Deep water electrolysis produces hydrogen with the potential to produce mechanical, electrical and gravitational energy as well as water.
Hydrogen is a water and energy carrier. Compressed hydrogen has the highest energy potential by weight of non-nuclear materials. The most efficient way to produce compressed hydrogen is to perform electrolysis in deep water. When performed at a depth of 1000 meters the gas arrives at the surface pressurized to 100 bar.
The average land height is 840 meters. Raising desalinated ocean water consumes considerable energy. Hydrogen on the other hand is lighter than air and would rise from a depth of 1000 meters to any place on land of its own volition. It is a lifting gas because it is 14 times less dense than air. Above the surface compressed gas has the same energy potential as compressed air energy storage systems.
Hydrogen is most frequently associated with stationary or transportation fuel cells. In the latter case the gas is compressed to between 350 and 700 bar for spatial and range considerations but the optimal operating pressure of PEM fuel cell systems in automotive or stationary applications is about 6 bar.
The relationship between work required and the compression of a gas is logarithmic so only 30% more energy is required to compress a gas to 700 bar from 100. This extra work plus the potential inherent in the gas at 100 bar is recovered when the pressure is dropped back to the 6 bar used in the fuel cell.
In a fuel cell hydrogen is combined with oxygen to produce electrical energy and water in a process that is thermodynamically the opposite of electrolysis - the fuel cell produces the same amount of energy as is consumed in electrolysis.
Water produced by fuel cells on average would have a hydrological head of 840 meters or about four times the current potential of the Hoover Dam. Hydrogen and water can be combined in a stationary installation at any elevation however to produce energy and water and the head between where it is produced and where it is needed can be used either to augment the system's energy output or to facilitate water distribution.
What actions do you propose?
Most scientists agree that if carbon emissions are not dramatically reduced there will be irreversible catastrophic climate change twenty years from now. Vaclav Smil however has pointed out that it took 50 to 75 years for coal, oil and natural gas to become significant contributors to global energy portfolios even though the technology was largely available and cheap.
Since it is unlikely the world can transition away from fossil fuels much faster than it transitioned to them, in spite of the urgency to do so, it is imperative that the greatest environmental benefit be derived from every dollar spent on replacement technology.
For most of this century atmospheric warming was thought to have slowed, due principally to the movement of trapped heat into deeper ocean water.
The oceans are the repository of over 90% of the heat of global warming. Since warm water is less dense than cold the oceans are becoming increasingly thermally stratified and this in turn enhances the conditions for producing energy in a heat engine.
Wind and density issues associated with the melting of polar ice are the mechanisms that moved heat to deeper water between 1998 and 2014. Both of these are believed to be temporary phenomena however that when reversed, as appears to be happening now, will see much of the so called missing heat returned to the atmosphere.
As is apparent from the following diagram heat was only driven down about 50 meters in the Western Pacific Ocean, to about 250 meters, by the strong La Niña conditions that existed for the most part between 1998 and 2014.
To produce energy with ocean thermal energy conversion or OTEC heat engines a temperature differential of at least 20C is required between the surface and the cold, deep, ocean, heat sink.
Water is at its maximum density at a temperature of 4C and as can be seen from the following diagram of the ocean thermocline, the oceans universally are that temperature or less at a depths of 1000 meters or greater.
As is apparent from the following diagram, delta Ts of 20C between the surface and 1000 meter ocean depths exist universally between latitudes 20 degrees either side of the equator.
The efficiency of a heat engine is equal to 1- the temperature of the cold reservoir – in degrees Kelvin – divided by the temperature of the hot reservoir.
For surface temperatures 20C greater than 4C this would be 1-277/297 or about 7 percent. Practically this would be closer to 5 percent, at best, which means to produce 1 unit of energy it is necessary to move 20 times more heat from the surface to at least 1000 meters.
The rate of warming of the oceans is over 300 terawatts (TW) or about 5 Hiroshima bombs worth every second.
In the estimation of Gerard Nihous of the University of Hawaii, the oceans can produce about 14 TW of energy without adverse environmental impact. This would be a direct conversion of 14 TW of the 300 TW accumulating due to global warming to productive work in accordance with the 1st law of thermodynamics and the movement of at least 280 more thermal units to deep water.
Effectively this a mitigation of over 90 percent of the heat of global warming.
OTEC using a heat pipe therefore is an approach to producing energy that buys time to transition away from fossil fuels and puts irreversible catastrophic climate change on hold.
At the ocean surface accumulating heat produces storms and contributes to sea level rise due to thermal expansion. The storms also move heat towards the poles where they melt icecaps further exacerbating sea level rise.
A heat pipe is a device that moves heat away from locations where it can do damage to somewhere benign. It does this with phase changes of a working fluid and energy can be produced by inserting a turbine into the vapor stream of such a device.
This design moves warming heat to a depth of 1000 meters from where, with an estimated return rate of 4 meters per year, it would take 250 years to return to the surface as opposed to decades, at most, as a consequence of the shallow heat movement resulting from the natural influences of wind and ice melting that have recently slowed atmospheric warming.
Sea level rise and storm surge are two of the greatest risks of climate change and are both mitigated by moving heat away from the ocean’s surface. At a depth of 1000 meters the coefficient of expansion of sea water is half that of the tropical surface and heat removed from the surface is no longer available to drive storms.
As is apparent from the diagram showing ocean temperature delta Ts, energy produced with OTEC would be generated remote from most major markets in North America and Europe but close to those in Asia.
In order to get this power to market it is necessary therefore to convert the electricity generated to an energy carrier like hydrogen.
Other carriers, like ammonia, have been proposed but hydrogen would be ideal because it is as much a water carrier as it is an energy carrier and water is even more vital than energy.
Hydrogen is the ideal energy carrier because compressed it has the highest specific energy of any non fissionable material. It produces over 3 times the amount of energy as an equal weight of gasoline and when burned or is converted to electricity in fuel cells water is the only by-product.
It is also an ideal water carrier as outlined in the summary above.
Hydrogen’s drawbacks are the energy required to compress it to the 350 to 700 bar (atmospheres) needed for volume and range considerations in most transportation applications and the CO2 produced by steam reforming of natural gas, which is the principal way the gas is produced commercially.
Steam reforming is used because electrolysis is between 3 and 10 times more costly but the CO2 negates much of the environmental potential of hydrogen when both are produced by this process.
High-pressure electrolysis is the cheapest form of electrolysis because it eliminates the need for further compression of the gas.
At 1000 meters, the deepest extent of a heat pipe OTEC system, the water pressure is 100 bar and electrolysis performed there would bring hydrogen to the surface at that pressure. Further when the electrolysis is performed with the technique developed by a team of Lawrence Livermore scientists, atmospheric and dissolved ocean CO2 is sequestered and ocean acidification is neutralized.
This is another way to buy the time necessary to avoid climate catastrophe and to transitions away from fossil fuels.
If climate catastrophe is imminent, we should be prepared to address the problem regardless of the cost. That is the primal human response to existential threats but as is discussed in the cost section below, heat pipe OTEC may be the renewable energy with the lowest levelized cost and therefore should be transitioned to on that basis alone.
It will take trillions of dollars to transition to technology that solves climate change.
Before committing to anything like that kind of expense systems will have to prove they can produce the quantities of energy that are required to replace fossil fuels and further that they will not exacerbate the climate problem.
All of this has to be done within a framework of impending climate catastrophe so it is imperative that all efforts comport with sound science and further it would be folly not to follow natural example.
The essence of global warming is the production and consumption of energy. The science of energy is thermodynamics. It is impossible to effectively address climate change within any framework other than the laws of thermodynamics.
The first law says energy can be transformed from one form to another, but cannot be created or destroyed.
The second law has a number of components. One says heat flows naturally from regions of higher temperature to regions of lower temperature, but that it will not flow naturally the other way. Another says you can extract work from this flow by moving the heat through a heat engine.
Global warming is trapped heat. The only thing you can do with this is transform some to useful energy and move the rest to a colder location, preferably where it will do the least damage.
Most of the heat is currently going into the tropical ocean and the buoyancy of warm water keeps it near the surface. Nature’s response to this heating is to convert some of the excess to mechanical energy in the form of storms. These in turn move heat away from the equator towards the poles, where it is a significant problem due to icecap and permafrost melting.
The ocean abyss is an even greater heat sink than the poles and one where, due to the unsurpassed thermal capacity of water, a great deal of heat can be relocated without significantly increasing the water’s temperature and thus the abyss is the place where the heat would do the least damage.
A tropical storm is powered by the evaporation and condensation of water.
A heat pipe is a device that boils a working fluid, Nature uses evaporation to change water phases, to move heat away from someplace it can do damage to somewhere benign. There are a number of fluids that will boil and condense, at the right pressure, within the range of 25C and 4C existing in the layered tropical water. These pipes can overcome the tendency of heat to remain near the surface because the movement depends on the pressure difference between the boiling and the condensing ends of the pipe. Heat moved this way can overcome gravity and a turbine place in the vapor stream can convert some of the flow to productive work.
Heat pipe OTEC replicates Nature’s response to climate change, potentially has the lowest levelized cost of all renewable energies, has baseload potential and is constantly available, moves the heat of warming to a safe location, electrolysis of sea water sequesters atmospheric and dissolve ocean CO2 and hydrogen produced at depth has diverse energy potential.
The problem is none of this potential is proven.
It is proposed therefore that this testing should begin immediately. First with the lab scale demonstration pictured below that can prove power can be produced with a heat pipe design operating within the projected temperature range.
This test could be completed within two years for less than $1 million.
Should this test prove successful, a small ocean going model, costing in the range of $50 million, should be tested over a period of 2 to 3 years.
The lessons learned from these tests would then be incorporated into a production model that would be in the 100MW range, cost about $275 million, and that could pay for itself out of revenue.
Currently there is little appetite in either the public or private domain for risk taking on untested ventures.
In spite of the theoretical environmental potential of this proposal it will likely take policy and financial innovation to move it forward.
Politicians do not typically fund projects with commercial potential, even if that potential is not being capitalized on in the public sector. As legislators their tendency is to be proscriptive rather proactive in terms of risky ventures that address significant issues.
The recent court case in the Netherlands however, where the court ordered the government to cut the country's greenhouse gas emissions by at least 25 percent by 2020, may give politicians, universally, pause to consider the issue of how they might, most effectively, reduce their country’s emission while continuing to provide the energy their economies need to move forward.
Also in jurisdictions like California climate change is having a significant and negative impact on the economy already so the state would not only benefit from technology that would provide water and energy locally, its economy would flourish as the hub of an industry that could provide these benefits to the world.
History is replete with examples of small, public, investments translating into significant private sector economic activity and it is the proponent’s opinion this would be the case in this instance as well.
Who will take these actions?
The Netherlands case makes a compelling argument for the proposition that governments have a legal obligation to protect their citizens from the dangers of climate change.
The United States National Climate Assessment warns that American citizens are already experiencing the consequences of global warming, and that their health and livelihoods will be even more at risk as temperatures rise.
It also makes more sense for developed countries, like the US, to provide emerging nations with energy that can mitigate the climate problem and provide economic activity rather than to pay climate reparations that probably have limited remedial environmental impact.
The most compelling US example of the problem is the ongoing drought in California, also the center of venture capital activity in the country and of automotive research focused on hydrogen fuelled vehicles.
The world is looking to the United States and in turn California for leadership on climate change and it is in the interest of the government of both to respond.
It is in their economic as well as environmental interest to do so.
Wealth comes from the sale of extracted resources or manufactured products.
Renewable energy stems from manufactured devices that can harness the free energy Nature provides on a continuous basis. It is a way to harness the revenue stream of both the energy and manufacturing sectors.
As the proponent of this solution it is my responsibility to try to make the case for the worthiness of the proposition and also to try to build the team that can move the effort forward and acquire the funding necessary to do the required R&D.
The automotive sector has made a substantial investment in hydrogen powered vehicles but their case is undercut by the way hydrogen is currently, for the most part, produced. This case and the one for expanding hydrogen infrastructure would be bolstered by the production of this energy/water carrier in a way that mitigates both the cause as well as effect of climate change.
Where will these actions be taken?
Ultimately it would take every shipyard and every mine on the planet to fully implement this solution.
Initially, as a resident of British Columbia, the proponent would like to see the R&D undertaken and be directed from BC and California, where decades of hydrogen related research has already taken place.
Governor Schwarzenegger of California and Premier Campbell of British Columbia committed in 2007 to an $89- million "hydrogen highway" between Vancouver and Whistler BC in time for the 2010 Winter Olympics. Although that effort failed a similar collaboration centered on this effort might revive it and both might be the basis for a global hydrogen effort. Both have maintained subsequent economic activity in the fuel cell sector and those efforts are a sound footing upon which to move forward.
The initial lab scale study will be a modest undertaking therefore its economic significance will be minimal as will be the importance of where it takes place.
Neither British Columbia nor California waters are conducive to the generation of OTEC power but that does not prevent them from becoming the co-hubs of an industry that would generate and transport power globally from mid-ocean regions.
As discussed in the time line section below, it will take a century long, all out, global, effort to solve the global warming problem but as with any effort it begins with a single step. Since these have already been taken in British Columbia and California it seems logical that the advancement should proceed from there but the proponent is not married to any particular business plan.
He is open and receptive to any input and collaboration that can advance what he presumes to be is a valid, scientifically based, solution.
How will these actions have a high impact in addressing climate change?
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 but it isn’t likely that would be fully attainable until the end of the century.
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 could therefore sequester about 79 billion metric tons/year by 2100 and return atmospheric CO2 concentrations to safe levels.
What are other key benefits?
Heat uptake in the deep oceans has caused the hiatus. This is replicated with a system that produces as much energy as is currently consumed.
As this is an emissions free approach to producing energy, atmospheric concentrations of CO2 would be reduced by the time the heat reemerged, estimated at 250 years as the return rate is 1cm/day, at which point it could be re-returned to the deep with the same process.
Moving heat away from the surface saps the energy of tropical storms that bring with them the dual threats of wind and low pressure driven storm surge and move heat towards the poles where it melts ice.
Moving heat into the deep reduces thermal stratification that is cutting phytoplankton, the base of the ocean food chain and the lungs of the planet, off from the nutrients they need to survive.
The output of fuel cells producing 14 TW of power is 16 trillion kgs of water, which is about 600 gallons of water per year for every person on the planet; twice daily recommended consumption.
What are the proposal’s costs?
The initial R&D estimates are $1 million for lab work and $50 million for a small scale ocean going prototype.
The MIT masters thesis of Shylesh Muralidharan illustrates the high capacity factor of OTEC as well as its competitive levelized capital cost with respect to other technologies. (Although not shown in the following table from the thesis, the paper points to a study that shows that the deep water condenser architecture – the heat pipe design - can bring down the installed capital cost of a 100 MW plant ship from 4000 $/kw to 2650 $/kw.)
The thesis also shows that each doubling of plant size leads to a cost/kW reduction of OTEC plants by approximately 22%.
Using CO2 as a working fluid allows for plants of gigawatt capacity.
Extrapolating from the thesis a 1 GW plant of heat pipe design would cost $2650*.88*.88*.88*(1-(.22*(200/800))) or 1707$/kw and have the lowest levelized capital cost of all energy sources but for combined cycle natural gas.
Nihous's 14 TW is based on 250,000 100 MW plants or 25,000 GW plants so the total cost of OTEC infrastructure would be about $43 trillion.
(A case study of a hypothetical 100 MW OTEC plant analyzing the prospects of OTEC technology by Dr. Subhashish Banerjee et. al (page 125) determined that hydrogen production from a 100 MW OTEC plant would be over 35,000 kg/day. OTEC's 14 TW would equate then to 1.8 trillion kg/year which in turn converts to 16 trillion kg of water which at a height of 840 meters has the potential to generate 4.3 terawatts of hydro or about 4 times what the world is currently producing.)
In 2011, expenditures on energy totaled over 6 trillion USD. Since OTEC's 14 TW + 4.3 from ancillary hydro would more than supplant current usage of about 16 TW of primary energy, this one technology could dominate the global energy sector.
If only half the 6 trillion went to defraying the cost of infrastructure it could be paid off in about 15 years, assuming no interest was charged on the initial investments.
Carbon Lock-In is the self-perpetuating inertia created by large fossil fuel-based energy systems that inhibits public and private efforts to introduce alternative energy technologies. It will take a long time to turn the global energy ship around so it is imperative we get the greatest benefit from the actions taken to prevent a greater than 2ºC temperature increase. With OTEC every watt of energy produced is a thermal watt of global warming heat converted to productive use and at least 20 more thermal watts moved to the safety of the abyss. No other energy form cools the oceans and atmosphere, reduces sea level rise, cyclones and the melting of ice caps and permafrost.
It will take up to 5 years to first prototype, at lab scale, the system that can provide these benefits and then test the lessons learned at that scale on a small ocean going system.
Gerard Nihous of the University of Hawaii estimates the oceans are capable of supporting about 250,000 100MW plants.
During the Second World War the allies built 637,248 planes and 54,932 ships. As only about 8,000 of these ships were considered large, for arguments sake, it is assumed about 16,000 equivalent to OTEC plants worth of ships were built and about half that in plane equivalents.
It would take therefore a full war time effort the rest of this century to reach OTEC’s full potential.
It also has to be noted that at the end of the war the vast majority of the ships and planes either had been destroyed or were obsolete and written off, whereas OTEC plants will be revenue generators from day one.
Thermodynamic geoengineereing: a fourth way. Thermal stratification of the oceans induced by global warming presents the opportunity to convert warming heat to productive energy.
The Intergovernmental Marine Bioenergy and Carbon Sequestration Protocol pitches: Low cost carbon negative fuel can be produced in abundance within the oceanic commons.
Quantitative Easing for Climate Change Mitigation + Adaptation. We cannot conventionally afford the huge funds needed to resolve climate change in time. Let’s be unconventional.
Saving the Planet, v2.0. Interested in air CO2 removal, carbon-negative fuel, saving the ocean, and redrawing the global energy map?
Links to papers, studies, reports etc. referenced in this proposal are shown in light blue.
Further writing by the proponent on the topic are:
The Lessons of Nature and Heat Pipe OTEC, OTEC Matters 2015, 130-147.