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Thursday, February 15, 2018

Combinations of renewable energy projects - better together

It seems odd that renewable energy technologies are rarely if ever combined.

For instance
Another option for synergy of these two projects is perhaps less obvious but potentially far better. Concentrated solar thermal energy can be used to turn the straw into synthesis gas. This saves about 30 percent of the energy in the straw that is 'wasted' if the straw is burned without first being converted to gas.

Co-production of syngas and potassium-based fertilizer by solar-driven thermochemical conversion of crop residues


We report on the thermochemical conversion of inedible crop residues using concentrated solar energy as the source of high-temperature process heat. ... The waste biomass feedstock consisted of unprocessed batches of cotton boll, soybean husk, and black mustard husk and straw, which were pyrolysed and steam-based gasified at nominal temperatures in the range 879–1266 °C, yielding high-quality syngas ... The heating value of the feedstock was solar-upgraded by 7%, thus outperforming autothermal gasification that typically downgrades by at least 15%. 

The ash contained 23% potassium. 

The solar-driven thermochemical process offers a sustainable and efficient path for the conversion of agricultural wastes into valuable fuels and soil fertilizers.

The synthesis gas produced:
  1. Avoids the cost of the thermal energy storage needed by the concentrated solar thermal power station. This is because the solar thermal energy is stored in the form of synthesis gas.
  2. Allows the energy in both the straw and the concentrated solar thermal energy to be used for a gas-fueled internal combustion engine or combined cycle gas turbine electricty generation. This raises the conversion efficiency to 60 percent - far above the efficiency that either power plant can achieve now (assuming they both plan to use steam turbine generators at efficiencies between 20 percent and 40 percent.)