Latest Buzz...
                  

Translate

Monday, February 16, 2015

A spoonful of sunshine makes the demand for coal go down

The University of Minnesota Solar Energy Laboratory develops technology using concentrated solar radiation for fuel and chemical production. It provided the inspiration for this article.


"In traditional biomass gasification, 20 to 30 percent of the biomass feedstock is burned to produce heat for the process. But if the required thermal energy is supplied from a concentrated solar source, all of the biomass can be converted into useful synthesis gas." (Read more...)

Burning any carbon-containing hydrocarbon or carbohydrate fuel - whether it is biomass or coal - uses some energy to break the chemical bonds that bind the atoms together in the molecules of the fuel and then releases some energy when those atoms combine with oxygen to produce carbon dioxide and water vapour.

Solar gasification of biomass: design and characterization of a molten salt gasification reactor

by Hathaway, Brandon Jay (2013)
A former doctoral student, Brandon Hathaway is now the lead research scientist at the University of Minnesota Solar Energy Laboratory.
"The reactor developed in this work allows for 3 kWth operation with an average aperture flux of 1530 suns at salt temperatures of 1200 K with pneumatic injection of ground or powdered dry biomass feedstocks directly into the salt melt." (Read more...)
Link to Dr Hathaway on Twitter

Here is a diagram that represents the energy used and released by burning brown coal mined in the Gippsland Basin coal fields  of Victoria, Australia:

Burning hydrocarbons and carbohydrates - energy used and released

What the diagram represents is that 1 kilogram (2.2 lbs) of brown coal is decomposed into carbon monoxide and hydrogen by absorbing 5.54 megajoules of heat energy. 

The resulting carbon monoxide and hydrogen then releases 14.14 megajoules of heat energy when it combines with oxygen to produce carbon dioxide and water vapour.

The net heat energy available from burning this kilogram of brown coal is the difference between these two energy flows: 14.14 - 5.54 = 8.60 megajoules of heat energy.

Burning a kilogram of brown coal in a coal-fired power station allows a proportion of this 8.60 megajoules of heat energy to be converted to electricity.  Typically only about 40 percent is delivered as electricity: around 0.96 kilowatt-hours.

A different way of converting brown coal to electricity enables a far greater amount of electricity to be produced from each kilogram:
  • First each kilogram of brown coal is decomposed into carbon monoxide and hydrogen by absorbing 5.54 megajoules of concentrated solar thermal energy.  
  • Second, the resulting carbon monoxide and hydrogen releases 14.14 megajoules of heat energy when it combines with oxygen to produce carbon dioxide and water vapour in a gas power plant. Typically about 60 percent is delivered as electricity: around 2.36 kilowatt-hours.

The coal needed to produce 0.96 kilowatt-hours of electricity is reduced from 1 kilogram (2.2 lbs) to just 405 grams (14.3 ozs).

1 comments:

Mike Dill said...

If the residual heated water could be used then the efficiency could be even higher. This works when used as a community project to heat buildings and even swimming pools