Meredith I love the idea of subsidizing for damage not done but why not extend the principal to include benefits provided?
In that scenario OTEC would hands down be the winner.
Currently we derive approximately 14 terawatts of primary energy from fossil fuels and produce about 36 billion metric tons of CO2 in that process. Nihous estimates we could produce about 14 terawatts with OTEC and thus reduce CO2 emissions to zero as we could with nuclear wind or solar.
To get energy produced at sea to market however requires the conversion of the electrical energy to the energy carrrier hydrogn by electrolysis. A Lawrence Livermore team has demonstrated that electrolysis of saline water produces not only hydrogen, chlorine and oxygen gases, the resulting electrolyte solution is significantly elevated in hydroxide concentration, which are strongly absorptive and retentive of atmospheric CO2.
The formula is:
Every mole of hydrogen produces a mole of sodium that in turn precipitates a mole of CO2. A 100 MW OTEC plant produces about 35,000 kg of H2 per day or 12,775,000 kg a year which sequesters 562,000 metric tons of CO2. Full capacity OTEC would therefore sequester about 79 billion metric tons/year by the end of the century, which is about how long it would take to build to full capacity, thus CO2 concentrations could be returning to safe levels throughout the build out.
On land the hydrogen is converted in a fuel cell back to electrical energy and water in a process that is thermodynamically the opposite of electrolysis. The enthalpies and entropies are equal but with opposite signs so theorectically you get back the same amount of energy from the fuel cell as was used to electrolyze the water.
Fourteen terawatts produces 1.8 trillion kg of hydrogen a year which in turn converts to 16 trillion kg of water which at a height of 840 meters (the average land height) has the potential to generate an additional 4.3 terawatts of hydro or about 4 times what the world is currently producing.)
This 16 trillion kgs of water in turn is 600 gallons per year for each of the 7 billion of us living on the planet enough to services the recommended intake of a half gallon per day per person twice over.
The UN recommends the cost of water should be US 4 cents/day so this is another potential $100 billion revenue source.
As an added benefit OTEC remedies storm surge and sea level rise and replicates the conditions that have brought about the atmospheric warming hiatus but the topper is it also potentially the cheapest of the renewables and less than nuclear.