"Curtailment of PV" or revenge of the Orphan Watts...

The famous uneven distribution of the future prompts us all to look around for what might be the shape of things to come. Germany and Hawaii are both at the leading edge of solar PV uptake. So I sat up and took notice when I saw this:

"A recent analysis finds that a new German program offering up to 660 EUR/kW subsidy for storage tied to PV will not lower battery payback periods enough to induce new investment.(10) Germany’s solar incentives now require PV systems to have a curtailment capability, to allow shut-off during periods of grid instability.(11)

here are the citations:

10 Bloomberg New Energy Finance. “Will Germany’s energy storage subsidy spur investment?” London. (2013) p. 1.
and 11 Fulton, M. and Capalino, R., “The German Feed-in Tariff: Recent Policy Changes.” New York: Deutsche Bank (2012) p. 21

(I found it in the FOCUS FOA from ARPA-E (link later in this post)

So... what is "curtailment" in the context of PV? Curtailment is throwing away energy that cannot be matched to demand at that moment (Electricity has a fierce stale date: basically immediate.) Because of the unbidden rise and fall of the PV output it cannot easily be responded to by the various base-load supporting generators. Those generators need to ramp up and down. Those are mostly not built for throttling etc.

Down in the weeds it gets ugly. Here is a pretty good paper on it in the context of storage of CSP (Concentrating Solar Power - the current term for high temp solar thermal collection): Enabling Greater Penetration of Solar Power...

The FOA that tipped me off to the issue is here at ARPA.

Load management (and yes, storage) is looking like a great place to be. The smart grid cannot come soon enough if we hope to keep the gains that come from PV and other renewables.  For instance: freezers that go extra-cold when there is spare electricity available (a prepaid expense.) How about a clothes washer that sits waiting to pounce on extra watts? Same for a dishwasher and so-called "vampires" the small standby loads and converter boxes - if they could get a tiny bit of smarts they could wait for the scrap watts. OH I like that, "scrap watts." Or how about, "orphan watts." I'll keep working on that. What do you think?