> GW is, however, a characteristic of an energy storage system, and just a valid and important measurement as the amount of energy it stores.
Wrong.
The watt is a measure of power, not of stored energy. These are different physical notions. So, yes, you could say that some storage facility can output up to so many GW, but that's actually a measure of how much energy per second can exit the system when it's being used.
The proper unit for measuring an amount of energy that's stored in the system is the Wh (or its multiple the GWh), which has the same dimension as the joule, which is the standard unit of energy.
GW is like how many liters of water per second can exit the storage tank when it's being emptied. GWh is like how many liters of water total are stored in the full tank. And yes, both are important when designing a battery system. But saying "GW is [...] a valid and important measurement as the amount of energy it stores" would fail you high school physics.
GWh is static energy (or simply - energy). GW is energy moving from point A to point B, which is power.
Here's a brief introduction to the basic meaning of these terms:
GW is a very important characteristic of an energy storage system, especially as a ratio of GWh. A technology could store 100TWh, but if it can only release 1kW, I'm not interested.
The comment you replied to said "just a valid and important measurement as the amount of energy it stores". The comment didn't say power was the same thing as energy, it says that the power is as important as the energy. I don't think this would fail high school physics.
> GW is [...] a [..] measurement as the amount of energy it stores.
Which doesn't parse. If the text read "of" instead of "as", I might agree with you. As it stands, it doesn't correctly parse either way. Given the full context of the statement, the more likely original intention was that:
> GW is [...] just a[s] valid and important [a] measurement as the amount of energy it stores.
At no point do you actually say what was wrong about what you quoted. What do you feel is in error?
>GWh is static energy (or simply - energy). GW is energy moving from point A to point B, which is power.
Yes, obviously. This is HN. Generally it pays to assume that people know what they are talking about around here.
It may be that you don't care about the power rating of the storage instance, but a utility does! They care about the power rating just as much as the total storage amount, as they are both essential design parameters. Particularly in the case of lithium ion, since many applications use discharges or charges less than an hour long (lithium ion batteries are typically designed with a W:Wh ratio of 1:1 - 1:4).
The original article is citing a market report from IHS Markit. Now, I can't find the particular news release for this one, but IHS Markit uses both terms GWh and GW when talking about storage, and as market researchers if they were messing that up it would be a worthless report. So lets look at one of the recent reports:
> This was largely a result of over 100 MW of projects being completed and commissioned in California in early 2017 as part of Southern California Edison and San Diego Gas and Electric’s response to the Aliso Canyon gas leak.
>(CPUC) expedited the approval of around 100 megawatts of energy storage in Southern California Edison and San Diego Gas & Electric territories, in response to the Aliso Canyon blowout.
>Tesla, Greensmith Energy and AES Energy Storage celebrated the completion on Monday of three large-scale lithium-ion battery projects totaling 70 megawatts -- consisting of 20 megawatts, 20 megawatts and 30 megawatts, respectively.
Now, here all megawatts! And the mean it, because these the AES batteries were 37.5MW and 150MWh, and the Tesla battery is 30MW and 80MWh:
So yes, they mean GW and not GWh, and yes, that is a very meaningful statistic when talking about the grid. It's not the only one, and for bystanders, maybe they care about the Wh more than the W, but it's not like you can design a system without known both.
It is obvious from epistasis' comment that (s)he is fully aware of the difference between power and energy, and also that both are relevant properties to consider when designing an energy storage system.
Wrong.
The watt is a measure of power, not of stored energy. These are different physical notions. So, yes, you could say that some storage facility can output up to so many GW, but that's actually a measure of how much energy per second can exit the system when it's being used.
The proper unit for measuring an amount of energy that's stored in the system is the Wh (or its multiple the GWh), which has the same dimension as the joule, which is the standard unit of energy.
GW is like how many liters of water per second can exit the storage tank when it's being emptied. GWh is like how many liters of water total are stored in the full tank. And yes, both are important when designing a battery system. But saying "GW is [...] a valid and important measurement as the amount of energy it stores" would fail you high school physics.
GWh is static energy (or simply - energy). GW is energy moving from point A to point B, which is power.
Here's a brief introduction to the basic meaning of these terms:
https://cleantechnica.com/2015/02/02/power-vs-energy-explana...