this post was submitted on 21 Oct 2023
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Futurology
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I'm not criticising solar energy, I'm criticisng their projection that solar will become the dominant power source. I say that as an HV electrical commissioning engineer who has worked extensively on a range of renewable sites.
In particular, they gloss over the grid stability aspects. Inverter driven generation like solar (and most wind) is inherently chasing, it measures the voltage and frequency at its output and uses that to form a feedback loop controlling the generation output. This means it is poor at handling load changes - especially compared to traditional rotating mass generation, which has inertia behind it. There are solutions for this, but they have drawbacks.
In general, their study seems to lack any real understanding of the nature of the electricity network.
Solar is very important, and we should be going hard on installing current renewable technology over all else to get to net zero as quickly as possible. But, to me, this reads as economists patting themselves on the back for creating a computer generated model. The saying goes, "all models are wrong, some models are useful" but economists are prone to making models without actually testing them thoroughly.
Wind turbines are also a rotating mass system, there is a significant amount of energy in the rotor that is used to stabilise the grid on short term by slowing down or speeding up the rotor.
The mass in a wind turbine is much less than conventional turbine generators. Also, wind turbines are mostly half or fully converted, where the raw AC is converted to DC and then back again to smooth out the waveform. Thus, wind turbines are generally inverter driven generation and have poor ride through capabilities.
They can control the generation manually somewhat, to provide VAr and frequency control, but when it comes to unexpected disruptions they can easily fall out and trip.
Yeah the rotating mass of a single turbine is relatively small but inertia is significant due to the size of the rotor (rotor diameters of 100 to 200 metres are not uncommon). On top of that we should compare the inertia of a entire windfarm to a convential turbine.
The size difference is still huge. A new onshore turbine might be 5MW, offshore is now maybe 10-15MW, but a single big turbine in say a nuclear or coal plant could be hundreds of MW or even into the GW. The machines are just much bigger and much more massive.
That doesn't mean we should prioritise them, however. The UK's National Grid did a Future Energy Scenarios study and determined that the fastest way to net zero is to go hard on current renewable technology. It's ready, it's proven, and it's cheap and quick to build. Money spent on nuclear is just money that could be spent on getting renewables up and running more quickly, and we'll almost certainly use more combustible fuel waiting for nuclear than we would backing up renewables. If we build a large excess in renewable capacity we should be able to meet almost all demand, regardless of when the sun isn't shining or the wind isn't blowing (the sun still shines through the clouds and it's usually always blowing somewhere), and if we focus on building nuclear afterwards then by the time that's operational our demand may have increased so much that the excess of renewables isn't an excess anymore.
In terms of grid stability, rotating stabilisers are one solution. They're basically giant, heavy spinning discs, providing the same mass and inertia you would get from a large turbine, but driven electrically off the grid. They're used often on large ships, eg cruise ships and aircraft carriers, however on land there is a little concern over what might happen if they fail - the last thing you want is several hundred tons of metal spinning at hundreds or thousands of RPM rolling through the countryside lol. It's quite funny how the manufacturers have different ideas on how to deal with this, GE use gearing to reduce the RPM, Siemens use loads of sensors and monitoring to detect when it's failing before it happens, and ABB plan on shunting all the momentum into this smaller thing housed in a brick building that they hope will contain it.