The Lowest Cost Renewable Energy Comes With a 2000 Percent Environmental Dividend
- January 29, 2015
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NASA and NOAA have proclaimed 2014 the warmest year ever recorded. It was the year also in which scientists identified heat movement into the ocean depths as the reason an atmospheric warming hiatus has existed for the previous 15 years.
Just as climate change is anthropogenic, the conditions that brought about the hiatus can be replicated with human effort using heat pipes that utilize the phase changes of working fluids to move surface heat to deep water.
The 2nd law of thermodynamics states that when heat is moved from a warmer to cooler region, through a heat engine, work is produced.
Researchers from the University of Hawaii have estimated that the oceans have the potential to produce 14 terawatts of energy this way – more than is derived from all of the world’s fossil fuels – with ocean thermal energy conversion or OTEC.
The efficiency of this process is determined by the difference in absolute temperatures between the warm and cooler heat sink in accordance with the formula
where: n is thermodynamic efficiency
W is work derived from the system
QH is heat input
TC is temperature of the cold sink, and
TH is temperature of the hot source.
OTEC systems typically operate where surface temperatures are at least 20oC above the 4oC found almost universally in the oceans at a depth of 1000 meters.
Solving for these values the theoretical efficiency of the system would therefore be 1-277/297 or about 7 percent.
Realistically this value would not be achieved, but assuming 5 percent was a possibility, 20 times more heat would have to be moved to the depths than energy produced.
At first blush this seems like a problem but factoring in the recent finding that heat movement into the depths means a slower increase in atmospheric warming, it is the reverse, In fact for every kilowatt of energy you produce with such a system you are rewarded with a 20 kilowatt (2000 percent) environmental heat dividend.
Scaling this to 14 terawatts of energy production with 280 kilowatts of heat movement to the ocean depths takes care of 89 percent of the 330 terawatts of heat/year NOAA determined in 2010 the oceans are taking up on account of global warming.
So why wouldn’t you immediately start taking advantage of this environmentally rehabilitating form of energy?
The only rational reason for not doing so would be cost, but guess what?
OTEC is demonstrably the most inexpensive form of renewable energy that can be produced!
The following table from the recent MIT masters thesis by Shylesh Muralidharan shows the capacity and levelized capital costs of various energy technologies.
Although not shown in the table, Muralidharan points to a study that shows the deep water condenser architecture for OTEC, which is the design that moves heat most deeply into the depths and thus prolongs the time it would stay down there, brings down the installed capital cost of a 100 MW plant ship from 4000 $/kw to 2650 $/kw.
He also explains how the doubling of OTEC plant size leads to a cost/kW reduction of approximately 22%.
Using CO2 as the working fluid allows for OTEC plants of gigawatt capacity or more, so extrapolating from the study’s data a 1 GW plant of the deep water condenser design would cost $86*2650/4000*78/100*(1-(.22*(200/800))) or 42 $/MWh for the lowest levelized capital cost of all energy sources but for combined cycle natural gas.
By a considerable margin it would be the cheapest of the renewable energies and therefore what our rapidly warming planet is crying out for.
In view of the futile response to two years of advocacy for the lowest cost, most environmentally effective form of energy, one is left to ponder the question Casey Stengel posed of his 62 Mets Baseball Team, “Can’t anybody play this here game?”
Put another way, paraphrasing the late Frank Sherwood Rowland, 1995 Noble Prize Laureate in Chemisty, What’s the use of developing a solution if, in the end, all we’re willing to do is stand around and wait for the resolved problem to destroy us?
Photo Credit: Ocean Energy Sources and Decarbonization/shutterstock