Net Zero? The big picture is looking good, but there are some gaps to fill in
Last week saw the publication of the International Energy Agency's (IEA) renewables outlook, a kind of annual report on world progress towards Net Zero. In the midst of a gloomy year, it was a surprisingly upbeat assessment.
Although they didn't actually resort to the cliche about every cloud having a silver lining, IEA analysts have clearly come to regard the Russia-Ukraine war as a kickstarter for the renewables sector. SolarPV capacity is going to double over the next five years. Wind generation will increase by 65 per cent over the same period. Putin's invasion will result in the world's energy map being redrawn, with green energy overtaking coal by the end of the decade.
Result! But this rosy picture is complicated by another cliche, the one about the devil being in the detail.
As anyone who follows the ups and downs of the wind generation sector will attest, having generating capacity isn't the same thing as having power in your wall sockets. Wind generation is notoriously unreliable. If it's a still day, all the gigawatts of your turbine bank will be left sitting idle. SolarPV generation is more predictable, but it still remains less reliable than coal, gas or nuclear. Ensuring the integrity of our energy supplies as we transition away from carbon is going to be a challenge.
Balancing up
It's important to understand that imbalances of supply and demand are nothing new. While supply-side shortages are something of a novelty in Europe - unless you count the strikes of the early 70s - demand-side variations are a fact of life throughout the industry. (You've probably heard the old factoid about all the nation's electric kettles being switched on at once when the half-time whistle sounds in a World Cup match.)
In the UK, the National Grid deals with such imbalances by means of dispatchables, generating resources that are relatively expensive to run but deployable at short notice. In, say, 1995, Grid engineers would have relied on coal and nuclear for baseline requirements and used gas-fired turbines as dispatchables. But now those resources now becoming less and less acceptable. Where are the green dispatchables that will take their place?
Some of the necessary technologies are already in place. For example, older readers may remember the rollout of pumped-storage hydroelectric in Scotland, when engineers showed off the systems that would use off-peak kilowatts to pump water back up into storage reservoirs in preparation for release during upcoming peaks. Geothermal and biomass systems can apparently be tweaked to function as dispatchables, too... but the IEA team is right to highlight a shortfall and to call for government initiatives to plug the gap.
Blue-sky solutions like sand batteries and gravity storage, both of which we've covered in these pages, may provide a long-term fix. In the meantime, the best response is likely to take the form of upmarket virtual power plants. With grid inverters and smart storage batteries, banks of household solarPV installations can become a powerful peaktime resource.
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