Scotland has become the first part of the UK to stop burning coal to supply electricity following the closure of Longannet, its largest power station, on March 24. According to Paul Younger, Professor of Energy Engineering at University of Glasgow, the closure of coal-fired power plants in the UK may lead to serious problems with voltage control. Prepare for power interruptions and flickering lights.
The closure of Longannet is a sign of the times, with the rest of the UK’s coal-fired power stations on death row after energy secretary Amber Rudd announced late last year that they will all be forced to close by 2025.
For many reasons, it is hard to mourn the demise of coal-fired power. Around 12,000 miners are killed around the world each year, most of them digging for coal; abandoned mines cause widespread water pollution; and coal-fired plants pollute the air with the likes of nitrogen and sulphur compounds, as well as the highest greenhouse-gas emissions of any major source of energy generation. In the absence of carbon capture and storage, a technology which would be ready more quickly if the government backed it properly, plant closure may therefore seem sensible – even while we should help those that lose their jobs and regret the loss of skills from the workforce.
If we are going to manage without Longannet and all the other gas-fired and coal-fired power stations, we would need at least 970 GWh of storage – more than a hundred pumped hydropower stations of comparable size to those we already have
That would be all there was to say were it not for a few harsh realities of electricity supply. There are two reasons why coal-fired power plants have survived so long. Coal is cheap; only since the US shale-gas boom has it been consistently beaten on price. And coal-fired plants are particularly suited to providing power on demand at short notice, as well as providing crucial stabilisation services for frequency and voltage across the grid.
Power on demand
If we are unable to dispatch electricity on demand, we must expect blackouts. To do away with coal-fired power before alternatives are available is bold, to say the least. Gas-fired plants can play the same role, of course, but we have not been building them in the UK in recent decades. And the economics for doing so have been made very difficult by the capacity-auctions system that helps to fund them, which has also seen many existing plants mothballed. As for nuclear power, it is low-carbon but provides electricity at a constant rate and therefore can’t be increased to track demand. Besides, the ongoing fiasco over Hinkley C – and by extension nuclear new-build in general – hardly makes it look a great contributor to energy security in the foreseeable future.
We may be heading into dangerous territory. The UK needs to get a strategy together for building new gas-fired or coal-fired power, fitted with carbon capture and storage technology, before the situation deteriorates any further
Among the renewable sources, the only one that offers equivalent dispatchable power is biomass combustion – burning mainly wood – but it also entails air-quality challenges and its sustainability is debatable. Hydropower is seasonally limited, while wind and solar are incapable of dispatchable output. The consequences are not just for the future, either – to compensate for the reduced coal-fired and gas-fired power, National Grid has been quietly allowing energy companies to set up “diesel farms” of temporary generators in England to provide extra power in peak, even though it’s more damaging than coal.
But can’t we just store renewable energy, whenever it is generated, and dispatch it at times of high demand? Let’s be clear: we have the technology – it’s the affordability and scale that are challenging. Of the myriad potential storage technologies, none are as yet close to being able to store electricity at comparable scale and cost to our only grid-level storage technology: pumped-storage hydropower.
But pumped storage can only do so much. Let’s assume the UK could muster sufficient wind power to meet one third of our typical daily electricity consumption (40 GW to 45 GW). In the absence of dispatchable power on demand, to offset the kind of three-day calm period that is common during spells of high pressure in winter, we would need to be able to store around 1,000 gigawatt hours (GWh) of power. Yet pumped storage hydropower in the UK only totals 30 GWh, from four stations.
If we are going to manage without Longannet and all the other gas-fired and coal-fired power stations, we would need at least 970 GWh of storage – more than a hundred pumped hydropower stations of comparable size to those we already have. This would be unlikely to cost less than £100 billion. And do we even have 100 plus upland catchments we’d be happy to impound and manage for this purpose? Even if most of the UK uplands were not (rightly) zealously protected conservation areas, it seems implausible that the UK could find sufficient sites.
So as we close plants such as Longannet, we can expect serious problems with voltage control. This bodes ill for the electrical appliances and devices on which we all increasingly rely.
Add the important caveat that you lose energy sending it back and forth to a storage facility, between 10% and 35% depending on the technology. This means that relying on renewables and increased storage means you would need substantially more total generating capacity than at present.
The voltage issue
So far we have only talked about power quantity, whereas power quality is also crucial. To keep voltage within prescribed bounds requires “reactive” (or “wattless”) power. Coal-fired power-stations have long been the mainstay of this activity – not least in Scotland. It has to be done regionally, so you can’t make up for this with coal power from elsewhere. Wind turbines cannot provide reactive power control, and neither can nuclear. Gas-fired power is again the only alternative.
So as we close plants such as Longannet, we can expect serious problems with voltage control. This bodes ill for the electrical appliances and devices on which we all increasingly rely. With the closure of Longannet, Scotland thus becomes the first area of the UK to take a serious gamble with reactive power. It will take not just good management but a serious amount of good luck for the fossil-fuel funeral wake not to be spoiled by flickering or failure of the lights.
In short, we may be heading into dangerous territory. The UK needs to get a strategy together for building new gas-fired or coal-fired power, fitted with carbon capture and storage technology, before the situation deteriorates any further.
Editor’s Note
Paul Younger is Professor of Energy Engineering at the University of Glasgow. This article was first published on The Conversation and is republished here with permission.
Jan VeselĂ˝ says
Professor should look around before he states that something is impossible. There can be some fool who doesn’t know and make it happen. Then the professor will become a fool.
PV inverters in Hawaii are capable of providing reactive power, after a software update :-). As well as some US wind farms. The key is legislation, when you allow them to join that lucrative market, they join. When you establish impassable conditions (like here in CZ), they will not join.
Elementary, my dear Watson.
Mike Fletcher says
Good points, but I find the discussion too narrow. Things I find to be missing to cover low supply or high demand periods
– demand response
– power imports
– over building some non-dispatchable resources (wind, nuclear) to better cover high demand periods. During low demand periods this power can be made into hydrogen and be mixed into the gas grid.
– underwater compressed air storage – currently being undertaken by Toronto Hydro and covered on their web site.
Also, too much is made of voltage regulation. This can be done with a small amount of spinning storage as is done in Ontario, Canada – see IESO.
Peter Mott says
Demand response: The SBR (supplemental balancing reserve) is set up to allow cutting power to big industrial usesers – they are paid for this and start up their diesel generators I guess. Power imports: ther is 3.5GW interconnection with England I think, though I don’t know about its availability. Overbuilding wind: the trouble is that as more wind becomes available supply typically exceeds demand so either one has to pay curtailment subsidies or the economic case for building them fails. This problem is already stalling the development of new gas generation. Not clear what the outcome will be, which is I guess what Paul Younger was saying.
Grace Adams says
I like Pres. Obama’s all of the above energy policy better than too much reliance on any one or even two or three technologies.
Mark Taylor says
Looks to me as though we have subsidised clean renewable energy; causing higher electricity bills. Then, now there is a shortage of dispatchable energy we will be subsidising dirty top-up energy; causing higher electricity bills and/or we will be paying heavy industry not to produce in peak hours; causing higher electricity bills. Brilliant. If it wasn’t such a serious issue I’d suggest DECC doesn’t start a brewery.
Peter Mott says
Didn’t Margaret Thatcher use Scotland as a testing ground for her Poll Tax?
Grace Adams says
I like Jan Vesely’s comment about PV inverters in Hawaii. I also like Mike Fletcher’s comment about overbuilding non-dispatchable power and storing surplus as hydrogen from electrolyzing water and mixing the hydrogen in with natural gas.
Ian Porter, Perth Aus says
Electrolysing water with wind while highly inefficient can be considered a ‘fair’ solution but storage in pipelines is folly. Hydrogen is a tiny molecule and finds its way out of virtually anything its contained in. Take for instance the Boston experience. It was assumed that there were some thousands of leaks in the pipe network. Hydrogen was also injected into the network in a similar conservation measure. You can be sure, not one of the molecules ever made it to the customer! Horses for courses!
Mike Parr says
If there are problems with leaky pipes vis a vis H2 then push the H2 through a menthanisation stage – and there you have CNG. Electrolysis “highly inefficienct” – compared to what? very roughly a full P2G system (with heat recovery) is around 75% “efficient” turning elec’ into methane and useable heat. A good electrolyser will use 60kWh to make 1kg of H2. CNG/SNG used in trnasport provides an excellent solution to Europes big unsolved problem: how to decarb transport emissions.
Grace Adams says
Didn’t Boston decide it had a problem with leaky pipes and replace much of its local natural gas distribution system shortly after that? Maybe hydrogen is good ONLY for storing for short lengths of time and shipping over short distances.
Mike Parr says
“If we are unable to dispatch electricity on demand, we must expect blackouts”……..National Grid estimates that in terms of demand response the Uk has around 9GW of capacity. This could provide an answer to the “evening peak” “problem”. The others have provided plenty of other critiques – reactive power? – plenty down south in the Uk (where it is needed) – from aggregated ground-mount PV systems with their 4quad inverters – thing is – the DNOs would be “unhappy” etc etc.