Thesis Update: Wind Power and Demand Response in Denmark and Hawaii

Today I signed up 500 MW of demand response customers in Denmark.

Well, simulated customers.

My thesis, you may recall, is on integration of wind resources in Hawaii. Denmark is a pretty good analogue for Hawaii since it has lots of wind and a similar number of thermal generators. There is also a really good stochastic unit commitment model for the nordic countries called WILMAR. I am in the process of modifying WILMAR so that it can simulate Hawaii, but before that I wanted to see how Denmark would behave if it had a lot of responsive demand and 20% wind.

Rather than treating responsive demand as actual curtailment, I model it as another type of generator and leave the demand function unchanged. On the graph above, you see coal/oil/gas powerplants in grey, wind in green, and demand response in red. The x-axis represents about two weeks of operations. To model demand response, I am considering it (to first approximation) to have instantaneous spin-up time, an infinite ramp rate, and no startup/shutdown cost. Its marginal cost is higher than all other generators in the market.

Given these characteristics, I expected DR to be used relatively infrequently when the wind came in less strong than predicted. Not so - the optimization seems to like the flexibility of demand response and dispatches it all the time. I need to look deeper into my assumptions about DR having zero startup cost. (Furthermore, HECO rules promise that DR won't be called for longer than 2 hours at a time. Obviously that still needs to be coded into the constraint set.)

Other interesting observation: that large dark grey band is coal. For all of its world-class wind penetration, the country is still running a lot of dirty coal. You see the cleaner natural gas plants (light grey) kick in mostly when the wind dies down such as on 7/3. Running coal and wind feels to me like eating chocolate cake and diet coke to balance it out. I'd be interested in calculating the carbon-intensity of denmark's dirty/clean hybrid and comparing it to New England's pretty-clean natural gas sector. (Also: 100% wind on the night of 7/12! Go Denmark!)

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