By Douglas Pollock
Advocates of wind and solar power confidently assert that using it to replace a coal-fired power plant will abate all the CO2 formerly emitted by the coal station, because unreliables do not emit CO2.
To keep the lights on when we need them, wind and solar requires backup from flexible sources, such as natural gas, that can react quickly when the Sun rises or sets, or when the wind drops or blows a gale.
This thermal backup emits CO2. Worse, when thermal stations are on standby, known in the trade as rotating reserve, they burn fuel without feeding any power to the grid and, when needed, they must be suddenly ramped up to full load capacity, thus emitting far more in the process than when running permanently at full load. Their emissions must thus be subtracted from the reductions achieved by decommissioned coal-fired capacity.
Why would anyone bother with wind and solar power? The fastest way to reduce grid emissions is to switch from coal-fired to gas-fired generation without using unreliables at all. That coal-to-gas switch cuts CO2 emissions by the difference between the products of the CO2 output emission rates and outputs of coal – a far greater reduction than that which is achieved by replacing coal with renewables backed up by thermal sources.
For instance, in 2019 US grid emissions abated would have been almost 18% greater if all coal-fired power replaced thus far by gas-backed wind and solar had instead simply been directly replaced by gas-fired power.
However, the US also uses a fraction of oil and coal generation to backup renewables. Since these fuels emit almost three times as much CO2 as natural gas, grid emissions abated would have been more than 90% greater if coal had been directly replaced by natural gas generation instead of renewables backed up by the current thermal-reserve mix.
Reductions in grid CO2 emissions (even if they were desirable) have come not from adding wind and solar power to the grid but from replacing coal-fired power directly by natural gas generation. Wind and solar power actually hinder emissions abatement.
The next time you see a wind or solar farm being installed, while a coal-fired plant somewhere else is dismantled in the name of Saving The Planet, praise the gas-fired station hidden behind those renewables. Without it, they could not exist, and nearly all the modest emissions reduction currently but falsely attributed to unreliables would never have occurred.
The most significant effects of adding wind and solar power to any grid are to destabilize it and greatly to increase the cost of electricity for homes and businesses everywhere. In those countries where the installed nameplate capacity of wind and solar – their output in ideal weather – exceeds the total mean hourly demand on the grid, adding more wind and solar will not reduce emissions at all, unless absurdly expensive battery backup is also installed. Wind and solar are a pointless, costly, environmentally-destructive dead end.