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Solar Thermal Depolymerization

Use Concentrated Solar Thermal power to help make fuel
  [vote for,

Thermal depolymerization is a process which turns solid biomass into liquid fuels, using heat and pressure.

The process is often quoted as being 85% efficient, since some of the liquid fuels produced must be burnt to produce the heat needed to sustain the process.

This idea is fairly simple: supply all of the heat using concentrated solar power, thus allowing all or nearly all of the chemical energy of the feedstock to become chemical energy in the produced liquid fuel.

In a way, this is very similar to the well known process of using concentrated solar energy for biomass gasification, except that my idea will produce a liquid instead of a gas.

Unlike gasification, which works best with dry feedstock, thermal depolymerization can work well with wet feedstock, including manure, sewer sludge, algae, or offal from meat processing plants, without needing to dry it.

Dry hydrocarbons (biomass, plastics, rubber, other garbage) can also be turned into liquid fuels by this process, though of course a certain amount of water must be added.

goldbb, Apr 03 2011

Anything Into Oil http://discovermaga...eatoil/article_view
[goldbb, Apr 03 2011]

Crosby, Solar Tar Stills... Solar_20Tar_20Stills
... and gNashing of teeth [4whom, Apr 04 2011]


       4whom, the idea you linked to is basically solar thermal gasification, which, as I mentioned, is widely known to exist. People were patenting ideas for it before I was born.   

       Solar thermal depolymerization is, as far as I can determine, an entirely new concept. I could probably patent it if I had enough money, enough knowledge of patents, and sufficient expectation of earning that money back. And if I hadn't given the idea away here ;)   

       Gasification (whether solar thermal, or powered by the generated fuel) turns a dry solid hydrocarbon feedstock into a gaseous hydrocarbon fuel. In order to use gasification to generate a liquid hydrocarbon fuel, one must first turn the solid feedstock into a gas, then (using the Fischer Tropsch process) turn that gas into a liquid. If the feedstock is contains liquid water in it, the first step of gasification is to dry the feedstock, which requires thermal energy, and unless that thermal energy is being supplied by the sun, requires that we burn a portion of our generated fuel for the drying of the feedstock.   

       Thermal depolymerization turns the feedstock (which can and perhaps *should* be wet) directly into a liquid hydrocarbon without ever turning it into a gas.   

       Gasification uses pressures close to atmospheric, and temperatures above 700C.   

       Thermal depolymerization occurs in two stages; the first stage (where depolymerization turns the solid feedstock into tars) uses a pressure of about 600 psi (4 MPa) and a temperature of about 250C, and the second stage (where hydrolysis cracks those tars into shorter, more usable hydrocarbons) uses a temperature of about 500C.   

       The temperatures required for depolymerization are much lower than those required for gasification, thus it should be just as easy to use concentrated solar power to supply the heat for depolymerization as it is use solar power to supply the heat for gasification; however, my searches of the web does not show anyone doing so.
goldbb, Apr 06 2011

       //my searches of the web does not show anyone doing so//   

       Possibly it is easier to use some of your biofuel, which is already quite green, to heat the biomass.   

       Or maybe instead of having an array of solar reflectors, you can just let the land grow full of weeds and periodically cut it down for fuel. An acre of farmland is much cheaper than an acre of solar panels.
Bad Jim, Apr 06 2011

       Can it be that easy? There must be a catch or anyone with agricultural waste could make oil. Why would they waste their time with all the ethanol fussiness if they could go straight to oil with this scheme?
bungston, Apr 06 2011

       Bad Jim, yes of course you can use some of the biofuel for process heat, but it results in only about 85% of the energy of the initial biomass ending up in the resulting fuel. By using solar thermal energy, we can hope convert 100% of the feedstock's energy into fuel energy. If the feedstock cost money to grow and harvest, then it's better to not waste it, when sunlight can do the job for free.   

       Bungston, people are wasting time and energy producing ethanol from corn, in spite of it the ethanol produced containing no more than 1.6 units of energy for each unit of energy put into it's production... and that's being generous, due to a combination of hype, enthusiasm, and government subsidies.   

       Assuming an 85% conversion efficiency, and ignoring the energy costs of producing the feedstock, thermal depolymerization can produce 5.67 times as much energy than the process consumes.   

       I would guess that the subsidies aren't as high, or the process is newer (than either ethanol or gasification) and less well known.
goldbb, Apr 07 2011


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