ALGAE (CONT)

The limited range of hydrogen powered vehicles makes them comparable to electric vehicles. The energy balance, however, is completely different. While a hydrogen vehicle would use electricity to electrolyze water to get hydrogen for fuel, an electric vehicle uses electricity to charge batteries. Battery charging systems are around 90% efficient, compared to the 60% efficiency for electrolysis. Using the charged batteries to propel a car has an efficiency in the upper 90% range, giving electric cars an overall energy efficiency of around 85%, or 0.85:1. The energy balance of electric vehicles is more than twice as efficient as a car powered with hydrogen produced through electrolysis.

Now let us consider biodiesel. Based on a report by the US DOE and USDA entitled "Life Cycle Inventory of Biodiesel and Petroleum Diesel for Use in an Urban Bus"5, biodiesel produced from soy has an energy balance of 3.2:1. That means that for each unit of energy put into growing the soybeans and turning the soy oil into biodiesel, we get back 3.2 units of energy in the form of biodiesel. That works out to an energy efficiency of 320%. The reason for the energy efficiency being greater than 100% is that the growing soybeans turn energy from the sun into chemical energy (oil). Current generation diesel engines are 43% efficient (HCCI diesel engines under development, and heavy duty diesel engines have higher efficiencies, but for the moment we'll just use current car-sized diesel engine technology). That brings the overall energy balance down to 1.38:1, roughly three times better than the 0.36:1 of the hydrogen fuel cell car. This figure means that for each unit of energy that goes into growing the crops and producing the biodiesel, 1.38 units of energy are available to be used for moving the vehicle, a net gain of 38%, compared to a net loss of 64% for hydrogen. With the improved energy balances of other crops such as mustard and algae compared to the 3.2:1 of soy, this energy balance would be even better.

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