hydrogen have used a process called steam reforming. This process
involves vaporizing fossil fuels and mixing them with high-pressure,
high-temperature steam. A nickel-based catalyst is introduced, and the
process yields hydrogen. It also, however, yields carbon monoxide (CO)
and CO2, the primary greenhouse gas. Additionally, the source of the
hydrogen yielded from this process is a nonrenewable form of energy.
Scientists working with this process argue that it is worthy for two
primary reasons. First, what has been learned about fossil fuels could soon
be applied to other renewable hydrocarbon fuels, such as biomass.
Second, the waste by-products, such as CO2, are more easily controlled in
a single large-scale production facility than they are coming out of auto-
mobile tailpipes. Therefore, converting car engines to run on only
Chapter 5
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Technology: Ocean Thermal Energy Conversion (OTEC)
Any scuba diver knows that there are often vast differences between the temperature of
surface waters and the temperature of waters some depth below. Imagine having the
ability to take advantage of that temperature change and produce electricity! This is what
Ocean Thermal Energy Conversion (OTEC) really does. See Figure 5-A.
The OTEC system of power generation relies on a refrigerant, such as ammonia, that
vaporizes at a temperature less than the surface water temperature. The refrigerant also
must recondense back into a liquid at a certain temperature, in accordance with the depth
waters. The gas is locked in a closed loop. Warm surface waters are used to vaporize the
refrigerant. The force of the expanding gas is used to spin a turbine coupled to a generator.
Once the energy from the expanding gas has been transferred to the turbine, the gas is
cooled back into a liquid using the temperature of the depth waters. The entire process
requires about a 40°F temperature differential and goes on continuously to provide steady
power generation. Obviously, this type of temperature differential is not available in all
waters. OTEC is being tested domestically in Hawaii.
OTEC does not provide any fossil fuel pollutants. Small generating plants can run
quietly and efficiently. They must, however, be located near land, in order to feed elec-
tricity onshore. Also, they must be tethered to the ocean floor, thereby creating a form of
environmental and visual pollution. The changes in temperature created by OTEC genera-
tors can kill nearby marine life. Lastly, these generators appear to work best for small-scale
power generation, leaving their ability to someday replace major power-producing
sources in question.