Almost the entire optimisation market was built around storage. Wind and solar pose a problem of a different nature — and they are the majority of installed capacity in the Peninsula.
A storage system is a dispatchable asset: you decide when it charges, when it discharges and at what power. Optimisation is a deterministic problem and resource forecast error does not exist.
An intermittent asset is the opposite. You do not decide when it produces. You decide whether to offer, in which market, at what price — and whether, in a given period, it is better not to produce at all. All the decision latitude sits there, and all of it depends on knowing the uncertainty you are working with.
There is a useful asymmetry in renewable assets: going up depends on the resource, but coming down depends only on an instruction. A solar or wind plant in production has, at all times, curtailment capacity available — with no additional investment and no new equipment.
That capacity is downward reserve, and it is a product the system buys.
Today, in the overwhelming majority of assets, it is neither offered nor paid for. It is there, and no one charges for it.
Curtailing only makes sense if curtailing does not mean losing. That is the role of deemed energy: the asset is paid for the energy it would have produced, not only for what it actually produced.
The output that would have existed is estimated from the plant’s own weather station — pyranometer or anemometer — through a conversion function fitted to that specific asset’s history and recalibrated monthly over the hours in which no setpoint applied.
The arrangement presupposes the ability to control the asset remotely. Without that, the general imbalance regime applies.
A battery next to a renewable plant changes the problem, and for the better: it adds a degree of freedom to an asset that had few. We work with those assets, and the battery enters the same decision as everything else.
What we claim is something else: that there is a great deal to do before there is a battery, and that this work is currently left undone in most Iberian plants.
The Peninsula combines two conditions that few markets have at the same time: high renewable penetration and a fast-growing system services market. The first creates the problem; the second pays for the solution.
wattimize weather →We process the plant’s history, separating the weather effect from the dispatch effect, and quantify the result.