A Nice Paper Analyzing Heat Exchange Networks for the Utilization of Waste Heat for Desalination.

[NNadir]

Despite much nonsensical wishful and often delusional thinking about the ersatz "triumph" so called "renewable energy," as of 2017 - as was the case in 2007, 1997, 1987, 1977...and so on - almost all of the world's energy is supplied by heat engines of various types, The fastest growing form of energy (as opposed to peak capacity on a sunny or windy day) is the dangerous fossil fuel natural gas which is, so far as power plants and vehicles is concerned, is utilized in heat engines.

The failed and expensive so called "renewable energy" industry - which is neither sustainable or, in fact, renewable, is nothing more than lipstick on the natural gas pig, as is readily seen simply by looking at the rate at which the dangerous fossil fuel waste carbon dioxide is accumulating in the atmosphere, currently the fastest rate ever observed, roughly 3.00 ppm per year.

The second law of thermodynamics, which cannot be repealed by any governmental organization or by scientifically illiterate claptrap put out by say, Greenpeace (or any other NGO), requires that heat engines must waste some energy as heat. The total amount of exergy - useful work - extracted by a heat engine can never equal the heat generated in the combustion of dangerous fossil fuels or dangerous biomass combustion. The ratio of the exergy to the heat output of the fuel is termed the "efficiency" of a system.

In 2004, a famous paper by Socolow and Pacala, two scientists at Princeton University, postulated that the "switch" from coal to high efficiency natural gas would stabilize the climate. Events, the concentration of carbon dioxide in the atmosphere, has shown that this hypothesis was not borne out by experiment, since the overwhelmingly largest source of new electrical energy generation on this planet is natural gas. Experiment, um - excuse the word - trumps theory.

Nevertheless, in general, the most efficient heat engines on the planet are, in fact, dangerous natural gas plants (along with some pilot demonstrator coal plants) known as "combined cycle" power plants, which have a brayton cycle (very high temperature) gas turbine in which the rejected heat is used to boil water to drive a steam turbine (rankine cycle). These plants can operate in excess of 50% thermal efficiency - even close to 60% - in the generation of electricity.

The higher the temperature at which a system can operate, the greater the efficiency it can realize. Combined cycle plants are only now possible because of developments in materials science, in particular the development of "super alloys" and thermal barrier coatings - generally ceramics - with which these alloys can be coated.

It is worth noting that combined cycles need not be limited to Brayton systems coupled to Rankine systems: It is possible to couple them to a third type of device, a high temperature thermal reformer which provides chemical energy. (Ideally such systems would be driven by nuclear heat.)

The problem with waste heat is that is has to go somewhere, and that "somewhere" is often a body of water. This is a big problem whenever the water in question is fresh water, since it is evaporated in the process, leaving the water unavailable for other uses, such as irrigation or residential or commercial water supplies.

However, since waste heat drives the evaporation of water, it can also be utilized to purify water, in particular, seawater. This process as described is just "distillation" but distillation is actually only one of the ways that waste heat can be utilized to desalinate water. There are a large number of processes other than simple distillation that can be utilized, for example flash distillation at low pressure, reverse osmosis driven by pressure gradients resulting from water expansion (or electrical power), multiple-effect distillation in which a linked series of heat exchangers evaporate and condense water in series with each distillation unit driven partially be waste heat from the previous system.

These types of systems are not new, and they are not exotic. The Diablo Canyon Nuclear Plant in California for instance, uses fresh water for cooling, and has always utilized fresh water for cooling, and all of the fresh water - some of the purest in the State of California has been obtained by desalination of seawater at this plant. Originally this desalination was performed by flash distillation using reduced pressure and waste heat, although materials science at the time of the building of the plant was relatively primitive, and corrosion in the heat exchangers lead to the replacement of the flash system with reverse osmosis systems. (There were plans to expand the water desalination capacity at the plant, but the decision was made to kill people by shutting the plant because of appeals to stupidity: Nuclear power plants save lives.)

Prevented Mortality and Greenhouse Gas Emissions from Historical and Projected Nuclear Power (Environ. Sci. Technol., 2013, 47 (9), pp 4889–4895)

Thus the desalination capacity will not be expanded.

In any case, advances in materials science have allowed new technologies for desalination to be realized and a very nice paper in one of my favorite scientific journals, Industrial & Engineering Chemistry Research evaluates the economics of utilizing waste heat to desalinate water, regrettably focusing on dangerous fossil fuel plants, dangerous biomass plants and useless and expensive solar thermal plants - which in every single case morph into dangerous natural gas plants when their economics belie the wasteful hype that caused them to be built is exposed as flawed. Despite this flaw in evaluating these types of plants, there is no reason that the same evaluation could not be applied to more sustainable, if unpopular, nuclear plants.

The paper is here: Optimal Design of Water Desalination Systems Involving Waste Heat Recovery (Ramón González-Bravo†, José María Ponce-Ortega*† , and Mahmoud M. El-Halwagi, Ind. Eng. Chem. Res., 2017, 56 (7), pp 1834–1847) If you are able to access the paper in a good scientific library you will see a lot of math directed at calculating the economics of various approaches for model systems operating in the State of Sonora in Mexico, analyzing the profit from power generation and water sales.

Water in that region is fossil water. The dire situation is described in the paper's text:

In this paper, the problem of overexploitation of water in the region of Costa de Hermosillo (CH) in the state of Sonora in Mexico was selected as a case study. The CH is one of the most overexploited aquifers of Mexico; the volume of water extracted is used mainly for crops with high water consumption.23 The volume of water is mainly used for agricultural purposes in the irrigation district “051 Costa de Hermosillo” (ID051). TheID051 has an annual water extraction of 461 hm3, an estimated natural recharge between 250 and 320 hm3 per year, and an annual seawater recharge of 98.4 hm3, which has caused serious salt pollution of the water.24 The energy sector in this regionals represents a challenge because it is located near to the Sonoran Desert, where the energy consumption increases in the warmer months due to the use of cooling systems.

In any case, for the model system, the most profitable network is found to be a multiple effect distillation system (described above) coupled to a thermal membrane distillation system, which would generate about 154M USD of power, 26M USD of water while generating a profit of roughly 110 USD while creating over 1000 jobs. For the system described about 8.7 million tons of the dangerous fossil fuel waste carbon dioxide would be released into the atmosphere. (See table 3 in the original paper, page 1844).

Were the plant nuclear powered, there would be very little carbon dioxide involved at all.

Thermal membrane distillation systems are described in an earlier paper in the same journal, this one: Integration Design of Heat Exchanger Networks into Membrane Distillation Systems to Save Energy (Yanyue Lu†‡ and Junghui Chen†* Ind. Eng. Chem. Res., 2012, 51 (19), pp 6798–6810)

Text from that paper describes the technology:

Membrane distillation is a thermal-driven process. The transmembrane vapor pressure difference, which is generated because of the temperature difference between the hot feed stream and the coolant stream, is the driving force of vapor through the microporous membrane. For this reason, the high thermal energy consumption becomes one of the main barriers of MD to realize common commercial application. In the field of pure water production, the comparison of several desalination technologies shows that the cost of pure water produced by reverse osmosis (RO) is the least; however, if the low grade energy sources, such as the waste heat and the solar energy, are used in the MD process, the expected cost for the MD process will become more competitive than RO.12

It should be noted that no desalination system, even a nuclear powered system, is entirely environmentally benign, chiefly because there is a need to dispose of the brine resulting from the recovery of water. Depending on the ecosystem into which the brine is discharged, the consequences can have fairly severe effects. (cf Brine Discharge: One Size Does Not Fit All Environ. Sci. Technol. Lett., 2017, 4 (7), pp 256–257)

Nonetheless, like many other resources, fresh water, as is the case in the Mexican State of Sonora, is a stressed resource, and there is no ideal solution to this very challenging problem.

It is not the case that in our desire to resist Trump that we forget the basic problems that need to be addressed and which he and is enablers are incompetent to address and, frankly too ignorant to address.

Have a nice week.

[tonyt53]

1. As a mechanical engineer, who has worked with alternative and renewables for years, I see an issue

Us that work in the industry that I mentioned, have a good understanding that natural gas is merely a transition medium. Also, the salts recovered during desalination, could actually be used as molten salts, which hold great potential for energy storage. Saltwater contains varying levels of multiple salts. Even simple table salt becomes molten at about 1500F.

What is the most striking omission in the article, is that while it touts nuclear energy, it fails to mention what happens to the spent fuel. To refer to a nuclear system as "benign" makes one wonder who paid for the research for the article.

There is no perfect energy solution now. Even solar and wind require great amounts of energy to produce the materials. However, as with natural gas, they sure neat the hell out of coal and oil. They are a bridge that helps us across the stream as we build a bridge across the river.

[NNadir]

2. Natural gas is NOT "transitional." That is a bald faced lie. I note that unlike spent fossil...

...fossil fuels which are dumped indiscriminately into the atmosphere with no rational or reasonable approach to managing them, used nuclear fuel can be - as been experimentally observed for more than half a century - be kept on the site where it is generated without killing anyone other than the people it kills when people burn gas to complain about it on the internet.

I have been studying the chemistry and physics of used nuclear fuel for over 30 years in the primary scientific literature, and while it is true that I started the exercise when I was an anti-nuclear idiot, I have come to the conclusion that the selective attention applied to the risks of nuclear energy are far more toxic than nuclear power has ever been or ever will be.

Natural gas explosions, the disgusting residue of fracking being dumped on all future generations is a crime against all future generations, as is, frankly, all anti-nuclear rhetoric.

Last year, and every damned year before that, air pollution killed close to seven million people.

A comparative risk assessment of burden of disease and injury attributable to 67 risk factors and risk factor clusters in 21 regions, 1990–2010: a systematic analysis for the Global Burden of Disease Study 2010 (Lancet 2012, 380, 2224–60: For air pollution mortality figures see Table 3, page 2238 and the text on page 2240.)

That there are people on this planet who ignore the deaths of 70 million people - more than were killed in World War II - every decade is disgusting beyond belief, at least in my opinion.

The world just squandered two trillion dollars in just ten years on so called "renewable energy" or "alternative energy" and combined, solar and wind do not produce even 5 of the 570 exajoules of energy consumed each year.

Now, I often encounter people who assume that anyone who takes an ethical position in support of future generations via nuclear energy must be paid off. This says more about them than it says about me; they think that money and only money counts, that the only reason that anyone does anything is for money. Believing this is evidence of having a withered sense of values.

And let me be clear on something, my position here is entirely and wholly ethical and I'm not interested in the rhetoric of bean counting materialist bullshit artists who wish to claim otherwise. I invested a lot of time to fully explicate my moral position elsewhere: Current Energy Demand; Ethical Energy Demand; Depleted Uranium and the Centuries to Come

One participant in this conversation of course, is as stated at the outset making money off of an energy scheme; one that has clearly not worked, is not working, and will not work: So called "Alternative energy."

How do we know it's not working? Because we surged past 400 ppm of dangerous fossil fuel waste in the atmosphere in the last two years and no one now living will ever see a value anywhere on this planet that will ever again be lower. In 2015 and 2016, for the first time in observable history the annual increase was at 3.00 ppm per year.

I consider the specious selective attention rhetoric directed against nuclear energy to be a crime against all future generations. The cited paper in the OP from one of the world's most important climate scientists, Jim Hansen, certainly supports this view.

Nuclear power need not be perfect, it need not be without risk to be vastly superior to everything else. It only needs to be vastly superior to everything else, which it is.

My son has just entered a fine university (on a nearly full scholarship) to study materials science engineering. I hope, I pray, that unlike some of the engineers one hears from, he will be competent to address, and informed about, the absolutely critical engineering issues before humanity, and would never embrace the fantasy that dangerous natural gas - which has killed far more people in the last ten years than nuclear killed in the last half a century - is a "transitional" fuel. That's garbage, extremely dangerous garbage. Natural gas is nothing more than a disastrous scheme to squeeze the last molecule of carbon dioxide into the atmosphere that can be squeezed into it before the planet wholly and completely collapses.

Have a nice week.

[tonyt53]

3. That is your opinion, and you can have it.

To us already working in alternatives, we recognize that natural gas IS most certainly a transitional fuel. In the meantime, work will continue on clean energy production, AND the oil-fired and coal-fired generation units are going away.

No nuclear power is not the answer. When it costs ten times what a similarly MW sized coal-fired unit with the most modern emission controls costs, does that make sense? How about the timeframe to build a nuclear power plant? Three to four times the construction time of a coal-fired plant of similar size. When the cost of solar and wind are dropping significantly, does it make sense to build a nuclear power plant? Finally, do you want the spent fuel to be stored in your backyard?

If there was a magic wand that we could wave and we would have clean fuel forever, it would happen. but in the meantime, we have to be realistic. The steam engine was built well before somebody decided to couple it with wheels and make a train.

Nuclear power plants are not the answer now and they won't be in the future. You can have your moral standing, just don't expect others to fall in line with you when it comes to nuclear power. I sure as hell won't.

[hunter]

4. Fuck "natural" gas. It will be the end of this world civilization 1.0

"Better than coal" is not good enough, especially as it becomes apparent we have a century of gas "reserves."

These reserves will kill us.

[tonyt53]

6. We have 200 years of coal reserves, and how is coal doing? Alternatives and renewables are growing.

[NNadir]

8. All the so called "renewables" ever built in half a century of mindless cheering do not equal...

....the annual growth in the use of dangerous natural gas. Again, after the expenditure of two trillion dollars in ten years, solar and wind combined don't produce 5 exajoules.

The natural gas industry gets away with using so called "renewables" as a fig leaf for its criminal intent to dump unlimited quantities of waste in the atmosphere.

In my experience there are zero advocates of squandering the world's resources on the toxic so called "renewables" industry who aren't apologists for dangerous fossil fuels.

History will not, and should not forgive this crime against the future, should history survive.

If you must know how coal is doing, you could look up something called "data" which is all over the internet and in the scientific literature. The coal industry in 2017 dwarfs the coal industry in 2000.

It's a very, very, very provincial view point that coal is dying. It's not. It is still responsible for a huge fraction of the world's energy, although the scheme to burn every last molecule of methane and dump the waste in the atmosphere is also moving forward.

Anyone who claims that so called "renewables" is an alternative to gas or coal is simply grotesquely uninformed, lazy, or venal, possibly all three.

[tonyt53]

9. Your last sentence says it all - you are a mouthpiece for nuclear power and nothing else.

Hell, nobody that I know refers to natural gas as a "renewable fuel". Your words tell the truth about your agenda - it is nukes of nothing. Sorry, but it is nothing then. NOBODY is going to pay for them and NOBODY wants the spent fuel in their backyard.

By the way, exactly what is your experience? Not reading something on the internet, but your real professional experience. What world's resource are being squandered on renewables? Fact is, people such as yourself have no real ideas. You just want to push your own agenda on everyone else - and that agenda creates more problems than already exist. Nuclear power is not by any means an answer - long term or short term. You are worse off than uninformed, lazy, or venal; you are a fool.

[NNadir]

10. Actually, I am a person with 30 years of experience in reading the primary scientific literature...

Last edited Tue Aug 29, 2017, 04:04 PM - Edit history (2)

...on energy and the environment.

I have already stated my moral view of people who claim that the only reason that anyone does anything is for money. Again, their venal and materialist view point says more about them than it does about me.

I am tired and rather angry at people who know nothing at all about nuclear energy but hate it anyway. Given the clear evidence in the references provided above that nuclear energy saves lives, I regard this viewpoint as dangerous, and frankly, criminal, and I will never apologize for stating it in obvious terms.

Climate change is an extremely dangerous state of affairs, and anyone so clueless as to suggest that the huge and useless investment in so called renewable energy has done anything to address climate change is simply not looking at the data, which any fool can read. Carbon dioxide increases in 2015 and 2016 totaled 6.00 ppm, completely unprecedented.

So much for the tired decades old pablum that "renewable energy" is growing. It has not, is not, and will not grow as fast as dangerous fossil fuels.

Anyone can learn this with simple research, if not from the primary scientific literature, as referenced in the OP, from readily available information in the public domain.

Frankly, rather than engage these people producing this dangerous pablum year after year decade beyond decade, and in recognition of the fact that they anger me beyond words, I have chosen to uitlize my "ignore" list on this website where they are concerned. Welcome to it.

Have a nice life.

[tonyt53]

11. Reading??? I've lived it for well over 40 years since I graduated college.

[hunter]

5. I don't have access right away to the paper you cite...

... but I've been paying attention to "forward osmosis" projects that are able to use "waste" heat.

As I recall, Yale researchers are looking at Ammonium Carbonate forward osmosis cycles.

[NNadir]

7. There are actually lots of schemes for using waste heat for water treatment.

There's a whole journal called Desalination. I don't read it regularly, but I stumble on it from time to time.

Salt gradients are actually stored energy, and one can in theory (and certainly at lab scale) generate currents by utilizing them.

My interest in the article in the OP - in a journal whose table of contents I go through every issue - was driven by my interest in what may be ungenerously be called "Rube Goldberg" schemes for very high recovery of exergy. I often dream about these kinds of networks of heat flows and transfer to do work, if not mechanical work, chemical work.

Although I do always keep Jevon's paradox in the back of my mind, I do believe that efficiency matters, and matters a great deal from a purely environmental standpoint.