Image: Christopher Griffith/Trunk Archive
In Brief
- The sun does not shine at night, and the wind does not always blow; methods to store large amounts of energy for downtimes are needed to make widespread solar and wind power more practical.
- Some utility companies already use excess solar or wind power to pump water to uphill reservoirs, where it can later fall to turn turbines; this pumped-hydro approach could be installed in many more locations.
- Other viable energy storage solutions include facilities that compress air into large underground caverns, that heat fluids or molten salts that later create steam to turn turbines, or that can charge advanced batteries. These methods require breakthroughs to make them more efficient so they can compete on price with the cost of electricity from traditional power plants.
More In This Article
To see the big obstacle confronting renewable energy, look at Denmark. The small nation has some of the world’s largest wind farms. Yet because consumer demand for electricity is often lowest when the winds blow hardest, Denmark has to sell its overflow of electrons to neighboring countries for pennies—only to buy energy back when demand rises, at much higher prices. As a result, Danish consumers pay some of the highest electricity rates on the planet.
Utilities in Texas and California face a similar mismatch between supply and demand; they sometimes have to pay customers to take energy from their windmills and solar farms. On paper, wind and sun could supply the U.S. and some other countries with all the electricity they require. In practice, however, both sources are too erratic to supply more than about 20 percent of a region’s total energy capacity, according to the U.S. Department of Energy. Beyond that point, balancing supply and demand becomes too difficult. What are needed are cheap and efficient ways of storing power, to be tapped later, that is generated when winds are howling and the sun is beating down.
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31 Comments
Add CommentI'm rather surprised that David Mackay put his name to this article( perhaps he didn't see the final draft )It is little use writing that"the US stores about 20 gigawatts of power - it doesn't ( What it does do is store energy and the generators that draw from these energy stores can deliver 20 gigawatts of power, but without knowing for how long it is meaningless ). Davide Castelvecchi should know this.Hydrogen does NOT have a higher energy density than gasoline. ( it is more energetic per unit mass, but that is not energy density ) Even with everything in it's favour( fuel cells versus ICE, etc ) as a vehicle fuel you would need 5 ltres of liquid hydrogen ( at 4 degrees kelvin by the way )to equal 4 litres of gasoline.The so called "hydrogen economy" may have been long envisioned,but rejected for almost as long as both dangerous and impractical. Hydrogen gas is colourless, odourless,and burns with an invisible flame.It can also form an explosive mixture with air over a wide range of ratios (4% to74%) Due to it's low energy density it is expensive to transport,making a network of fuel stations more expensive to run. It may in time come to pass as a source for producing fuels.Most,if not all towns and cities have the twin problems of dealing with garbage and sewage. For every kilogram of hydrogen released when electrolysing water,eight kilograms of oxygen are also produced. This could be a valuable resource to incinerate wastes at high temperatures making the process suitable for further power generation, and the co2 released can be retained to be chemically reduced with hydrogen to produce synthetic hydrocarbons both for fuel and feedstock use.I'm not talking perpetual motion here, but long term energy storage is still only practical as chemicals we now have a long history of safe handling
Reply | Report Abuse | Link to thisWe can't ignore the distributed energy storage at the buildings. If renewable energy is going to take off, storing it at the buildings for the times when the sun isn't shining and the wind isn't blowing will be a great help! A smart grid with renewables won't work with dumb buildings. Not to mention, energy storage for air-conditioning at the buildings shift away the troublesome peak demand that is mainly caused by air-conditioning and increasingly being met by intermittent energy sources.
Reply | Report Abuse | Link to thisUnbelievable. Let me get this straight. Sleezoid politicians are shoving this "Clean Energy" SCAM down our throats, at enormous expense, claiming it's "green" and helps prevent Global Warming, which is utter nonsense - it doesn't, and NO it ain't green. So we have "Clean Energy" which = mostly Wind with a smidgen of Solar & Geothermal, at > double the cost of much cleaner Nuclear, installed at a cost of 100's of $billions. Mostly exported jobs. And might last 20 yrs.
Reply | Report Abuse | Link to thisSo next the Pimps are saying, Oh look at all the Wind & Solar we installed at an incredible price, well Nuclear & Coal doesn't mate well with all that wildly fluctuating Wind & Solar - so what do you know, now we have to install NG Fuel Guzzling Turbines to shadow the fluctuating Wind & Solar. Probably 1/2 inefficient OCGTs. What they don't tell you is that 80-90% of the primary energy of the Wind/Solar/NG system will come from NG. And just installing CCGT's without the Wind would use less fuel. The little factoid they don't want anybody to know. Which of course is the REAL REASON Slimey politicians & Big Oil/NG companies are pushing Wind & Solar in the first place.
Now to add misery to madness, to go from insane to to totally bonkers, they are telling us, now we've installed all this Wind & Solar, well what-do-you-know it is basically worthless without storage - go figure. So taxpayers, please fork out more 100's of $billions to add storage to the otherwise worthless Wind Energy. They don't tell you that the storage will cost twice as much as the Wind & Solar costs, which is twice again the price of the Nuclear which they could have installed in the first place, that doesn't need any storage. One ounce of thorium or uranium will supply the average American's lifetime Energy consumption, burnt in a LFTR or an IFR, that's plenty of storage, as far as I'm concerned.
Criminally corrupt politicians. Many persons deserve a long prison sentence for this deliberate SCAM perpetuated on the American people. The whole purpose is to force up the price of Electricity and greatly increase NG consumption, until the Shale Gas bubble bursts, and citizens will be stuck with 100's of GW of fuel-guzzling Gas Turbine Electricity generation, with NG price rising to International levels 5X current domestic prices.
Read about the sordid tale of the Shale Gas Bomb here, from Deborah Rogers:
www.youtube.com/watch?v=bYzU4bEfJ5U
If you don't have the 36 min, at least watch the last 4 mins of the video.
This article is interesting, but disappointingly appears to confuse the difference between energy and power--eg, "Several countries already store considerable power--about 20 gigawatts in the US." I suspect Mr. Castelvecchi means that enough energy is stored to generate 20GW, but for how long? A few minutes? A few days?
Reply | Report Abuse | Link to thisI expected better from Sci Am.
This is a very serious problem and I am glad that Scientific American pays attention to it. I hope that further papers will follow in Scientific American that will go in more depth on how to address this. I have some comments however to the five presented solutions. They do make sense but they all have some serious problems. To my opinion the ideal solution should be to convert electricity to an energy carrier that can be easily stored for longer periods of time. So, some kind of fluid (like gasoline). Storage of a few days is not enough since the sun cannot shine for several days and the wind may be very low when there is a high pressure region. Actually, one should first address the question how much energy storage is really needed and for how long a period. Also this energy carrier should enable to generate easily and efficiently electricity when there is a shortage of wind or solar energy. I think that a paper would be worthwhile that first describes what the desired solution would be and not starting from existing methods and evaluate whether they are suitable or not. And only after that start looking for solutions.
Reply | Report Abuse | Link to thisIt is very worthwhile to address this problem systematically because I expect it will still take many years before we will be able to solve this problem.
The first five commenters must be the ones who started the climategate scandals, or either, they are just idiots. If you build geothermal, hydro and wave generators, and it doesn't take 100's of billions of dollars for each one neither like it does for nuclear, you would not need storage devices. Geothermal, ocean wave, river wave, and hydro generators give you a continues supply of never ending energy that can be put right into our existing grid just like coal, oil, nuclear, and natural gas is now and they are near zero and zero polluting and you do not need to find a place to store deadly radiation.
Reply | Report Abuse | Link to thisFor every geothermal (either above ground or below ground), hydro and wave generator you build, shut down a fossil fuel generator and put that energy straight into the current grid. It is really a no brainer, and since the republicans do not have a brain, it should be easy for them and easy for them to remember.
Put in unlimited investment and max out wind, geothermal, hydro (damn the fish), and wave/tidal (damn the fish again), and you'll replace around 10% of the conventional generating base. What about the other 90%?
Reply | Report Abuse | Link to this"lamorpa", you are drawing for straws in a quickly ending battle. If you had kept up on your reading, you would know that ocean wave generators and river wave generators are now built 'fish friendly'. It is near impossible for a fish to get caught or killed in an ocean or river turbine generator, and bats do not run into wind turbines or get fried on solar panels, they are smarter than that. There are solar panels called 'full spectrum solar panels' that generate energy from any kind of light; they are using them in Germany and Canada where there are very few bright days. Hydro turbines do not deplete our fresh water supply neither. If a million of gallons of fresh water runs through a hydro turbine, a million gallons comes out the other end and the turbines do not kill fish; fish are smarter than that. Apparently, you think that our wild life is as stupid as the deniers are of clean energy.
Reply | Report Abuse | Link to thisMay I recommend an energy engineering textbook to readers to help understand diurnal vs. seasonal imbalances, end-user improvements such as increased thermal mass to deal with those imbalances, and many other issues about which commenters are making strong statements without the required expertise? Vanek and Albright's Energy Systems Engineering comes to mind as a recent resource.
Reply | Report Abuse | Link to thisAlso, if you read the coal-plant-operators' magazine, you'll see that even old coal plants can adjust output efficiently by fiddling with flame height. In other words, natural gas turbine isn't the only technology that can deal with wind intermittency, as long as the operators of boiler plants attend some professional development workshops or read up on new techniques. In even other words, the answer isn't technology, it's smarter people. Rabid polemics like dwdb's here are not convincing anyone, at least not me.
If wind and hydro can only do 10% of our current demand, efficiency will have to take care of 50%, which it has proven it can, and solar can do the next 40%, and we're home in roughly 50-100 years. Of course this is all ruined if we don't manage population growth also.
This same debate was held less than four months ago. See http://www.scientificamerican.com/article.cfm?id=energy-storage-role-in-electric-grid
Reply | Report Abuse | Link to thisI suggest people check that article & posters contributions & responses.
There are a number of serious flaws in this article. First of all, Denmark has high electricity prices because of heavy taxes on electricity, not because of wind energy. As this article explains, "Pre-tax price for electricity in Denmark is generally lower than European averages but the final electricity price is among the highest. That is because Denmark is among the EU countries with the greatest taxation of the electricity price for private households. For a typical user the share of tax of the electricity price was 57.8% in 2006."
Reply | Report Abuse | Link to thishttp://www.alice.uni-oldenburg.de/download/denmark_080511.pdf , page 10
The argument that energy storage is essential for accommodating wind energy doesn't hold water either. Every analysis that has examined the issue has concluded there is already sufficient capacity and flexibility built into the U.S. power system to accommodate wind and solar penetrations dozens of times higher than we currently have today. When wind and solar plants are distributed over large areas, variations in their output tend to cancel each other out. In addition, electricity demand already varies by a factor of three or more depending on the time of day and year, and many changes in wind and solar output simply cancel out opposite changes in electric demand. For any remaining variability, grid operators use the same flexible resources that they use to accommodate variations in electric demand and unexpected outages at conventional power plants, which tend to be larger and more rapid sources of variability. Energy storage technologies are one option for providing that needed power system flexibility. For more, see:
http://www.awea.org/learnabout/publications/upload/Energy-Storage-Factsheet_WP11.pdf
Also, this joint statement between the Electricity Storage Association and the American Wind Energy Association does a good job of highlighting some of these common misconceptions about both of our technologies:
http://www.awea.org/newsroom/pressreleases/Joint-Statement-of-the-American-Wind-Energy-Association-and-Electricity-Storage-Association.cfm
Michael Goggin,
American Wind Energy Association
Reply | Report Abuse | Link to thisWhat I do know is I can make my own power for much less money with RE. while one needs to know what they are doing, one should because it's how the smart people will get theirs.
PV laminates are now $.50/wt!!! Just 10 minutes to install a junction box and you have dirt cheap power. Or ready to use PV for $1/wt is still more cheap than retail coal, nuke, etc. sunelec.com among others.
I'm building 2kw windgenerators for $2k/kw list price. A home with a WG and 2kw of PV with 10kwhrs of lead battery and grid-tie inverter, can supply an eff home for 25-50 yrs on under $10k. Charging the batts at night and selling peak power pays for them and a profit, wind when it happens and solar tracks perectly with demand making it the most valuable power, profit.
Notice no one ever mention the huge amount of generation needed to back up nukes? Just ask Progress when the murdered their nuke and has cost millions to replace.
Nor about having more than 25% nukes that can't turn down forcing France to even pay others to take their massive surplus power.
Standard grid has a 4-1 ratio peak to low power so already set up to handle variability in demand, the same thing as supply as far as handling it. So any power you can't shut down can't be more than 20% of peak like nukes.
The amount of energy in the grid means there is no way using storage will help other than in the margins. On the other hand EV's with V2G could suck, stop or pump power from/into the grid as needed once enough of them are out there. And yes the problems were worked out 15 yrs ago in the Ford E-Ranger that had it standard by ACPropulsion.
If you all want to get screwed by the grid, go ahead and I'll make my own for far less.
Your home scheme is fine if you disconnect from the grid. Remaining on the grid for backup means other users are in effect subsidising you.
Reply | Report Abuse | Link to thisUnbelievable is right. "Wildly fluctuating" solar energy? What? Solar is incredibly predictable, and mates perfectly with coal. Every watt generated by solar is one little lump of coal not burned. Why is this so hard to understand? Nobody says solar can replace traditional energy. Just that more solar means less coal.
Reply | Report Abuse | Link to thisWhy does solar shove right-wingers into apoplexy? Investment returns, that's why. The big bucks are in utility monopolies rolling out nukes for profit now, socialized public dismantling later, private coal power profits now, socialized slag pond cleanup later. No thanks.
I have 3.4KW of solar on my roof that generates more than I can use from 9am to 5pm exactly when it's needed most by cities such as mine. Predictable as the day is long. Literally. How is this a "scam" by any definition?
Hope your Heritage check clears, FUD-er.
Thanks for interjecting a bunch of loaded words and heated rhetoric that's fairly light on facts. I now know why renewable energy haters NEVER have facts to back up their silly arguments....it's because THERE ARE NO FACTS TO BEGIN WITH! Either the angry man on the News Channel / radio show / blog TELLS you that clean energy is bad or you're PAID to make people think it's bad.
Reply | Report Abuse | Link to thisSo, if nuclear power is SOOOOO great, what's keeping history from repeating itself?
http://seattletimes.nwsource.com/html/opinion/2008082460_nukeop31.html
This sad tale is just one of many that happened in the 70s and 80s where grandiose plans collided with fundamentally flawed technology, leaving ratepayers holding the tab TO THIS DAY.
"Like most nuclear projects, the Supply System's plants took far longer than expected to build while cost estimates ballooned...The Supply System was approaching financial hell in the early 1980s. The disastrous brew of construction delays, cost overruns, public suspicion and declining demand put the agency in an untenable position. The plants, initially slated to cost about $4.5 billion, were estimated in 1981 at $23.9 billion."
And that's $23.9B in 1981 dollars! Is that like $40B today? Unbelievable!
Sure LFTR is promising, but it's AT LEAST 20 years away from commercial viability, regardless of all the pretty pictures and slide shows LFTR boosters put forward. So when you say "Nuclear Power" in your heated rants, you have to qualify it by saying "experimental, commericially unproven, might be ready for prime time after 2030 Nuclear Power" because you DEFINITELY aren't talking about the expensive and dangerous LWRs we're building today.
Ok all I can read is the preview but I just wanted to add something. Denmark has the most expensive electricity tariff, and unless I'm reading it wrong that means highest tax on electricity.
Reply | Report Abuse | Link to this"because consumer demand for electricity is often lowest when the winds blow hardest, Denmark has to sell its overflow of electrons to neighboring countries for pennies—only to buy energy back when demand rises, at much higher prices. As a result, Danish consumers pay some of the highest electricity rates on the planet."
Not sure if that's a factually accurate statement. Especially considering wind farms are generally consumer owned, and the people who own them generally get a reduced bill, if not a bill that's replaced by a check. It's also unclear if the statement rests on monetary differences. So having a strong currency doesn't mean you pay more, even though technically speaking your spending more U.S.D per whatever the metric for electricity that is being used. In any case, the statement seems rather suspect.
I remember reading that wind power or solar power (either one alone) could meet all current energy needs for the US (but not for some more densely populated countries). Geothermal power could supply about 5 times current energy use in the US, and could supply current needs for most countries. (This assumes deep well geothermal, which is more expensive than using favorable sites where the hot rocks are very near the surface.)
Reply | Report Abuse | Link to thisWe should not assume that current needs will suffice for the future, though. Energy use per capita is likely to increase, and the number of people is, unfortunately, going to continue to increase as well. Eventually we will need something new and better, possibly fusion, or possibly space-based generating stations.
It is not valid to compare the market price of coal, oil, natural gas, or nuclear power to the market price of clean renewable energy sources, because the dirty sources are massively subsidized -- none more so than nuclear. In fact, nuclear power is so financially risky that private investors will not invest in it at all without a 100% government guarantee! In effect, that is a very great subsidy. So is shifting the cost of disposing safely of radioactive waste to the taxpayers. Finally, nuclear advocates like to ignore the fact that uranium is a finite resource, and already becoming more expensive due to lack of supply. Nuclear is not a renewable energy resource. At best it would be a bridge technology allowing us extra time to build real renewable infrastructure, which will take time. Fossil fuels are finite, and rapidly being depleted. Change is inevitable.
For hydrogen, I think a simple solution for reconverting the hydrogen to electricity is being ignored. Fuel cells are expensive and fragile. But it is not necessary to use fuel cells (except maybe in space ships, for safety). We could simply burn the hydrogen -- recombine it with the oxygen for maximum efficiency -- and use the heat to boil water. Steam generating technology is well established, simple, cheap, and reliable. (I am not sure if it is as efficient at recovering the energy required to hydrolize the water as a properly operating fuel cell, but the fact that it is so much cheaper and simpler might make up for that.) Storing the hydrogen (and oxygen) is still a real issue, which might make the home-based proposal impractical. But if this can be solved, the waste heat produced by a steam generating system could be used to heat the building or hot water, and thus not wasted, at least in Winter.
we can harness energy from wind but when it stop it stop..
Reply | Report Abuse | Link to thisif we can harness energy from wind ..
we can too from a electric fan, it wont stop blowing!..
say we have three turbine next to each other
first turbine for the fan alone..
second one for the house
third one you can sell it to DWP...?
One problem with a hydrogen economy is a distribution system. However, hydrogen could be shipped in current natural gas lines up to 15% with the natural gas. Using a semipermeable membrane at the receiving end (residence or business) the hydrogen could be recovered for use in a fuel cell to generate electricity. A major advantage would be decreased load on the electrical distribution grid from distributed generation.
Reply | Report Abuse | Link to thisGreen-energy haters are almost always right-wing, religious-nut and Conservative Repuglican types, mindlessly doing minion-work for the Heartland Institute.
Reply | Report Abuse | Link to thisIt's so very obvious that green-energy in all it's forms is being squelched by the Koch Bros. and Exxon. They positively hate the Earth, because the Earth is female and is need of contraceptive health-care.
That's very perceptive of you, to note the relationship between Conservative Republicants, Fem-bashers and Earth-haters.
Reply | Report Abuse | Link to thisRush Limbaugh, in his ongoing quest to deny human females the human right to save the Earth through infanticide, is a Earth-hater as well.
OK, so this may be a stupid question, but here goes. If pumping water uphill is a way to store energy for later use (by letting it flow back downhill again), would it also be possible to store energy by pushing some other heavy object uphill and using gravity to release it later? I mean, obviously it would be possible, but would it be an effective storage mechanism? Windmills, funicular railroads, heck even elevator shafts… Big weights that go up when the intermittent energy source (wind, sunlight) is available to power the lift, and down when the energy is needed. As they fall they drive a turbine. It seems to me too that this approach is both eminently scalable, from individual homes or office buildings to large arrays at, for example, wind farms, and adaptable to a much wider variety of settings than the pumped water approach.
Reply | Report Abuse | Link to thisSo my question is, is there something about water that makes it more effective in this mode of storage or energy transfer? It seems to me, with my limited knowledge, that the big issues would be density and friction. The denser the object the greater the energy required to lift it and so the greater the energy stored when it’s in the “up” position—right?. And it seems there are lots of solids out there much denser than water. The other is friction: as the object falls, transferring its kinetic energy to a turbine is subject to some loss. Is there something about the way water flows through and drives a turbine that makes it more efficient at this transfer?
But as I say, I don’t have the background in physics to figure this out, so maybe I’m barking up the wrong elevator shaft…
@Eric I agree with you on several issues. I'm working for a company focused on production of methanol from solar (or wind) energy and ambient air. Ideally from direct photon-energy. This system does not have the impractical and safety matters of hydrogen. We started looking at large scale applications for production of methanol as transportation fuel but now we have shifted our focus on home-application where the (average) energy consumption is one of the leading factors. This in order to keep the size and price of such a system as minimal as possible.
Reply | Report Abuse | Link to thisto my understanding even compressed at 700Bar hydrogen has lower energy density than gasoline (8,5 vs 34 MJ/L). the end of article suggests the opposite though. I'm wondering if I'm missing something here?
Comment 20 about euthanasia was posted by someone who registered and duplicated my username. Please disregard this comment by someone who is too afraid to use their own name or penname.
Reply | Report Abuse | Link to thisAgain, sorry, but this is the impostor InquiringConstructivist. I, the real user, would avoid such attacks and hyperbole. Hopefully the webmaster here will remove or change the other poster's name.
Reply | Report Abuse | Link to thisAlthough sault is one of my protagonists, I deplore the fact that he also has suffered the same hack attack. You need to point out the problem to SCIAM. They deleted the offensive posts that ostensibly had come from sault. In doing so though they also deleted his post complaining about it.
Reply | Report Abuse | Link to thisYour question is not stupid. The weights you see on some old clocks were storing gravitational energy. The problem is the quantity of the commodity, be it water or any other matter, required to give you meaningful storage. Height is just as important. Water has the advantage that it can be pumped up through relatively inexpensive piping. If you look up horsepower & foot/pounds it would probably be the quickest way for you to learn about it. Joules or BTU definitions will also help. Only by asking & inquiring do you learn. Thinking about these things leads to understanding many other things.
Reply | Report Abuse | Link to thisThanks, Carlyle, I did email the webmaster yesterday and they said they're working on banning/deleting the user, and that I should report the false posts for moderation.
Reply | Report Abuse | Link to thisIn the midst of confusion, I think you also confused protagonist and antagonist. Heh.
It was truly childish of our mystery guest to equate population control with euthanasia. Also, sarcasm does not work well in print without excellent writing, so I hope in the future they leave it to Wilde or Eliot.
To Daviso, I was surprised to find out how efficient the water pumps and turbines are that we we use here in New York State to smooth our grid. If you look at the peak 15-minute prices of wholesale electricity on hot summer days, you'll see how much local utilities would prefer to have such storage.
Biomass pyrolysis converts biomass into diesel (or hydrogen and char) which can be stored and used in generators when other sustainable sources are not producing. See Agila, BTG-BTL, Ensyn or Eprida for details. And it is financially viable!
Reply | Report Abuse | Link to thisNorth America has the biggest site in the world for Pumped Hydro. Energy storage problem solved. It's called Lake Erie and Lake Ontario. Allow +/- 1 foot and you can run a 250,000 MW pumped hydro plant. Easily enough for all of North America.
Reply | Report Abuse | Link to thisIf everything was that easy....
If Denmark, has this alleged problem, then imagine Panama: their OCEANOGENIC POWER is no obstacle to the invented, U.S. energy independence; takes away meaning that USA will be begging favors from banks of which are the owners; and worse, that its owners are trying to deceive everyone, including the village of USA, to justify obsolete economic systems based on accumulating money, and logically, as the same is limited, sooner or later it will run out, or will have to be inflated.
Reply | Report Abuse | Link to thisTo those who do not want or may not innovate, by being thinking only about stupid wars, I suggest suggest, to their creatives trusted, that an economy and infrastructure that accumulates the TRUTH and his beauty, is the irreversible future. We're just waiting for the disappearance of these suicidal stances.
By the way, with the renewable energy, OCEANOGENIC POWER of Panama, cheap, reliable, and abundant; storage of hydrogen and oxygen would be the end of the line. So even liquefy it is not necessary. For transportation would be used butane, precipitate of methane, taken of garbage from the cities, and / or vegetation, produced for that purpose, and also for the same market or user who wants to. All this, thanks to that same cheap energy, brought from Panama with superconducting lines, coaxial, and half wave.
What is the real obstacle? This is not good, nor for weapons, nor for stupid wars. I'm not opposed to guns are useful tools, what I am against is of the fanaticism of any kind.