A Free-Market Energy Blog

Energy Density is Key

By Richard W. Fulmer -- April 3, 2010

When it comes to power, density is the key. Energy density. The reason that solar power, wind power, and ethanol are so expensive is that they are derived from very diffuse energy sources. It takes a lot of energy collectors such as solar cells, wind turbines, or corn stalks covering many square miles of land to produce the same amount of power that traditional coal, natural gas, or nuclear plants can on just a few acres.

Each of these alternative energy sources is based on mature technology. Agriculture and fermentation have their roots in prehistory, windmills date back at least to 65 B.C., the photovoltaic effect was discovered in 1839. Yet nowhere in the world are these technologies serving as primary energy sources without significant government subsidies. While incremental improvements can be expected, what is needed for them to become viable is an order of magnitude increase in productivity. As old and as well-researched as the technologies are, such improvements are possible but unlikely. As significant future energy sources these technologies are dead ends, which is why the government, and not the private sector, is funding them.

Industry is more than willing to risk research dollars on technologies that show real promise, but it is not willing to flush shareholder money down a rat hole. Politicians, however, operate from different incentives. When a crisis, real or imagined, makes headlines, they want voters to see them doing “something” about it, and they must move quickly because election cycles and constituent attention spans are short. Funding long-term research in promising technologies is not sufficient to meet politicians’ needs. Solar panels, wind turbines, and ethanol refineries are all current technology, and can be erected quickly with fanfare and photo-ops. By the time these alternative power sources prove to be financial and, possibly, environmental busts, the politicians will have been reelected and voters’ attention will have shifted to the next crisis.

Another benefit of subsidizing “shovel ready” solutions is that existing technologies have existing supporters who can provide campaign funds. Such supporters, however, constitute a well-financed “status quo” that will make government funding, once started, difficult to end. For example, even though corn-based ethanol has driven up food and fuel prices, increased auto emissions, raised atmospheric carbon dioxide concentrations (by causing additional acreage to be tilled), and possibly resulted in net energy losses, the government is still subsidizing the industry and still requiring that the fuel be added to gasoline.

Wind energy, for its part, has been “just a few years away” from being economically competitive with conventional power for at least the last 25 years, and this will not change any time soon. The Energy Information Agency predicts that in 2016 wind power will still be 49% to 77% more expensive than electricity from either coal or natural gas. Furthermore, because wind turbines work only when the wind blows, wind farms cannot replace conventional plants. Backup power from conventional sources, usually gas turbines, must be ready to come on line the moment the wind fails. Despite these fundamental problems, subsidies continue to flow thanks to an entrenched lobby.

By contrast, consider the significant oil industry investments in researching biofuels made from algae. Unlike ethanol, biofuels are chemically similar to fuel made from petroleum and, like petroleum-based fuels, have a significantly higher energy content than does ethanol. Biofuels can also be handled by current fuel distribution systems and can be burned in today’s vehicles.

Algae can be grown in brackish water on desert land and, with today’s technology, can produce over 2,000 gallons of fuel per acre each year. This compares favorably with the approximately 250 gallons of ethanol that can be produced from an acre of corn – a ratio of 8 to 1. Accounting for the differences in BTU content, the ratio jumps to over 12 to 1. It may even be possible to boost productivity to 100,000 gallons per acre per year, raising algae’s potential to over 600 times that of corn-based ethanol!

Biofuels are carbon neutral because the carbon dioxide released when they are burned is first extracted from the atmosphere by the algae. Unlike burning petroleum-based fuels, then, burning biofuels will not result in a net increase in atmospheric CO2 levels.

With algae’s vast potential, it is easy to understand why private industry is interested, and why no government subsidies are needed to encourage investment. Moreover, if algae-based fuels do not prove viable, the companies now researching them will have no “status quo” problems with ending their investments and shifting scarce resources to more promising technologies – where “promise” is measured in density.


This piece originally appeared in The Freeman (January/February 2010). Mr. Fulmer is co-author (with Robert Bradley) of Energy: The Master Resource (Kendall/Hunt, 2004).


  1. steve  

    Gee, too bad you didn’t consider the costs of the pollution of the fossil fuels that you give as examples. Then maybe wind could compete with coal.


  2. Matthew Sinclair  

    Great post. I really like the simple, sharp explanation at the beginning; a really strong analysis of the fundamentals.


  3. Jon Boone  

    Even with the pollution externalities factored in, wind couldn’t begin to carry coal’s bat and glove. With wind, it’s not just its vaporous energy density that is problematic; it’s the relentless variability, which must be continuously infilled with, mainly, more energy dense fossil fuels, thus reducing the externality gap to virtually nothing.

    What is it with people who continue to compare wind with conventional generation, not understanding that such a metric is like comparing a fish to a bicycle?


  4. Levi  

    50% or so more expensive is really not all that expensive, and many people can afford it. Probably a bigger problem is the lack of infrastructure, both to generate the power and to use it for transportation. Problems with variability can be solved with overlapping technology such as solar, wind, tide, or whatever. Maybe in a few years, once all-electric cars have some public exposure, this problem will look a little different.


  5. Richard W. Fulmer  

    Coal’s pollution costs have been factored into its price to a large extent by laws requiring scrubbers on all coal-fired power plants and regulations requiring top soil restoration at strip mines.

    No matter how high we price coal, however, it will not make coal power plants intermittent energy suppliers nor wind turbines constant suppliers. Because wind turbines are not reliable, they must be backed up, and only natural gas turbines can be fired up quickly enough to serve as back ups.

    Wind turbines are conceivable as primary power supplies only because of the availability of fossil fuels. We can no more have wind power without natural gas than we can have rain without clouds.

    Why cling to such unpromising technologies as wind, solar, and corn-based ethanol with all of their inherent problems when alternatives like algae-based fuels have so much potential?


  6. chris y  

    The 100,000 gallons/acre/year claim for biofuels derived from algae is specious nonsense. Energy efficiency of photosynthesis and typical solar insolation averaged over a year in the southwest U.S. could potentially provide 8000 gallons/acre/year. Production costs today are $100/gallon. Future production cost estimates are pure WAGs. Large scale demonstration plants are still a far-off dream. But hey, algae biofuel sure does attract venture funding!


  7. Jon Boone  

    “Problems with variability can be solved with overlapping technology such as solar, wind, tide, or whatever.”

    Solving problems of variability with–uh–more variability is a pitch perfect slogan for our times….


  8. Tom Stacy  

    “Industry is more than willing to risk research dollars on technologies that show real promise, but it is not willing to flush shareholder money down a rat hole.”

    Unfortunately, this is not as true as it used to be. With government offering up “profit insurance policies” for the unprofitable, why would the smart money invest in any technology without similar assurances? I am afraid our government’s willingness to punish the most affordable and insure the profitability of the unaffordable has neutralized most free market investment for now. An exception is reactive power whose margins and utilization increase with the use of more intermittent resources like wind and solar.


  9. Richard W. Fulmer  

    Interesting. Please provide your sources. Thanks!


  10. Jon Boone  

    And nothing seems to demonstrate Tom Stacey’s point better than the “commitment” that GE, Siemens, AES, BP, FL&L, among others, have made to “renewables” like wind technology. The warped synergy is perversely poetic. These companies invest in wind for government-insured tax avoidance, providing dysfunctional energy service and generating unmerited public relations fodder. The taxes not paid mean that taxpayers must pay more or that they will receive diminished services.

    Il buco di topo (the hole of the rat) uber alles.


  11. Donald Hertzmark  

    Good post. Two points: (i) the wind backup situation is sometimes even worse than you (we) think – in at least one state (CO) wind is backed up by cycling coal-fired plants – the worst of both worlds with regard to emissions and fuel use; (ii) your post is a concise practical restatement of the second law of thermodynamics – to obtain work from a low quality energy source one needs an infinitely large heat exchanger. Substitute, wind farm, solar array, Tx system for heat exchanger and you get the idea. It is never a good plan to fight the second law.


  12. Rick Row  

    I’m having trouble getting excited about algae and its biofuel. Converting your numbers into watts per square meter, I got 2.13 watts/sq. meter, which compares unfavorably with concentrating solar power that generates about 15 watts/sq.meter (David MacKay’s number on page 177 of ‘Sustainability-Without the Hot Air’).
    In case my arithmetic was poor, I used the following conversion factors:
    1 acre = 4047 square meter
    1,056 joule = 1 Btu
    31,536,000 seconds = 1 year
    1 watt = 1 joule/second

    You’re going to have to run the respective capital and operating costs to convince me that algae biofuel would be a better deal than concentrating solar power electricity for an energy source out in the desert.



  13. Richard W. Fulmer  

    We have two main power needs: electricity and transportation.

    As you point out, solar cells convert sunlight into usable energy more efficiently than do plants. If we were interested only in producing electricity and if our only two choices were solar cells and algae-based biofuel, I (like you) would choose solar cells. We’re not limited to two choices, though. There are other, far more efficient and eco-friendly ways to produce electricity, such as nuclear and natural gas. Each is much cheaper than either solar or biofuel, and each has a much smaller footprint.

    Neither solar cells nor nuclear power plants are of much use in supplying our transportation needs, however. While electricity can power mass transit, mass transit is expensive and inflexible. Electric power can also be used to charge batteries and to generate hydrogen. Even after over 100 years of development, though, battery-powered cars are still not practical. Batteries cannot yet store enough power, they take too long to charge, they contain some nasty chemicals that create disposal problems, and they’re very expensive.

    Hydrogen has an energy density problem of its own. For a hydrogen-powered car to have the same range and cargo capacity as a gasoline-powered vehicle, its hydrogen storage tank would have to be pressurized to tens of thousands of pounds per square inch. Even if we could achieve such pressures, we wouldn’t want to be anywhere near such a tank in the event of a car accident. Were it to rupture, the resulting explosion would level a city block.

    If we’re looking for a reasonable replacement for gasoline and diesel, then, algae-based biofuels are worth a look. The oil companies think so too, and are putting up hundreds of millions of dollars to take a peek.


  14. Densidad de energía es la clave  

    […] Cuando se llega al poder, la densidad es la clave. Densidad de energía. La razón por la que la energía solar, energía eólica y el etanol son tan caros es que son derivados de fuentes de energía muy difusa. Se necesita una gran cantidad de colectores de energía, como células solares, turbinas de viento, o tallos de maíz que abarca muchos kilómetros cuadrados de tierra [. . . ] URL del artículo original http://www.masterresource.org/2010/04/energy-density-is-key/ […]


  15. jsm  

    there are some good points here.

    but to say that pollution externalities have been priced into coal is either ignorant or dishonest. the coal industry has managed through substantial funding to reduce any pollution controls to a bare minimum. “mountaintop restoration?” are you kidding? does the mountain look the same as before and house diverse ecosystem? hardly. there is some “coal scrubbing” going on, but a significant percentage of coal plants in operation are grandfathered and don’t have to bother with such regulations. the ones that do have huge toxic sludge pits whose remediation is suspect as best. and certainly there is no co2 priced into the costs of coal.

    coal is incredibly dirty business and “clean coal” is really not cleaner either. comparing wind to coal is indeed like comparing fish to a bicycle.


  16. The Energy Density Problem « Stall Talk  

    […] Here is an article that lays it out nicely. […]


  17. C4P  

    It’s not just the energy density that matters, this analysis just gives a part of the picture, and energy density by no means “the key”. You also need to deal with the quality of energy. When you are coming from any source such as hydrocarbon, the amount of energy which you can extract will be limited by the Carnot efficiency. So has anyone really calculated how much energy you have to live with releasing to the atmosphere, no matter what you do in a coal powered plant and how in-efficient it is? Or that only 2% of energy produced by gasoline is actually used in transporting me from point a to point b? What use is the energy density if there is a limit to what we can extract? http://www.carbon4profit.com


  18. Phil Bongard  

    The appropriate hope to place in algae is closed system photo-bioreactor technology that can plug out an easy 15,000gal/acre/year….that number has been tested and proven as a safe projection….that still makes algae based biofuel much more promising than using our food supply as gas, and it is much more efficient per acre per year anyways. So why not put the money into it now? Its perfect timing. plug them into CO2 outputs on power plants…there is some more energy…


  19. Steve Stillwater  

    Great post, showing why fossil fuels are so difficult to replace at reasonable cost. They are, in fact, concentrated sources of energy, relatively easy to store, transport, and use.


  20. Joe Lepip  

    “Or that only 2% of energy produced by gasoline is actually used in transporting me from point a to point b?”

    What? In an internal combustion engine, the losses are about 63% (due to friction, pumping air into and out of the engine and wasted heat). 15% of the energy propels your car along the road. The difference (22% is lost in air conditioning, drive train inefficiencies, idling etc.) . Diesels are 30 to 35% more efficient.


  21. Smarter Energy Policy Made Easy – Go Wood  

    […] and those forms can be evaluated in the form of energy density. Nuclear energy is extremely dense, solar and wind power are at the other extreme, very diffuse. That means that the area of production to generate a certain amount of power from the […]


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