Ivanpah Solar Thermal Electrical Power Facility (Wikipedia)
I know that, just looking at the title of this argument, some people are already gathering up all their arguments why I'm wrong, foolish, and just don't get why solar can't work. Others of you might cheer, but not understand why I use the word "Revolution." I can tell you that it's a perfectly apt word, and there's no foolishness about it.
A caveat, however. People collectively known loosely as "Greens" have been touting solar power for decades, based the obvious fact that the sun's energy is free and, as long as you don't expose your skin too it for to long (the UV part of its spectrum is causing skin cancer rates to skyrocket), about as clean as you can get. You might even say, "It's natural," although that doesn't automatically make anything good.
My caveat for all who think that way is that, quite simply, you've been deluding yourselves. Free and essentially clean it may be, the sun's rays nevertheless have two staring-you-in-the-face disadvantages: first, it's quite dilute, providing only a maximum of about one kilowatt per square meter even when directly overhead (which it almost never is, so the average intensity is only about 200-300 watts of power per square meter, depending on latitude and climate); second, as everyone knows whether they think about it or not, you only get the energy during daytime, and even then it's often partly obscured by clouds and other atmospheric barriers. Oh, and there's a third: your electric washing machine will not work no matter how much sunshine you inundate it with.
No, it hasn't been a lack of political will, or the big, bad oil companies, or short-sighted politicians elected by ignorant voters, that kept solar out of the power mix for so long. Keep beating one side of your head until those delusions drain out of your ear like tepid bath water.
The real problem, until now, has simply been the lack of scientific and technical know-how to take our star's energy, concentrate it, and convert into electricity. But here is where we've been fortunate: the computer revolution over the last 30-40 years has pointed the way to effective solar to electricity conversion.
Before I elaborate on this, I have to point out that there are two different ways of harnessing the sun's energy to make electricity. One is shown in the picture above. The Ivanpah Solar Thermal (ST) plant provides, on average, about enough juice to service a quarter of a million homes or so. It does so when the sun is up by using vast arrays of mirrors to concentrate sunlight onto a molten salt container, which gets hot enough to generate the steam needed to turn the turbines and create the wonder of electric power. Now, since molten salt is a pretty good retainer of heat (even better materials are being developed), you can even get pretty good output from the plant at night and in inclement weather, to the extent this exists in the desert.
Solar Thermal, while workable under special conditions, has its drawbacks however. The Ivanpah plant cover about five square miles of desert, and that five square miles was no easy acquisition because a lot of study of the local ecologies of the region had to be made before it could be, barely, approved. Further, that quarter million households might sound impressive, but it's only a fair sized town. Imagine powering Los Angeles, or any major city, in this manner: you'd need ten to fifty times the area, and good luck getting that OK'ed after environmental studies are done. Then lets talk about an entire state, or part of a state, with several decent sized cities.
ST plants have these limitations, but again the big price is in construction, and Ivanpah needed 2.2 billion dollars to construct (with 1.6 billion being a government loan). Once in action though, that free solar energy means that, charging only 0.10$ per kilowatt-hour to those households, it should be pay off in (0.10 dollars X 24 hours/day X 365 days/year X 250,000 households = $220 million dollars a year => 10 years to pay off the costs. If the plant has a lifetime of 30-40 year, it could gross up to six or so billion, minus, of course, operation, maintenance, and repair costs (which, for five square miles, will amount to some serious change). So it really could work, if those costs are minimized. And if you could scale the whole operation up, say twenty times (a hundred square miles), Los Angeles might now have to rely on the Hoover Dam any more. At this point, it's still all a tad iffy, but plants like this, both smaller and larger, are being constructed all around the world. Improvements to Ivanpah include better heat storing substances than molten salt, and the ability to generate "super critical" steam which increases heat to electricity efficiency significantly. So it looks as though it is going to play a significant, albeit limited, role in solar's future.
Photovoltiacs -- the Real, Big-Time Player in Solar Power
I mentioned the computer revolution, but little of that has to do with ST. I'll move on now to photovoltaics, which involves the direct conversion of solar energy into electricity. I can't tout it without explaining it some, and the explanation involves some science you may not be familiar with, so I'll try to keep it simple without dumbing it down. Some materials, metals are the most obvious but not the only example, conduct electricity wonderfully. Why is this? As Wikipedia has a good article on this, I'll present part of it here for you. It has to do with conduction bands in the material:____________________________________________
(Wiki) The conduction band quantifies the range of energy required to free an electron from its bond to an atom. Once freed from this bond, the electron becomes a 'delocalized electron', moving freely within the atomic lattice of the material to which the atom belongs. Various materials may be classified by their band gap: this is defined as the difference between the valence and conduction bands.
- In non-conductors, commonly known as insulators, the conduction band is higher than that of the valence band, so it takes infeasibly high energies to delocalize their valence electrons. They are said to have a non-zero band gap.
- In semiconductors, the band gap is small. This explains why it takes a little energy (in the form of heat or light) to make semiconductors' electrons delocalize and conduct electricity, hence the name, semiconductor.
- In metals, the Fermi level is inside at least one band. These Fermi-level-crossing bands may be called conduction band, valence band, or something else depending on circumstance.
Electrons within the conduction band are mobile charge carriers in solids, responsible for conduction of electric currents in metals and other good electrical conductors.
The concept has wide applications in the solid-state physics field of semiconductors and insulators.
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Semiconductor band structure
See electrical conduction and semiconductor for a more detailed description of band structure.
In summary, in metals and other excellent conductors, the electrons are in bands about the atoms in their crystal arrangement. Most of the electrons are in filled, so-called valence bands, and being filled, cannot move under an electromotive force (like a turbine or a battery). But there is a low energy "conducting band" just above the highest valence band, so electrons can easily move into it, thus yielding a partially filled band where a force can make them move, in an electric current.
In an insulating material, either there is no atomic structure giving rise to these bands, or the conducting band is so high above the highest valence band that very few electrons even acquire the energy needed to reach them. There is a third category, however: semi-conducting materials. I suspect you've heard this word, particularly in the context of computers. Now you get the explanation of them: unlike conductors, where the conducting band is close enough to the valence band that electrons can easily partially fill it, and insulators, where the band gap is so great that essentially no electrons can make the leap, in semi-conductors the gap is just high enough for a decent energy jolt for electrons to make the crossing. In computers, semi-conductors lie at the heart of transistors, the basic gizmos (in the very old days, we used expensive things called vacuum tubes which had to be routinely changed at considerably nuisance) that give the computer its speed and capacity, if you can keep making them smaller and smaller, thus closer and closer, on an integrated circuit to communicate extremely rapidly. What has made the computer revolution possible is the exponential improvements in fabricating smaller and smaller transistors, with better and better semi-conductors, until -- well, until we now have computers that will comfortably sit on your lap which possess far more power and speed than their room-sized ancestors of only a couple of generations ago.
This exponential growth has been fueled by ever newer and newer improvements in materials science, and the chemistry and physics which underlay it. The advancement has been so profound, so rapid (it has been following Moore's Law, which keeps correctly predicting a doubling in computer speed and power every eighteen months or so) that there appears to be something of a positive feedback loop in progress here, in which each improvement lays the foundation for yet more of the same, all with no clear end in sight -- the precise definition of exponential growth, of which Moore's Law is one example in real life. The result is that way find ourselves in a position that even a generation ago would have been almost impossible to foresee. And it, more than anything else, has laid the groundwork for the solar energy revolution we are just beginning to enter.
In what way? Because the band gap in a semiconductor can now be tuned very precisely to match a specific wavelength of light, or even a significant part of the light spectrum. This means that solar energy shining on this semiconducting material can directly generate a current of electricity, with a certain voltage. Again, it wasn't as if the potential wasn't always there, it just needed sufficient STEM to become a practical reality -- and that probably wouldn't have happened without the computer revolution preceding it.
Now the idea of using semiconductors this way isn't new. But the scientific advances that are making it increasing practical and even compelling aren't stopping, or even slowing down. Starting with just 2-3% efficiency only some twenty years ago, solar PV efficiencies are now up to 15-20%, and climbing every year, while at the same time costs are plummeting. At this rate it won't be long before they reach the "theoretical" maximum of around 30%, and then some wise guy will figure out a way to overcome that too. But even at that thirty percent, it's well within the range of "ordinary" electricity producing plants (30-40%), and since solar cells and panels can be placed almost anywhere, the lack of long distance travel through transmission lines (which use high-voltage / relatively low-current AC to keep losses to a minimum) means even higher practical efficiencies -- if you decentralize the system, which I think is the best, even main, goal.
At this point, you should be about to say, "Wait a minute. Again, what about the storage problem you have, because the sun isn't always out and shining. I understand the solution for solar thermal, but if you want decentralized power, that's probably not going to work for local solar generators. You're going to need some kind of super battery. And just how many of these batteries do you think it will take to power NYC or Las Vegas at night? Well?"
Yes, yes, you're right. A different kind of storage capacity, chemical or otherwise, is probably needed for solar PVs. But be careful of a certain fallacy I have been encountering over and over again while perusing posts and blogs and comments. I call it the "The computer revolution never happened because its too expensive and too damn hard to keep replacing all those vacuum tubes constantly" fallacy.
I'll again use others' work to demonstrate what's actually happening in the real world:
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New Battery Material Could Help Wind and Solar Power Go Big
Low-cost materials could make storing hours of power from a wind farm economically feasible.
Utilities would love to be able to store the power that wind farms generate at night—when no one wants it—and use it when demand is high during the day. But conventional battery technology is so expensive that it only makes economic sense to store a few minutes of electricity, enough to smooth out a few fluctuations from gusts of wind.
Harvard University researchers say they’ve developed a new type of battery that could make it economical to store a couple of days of electricity from wind farms and other sources of power. The new battery, which is described in the journal Nature, is based on an organic molecule—called a quinone—that’s found in plants such as rhubarb and can be cheaply synthesized from crude oil. The molecules could reduce, by two-thirds, the cost of energy storage materials in a type of battery called a flow battery, which is particularly well suited to storing large amounts of energy.
If it solves the problem of the intermittency of power sources like wind and solar, the technology will make it possible to rely far more heavily on renewable energy. Such batteries could also reduce the number of power plants needed on the grid by allowing them to operate more efficiently, much the way a battery in a hybrid vehicle improves fuel economy.
In a flow battery, energy is stored in liquid form in large tanks. Such batteries have been around for decades, and are used in places like Japan to help manage the power grid, but they’re expensive—about $700 per kilowatt-hour of storage capacity, according to one estimate. To make storing hours of energy from wind farms economical, batteries need to cost just $100 per kilowatt-hour, according to the U.S. Department of Energy.
The energy storage materials account for only a fraction of a flow battery’s total cost. Vanadium, the material typically used now, costs about $80 per kilowatt-hour. But that’s high enough to make hitting the $100 target for the whole system impossible. Michael Aziz, a professor of materials and energy technologies at Harvard University who led the work, says the quinones will cut the energy storage material costs down to just $27 per kilowatt-hour. Together with other recent advances in bringing down the cost of the rest of the system, he says, this could put the DOE target in reach.
The Harvard work is the first time that researchers have demonstrated high-performance flow batteries that use organic molecules instead of the metal ions usually used. The quinones can be easily modified, which might make it possible to improve their performance and reduce costs more. “The options for metal ions were pretty well worked through,” Aziz says. “We’ve now introduced a vast new set of materials.”
After identifying quinones as potential energy storage molecules, the Harvard researchers used high-throughput screening techniques to sort through 10,000 variants, searching for ones that had all the right properties for a battery, such as the right voltage levels, the ability to withstand charging and discharging, and the ability to be dissolved in water so they could be stored in liquid tanks.
The Harvard researchers are working with the startup Sustainable Innovations to develop a horse-trailer sized battery that can be used to store power from solar panels on commercial buildings.
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See what I mean? I could go gallivanting about the Web, gathering more data for the solution of solar PV energy storage, but this one example should suffice. We've are making great progress, have been making great progress, and will continue to make great progress. By great, I mean computer revolution great, for it is all still founded on materials sciences, and an enormous body of knowledge is already available thanks to computers.
The computer revolution, to date at least, has taken some two generations to reach where it is today. I see no reason, either in principle or in practice, why the solar energy revolution can't race along the same curve.
