Wednesday, August 13, 2014

Department of (Zero Total) Energy

I think that we have to seriously consider the idea that the total energy content of the universe is zero. (While experimentally proving that it is exactly zero before inflation is nearly impossible, data coming from multiple data sets is all leading to the same conclusion: that the total energy content of the universe post-inflation is nearly zero and remains nearly zero throughout the rest of the history of the universe.) The image below show an possible energy content of the universe throughout its history (for a set of parameters close to today's values...expect for the radiation...which was make larger in order to make it easier to see. Note that this graph is from lecture#12 from Dr. Mark Whittle's Great Courses series titled Cosmology. I highly recommend watching it. It's infinitely better than the two Great Courses series by Dr. Sean Carroll.)


In the figure above, the kinetic energy (yellow) plus the gravitational energy (white) sum together to a value of zero (red) through time (x-axis.)

But wait a second. If the total energy content is and always will be zero, why do we say that there's an energy crisis? If the total energy content is zero and constant. How could there be a crisis?
Are millions of people worrying about a crisis that doesn't exist?


It's important here to remember that we don't face a crisis as far as the 1st Law of Thermodynamics goes. We've known for centuries that the total energy of the universe is constant (i.e. the first law of Thermo.) But we've also known for awhile that the entropy of the universe is increasing with time (i.e. the second law of thermo.) The "missing information" (i.e. entropy) increases with time, and hence the "available pool of useful work to generate information" (i.e. exergy) in the universe decreases with time.

This 2nd Law increase in entropy in the universe and hence decrease in "available pool of useful work to generate information" (i.e. exergy) is much closer to what normal people mean when they say that there's an energy crisis. But still, this is not exactly what people mean by an "energy crisis." I don't think that the average citizen is worried about the entropy generation (and hence exergy decrease) that is occurring right now in the center of virtually ever galaxy in the galaxy when a black hole consumes nearby gas and turns high quality energy (i.e. the rest mass of the gas) into low quality energy (i.e photons and neutrinos.) The exergy destruction inside of a black hole completely dwarfs the exergy destruction at power plants on Earth.

So what is it exactly that worries people in developed countries? I think what worries many people in developed countries is that the growth rate of useful work seems to be dropping and that the generation of useful work seems to be causing serious long-term damage to the ecosystems on our planet. But how does this relate back to the 1st or 2nd Laws of thermodynamics?

Well, clearly the crisis I mentioned above has nothing to do with the 1st Law of Thermodynamics. (Total energy is nearly zero and remains constant with time.) The "crisis" is a real one, but it's not completely related to the 2nd Law of Thermodynamics either. While "missing information" has been and will increase for quite while, the question is: what is happening to our total information content?

Generating information from useful work is not limited by the 1st or 2nd Laws of Thermodynamics. Once you have "near pure forms of useful work" such as stored electricity, then that stored electricity can be converted into information in a one-to-one correspondence between the quanta of useful work into bits of information.

However, if we took all of our currently stored useful work (such as stored electricity) and converted it into information, then we would have briefly generated a lot of information. (Image throwing our entire World GDP into building the successor to the LHC at CERN. We would be able to generate a lot of useful information fairly quickly. However, that would be it. Once we consumed all of our stored useful work, then that would be it.)
The key to growing the amount of information is to find the optimal balance between (1) the growth of useful work, (2) the generation of new information, and equally important (3) the avoidance of environmental or societal damage from (1) and (2). What I'm trying to point out in item(3) is that we need to avoid or constrain those processes in (1) and (2) that in the short term appear to increase (1) or (2), but in the long run end up decreasing (1) or (2) because of their environmental or societal impact.  (Specifically, what I mean here is that the long-term damage from greenhouse gas emissions from power plants, cars, factories, etc... could end up leading to severe loss of information (i.e. destruction of ecosystems) and severe decrease in the growth of useful work (i.e. so much useful work will be spent on "adaptation" that it would have been better to have never built the GHG-emitting power plant in the first place.)

So, let me step back and re-iterate what I've stating above:
(a) The crisis we face has nothing to do with the First Law of Thermodynamics.
(b) The crisis we face is only somewhat related to the Second Law of Thermodynamics. (Yes, the exergy of the universe is decreasing and this shows up as a decrease in the quality of available exergy sources here on Earth. However, this decrease in the quality of available exergy has been occurring throughout human history. China already mined all of the easy to reach coal a thousand years ago, and all of the easy to drill oil in Pennsylvania was consumed a century ago. So, we can't explain our "crisis" just using the 2nd Law of Thermo.)
(c) The crisis we face is a crisis of biology and economics, not physics. It's a crisis of how best to balance (1) growing the supply stored useful work (i.e. growing work), (2) generating new information, and (3) environmental and societal stewardship. This is an on-going "crisis" that will remain with us until there is no exergy left to consume.

So, let me tie this together and relate it back to the title of this post. The US Department of Energy is misnamed (just like many other governmental "Energy Departments" across the globe.) It might as well be named the "Department of Zero Total Energy" because we don't face an Energy Crisis.
But the Department of Energy has crucial role to play in addressing (1), (2) and (3). The Department of Energy currently is conducting research into how to generate electricity and drive cars without generating GHG emissions, and it is also generating useful information by funding basic science. (Note that I'll wait for a later post to discuss whether some or all of the functions of the Department of Energy would be best left for the private sector to do. This is an interesting and complex question, but it deserves an entire post.)

The problem is that the term "Energy" no longer means (to many scientists) what it originally meant. For example, the word "Energy" is a noun waiting for an adjective in front of it, such as  "Total Energy", "Kinetic Energy", "Gravitational  Potential Energy, " etc...
Worse, in the era after Einstein, we now know that what we previously meant by energy is just one term in a 4by4 matrix which is called the "Energy-Momentum Tensor." As such, the term energy no longer means what it used to mean a century ago. The term today that better describes what we used to mean by energy is "exergy." As such, it might be better to change the name from the Department of Energy to the Department of Exergy. However, the current purpose of the Department of Energy is much more than just to find Exergy. It's about finding exergy and converting it into useful work in an environmentally sustainable manner, and also about turning some of the useful work the US generates into new, useful knowledge (i.e. basic and applied science.)

So, while I'm in favor of changing the name of the Department of Energy into the Department of Exergy, I recognize that there's no way to describe in one word crisis we face or the Department that is supposed to solve that crisis. We face the crisis that every species faces: how best to balance growth, new information generation, and environmental stewardship.

No comments:

Post a Comment