Solar Duck Curve
The "solar duck curve" is caused by an oversupply of solar PV power during the middle of the day, followed by the early evening demand spike. Here in California, the PV oversupply has become chronic and can almost be seen year around. As we enter spring time it is even worse. When there is an oversupply, wholesale electricity prices drop and can even go negative. That is, we will pay generators to cut their output. In Europe, situations like that will result in retail electricity rates to be negative. But here in California we have no correlation between oversupply and retail rates.
The image is an illustration from CAISO of such an oversupply scenario. At the time of oversupply, all "behind the meter" PV systems are busy producing, while utility generators such as gas, and PV are being called on to scale back. In the last few years we have been busy installing grid connected batteries. Currently there are about 10GW of connected batteries with a capacity of 40GWh. This has helped reduce the duck curve problem tremendously, but it seems that as we add more batteries, more PV power generation is also added - and we still have massive solar PV curtailment.
This is the root of the problem that California's PUC has been tasked to sort out. There are way too many issues related to this to cover in a simple post like this, but I would like to make two points. 1) When we have an overproduction period, we have the cleanest electricity. 2) We are not rewarding customers to consume more. In fact, we still have the old incentive policy from the past where we incentivize/rebate nighttime consumption. This is absurd.
Add to that our new EV fleet. We have mandated all new housing have EV charge points. At the face of it, that is cool. However, when you consider residential EV charging will mostly take place during nocturnal hours, such policy will only make the situation worse.
Instead, how about if we charge all EV's while at work? How much of an impact will that have on the duck curve? We have around 1.5mil EV's on the road. Assume a daily usage of 20 miles, and average efficiency of 3kWh/mi, and you have a EV charging grid load of 10GWh. It will reduce a good chunk of the oversupply.
I have my doubts about such a policy becoming real, but if you are like me, and would like to reduce your CO2 footprint, then try to use electricity during daylight hours.
