Ignoring those benefits makes a portfolio of renewables appear to have less value than they really do, and utilities might choose to build more renewables if they accounted for diversity benefits. Portland General, for example, is working on a wind plus solar plus storage project. Solar plus wind are also complementary resources. Solar plus storage are complementary resources. As you add more and more solar on the grid, the net peak demand gets shifted over but it also gets shorter, which means that it is easier for storage to do its thing and help meet net peak demand. But it also depends on the mix of other resources on the grid. It’s just, and … spoiler alert …Īnd the additive benefits of solar plus storage are also not magic, it’s the value of resource diversity.įor resources such as solar and wind, the ELCC is dependent on other variables, like the hour of the day when net peak demand occurs. It turns out that the magic math of solar plus storage is a bit like the magic of pulling a rabbit out of a hat. So, 0.6 GW plus 1.6 GW equals 2.8 GW! That’s an extra 0.6 GW!įigure NS-3 from Nicolai Schlag’s testimony before the New Mexico Regulation Commission, Case No. Meanwhile, 2.5 GW of storage, on its own, only contributes 1.6 GW of peak load reduction.īut when you pair solar and storage, the combined effectiveness in load reduction is 2.8 GW. Now the company is asking for approval to do the same for its share of a nuclear plant.ĭuring the PNM proceeding, an expert witness testified that if a service territory with approximately 8 gigawatts (GW) in peak load added 5 GW of solar, its net peak load would only see a 0.6 GW reduction. The example below comes from a New Mexico proceeding where the local monopoly utility, Public Service Company of New Mexico (PNM), is already working to replace a coal plant with solar and battery storage. The effective load-carrying capability of solar with storage is actually higher than the ELCC of solar plus the ELCC of storage.
The old phrase “the whole is greater than the sum of its parts” is the perfect description for the magic math for storage plus solar.
The whole is greater than the sum of its parts Wind, solar, storage - each resource is given an ELCC value that the computer models use to make sure the grid can meet future demand. So, when they do their planning, they take this into account. This declining marginal value effect is well-known and well-understood by grid planners. The thing is, the more solar you add to the grid, the less the next MW of solar contributes to net peak demand. Meeting net peak demand is an important part of keeping the lights on so when grid planners do long-term resource planning, they use metrics such as ELCC to make sure they will have enough resources to meet net peak demand five, 10, or even 20 years in the future.įor solar, the ELCC might start around 50 percent - that is, 1 megawatt (MW) of installed solar will contribute a half MW of power during net peak demand. Most frequently these moments are at the time of net peak demand. My colleague Mark Specht wrote a fantastic blog on the subject that you can read here.ĮLCC is a metric used by grid planners to evaluate a resource’s ability to meet demand when outages are most likely to occur. A bit of backgroundīefore we get to the magic math, there is a very important concept that you have to understand first: Effective load-carrying capability, or ELCC.
Well, that’s the magic math of solar plus storage. So, imagine how surprised I was one day to find out that 1 plus 1 doesn’t always equal 2. (What do you mean “y” is SOMETIMES a vowel?!) Not like grammar with all its exceptions to the rules. I find solace and comfort in its consistency.
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