Professor Keith's recent essay on solar power, "Cheap Solar Power," shows the facts and calculations to explain why solar power now beats several other sources of primary electricity for many applications. It is very likely that many industries will move to places where solar power is especially abundant and inexpensive.
It's hard to argue with numbers that are already there in front of you. A lot of the cost changes have been driven precisely because there was investment and the industry grew, his prognostications about it never being affordable were an attempt at a self-fulfilling prophecy in that by increasing skepticism about the tech curve, it never gets explored.
I'd be skeptical of his views of the future, though. For example, he mentions gas peaking plants, but grid-scale lithium ion batteries are already cheaper than natural gas peakers for many situations; lithium ion is getting cheaper but natural gas is not. The only advantage of natural gas is lower capex, but in this financial environment that's not a huge advantage. By the time that solar is displacing lots of other energy, lithium ion will be displacing all those natural gas peaker plants. Once he sees those numbers, he'll probably change his mind again.
A standard lithium ion batter is at 87% in the worst case, when it's AC-DC-storage-DC-AC. Going direct from solar panels to storage would save one trip:
In any case, the efficiency of storage is only one aspect; it limits how cheap the storage can potentially be, but electricity lost due to inefficiency is not the primary driver of storage cost with any of the currently used technologies.
The advantages over pumped hydro are,
The power density is much higher, 100000 joules/kg vs 300-500 joules/kg.
You can locate storage facilities pretty much anywhere that's out of shrapnel range. In case the big tank of gas and rocks blows up.
Doesn't have the environmental impact of dams. And rocks are significantly less precious than huge amounts of water.
But I think there may be other areas that I'm not finding specifically right now... ("solar battery" is a poor search term for this research...)
- a redox flow battery coupled directly to solar charging
- super high specific energy, ~0.33kWh/kg which is right on par with traditional solid lithium ion batteries
My remaining questions are:
- Compared to PV solar + lithium ion battery, how much insolation is required to store a kWh?
- What is the cost/kWh of the lithium iodide?
- What is the cost/kW of the solar charger, discharger?
- Can the anode and cathode be used to charge the battery from standard electricity, in addition to the (more efficient) solar method?
Thanks for this pointer, this gives me even greater optimism about the future of storage!
To flip that around, there exist applications where battery storage isn't reasonable. Is it thus also bizarre to bring batteries?
You're not answering:
> To flip that around, there exist applications where battery storage isn't reasonable. Is it thus also bizarre to bring batteries?
The post I was replying to called talking about hydro storage "bizarre". I was pointing out that it isn't. The logic here seems analogous to saying that compact cars suck because you can't use them as a dump truck.
The strong part of pumped hydropower is that it scales really really well even if the baseline efficiency isn't stellar.
It's a big power station, 1.8 GW, but is only providing service to portion of consumers in Michigan.
Making it 10 times bigger would probably be doable but it wouldn't be trivial.
It's also one of the better places on the planet to build a single reservoir system (otherwise you need 2 enormous reservoirs).
I wonder if the answer to seasonal variation will be to make fuel in the summer.
It kind of reminds me of people that think that we should use the exercise bikes in gyms to power the lighting; yes, brilliant, but actually run the numbers and you realize that humans output very very little energy even at peak exercise. The amount of waste on generators would be phenomenal.
There are some cases where pumped hydro makes sense, but there's limited scalability.
For example, 1000 kilograms of water (1 cubic meter) at the top of a 100 meter tower has a potential energy of about 0.272 kW·h (capable of raising the temperature of the same amount of water by only 0.23 Celsius = 0.42 Fahrenheit).
Given the much smaller height of a rooftop tank, every 1000 kg of water pumped would support a number of minutes of normal household usage (a decent refrigerator would need several thousand kg per hour).
I'm sure compressed air in other forms would be a good store. You could also raise and lower weights into a mine, it doesn't matter so long as you can convert between electric energy and kinetic potential of some kind.
1000L tank on a roof which is ~4m high.
E = m * g * h = 1000 * 9.8 * 4 = ~40,000J
Which is about 12Wh not taking into account any losses.
You could maybe improve this by having the water fall into a well but still nowhere near what a battery can provide for a fraction of the cost/complexity.
A standard 100Ah battery will provide 1200Wh.
Also, there are projects to do the thermodynamic equivalent of district heating over a single home! i.e. you burn gas to produce electricity, and use the waste heat to heat your house or office. A year or two back British Gas was doing a pilot using a gas boiler with a Stirling Engine to generate electricity (called the Ecogen IIRC). It seems to have been difficult/expensive to maintain, but it's an exciting principle.
If you had battery storage for solar during the Summer, you could use that equally to buffer that kind of gas generation in the Winter.
It seems to me sufficient solar and battery cost reductions effectively solve electricity generation for everywhere close to the equator. Add in that kind of waste heat boiler, generating electricity at a reasonable cost, and you have a solution for almost the whole planet.
Fuel cells sound really neat, and I had no idea you could actually by your own until a couple days ago. But the estimate of a small continuous use unit needing to have the catalyst replaced up to annually seems to make them a novelty for now (the existing units that is).
Interested in knowing more if you keep up with it though.
Transmission losses in the electric power grid are around 6.5%, but that's because the energy is typically only transmitted a few hundred kilometers; about 4000 km is the longest cost-effective distance for AC power transmission. LNG tankers can travel further than that.
Bearings and motors/generators are very well understood, unlike lithium ion batteries, so I don't see them getting much cheaper as a flywheel industry expands.
Currently, the most expensive lithium ion battery is cheaper than the cheapest flywheel:
Still a flywheel powered car using three flywheels set at opposing angles (so their gyroscopic effects cancel) composed of tightly wrapped layers (so they cannot explode) would be awesome.
What's really hard to deal with is the angular momentum. Regardless of how the rotor fragments, angular momentum is conserved. What this means is that the failing rotor will produce amazingly high torques as it encounters stationary surroundings.
For typical rotor failures, you can figure that most of the angular momentum will get dumped into the environment in a few seconds as the fragments dig into whatever they hit and come to rest. So as a napkin exercise, if your flywheel spins up to full charge over a period of an hour, and then dumps all that momentum during ten seconds when it fails, you can kind of approximate the torque drama by multiplying the charging torque times the ratio of the charge duration to the failure duration. (I know the torque varies with the flywheel speed, etc. - this is just a disaster estimation exercise.)
The practical effect is that you have to secure the containment really well to make sure it doesn't break loose and roll through your facility on its way out into the street.
The only two ways I've seen of dealing with the angular momentum problem are (1) have two adjacent counter-rotating wheels that jam into each other when there's a failure or (2) have a containment shell that is free to rotate on one-time use mechanical bearings so it can take the failed rotor momentum and dissipate it over a reasonable time with a braking mechanism. Neither solution is cheap.
It's uplifting to me, both for the high value on a ton of CO2 and the (still) low resulting price of fuel. Solar beats fusion (chance * impact)!
I suspect over time the cost of producing solar electricity will become negligible against the cost of storage. The key thing will be not so much the lower levels of sun which you get in temperate latitudes, but the variation you get between Summer and Winter levels of insolation, which means you have to maintain backup generation. Variation within a day you can deal with, variation from season to season will be much more difficult. But as you say that is going to drive some interesting changes in geopolitics.
The obvious thing to do is just size the solar array for the winter insolation levels, since the solar part is likely to be so much cheaper than the storage part.
Also, don't forget wind, which is also super cheap at the good sites. It will balance out some of the seasonal shift, and also a good amount of the night time needs.
This all depends on cross-continent interconnects, and energy markets. The entrenched interests are going to resist mightily to anything that might cost them even a cent, and they control the laws to lock out competition.
I view interconnects as important an issue as the interstate system. It will enable so much innovation and drive down costs quite a bit.
I don't follow solar/power/coal news much, so forgive me ...
Is all of this ex-subsidies ? That is, if we remove the subsidies that coal gets and the tax credits / subsidies that solar gets, does the math still pencil out in the way that still makes David Keith no longer a skeptic ?
Also ask what price point would be needed to scale back CO2 emissions to something sustainable. Then run the economic analyses.
Coal provides baseless power--coal plants are designed to run at a relatively steady level for more than 90% of the time. Reliable power is critical for things like server farms which draw power all the time. Solar cannot serve the same purpose without battery or other backup.
At this time of year in places like California, solar doesn't help meet peak demand either. http://content.caiso.com/green/renewrpt/20160503_DailyRenewa... Solar has a role, but comparing it to coal is misleading.
For example - utility scale storage (pumped hydro); distributed storage (home batteries and Vehicle-to-grid battery Ev cars); demand-side management; power-to-gas (hydrogen); and geographic grid integration.
See more at
Pumped hydro is probably the best bet, but is very geography dependent. Adding transmission is a non-trivial investment.
We have a pumped hydro solution where I live. It's huge and only supplements a small power plant.
"One of the striking things about the ARES project is its size: 50 MW of power capacity and 12.5 MWh of energy. That would be large for a battery storage project, but for ARES, it is on the low side. “Fifty megawatts doesn’t get us to economies of scale,” CEO James Kelly said. “We are more efficient as we get larger.”
Kelly said ARES projects can be sized anywhere from 50 MW to 1 GW. “If we had a 500 MW project, we could double the capacity and it would only increase capital costs by 20%,” he said."
Could they perhaps achieve high enough mass in a small volume by using eg. lead?
Could it be that a train is more efficient at converting potential energy than a water turbine?
Could it be that they have a longer drop?
You gotta show your assumptions if you're arguing through back of the envelope calculation.
Not all locations have a lake (or 2) conveniently located near a large elevation drop.
The article says "They move up and down an 8-degree slope with an elevation change of about 3,000 feet", that's a lot of energy.
A reservoir 10m deep and 45m square at the same elevation has the same potential energy. If you can find a convenient 1000m plateau I think it would probably be cheaper to build a reservoir on top than to build the tracks and trains.
Now I wonder how fast these railcars move.
I wonder how hard it is to scale though.
See this for a comprehensive annual survey by Lazard on storage technologies and costs
You could build surface level reservoirs as two tank hydroelectric dams, and then use the water as an energy reserve as well as freshwater reserve.
Non-trivial in terms of size and politics, but an extremely solid one that will reduce the cost of electricity.
That's a very specific claim, and I don't think your cited graph even supports it.
Presumably, you say "this time of year" because you know that the yearly peak in California is driven by air-con usage in the summer afternoons, which correlates very well with solar.
But even right now, in early May, the graph is mostly flat through the afternoon and evening, with only the slight peak at 8 or 9 at night making your statement true in a very narrow sense.
Notably however, the graph only includes grid side solar production, so panels on homes or business roofs are not included in the graph. If you added those to the total demand curve would shift upwards during solar production hours.
Yes, solar can help meet peak load during the summer, but not the rest of the year and it causes stress on the system by requiring a lot of power to spin up to meet demand and solar decreases.
You don't know when peak demand in California was yesterday, because you're looking at a graph of the utility company's electricity production, not electricity demand. You'd need to add all the self-consumption by "behind-the-meter" solar installations on homes and businesses to find out the real demand peak. From the perspective of CAISO, solar self-generation is indistiguishable from reduced demand.
We know from historical figures that the absolute highest yearly peak in California, the one that you need to build your grid to withstand at great expense even if it only requires that load for a short period of time per year correlates well with solar, and so solar saves lots of money by shaving that peak.
The "duck curve" is also not a demand curve, it's demand, minus self-generated-solar, minus grid-generated-solar. And even then, it only appears in the winter months, when demand in California is on the low end of the yearly cycle something like a third of peak demand in the summer months. (Note the graphs showing the duck curve in your second link are from January and March).
I don't think that explains everything about the demand curve, but using the current day demand curve to say 'solar doesn't work' isn't looking deeply enough.
I like the Arthur Clarke quote:
When a distinguished but elderly scientist states that something is possible, he is almost certainly right. When he states that something is impossible, he is very probably wrong.
- Arthur C. Clarke
Note that Solar isn't "hurting". Because such demand right now is being covered by Natural Gas Peaker Plants anyway.
Natural Gas Peaker plants are expensive, so if we can replace some of their usage with other energy sources, that'd be great. Eventually, we might be able to transition off of them with sufficiently advanced energy storage technologies.
And once baseload power starts getting "replaced", we enter the realm of coal plants and nuclear plants reconditioning themselves so that they can be scaled up and down a bit better.
I know both coal and nuclear power require many minutes to change their energy production, but if a smaller-scale energy storage (~30 minutes) can be created to hold out during the scaling up / down period, the problem could be solved.
As opposed to say, load-shifting pure solar energy (which requires a storage capacity measured in hours, not minutes). High power / low time can be solved with standard Lead Acid batteries or maybe Flywheels (cheaper technology than Lithium Ion, which would be better for hours of storage)
Industries and homes find innovative ways to adapt to market pricing. All the appliances there have options to use power at night (when it is cheaper there). For solar, the times may be different but the same idea remains. Commercial power is priced at a premium when the grid is overloaded (typically winter months).
"Technicians say that the Noor 2 and 3 plants, due to open in 2017 will store energy for up to eight hours – opening the prospect of 24/7 solar energy in the Sahara, and the surrounding region."
Think of the battery as a really big capacitor operating on a larger time-scale. It's perfectly reasonable to smooth out power this way, and as battery technology improves, you will certainly see more reliable power from solar for things like server farms.
I agree storage (if required) and environmental impact should both be considered when comparing different energy options.
Energy storage is improving rapidly. Lithium-Ion batteries are but one technology that I don't personally expect will become the norm at grid-scale.
> The larger Powerwall was positioned as a longer-term back up power supply, which GTM noted was looking like a hard sell, with other market alternatives that were priced far below the $3500 price tag.
> The remaining 6.4 kwh device has less capacity, and is designed more to shift the load of available power, such as from a solar panel, to times when the production of such energy is lower.
Also the Powerwall is for home use. For utilities they offer Powerpacks, and they are already on sale:
There's nothing stopping anyone from getting more than one battery to make up for the capacity that was offered by the larger model.
It's true that the daily peak is in the evening and that won't be helped by solar. But grid generation capacity is built to handle the annual peak, not the daily peak, so the annual peak is what matters. And because the annual peak tends to be hot afternoons, solar actually will replace other generation in the long run.
I used to analyze this stuff professionally when I worked at a California utility.
Is it just too hard to move electricity so far away?
In the short term, transmission lines are congested during peak hours so we often can't pipe enough power to high demand markets.
“Let’s Build a Global Power Grid - IEEE Spectrum”
Maintaining fiber optic cables can be hard across the ocean. How about a power line that has a diameter of 50 feet? I can't even imagine the engineering of that.
Info on losses here: https://en.wikipedia.org/wiki/Electric_power_transmission#Lo...
No idea on the math for what % of power we would lose across the ocean.
Seems local batteries would win out..
The circumference of the earth at the equator is 24,901 miles. Halfway around the world, we'd deliver 29% of original power.
The holy grail in transmission is high temperature super conductors. We're not there yet.
The difference between solar and coal is that the output of coal is more reliable.
It is correct that coal does not ramp up or down quickly, but that is not a characteristic of dispatchablilty.
It's exists between something like nuclear (which has to just be on for months at a time) and natural gas peaker plants (which turn off and one during the day to meet demand.
You could, for example, run coal plants during the winter (when there is little sun) and not during the summer. Or you could run coal on cloudy days. Or just turn it off on weekends.
(I understand your actual point, and agree with it)
Solar reduces the base load required and makes the maintenance and capital costs of coal stations higher.
the only question is, can politicians be convinced to do something good for the country which may not keep them in office?
It's a different game altogether - batteries etc instead of train cars full of coal. But it will happen.
Elon Musk, CEO of Tesla is some 2 to 5 years away from fixing that battery issue and getting extremely rich in the process.
Large, somewhat unpredictable fluctuations in the cost of generation (solar and wind) should lead to large fluctuations in price of generated electricity, down to minute-by-minute. Ideally, generators want to sell every kwh they can at peak production, even at a lower cost. With modern computer controls, this makes a delightful opportunity for an arbitrage market.
Storage providers - and this could be giants like lake-scale hydro, or dwarves like the batteries in electric cars - could buy electricity from generators when it's cheap, and sell it when it's expensive (the sun isn't shining, the wind isn't blowing, hot day spikes demand, etc). This can be fully automated. Just plug your car into the wall at night. It might decide to buy electricity, or sell electricity, depending on the price at the time. Aggregators could pool capacity across many small providers. Large storage systems could benefit from economies of scale and long-term contracts.
Create a smart grid that can support this, and let the free market solve the pricing problems for us.
The PJM capacity market had a big increase in demand response supply circa 2012, though not much of it was from storage. Still, new players are paying attention to these arbitrage opportunities. CAISO is already seeking out corporate partners to participate in demand reduction.
If it was clearly economical, someone like Exelon (who owns nuke plants) would probably be doing it.
Then again, at lest several utilities claims they were going to buy Telsa powerwalls to do it. So maybe the pricing is getting to the point where it's profitable.
Nuclear plants, as you probably know, are almost pure base load solutions. They can't just be scaled up or slowed down arbitrarily. A volatile, arbitrage-based market efficiency would be pretty hard on the existing nuclear base, and could render a lot of plants unprofitable.
Meanwhile, the gas-fired peak load plants are tremendously expensive, because they have so much downtime and are inefficient. One or two decades ago, competing against them with storage was economically impractical. Now, it's becoming feasible. Especially once we start building gigawatts of sitting capacity anyway, in the shape of EV cars.
One can suspect that Masdar had access to long-term financing through the wealthy emirate of Abu Dhabi that no commercial banks, the primary source of capital for the other bidders, could match in cost.
1. 1 out of 78 jobs created in the U.S. last year were solar jobs.
2. There are more solar employees in California than utility employees.
3. Soft costs (non-hardware) were recently 64% of the installed cost of solar.
4. Solar is expected to reach a load defection point (i.e. cheaper to leave the grid) in most places in the next 10-15 years.
5. Energy over the next 25 years is a potential $200 trillion opportunity.
Like OP's article states, this industry's hardware has gotten really cheap, but the software in the industry hasn't kept up in places. So much so, in fact, that an entire startup accelerator program in the bay area, Powerhouse, has been created to try and attract tech entrepreneurs into the solar industry to make the next generation of solar software. My startup recently went through the program, and being a part of this industry is one of the most empowering and rewarding things I've ever done. It's one of those extremely rare instances where you can have a solid business model and a positive impact on the world.
And we need all the help it can get. Solar expected to grow 100-200x over the next 25 years, but it won't happen if smart people don't join in. Smart grid, machine learning, energy storage, demand response, customer acquisition, logistics, energy efficiency, inventory tracking, IoT, security, and many more software areas are currently in the dark ages in energy. Solar, wind, nuclear, geothermal, storage, and other clean energy sources have to replace 87% of the worlds energy in the next 32 years. PLEASE HELP US!
If you're a tech entrepreneur, and want to do something that matters, please please please consider doing a startup in solar or other clean energy industry. To start, if you're in the bay area, there's a hackathon next weekend around solar software. I encourage you to come and learn more about solar and software in the clean energy sector.
Working on stuff like smart grids, demand response, inventory tracking, security, etc seem like something the big companies who own the infrastructure need to be doing. Some random entrepreneur isn't exactly in a position to make solutions for these giant companies because there's no way to have access to the information needed. And even then, selling software to giant companies is hard as shit, and if you strike out there's not exactly a lot of other customers to sell to.
It just doesn't seem like an environment conducive to entrepreneurship.
That compares to a solar panel efficiency of .15; and I guess a lot less when applied to water heating due to conversion.
And implementing in dense urban areas, passive is not as viable as active.
If we were serious we would first implement passive systems.
But we don't. I guess there’s something I don’t understand.
For investors, a big power station like this is a purely economic decision (will it be profitable or not).
For a homeowner, a few dollars a month for hot water is not a significant motivator to make a change (replacing a thing that works to save money after several years is not exciting).
It would probably be a good idea to figure out how to incentivize rental property owners to increase building efficiency. Or maybe just pay for it directly in exchange for a few years of not capturing the benefit in the rent.
Creating electricity with a lot of effort and using it for heating water doesn't make sense.
The sea critters are already happy to swim around in it, and you're not going to meaningfully change the concentration of the ocean. You could mix it with sea water near the exit point to avoid temporarily raising the concentration there.
(though you might need more sun and space for that)
"All the other ways" is salt mines
Second question down.
"Whereas they concentrate seawater 1.5 times, recovery of salt would require seawater to be concentrated ten times. Under such conditions the first crystals would appear in the brine"
You'll just start with something more concentrated instead of seawater
Yes, you might have a reason to not want to do that, it might be easier/cheaper to just throw it back into the sea
Remember, before we invented tractors, if you wanted to move a thousand tons of rock a mile, it had to be done largely by hand. That is a use case for slave labor. Before we invented harvesters, cotton had to be picked by hand. That is a use case for slave labor. Domestic servants are a use case. But the invention of powered machinery made most slave jobs obsolete.
1/ Can solar impact CO2 emissions beyond single digit percentages?
2/ On what order of magnitude would battery storage capabilities have to improve to match performance characteristics of natural gas peaker plants or dare we say Oil/Natural gas?
3/ Don't the fluctuations in peak demand make solar less attractive because they require rapid natural gas peaking plants when there's increases in usage? (Outside of summer is a great example)
4/ What would be the desired performance characteristics of batteries that would make Solar a no-brainer for the environmental impact and actual viability? Cost, capability, and reusability.
Curious that Bloomberg opted for the Persian, over Arabian, Gulf when referring to the United Arab Emirates.
Since you brought up trains, look at the giant mess that is the California 'bullet' train. Not a single section of track has been completed, and it's already doubled in budget, reduced dramatically in speed (current projections put the trip time at ~4hrs due to a number of issues including track sharing), with ticket prices 70% higher than promised, and the legal requirements for private investment have been ignored because no private company is willing to touch it with a ten foot pole.
Dramatic changes indeed...
Even Solyndras is just one tiny failure in a massive pool of wealth-creation with regards to the entire program. US Government makes money from the loans. US citizens created jobs for each other. Solar energy development got accelerated.
The only answer to Solyndras is... damn, that was a single battle lost (0.5 Billion loan default), but the US definitely "won the war" on the $800 Billion program.
While dodging a question about his understanding of economics. Forgive me, I'm just a bitter Canadian upset that we're now running a huge deficit and passing the buck on to our children.
The huge chunk of debt is owed from one part of the government to the other.
No one ever cut their way to growth. The key is almost always to grow the GDP faster than you grow the debt on average. The nominal debt number will never go down - ever - but it should stay fixed or shrink relative to GDP if possible.