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By Robert Rapier on May 17, 2012 with 33 responses

The Most Important Problem in Renewable Energy — R-Squared Energy TV Ep. 22

In this week’s episode of R-Squared Energy TV, I answer a question about the artificial leaf being worked on by Daniel Nocera at MIT. I discuss the strengths and weaknesses of various storage schemes, and explain why I believe storage is the most important problem in renewable energy.

In the video I discuss the low energy density of batteries relative to liquid fuels. Below is a graphic I pulled off of the Wikipedia entry for Energy Density that illustrates this:

Readers who have specific questions can send them to ask [at] consumerenergyreport [dot] com or leave the question after this post (at the original source). Consider subscribing to our YouTube channel where you’ll be able to view past and future videos.

Link to Original Article: The Most Important Problem in Renewable Energy — R-Squared Energy TV Ep. 22

By Robert Rapier

  1. By Jerry Unruh on May 18, 2012 at 9:54 am

    If PV efficiency is 15% (this is improving), water electrolysis can get to about 10% including compression  [e.g. Norsk Hydro at plant efficiency of 73% (NREL/MP-560-36734, Sept, 2004)].  Ignoring, for the moment the problems of hydrogen storage, do you think artificial photosynthesis will beat this?  Both improving PV and electrolysis will improve this number.  I chose the Norsk unit because it uses stainless steel/nickel electrodes not platinum.  Of course this is still better than biomass efficiency but I’m ignoring economics for this question.

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    • By Robert Rapier on May 18, 2012 at 2:22 pm

      Ignoring, for the moment the problems of hydrogen storage, do you think artificial photosynthesis will beat this?

      Jerry, I don’t know. It’s just an interesting concept to me. I like what photosynthesis does in nature, and always thought (even before I heard of Daniel Nocera) that it would be interesting to somehow be able to harvest that. Whether they can do it economically is another matter.

      By the way, I wonder why they don’t do electrolysis (or this process) under pressure, avoiding compression? I assume if I did electrolysis in a closed cell the pressure would build (i.e., automatic compression). Any ideas of whether that is feasible?

      RR

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      • By Jerry Unruh on May 18, 2012 at 4:53 pm

        Robert:

         

        My understanding is that there are units that run under pressure and are approaching 90+% efficiency.  I chose the Norsk unit because they have been business more than 80 years and aren’t using Pt electrodes.  Clearly there is room for improvement in both PV (or wind) and electrolysis.  BTW the 73% efficiency includes everything; the electrolysis efficiency is about 85% (and I think is based on HHV)

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  2. By Edward Kerr on May 18, 2012 at 10:33 am

    Robert,

    If the goal of “energy storage” is to provide a fully charged and harmonized electrical grid then I ‘m a bit confused concerning the point that you are trying to make. (?)  With the advent of “molten salt CS” being able to produce base load power 24-7 (with a single caveat) and wind providing energy “whenever” and PV providing energy when stimulated I think that energy storage is a red herring.

    As to liquid fuels (and I’ve harped at you on this issue before) it’s clear to me that oil produced by algae through photosynthesis will provide all of the liquid fuels (energy dense and stored) that we need to continue powering our civilization in a manner to which it has become accustomed.

    In the search of a sane energy paradigm,

    Ed

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    • By Robert Rapier on May 18, 2012 at 2:25 pm

      I think that energy storage is a red herring.

      Energy storage has to be cost effective. There are all sorts of schemes we could envision; few of them would be practical and cost effective. We could also say “With available battery technology, energy storage is a red herring.” Sure, you could just put enormous battery banks on every wind and solar farm. But why don’t they? Cost.

      it’s clear to me that oil produced by algae through photosynthesis…

      That’s not at all clear to me. In fact, many of the algae companies are going off in search of higher margin products because they can’t make fuel cost effectively. 

      RR

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  3. By Ed on May 18, 2012 at 5:59 pm

    Please remember that a CSP system with storage (ignoring in and out and storage period losses) must collect ~4 times the energy during the collection period (~6 hours/day) that it will deliver to the load on a 24/7 basis. Therefore, while the cost of the electric output might be $”x”/MWh for “source of opportunity” power, available when it is available, the cost of 24/7 power from a CSP plant with storage would be ~$5″x”/MWh, assuming that the cost of the storage system to store approximately 75% of the daily output of the plant for an average of 9 hours per day were equal to ~25% of the installed cost of the collector system. That is not a trivial issue.

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    • By Ed on May 18, 2012 at 6:09 pm

      CLARIFICATION: The system must collect ~4 times the energy EACH HOUR during the collection period that it will deliver EACH HOUR on a 24/7 basis.

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      • By Tom G. on May 19, 2012 at 9:08 am

        Hi Ed – Good Posting

        Only have a couple of minutes before going out the door this morning.  Two minor points.  

        If the plant is designed to run 24/7 which I think is quite unwise for Concentrated Solar Power [CSP]; shouldn’t the collected excess power be approximately 3:1?  I guess that could be 4:1 depending on how you look at it.  

        From what I read many CSP plants are being designed to generate electricity only during peak periods to reduce cost.  We have lots of other evening generation capabilities.  Therefor the amount of storage needed would be somewhat limited since the power would only be needed between say 5 pm and 9 pm.  I don’t think 24/7 CSP is cost competitive yet with some of the other available sources.       

        Have a great day 

         

         

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        • By Ed Reid on May 19, 2012 at 1:25 pm

          Tom,

          Thanks. I was replying to the Edward Kerr comment above, though it didn’t post that way. I worked from his premise of CSP 24/7 making storage a red herring, though obviously CSP 24/7 relies on a lot of storage.

          I’ll grant that we don’t need CSP 24/7 today. However, the folks who advocate for all renewables all the time would do well to analyze the power cost implications of renewables as reliable, dispatchable power, rather than “source of opportunity” power. A factor of 5 multiplier makes the economics look rather daunting.

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      • By Robert Rapier on May 20, 2012 at 3:07 pm

        The system must collect ~4 times the energy EACH HOUR during the collection period that it will deliver EACH HOUR on a 24/7 basis.

        And that was the point I was trying to make. Just because solar thermal can in theory provide energy 24/7 does not mean it can do it in a cost effective manner. The round-the-clock output will be a fraction of the potential daytime output.

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  4. By Russ Finley on May 19, 2012 at 11:00 am

    Cost effective storage would also allow nuclear (and unfortunately coal as well ) to cost effectively provide peaking and load following for intermittent sources like wind and solar. Storage would compete mostly with natural gas which is now used for peaking power.

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    • By Herm on May 19, 2012 at 12:34 pm

      Thats the problem with storage.. the essentially free natural gas that is available in the US will kill any storage potential for the next decade, perhaps longer.

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    • By Robert Rapier on May 20, 2012 at 3:05 pm

      Cost effective storage would also allow nuclear (and unfortunately coal as well ) to cost effectively provide peaking and load following for intermittent sources like wind and solar.

      I meant to make that point in the video. I did mention it in my presentation at Santa Barbara. It would allow for more efficient operation of fossil fuel plants though by allowing them to run at more stable rates. 

      RR

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  5. By notKit P on May 19, 2012 at 2:48 pm

    The basic problem with renewable energy is that the people who produce power are so good at providing when an where people need it, the impractical uses of renewable energy are not needed When renewable energy is available, we make use of it very effectively. Hydroelectric is used in the US to its practical extent. Same with geothermal and biomass.

     

    As society needed more power, fossil and then nuclear were used. When we have an adequate reserve margin, we stop building power plants. So what happens to wind farms when the power is not needed. You idle them just like you do coal plants in the spring and fall when the power is not needed.

     

    The real problem with renewable energy is that it is not a better environmental choice. Renewable energy has environmental impact just like any source of power. We are required to minimize the environmental impact so that the net result is that the impact is insignificant compared to the impact our customers have on the environment. The Seattle are has a big environmental impact. Making its power does not.

     

    ‘Clean energy’ is base on the fallacy that there is ‘dirty’ energy. All the promoters of ‘clean energy’ talk about some futuristic without noticing it is already here.

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  6. By Jim Takchess on May 19, 2012 at 8:57 pm

    I’ll pose the storage question in a different quirky way. 

    Is there a business, process or a form of work that could be connected to a intermittent variable power supply like solar or wind that would be profitable using only that input ?  

    The ideal process would fit this criteria:

    * A process that had low fixed costs whose costs are mainly variable based on energy input.

    * could take advantage of all the energy provided when it was provided (little waste) 

    * would have low or no cost when not being provided with energy  

    * could be performed near the energy source with little energy  loss.

     I find this to be an interesting question. Any thoughts?

     

     

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    • By robert on May 19, 2012 at 11:17 pm

      Is there a business, process or a form of work that could be connected to a intermittent variable power supply like solar or wind that would be profitable using only that input ?  

       

      Pumping water uphill.  Let’s take the example of Little House on the Prairie with a windmill and a well.  Perhaps irrigation.  Pumping water into a holding tank need only occur when the wind blow.

      The central arizona project pumps water uphill to Tucson where we inject it into the ground in case we need it a generaton from now.  It takes like an entire coal burning plant to do this.  There isn’t much wind in Arizona and solar is still kind of expensive but it seems like something that could be done at night or whenever there is cheap time of use rates.

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    • By Robert Rapier on May 20, 2012 at 3:09 pm

      Is there a business, process or a form of work that could be connected to a intermittent variable power supply like solar or wind that would be profitable using only that input? 

      That’s an interesting way to think about it. One I have heard discussed is refrigeration. If you kept a large thermal mass at somewhat less than was required for the particular purpose, when the power isn’t producing you could just let the temperature rise somewhat. You would have to be connected to a backup power source though in case you were without the intermittent power for an extended period.

      RR

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      • By Ed Reid on May 20, 2012 at 5:21 pm

        Ice storage equipment is commercially available. http://www.calmac.com/products/icebank.asp

        It is typically used to take advantage of lower night electric rates, as well as the lower night temperatures of the condensing environment. It could certainly be used to store “coolth” produced using  intermittent power sources, especially wind. Profitability is another question.

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  7. By Jim Takchess on May 20, 2012 at 10:25 am

    It would be interesting if there was a desalinization process that could be run entirely by tidal power  or a storage system that would pump salt water into a tower then have it desalt itself while extracting energy from it. Two benefits for the price of one. 

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  8. By Optimist on May 21, 2012 at 8:58 pm

    As to liquid fuels (and I’ve harped at you on this issue before) it’s clear to me that oil produced by algae through photosynthesis will provide all of the liquid fuels (energy dense and stored) that we need to continue powering our civilization in a manner to which it has become accustomed.

     Makes no sense to go growing new biomass, when we are dumping so much of it in our landfills. Start with the landfills. The biggest single component is paper (and that’s after all that much ballyhooed recycling).

    Harvesting only the lipid fraction from algae is sure way to FAIL: the yields aren’t high enough. High density is of little use. As is demonstrated by the continuing failure of algae to take the market by storm.

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  9. By Warren Stephens on May 23, 2012 at 11:42 am

    The best storage technology that I’ve found so far that could potentially scale up is the Carnegie Mellon University spinoff company Aquion Energy. 

    They have a battery that uses only cheap materials that are available in abundance, can be made in a factory without “clean room” type of equipment, and is environmentally benign (“edible” someone wrote).

    Aquion obtained $30m of (high profile) venture capital funding and is building their first commercial scale plant now.

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  10. By mac on May 25, 2012 at 12:16 am

    Warren,

    Here is  link to a TED talk given by Jay Whitacre, one of the engineers at Aquion Energy,  a materials scientist who used to work for NASA on the Mars Rover program. 

    Very funny presentation.  Worth watching just for the chuckles.  He explains why Aquion chose the materials they did and how they got the battery to market so quickly < 4 years.

    http://www.youtube.com/watch?v=vaMuxB4s5qI

    ————————————————————————————————————

    Also, I see in today’s ‘ news that they are planning to try to bring Donald Saldoway’s MIT molten metal battery to market, also made out of relatively inexpensive materials.

    http://www.masshightech.com/stories/2012/05/21/daily41-Gates-backed-Liquid-Metal-Battery-secures-15M.html

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    • By Warren Stephens on May 25, 2012 at 1:44 pm

      Thanks for that one on Whitacre.  I hadn’t seen it.

      Also, I have to confess that I’ve seen Sadoway present his idea, but have not actually figured out how why it should work.

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  11. By mac on May 25, 2012 at 4:56 pm

    Warren,

    Here’s a link to  a TED talk that Sadoway gave.  Like Whitacre’s talk, I found it quite amusing.

    Sadoway doesn’t go in depth into the actual formulas for the electro-chemical reactions but discusses mostly how the battery was conceived, developed, etc.  If you haven’t seen it. you might get a kick out of it.

    The Sadoway video on the MIT Technology Review website is a bit hard to follow and not nearly as funny as this one where Sadowy goes to the chalkboard.

    http://www.youtube.com/watch?v=Sddb0Khx0yA

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    • By Warren Stephens on May 29, 2012 at 11:13 am

      That is a good talk. 

      Some time ago I had seen Sadoway (in person) do a serious talk.  And I, like others, tuned out after hearing that the storage runs at high temperature.  That isn’t a reason to kill the idea, but I still don’t know exactly why.

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  12. By drunyon on June 10, 2012 at 10:39 am

    RR: have you seen any details from Solar Fuel (http://www.solar-fuel.net/en/the-challenge)?  They are pushing conversion of extra electricity from Solar/Wind to hydrogen, then to methane.   Supposedly, Alpha plant in production with beta plant “Currently being planned”.  They claim 60% effieicncy.

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    • By Robert Rapier on June 10, 2012 at 3:04 pm

      RR: have you seen any details from Solar Fuel (http://www.solar-fuel.net/en/the-challenge)?

      I have seen a number of schemes like that on paper — some to produce ammonia — but don’t know that anyone has pulled it off at any sort of scale. Their biggest challenge for that route is that methane is dirt cheap and likely to remain so for a while.

      RR

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  13. By Russ Finley on June 10, 2012 at 1:04 pm

    There is always somebody looking for funding for any given energy scheme. In one place they say:

    “The attainable level of efficiency is over 60 percent.”

    In another place they say:

    “The efficiency of the SolarFuel power-to-gas method is about 60%.”

    And by that they are only referring to the conversion of hydrogen into methane. Unlike fossil fuel power plants, solar and wind typically send electricity directly into the grid without any efficiency loss (100% efficiency) at the power plant (all sources suffer line losses on the way to an outlet). This is a major factor in their economics–no fuel burn losses. If you are going to use solar and wind generated electricity to make a fuel, it would be deceptive to not account for the losses associated with turning fuel back into electricity.

    Not to mention, part of the appeal of hydrogen is that it emits no emissions (converts hydrogen and oxygen back into water). Although the promoters are careful not to say it, combustion of this source of methane creates more CO2 than was used to make it which defeats the main reason many environmentalists support solar and wind. From Wikipedia:  

    Combustion

    In the combustion of methane, several steps are involved. An early intermediate is formaldehyde (HCHO or H2CO). Oxidation of formaldehyde gives the formyl radical (HCO), which then give carbon monoxide (CO):

    CH4 + O2 → CO + H2 + H2O

    The resulting H2 oxidizes to H2O, releasing heat. This reaction occurs very quickly, usually in significantly less than a millisecond.

    2 H2 + O2 → 2 H2O

    Finally, the CO oxidizes, forming CO2 and releasing more heat. This process is generally slower than the other chemical steps, and typically requires a few to several milliseconds to occur.

    2 CO + O2 → 2 CO2

    The result of the above is the following total equation:

    CH4 + 2 O2 → CO2 + 2 H2O (ΔH = −891 kJ/mol (at standard conditions))

    This hydrogen to methane idea requires burning the fuel in an internal combustion engine of some sort. Conversion of fossil fuels into useable electricity typically throws away roughly 60-70% of the energy in the fossil fuel. Assuming they really are 60% efficient (which is unlikely) their conversion process throws away an additional 40% of of that  30-40% left after burning a fossil fuel for a total efficiency of about 18-24% compared to the original electricity efficiency of 100% I mentioned earlier.

    The only advantage of this idea is to trade the cost of storing hydrogen for the cost of converting it into methane (which can be stored in the existing natural gas infrastructure). However, whether you create and burn hydrogen or methane, the combustion process imparts a huge energy loss compared to sending electrical power straight into the grid without any conversion losses.

    Assuming cost is directly proportional to efficiency, this idea would increase the already high cost of electricity generated by wind and solar about 100-24 = 76 to 100-18 = 82 percent (neglecting the cost of building hydrogen-to-methane refineries and other complexities).

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