The paper Observed multi-decadal increase in the surface ocean’s thermal inertiademonstrates how the ocean's surface layer regulates the Earth's climate by absorbing excess heat from the atmosphere and helps to maintain global temperatures.
The study found a significant increase in the persistence of sea surface temperature (SST) anomalies globally since 1982. This trend is attributed to three main factors: deepening of the surface mixed layer, the weakening of the ocean’s influence on the Earth's climate and reduced damping of SST oscillations. The first two are short-term effects, and the latter is longer-term, leading to increased duration of marine heatwaves that threaten marine life and the ocean’s diminished capacity to sequester heat.
For a warming planet, an ocean with a diminished capacity to sequester heat means an atmosphere with an increased capacity to aggregate heat, with disastrous consequences.
Inertia suggests passivity, resistance to change, and a lack of motivation. Enterprise is the opposite. It implies initiative, action, and a willingness to take on challenges. In essence, enterprise is about taking action to achieve a goal, whereas inertia is about resisting action, as is happening with climate change.
The mixed layer of the ocean, typically extending down a few hundred meters, is characterized by relatively uniform temperature, salinity, and density. It directly absorbs heat from the sun and the atmosphere. As the atmosphere warms due to greenhouse gas emissions, this heat is transferred to the ocean's surface. As that surface warms, it becomes less dense and less likely to mix with colder, deeper waters, which creates a pronounced stratification, with warmer, less dense water at the surface and cooler, denser water below.
This stratification traps heat in the upper layers, further accelerating surface warming. It prolongs marine heat waves and impedes the exchange of oxygen and nutrients between the surface and deeper waters, affecting marine ecosystems. And it amplifies the energy potemtial of ocean thermal energy conversion (OTEC).
The conventional wisdom is that OTEC is a niche technology due to its low efficiency, high costs, and engineering complexity. It requires massive volumes of water; however, a deepwater condenser design, as Thermodynamic Geoengineering (TG) provides, moves heat through the phase changes of the working fluid within the evaporator and condenser rather than relying on the sensible heat of water for heat movement. This approach is 2.5 times more efficient and half the cost.
The only vertical movement of water occurs as the heat released by the deepwater condenser, located at a depth of 1,000 meters, diffuses back to the surface at a rate of 4 meters per year. Although the heat exchangers are large, when manufactured by using magnesium alloys, which are available in the ocean at concentrations three times greater than CO2 in the atmosphere, and with a proprietary thin-film design, these heat exchangers can be up to ten times smaller and one-third cheaper than the conventional shell and tube heat exchanger featured by earlier OTEC efforts.
In contrast to conventional cold water pipes, which are massive, the heat pipes used in a deepwater condenser design are one order of magnitude smaller, reducing system costs by at least 30%. And instead of ammonia, carbon dioxide can be utilized as the working fluid, which enhances OTEC efficiency due to the proximity of the density of the working fluid in both its liquid and gaseous states at the operating temperatures.
Power plants are typically about 1 gigawatt in size to take advantage of economies of scale. According to the paper "Ocean Thermal Energy Conversion (OTEC) Economics: Updates and Strategies," the capital cost formula is given by 61980 x [Plant Size (MW)]-0.348. The capital cost for a 1 MW plant is therefore $61980 per kW, while a 1 GW plant has a capital cost of $5,601 per kW.
The paper suggests that thin-film heat exchangers could reduce this cost by 33%, and the deep water condenser, due to smaller pipes and infrastructure, would lower the cost by an additional 30%. This means the total cost for a plant would be approximately $2.6 billion, with a capacity utilization of 97%.
With respect to global warming, the excess heat is estimated at 500 terawatts. With an efficiency of 7.6%, as is the estimation of the experimental physicist Melvin Prueitt in his patent Heat transfer for ocean thermal energy conversion, about 38 terawatts (TW) of primary energy is available for conversion to work.
The paper Quantification of ocean heat uptake from changes in atmospheric O2 and CO2 composition by Resplandy et al. used the measurement of atmospheric oxygen and carbon dioxide levels as the oceans warm and release these gases as a proxy for global warming. They calculated that between 1991 and 2016, the average warming amounted to about 1.29 ± 0.79 × 1022 Joules of heat (409 TW/year), equivalent to a planetary energy imbalance of 0.80 ± 0.49 W/m2 of the Earth’s surface.
NASA and other studies have indicated that the Earth's energy imbalance is, as of 2023, approximately 1.41 watts per square meter, or about 175% higher than it was 20 years earlier.
The earliest we are likely to be able to start bringing ocean heat under control by doubling the current installed capacity of 100kW/yr of OTEC would be 2055. At that time, assuming a doubling of the 2004 energy imbalance every 20 years, the accumulated total heat would be 3300 TW. Since it will have taken about 250 years from the start of the industrial revolution to have built up this inventory, it will take about the same length of time to dissipate it by converting about 409 TW of ocean heat to work at 7.6% efficiency each year and then recycling the balance 12 more times.
Therefore, it would take around 31,000 1 GW plants to convert the heat of warming to work, at a cost of $2.6 billion each, for a total of about $80 trillion. These plants have an operational life of 30 years; therefore, the annual cost would be $2.7 trillion. This figure is about 10% lower than the 2023 global cost of oil consumption, which generated only two terawatts of energy. Additionally, factoring in the annual fossil fuel subsidy of $7 trillion per year, calculated by the IMF, OTEC is at least 30 times cheaper than oil. And if 31,000 1 GW OTEC plants produce 332,880,000,000 kWh annually, the cost per kWh would be .9 cents.
OTEC vs. Wind/Solar: The Hidden Costs of Storage
In 2023, Lazard estimated the unsubsidized LCOE of solar PV is between $0.03–0.06/kWh, and for wind, it was $0.02–0.05/kWh, assuming grid stability (no storage). With Storage (4–8h lithium-ion batteries at a $0.02–0.10/kWh, the total cost would be $0.05–0.15/kWh. And for long-duration storage (24 h+), the cost would be $0.10–0.30/kWh for a total of between $0.15–0.40/kWh.
The real-world example (California) for solar curtailment (excess wasted energy) hit 2.4 TWh in 2023, enough to power 200,000 homes annually.
OTEC vs. Nuclear Power: The in-your-face of fission.
Scott Kemp, an associate professor of Nuclear Science and Engineering and director of the MIT Laboratory for Nuclear Security and Policy, says in the Utah News Dispatch article “Glowing pains: Developing nuclear power could cost Utah tens of billions: “You can buy nuclear power that will give you a gigawatt of carbon-free energy for $10 billion, or you can buy wind and solar that will give you four gigawatts of carbon-free energy for $10 billion”. And whereas the advantage of economy of scale goes to OTEC, nuclear power does the opposite with Small Modular Reactors. Plus, atomic power defies the Law of Holes. A law cautioning against digging by producing waste heat in a warming world.
Four gigawatts of OTEC would cost you $10.4 billion, but it saves between $0.10–0.30/kWh in wind or solar storage at half to a third of their cost, assuming grid stability. Furthermore, wind and solar energy do not address sea level rise or storm surge. Utilizing a heat pipe to transfer heat into deep water can reduce thermal expansion by 25%. This is because the coefficient of thermal expansion is half at a depth of 1,000 meters compared to the tropical surface. Moving heat to about 500 meters can significantly decrease thermal expansion by averaging the depths. Furthermore, heat relocated to this depth can no longer contribute to melting ice caps or intensifying tropical storms.
There are substantial social benefits to this method of deep heat transfer that have yet to be monetized. In the book "The Promise of Frontier Technologies for Sustainable Development," Vijay Modi suggests that unstored solar power could become “too cheap to meter.”
TG is solar power already stored in the stratified layers of the tropical ocean.
OTEC only works in tropical zones (20°N–20°S), covering ~10% of the ocean's area. However, the heat of warming accumulates in this area at a rate of about 80 watts per square meter and dissipates in the higher latitudes. Ten percent of the ocean surface, which is 510 trillion square meters, times 80 watts per square meter, is about 4080 terawatts per square meter, but only about 10% of this can be converted in a single year.
Conventional OTEC, at a capacity of 31 TWs, would upwell 62 million m3/second of cold water, producing a significant ecological impact, including offgassing of CO2 from the ocean to the atmosphere. It also dumps the heat of warming to between 70 and 100 years in the mixed layer of the ocean, where the diffusion rate of heat is 1 meter/day. Therefore, the heat would return to the surface in about three months, providing no long-term climate respite. Over the course of 1000 years, the heat of warming would be recirculated about 4000 times, and at the same time, the tropical surface will have cooled by about 4 °C at the cost of the warming of the Arctic by the same amount.
Conversely, TG diffuses water from a depth of 1,000 meters at a rate of 4 meters/year for a total of 4.4 times over the course of 1,000 years. At a rate of 62,000,000m3/(226 years*365 days*24hrs*60mins*60secs), this would be about .0008 Sv. Therefore, there would be no ecological impact, shift in the thermohaline circulation, increase in algal blooms (climate shifts), or heterogeneous surface warming.
There would be no thermal pollution with TG because the surface temperature would be about 1.7 degrees higher than the preindustrial temperature 30 years from now, which would be reduced (1.7/250) about .007 degrees each year at the expense of the warming of a 1000 column of the tropics by .000007 degrees/year. After 250 years, the heat trapped in the ocean would be recycled 12 more times over about 3250 years, so there would be essentially zero impact on the sea life in the abyssal zones.
A 1 GW TG plant occupies 28,314 m2 since it consists of 66 evaporators of a length of 33 meters by 13 meters wide, angled at 60 degrees to form the two sides of an equilateral triangle that is the strongest available structural configuration. This arrowhead (per the following graphic) shows TG in a hydrogen production configuration) can move through the ocean at 2 knots, seeking out the highest sea surface temperatures available to produce work. Thirty-one thousand of these plants would cover 850 square kilometres or 0.0003% of the ocean’s surface. So once again, they would provide essentially zero sunlight blockage or aquatic-life impact.
With the cheapest energy extant, that mitigates every consequence of warming, where are the moguls?