Question

Alternative energy sources that are renewable and that can reduce greenhouse gas emissions are actively being developed. In this example, you wish to explore the feasibility of two alternative energy sources to petroleum. The U.S. petroleum consumption is approximately 3 million m³ per day. You may assume that the fuel value of petroleum can be represented by octane. The density of octane is 0.70 g/cm³. Take the average power density for solar radiation over a 24-hour period to be 200 W/m².

(a) Assuming a solar cell efficiency of 10%, how much area would be needed to provide the equivalent energy to that used by petroleum in the United States?

(b) Bioethanol provides another possible alternative energy source. It is a biofuel that can be generated biologically through fermentation of corn. The energy efficiency of photosynthesis, defined as the energy content of the biomass that can be harvested divided by the average energy of solar radiation impinging on the same area, is typically between 0.1 and 1% for crop plants (it goes up to around 3% for microalgae grown in bioreactors). How does the crop area needed for corn compare to the area calculated in part (a)?

Answer 1

applying energy balance and calculating flux for one day we can find the required area for given efficiencies

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