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The article seems to mix storage capacity and instantaneous power. Lithium batteries tend to be able to discharge their stored energy in perhaps 1 to 4 hours (f

The article seems to mix storage capacity and instantaneous power. Lithium batteries tend to be able to discharge their stored energy in perhaps 1 to 4 hours (for instance the Tesla Megapack is between 2 and 3 hours to discharge). Yes batteries are great at flattening the evening peak, when prices presumably spike upwards. That appears to be a good use-case, cycled once a day. Eyeballing the second graph there appears to be around 25 GWh of storage participating on that day, which makes is last equal in terms of energy delivered grouped by type (excepting coal which does not appear to have a line on the graph despite being on the key). Most interesting is the large amount of imports.

api 2y ago
I hardly ever see a popular science article about any kind of energy that gets units right or understands what they mean. Usually they can manage when it’s a conventional power plant by parroting how many “homes” it could power. If it’s anything else forget it.
LUmBULtERA 2y ago
Part of the problem is the source data. In one example the article mentions a battery is 680MW and has 4 hours of discharge. But most of the source data is a LBNL Interconnection Queue report that does not have that data available (the Council of Economic Advisors seems to be using this). I know the source report does not have this data because it is not published in the report and the lab does not have it (I’ve asked them).
- chickenbig 2y ago
  Well, I've eyeballed the capacity of the storage in the system from the graph at around 25 to 30GWh. The CAISO website does allow downloading per-day CSV files of the 5-minute power on a per-day basis. There is also the question of behind-the-meter batteries which presumably do not show up (neither generated solar nor evening peak consumption saved).
epistasis 2y ago
When talking about grid storage, "capacity" refers to power, not to energy, because grid assets are almost universally identified primarily by their power. Changing this tradition for storage assets would be far more confusing than the correct terminology which is used in the article. There's an entire industry, with highly trained professionals, advanced curriculums, etc. etc. etc. that run the grid. It's old technology, but it is still technology. They have chosen to measure battery storage assets primarily by the power capacity, because that's the most important metric for how grids are actually run in practice. Every single time that outsiders are introduced to the grid, there's always some comments that assume that the grid people or the journalists somehow got the usage of MW and GW wrong, but it's actually how it's used in practice by the real engineers who run these things. I have had many many discussions on HN and other forums going over this, but I have not yet found the language to concisely convince people of this fact (and my comment is mostly addressed to other readers of the forum, not to you directly).
- chickenbig 2y ago
  I understand that such a capacity metric might be useful for generation, and somewhat useful for storage. One could see the grid operators having a good grip on the utility of storage to smooth off tv pickup and evening peaks, in full knowledge that the energy stored will run out in a few hours. However the linked article is on theprogressplaybook.com; the about page has the following blurb The Progress Playbook™ focuses on proven ideas for a better world. We cover the policies and projects that are succeeding in driving sustainable development, and that could be replicated elsewhere. This publication is intended to be a resource for policymakers, business leaders, civil society organisations, and ordinary citizens. It is clear that the publication is not aimed specifically at grid insiders, so propagating the grid's argot to a more general audience is at the very least unhelpful.

api 2y ago

I hardly ever see a popular science article about any kind of energy that gets units right or understands what they mean. Usually they can manage when it’s a conventional power plant by parroting how many “homes” it could power. If it’s anything else forget it.

LUmBULtERA 2y ago

Part of the problem is the source data. In one example the article mentions a battery is 680MW and has 4 hours of discharge. But most of the source data is a LBNL Interconnection Queue report that does not have that data available (the Council of Economic Advisors seems to be using this). I know the source report does not have this data because it is not published in the report and the lab does not have it (I’ve asked them).

chickenbig 2y ago
Well, I've eyeballed the capacity of the storage in the system from the graph at around 25 to 30GWh. The CAISO website does allow downloading per-day CSV files of the 5-minute power on a per-day basis. There is also the question of behind-the-meter batteries which presumably do not show up (neither generated solar nor evening peak consumption saved).

epistasis 2y ago

When talking about grid storage, "capacity" refers to power, not to energy, because grid assets are almost universally identified primarily by their power. Changing this tradition for storage assets would be far more confusing than the correct terminology which is used in the article. There's an entire industry, with highly trained professionals, advanced curriculums, etc. etc. etc. that run the grid. It's old technology, but it is still technology. They have chosen to measure battery storage assets primarily by the power capacity, because that's the most important metric for how grids are actually run in practice. Every single time that outsiders are introduced to the grid, there's always some comments that assume that the grid people or the journalists somehow got the usage of MW and GW wrong, but it's actually how it's used in practice by the real engineers who run these things. I have had many many discussions on HN and other forums going over this, but I have not yet found the language to concisely convince people of this fact (and my comment is mostly addressed to other readers of the forum, not to you directly).

chickenbig 2y ago
I understand that such a capacity metric might be useful for generation, and somewhat useful for storage. One could see the grid operators having a good grip on the utility of storage to smooth off tv pickup and evening peaks, in full knowledge that the energy stored will run out in a few hours. However the linked article is on theprogressplaybook.com; the about page has the following blurb The Progress Playbook™ focuses on proven ideas for a better world. We cover the policies and projects that are succeeding in driving sustainable development, and that could be replicated elsewhere. This publication is intended to be a resource for policymakers, business leaders, civil society organisations, and ordinary citizens. It is clear that the publication is not aimed specifically at grid insiders, so propagating the grid's argot to a more general audience is at the very least unhelpful.