From Stanford University
Stanford scientists calculate the energy required to store wind and solar power on the grid
Renewable energy holds the promise of reducing carbon dioxide emissions. But there are times when solar and wind farms generate more electricity than is needed by consumers. Storing that surplus energy in batteries for later use seems like an obvious solution, but a new study from Stanford University suggests that might not always be the case.
“We looked at batteries and other promising technologies for storing solar and wind energy on the electrical grid,” said Charles Barnhart, the lead author of the study and a postdoctoral scholar at Stanford’s Global Climate and Energy Project (GCEP).
“Our primary goal was to calculate their overall energetic cost – that is, the total amount of fuel and electricity required to build and operate these storage technologies. We found that when you factor in the energetic costs, grid-scale batteries make sense for storing surplus solar energy, but not for wind.”
The study, which is supported by GCEP, is published in the online edition of the journal Energy and Environmental Science.
Climate change and renewable energy
Most electricity in the United States is generated at power plants that run on coal and natural gas – fossil fuels that contribute significantly to global warming by emitting large amounts of carbon dioxide. Solar and wind power are emissions-free and renewable, but depend on sunlight or wind to operate.
“For the grid to function efficiently, power supply needs to match power demand at all times, but with renewables, that’s not always the case,” Barnhart said. “For example, wind farms sometimes produce too much electricity at night when demand is low. That excess energy has to be stored or used elsewhere. Otherwise it will be lost. However, the U.S. grid has very limited storage capacity.”
A wide variety of technologies are being developed to address the lack of grid-scale storage. The Stanford team looked at several emerging technologies, including five battery types – lead-acid, lithium-ion, sodium-sulfur, vanadium-redox and zinc-bromine.
In a previous study, Barnhart calculated the energetic cost of building and maintaining each of the five battery systems for grid-scale storage. Lead-acid batteries had the highest energetic cost, lithium-ion the lowest, he found.
“We calculated how much energy is used over the full lifecycle of the battery – from the mining of raw materials to the installation of the finished device,” Barnhart said. “Batteries with high energetic cost consume more fossil fuels and therefore release more carbon dioxide over their lifetime. If a battery’s energetic cost is too high, its overall contribution to global warming could negate the environmental benefits of the wind or solar farm it was supposed to support.”
For this study, he and his colleagues calculated the energetic cost of grid-scale photovoltaic solar cells and wind turbines.
“Both wind turbines and photovoltaics deliver more energy than it takes to build and maintain them,” said GCEP postdoctoral scholar Michael Dale, a co-author of the study. “However, our calculations showed that the overall energetic cost of wind turbines is much lower than conventional solar panels, which require lots of energy, primarily from fossil fuels, for processing silicon and fabricating other components.”
To store or curtail?
Next the scientists looked at the energetic cost of curtailment – the practice of shutting down solar panels and wind turbines to reduce the production of surplus electricity on the grid.
“Curtailment of renewable resources seems wasteful,” Barnhart said. “But grid operators routinely curtail wind turbines to avoid a sudden, unexpected surge of excess electricity that could overload transmission lines and cause blackouts. Curtailment rates in the U.S. will likely increase as renewable energy becomes more prevalent.”
Shutting down a clean source of electricity seems counterproductive, but is storing surplus energy in batteries a practical alternative?
To find out, the researchers compared the energetic cost of curtailing solar and wind power, versus the energetic cost of grid-scale storage. Their calculations were based on a formula known as “energy return on investment” – the amount of energy produced by a technology, divided by the amount of energy it takes to build and maintain it.
Using that formula, the researchers found that the amount of energy required to create a solar farm is comparable to the energy used to build each of the five battery technologies. “Using batteries to store solar power during periods of low demand would, therefore, be energetically favorable,” Dale said.
The results were quite different for wind farms. The scientists found that curtailing wind power reduces the energy return on investment by 10 percent. But storing surplus wind-generated electricity in batteries results in even greater reductions – from about 20 percent for lithium-ion batteries to more than 50 percent for lead-acid.
“Ideally, the energetic cost of curtailing a resource should at least equal the amount of energy it cost to store it,” Dale said. “That’s the case for photovoltaics, but for wind farms, the energetic cost of curtailment is much lower than it is for batteries. Therefore, it would actually be more energetically efficient to shut down a wind turbine than to store the surplus electricity it generates.”
He compared it to buying a safe. “You wouldn’t spend a $100 on a safe to store a $10 watch,” he said. “Likewise, it’s not sensible to build energetically expensive batteries for an energetically cheap resource like wind, but it does make sense for photovoltaic systems, which require lots of energy to produce.”
Increasing the cycle life of a battery would be the most effective way to improve its energetic performance, Barnhart added. Conventional lithium-ion batteries last about four years, or 6,000 charge-discharge cycles. Lead-acid batteries only last about 700 cycles. To efficiently store energy on the grid, batteries must endure 10,000 to 18,000 cycles, he said.
“Storing energy consumes energy, and curtailing energy wastes it,” Barnhart said. “In either case, the result is a reduction in the overall energy return on investment.”
Other options
In addition to batteries, the researchers considered other technologies for storing renewable energy, such as pumped hydroelectric storage, which uses surplus electricity to pump water to a reservoir behind a dam. Later, when demand for energy is high, the stored water is released through turbines in the dam to generate electricity.
“Pumped hydro is used in 99 percent of grid storage today, ” Barnhart said. “It works fantastically from an energetic perspective for both wind and solar. Its energy return on investment is 10 times better than conventional batteries. But there are geologic and environmental constraints on where pumped hydro can be deployed.”
Storage is not the only way to improve grid reliability. “Energy that would otherwise be lost during times of excess could be used to pump water for irrigation or to charge a fleet of electric vehicles, for example,” Dale said.
It’s important for society to be energy-smart about implementing new technologies, Barnhart added. “Policymakers and investors need to consider the energetic cost as well as the financial cost of new technologies,” he said. “If economics is the sole focus, then less expensive technologies that require significant amounts of energy for their manufacture, maintenance and replacement might win out – even if they ultimately increase greenhouse gas emissions and negate the long-term benefits of implementing wind and solar power.”
“Our goal is to understand what’s needed to build a scalable low-carbon energy system,” said co-author Sally Benson, the director of GCEP and a professor of energy resources engineering. “Energy return on investment is one of those metrics that sheds light on potential roadblocks. Hopefully this study will provide a performance target to guide future research on grid-scale energy storage.”
Adam Brandt, an assistant professor of energy resources engineering in Stanford’s School of Earth Sciences, also co-authored the study.
This article was written by Mark Shwartz of the Precourt Institute for Energy at Stanford University.
Really enjoyable thread. After Willis showed that a tonne of coal is the best battery perhaps he could turn his analytical skills to this problem.
It seems from the above and as per previous posts, mitigation is the way to go. Here we can buy water heaters that use the waste heat from air conditioning units. 20% power saving at least there. Solar water heaters can drive space chillers. Better insulation. All make massive savings on the bottom line, how much you pay per moth.
Regarding storage, how about pump from the Med, fill a balance lake higher up. then when power is needed drain to the Dead Sea. Several places that can be done around the world.
Re spreading the power around. Comments made on HVDC transmission. No need to make a grid with it, just link grids. Example Indonesia to South East Asia. Power it up with Geothermal. Same in Japan, link to Korea-Asian Mainland. You get clean power and greater flexibility. The UK is looking at Importing same power from Iceland.
@Bruce of Newcastle 5:34 pm – low grade ores
I totally agree, Bruce. When I mentioned that we’d need 1000 lead than current reserves, it was to make the point that it is a tall order. Price increases will ultimatly increase reserves, but 1000 times is unlikely.
If, (and it is a very big IF) and when (likely not to soon), battery storage becomes viable I think it will negatively impact ‘renewables’. Conventional energy generation will benefit by running FLAT-OUT at high efficiency 24 hour a day and store the off peak excess power and push to the grid as needed. A propeller on a pole will never compete. Cheers, Mark
Here is a Na-S battery system, of 1 MW capacity, that is installed on Santa Catalina Island offshore Los Angeles, California. This is not for wind or solar power storage, but to reduce pollutants into the air from the diesel-powered generators on the island. The local air pollution control district required the emissions be reduced, and this is the agreed solution. The diesel generators now run at a nearly constant rate, with excess power stored in the batteries at night. Power is drawn from the batteries the next day. A suitable monitoring and control system ensures the local grid is stable.
http://www.energystorageexchange.org/projects/77
“The isolated electrical system on Santa Catalina Island has daily load variations from approximately 2 MW in the very early morning to approximately 5 MW in the late afternoon. SCE’s existing diesel generating capacity must be constantly cycled to accommodate the varying system load. One of the major consequences of cycling the diesel generators is operating the units at less-than-optimal Nitrous-Oxide (NOx) emission operating points.”
Uh. Roger.
That’s 2 Megawatt. Not needed, but politivally required 2 Megawatt – so it really doesn’t matter whether or not that little bitty 2 meg battery system is economically justified or ecologically justified (energy and time “in” > energy and time and value “out” ) but merely “Did the government demand we do this?”
Now, a little itty bitty 2 MegWatt “overnight” power supply is good enough to replace ONE wind turbine. One time. IF that wind turbine is only “out” for one night.
Ya got another 300 battery systems to work with ONE combined cycle gas turbine of 600 Megawatts?
I’m too much of a tyro to know which of the preceding suggestions could be the basis for a future Nobel prize, and which could be the deluded ramblings of an old man wearing tinfoil headgear. (*)
One thing, however, comes through very clearly: while all (or most) of those commenting may be AGW skeptics, you are as invested in protecting the environment as those who stage protests under a banner for Gaia. There is an obvious passion for facts; pet theories are discouraged. Every theory or plan for harnessing power from Nature is examined with a hope for success, but with an eye for flaws. And when something works, you embrace it. Many of you (with Anthony being a prime example) have adapted “green” technologies to a far greater degree than those who publicly endorse them.
Nor is this phenomenon unique to this site (although I think this site exhibits it to an unusually high degree). The fact is, aside from a kind of loony fringe of skeptics who don’t believe in AGW because it’s all part of a nefarious plan set in motion centuries ago by a secret, but very, very powerful society whose members include not only past presidents of the United States and Russia, but also the entire writing team for Saturday Night Live — aside from such outliers, one of the most obvious traits of AGW skeptics is their respect for the environment and their desire to protect it as much as possible.
So the question is, how come the “anti-environment” label sticks so readily to them?
I didn’t say I had an answer.
—————–
* While popular culture and common usage refer to thought-protection helmets as “tin foil hats,” tinfoil is no longer the recommended material. Research conducted by Michael Menkin indicates that Velostat, available in rolls from the 3M company, is far superior, with an apparent 100% efficacy in preventing alien abductions by blocking out their spy rays. [ Stop Alien Abductions
You mean that batteries are not included when you get these blasted windmills? For the price they cost you’d think the manufacturers could throw in a couple of AAs.
@ur momisugly RACookPE1978, actually, the Catalina Island battery system is only 1 MW, per the article. The night-time load is approximately 2 MW.
“In response to diesel engine emission reviews at PBGS, the 2009 SCE-SCAQMD settlement agreement directed SCE to install a 1 MW battery system to help stabilize the generation fluctuations. The battery project was completed in 2011 in partnership with S&C Electronics. It provides the necessary energy storage capacity during off-peak periods, and energy supply capacity during on-peak periods, to allow for steady operation of the diesel generators at fixed, minimum emission operating points. Additional benefits include improved system voltage regulation, system stability, and system reliability.” (Note, SCE is the utility, Southern California Edison. SCAQMD is the air pollution agency, South Coast Air Quality Management District)
The battery technology works, so there can be no debate about “does it work.” The only question is one of economics. It is well-known that energy storage at grid-scales, as you suggested 300 MW is too expensive for any but rare installations. As others above wrote, pumped storage hydroelectric can be economic, but the number of suitable sites is small.
@Margaret Smith
Before you start writing “f’ words, please remember that some of us have had a delicate upbringing.
Teresa says:
September 9, 2013 at 1:21 pm
It’s a matter of scale, heat transfer area and method, water flow rate and delta temperature, and availability of many things: The natural gas pipeline, the need for the electricity at that location, the availability of the water for the natural gas plant cooling, the availability of the extra power lines required, and the ability to actually preheat that much water that fast with the electric heaters from the wind generation facility. A steam plant needs a LOT of reheating power every second – many hundred times what the wind generators normally produce.
A wind on average only generates 23% of its ‘rated power”. When it is “out” – which is most of the time – you have to be able to preheat that water anyway over in the natural gas-fired/coal-fired plant, right? SO you’d have to build two sets of heat exchangers – one set of which is not going to be doing anything but wasting pumping power and money being built but NOT heating the water more than 4/5 days of the year. (The regular steam-heated/waste-heat recovery heat exchangers have to always be on-service, so the electric heaters form the wind generators require more piping, more heat exchange area, and more pump resistance in the power plant pipes. ) When the wind generators are “on” they may be turning, but only creating 10% to 30% of their maximum rated load.
But notice that you HAVE to build the extra power lines and transformers and wires and controls and switch-yards and monitors AS IF the wind turbines WERE creating 100% of their rated load, but – every now and then – they do actually generate 100% rated power. So you end up building many millions of extra expensive material consuming resources only to use them only 23% of the time.
Also, not “all” of the wind-created power is “not used” – many days, what little is generated CAN be used on the grid. The number of days of “over-production” by the wind turbines is actually very, very few.
Grey Lensman said “how about a pump from the Med …”. Nice concept (as the Med is essentially non-tidal) but I think the real problem is practical politics: there are just too many stakeholder countries around the Med (all of whom will be saying what’s in this for us, as we now need to build raised harbour walls) including some of the most volatile in the world…
And as to connecting national or regional grids, this is of course happening anyway where tariffs can be agreed (eg England/France) but at quite short range – the real benefits will only come where connections are at long range – eg to balance night and day (perhaps crossing the Atlantic?) or even summer and winter…!
The unspoken problem with flywheel storage;
1. Kinetic energy – E=mv2 so if energy is taken out at a constant rate speed loss is exponential.
2. Electromagnetic induction – V=blv2 so as speed drops voltage drops exponentially. This cause huge regulation problems and a very limited period of useful output.
Roger Sowell-
“Here is a Na-S battery system, of 1 MW capacity, that is installed on Santa Catalina Island”
An important battery system spec is energy storage. The S&C brochure describing the Catalina project indicates it may have a maximum energy storage capacity of about 7000 kWhr. Also, the system cost is $6.1M. So, that comes out to about $870/kWhr. Very pricey.
Onshore wind turbine installed is about $3/W, or $9M for a 3MW turbine. At 25% capacity, it generates on average about 18,000 kWhr/day. Since there are times when this turbine may be idle for a week, a battery backup for the wind turbine should have a capacity of 126,000 kWhr.
The $9M wind turbine needs a $110M Na-S battery backup to guarantee power delivery during a potential windless week.
http://www.sandc.com/edocs_pdfs/EDOC_075872.pdf
Is there no thought given to the poor Power System Dispatcher that would have to manage all these pipe dreams. I used to be one and had enough issues with conventional. This talk about a smart grid, bring that subject up with a Power Dispatcher then stand back to get away from the spittle coming out of his mouth.
Cam_S says:
September 9, 2013 at 10:15 am
A hydroelectric facility over 35 MW capacity does not qualify for RPS. It seems they don’t want to encourage new storage.
Why don’t we use excess wind to make H2 from wastewater? You only need half of that battery. Throw the O2 away. You can get it back anytime.
LH2 from wastewater using nuclear would be better. No gasoline needed. And you could easily get superconducting conduits for power in your pipe to deliver LH2. Boiled off H2 can replace natural gas. EMP protection too.
California loves its command and control economy. Gone are the days of great innovation and leading the world forward. Now the dream is to be just like Cuba. Viva Che!
Consider this from another view point: the free market has always produced, and will always produce the cheapest form of energy generation. Period. Take away the gov’t subsidies (and that will happen eventually as even we can’t afford to keep printing money forever) and the renewables market turns to vapor in a heartbeat. The free market will still continue to produce affordable electricity (relatively speaking) because it must in order to stay in business.
Tim OBrien says:
September 9, 2013 at 12:05 pm
Did they factor in the high costs of the toxic heavy-metal cleanup associated with lead, zinc, etc.???
Did they factor in the number of deaths associated with the mining, manufacturing and disposal of those same heavy-metal items?
Tim you forget that these people don’t live in developed countries with vocal green groups. Their lives, therefore, do not get factored in to the costs (they are not even middle class!).
Gail Combs:
I rarely disagree with one of your usually very fine posts, but this is one of those rare occasions.
In your post at September 9, 2013 at 6:32 pm
http://wattsupwiththat.com/2013/09/09/claim-lets-put-batteries-on-wind-and-solar-farms/#comment-1412862
you quote davidmhoffer having said
And you reply to that saying
Sorry, but David is right.
The ONLY valid consideration is financial return, and energy return is not relevant.
This is because people buy what they want. And they buy the energy they want in the form that they want. They pay for what they want in money and NOT energy.
For example, a person who wants to power a portable radio will buy the needed batteries. He has no interest in whether the life cycle of the batteries provides or consumes net energy. He only considers how to power his radio most cheaply and reliably.
Wind and solar are expensive sources of electricity for supply to a grid. And they are guaranteed to be unreliable because they only work some of the time.
Also,
A ‘Rule Of Thumb’ is that if something costs most then it uses most energy.
This is because energy is ability to do work, and
Money is payment for work done.
Richard
Stephen Rasey:
re your post at September 9, 2013 at 8:00 pm
http://wattsupwiththat.com/2013/09/09/claim-lets-put-batteries-on-wind-and-solar-farms/#comment-1412907
Yes. I provide a link to draw attention to it.
Richard
Grey Lensman:
re your post at September 9, 2013 at 8:02 pm.
Your suggestions are both technically and politically difficult to implement.
Building fossil fueled or nuclear power stations would be cheaper, more reliable and far less environmentally damaging.
Richard
Mark:
At September 9, 2013 at 8:10 pm you say
Yes, and it would reduce the need for power stations by about a third.
Richard
Sounds like a plan conceived by idiots.
Energy losses converting the generated AC to DC for battery storage, then back to AC for distribution would wipe out any power produced. Then extra infrastructure costs, battery costs would make the whole thing totally unaffordable.
Back in the early 90’s I lived in Switzerland. At that time the French and Swiss had nuclear power plants that generated significant power at minimum, base load output levels, more than enough for off-peak periods but not enough for peak periods. The ever entrepreneurial Swiss had a great scheme going, they bought the French off-peak base load power from the nuclear plants at a discount price so the French could manage their nuclear plants and they used it to pump water uphill to holding dams in the mountains. Then, during peak period, they would run the stored water back down through a hydroelectric power plant and sell the power back to the French at a profit! Kinetic storage batteries on a vast scale!
OK, pumped storage of surplus energy is ‘good’, but not ubiquitously possible. But splitting water and storing the hydrogen is. Too obvious for words?
Richard and others. Turning water to gas uses more energy than output, no doubt, same as a battery. That was the point of the suggestion, as well as pointing out, by their green methodology it is a viable mechanism, more so than most other suggestions.
Note also according to a recent energy/political report in Germany, most Pump Storage systems are being retired, huh.
The whole energy in/out claim is false. Fill your car with petrol, drive till the tank is empty. Wow, you have used all the energy, none left. not viable???????????????????????. What counts is what you pay. Ask German electricity consumers.
For reliable, efficient and clean power, we have gas, oil, coal , hydro and nuclear. All well proven. On the sidelines, Geothermal and Biomass ( inc natural methane). Wind and Solar need to be retired, or downgraded to packaged domestic units, sold on their price and applicablity
The real aim must be plentiful cheap and clean energy. Full stop.