> And that is why it is a huge problem for the power companies
It is a problem, but not necessarily in the way you may be thinking. Peak residential power usage is in the evening when solar isn't available. Power companies therefore end up spinning down coal and natural gas during peak solar, then just spinning them back up again as the sun begins to set. [1]
So you haven't replaced the coal and natural gas plants, you're just running them less. This results in higher overall costs, because you pay $$$ to build huge plants then just let them sit most of the day, which results in higher per-watt cost of non-solar power because the infrastructure and maintenance is no longer amortized over whole-day usage.
[1] My friend, a manager of 30 years at a huge mid-west power company
Can validate. The problem with electricity is that there is no large scale storage like there is for other forms of energy like NG and Crude. Until someone comes along and figures out how to store electricity, this will continue to cause grief to power companies. Power plants are really just options, if the price per kWh is at a certain point then it makes sense to spin up or take down a plant and generate power. Adding a bunch of highly variant generation to the grid can make the market more volatile since there could be a lot of up and down with generation facilities.[0]
That said, there will be teething pains but this is a net positive thing that is happening. Growing up I lumped solar into the perpetual 10 years away category. It looks like I am going to see solar be competitive after all.
[0] I implement trading and risk management software in the energy sector, including Crude, NGL, NG, and electic.
Oncor solicited a study that showed that a mass install of Tesla Powerwall devices would be an economic solution to this problem [1], at which point all the generators lost their minds and lobbied the PUCT to prevent Oncor from destroying their market [2] (because of their position as a Transmission & Distribution Service Provider in the market, it would require a change in law for Oncor to be able to implement the project).
[0] Work for a multinational in their energy & utilities consulting practice; above comment is my own.
It's interesting to see the stark contrast between the naysayers that don't have information to back their claims (such as comments sibling to yours), and the people who have looked at current tech and made realistic assessments like Oncor and Brattle.
A lot of people are willing to make confident, but very wrong, statements based on out of date information. It serves to protect entrenched interests and stop competition, but I have a feeling that disruption is far closer than anybody is publicly saying.
Thanks. But it's not realistic and smart because of that, it's realistic and smart because it examines the facts at hand and makes plans instead of handwaving. This is an important distinction.
It's very efficient and it's a great solution overall; the only problem is there are only so many dams we can build, since each one requires drowning a valley.
Though you need less volume if it is only being used for overnight storage rather than long term rainfall storage. For example, to store enough energy to produce 1GW for 1 day (~10^5 seconds) with a head of 100m, use Pt=mgh to work out you need to store:
m = 10^9.10^5 / (10*100) = 10^11 kg of water. = 10^8 m^3
This is not a big reserviour, being 1/20th of the size of Warragamba dam's reserviour (in Sydney). One valley could provide 20GW for a day. Compare that with demand for where I live:
Peak demand for 7.5M people is 9GW, with an average closer to 7GW. One valley could provide overnight storage for over 20 million people, with first world demands (all of Australia). The limitation is transmission and generating/pumping capacity, rather than storage volume.
Gravity potential energy = mgh. Suppose pool is 10 meters up, then you need 239,000 kg of water = 63K gallons or 8400 cu ft. This is a huge pool: 29 ft. x 29 ft x 10 ft.
You could use the city water supply: borrow water through a turbine at night, and return it during the day :-)
Or have pool up very high, for example on a cliff overlooking the Mediterranean:
The outflow from an Auckland homes storm water is not insignificant - an average roof would have something around 5 cubic metres of water come off it several times per year.
I remember a while ago on the show "Let's Get Inventing" (Saturday morning kids show with kids inventing stuff, think it was on TV2), they tried generating electricity from drainpipes, they couldn't get enough power to even power a servo squeezing the trigger on a spraybottle, they had to get a great big firehose from an firetruck to actually generate anything.
Pumped storage is routinely used to store energy. It's not theoretical.
Has Flywheel storage every been seriously used in large-scale commercial applications? Someone mentions it on every energy-storage thread, and I'd like to know if the people suggesting it are just spinning our wheels.
FES is used in non-kill-zone habitable solutions like datacenters, bottoms of passenger trams/hybrid buses and electromagnetic aircraft catapults. The historical issue with FES is unscheduled, rapid disassembly, but carbon/kevlar composites have been shown to have greater integrity with least unsprung structural mass (because you want the most mass as close to the rim as possible to ensure highest moment of inertia.)
FES has 10x specific energy than supercapacitors or batteries with no memory and precise state of charge. Magnetic bearings and hard vacuums make them quite efficient.
The JET fusion reactor in Oxfordshire uses flywheels to provide very large pulses of electricity for short periods of time (a minute or two iirc). The reactor requires too much energy to run directly off the National Grid.
As I recall from a tour I went on of jet 30 years ago there are a large bank of flywheels which spin up over several minutes, these are then rapidly discharged to a bank of capacitors which are then used to power the experiment, I believe the duty cycle was 9 minutes. [1][2]
I believe some electric cars used capacitors to store regenerated electricity from breaking.
"More Ampères please Mister Woodbine." - Road to Welville
Sounds like they use it for high output rather than efficiency though. Still interesting that it has real world applications though. Shows that the technology has potential as well.
It's not even remotely on the same scale. There are three massive utility-level flywheel deployments according to Wikipedia that provide 15 minutes of output.
Edit: Seems the purpose is purely frequency regulation, rather than storage per se.
Better than nothing, but not that efficient. I took the tour of the somewhat mis-named Dinorwig Power Station (really a pumped storage facility) in Snowdonia, Wales. The figures they quoted there put it at about 75% efficiency. It's not really supposed to be for 24-hour power smoothing, more for rapid response to sudden demand; it's a lot faster to open a valve on a turbine than to stoke up a coal plant, and for some spikes (such as the example they quoted on the tour, when everyone puts the kettle on when Coronation Street finishes) you have a 30-second window or so. However, as demand has increased it's being used more and more, and the more it's used the more power we're wasting.
Interestingly, it does not use a dam. There's a natural lake at the bottom of a mountain and a man-made reservoir at the top, and the entire pumping facility is completely inside the mountain; it's not at all obvious that there's anything there at all from the outside. I think about that whenever people moan about the environmental impact, or flooding valleys.
I thought I read that some water districts run their pumps at reduced volume during peak hours and top them off before or after. It's a smaller volume but it's already a solved problem.
And it allows you to push some levers and dials as to whether it's cheaper this year to increase your water capacity or your power capacity. City planners love that kind of thing.
It's a problem, but the nature of the problem varies a lot from country to country. In the Netherlands, we don't have enough renewables yet for this to be an issue (~10%). Once you start getting to Germany's penetration, you start to see some issues with balancing the grid and meeting peak demand. There are more options than just storage, though.
Demand side response is already used in industry to regulate electricity demand and smooth peaks. Smart meter penetration will allow utilities to do this more and more in the residential sector too.
Supergrids are also starting to emerge and indeed, some large grid companies are pushing hard for international interconnects. (China wants a supergrid). Countries are building out more and more HVDC interconnects, both across borders and within countries. Once you have a network of utility scale renewable sources across multiple countries, meeting peak demand becomes more a matter of coordination between grids. Europe for example, is looking like a very interesting area for this right now with planned interconnects between North Africa and Southern Europe.
Since we're all citing employment, I work for a renewable energy company :)
Instead (or rather in addition) to storing power, we can also get better at coordinating demand.
There are already programs for industrial users to get electricity for much cheaper, if they can tolerate power cuts during peak demand. Those programs will become more and more rewarding to join and extend and automate as supply gets spikier.
That's great but then instead of increasing the effective capital cost of the generating plants, you're increasing the effective capital cost of the industrial facilities (by lengthening the time to pay off financing).
It'd be interesting to see a study comparing the two options.
The incentives create a market in which the energy consumer and producer can trade in their existing inefficiencies. The market will decide where it is best to make the compromise, whereas before there were just wasteful externalities.
If you have an industrial process that can cope with intermittent power supply, it may be only slightly more expensive to design or build so that interruption of power won't result in interruption of production. If the overall cost increase is less than the decrease of energy costs due to incentives, there is no downside.
The energy producers likewise price the incentives so that their loss of revenue is lower than their cost savings.
Unless of course the market is created and operated by Enron, then we're all fucked.
Yup. Having many distributed li-ion battery walls charging at night for peak assist during the day is one way to level out demand and make the energy infrastructure more resilient in a Google-servers-like way.
Sell electricity at spot prices, give consumers access to that spot price, and you'll see a lot of demand flatten simply through natural market forces.
Where I live, I pay five times more for electricity between peak hours of 2pm and 8pm than I do between off-peak hours of 10pm-8am. (The remaining hours are priced at a medium level.) This has changed my behaviour, in that I now tend to wait until bedtime before switching on the clothes dryer and dishwasher.
No, although the current system is pretty tame. The electric company can turn your electric water heater or air conditioner (depending on geography and utility) off for 15 minutes at a time, and in return you get a credit on your electric bill. Its opt in.
Yes, industrial plants will turn off production (for instance at an aluminum smelting plant) in relation to the frequency of the grid. Grid frequency decreases slightly when demand starts outpacing "supply."
That frequency change used to be a natural reaction from the generators.
I wonder whether they create that signal artificially with electronics these days, or if it's still a natural consequence of the mechanics of the spinning generators they run in power stations?
I recall reading a while ago about using molten salt storage at large solar concentrators. Did this ever take off? The theory was you generate excess power during the day and you can use this excess to heat the salt solution which then release thermal energy during the night.
Does anyone know more about this? Is this able to meet baseload demand?
This one in Nevada came online not too long ago and is quite large -- apparently has 10 hours of storage and according to Wikipedia it generated 9.1GWh in February 2016 alone.
Thermodispatchable solar, even if the word does not exist, has been a recurring theme. But installations seem to be one-offs that are rarely followed by a direct successor project with the ever dropping price of photovoltaic.
In areas with cold weather, one of the most interesting (and underrated, due to only making fossil use more adaptable) developments is the installation of huge, insulated hot water tanks, to make the power generation and the great generation of combined cycle plants individually dispatchable.
Sorry for the late correction: in the last sentence I meant cogeneration plants, not combined cycle. (which would typically not be combined cycle, because the heat not captured for electricity is not wasted in cogeneration)
We have a lot of good technologies already, the problem is they just don't scale well.
I can envision older warehouses in an industrial district being converted in to vacuum flywheel storage sites where power fed in to the grid earlier is buffered and then released back to it.
Changing our culture is another possible approach. Power is used in the evenings because that's when most people get off work/home/etc and they tend to have /that/ time to do cooking and cleaning (thermal cooling / heating are more solvable with changes in materials and building shape than culture change).
That seems backwards. The aggregate preferences and habits of humans should be seen as an incentivizing force for the creations of new technologies, not the other way around.
Yikes. Yes, of course technology is driven by human preferences. But, No, humans must occasionally accept that certain habits are not sustainable given current and near-future technologies.
I generally agree with your position but in this particular scenario the people with the greatest capacity to adjust their behavior are the people who will be affected the least financially by a hike in peak prices and thus less likely to change or more likely to invest in solar at home, while those with the least flexibility in work arrangements and spending, e.g. lower income earners working in the services sector, will be affected negatively the most and unable to work around it.
If the spot market was the status quo, and someone was suggesting a change to the current system of flat prices, one could make the same argument. (Ie already well off people are flexible enough to make use of the new system better.)
More variant pricing will better distribute usage. The unfortunate effects on the poor can be negated by a sales tax paid back to all citizens equally as a lump sum.
Well, in that case, pricing electricity differently through the day will encourage people to develop new technologies for cheaply generating and/or storing electricity for evening consumption peak.
That's like saying market economies are backwards. We need to match resources to people somehow, and markets are a very popular way to do that fairly and efficiently.
I'm not saying that markets should be unchecked but it's very strange to see such naked Marxism on this site.
It doesn't have to incentivize new technologies. It could just as easily incentivize new business models. Imagine a laundromat that sells "FREE DRYING" during the day. Heck, I bet you a lot more people will do laundry during the day time. Similarly, power companies can give incentives for more day time power usage. A lot of people already follow night time power usage today so its no reason to think it wouldn't work.
You are correct- there are energy storage solutions out there, I should have clarified my statement above. The issue is that they cant store power grid levels of power in an efficient, compact, and scalable manner. This is the rub. Maintaining a giant battery bank or other measures require maintenance and large capital expenditures.
Being a manager at a large power company for 30 years is both an advantage and a disadvantage. For the past 30 years, the energy industry has changed incredibly slowly, so ones expectations of what is possible in the way of innovation is far far lower than it should be.
The "duck curve" that your friend is referring to will be solved in a variety of ways, from wind to storage to HVDC interconnects to the rest of the nation, to peaker plants.
In the future, coal is dead. No need to build any more of it. Nuclear is too expensive to build anymore. (Unless somebody actually does thorium innovation, but I'm not holding my breath...)
When storing a kWh costs $0.10, and there's also adaptive pricing to match supply and demand better, these problems will melt away.
It does require a huge mental shift, but the cost savings will make that happen
There are a couple other (not yet released) energy storage solutions mentioned there that might get the cost down even lower - Eos Aurora and Imergy Flow Battery
It'd take over 1 BILLION Powerwalls to store half the daily usage in the US (using old usage numbers off Wikipedia).
I wonder if there's enough raw materials to make that realistic. And how to you manage recycling, repair, replacement, end-of-life concerns for all those batteries on that scale?
Not asking a sarcastic hypothetical. Genuinely curious. It's hard to wrap my head around numbers that big.
Just throwing around "BILLION" doesn't make it seem big, you need to compare it the unit size.
A single gigafactory is going to produce 35 GWh in a year, which is about 5.3 million power walls a year. If their lifespan is 10 years, than we need to produce 1e9 power walls / 10 years = 100 million powerwalls/year to maintain that capacity.
So we'd only need 20 gigafactories worth to do this. And with wind and proper grid interconnects we won't even really need much storage at all to keep the electricity going; the national weather is very very consistent.
We will need enough lithium for our ~300 million cars and their batteries, which are probably going to be 50-100kWh each, which is far far more than storing half a days worth of electricity.
That's over 3 Powerwalls every second. And I've got to think you're not going to see more than 75% original capacity in ten years as a best case?
I'm not as concerned about the factory as the supply chain, can we actually supply that much raw material, and what will mining it do to the environment? I assume lithium is much rarer than iron or copper. But I don't really know.
For reference 16 million vehicles were sold in the US in 2013, but many (most?) of those were trucks and large SUVs, which AFAIK aren't on the roadmap for any EV manufacturer right now. And then there's fleet/work vehicles, single car families in states without long distance transportation or quick chargers (like TX).
It makes me wonder if 20 years from now fuel cells won't completely obsolete batteries?
If these numbers are even close to accurate, this should be the top post.
It's no use for everyone to argue over wether a completely implausible idea is financially competitive on a small scale when the implication is we're talking about scaling on a national level.
The number actually needed is a bit lower than that (I estimate half a billion), but the general question still stands.
Variable electricity needs already mean we use less electricity at night time [0]. Shift electricity expensive processes preferentially run at night to the day and using 80%/120% seems like a reasonable rough approximation. So we need 4,686,400,000,000 / 365 / 2 * 0.8 ~= 513,5780,822 kwh in the '12 dark hours'
Between current supplies nuclear hydro and wind we account for approximately 30% of electricity generation [1], on the assumption that electricity generation from these is constant, but can't be ramped up during the night, we get about 4,686,400,000,000 / 365 / 2 * 0.3 = 1,925,917,808 kwh. Leaving 3,209,863,014 kwh needed from storage, or 501,541,095 powerwalls.
I guess it could drive itself home after dropping its owner off at work, but that's probably too inefficient in most cases to make a full extra round-trip just to charge up with the panels at home.
I guess the implication being there'd be a massive number of charge spots and you could swipe your card to pull off the grid what your home is putting on.
But this would mean turning a car-park with just 40 plugs into needing 1,600 amps at 240v. With those grid connected homes having modest 2kWh solar installations you're talking 80kw/h. If you only spent 3kWh getting to work on average (double that for the round-trip) you'd fully charge the cars in a couple hours.
So I guess the goal would be to run your home off the unused capacity. But then you're putting a far heavier duty cycle on those batteries. Whose going to pay for them when that $10,000 pack needs to be refurbished in five years? Or do we just accept EVs depreciating down to zero when the pack replacement cost exceeds their value?
There may well be good answers to all this. Just some things that popped into my head.
It would seem at first glance to be very costly for the car park, the grid and the consumer. I'm not sure any technology with the depreciation schedule of lithium batteries makes sense financially or environmentally?
My modest intended implication was that if we only care about total sums, where the car is doesn't matter too much, as long as it has access to the grid.
The economics could work out, if the car park charges you more for electricity than they pay the grid; and the grid your home less that it charges the car park.
The car park and the grid both take a cut. For the home- and car owner, this works out to a slightly less efficient battery cycle. (If you convert the money charged back into the equivalent amount of energy.)
Of course, if you are going to use your electric vehicle like as a battery like this, it's going to affect the battery's useful life. The same would happen with the single purpose battery you have sitting in your home.
Now, the performance characteristics one looks for in a car battery and a grid storage battery are different. So I don't know whether using the car battery as a home battery even makes sense. (Ie home batteries can be bulky, but better be cheap. Car batteries have to be light and charge fast.)
On a more refined note, one can play the same game, but only do it during spikes. Ie the car can stop charging during a spike in demand, and even uncharge if the spike gets big enough or the battery is already full.
This won't do much for the diurnal cycle (that we discussed above), but a contribution during the spikiest peaks might already be worthwhile.
My gut feeling is that we will see the demand shaping for charging, but I am more doubtful about whether we'll see cars actively feeding back into the grid.
> Being a manager at a large power company for 30 years is both an advantage and a disadvantage.
He is definitely biased against solar, but is acutely aware of the costs it presents to traditional power generation and definitely well qualified to comment on them.
Right, and my point is kind of that the entrenched energy interests have been wrong time and again about solar, wind, and now storage. As well as HVDC.
They don't understand these things, they see less than half of the equation because they don't want things to change, and they only see the problems and have no interest in solving them.
IT wasn't that long ago that they were saying that solar was impossible, or that wind would never be affordable.
They were wrong about that and they will be wrong about how difficult it is going to be to adapt to lots of intermittant renewable energy powering the grid. They will complain vociferously, and they may be able to talk about some of the difficulties, but we can't trust their perspective on the big picture.
Nuclear could be made cheaper (even with Uranium) by updating regulations.
Fission plants are held to a much higher standards of safety in terms of eg decrease in quality adjusted life-years per Gigawatthour than any other form of producing electricity. Even solar.
(Though most deaths and injuries from solar come from people slipping off their roof when installing residential capacity. If memory serves right.)
A nuclear plant today would cost something like $6B that's not a regulatory tweak.
The problem with nuclear is waste disposal (still not figured out, and a will be a problem for decades/centuries after the plant is closed) and amortization of billions of capital costs.
With the price disruption potential of other technology, it's a bad bet, and has been so for many years.
Nuclear was only ever "viable" for political reasons. We had to have enough nuclear weapons to extinguish mammalian life nineteen times over. Eighteen times would have been pathetic. It was all a boondoggle anyway, so the war pigs were happy to spread a bit of cash on the civilian side...
The problem is they have a huge spinup and spindown cost. So as long as we have solar, we need power that we can use at those times when solar is unavailable.
This claim about peak power usage is untrue, at least for California. For the past 20 years in California, the annual peak electricity usage has ALWAYS occurred between 2pm and 5pm.:
(It's true that the daily peak is in the evening and that won't be helped by solar. But capacity is built to handle the annual peak, not the daily peak, and because the annual peak tends to be hot afternoons, solar actually will replace other generation in the long run.)
There is another way - minute by minute pricing. Much of the electric power usage is not required to be right now, and can be deferred - running the refrigerator, A/C, hotwater heater, dishwasher, charging the car, etc. With real time spot pricing information available, the deferrable usages can be deferred until the spot price is cheap.
I bet this could even out demand quite a bit.
With the current flat rate pricing structure, there is no incentive whatsoever to shift demand to blunt spikes.
Which is exactly why Tesla and other companies are investing in residential power banks. They have the potential for huge efficiency gains across the grid.
I am clearly out of my depth here but what if we take the newly daytime unused/idle coal power or natural gas power for other endeavors like sea water desalination or just pumping up water into a watertower when daytime energy cost is low and adding increased hydro capacity in the evening when the energy cost is higher?
It's already happening, but I predict we'll see more of that in the future.
Eg lots of industrial applications like smelting aluminium can do with short-ish power cuts. In return, they get a steep rebate on their electricity bill.
> Peak residential power usage is in the evening when solar isn't available. Power companies therefore end up spinning down coal and natural gas during peak solar, then just spinning them back up again as the sun begins to set.
Would it be possible (in an utopian world) to actually have a global power network and route electricity produced during the day in one area across multiple timezones to an area where the demand is greater and no available solar? e.g. Electricity produced in West Africa at noon to be delivered to .. Tokyo, where it would be 9PM.
I understand that politically this is almost impossible, but I am curious whether there are any technological impediments for this to be feasible.
I would propose a global power grid as a solution to this problem, on which the sun would never set. The only problem is that earth is not set up well for this: the Sahara would be the solar workhorse of the planet, and the consumer of all this power would be Hawaii.
Maybe if we had room-temperature superconductors. For now, transporting huge amounts of electric power across many thousands of miles is very, very inefficient.
Well, you could just massively overproduce solar, and use the excess to pump water up a hill. Also, I think there are certain externalities with coal that your friend never had to pay for, like Mercury poisoning. Reducing the amount of time coal plants run may be beneficial to reduce those externalities.
That's a good thing. Peak power usage is midday, so providing additional supply at that time avoids the need to site new plants, which costs millions or billions of dollars.
It also makes coal less economical and makes gas plants, which are cleaner and safer to operate more economical.
The power companies can get overflow from solar and wind and water and redistribute it at a profit while paying the residential over suppliers. It's on the power companies to build the infrastructure like batteries to take advantage of all this free new power.
Sorry for the noob question, but isn't there always sun somewhere on the planet? Are electricity grids not globally connected, or would it be lost in transmission?
They are not globally connected. And losses become significant after a thousand kms or so. You're not going to get to the electricity to the other side of the world where the sun is shining.
You need local storage. As much as is said about batteries, the only real solution here is hydro. Expect to see every viable valley start to get dammed over the next decade or so.
It is a problem, but not necessarily in the way you may be thinking. Peak residential power usage is in the evening when solar isn't available. Power companies therefore end up spinning down coal and natural gas during peak solar, then just spinning them back up again as the sun begins to set. [1]
So you haven't replaced the coal and natural gas plants, you're just running them less. This results in higher overall costs, because you pay $$$ to build huge plants then just let them sit most of the day, which results in higher per-watt cost of non-solar power because the infrastructure and maintenance is no longer amortized over whole-day usage.
[1] My friend, a manager of 30 years at a huge mid-west power company