The difficult parts of the emerging renewable energy economy are the high-efficiency biomass converters and new energy storage. (The biomass-to-electricity converter is a sine qua non for the Sustainability scheme.) These are essential; without high efficiency the energy yield of biomass is too low to support a high standard of living, and without storage the use of intermittent supplies (such as wind and solar) becomes problematic.
At least, they looked difficult. Turns out one might be on the way as a solution for other problems, and a big chunk of the other is already available for free.
Storage first. Nature magazine reports an experiment in the Netherlands which will use cold-storage warehouses as massive demand-managed systems to balance the variability of wind power and the daily demand curve. (More commentary here, and a short project description here). During periods of power surplus, the warehouses' refrigeration systems will be run full-bore to chill them by up to 1°C; when power production lags demand, the warehouses will shut off their chillers and coast on their stored heat-absorption capabity. The possibilities are claimed to be huge:
The net effect would be that the warehouses would act as as batteries — potentially storing 50,000 megawatt-hours of energy — and the food wouldn't melt.
Electricity is expensive to store, but many of the things we make from electricity are not. I've been touting the possibilities of ice-storage systems for A/C for some time. Here's an example of DSM which is already available for free — and even has the control systems built in to handle shorter (6 minute) interruptions for the sake of peak-demand management.
This example is a clue-by-four to use on denialists. They've been saying it can't be done, so now we can point to this and say "Holland is doing it, you ignoramus." (As far as I'm concerned, anyone denying a confirmable fact gets one free pass along with a hotlink to the information which proves them wrong. After that, they're fair game for any epithet you like.) Once the warehouse systems are out there, we can extend the concept as necessary to leverage the variable energy resources. The population of the Netherlands is about 16.5 million. The US has about 18 times as many people, and likely about 18 times as much refrigerated warehouse capacity. If Holland has 50 GWH of energy-banking capability available, the US might already have on the order of 900 GWH. That's about 2 hours of average US electric consumption. We'd have to build out one huge amount of wind and solar power capacity to strain that.
Being able to store renewable energy is no good if you can't make it. So I was very happy to receive a note from a reader telling me about the Gas Institute's solid-oxide fuel cell powered by gasified chicken litter. The power density of the SOFC was reduced to about 40% of normal due to the low-BTU fuel gas, but it did not accumulate any damaging deposits such as carbon. The SOFC's going to DOE for testing recently were priced in the $250-$300/kW range; if the same cells were used for converting gasified biomass and nothing can be done to raise the power level again (such as pressurizing the system), the SOFC portion's cost would increase to $625-$750/kW. This figure seems quite reasonable. After adding fuel preparation and a microturbine to provide forced-air feed and bottoming-cycle energy recovery (and assuming no increase in power density from pressurization), I guesstimate that the system might cost in the neighborhood of $1000/kW This is about the per-kW cost of a Capstone microturbine.
Dr. Lau and company appear to have used chicken litter because it is a disposal problem in some areas. What other energy-rich materials are a disposal problem? Excess rice straw? Check. Excess corn stover? If you don't have livestock to feed, check. Forestry waste? Check. Municipal green waste? Check. Plastic waste, waste cooking grease, etc? The list goes on and on.
Nobody's sent me a note about a crop waste-powered SOFC being used to generate the CO2 for an algae growth system to make liquid bio-fuels, but at the rate my speculations have been popping up in the news, it wouldn't surprise me if it happens any day now. It really does move too fast to keep up.
We look to be on-track for a Viridian green future, too late for comfort but sooner than anyone expects.
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