Baseload
The term "baseload" refers to electricity that has to be available 24/7. This is a challenge for intermittent energy sources like solar and wind.
How much baseload power do we need?
Most optimistically, only about 10% of global energy demand has to be baseload. The other 90% consists of industry, road vehicles, heating, etc. In principle, these could run entirely on energy from peak-supply times of day. For example in a mostly-solar scenario, factories could run entirely during daytime (and maybe even slow down production during cloudy days). Electric vehicles could also be charged during daytime.
Things that truely need baseload power include:
- Lights in homes, buildings, and on city streets
- Computers, TVs, and most home appliances
- Web servers
- Electric trains
Which energy sources can provide baseload power?
- Coal and natural gas power plants - these currently provide most baseload electricity around the world.
- Hydropower - a greener energy source overall, but only viable in some parts of the world. Most hydro power plants that can be built, already have been - with some exceptions.
- Nuclear - currently depends on uranium-235, which is quite scarce. There might just barely be enough if nuclear power is used only for baseloads.
- With enough energy storage, even solar and wind could be converted to baseload power. This is its own challenge.
Adjustability of power plants
Energy demand fluctuates throughout the day, and the energy supply has to adjust to accommodate this.
- Coal and natural gas power plants are the easiest to ramp up or ramp down on-the-fly - although the most efficient natural gas plants (the "combined cycle" type) can't respond quite as quickly.
- Some nuclear power plants can also be ramped up or down; others can't.
- Hydropower can be ramped up and ramped down by controlling the extra reservoirs of water. However, if demand stays high for long enough (perhaps several days), the reservoirs run out and the power plant can't keep up with demand. This isn't generally an issue because demand usually stays high only for a few hours at a time.