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On 100 Percent Renewable Energy is 100 Percent Possible

I realize it is a great deal of heat and that is why I worked on the counter-current heat transfer system to try to find away around dumping that much into the deep. As was pointed out to me by Martin Hoffert 30TW would probably be enough to overturn the Thermohaline circulation using the conventional approach.

Gerard Nihous thought only a few years ago 5TW was the upper limit for OTEC because it would dump so much heat the Carnot efficiency would drop even lower. His work was the impetus for trying to find a way around the problem in the first place.

Thank you for your input.

April 27, 2013    View Comment    

On 100 Percent Renewable Energy is 100 Percent Possible

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25 Tw/year, the world currently operates on 16TW.

To generate 1TWh from a low temp heat engine operating at 3percent efficiency requires you to move 34 TWh of heat.

The question is can you return that heat rapidly to the surface in a closed circuit counter current heat transfer system?

With respect, I will take my counsel on cooling the oceans surface from the former Chief Technologist with NASA, Woods Hole Oceanographic Institution, the University of Hawaii and Florida Atlantic University and Dominic Michaelis, Founder, Energy Island Ltd.

Re: thousand years, according to the IPCC, "complete elimination of CO2 emissions is estimated to lead to a slow decrease in atmospheric CO2 of about 40 ppm over the 21st century."

It would take 3 centuries therefore to return to the pre-industrial base. According to the University of Calgary and the NAS, "Following cessation of emissions, removal of atmospheric carbon dioxide decreases radiative forcing, but is largely compensated by slower loss of heat to the ocean, so that atmospheric temperatures do not drop significantly for at least 1,000 years."

Re the Chemistry and Physics, perhaps a perusal of the American Institute of Physics, The Carbon Dioxide Greenhouse Effect, might be in order.

April 26, 2013    View Comment    

On 100 Percent Renewable Energy is 100 Percent Possible

No claim made to cooling the planet, only the surface of the ocean which in turn fuels tropical storms.

No claim made to depositing 330TW to the depths and having it stay there. Claim of coverting 25TWh to work.

I guess you count NOAA and the National Academy of Science as cheerleaders spouting nonsense? The 1000 year projections are theirs here and here.

The carbon cycle is well understood and outlined on my web page.

 

April 26, 2013    View Comment    

On 100 Percent Renewable Energy is 100 Percent Possible

Nathan, I stand to be corrected, but I don't think you necessarily violate the Carnot equation if you recapture the latent heat of condensation, which is virtually all of the heat in the system after you extract the work through the turbine, in a system of coils at depth and return it in the condensed working fluid in parallel to the descending vapour.

Most of it is going to return to the surface in the water via convection from the depths in any case.

What is the difference if you dissipate this heat to the deep or return it in parallel to the descending vapour?

And what is the difference if most of the latent heat of evaporaton is recovered from the depths rather than from the surface?

The velocity in the vapour tube between evaporation and condensation ought to be the same either way. That is how a heat pipe works and in this case you are simply putting a turbine inside the vapour column. It gets a little hairy at the bottom because you have to expose the condensed vapour to the deep cold to drop its temperature and then return it through the coils inside the vapour tube at the bottom upon which the descending vapour condenses. The vapour from the coils is then pumped back to the surface in a series of break tanks surrounding the vapour column. 

It is the drop in pressure when the vapour condenses that provides the impetus for the vapour movement.

Obviously you can't capture all of the latent heat in the coils but you should be able to get a most of it and the coils strengthen the heat pipe against the crushing forces at depth.

Again I stand to be corrected and would love to do the experiment one way or the other.

Even if this is wrong, the heat pipe is still the better option cost wise and environmentally.

 

 

April 26, 2013    View Comment    

On 100 Percent Renewable Energy is 100 Percent Possible

Hi Schalk

Getting energy from the middle of the oceans provides one more opportunity to address the problem of sea level rise. Convert liquid ocean volume to gas by electrolysis and transport the energy/water currency – Hydrogen – to shore. Or as others prefer produce NH3 or CH3OH as the energy carrier.

Engineers look at EROI, while disregarding the $28 trillion in potential damage to coast infrastructure the insurance company Allianz has identified and strorms like Hurricane Sandy presage.  

OTEC mitigates this problem five ways:

  1. converting heat to work to lessen thermal expansion.
  2. desalination with the open cycle.
  3. electrolysis to convert liquid volume to gas.
  4. moving surface heat to the depths where the coefficient of expansion is half that of the tropical surface, and
  5. sapping the tropical energy of storms that move the heat to the poles that is melting the icecaps and the permafrost.

Conventional OTEC structure are massive and costly as a consequence of the need for massive movements of water. For a 50MW plant this is about 400m3/sec. Using a heat pipe design however – moving heat by phase changes of a working fluid you can produce 50MW with the movement of only 8m3/sec of ammonia in a closed system that avoids environmental damage. This reduces the size of the piping one order of magnitude with a commensurate reduction in cost.

By using a counter-current heat transfer system diagramed in this link, as does a typical heat pipe, you also limit the amount of heat transferred from the surface to the depths and thus you maximize the amount of energy you can produce. With such an approach, 25TW would be a lower limit because with an ideal heat pipe the amount of heat taken in at the evaporator end equals the amount lost through condensing end. With conventional OTEC you move 20TWh to the depths to produce 1TWe. With the heat pipe and counter-current you extract 2TWh from the surface, produce 1TWe and dumpt 1TWh to the depths.

OTEC will have a meaningful impact on global warming because first it is carbon free and combined with 25 plus TWh conversion you get a reduction of about 40 ppm of CO2 every century once you stop adding CO2 to the environment. In 300 years you would be back to pre-industrial concentrations and in the meantime you would be extracting the excess heat from the oceans that is doing all the damage.

Current projections are global warming is locked in for 1000 years after CO2 emissions are completely stopped and that the seas will rise an additional 320% this century due thermal expansion.  

The problem is accumulating heat in the oceans.

It is hard to see how you address climate change by avoiding the problem.

There is no question the use of energy on land adds to the problem but I don't think you are going to prevent the energy deprived from seaking to thwart their deprivation.

You can fill there need, say 30TW, with nuclear or fission and add an additional 60TW of waste heat to the ocean or take that 30TW out of the ocean in the first place.

To my simple mind the answer is fairly obvious. It is ocean energy reduced on investment.

 

April 25, 2013    View Comment    

On Carbon Emissions and the Future of Cars and Light Trucks

Nathan, a recent article in the Globe and Mail, suggests some advances are being made on the FCEV front.

April 25, 2013    View Comment    

On 100 Percent Renewable Energy is 100 Percent Possible

Schalk, 90 percent of heat attributable to climate change has been accumulating in the oceans. It is causing thermal expansion and the erosion of the icecaps.

A portion of the 330 TWh a NASA study suggests has been accumulating there, can be converted to work by the process of ocean thermal energy conversion (OTEC).

Ray Schmitt, Woods Hole Oceanographic Institution, suggests OTEC's potential is 15-24 TW; whereas the world currently operates on a bout 16 TW.

Gerard Nihous, suggests as much as 25 TW is available here.

The more energy produced by this method, the more the ocean's surface would be cooled, which in turn lessens the threat from tropical storms and reduces the movement of heat towards the poles.

The oceans are the largest heat repository on the planet at the same time as they are the largest heat sink. Virtually all other forms of energy production and all energy use adds to the problem of ocean heat.

OTEC is the only form of production that ameliorates the problem.

The more energy produced, the more the ocean is cooled.

It is a renewable with a bright and virtually limitless horizon. 

 

April 25, 2013    View Comment    

On Will Water Limit Fracking and Natural Gas Development in Saudi Arabia?

Geoff, it never ceases to amaze me that oil tankers deadhead with salt water in their ballast tanks as opposed to fresh water, which they can load at the mouth of virtually any major river as it enters the oceans.

Canada has, for example, a virtual embargo on water exports.

It does not apply to ballast water.

April 23, 2013    View Comment    

On Climate Change and the Peak Oil Flip-Flop

Jim, Ray Schmitt, Woods Hole Oceanographic Institution, shows OTEC's potential to be 15-24 terawatts.

Gerard Nihous, suggests as much as 25 terawatts is available here.

To maximize the output, I suggest a counter-current heat transfer system here ane here.

April 19, 2013    View Comment    

On Africa Aims to Combat Climate Change By Greening the Desert

Africa Aims to Combat Climate Change By Greening the Desert.

As does the Global Warming Mitigation Method.

April 18, 2013    View Comment    

On Climate Change and the Peak Oil Flip-Flop

What I mean.

See Prof. MacKay Sustainainable Energy -- without the hot air, refered to above.

Ocean thermal energy conversion 5W/m2.

World oceans 361 million km²

First law of thermodynamics: Heat and work are forms of energy transfer. Energy is invariably conserved, however the internal energy of a closed system may change as heat is transferred into or out of the system or work is done on or by the system.

 

April 16, 2013    View Comment    

On Climate Change and the Peak Oil Flip-Flop

Jim, the greenhouse in which we live is adding as much as 330 terawatts of heat to the oceans every year, NASA.

Converting half of this to productive use gets us twice the current rate of primary energy production.


April 15, 2013    View Comment