Climate mitigating energy production

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One hundred fourteen nations committed to limiting the global average temperature increase to no more than 2 degrees Celsius above pre-industrial levels. The Copenhagen Accord also includes a reference to considering limiting the increase to below 1.5 degrees, as demanded by vulnerable developing countries.

 

It is anticipated by the end of this year the average global temperature will have risen half way towards the 2 degree limit and two thirds of the way to 1.5 degrees.  

Prior to 1998 global temperatures were increasing at a rate of about 0.21 degrees each decade. From 1998 to 2012 however the observed decadal rate of warming was just 0.04 degrees. This slowdown or “hiatus” has been attributed to the movement of heat to deeper water in the eastern Pacific Ocean as a consequence of stronger than normal trade winds.

 

Were we capable of perpetuating the hiatus rate of temperature increase, as in fact we can, or even better it, 1.5 degrees, or better, is achievable.  

 

The trade winds stacked warm water in the eastern Pacific driving the thermocline down to a depth of about 300 meters. Once these winds subsided however, in 2013, this stacked water sloshed back to the west and to the surface with the result 2014 and 2015 have successively been the warmest years ever recorded.

 

 

  Hiatus Thermocline  Current Thermocline

 

During the hiatus the vast majority of this heat was never mixed nor was it diluted by the by the enormous  heat sink of the ocean abyss that exists below the thermocline.

 

The oceans are the repository of 93 percent of the heat of global warming. Since warm water rises, most of this heat sits near the surface of the ocean while the temperature at depth approaches water’s freezing point. This differential makes the oceans, particularly tropical waters, the largest battery on the planet. When heat flows from a warm source to a cold sink through a heat engine, just as when electrons flow from the negative to positive terminal of a battery, energy is produced.

 

 

It is estimated the oceans have the potential to produce 14 terawatts of primary energy through ocean thermal energy conversion or OTEC, or about the same amount of energy as is currently derived from fossil fuels.

 

NOAA estimates the ocean battery is being charged at a rate of about 330 terawatts each year and since there is no draw down of this inexorably increasing charge we are experiencing the escalating consequences of global warming.

 

Due to the low thermodynamic efficiency of a heat engine operating within the temperature range of the oceans OTEC requires the movement of about 20 times more heat to the deep than the14 terawatts of power the oceans are capable of producing.

 

In other words, virtually all of the heat the ocean battery is accumulating is either converted to work or benignly moved to deep water.  

 

In support of this premise, in the late 1970s a team from the Applied Physics Laboratory of Johns Hopkins University estimated that the surface water temperature of the oceans, and therefore the lower atmosphere as well, would be reduced by 1C each decade through the production of 5 terrawatts of OTEC power.

 

The relocation of this heat to the deep would be benign due to the large thermal capacity of water. It is estimated that in spite of all the heat they are absorbing, at depths from 500 to 2000 meters, the oceans are warming by about .002 degrees Celsius every year, and in the top 500 meters, they’re gaining .005 degrees C.

 

The benefit of this heat absorption is noted by Levitus, who points out that if all of the heat the oceans absorbed to a depth of 2000 meters from 1955–2008, which raised their temperature by an average .09 degrees Celsius, was instantly added to the lower 10 kilometers of the atmosphere that layer would be warmed 36 degrees Celsius.

 

It is obvious therefore that the objective of Copenhagen is well within reach provided we produce the energy the world demands with the right technology.

 

The OTEC heat pipe design overcomes the cost and environmental concerns of conventional OTEC designs and moves heat through the phase changes of a low boiling point working fluid, to a depth of 1000 meters. From there it would take 250 years, at a return rate of 4 meters annually, to reemerge and by that time carbon dioxide concentrations in the atmosphere will have declined due to the replacement of fossil fuels with zero emissions energy and these concentrations can further be reduced significantly with an electrolysis process that produces hydrogen as an energy carrier for mid-ocean derived power.

 

Full capacity OTEC -14 terawatts - could sequester about 79 billion metric tons of carbon dioxide each year.   

 

That amount of power would also produce 1.8 trillion kilograms of hydrogen through the electrolysis of 16 trillion kilograms of water and when reconstituted on land through the production of energy in a fuel cell or by burning in an engine the byproduct would be 600 gallons of water for every person on the planet.

 

A widely-used model estimates the social cost of anthropogenic greenhouse gas emissions at $326 trillion by 2200.

 

A new University of Cambridge study shows that melting permafrost will release sufficient carbon dioxide and methane to increase that cost by an additional $43 trillion.

 

The technology that slows or reverses global warming can not only prevent these losses, it can generate trillions of dollars in revenue for the providers of the technology.

 

We can't afford not to keep warming below 2oC.

 

 

2 Degrees Celsius