Energy From the Oceans

Energy From the Oceans

Ocean Thermal Electric Conversion

The oceans are a huge heat engine. Temperature differences, caused by differences in insolation both in latitude and in depth. More promising technology is OTEC (Ocean Thermal Energy Generation). This takes advantage of the fact that the ocean is an enormous heat engine.

This in fact is a "global solution" and represents a chance for the world to collaborate on varions infrastructure and production facilities.

Physics of Heat Engines:

Thermodynamic Constraints:

To get the highest efficiency one wants to maximize the difference between T1 and T2 but in most natural environments nature doesn't really do this.

Do this:

Basic principle is that heat difference is used to condense a steam into a liquid then return it to be reheated.

Since heat differences in the ocean will be smaller, then one must substitute ammonia for water as the working fluid.

This 50-m high, 100-m diameter concrete facility is to generate 100 MW of electric power

Example Calculations:

Possible Additional Benefits:

OTEC Potential Sites:

Above sites typically have thermal gradients higher then 22 degrees C

Energy extracted comes from the cooling of the warmer water this is transferred to the ammonia which does the actual work of turning the turbine (as ammonia steam)

Energy extracted proportional to the volume of water and the temperature it drops.

Principal energy loss is when the warmer water meets the cooler water in the condenser.

Review of OTEC (Ocean Thermal Energy Conversion)

Major currents are shaped by:

Tapping the Current for Energy:

Tidal Energy from the Ocean

Extracts energy from the kinetic energy of the earth-moon-sun system.

Variations in water level along coastlines can be used to drive turbines technology is the same as low-head hydro power

Vertical tides on US coast range from 2 feet in Florida to more than 18 feet in Maine

To enhance efficiency of turbines driven by tidal currents, it is desireable to build a damlike structure across the mouth of a tidal basin in order to direct the flow to a turbine

Turbines designed for work at both high and low tide (inflow or outflow)

Intermittent tidal flow is major problem. Tidal facility produces about 1/3 the electrical energy of a hydro facility of the same peak capacity

Two tidal plants in the world:

Proposed New Facilities:

Potential Sites in the US

Bottom Line: There aren't many favorable sites in the world for tidal power and the estimated capacity is 50 times smaller than the world's hydroelectric power capacity.