Energy from the Ocean
More promising technology is OTEC (Ocean Thermal Energy Generation).
This takes advantage of the fact that the ocean is an enormous
Physics of Heat Engines:
- efficiency = work done/energy input
- it can be shown that this is equivalent to
efficiency (in %) = 1 - T1/T2 ; T1 < T2
- So, in principle any two reservoirs with different
temperatures T1 and T2 can produce energy.
- Systems are in equilibrium when they are at the
- energy is conserved within a closed system
- it is not possible to extract heat energy from a reservoir
and perform work without transferring heat to a reservoir of
lower temperature. In other words, all thermodynamic systems
must tend towards equilibrium. Some energy goes towards
performing work and some is lost as waste heat.
To get the highest efficiency one wants to maximize the difference
between T1 and T2 but then their are material problems (containers
melt, freeze, etc)
- Coal-fired burner: T = 825K
- Cooling tower: T = 300 K
- efficiency = 1 - 300/825 = 64%
How this all works:
Exhaust steam is condensed back into liquid thereby
decreasing its total volume by a factor of 1000
Therefore the work done by the pump is down by a
factor of 1000 compared to if it had to pump steam directly
back into the system
Overall efficiency of the above is about 1/3.
a 1000 MW plant therefore requires a 3000 MW Boiler and
2000 MW are given off as waste heat
The Electronic Universe Project