California breaks 1 GW energy storage milestone
pv-magazine-usa.com
pv-magazine-usa.com
Most electrical grids experience peak demand in the early evening when people come home from work, turn on lights, cook dinner, etc. This peak period is usually on the order of 4 hours. This early evening period is also when solar output drops toward zero.
Energy storage projects in CA are currently generally provisioned for 2-4 hours of storage to ensure a good match to this daily evening demand peak and dropping solar output. Storage is still expensive so it doesn't make financial sense to add capacity that isn't going to be used most days.
Some of these projects publish detailed information about power and energy. Others just publicize power, but given what is known about the California market their energy capacity can still be estimated to a reasonable degree.
I liken it more to distance vs speed. Power, like speed, is a rate, in particular the instantaneous rate at which energy is transferred.
Expressed using the same scheme we use for speed (distance per time : power per time), power is watt-hours per hour (or 0.0036 megajoules per hour).
I'm guessing we express power differently because James Watt codified the standard unit for power and the standard for electrical energy came from the time-integral of his definition of power.
This makes perfect sense because most of the measurements of things we own or consume are counted in units like area, volume, and energy, which are inherently more tangible than an instantaneous rate like "power". Speed is a bit of an exception to this, but I think that has to do with the ubiquity of speedometers in cars.
To the extent that people broadly understand power as distinct from energy they tend to do so in a mechanical, not an electrical context, and in less precise terms ("That's a powerful truck"). However, some exceptions to this are light bulbs and electric space heaters, where people generally understand power as being proportional to brightness and heat output.
In a way, it's an incredible testament to the engineering of electrical systems that people have been able to largely ignore the difference between power and energy, or just need to flip a circuit breaker if something exceeds a limit.
Also, Li-ion and LiFePO4 batteries have a much different discharge curve than earlier chemistries [1], with much more constant voltage up to 80% discharge.
1. https://www.powertechsystems.eu/wp-content/uploads/sites/6/2...
Assuming 12V, that's about 400Ah*12V=4800Wh of storage. 4800Wh/400W = 12 hours to charge those, which seems reasonable for an RV. The thing that seems a bit oversized is the 3000W inverter.
Based on the energy mix, it looks like lost coal capacity has been replaced with solar and other green energy, and demand has gone down relative to population because of efficiency initiatives and rooftop solar for the largest home consumers (rich people).
I'll bet demand falls even faster as home energy storage gets cheaper and more prevalent.
Transmission is crucial for flexibility in balancing generation and consumption, as well as optimizing storage utilization. You can also assume there will be times you’ll throw away (curtail) clean energy as it’s cheaper than it would’ve been to store and then deliver it, but you still need that capacity available at other times (seasonal variability).
> Fortunately, 2,000 MW of energy storage capacity is coming online by August 1, per the California Public Utility Commission. Much of this capacity will have four hours of battery energy sitting behind it, nearly 8,000 MWh in total.
That's 2 GW of power delivery backed by 8 GWh of storage.
I think this is where the confusion starts: if someone talks about "energy storage capacity", my first association is the amount of energy that can be stored, not the rate at which that energy can be discharged from the storage (i.e. power).
We could call them power capacity and energy capacity. This system can deliver 2000MW for four hours, or 1000MW for eight hours, but can't deliver 4000MW for two hours, because that exceeds the power capacity.
We don't state that a car with a 100mph top speed has a 100mph capacity.
What are our power sources available to the grid today? Nuclear, Hydro, Energy Storage.
What are the capacities?
Nuclear capacity is 1 GW
Hydro capacity is 1 GW
Energy storage capacity is 2 GW
The battery energy storage is 8GWh with a power capacity of 2GW. There is no such thing as a power storage capacity, because power is a rate. However, the storage may have a power capacity. pedantic, I know.
Watts are joules / second, so watt * hours cancels time on both sides, it's just energy. Watt-hours are more convenient than "raw" joules only because we tend to be more interested in how many hours a battery will last at a given wattage, not how many seconds it will last.
So energy capacity is correct, it's the amount of energy (not power) one can store in the battery.
Edit: I read this as though you were replying to me, not the comment I was replying to. Swimming upstream, I see that, yes, "energy storage capacity" isn't in watts, but rather watt * hours, but I agree with @renewiltord that it's easy to understand once you factor in that journalists, for the most part, never took physics.
The numbers have the units next to them, after all.
The right answer is to use power and energy capacity respectively if you’re talking to lay people but this publication is talking to people who disambiguate based off the units pretty easily.
Nuclear capacity/wind capacity/Energy Storage Capacity. Three different delivery methods for power. That’s how they’d read it at the end of the sentence.
But anyway, the trick is to perform either unit disambiguation or perform one sentence lookahead.
And finally, think of it as no different from using the summation convention in tensor notation. You read it and you’re like wtf but that’s because you’re not the audience and you lack the context to get it.
> Fortunately, 2,000 MW of electricity is coming online by August 1, per the California Public Utility Commission. Much of this will have four hours of battery time sitting behind it, nearly 8,000 MWh in total.
Or alternatively, by using the correct physics terms where applicable:
> Fortunately, 2,000 MW of peak power capacity is coming online by August 1, per the California Public Utility Commission. Much of this capacity will have four hours of battery energy sitting behind it, providing nearly 8,000 MWh of energy in total.
But as is, the author provided the worst of both worlds. To me as a reader, I read "2000 MW of energy storage capacity", stumbled over that, then read on to "8000 MWh in total", understood that that is actually the storage capacity, then had to go back to "2000 MW" to understand that they meant "power", not "energy", to make sense of this whole two-sentence section.
So yes, this all does make sense. After reading it multiple times, some of which are back to front. The information is in there, but it certainly isn't clear or up-front.
Well the new hybrid inverter from phocus is supposed to use the generation when grid outside is down internally at home and that opens up a lot of possibilities.
Been thinking about using solar water heating to reduce electricity consumption but that is a big project.
Batteries are still expensive in india. Lithium ion is prohibitively expensive than lead acid. Agreed it pays in time of life but still.
Edit: anyone know if I can incorporate phocus inverter into home assistant ? It has ble so some sort ?
The amount of energy that can be stored in California's pumped storage projects is enormous, measured in hundreds, if not thousands, of GWh, but that's mostly irrelevant to this discussion.
Is it irrelevant? As another thread mentioned, how long you can provide that power for that for and how fast you can replenish capacity seems relevant for its usefulness buffering solar for after hours.
I'm pretty unread on the energy storage situation so your insight or any good resources are very welcome!
What kind of home PV solar panels should a person ask a contractor for? How do you know they're giving you quality rated panels?
Gonna be a gnarly market.