California's Energy Flow Diagram.
This comes from a paper on energy and water a few years back, but the diagram reflects the entire energy flow of the entire state after half a century of "by 'such and such' a date" legislation.
Environ. Sci. Technol., 2015, 49 (6), pp 3314–3321
Sometimes the state is described as a "renewable energy nirvana," but like most such nirvanas, it's just marketing.
Have a nice evening.
= new reply since forum marked as read
...you have certain thermodynamic misapprehensions, despite your witty restatement of the three main laws of thermodynamics, which wit aside, are a little misleading.
Let me see if I can improve your understanding of these laws a little bit, since any intelligent decision about energy necessarily involves an understanding of these incontrovertible laws, which - try as they might to do so, particularly in California - no legislature can repeal.
It's actually, ironically, an opportune time for me, since my kid is home from College for his winter break, and we've just received his textbook for one of the courses he'll be taking next semester - he's majoring in materials science engineering - this one: Thermodynamics of Materials I've been leafing through it for fun and also to get a feel about what he'll be learning and how he will understand this critical subject. (It's a pretty well written book by the way.)
Thermodynamics is, by the way, a difficult subject to understand on a profound level - at least it was for me - and thus it is easy to pull the thermodynamic wool over the public eyes to use a fun cliche.
You are incorrect when you write, "I am presuming that much of that is transmission losses," a statement that you advance to suggest that distributed energy is a good idea. Despite public enthusiasm for this idea, that distributed energy is a good idea, from a strictly environmental standpoint distributed energy is a terrible, awful, idea, and is, in my opinion, one of the worst, among many urban myths about energy. One reason that this is so is that distributed energy is distributed pollution, and the automobile, the invention of which was probably the world's largest environmental disasters in history - this applies to electric, gasoline, diesel and biofuel powered cars - is the world's largest distributed energy systems, obviating why distributed energy sucks. One can put a scrubber - at least in theory if not in practice - on a dangerous fossil fuel power plant, even a scrubber for the dangerous fossil fuel waste carbon dioxide, since the pollutant is in a large centralized area. The best one can do, by contrast, with a car is to add a catalyst, and catalysts, which in most places are only monitored periodically, can and do become inactivated.
The electric car, which is the subject of much public fantasy as being "green" is, in particular, a thermodynamic nightmare.
Transmission accounts, depending on the distance transported, for losses that amount to only a small portion of energy losses described in the chart. The overwhelming losses shown are second law losses, a result of the fact that California, pretty much like every other place on this planet, relies to an overwhelming extent on thermal power.
The concept of energy efficiency is often taught to undergraduates in terms of Carnot efficiency. There are many graphic evocations of Carnot efficiency all over the internet, this one - the first to pop on google - is pretty good and includes the famous efficiency equation:
The maximal amount of energy that one can obtain from a heat engine is known as the "exergy" but one will always lose energy to the environment as entropy, irrespective of how close one can to the total exergy possible in a system. Entropy can be a sort of gooey subject, but the most beautiful statement of it is Bolzmann's equation, which is inscribed on his tombstone constructed after his suicide:
S is the entropy, k is the Boltzmann constant - which has a habit of showing up in lots of places since is fundamental to the universe - and W is a number referring to the number of possible states a system can have on an atomic scale, generally a vast number. This is often described in public parlance as disorder, which in a sense it is, although this description is somewhat vague without an understanding of the statistical mechanics of gases, for example.
Now, as the other correspondent noted in response to your post, the efficiency of a system depends on the temperature gradient. This is why, if you look on some websites such as those of the EIA - which to my knowledge Trump and the Republicans, with their well known contempt for science, haven't destroyed yet - you will see power plants described as having "summer capacity" and "winter capacity." Thermal power plants are more efficient in winter because the temperatures of their surroundings are lower.
The other way to increase efficiency is to raise the temperature of the device.
The work extracted from a system is dependent on the path of the heat flows. This is why the differentials in thermodynamic equations have a funny looking symbol to evoke them, since they are not strictly immediately intergrable.
https://wikimedia.org/api/rest_v1/media/math/render/svg/a2b2ec583c3d49153ea73afaf917f6f4f542ce92
Most coal, nuclear and still the majority (I think) of gas plants have fairly low thermal efficiency, typically on the order of around 33%. The majority of them rely on the Rankine (steam) thermodynamic cycle which involves a phase transition, almost always of water commercially - although other fluids can and have been used - in which the liquid fluid is boiled and the vapor is allowed to expand against a turbine or piston. However one can recover more work by choosing another high temperature cycle that has become available because of advances in materials science, in particular the development of "superalloys" and thermal barrier coatings. This is the Brayton cycle. The Brayton cycle relies on simply heating a gas to raise its pressure and letting it expand against a turbine.
The most common Brayton cycle device is the jet engine. Jet engines all rely on superalloy materials.
Very modern and highly efficient gas plants are "combined cycle" plants which use both the Brayton and Rankine cycles, although despite their high thermodynamic efficiency are still extremely dangerous plants since they are permitted to dump their waste, carbon dioxide, directly into the planetary atmosphere. The first working fluid is the gas carbon dioxide, which has been heated to very high temperatures by its formation in a reaction to oxidize methane and other small alkanes in dangerous natural gas. It expands against a superalloy thermal barrier coated turbine, an exits, at temperatures far in excess of the boiling point of water, into a line where it is cooled by water which boils and is used to drive a steam turbine.
A clean option, as opposed to the unacceptably dirty option involving the dangerous fossil fuel "natural gas" is to use high temperature nuclear reactors, such as the "pebble bed" reactor you evoke. Another type of reactor of this type is the HTGC, high temperature gas cooled reactor, originally developed at General Atomics. Unfortunately, most of the high temperature nuclear reactors that have been built were economic failures - with the exception of the first nuclear reactor ever built, the Calder Hall reactor in Britain, a "Magnox" reactor in which the working fluid was carbon dioxide in a closed system, and which operated for more than half a century, albeit not without problems, and regrettably, because of materials science issues that were discovered after it went into operation at relatively low thermal efficiency.
A series of new players have been developed that also promise very high thermal efficiency, these are the liquid lead (or lead/bismuth eutectic) cooled reactors that are "breed and burn" reactors that are designed to never require refueling in their lifetimes. Companies working on these are Nuscale and Bill Gates' Terrapower. Another example are the MSR, molten salt reactors, which I studied a great deal many years back, and for which I had much enthusiasm, although I've changed my mind and no longer think they are the ideal type of nuclear reactors for reasons which will take too long to describe.
However, in theory nuclear power plants utilizing modern materials science can demonstrate previously unattainable thermodynamic efficiency by use - I believe - of a ternary combined cycle. In this scheme, steam (sometimes in the presence of waste carbon or biomass) can be utilized to generate hydrogen at very high temperatures (or also by thermochemical water splitting), the syn gas or hydrogen can expand against a turbine (Brayton) and ultimately boil water or another working fluid (Rankine). I suspect this kind of process, or related processes, might raise thermal efficiency closer to the pure exergy limit. I've thought a lot about this, and other people have as well.
A word about the efficiency of solar cells, which in my view are unacceptably dangerous, despite public enthusiasm for them.
They are not thermodynamically efficient, since they only capture a portion of the energy they receive. Depending on where one stands on the planet, the solar flux, insolation, is on the order of 1300 watts per square meter. There's a lot of hype about solar efficiency, much of it highly questionable, but typically the best of them operate at 20% efficiency. The usual response to this is "So what? Solar energy is 'free.'" This is a bullshit statement and is just one of the lies that drives this unfortunate scam, the other being reporting peak power as if it were average continuous power, which for the solar scam, involves typically very low capacity utilization, even before they get covered with dust and, in California recently, ash. Low efficiency is connected with the amount of surface area that solar cells must cover, the more surface area they are required to cover, the more habitat must be destroyed to install this crap, and worse, the more materials they demand for manufacture.
Were the solar industry ever to become significant - it won't, it will just soak up money for no useful purpose - another seldom discussed issue is the change in the planetary albedo. Solar cells are generally black, and thus they absorb light and discharge it as heat, just like a thermal system does. When this heat is released to the surroundings, it does not radiate into space transparently as white light does. This raises the temperature of the atmosphere. Fortunately the solar industry is and will always remain a trivial source of energy, but would be a real issue nonetheless.
Changes to the planetary albedo - derived from the melting of ice - is an important feedback loop in climate change. The solar industry did not work to slow climate change, it is not working to do so, and it will not work to do so.
A word on electric cars: Electric cars are extremely inefficient devices because they involve many thermodynamic energy losses because of the second law. The majority of electricity on this planet is generated using dangerous fossil fuels. Here is a list of the energy transformations involved, all of which are subject to the second law: Chemical energy (dangerous fossil fuels) is converted into thermal energy (steam), which is converted into mechanical energy (turbine) which is then converted to electrical energy (generator), transmitted with (minor) losses, then reconverted into chemical energy (the battery), then recovered to electrical energy, and then converted to mechanical energy.
This is not an efficient process. In places where electricity is particularly dirty, China for instance, it has been shown that the loss of life from electric cars is actually worse than the loss of life (in both cases to air pollution) than gasoline cars.
Electric Vehicles in China: Emissions and Health Impacts (Cherry et al Environ. Sci. Technol., 2012, 46 (4), pp 2018–2024)
In a gasoline or diesel car the transformations are dangerous fossil fuel (or biofuel) to thermal energy to mechanical energy, far fewer thermodynamic dependent processes, and therefore, almost always more efficient, which is not to say that I am fond of gasoline powered cars.
In my view, the cleanest possible car - if we must have cars - is a diesel powered car run on the wonder fuel dimethyl ether, which is, in fact accessible to nuclear energy, the cleanest possible primary energy source there is.
The enthusiasm for electric cars by "green" advocates is a highly dubious environmental undertaking in my view, and seriously needs to be carefully reconsidered.
Thank you for thinking. I hope this response has been useful to you, educational and will lead you to question your assumptions.
Have a nice day tomorrow.
I find this a bit easier to follow... though it's the same basic story of course. You can find this and other charts (for the whole US, other states...) at Livermore's energy flow chart site
