In one of my previous blog posts, I discussed a current issue with wind and solar generation. The problem is that the sources come and they go. Obviously the sun goes down at night time, but solar power generation can also be affected by cloud cover. Wind is very sporadic and frequently stops blowing. The grid on the other hand has a never ending demand for electricity. We can’t just tell people to turn off their refrigerators at night time. In order to compensate for this fluctuating supply of power the grid offsets solar and wind generation by ramping up and down coal and natural gas power plants. By ramping up and down these traditional energy sources grid managers are able to stabilize the power supply. This method is used to compensate for a lack of energy supply from solar and wind, but solar also carries another disadvantage.
At sometimes throughout the year, solar energy generators actually supply the grid with too much energy. This is especially the case on clear spring days. It has caused a lot of problems for grid operators in California and other states with large solar supplies. The problem occurs on cool spring days when there is a lot of solar potential and the supply is really high. At the same time, not many people are turning on their air conditioners because of the cool temperature and there is no need for them. This situation creates too much supply and not enough demand. It leads to grid operators having to rapidly curtail equipment to balance the grid. It is a pain for everyone, and it is also bad for large equipment to cycle on and off again. This quirk in the solar market is known as the duck curve because when you plot a graph of the power demand throughout the day it resembles a duck. The times when the demand is lowest happen to be the times when solar is producing at its highest.
Geothermal energy is a great counter balance to this phenomenon because it is base load generation. In other words, geothermal produces a mostly stable supply to the grid 24-7-365. It results in a much smother energy product compared to the over and under supply often faced by solar power. Any grid that wants to have more renewable energy on it will be much better off if its energy mix includes some geothermal power. Hydroelectric is also a good option for base load generation but I understand that most of the feasible places to locate a hydroelectric plant already have one. Geothermal still has a ton of untapped potential in the world.
Duck Curve Photo Credit: ilsr.org/wp-content/uploads/2014/03/Screenshot-2014-03-25-14.36.08.png