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Old 12-18-2009, 12:54 PM
cragger cragger is offline
 
Join Date: Aug 2007
Posts: 632
Default Re: How a giant battery may save the world (osmium & irw)

Good discussion. I particulaly appreciated the description of the problem as being one of grid level energy storage. The types of storage you considered - chemical energy in batteries or fuel cells and possibly storage in fields using capacitors aren't the only ways to store energy, though it's understandable you concentrated on batteries since that is what you work on.

A few initial thoughts spurred by the diavlog:

Considering the relative costs of renewable sources vs. the various fossil energy sources, the crossover point seems to be approaching. Solar costs per KWH have been coming down over time, and fuels increasing in cost, particularly for oil and gas-fired plants. These appear subject to steep cost increases in the near-term future, though it will likely be a while before coal costs go up steeply. Of course in comparing the costs per KWH one must also remember that the figures are very distorted by the externalization of considerable costs from the use of fossil fuels, costs now coming home to roost though not through market economics directly tied to the causes of those costs.

A couple of additional factors in solar's favor include creation of a distributed source system that offers advantages in resiliance and robustness over a centralized source system. As a partial solution to energy generation, solar output is well matched to the demand curve. Distributed generation, such as at the home level, also gives the advantage of generation at the point of consumption, reducing both transmission needs and transmission power losses.

A couple thoughts on storage. Though the batteries Osmium is working on are hoped to last longer than the deep discharge cells typically used in off-grid systems now (say 8-10 years rather than "several"), the installation and maintenance costs of the system of cells and attendant electronics to control charging and do power conversion still don't sound likely to be trivial. It would take a pretty steep price curve for power depending on real-time demand to motivate much installation.

This suggests that like generation, there is likely a mixed solution set for storage that will be optimum, rather than any single magic-bullet techno fix. It was suggested that a homeowner might have storage batteries next to his water heater. Since energy can be stored as heat, it is likely that a partial storage solution would be a changeover from small tank and tankless hot water systems to storing energy in a big tank of hot water. This might easily act as a store that could also be used for home heating, as well as for hot water. (Conversion of the heat to electricity may be impractical at present). An insulated storage tank requires no maintenance, lasts a very long time, and seems likely to offer lower life cycle costs per joule of storage than any likely battery system. Again, not the whole solution, but part of the overall picture. Not glamorous, just cheap and effective.

A more centralized grid level storage option that similarly requires no new technology would be to build dams with a second catchment basin, or add such catchments to existing dams. The second basin need not provide the "head" that the upper dam uses for power generation, it is simply a store of water that has gone thru the dam and powerhouse. During times when power generation exceeds demand, water is pumped from the lower catchment back up to the reservoir above the dam. When demand exceeds generation, the dam releases water through the powerhouse. Water could be recycled through the dam and powerhouse any number of times without affecting the overall river flow.
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