this post was submitted on 16 Nov 2024
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Anon questions our energy sector (slrpnk.net)
submitted 1 week ago by [email protected] to c/[email protected]
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[–] [email protected] 3 points 1 week ago (1 children)

Source (1)

Later this month the LA Board of Water and Power Commissioners is expected to approve a 25-year contract that will serve 7 percent of the city's electricity demand at 1.997¢/kwh for solar energy and 1.3¢ for power from batteries.

The project is 1 GW of solar, 500MW of storage. They don't specify storage capacity (MWh). The source provides two contradicting statements towards their ability to provide stable supply: (a)

"The solar is inherently variable, and the battery is able to take a portion of that solar from that facility, the portion that’s variable, which is usually the top tend of it, take all of that, strip that off and then store it into the battery, so the facility can provide a constant output to the grid"

And (b)

The Eland Project will not rid Los Angeles of natural gas, however. The city will still depend on gas and hydro to supply its overnight power.

Source (2) researches "Levelized cost of energy", a term they define as

Comparative LCOE analysis for various generation technologies on a $/MWh basis, including sensitivities for U.S. federal tax subsidies, fuel prices, carbon pricing and cost of capital

It looks at the cost of power generation. Nowhere does it state the cost of reaching 90% uptime with renewables + battery. Or 99% uptime with renewables + battery. The document doesn't mention uptime, at all. Only generation, independant of demand.

To the best of my understanding, these sources don't support the claim that renewables + battery storage are costeffective technologies for a balanced electric grid.

[–] [email protected] 0 points 1 week ago (1 children)

It looks at the cost of power generation

Yes.

But then you added the requirement of 90% uptime which is isn't how a grid works. For example a coal generator only has 85% uptime yet your power isn't out 4 hours a day every day.

Nuclear reactors are out of service every 18-24 months for refueling. Yet you don't lose power for days because the plant has typically two reactors and the grid is designed for those outages.

So the only issue is cost per megawatt. You need 2 reactors for nuclear to be reliable. That's part of the cost. You need extra bess to be reliable. That's part of the cost.

[–] [email protected] 2 points 1 week ago* (last edited 1 week ago) (2 children)

But then you added the requirement of 90% uptime which is isn't how a grid works.

I'm referring to the uptime of the grid. Not an individual power source.

Assume we've successfully banned fossil fuels and nuclear, as is the goal of the green parties.

How much renewable production, and bess, does one need to achieve 90% grid uptime? Or 99% grid uptime?

If you want a balanced grid, you don't need to just build for the average day (in production and consumption), you need to build for the worst case in both production and consumption.

The worst case production in case for renewables, is close to zero for days (example). Meaning you need to size storage appropriatelly, in order to fairly compare to nuclear. And build sufficient production so that surplus is generated and able to be stored.

If we're fine with a blackout 10% of the time, I can see solar + bess beating nuclear, price wise. If the goal instead is a reliable grid, then not.

As an example: take Belgium. As a result of this same idea (solar/wind is cheap!) we ended up with both (1) higher greenhouse gas emissions and (2) costlier energy generation, as we now heavily rely on gas power generation (previously mainly russian, now mainly US LNG) to balance the grid. Previous winter we even had to use kerosene turbine generation to avoid a blackout.

[–] [email protected] 1 points 1 week ago* (last edited 1 week ago) (1 children)

How much renewable production, and bess, does one need to achieve 90% grid uptime? Or 99% grid uptime?

About 115% to 130%. Depending on diversification of renewable sources and locations. The remains are losses in storage and transport obviously.

But shouldn't you actual question be: How much storage is needed?

For a quick summary of those questions you can look here for example...

[–] [email protected] 1 points 1 week ago (1 children)

What would 130% grid uptime even look like? 475 days a year without blackout?

I think we're talking about different things.

[–] [email protected] 2 points 1 week ago* (last edited 1 week ago)

130% production on average, with excess being stored, minus losses in conversions, transport and storage = 100% demand covered all the time.

Or the longer version: For a stable grid I need to cover 100% of the demand in next to real-time. This can be achieved with enough long- and short-term storage, plus some overproduction to account for storage losses. The 115% to 130% production (compared to actual demand) are based on studies for Germany and vary by scenario, with the higher number for the worst case (people strongly resisting all changes to better balance consumption and south Germany keeping up there resistence to diversify by only building solar while blocking wind power).

The question now is: How much storage do I need? And that answer is varying by much greater amount based on scenario (for example between 50 and 120 GW capacity needed as electrolysis for long term-storage or battery storage between 50GWh and 200GWh).

[–] [email protected] 0 points 1 week ago

Yes you have to build for worst case. That's what I already said.

You are comparing overbuilt nuclear but acting like bess can't be over built too. That's why the cost of storage is the only important metric.

You need an absolute minimum of 2 nuclear reactors to be reliable (Belgium has 7). That doubles the cost of nuclear. But it doesn't matter because that's factored in when you look at levelized cost. You look at cost per MWhr. How reliability is achieved doesn't matter.

Bess is $200 per MWhr.