Burning energy questions – ERoEI, desert solar, oil replacements, realistic renewables and tropical islands

Late last year, Tom Blees, I and a few other people from the International Award Committee of the Global Energy Prize answered reader’s energy questions on The Guardian’s Facebook page. The questions and answers were reproduced on BNC here. Now we’re  at it again, this time for the website Eco-Business.com (tagline: Asia Pacific’s sustainable business community). My section is hosted here (Part I), and Tom’s here (part III).

Part II, which I don’t reprint, answered by Iceland’s Thorsteinn Sigfusson, covered the relationship between large-hydro and climate change, and why solar conversion isn’t used more extensively.

I’ve reproduced my and Tom’s answers below.

—————————————

Barry Brook’s Q&A

Sunil Sood: What are the “Real Energy Payback Periods” for Solar PV and Wind Energy Systems? Taking in to account the energy consumed during manufacture of components, balance of systems, transportation, installation, servicing and variations in availability of energy and usage patterns, actual life expectancy (not theoretical).  Are we consuming more of ‘Dirty Coal’ to produce these so-called ‘Clean’ energies?

Calculating true energy paybacks are tough. Every energy system has initial investments of energy in the construction of the plant. It then must produce energy for a number of years until it reaches the end of its effective lifetime. Along the way, additional energy costs are incurred in the operation and maintenance of the facility, including any self-use of energy. The energy payback period is the time it takes a facility to “pay back” or produce an amount of energy equivalent to that invested in its start-up. A full accounting of energy payback includes not only the materials and energy that are input into the extraction (mining) and manufacturing processes, but also some pro-rata calculation for inputs into the factory that constructed the power generation facility, some estimate for human (worker) inputs, etc. As you can imagine, it can be difficult to fully integrate all possible inputs.

However, there are reasonable ballpark estimates for a range of technologies, including wind, solar PV, solar thermal and nuclear. Material inputs tells one part of the story, and some attempts are a standardized comparison are given here and here for a few technologies (wind, solar thermal, Gen III nuclear). As a short-cut for estimate of total energy-returned-on-energy-invested (ERoEI), we can use studies that have looked at the life-cycle emissions of alternative technologies, and then calibrate these against the emissions intensity of the background economy used to produce the technology. This gives us an approximate ERoEI. Based on a range of studies, the estimates range from 180 to 11 for Gen III nuclear, 30 for wind, 11 for solar thermal and 6 for solar PV. That is, your PV panels would repay their inputs 6 times over during their lifespan, and if they lasted on your roof for 25 years then the payback time is about 4 years. If a nuclear plant had a ERoEI of 50 and operated for 40 years, its energy payback time would be 10 months.

Sophie Hughes, General Manager, CPR Sustainability, Sydney: As we battle with NIMBY-ism and planning issues, should international governments be focusing on building large scale renewable energy projects in uninhabited areas, such as central Australia or the edges of the Sahara? Is this feasible and does this mean that we need to focus more efficient infrastructure and storage capacities, rather than being dazzled by the technologies themselves.

All energy technology options have their pros and cons, and so investment decisions should ideally be based on a set of logical, consistent and unbiased criteria. This should include considerations of cost, externalities (e.g., CO2e emissions and toxins emitted per MWh of energy), technological maturity, dispatchability, reliability, safety, energy returned on energy invested, sustainability and security of material inputs and fuel, facility lifespan, land use, public acceptability, and so on. Typically however, many (most) of these are left out of decision making – public and private. As an example, a recent analysis of the ‘fit-for-service criteria’, life-cycle emissions and levelized costs of technology options, can be read here, here and here.

So, as to the specific question, it would make sense for governments to invest in large-scale desert-based solar plants if, on the basis of a rational analysis using these criteria, it was shown to be a superior option compared to alternatives. At present, desert solar has many large uncertainties, especially in terms of cost (including transmission from remote locations), amount of energy storage required, and technological maturity. My view is that it is worth developing, via multi-lateral funding and RD&D initiatives, a number of large demonstration plants for a range of new renewable and next-generation nuclear technologies – and then on the basis of performance, governments and the market can work together on commercial deployment. For a checklist of what types of details any large-scale alternative energy plan should (ideally) cover, see here.

Susan:  Given that oil is a finite resource, and our society is unlikely to re-invent itself, what is the most exciting development that you see that has the potential to replace our dependence on oil?  And, what are the difficulties in getting solar power from remote areas, like the Sahara Desert or the Australian Outback – identified as some of the best solar sources – to the places where people actually live? Is there anything new on the horizon that may improve this?

Oil will ultimately be replaced by some mixture of batteries, synthetic fuels, exotic energy carriers and, probably, small modular nuclear reactors. Desert-based solar could, if proven economic, be used to generate hydrogen from water via electrolysis or direct heat processes, as could nuclear heat or electricity. Pure hydrogen can be difficult to manage and transport, however, so derivatives such as hydrogen-nitrogen (e.g., ammonia, hydrazine) and hydrogen-carbon synfuels (e.g., methanol, dimethyl ether) may end up being preferred. See here for some detailed discussion of the many potential applications for ammonia. Batteries using lithium air or other advanced technologies will likely be increasingly used for passenger vehicles. There are also serious concepts for using refined metals like boron in a closed B-O cycle as a totally recyclable energy carrier for combustions engines (just add heat to recharge).

Large transport fleets like rail will move increasingly towards electrification, and ship-borne cargo transport will probably depend more on small nuclear reactors rather than huge diesel engines – as the Russian private ice-breaker fleet already does. As to transmission of electricity from remote locations to high-demand centres, the current limitations are cost – $1 to 10 million per km for Ultra-High-Voltage Direct-Current lines (UHVDC), with the actual cost depending on the power rating and other factors (huge generation facilities would require many lines). Some exciting work is being done in the area of high-temperature superconductivity, but this is many years off commercial application.

Tom Blees’ Q&A

Brooks Keene: The IEA has more or less acknowledged that global oil production has or will soon peak (see here). What implications does this have for the need to decarbonize our economies, and what role can businesses play in leading the way towards creating policy frameworks that create the right incentives for navigating the road ahead?

While there are different opinions for when the world reaches “peak oil”, most agree that we either have already hit that mark or will soon do so. Assuming that’s the case, the response of businesses depends to a great degree on what businesses we’re talking about. The oil companies would seem to have little incentive to make major changes (short of prospecting for more oil), since their costs are always passed on to consumers, in either shortages or gluts. They’re looking at many more years of virtually guaranteed healthy (if not obscene) profits as long as the majority of transport depends on gasoline, diesel, and aviation fuels based on petroleum.

That being said, gas companies have a tremendous incentive to take advantage of concerns about peak oil, especially now that fracking is expanding almost exponentially. The push to convert automobiles and other ground transport to compressed natural gas has been with us for a while and can be expected to increase, especially if fracking continues to expand–though anti-fracking pressures based on environmental concerns may affect that, in some countries more than others.

Though some environmentalists have embraced natural gas as an alternative to coal in electrical generation, this is a Faustian bargain that is driven more out of desperation than logic or conviction. Those who are pushing the hardest for an all-renewables future know that they need what is euphemistically called “backup power” for when solar and wind facilities aren’t producing. How one can call the system that provides about 75% or more of one’s energy “backup” is a mystery, but so it is in today’s energy politics.

The hard data available to date indicates that the only way we can decarbonize—eliminating both oil and gas—is to employ nuclear power as backup, and to devise methods of using renewables plus nuclear and biomass to make the transportation fuels we need, in addition to the electricity that our societies will come to depend on more and more in the future. Businesses not directly involved in the energy sector have few options in terms of directly affecting the course of energy policy. Sure, we see some businesses putting up solar arrays or making other politically correct token gestures, but these are window dressing that relies on subsidies, not really consequential in the effort to decarbonize human energy systems. The decisions that matter will be made within the energy sector, and those decisions will continue to accommodate the fossil fuel industries—be they coal, oil, or gas—unless governments lay down the law and force through policies that make it impossible for the status quo to continue. Carbon taxes are a first step, but support for a massive buildout of nuclear power (as we see in China today and to a lesser degree in some other countries) is critical to making progress in cutting greenhouse gas emissions in a meaningful way.

Shadi Saboori: What would be an optimal way to create incentives for businesses to transition to renewable energy? (And one that is politically realistic).

This is touched on in the previous response. Assuming that the term “renewable energy” doesn’t include nuclear power, the options for businesses that wish to transition to renewables are dictated primarily by the degree of subsidization offered. Customer demand is also a factor, such that if a company believes that hyping their green credentials by putting solar panels on their roofs will help business, then it’s more likely that they’ll take that step even if it costs them money in the long run. Thanks to generous subsidization by many governments, however, businesses can make it a paying proposition because, unlike many homeowners, they have the wherewithal to put up the sometimes fairly large sums up front, knowing that they’ll more than make back their investment over time due to tax deductions, generous depreciation and other allowances, and especially feed-in tariffs.

While all these incentives do encourage businesses to transition to renewable energy, is that necessarily a good thing from a societal standpoint? After all, the only reason that it’s at all profitable for the few companies that do it is because a large base of ratepayers are splitting up the cost amongst themselves (usually unknowingly). In other words, while such deployment (of solar, usually) makes things appear to be progressing in terms of societal transition to renewables, it’s simply not economically rational without the subsidies, so the wealthy (the companies that do it) are taking advantage of the less well-heeled individual citizens. If everyone were to attempt to transition to solar thusly, it would obviously be impossible, since there would be no pool from which the subsidies could be derived.

When it comes to large energy-intensive industries, even massive solar arrays can’t hope to provide the energy they’ll need, which is why some of Germany’s major industries with long histories in that country are either demanding specially reduced electricity rates or threatening to leave the country. Germany, of course, is where renewables—particularly solar and wind—have had enthusiastic government support for the last couple decades or so. Of course when the government cuts a discount energy rate deal with such industries to offset the steadily climbing electricity costs, it transfers even more of a burden onto the shoulders of regular consumers, forcing their escalating rates even higher.

Ultimately, the truly consequential decisions about a nation’s energy policy will be made by governments, with individual businesses moving in one direction or another based on their economic self-interest. And if Germany and Denmark—as the two nations with the longest history of continued government support for non-nuclear renewables—are any guide, the transition to an all-renewables future is nothing we can expect to consider viable in the foreseeable future.

Berend Jan Kleute, Bluerise BV: Island environments have unique characteristics that make them interesting to provide a general view of how possible integration of renewable energy (RE) systems can be implemented. Tropical islands usually have the greater potential of conversion using traditional RE technology (wind, solar) given their resource availability. Unfortunately islands very often lack the luxury of interconnection to a large grid, and the limited space and resources make energy storage and widespread deployment of these traditional RE systems (due to intermittency) unfeasible. The lack of an effective storage/buffer solution limits the penetration potential of traditional RE sources. What role do you foresee for different RE systems, including wind and solar, and in particular baseload RE technologies such as Ocean Thermal Energy Conversion (OTEC) and Seawater Air-conditioning (SWAC) to achieve a 100% energy self-sufficiency of tropical islands?

Even in the most environmentally cooperative islands (breezy tropical settings) wind and solar alone will simply not be able to lead to 100% self-sufficiency without considerable energy storage, not something that’s heretofore been demonstrated at scale except at great expense. OTEC and SWAC theoretically could provide true baseload power, but these two also have yet to be scaled up.

As someone who spent a couple decades working on some of the world’s stormiest seas, whenever I consider the often glib assurances that OTEC and wave power and other such systems will someday carry a meaningful amount of the load in supplying mankind’s energy demands, I cannot help but be skeptical. For while such systems may scale up and perform quite well for months, Mother Nature has a way of kicking up the power of the ocean in ways that are truly awesome to behold, and when that happens even the sturdiest manmade contraptions are often brought to ruin. I suspect it is difficult for many people who hold out high hopes for such systems—or for many of those who design them, for that matter—to truly appreciate what they’re up against. For my part, having experienced hurricane-force winds several times in the Bering Sea and a hurricane in the Caribbean that broke wind speed records, I would have to say that I’ll believe these ocean-tapping systems will work over the long haul when they’ve been deployed and operated successfully for many years.

One technology that I believe will soon be seeing widespread deployment on island groups is plasma converters, which I wrote about in my book Prescription for the Planet. I’ve posted a chapter on this technology online for those who wish to read about it in detail. These systems allow for efficient recycling of virtually everything, being essentially molecular deconstructors. Disposal of municipal solid waste, sewage sludge, discarded tires and other waste is especially problematic for islands, what with limited space for landfills and water contamination issues that can sometimes result. Plasma converters eliminate the need for landfills altogether and allow waste materials to be converted into electricity (usually extremely expensive on islands) and building materials. They also do away with the need for an entirely separate recycling infrastructure, since everything can be discarded in any mix and the plasma converters will sort it all out. Another bonus for island groups that have problems with reef destruction: the inert glassy slag resulting from treating wastes can be used to build artificial reefs, or to augment the surviving reefs.

But even if all the islands’ waste is efficiently converted and the electricity from it is piped into the island grid, there will still be a shortfall. Barring dependence, to one degree or another, on either fossil fuels or nuclear power, I suspect that islands that can manage the cost of substantial wind and solar systems will end up adding the cost of as much storage as they can muster and their citizens will learn to live with energy rationing and occasional failures. Several companies are prepared to provide small modular nuclear power systems, however, that could serve islands perfectly. The Russians are also planning on deploying reactors on barges, and these could also provide all the energy that island groups require. I believe the next couple decades will see more and more island groups turning to nuclear power, which has a very small footprint (or none, in the case of floating or submerged systems), low operating and maintenance costs, and no emissions.

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27 Comments

  1. I agree that OTEC systems are not credible. A calculation based on the Carnot cycle show that the efficiency will be extremely low. For surface water at 27°C and deep water at 4°C, the theoritical efficiency is just 8%. So one would need very low losses in pumps and very few leaks of heat. I just would not start from here!

  2. Carbon taxes are a first step

    I repeat my disagreement from long ago. Carbon taxes are a kind of sin tax, or as I seem to recall from a very serious economics discussion I tried to put my oar into a year or two ago, a Pigouvian tax.

    I tried to say that if you are a person financially supported by government, the problem with Pigouvian taxes is that they make a pig of ou. My comment did not appear.

    The first step, even before new C taxation, is to apply Hansen’s fee-and-dividend scheme to existing fossil carbon revenues, to the fees we’re already paying.

    When carbon tax is proposed, I believe it is met with fear that it will increase governments’ interest in keeping the fossil fuel industries in being. If a precedent is established of returning existing carbon revenues in equal shares to the citizens, this will make less implausible the promise that the revenues from new carbon taxes will also be returned.

    Thank you for mentioning my B/Al paper.

  3. GRLC, you are right. It was sloppy wording from my. I agree with your position.

    EG, yes, I was thinking principally of industrial uses for hydrazine.

    CS, the figures are meant to be guide markers only — the idea is to click on them for an enlarged version, or for a link to the article they come from (if you want more information). For figures/tables that I want to be fully legible, I use a larger, centred format (e.g. see previous post on my Energy Policy paper for legible tables).

  4. Can a link be provided to a legible version of the five energy plans for Britain?

    Thanks for this, Barry. It is especially pleasing to see that it brings together much of the work which has gone into the TCase series and the ammonia storage thread from BNC.

    Well done.

    Now, what about the action plans? Which government is going to be the first to really get behind truly effective action, even if it comes at the cost of reductions to PV and Solar Thermal and similar currently uneconomic programs?

  5. Zachary, it’s tough to know what to make of LENR. In my mind there is not enough solid information to judge. It cannot be explained by known physical and chemical principles (as far as I understand them), so it will require some extraordinary demonstrations before it’s taken seriously by the scientific community. It’d be nice if it was real, but I’m highly skeptical.

    This is the opinion of a highly credentialled nuclear physicist/engineer I know, when asked the same question (in some email correspondence):

    “The Universal Fusion idea is more like a traditional fusion in a micro-scale, which I don’t think will ever work.

    The NASA LENR is a variant of the cold fusion. The cold fusion mania started by Pons and Fleischman in 1989. They proposed cold fusion in New York Times instead of a scientific journal. No one could replicate their claims, but the mania spread uncontrollably. Gary Taubes, a journalist who had been following the cold fusion from its inception, published a book titled, “Bad Science: The Short Life and Weird Times of Cold Fusion,” in 1993. But the cold fusion never died away.

    Ever since, cold Fusion has become a religion — it is a matter of ‘believing’ quite literally. Like in a religion, there is a whole community of believers, who have their own conferences and even their own journals. It is fascinating. And they believe that mainstream science is conspiring against them. It is interesting to note that NASA PowerPoint presentation has a stamp on page 2, “Not recommended for people who follow dogma or have fixed beliefs.”

    There are people who keep coming up with what they claim are new and more results, but the rest of the physics community has been ignoring it. Some claim theirs are not cold fusion but nuclear transmutation — LENR is in that category. At the request of DOE, I once reviewed all day long a new experimental evidence from a reputable university. I decided to stop paying attention — what is the point of digging through a myriad of sloppy experiments to find out where they went wrong? If there were a really convincing (and reproducible by non-believers) demonstration, then they should bring it to the science community through a peer reviewed scientific publication.

    My recommendation is: Don’t pay any attention to any of such claims.”

    Make of it what you will — certainly, time will tell.

  6. Barry, while I am very skeptical of reports of low energy nuclear reaction, my skepticism is of the Carl Sagan variety – extraordinary claims require extraordinary evidence, and we don’t yet have extraordinary evidence. But I will keep an open mind while the process of science follows its course.

    Your correspondent offers not a single substantive reason to reject the recent interesting claims. His comments all boil down to a guilt by association linkage to Fleischmann and Pons, in one way or another. Its understandable, many people were burned by the experience of the first cold fusion claims. But that is simply not a reason to reject newer unrelated work. Its not a valid mode of reasoning.

    He says if there were a convincing demonstration it should be brought into the scientific community in a peer reviewed publication. Well, its not a demonstration, but Widom and Larsen have published a mechanism for a low energy nuclear reaction in the European Journal of Physics C (2006):

    Ultra low momentum neutron catalyzed nuclear reactions on metallic hydride surfaces

    There’s a further half dozen papers in arXiv, listed on this page.

    The mechanism they propose is pretty interesting. It starts by observing that the “Born-Oppenheimer approximation can break down at the surface of metal hydrides allowing electromagnetic coupling of surface proton oscillations to surface plasmon polariton electrons”.

    To put that into plain(er) English, the Born-Oppenheimer approximation says you can neglect the movement of the atomic nuclei when you want to figure out what the electrons are doing. Its an essential approximation that makes most of quantum chemistry tractable. But its only an approximation.

    Widom and Larsen consider several situations where it breaks down. One of them is at metal hydride surfaces. The breakdown of the B-O approximation means nuclear momentum is transferred to the electrons. They describe a mechanism where groups of nuclei moving together transfer momentum to groups of electrons.

    The transferred energy manifests as an increase in the mass of the electron. Widom and Larsen propose the heavy electrons can react with adsorbed protons to produce a neutron. The neutron that results has ultralow momentum and is easily absorbed by a nearby nucleus. If the resulting nucleus is unstable, it decays and liberates energy.

    There is nothing inherently implausible about this mechanism. I’m not able to read these papers at a level that can assess the detail, so I can’t judge if assumptions are invalid or the calculations are correct, so I’ll wait for the scientific community to make its judgement, without pre-empting it.

    A critique of W-L’s 2006 paper by Hagelstein and Chaudhary was published in J. Phys. B. in 2008. It claims W-L’s electron mass shift calculation is wrong. But it goes on to consider some other systems where B-O breaks down and electron mass increase should be observed. Whether W-L or H-C are right or wrong, and whether or not there are low energy nuclear reactions, it seems to me that there is interesting new physics being explored here.

    W-L responded to H-C’s critique quite sharply, and gave a number of errors they perceive in that work. Again I’m not able to judge, but they assert their original analysis stands (and the use of the word “blunder” in a scientific paper always draws a sharp intake of breath).

    Back soon after Fleischmann and Pons made their announcement, in the midst of the initial excitement, I attended a seminar by a very distinguished quantum chemist who went through the muon catalysis mechanism that had been proposed to explain F&P’s claimed result. It was plausible, but subsequently shown to be wrong. So I’m quite aware that a plausible mechanism on paper may end up not being worth the paper it is printed on. I maintain a level of skepticism consistent with the strength of evidence that will be required to support these new LENR claims.

    But its not OK to tar everything with the brush of the early cold fusion work. Let Fleischmann and Pons rest in peace. And let any new work in this area be judged on its own merits.

  7. UK energy plans – while SEWTHA is always worth a read if you haven’t already, the energy plan sketches are a bit out of date now. Latest versions are in the ‘2050 calculator’ at

    http://2050-calculator-tool.decc.gov.uk

    Pick one of the example paths, or make your own. ‘Markal 3′ is closest to current official plans. Note the largest energy source by 2050…… No Gen IV reactors in the model though, unfortunately.

  8. This might be of some interest here … solar biofuel company, Joule Unlimited, just got a large influx of private capital, and currently claims productivity several factors higher than cellulosic ethanol. The key, which they report in a peer reviewed paper (“A new dawn for industrial photosynthesis“), are genetically engineered cyanobacteria able to operate continuously, and “achieve an overall efficiency of 7.2% in converting sunlight to liquid fuel.” Company claims it may eventually be able to produce diesel for as low as $1.19/gallon.

    If finding a low cost alternative to middle east oil is the goal (and with reported 1/2 emissions than conventional synthetic fuel production), Silicon Valley feels like it has a good approach. Using natural gas instead of water as a hydrogen source, and operating at much lower temperatures (eliminating oxygen-fired combustion), Stanford University Research Institute (SRI) has developed an experimental process for turning coal into liquid fuels. Even with the advent of cost effective electric cars and batteries, we’ll still see a need for liquid fuels to fly airplanes. SRI reports a price point of $2.82/gallon for jet fuel, and a much lower cost for conversion plant (when compared with more expensive and higher emissions Fischer-Tropsch process). Experimental scale on both fronts, but still very interesting.

  9. ERoEI is math and not the real world of processes, huge machines, massive buildings and global transportation. This essay has pictures to make the point.
    >>>>>>>>
    Solar and wind capturing devices are not alternative energy sources. They are extensions of the fossil fuel supply. There is an illusion of looking at the trees and not the forest in the “Renewable” energy world. Not seeing the systems, machineries, fossil fuel uses and environmental assaults that create the devices to capture the sun, wind and biofuels allows myopia and false claims.
    ERoEI is only a part of the the equation. Each of these processes and machines may only add a miniscule amount of energy to the final component of solar or wind devices. How else would we do it? There is always the old way. Who of us will go down in the mine first?
    A story in pictures and diagrams:
    From Machines making machines making machines

    http://sunweber.blogspot.com/2011/12/machines-making-machines-making.html

  10. Following.
    and just to say I finally got my “Plentiful Energy ” book and after just the Intro I am hooked.

    It seems odd that the Clinton Admin would have killed this program. I would have guessed the Repubs since they love big oil.

    but never the less it will all happen in due time (or maybe too late)……who knows??

  11. Of course, the wind lens reduces edge losses hugely compared to a fully open design. I doubt it’s practical for MW class turbines though, simply due to the huge rotor diameter – which means it’s not applicable to the most efficient and economical turbines (the big ones).

    The more important question is, will the wind lens make the wind blow?

    The answer is no. Wind power output is an exponential function of the wind speed. Less wind means hugely reduced output.

    So the answer is also, no you can’t power the entire USA with wind. You can however burn loads of natural gas and have some wind turbines to feel good about your monstrous greenwash.

  12. TerjeP (say tay-a) wrote:

    An interesting video on a new invention from Japan. The demonstration shown suggests that the addition of a relatively simple wind lens to conventional wind turbines can double the power output.

    This is similar to the Flodesign axial-flow turbine (video too), which exceeds the betz limit (59.3%) of conventional designs … meaning it funnels more air to the turbine blades, like a jet engine, rather than pushing air around the sides. Advantages are better deployment in urban areas, greater energy conversion (same as conventional turbine twice it’s size), closer site spacing (minimizing land use), operation in both low and high wind environments (power increasing “with the cube of the wind speed”), shorter and more stable rotors, and more. Disadvantage are that turbine has to be very closely aligned to wind direction. Flodesign has it’s roots in aerospace, is very close to commercialization, and also has significant private capital and arpa-e funding.

  13. EL,

    You’ve listed some disadvantages but missed the important ones. The disadvantage of all types of Wind generation are: it is very high cost, completely unreilable, not available when most needed (e.g. slide 12 here: http://www.ceem.unsw.edu.au/content/userDocs/Solar2011-slides.pdf ) uses far more resources than the alternative low emissions techmologies (…. you can fill it in), avoids little GHG, diverts the focus and resources from realistic solutions, damages the economy and …. you can fill it in if you want to.

  14. What these “wind lenses” do is they reduce edge losses. Edge losses are important for small wind turbines as they have much more circumference per square meter of blade area, and therefore inherently high edge losses. Unfortunately, smaller wind turbines are grossly uneconomical, they are ineffcient to start with and use too much equipment (kg/kW) so you just started an improvement on the least economical wind turbine type. This might be considered silly. You need to start with the MW class wind turbines and then make it a factor of 2-3 more productivel, that would be cool. And it looks like this isn’t feasible. Wind lenses have much less effect on larger rotor diameters simply due to the lower circumference (edge losses) per square meter of rotor area. Indeed, this is one of the main reasons why larger wind turbines are more efficient (closer to Betz limit). It’s also one of the main reasons why big steam and gas turbines end up much more efficient than smaller ones – reduced edge losses.

    Like Peter Lang says, there are many other disadvantages of wind that are actually showstoppers. For example wind turbines don’t produce most of the time and you can’t control the wind. We can’t control the sun either. We can’t power our countries with it. Energy storage? Take a look at how much you need and what this costs per capita, to truely power the country with these wind and solar energy sources. It’s huge, tonnes of batteries per capita, prohibitively expensive and not very green either. I could go on but this uncontrollability and unproductivity (and the economical consequences of prohibitive storage requirements) is already a showstopper.

  15. It would be better to promote the creation of large scale renewable energy projects in areas that are degraded by human use, such as abandoned (or even current) military land or dump sites as oppose to just “uninhabited” areas that can be important habitat for rare species: http://www.biologicaldiversity.org/programs/public_lands/deserts/mojave_desert/preserves_and_solar_power.html. In the US, for instance, there is talk about large scale solar in the extremely biodiverse Mojave Desert or in grasslands home to endangered foxes, birds and snakes. It seems a little counterproductive to destroy habitat of the life we are trying to protect with renewable energy. http://conservationofbiodiversity.wordpress.com/

  16. Pingback: Wind Power and hard facts on energy economics and ERoEI – Engineering Matters

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