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Renewable Baseload Energy

Posted on 27 November 2010 by dana1981

A common argument against investing in renewable energy technology is that it cannot provide baseload power - that is, the ability to provide energy at all times on all days.  This raises two questions - (i) are there renewable energy sources that can provide baseload power, and (ii) do we even need renewable baseload energy?

Does Renewable Energy Need to Provide Baseload Power?

A common myth is that because some types of renewable energy do not provide baseload power, they require an equivalent amount of backup power provided by fossil fuel plants.  However, this is simply untrue.  As wind production fluctuates, it can be supplemented if necessary by a form of baseload power which can start up or whose output can be changed in a relatively short period of time.  Hydroelectric and natural gas plants are common choices for this type of reserve power (AWEA 2008). Although a fossil fuel, combustion of natural gas emits only 45% as much carbon dioxide as combustion of coal, and hydroelectric is of course a very low-carbon energy source.

The current energy production structure consists primarily of coal and nuclear energy providing baseload power, while natural gas and hydroelectric power generally provide the variable reserves to meet peak demand. Coal is cheap, dirty, and the plant output cannot be varied easily.  It also has high initial investment cost and a long return on investment time.  Hydroelectric power is also cheap, clean, and good for both baseload and meeting peak demand, but limited by available natural sources.  Natural gas is less dirty than coal, more expensive and used for peak demand.  Nuclear power is a low-carbon power source, but with an extremely high investment cost and long return on investment time.

Renewable energy can be used to replace some higher-carbon sources of energy in the power grid and achieve a reduction in total greenhouse gas emissions from power generation, even if not used to provide baseload power.  Intermittent renewables can provide 10-20% of our electricity, with hydroelectric and other baseload renewable sources (see below) on top of that. Even if the rapid growth in wind and other intermittent renewable sources continues, it will be over a decade before storage of the intermittent sources becomes a necessity.

Renewable Baseload Energy Sources

Of course in an ideal world, renewable sources would meet all of our energy needs.  And there are several means by which renewable energy can indeed provide baseload power. 

Concentrated Solar Thermal

One of the more promising renewable energy technologies is concentrated solar thermal, which uses a system of mirrors or lenses to focus solar radiation on a collector.  This type of system can collect and store energy in pressurized steam, molten salt, phase change materials, or purified graphite.  

The first test of a large-scale thermal solar power tower plant was Solar One in the California Mojave Desert, constructed in 1981.  The project produced 10 megawatts (MW) of electricity using 1,818 mirrors, concentrating solar radiation onto a tower which used high-temperature heat transfer fluid to carry the energy to a boiler on the ground, where the steam was used to spin a series of turbines.  Water was used as an energy storage medium for Solar One.  The system was redesigned in 1995 and renamed Solar Two, which used molten salt as an energy storage medium.  In this type of system, molten salt at 290ºC is pumped from a cold storage tank through the receiver where it is heated to about 565ºC. The heated salt then moves on to the hot storage tank (Figure 1).  When power is needed from the plant, the hot salt is pumped to a generator that produces steam, which activates a turbine/generator system that creates electricity (NREL 2001).

 

Figure 1:  Solar Two Power Tower System Diagram (NREL 2001)

The Solar Two molten salt system was capable of storing enough energy to produce power three hours after the Sun had set.  By using thermal storage, power tower plants can potentially operate for 65 percent of the year without the need for a back-up fuel source. The first commercial concentrated solar thermal plant with molten salt storage - Andasol 1 - was completed in Spain in 2009.  Andasol 1 produces 50 MW of power and the molten salt storage can continue to power the plant for approximately 7.5 hours.

Abengoa Solar is building a 280 MW solar thermal plant in Arizona (the Solana Generating Station), scheduled to begin operation in 2013.  This plant will also have a molten salt system with up to 6 hours worth of storage.  The electrical utility Arizona Public Service has contracted to purchase the power from Solana station for approximately 14 cents per kilawatt-hour. 

Italian utility Enel recently unveiled "Archimede", the first concentrated solar thermal plant to use molten salts for both heat storage and heat transfer.  Molten salts can operate at higher temperatures than oils, which gives Archimede higher efficiency and power output.  With the higher temperature heat storage allowed by the direct use of salts, Archimede can extend its operating hours further than an oil-operated solar thermal plant with molten salt storage.  Archimede is a 5 MW plant with 8 hours of storage capacity.

The National Renewable Energy Laboratory provides a long list of concentrated solar thermal plants in operation, under construction, and in development, many of which have energy storage systems.  In short, solar thermal molten salt power storage is already a reality, and a growing resource.

Geothermal

Geothermal systems extract energy from water exposed to hot rock deep beneath the earth's surface, and thus do not face the intermittency problems of other renewable energy sources like wind and solar.  An expert panel concluded that geothermal sources could produce approximately 100 gigawatts (GW) of baseload power to the USA by mid-century, which is approximately 10% of current US generating capacity (MIT 2006).  The panel also concluded that a research and development investment of less than $1 billion would make geothermal energy economically viable.

The MIT-led report focuses on a technology called enhanced or engineered geothermal systems (EGS), which doesn't require ideal subsurface conditions and could theoretically work anywhere.   installing an EGS plant typically involves drilling a 10- to 12-inch-wide, three- to four-kilometer-deep hole, expanding existing fractures in the rock at the bottom of the hole by pumping down water under high pressure, and drilling a second hole into those fractures.  Water pumped down one hole courses through the gaps in the rock, heats up, and flows back to the surface through the second hole. Finally, a plant harvests the heat and circulates the cooled water back down into the cracks (MIT 2007).

Currently there are 10.7 GW of geothermal power online globally, with a 20% increase in geothermal power online capacity since 2005.  The USA leads the world in geothermal production with 3.1 GW of installed capacity from 77 power plants (GEA 2010).

Wind Compressed Air Energy Storage (CAES)

Various methods of storing wind energy have been explored, including pumped hydroelectric storage, batteries, superconducting magnets, flywheels, regenerative fuel cells, and CAES.  CAES has been identified as the most promising technology for utility-scale bulk wind energy storage due to relatively low costs, environmental impacts, and high reliability (Cavallo 2005).  CAES plants are currently operational in Huntorf, Germany (290 MW, since 1978) and Macintosh, Alabama (110 MW, since 1991).  Recently this type of system has been considered to solve the intermittency difficulties associated with wind turbines.  It is estimated that more than 80% of the U.S. territory has geology suitable for such underground storage (Gardner and Haynes 2007).

The Iowa Stored Energy Park has been proposed to store air in an underground geologic structure during time periods of low customer electric demand and high wind.  The project is hoping to store a 20 week supply of compressed air and have approximately 270 MW of generating capacity.  The project is anticipated to be operational in 2015. 

A similar system has been proposed to create a wind turbine-air compressor.  Instead of generating electricity, each wind turbine will pump air into CAES. This approach has the potential for saving money and improving overall efficiency by eliminating the intermediate and unnecessary electrical generation between the turbine and the air compressor  (Gardner and Haynes 2007).

Pumped Heat Energy Storage

Another promising energy storage technology involves pumping heat between tanks containing hot and cold insulated gravel.  Electrical power is input to the system, which compresses/expands air to approximately 500°C on the hot side and -150°C on the cold side. The air is passed through the two piles of gravel where it gives up its heat/cold to the gravel. In order to regenerate the electricity, the cycle is simply reversed.  The benefits of this type of system are that it would take up relatively little space, the round-trip efficiency is approximately 75%, and gravel is a very cheap and abundant material.

Spent Electric Vehicle (EV) Battery Storage

As plug-in hybrids and electric vehicles become more commonplace, the possibility exists to utilize the spent EV batteries for power grid storage after their automotive life, at which point they will still have significant storage capacity.  General Motors has been examining this possibility, for example.  If a sufficiently large number of former EV batteries could be hooked up to the power grid, they could provide storage capacity for intermittent renewable energy sources.

Summary

To sum up, there are several types of renewable energy which can provide baseload power.  Additionally, intermittent renewable energy can replace dirty energy sources like coal, although it currently requires a backup source such as natural gas which must be factored into the cost of intermittent sources.  It will be over a decade before we can produce sufficient intermittent renewable energy to require high levels of storage, and there are several promising energy storage technologies.  One study found that the UK power grid could accommodate approximately 10-20% of energy from intermittent renewable sources without a "significant issue" (Carbon Trust and DTI 2003).  By the time renewable energy sources begin to displace a significant part of hydrocarbon generation, there may even be new storage technologies coming into play.  The US Department of Energy has made large-scale energy storage one if its research priorities, recently awarding $24.7 million in research grants for Grid-Scale Rampable Intermittent Dispatchable Storage.

This post is the Intermediate version (written by Dana Nuccitelli [dana1981]) of the skeptic argument "Renewables can't provide baseload power". 

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Comments 401 to 425 out of 425:

  1. Actually thoughtful,
    Thanks for the information. We get a mixture of sun and clouds in the summer. From what you say it sounds like systems are being developed. We will have to see how economic they turn out to be. I have heard a lot about GSHP.
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  2. It is not "Being developed" - it is done. Here now. Ready to go. You too can save money and the environment by acting now. Failure to act puts you in the denier crowd by actions, if not by words.

    I don't mean to be inflammatory, but there is a tendency to wait for "someone" else to do this. We are witnessing government failure in the United States - people are choosing to stay ignorant, and democracies require an informed electorate.

    The only possible solution is individual action.

    The fact that you will save money and be more comfortable is gravy.
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  3. @402 actually thoughtfull

    Nonsense of the first order. Climate is not going to be saved by the well heeled indulging in micro generation. Not now, not in ten years, not in 20 years, not in 50 years and not in 100 years. Never ever. Period.

    The climate problem is an industrial problem and requires solutions on an industrial scale - and quickly. Individuals do not build GW scale power stations - but that is what is needed.

    The US deployed 140 MW of PV in the first 11 months of 2010 and over 6000 MW of new coal. Assuming a generous 20% capacity factor for PV and 80% for coal, it would take 28 years of PV deployment at this rate to equal the output of just one 1GW coal fired power station. This is the harsh reality that the purveyors of the micro generation nonsense would rather hide.

    You cannot solve the climate problem without getting rid of coal. Micro generation will NEVER get rid of coal. Maintaining otherwise is sheer fantasy - backed by no evidence whatsoever.

    You either want to tackle the climate problem or you don't ......
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  4. Nothing could illustrate the uselessness of micro generation in combating climate change more than the case of Germany. After spending an astonishing amount of money on PV, there are moves afoot to build 27 new coal fired power stations. The push is coming from the energy companies who clearly believe that is/will be a demand for electricity that all the micro generation in the world will not be able to meet:

    http://www.spiegel.de/international/germany/0,1518,472786,00.html
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  5. An interesting aside on this topic:

    Israel has endorsed a plan for a network of electric cars, built by Renault-Nissan and using swappable battery packs for 5-minute charge changes. They plan a network of "switching stations", estimating a cost of $150M or so to build a network capable of covering the country.

    Plans by the network provider Better Place are to expand to Denmark (aiming for 100,000 cars there), and then to a (ahem) small island network - i.e. Australia, with a network covering the entire southern coast.

    Given some of the concerns on renewable baseline power, if a network of switching stations with packs of car-sized cells on chargers is available, that could provide a potential buffer for short-term demand variations. There would have to be a compensation mechanism (subtracting drawn power from charged power on the bills, at the least?), but that would represent quite an accumulation of energy.
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  6. @quokka: "The US deployed 140 MW of PV in the first 11 months of 2010 and over 6000 MW of new coal. Assuming a generous 20% capacity factor for PV and 80% for coal, it would take 28 years of PV deployment at this rate to equal the output of just one 1GW coal fired power station. This is the harsh reality that the purveyors of the micro generation nonsense would rather hide."

    Another illogical fallacy: the 140 MW of PV were not, AFAIK, microgeneration sites. Even then, you can't use the timid move towards PV as evidence that microgeneration can't help in the fight against emmissions. It's the same thing as faulting antibiotics for curing a disease when the doctor gives you only 1/20th of the required dose.

    Another mistake which you continue to make (willfully?) is that microgeneration advocates believe it is *the* solution. In fact, we believe that a mix of technologies - including nuclear - will be necessary. Again, your absolutist stance is highly suspect.

    This isn't even about opinion, it's about simple logic. You should make sure your arguments are logically consistent, otherwise you just sound like you're making a sales pitch.
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  7. 406 archiesteel

    I would remind you that I am NOT the one posting here who has a financial interest in making a sales pitch. "absolutist" assertions that

    The only possible solution is individual action.
    The fact that you will save money and be more comfortable is gravy.


    can reasonably be interpreted in only one way - micro generation. The assertion is nonsense, not based on evidence and intellectually indefensible. Let me repeat, I am NOT the one making a sales pitch here and I am NOT ascribing to others positions that they do not hold - read what was posted before making accusations.

    The whole "argument" about a mix of generation technologies is facile. There has been a mix in the past, there is currently a mix and without a shadow of a doubt there will be a mix in the future. As always, the devil is in the detail and the composition of the mix is the crunch point - it much be reliable from an engineering point of view and it must not be too expensive, otherwise it will never happen.

    Joe Romm is one who pushes this mix of technologies argument ad infinitum and states that nuclear will be part of his mix. But when a republican senator proposes 100 new nuclear power plants for the US Romm launches a broadside by reproducing a piece blathering on about jobs, college places and most astonishingly cost when the cost of other low emissions technologies would almost certainly be higher. Not once are CO2 emissions and the fact that the proposal, if realized, would make another 20% of US generation capacity very low emission mentioned. Those nukes would displace baseload coal and reduce US emissions from electricity generation by 30% or more. Such a proposal should be wholeheartedly supported.

    It is not I who is being "illogical".
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  8. @quokka: why are you talking about Joe Romm? I didn't.

    Now, if you are claiming I believe "The only possible solution is individual action", then you are using a strawman argument. I certainly do *not* think that the only possible solution is individual (considering that many see me as a Socialist, that'd be suprising).

    I do think that our Energy problem is so severe we must both act individually *and* through our governments for large-scale projects. The economy will profit either way.

    "when the cost of other low emissions technologies would almost certainly be higher."

    That is opinion, not fact, and it clearly ignores any participation of microgeneration in the mix.

    "Such a proposal should be wholeheartedly supported."

    Right. That's a pipe dream, and you know it - it would take considerable effort to deal with the NIMBY effect for so many stations.

    Again, it will be easier to sell nuclear along with renewables than instead of them.

    "It is not I who is being "illogical"."

    A strawman argument is a logical fallacy. You can deduce the rest.
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  9. @408 archiesteel

    My "opinion" that nuclear is cheaper than renewables is supported by the most recent estimates of the LCOE of the various generation technologies by IEA and EIA which I provided references to earlier in this thread. It is also supported by this The arithmetic adds up to nuclear metastudy surveying the authoritative literature.

    Micro generation will NOT reduce the cost of the "mix". The experience of feed in tariffs for PV should make that abundantly obvious. But if you think otherwise please present some evidence.

    Nuclear is the only economically viable replacement for coal in baseload generation. As Hansen and others have repeatedly pointed out getting rid of coal is the highest priority in emissions reduction. It we do not push for the elimination of coal and push hard, then we might as well give up on the notion of a safe climate. Cut the waffle about "mixes" and cut to the chase.
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  10. Here is an interesting idea for getting rid of coal - Coal2Nuclear.

    Briefly put, the idea is to retain the turbines, switch yards etc of existing coal plants and replace the coal boilers with small modular reactors. I don't know how feasible the idea is and it depends on the commercial availability of small modular reactors which are 7 - 10 years off. Nevertheless it certainly presents an interesting possibility for very economically giving coal the flick.

    It is just a thought, and I do not present it as a solution at this time as is commonly done for technologies such as enhanced geothermal which in reality is at least as far, and very possibly further away as a commercial proposition.
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    Moderator Response: [Daniel Bailey] Fixed link
  11. quokka - That's a very interesting link (if off-topic for here). Do you know if any of the micro-reactor designs now in the US/European planning stages are set for high temps like those Russian designs?
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  12. @quokka: well, I guess we'll just have to agree to disagree. I do believe the cost of nuclear is higher than the studies suggest, and I do believe you are too quick to dismiss the effect (and popularity) of microgeneration. Simply put, the more people reduce their energy consumption through microgeneration, the less power will be required of the grid at large.

    Furthermore, as long as you continue trumpeting nuclear as the only solution, you will turn people off of it. In other words, your advocacy is actually having a negative effect.

    You are also ignoring the political aspect, i.e. the strength of the NIMBY effect, and the geopolitical puzzle linked to nuclear energy (security and strategic issues, etc.).

    The fact that you can't admit a single weakness of nuclear energy is highly suspicious, in my view, but I'll refrain from saying what I really think so that my comment doesn't get deleted.
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  13. Also, microgeneration does have a significant advantage over large-scale power plants: since the energy is generated at the point where it is used, there is no loss of power during transmission. Up to 8% of electricity is wasted due to transmission over long distances.

    Another advantage is that you can still have power even when power grid fails. Decentralization also means less stress on the grid, and reduces maintenance costs.

    Is microgeneration the answer? No, it isn't, not by itself. As I said, a varied ecosystem of energy sources is the best option, even though it does mean less money for Westinghouse...
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  14. As far as cost is concerned, I wonder if they include the fact that mass production of solar and wind microgenerators would continue to lower costs overtime, making it more competitive.

    Personally, I like the idea of renewables as part of third world development strategy. Africa has enormous solar potential (mostly in the form of concentrated solar), and the technology is easier to master for what sadly remain regions with limited technical/technological education.

    In this context microgeneration plays a part, especially for tribal population who do not use much (but would like some) electrical power.

    As I said, there is no single solution. I wish we would at least agree on that, as I've already spent too much time arguing about this. After all, that time used a significant amount of that precious electricity (I don't type with the monitor off, for example).

    So in the spirit of conservation I'll say no more about this, and will leave you with the last word. I know my case is strong enough to challenge yours and keep the debate open for others, and that's fine with me.
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  15. I would think that microgeneration would be the ultimate goal of energy production. If you could get all your energy needs cost effectively from a generation unit in your home, why would you NOT want that? It may not be economically feasible now but that does not mean it won't be in the future. Maybe in the not-so-distant future.

    If the cost of PV continues to fall and battery technology continues to improve and also fall in price... what's to prevent microgeneration from being a reality? It just doesn't seem that far fetched to me.
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  16. Quokka,
    You are chery picking your renewable energy numbers. According to Wikipedia, in 2009 there was over 9,000 MW of wind installed, more than coal. As the technology ramps up there will be even more installed. Why do you pick an energy source that is not very developed to compare to? This type of cherry picking weakens your whole argument. How should I know when to believe what you post? Since no pilot modular reactors have been built yet (are there plans for one to be built?), it is very unlikely that they would be ready in less than 15 years and more likely 20 or more. They will have to build a pilot plant, run it for several years to test it and then build the real plants. It currently takes 10 years to build a nuclear plant on existing designs. Your 7-10 year projection is not realistic- more propaganda. They will be lucky to have the pilot plant built in 10 years. And who wants the waste in their backyard? Nuclear will probably be part of the solution, but propaganda does not advance the argument here.
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  17. Quokka - You have, again, failed to read and/or comprehend my post. I am speaking of solving heating and cooling issues - not microgeneration of electricity.

    This is the verboten 40% of energy use which no one is willing to speak of. We have the technology, now, to make virtually any/every building a net zero or net positive building.

    Delaying action locally in the vain hope of an organized centralized response seems at best silly, and it is possibly criminal (how will future generations judge us?)

    This doesn't mean I am against nuclear or centralized PV/CSP/wind/wave. Rather, all the above, as much and as fast as possible.

    But you are missing the powerful behavior change that local control over energy provides. When people control the means of (energy) production - they modify their behavior to maximize overall system performance.

    We find, again and again, that what is missing from the energy markets is information. Information about the true cost of carbon, real-time, actionable information about energy usage, and a sense of control over production.

    Solving one or more of the information deficits will take us much further down the road to a systemic solution than a nuke plant here or there.

    In my view, we need a systemic solution, not a different brand of band-aids.
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  18. Actually thoughtful,
    I looked more at ground source heat pumps at your suggestion. I had thought that a buried heat exchanger was the most expensive part of the system. It turns out in my area people use wells for water supply. I already have two wells on my property! I will be costing out the system to see if I can afford to change before next summer.
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  19. Michael - fantastic. It occurs to me that you are concentrating the value you get from your well - which is a good thing. Unless the well goes dry - in which case you wake up with no water and no heat/cool.

    Actually, I think you will still get heat/cool, even from a dry well (better performance with the water of course).
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  20. Actually thoughtful,
    You pump the water out one well, use the heat/cool and then pump the water down the other well. Since it is a siphon energy use is minimal. There is no net use of water for heat/cool. I get the impression this type of heat pump in only useful where there is a lot of water (like here in Florida).
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  21. Interesting article here from Scientific American on wind farms and fish schools.

    Gist of the article (at least the part interesting to me) is that by studying fish schooling (optimized for minimum energy in moving from place to place) and taking that analysis to wind farms (vertical turbines, closer spacing, aiming to provide maximum energy extraction) can result in a 10x higher energy density for wind farms. That's 1/10 the land use for the same energy provided.
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  22. Here's the high-density windmill paper - Whittlesey et al 2010, free access to an earlier version at Dalribi on Arxiv.

    Counter-rotating vertical axis turbines arranged to take advantage of upwind turbine wakes increase area power density by an order of magnitude over horizontal axis (propeller style) windmills.
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  23. An interesting article on use of microgeneration in developing countries:

    African Huts Far From the Grid Glow With Renewable Power
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  24. Solid state batteries with 2-3x the energy per weight, 10's of thousands of charging cycles, 1/3 the cost. http://www.economist.com/node/18007516?story_id=18007516&fsrc=rss
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  25. Very interesting and definitely worth keeping an eye on.

    University of Central Florida Researchers Confirm Battery Breakthrough Developed By Planar Energy
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