Cal Hates Curtailment

Over the last few years we have seen significant increases in the adoption of solar power, and are expecting to see this growth continue in the coming years as well. We are also all too familiar with the common gripes about solar and how it doesn’t work at night or in a storm, and up to this point the response to these arguments was that these were problems that could be solved with storage, or perhaps some other yet to be developed solution. In reality, up to this point it hasn’t been a pressing issue. In most cases the solar power generated only supplemented the regular supply and was not enough to cover full needs. Now things have changed. It seems solar’s success has caused it to take a step back because a new problem has developed. At an increasing frequency we are seeing solar energy curtailment. This is when the grid, largely propped up by daytime solar generation is generating more power than is demanded. When this happens grid operators are forced to curtail (read waste) much of the solar power as it is either inefficient or perhaps even dangerous to shut down the grids base load stations.

We have seen this happen, mainly in southern California, where solar power is incredibly effective and equally prevalent. And despite having a long way to go on the carbon free energy journey, it seems that we are already hitting the maximum effectiveness of solar power in some regions. The simple solution to this is storage. We already know that solar power stops generating at night and begins to wain off as demand reaches its peak in the phenomenon which has been identified as the duck curve. Named for the drastic jump in required energy generated by other sources as solar power generation going offline. Storage would not only prevent grid operators from curtailing solar power but would also allow them to dampen the duck curve simultaneously. However, as we all know large scale energy storage is not at all a simple solution. Instead, this problem requires a new solution that will prevent wasteful curtailment and prevent a future problem from slowing our progress.

So while all of this is going on, we are also seeing efforts made towards removing internal combustion engine vehicles from the road, in favor of electric vehicles. These have made massive strides, and while it is still a small market share, it is growing. They are sold on the idea that they can be driven within their range during the day and charged at night. Going further new types of vehicles are looking to be electrified because they are “good candidates for electrification” due to the face that they return each night to the same location where they can theoretically be charged. This would apply to fleet vehicles, buses, and farm equipment to name a few.

If we follow through with this and do electrify all of these vehicles we will see a large nighttime electricity load, that for much of its history has been extraordinarily low. In fact this long held expectation is part of the reasoning for electrification of these previously mentioned vehicles as nighttime loads are typically discounted to prevent curtailment of base load stations. So increasing this nighttime usage will likely bring an end to this cheaper nighttime electricity rates, and potentially require new stations to come online, stations that would not be operable on sunny days. Also, if we are referring to areas with large solar industries these are likely to be carbon producing and not economically feasible without extremely high energy prices to make the construction of the plants economical. And, these high energy prices would economically hurt the argument for electrification of the vehicles. So how do we fix this, recognizing that beyond the ability to charge, electrification is a good thing?

The solution is switching as much of this charging to daytime hours where they can be charged real time with surplus solar power. This will increase daytime demand and prevent larger increases in nighttime power demand caused by the growth of electric vehicles. This solution will allow both solar power and electric vehicles to sustainably grow, moving us forward on the carbon free revolution. This however does not come without effort. After all electric vehicles take a long time to charge and cannot be used while they are charging. So how do we charge these cars when the sun is shining?

Charging during the day is currently inconvenient and often less economic, as many customers do have access to lower nighttime electrical rates. So in order to see adoption of day time charging we must offer a better solution to both of these problems. First, we have convenience.  While city planners and environmentalists would love to see greater adoption of public transit and carpooling we must acknowledge the fact that most people drive to work every day by themselves. In fact about 76% of Americans drive into the office by themselves, when combined with carpoolers we see 115 million cars on the road everyday driving to and from work. (Source) Most of these cars perform this task in the morning, then proceed to sit in a parking lot for 8+ hours and do the same thing in the opposite direction. Again, most of these vehicles go to the same lots everyday. In our traditional view, we see this as out of the way and not near its charging spot. However, if charging infrastructure is brought to these parking lots, it is the exact same situation as at home charging.

As for the rates, we have a solution there as well. Using this model we could likely even beat current nighttime discounted energy rates. As with all energy infrastructure, solar panels are bought with the intention of a long productive life. For solar in particular a common lifetime being 25 years. Meaning that these are bought with the expectation that they will be productive for their entire life to offset the financial debt that is taken out to fund their installation. If this power is curtailed the owners of these solar panels are not receiving any income. If we are able to create a new market for this electric power, owners of this solar power would likely offer this power for reduced rates, as any income generation is better than none, and solar panels have relatively low required inputs.

This goes even further, we have to assume that total power consumed will be the same no matter when it is used from a demand side. (Accounting for the intricacies of storage and efficiencies, this is not completely accurate, however still offers a good insight) So any energy that we are able to use during the day would reduce nighttime energy demand that is likely coming from carbon intensive sources. We can use this to determine the theoretical carbon offset allowed by using solar power instead of carbon power we can use this to offset the so called carbon debt. This carbon debt originates from the production of the solar panels. Solar panels do not come out of the ether. They use materials like silicon and glass which require carbon to extract and process. This can be calculated and the carbon debt can be determined. The offset for a solar panel is on the order of 5 years of operation, however if this power is curtailed, for all of the time that the panels are non-operable this is time not spent offsetting this carbon debt.

Offering these chargers at the workplace would also work to ease people into the purchase of electric vehicles and prevent some owners from having to install charging capabilities at home, opening up more apartment dwellers to the opportunity of electric car ownership. 

Obviously this is not the perfect solution, we will have days that are not sunny, and not have excess solar power, and on these days we can either bite the bullet and increase daytime production via other means or use demand control to only charge the cars on the sunny days. This can be done with dynamic rates and software allowing the car owner to decide at what point it makes sense to charge the car. Luckily modern electric cars can support multiple trips to and from the workplace between charges allowing us to maintain this plan for spells of inclement weather. 

In states or regions with strong solar power potential, legislation and regulations must be put in place to mandate the availability of subsidized electric car charging during the day while the drivers are likely at work, running errands or otherwise out of the house. This will limit solar power curtailment and allow for the sustainable growth of electric vehicles without overwhelming the nighttime electric grid. This can be accomplished by legislation or regulations mandating the building of charging infrastructure and offering subsidized rates, a topic which will be further discussed in the future.

Note: This piece is focused around regions with a high capacity for solar power. Such as Southern California, Arizona and much of the Western United States. Similar patterns, though less time dependent by way of solar power could raise questions in other regions which call for similar actions, matching demand to available energy supply.

January 30th 2023