I wonder if there's a way to remove CO2 from the air with surplus electricity without a half-billion dollar plant. That would be a win for everyone. It operates when the wholesale price of electicity drops below its threshold, perhaps only 4-6 hours per day, so would have to be a pretty cheap fixed cost.
Power Worth Less Than Zero Spreads as Green Energy Floods the Grid
71–80 of 419 posts
Re: Power Worth Less Than Zero Spreads as Green Energy Floods the Grid
#72Can someone with a microecon background explain how this is possible? (My guess is that consumption is somehow completely independent of unit price and that its also inelastic?)
Generators are turned on/off via pricing signals, in advance a generator makes known how much money /MWh it will take for them to turn on and scale to various levels of output.
A control dispatch system monitors/estimates demand and sends pricing signals to the generators in an effort to match that demand. So reducing price when there's oversupply and increasing price when there's undersupply in an effort to balance load demand and generation supply.
Nuclear and coal plants produce a baseline output when they're on and take a long-time to turn on/off so their baseline bid is nearly zero. As long as they get a penny for a MWh they'll stay on because they make their profit in they high demand hours.
In a system without wind (solar is less of an issue because it's easier to predict) this design works fairly well at moderating power generation relative to demand.
Adding a renewable that's not properly predicted to this system for a few hours leads it to try to "turn off" some baseline generation if these hours are already low generation. If that baseline is priced close to zero then the pricing has to go negative.
Hope that makes sense.
Re: Power Worth Less Than Zero Spreads as Green Energy Floods the Grid
#73Earlier quoted context omitted.
It's likely a short-term problem. There are plenty of ways to fix it (besides the one you mention, just shut down coal & oil power plants for good and replace them with technologies like natural gas or hydro that can easily react to spikes in demand), but all of the fixes require capital investments and time to build factories & tooling. Basically this is a problem because a bunch of existing incumbents are probably…
Is the responsiveness of an oil plant so different from a natural gas plant? Why? They're both essentially a furnace fueled by a flow of combustible fluid, right?
NG plants tend to use gas turbines, which can ramp very quickly indeed. Steam plants are a lot slower (thermal stresses and whatnot).
Very little electricity is produced with oil, BTW. Steam plants are usually coal or nuclear.
Re: Power Worth Less Than Zero Spreads as Green Energy Floods the Grid
#74Earlier quoted context omitted.
With your desal example, I think a bulk of the energy requirement for desalination is building a pressure differential. That seems like it would be very easy to parallelize.. you don't need full on duplicative Desalination sites, you just need pressure vessels that can store large amounts of compressed air to take advantage of energy gluts.
I thought they used electricity to deionize salt water, the salts are already dissociated into positive and negative ions, so pass a current through the water, and every now and then raise the electrodes out, mechanically scrape it off or reverse current in dump brine to remove the ions...
Doesn’t work. By the time you’ve moved any non-negligible amount of ions, you’ve built up an insane amount of charge and hence voltage. That voltage will be impossible to work with, not to mention many orders of magnitude higher than the voltage needed to split water into H2 and O2.
One mole of singly charged ions is ~1e5 Coulombs. At an insanely high capacitance of 1 Farad (which you’ll never see in such an application) that’s 100kV of static charge by the time you move a few grams of salt.
This is why you essentially never encounter ions by themselves.
Re: Power Worth Less Than Zero Spreads as Green Energy Floods the Grid
#75Earlier quoted context omitted.
With your desal example, I think a bulk of the energy requirement for desalination is building a pressure differential. That seems like it would be very easy to parallelize.. you don't need full on duplicative Desalination sites, you just need pressure vessels that can store large amounts of compressed air to take advantage of energy gluts.
I thought they used electricity to deionize salt water, the salts are already dissociated into positive and negative ions, so pass a current through the water, and every now and then raise the electrodes out, mechanically scrape it off or reverse current in dump brine to remove the ions...
There are two major ways to do it at scale: Distillation, or reverse osmosis. In large plants they are actually energy competitive - reverse osmosis needs pumps to build pressure. Distillation needs energy to boil water, but then that steam is cooled down with the input water which gets heated in turn.
I'm not aware of any large scale ion plants, I don't know if the chemistry can work or not.
Re: Power Worth Less Than Zero Spreads as Green Energy Floods the Grid
#76Can someone with a microecon background explain how this is possible? (My guess is that consumption is somehow completely independent of unit price and that its also inelastic?)
Consumption and production are both inelastic and storage costs are high.
Traditionally when a producer produces more of a good than consumers want to buy, the price drops, consumers buy more, and producers produce less. If consumption & production are both inelastic, consumers won't buy more and producers can't produce less. The excess goes into inventory, where it's treated as an asset and then sold (often at lower prices) when supply and demand equilibrate.
You can't put electricity into inventory, at least not without batteries or similar tech, which cost money and leak charge. Hence, if you produce extra, you have to pay someone to manage the storage or usage of that extra current.
There are a few other industries that function like this. Garbage is a big one: you have to pay someone to take your garbage because demand for garbage is much less than supply and storage has non-zero cost.
Re: Power Worth Less Than Zero Spreads as Green Energy Floods the Grid
#77I don't truly understand this "problem". I understand storing the energy in batteries is currently very expensive economically and materially. However I believe there are plenty of "goods" (irrespective of if they are bulk materials, or partially processed products) which have a high processing energy per volume ratio (this does not need to be recoverable stored energy). Allow me to give an example: currently we have…
You "currently" have a drought, but otherwise you have plenty of water, so a desalination plant isn't a wise investment (yet). Also keep in mind that these are energy spikes that cause negative prices, whereas most industrial uses need a constant and even supply. These spikes are countered by periods of little to no energy . This is the biggest problem with (most) renewables, they cannot entirely replace coal or nucl…
> Energy storage (at cost) is an unsolved problem.
Super-true. It's actually pretty fascinating how it's currently done in the grid; storage of energy is often done by converting it (at significant efficiency loss) to a mechanical format.
Those formats can get very creative---traditional is "pump a bunch of water uphill into an artificial reservoir," but in areas where big dry mines are available, capping the mine and pressurizing the air inside is also used, which feels super-weird but apparently works?
Re: Power Worth Less Than Zero Spreads as Green Energy Floods the Grid
#78I don't truly understand this "problem". I understand storing the energy in batteries is currently very expensive economically and materially. However I believe there are plenty of "goods" (irrespective of if they are bulk materials, or partially processed products) which have a high processing energy per volume ratio (this does not need to be recoverable stored energy). Allow me to give an example: currently we have…
With your desal example, I think a bulk of the energy requirement for desalination is building a pressure differential. That seems like it would be very easy to parallelize.. you don't need full on duplicative Desalination sites, you just need pressure vessels that can store large amounts of compressed air to take advantage of energy gluts.
If you can store large amounts of compressed air to take advantage of energy gluts, it's probably better to just storing it and generate electricity to sell on the market when the price is high...
Re: Power Worth Less Than Zero Spreads as Green Energy Floods the Grid
#79I don't truly understand this "problem". I understand storing the energy in batteries is currently very expensive economically and materially. However I believe there are plenty of "goods" (irrespective of if they are bulk materials, or partially processed products) which have a high processing energy per volume ratio (this does not need to be recoverable stored energy). Allow me to give an example: currently we have…
Capital costs vs. marginal costs. You're going to build a $100M desalination plant and run it for three hours a day? That's a ton of money sitting idle most of the day, far more than what is recovered with zero operating costs. (This is called the utilization factor -- how long a piece of equipment is used vs. staying idle) Ideally you want useful processes with low capital costs and expensive marginal/energy costs.…
A desal plant is a useful thing and can be run around the clock off traditional energy sources. The "free energy" hours would help lower the costs.
I can even imagine a SETI-like application where people who over-generate power are able to donate it to causes of their preference...
Re: Power Worth Less Than Zero Spreads as Green Energy Floods the Grid
#80Surely Bitcoin miners will snatch up these opportunities soon. Cheap electricity can be translated into money if you have the mining equipment.
Agreed but its a weird transaction system that works better on windy days. :)
Interesting point! It seems to me that the economy regularly takes a beating on extreme weather days. However, these things are factored in. For e.g. whenever there is a cyclone brewing near the Louisiana coast, gas prices go up.
If there is a blizzard, people stay home. Then there are forest fires - these might cause property destruction and have a long term health impact - directly and indirectly affecting the economy. Although the exact timing of these events are not predictable, a huge part of our economy - the insurance industry tries to factor extreme weather into account. Similarly, mining during windy days should even out, given enough players are invested.