Why We Need Electric Cars
(Page 2 of 7)
October/November 2006
By Steve Heckeroth
Fossil fuels are inherently very inefficient because of the hundreds of millions of years of solar energy and the rare geologic events it takes to produce them. About 350,000,000 terawatt (trillion watt) hours of solar energy strike the Earth every year. It took 3.5 billion years of photosynthesis to create world oil reserves that contain about 1,000,000 terawatt hours of energy. Do the math and you will find that using direct solar radiation is about a quadrillion times more efficient than burning fossil fuels. It is long past time to transition from ancient solar energy, aka fossil fuels, to using the solar energy we receive every day.
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Biofuels, such as ethanol and biodiesel, may help us transition to cleaner vehicles, but let’s not forget that overharvesting has contributed to the decline of many civilizations over the last 10,000 years. For the last 100 years, ever-increasing amounts of soil nutrients and fossil fuels have been consumed to grow and distribute food. As the needs of an increasing population collide with the realities of diminishing soil quality and fossil fuels, growing food will trump growing fuel.
Photosynthesis by plants is a maximum of 1 percent efficient at converting solar energy into carbohydrates. The efficiency of producing biofuels from carbohydrates and then getting refined fuel to vehicles varies from 10 percent to 35 percent, depending on the process and the distance to the use. Then there’s the 10 percent to 20 percent efficiency of the internal-combustion engine and the transmission. So, the sun to wheel efficiency of biofuels is 0.01 percent to 0.07 percent.
Producing electricity from solar energy using photovoltaics (PV) is about 5 percent to 20 percent efficient, and solar-thermal electric generation can be more than 35 percent efficient. Current battery charge/discharge efficiency varies from 80 percent to 95 percent. Electric motors are more than 90 percent efficient. As a result, the sun to wheel efficiency of solar-electric power falls between 3 percent and 30 percent. This gives solar-electric vehicles an advantage 50 to 3,000 times greater than burning biofuels.
Of course, for EVs to truly have zero emissions, the electricity used to charge their batteries must be generated from renewable sources such as the sun or wind. If EVs are charged with electricity generated by nuclear or coal-fired power plants, the true costs will be passed on to future generations. Fortunately, renewables are ready and able to charge EVs and plug-in hybrids.
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