 53 of them." The
ministry said it has found fire-causing conditions in two experiments and the circumstances
observed in the experiments were "similar" to the actual accidents. On growing criticism of
the investigation's slow process, the ministry said: "The investigation of the Galaxy Note 7
fires took five months and the recent BMW fires also took five months." While the
government is taking time to find the cause of ESS fires, companies running and making the
battery systems are continuing to suffer. The ministry said 522 out of 1,490 ESS facilities across
Korea are suspended from operation as of April 30. This is down from 765 in March. No ESS
orders have been made to manufacturers so far this year. Amid the uncertainty, LG Chem
suffered a 120 billion won loss in its ESS business in the first quarter of this year. "Initially, we
planned 80 percent growth in ESS sales, but at this point, we doubt 50 percent growth," LG
Chem CFO Jeong Ho-young said. Samsung SDI, another major ESS maker, posted 1.73 trillion
won in sales in its battery business in the first quarter, down 7.9 percent from a year earlier.
Industry officials said the burden is heavier on smaller firms. "Large companies can handle
that kind of losses stemming from this uncertainty, but it is a matter of now or never for
smaller ESS makers because they don't have financial room to withstand this deadlock," a
battery firm official said. "To complement the limits in renewable energy, advances in the ESS
industry are crucial, but this slow progress and setbacks in running ESSs will deal a heavy blow
to the country's shift to renewable energy." An ESS is a large stack of rechargeable batteries.
It is often used for storing cheap off-peak electricity or coupled with solar, wind or other
intermittent power generators.
Then an insurance report published last September noted “An investigation into the cause
of an explosion at an Arizona energy storage facility that injured four firefighters
confirms what engineers had feared: Packing lithium-ion batteries tightly together can
spark a chain reaction that can cause catastrophic damage and endanger lives. Arizona
Public Service is holding off on its plan to aggressively expand battery storage capacity
while its suppliers draw up new plans that will reduce the risk of similar accidents.
Carnegie Road BESS in Liverpool, UK, as it looked when completed in early 2019. Image: Ørsted.
Less than a week later there was a report from Liverpool, There has been a fire at the
Carnegie Road 20MW battery energy storage system (BESS) project in Liverpool,
England, project owner Ørsted has confirmed. Merseyside Fire & Rescue Service
arrived to find a large grid battery system container well alight”. As so often, the
capacity of the battery in MW-hours is not given perhaps because it is both too small
to bridge the intermittency of renewables and too large to be safe. Such dangers are
compounded by the lack of scientific transparency and not openly acknowledged. The
result is a fire or explosion, reported as mysterious.
A look at the science of electrical batteries
The laws of chemistry limit the energy density of batteries. A modern Lithium battery
has an energy density when charged of about 1 Mega-joule per kg. So the UK “day-
battery” would require several million tons of battery. Fortunately, this would be as
unrealisable and unaffordable as it would be dangerous. Having moved from lead-acid
to lithium there is little further progress to be made by using lighter electrodes. The limit
would be the hydrogen fuel-cell. The Periodic Table of chemical elements cannot be
extended below hydrogen by investment. The energy per cell, a few volts, always lies
in a narrow range reflecting the electronic structure of matter.
So little progress on mega-batteries is likely, and battery accidents, plus belated safety
regulations with insurance and related costs, are to be expected. This was already a
problem in the development of batteries for mobile phones and laptops, and is likely to
become more common with batteries for electric transport. At the scale required to
ensure the viability of renewables an electrical mega-battery is fortunately just a dream
but also an unrealisable nightmare.
Note: Some new so-called “batteries” are not electrochemical, but nuclear. They are not batteries at
all in the above sense. They are playing with the word battery.
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