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Roger K. Brown
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Much better to be able to make H2 for transportation fuel from excess wind to avoid having to dump excess wind for next to nothing, then costing money to pay for imported oil. Electrolyzers are fairly expensive pieces of equipment. Wind capacity factors are in the range of 30 to 40%. Using only the excess wind capacity that does not fit into current grid demand would lead to very low capacity factors for the electrolyzers. I think that this scenario for electrolzyer use is unlikely.
Given the long dwell time of CO2 in the atmosphere we need to leave substantial amounts of fossil carbon in place (or practice effective long term CCS) if we want to mitigate global warming. Without an economic way of extracting CO2 from the atmosphere it is not clear whether or not this technology will do good or harm in this respect. I am not advocating against the development of this technology. I am simply questioning the easy optimism of many commenters that it represents a potential solution to the serious problems currently being faced by industrial civilization.
In order for this process to be carbon neutral it has to use CO2 from the atmosphere rather than CO2 obtained from fossil fuel plants or from cement processing. So in addition to improving the economics of the synthesis process, the economics of atmospheric CO2 extraction must also be improved. The second requirement may prove far more difficult than the first.
While one could argue that the char and gas produced and consumed within the shale conversion process has zero opportunity cost—i.e., that energy would not, or could not, be used somewhere else in the economy, so it should not be treated as a “cost”—the authors note, “the internal energy is absolutely necessary to accurately assess greenhouse gas emissions”. This statement typifies the kind pseudo-intellectual nonsense which surrounds the use of EROI as an economic parameter. If you want to characterize the greenhouse gas intensity of oil shale production then you should directly calculate this intensity rather than kluging up some energy ratio whose relationship to the relevant physical parameter is not clear. However, the use of EROI lends an air intellectual profundity to discussions of "biophysical economics" so that people insist on using it whether or not it is appropriate to the particular issue at hand. Although energy balance is obviously relevant to the economics of energy production EROI is not in and of itself an economic parameter. It is easy to invent an example where a process with an EROI of 1.5 economically outperforms a process with an EROI of 20. If you examine assumptions of such an example (or any example of energy production when properly considered) you will see that economics are determined by the total resource cost of producing a given quantity of net energy. All of non-energy related costs such labor, fresh water, land use, etc. must be considered. These non-energy costs are not secondary factors. There exists no limit in which they can be neglected. If one makes the assumption that the non-energy related resource cost scales with the input energy with universal constant of proportionality, then you can show that EROI-1 (which I call NEROI, since it is the ratio of net energy output to input energy) can by used as a proxy for the resource efficiency of energy production. The use of EROI rather than NEROI shows that the people who do net energy analysis have not thought carefully enough about the problem to even get the arithmetic correct. Furthermore the assumption of a universal constant of proportionality between input energy and total resource cost is undoubtedly not correct. Of course translating physcial resource costs (labor, fresh water, land use, etc) into a bottom line economic cost which allows comparsion between different energy producing processes involves you in the full complexity of how value is assigned to various resources in an overall economic system with many subtle interconnnections and interdependencies. This necessity is very distressing to people who have fallen in love with the idea of doing economic analysis by calculating dimensionless energy ratios, and so they insist on hanging on to the chimaerical simplicity offered by EROI.
It is not clear that GE is using the same nickel chloride chemistry as the Zebra battery. This technical brief (http://event08.ise-online.org/site/files/ise080203.pdf) suggests that they have been exploring a zinc chloride chemistry.
Like Dave Mart I am very skeptical about the economics of using electroyzers to produce chemical fuel. If you want to use wind energy for chemical fuel then most efficient use of electroyzers would be to give them first pickings from the power output so that they could run at a higher capacity factor than the wind turbines themselves. This choice would increase the difficulty of integrating the rest of the wind power rather than decrease it. Some other means of storage would be required. Low to intermediate temperature thermal storage (for space heating, hot water, etc.) using heat pumps is one possibility. Storing electricity, however, is expensive. One new storage possibility that I read about recently (http://www.launchpnt.com/portfolio/grid-scale-electricity-storage.html) is diurnal storage in elevated weights. The proposal is to create a long undergound tube that is half filled with a block of concrete. In the state of maxium storage the concrete block is in the upper half of the tube, and in the depleted state the block is at the bottom of the tube. The block would be raised by running hydropower turbines in reverse and the energy would be extracted by the block pushing water through the turbines in the forward direction. This scheme is a form of underground pumped hydro which requires a lot less water. The proposal is to have a tube of depth between 500 meters and 2000 meters. At 2000 meters with an efficiency of 80% (I am just making up a number) the energy stored per kg would be 0.8*9.9*1000/3600=2.2Wh/kg. Over 5000 cycles (=14 years at one cycle per day) the total storage would be 11kWh/kg. If the system could be put in place for $1/Kg the cost would be $0.09/kWh plus interest. Concrete itself cost only $0.06/kg. I suspect that excavation costs will make or break this idea. Digging a 2km deep shaft will cost some bucks.
"This sounds odd: a Li-ion battery is still much more expensive than a lead acid one, and most of the time, stationary applications don't care about weight or volume, so why would they want to use Li-ion?" Deep cycle lead acid batteries have relatively low up front capital costs but their life time (i.e. the number of charge/discharge cycle that they undergo without significant degradation) is relatively low. This is why sodium sulfur batteries are the current preferred choice for utility scale storage. Apparently Pike Research is claiming that the life cycle cost of lithium batteries will drop below those of NAS batteries. Remember that stationary batteries for grid storage do not have the same severe requirements concerning energy and power density that transport batteries do. Lowering costs may be easier for this application than for automotive applications. "Plus, their lifespan is much shorter than that of a Flywheel, and this lifespan gets shortened every time you need a lot of power or charge too quickly, which isn't the case for Flywheels. Someone has an explanation?" The only company I know of with substantial commercial sales of high rpm composite flywheels is Pentadyne. If you read the spec sheets for their product you will see that the bearing losses consume the entire stored power in a little over one hour. More than an order of magnitude improvement is needed before flywheels can be used for night/day load shifting. I have read some speculation that superconducting bearings might be able to lower losses by an order of magnitude or more, but I am not holding my breath waiting for a low cost product of this nature to enter the market.