Topic: Modeling Large-scale Renewable Electricity in LEAPSubscribe | Previous | Next
David Von Hippel 5/25/2018
A colleague has reached out to me with an interest in using LEAP to determine if, and when, renewable electricity generation capacity, and particularly solar PV capacity, has risen to a level where the grid in a given area cannot provide peaking power fast enough as the renewable generation decreases, for example, as the sun goes down during a summer peak. It seems to me that the load shape function--either expressed for the entire electricity load in an area or using individual load shapes on a demand-device by device basis--could be used, along with load shapes that describe the availability of solar PV power and other generators on the system. Has anyone else done or heard of anyone else doing this kind of analysis with LEAP? My second (related) question is, when modelling the growth of renewables (especially solar), what LEAP outputs would one used to be able to identify when peaking power resources become insufficient under particular generation expansion plans? Thinking out loud, I guess if one did modeled capacity and demand with yearly shapes (in an extreme example, on an hourly basis), one would be looking through the results of LEAP runs for periods of capacity shortfall, as indicated by negative reserve margins or generation shortfalls, and looking at the timing of same. Then the high-renewables scenarios would be modified to change the electricity resources available (for example, by providing peakers or storage) in order to bridge those gaps. Any feedback on this issue would be appreciated!
Jason Veysey 5/31/2018
These are good questions, and ones that we're increasingly addressing in the LEAP modeling we're doing at SEI. With regard to the first, we have used timesliced availability curves for PV and other generators, and coupled them with load shapes to explore how other resources must backfill when the sun goes down. We've built models that respond to the intermittency of PV (and other variable renewable energy sources) with a combination of other generation (e.g., gas), storage (using a customized version of OSeMOSYS and some other enhancements), and imports. This modeling has generally used hourly timeslices, so it's been fairly finely resolved.
There are two potentially important factors in responding to PV intermittency that aren't yet well supported by LEAP: ramping/shutdown times for generators and transmission & distribution constraints. We are actively working on adding these capabilities. We're also working on making storage modeling part of the regular LEAP distribution.
As for the second question, the answer depends on how the model is configured. I'm assuming that by "insufficient" peaking resources, you're referring to generation, not capacity. Shortfalls in generation will fall out of the model as imports or unmet requirements, depending on the properties of the transformation module's output fuel and the fuel's properties in the resources branch.
I hope this helps - feel free to follow up with any other questions.
David Von Hippel 5/31/2018
Thanks very much, Jason, and it's great to hear that SEI is actively working on enhancements that would help with modeling these issues, especially the addition of capabilities for modeling of energy storage. Yes, I guess that I was suggesting that unmet energy (generation) requirements (or, as you say, import) would be an indicator of insufficient back-up for solar PV and other intermittent renewables. Presumably, the way that one would operationalize the investigation of whether or not back-up resources (or storage) were sufficient would be to run the model (with finely time-sliced load curves) and look to see which years and time slices show unmet generation, then adjust supply and/or demand for electricity until those unmet requirements go away for the scenario under study?
As a follow-up question, I am wondering what you (and/or others) think of the following idea, and apologies in advance if my description of the idea is a little unformed. Given that full-year annual load and/or output data by hour might be difficult to obtain in some areas, and/or the use of hourly data over the full year might slow down calculations significantly (that's a guess), I'm wondering whether it might be possible to prepare a model that had hourly load shapes for electricity demand and generation for only one or a few critical periods during the year--a summer weekday, for example, for a summer-peaking utility, or a winter weekday for a system with a lot of electric space heating load--but use a much less detailed load shape model for the rest of the year. That way one could (maybe) focus on the times when problems are likely to occur, but reduce modeling inputs (and the time required for results evaluation). Of course a potential downside of this approach is that the periods that are critical in a given area may shift over the several-decade span of a LEAP model, as the types of loads and supply resources change over time.
Thanks again!