Solar generated electricity, along with wind power is cheaper than fossil fuels. These renewable energy sources are being deployed rapidly at many scales. We’ve been working toward these developments for the last seventy years.
Solar power has one very challenging feature: it is, by definition, intermittent. We can generate all the power we want—while the sun is shining. This creates a difficult problem for existing 24/7 grid systems: how to economically integrate vast amounts of intermittent generation into a reliable, always there, grid.
Obviously, batteries and other storage technology can help smooth out the supply, and there is plenty of work on these technologies. Even so, grid operators will still want to work with a mix of sources, and getting the mix right is a complicated optimization problem. Different technologies have their own characteristics, and economics.
The basic idea is that the economics of cheap and abundant solar and wind energy turn conventional wisdom on its head. Grid operators are generally constrained by the immense costs of building and running generating capacity. Therefore, it is economically necessary to build only “enough”, and to fully use generators. Idle plants are a financial disaster.
The new study shows that, in the case of intermittent solar power, it can be cheaper to “optimally” over build and curtail. The basic idea is that it is cheap enough to build enough PV generation so that most of the time you have enough to meet the target load. This means that a lot of the time, you have “too much”, more than needed–so you just don’t use the excess. This concept works even better with a combination of solar and wind.
Basically, this approach deliberately “wastes” both capital plant and output. So how can this be good?
The main point is that when renewable energy is cheaper than alternatives, it is cost effective to “waste” the renewable resources in return for minimizing the use of costly alternatives. (Note that this also upends the “renewable augments conventional fuels” paradigm, for a “conventional sources fill gaps in renewable generation” apporach.)
The thrust of the paper is modelling to demonstrate that an optimal combination of overbuilding and curtailment can be cost effective for grid operators. Their study indicates that a solar-only system is “feasible”, but including wind and small amounts of natural gas could be even cheaper. (The details will depend a lot on local conditions.)
I like this approach, if only because it leans on the idea that “solar power is almost free”. Nothing is free, but sunlight is as close to infinitely free as we are likely to get.
In this approach, the economics of the renewable generating plant (as opposed to the whole grid) are a bit more complex, because the overproduction isn’t sold to the general market. But, as the researchers point out, this “unused” electricity is still valuable, and can add additional value to the overall system. They suggest that “curtailed” production might go to something like desalinization or generating hydrogen for fuel.
- Marc Perez, Richard Perez, Karl R. Rábago, and Morgan Putnam, Overbuilding & curtailment: The cost-effective enablers of firm PV generation. Solar Energy, 180:412-422, 2019/03/01/ 2019. http://www.sciencedirect.com/science/article/pii/S0038092X18312714