Before thinking about how to replace fossil fuels for electricity, we need to look at how the power demand varies through the day. Not unexpectedly, this varies depending on where you live, but if you take various parts of the US as an example of industrialized usage, there is a baseline that involves minimal usage at about 0500 hrs, and that baseline varies by up to 30% seasonally. The difference between day and night can vary by up to 60%, the biggest variation is in hot summer and is due to the use of air conditioning. This means there is a huge difference between peak demand and minimum demand, which in turn means that difference has to be supplied by generation that can be turned on and off. The big thermal plants do not turn on and off easily. You can run the plant without producing electricity, but now you are simply burning fuel for no purpose.
The most responsive generators are the gas turbine and hydroelectricity. Hydro is an obvious “green” source for load smoothing; you simply shut the gate, save water, and stop generating, but most suitable hydro sites are already used. Wind power is also useful; you simply let wind pass if you do not want power, but it runs into trouble when you need power and there is no wind. Solar means you charge batteries during the day and used the power later, but in a previous post I showed it is impossible to make enough batteries to power our vehicle fleet, so how do we make an even greater supply of batteries? A further alternative is to run your base load near maximum usage, and use the surplus to make something like hydrogen when it is not needed. More on hydrogen in a later post.
The “inconvenient truth” for some is the only general major base load provider to replace coal and gas for electricity generation is nuclear. Unfortunately, nuclear has a bad press. Other downsides include, currently, it is too expensive. Most people think it is too dangerous and it is too likely to leak radiation. Actually, the smoke from coal combustion also is cancer inducing to lungs, while in the US there are around 13,000 premature deaths per year due to coal, and 23,000 annually in Europe. Coal is nowhere nearly as safe as people think. So far, nuclear power has a death rate of 0.07 deaths per terawatt-hour of electricity, or about 1 death per 14 years. That figure is enhanced substantially due to stupidity at Chernobyl. Fukushima has 1 death attributed to it, although there are claims that the stresses of it on those who had to move caused a further 2,200. Up to 2004 (18 years later) 78 died from Chernobyl. This is not good, but it is avoidable.
Current reserves of uranium total 5.3 million tonne, about a third of which are in Australia. However, only about 36,000 t of that is U235, which is what is fissile, and has to be enriched. The depleted uranium waste from the enrichment process goes into armour-piercing military rounds. What happens in most nuclear power stations is the enriched uranium rods generate heat, then have to be taken away to be reprocessed, which involves removing the plutonium for weapons. A long time ago, when I was at school, we had a visiting energy expert who told us that in the future the world would develop breeder reactors, and the enriched uranium would produce more fuel in the form of plutonium than it consumed in making electricity, The need to feed the military complex means that did not happen.
What is possible is a new generation of reactor, based on the fuel being dissolved in molten salt. The reactor is now at thermal equilibrium so it is impossible to have a melt-down – there is nothing to melt. The one catch is the issue of corrosion. That can undoubtedly be dealt with, but we have yet to learn the real long-term issues. China is currently testing one demonstration plant, and it is designed to simply provide the boiling pressurized water to run an existing power plant. The idea is simply the coal-firing is removed, this heat source is plugged in and everything else continues working. As the U238 gets converted to plutonium, it also fissions and generates heat to make electricity. What the surplus neutrons in the reactor do is also to burn “hot” isotopes, so the waste disposal problems are far less. Finally, once going, it can also take thorium as a fuel, and there is far more thorium in the world. Simple fission could keep us going for centuries.
Arguably, nuclear is not “green”. My argument is we either use it or not, but it alone has any chance of providing the levels of electricity we need and replace fossil fuel burning.
Ultimately, fusion power would solve all our energy problems. There is only one problem with it: we do not know how to make it work. There is also one general problem. To change our ways, we shall have to spend a very large amount of money, and basically replace about two thirds of our existing electricity generating infrastructure. The alternative is to do nothing and then rebuild all our major coastal cities when the ice sheets collapse. That is also expensive. We have a choice, but unfortunately our politicians seem to want to do nothing and leave the problem for our grandchildren.