About Ocean
Energy
The ocean can produce
two types of energy: thermal energy from the sun's heat, and mechanical energy from the tides and waves.
Oceans cover more
than 70% of Earth's surface, making them the world's largest solar collectors. The sun's heat warms the surface water a lot
more than the deep ocean water, and this temperature difference creates thermal energy. Just a small portion of the heat trapped
in the ocean could power the world.
Ocean thermal energy
is used for many applications, including electricity generation. There are three types of electricity conversion systems:
closed-cycle, open-cycle, and hybrid. Closed-cycle systems use the ocean's warm surface water to vaporize a working fluid,
which has a low-boiling point, such as ammonia. The vapor expands and turns a turbine. The turbine then activates a generator
to produce electricity. Open-cycle systems actually boil the seawater by operating at low pressures. This produces steam that
passes through a turbine/generator. And hybrid systems combine both closed-cycle and open-cycle systems.
Ocean mechanical
energy is quite different from ocean thermal energy. Even though the sun affects all ocean activity, tides are driven primarily
by the gravitational pull of the moon, and waves are driven primarily by the winds. As a result, tides and waves are intermittent
sources of energy, while ocean thermal energy is fairly constant. Also, unlike thermal energy, the electricity conversion
of both tidal and wave energy usually involves mechanical devices.
A barrage
(dam) is typically used to convert tidal energy into electricity by forcing the water through turbines, activating a generator.
For wave energy conversion, there are three basic systems: channel systems that funnel the waves into reservoirs; float systems
that drive hydraulic pumps; and oscillating water column systems that use the waves to compress air within a container. The
mechanical power created from these systems either directly activates a generator or transfers to a working fluid, water,
or air, which then drives a turbine/generator.
