Empty Energy Promises is a series of posts over the next couple of month which will look into the claims of some of some of the most hyped technologies and energy sources, and ask whether in reality, they have any real chance of living up to what they are being hailed as. This is not an anti-environmental posting, but quite the opposite. It’s the view of Depleted Cranium that pouring money and resources into energy sources which do not have a real chance of being a workable solution to enviornmental and energy needs is counter-productive and does nothing to help the environment. Sometimes what you hope for and the truth are not the same.
In the past twenty to thirty years, literally billions of dollars have been spent on research and development of solar energy as a viable form of usable utility-level electricity. Many are convinced that solar energy is the key to the future energy needs of man. Installation of solar panels on homes and business is being promoted by many, with claims that the panels can pay for themselves in just a few years. While this may be true for the property owner, this is mostly due to massive government subsidies for the use of solar energy.
In the US alone, generous tax breaks, energy vouchers and other government programs designed to promote solar energy have spent untold billions of dollars. Solar power stations in the US, Spain and Germany have been built at costs of hundreds of millions of dollars each, despite being of rather modest generation capacity, by grid standards. Despite this truly massive expenditure of funds and resources only a tiny fraction of a percentage of electricity comes from solar energy. And the rapid growth of solar, relatively speaking, has been puny compared to the rate at which coal-burning power plants are being built.
This chart shows power generation sources for the US in 2005. Where’s solar? It’s lumped in with
“other” along with waste-heat-recovery, wind, biomass, dump gas recovery and other methods. The
actual portion of energy generated is around .011%-.034%or so, depending on how it’s counted
(on grid capacity, total capacity, total operating capacity, etc.) Chart source
But why? What is wrong with this picture? Why is it that solar energy seems to be relegated to remote sites and satellites and space stations? There is a limiting factor of solar energy, and there is no way around it. Quite simply: a given amount of solar panels doesn’t give you that much power. And it never will be able to. This is because light, even on a bright sunny day, only contains a relatively small amount of energy. The energy which the sun illuminating a one square foot patch on a sunny day might be a few watts, at the very most. That’s under the best of conditions. And conditions are very rarely that good. Solar energy produces no energy at night, little energy at dawn and dusk and less on cloudy days.
Combine this with the fact that even the best systems now are only about 40% efficient, and most are less than 30% and it becomes apparent that it’s a loosing battle. Even if, in theory, 100% efficiency conversion method were discovered, and even if solar costs could be cut by 75%, the power density is so low, that the sheer amount of land needed, the maintenance of the facilities, the fact that solar cells degrade after a decade or so, the cost of installation and other incidental expenses means that solar energy is likely to remain one of the most expensive and impractical means of generating electricity.
This is not to say it does not have it’s place. For satellite and space probes, which bask in the high intensity of the sun’s direct rays nearly continuously, solar energy is ideal. For powering remote motoring stations, communications relays or for failsafe energy for emergency equipment, solar is a natural choice. And for homes and businesses, solar water heating panels are a great way to take some of the load off of heating off of furnaces or water heaters.
Solar power generation schemes can be broken up into two basic types: Photovoltaic and thermal.
These are the well known panels which you see on emergency road-side phones, calculators and satellites. In some applications they work great. For remote locations that need a source of energy that does not require refueling, or for space flight, where highly intense sunlight is nearly constant, they can be the best choice. But can they really be a major source of power for the electrical grid? There are some major shortcomings of the technology which make it a very poor choice for major energy needs.
Expensive – Even though a single solar cell might not seem like it is that costly, outfitting a building with them can cost many thousands, even to produce a small fraction of the structures power needs. And although many will claim government subsidies and tax breaks can counteract the cost, this does not actually make them more economically feasible, it just means that the end user does not always foot the whole bill. Solar cells are, when it comes down to it, semiconductor devices, and large arrays of them are simply not cheap.
Require Huge Amounts of Space – The best solar cells are, right now, about 30% efficient, and experimental prototypes have pushed 40% efficiency in converting light to electricity. But even at such high efficiencies, covering the roof of the average home would only be enough to cover basic energy needs when the sun is shining and few appliances are running. Turn on the air conditioner, the lights and the washing machine, and you’ll be pushing the limits of the available power. Even with batteries for surge needs, it’s not likely that you could ever power a house on solar energy without some very drastic cuts in energy usage, such as no electric oven, only a tiny television, a high efficiency laptop computer and small LED lights. Either that, or you will need massive amounts of realestate.
Non-Constant Power – The most obvious problem is that they simply do not produce energy when you need it. Rather, energy comes when the sun is out. If it’s overcast or night, you have no energy. Thus, the energy needs to be stored somehow. Either that, or have another source of energy when solar is not available. Both have issues. Using batteries, hydrogen or pumped water storage, huge amounts of energy are lost to the inherent inefficiency of the storage medium. Hydroelectric dams can be opened, coal fired plants can be put online when needed and nuclear reactors have variable thermal outputs, so most energy sources can be made available when needed. But not solar. If there is a huge need for power and it’s night, you have a problem. If it’s a sunny day and there is little demand, you could have a surplus, if the grid uses solar as a major power source.
Low Voltage DC Power – Solar cells produce DC electricity, but the power grid uses AC. In order to convert the DC to AC current requires a process called inversion. This process is somewhat lossy and as much as 25% of the energy can be lost to heat in the process of converting it to AC. But it gets worse: the voltage produced by solar cells varies greatly, depending on the intensity of the light. This needs to be compensated for and the regulation process can produce even more energy loss.
It’s important for the power grid to have reliable and stable power. If solar energy were to become a major part of the power grid’s generating capacity, it would make it difficult to ensure that there is always enough power to meet needs and that spontaneous brownouts do not occur if a freak thunderstorm should block out the sun.
Simply put, it just is not practical as a means of generating electricity for general purpose fixed sites and power grid usage. The amount of cells needed and their inconsistent output precludes it from ever being more than a very small portion of energy production. Even if price could be reduced to less than 10% of what it is now, it simply is, to put it bluntly: never going to happen.
Just look at one example of an attempt to produce a solar photovoltaic power plant:
Largest Single photovoltaic station under operation/construction:
Waldpolenz Solar Park – Leipzig, Germany
Maximum Power output – 40 Megawatts (under optimal conditions)
Expected Annual Energy Output: 40,000MWh
Average Power Output: Approximately 4.5 megawatts*
Land Used: 220 hectares / 543 acres / approximately .85 square miles
Cost: Approximately 130-160 million euros, projected. Or about a quarter of a billion US dollars.
*The amount of power output by the plant, ranges from as much as 40 megawatts down to approximately zero at night. The the total energy generated in a year is equivalent to the plant operating continuously at 4.5 megawatts.
The other major form of solar energy for electricity is Solar Thermal:
Basically this approach concentrates sun light in order to heat a fluid or other medium and then drive a sterling engine, steam engine or some other sort of thermal engine. It’s somewhat comparable to the solar water panels on homes, which preheat water to help reduce the energy used by a water heater. However, to effectively produce electricity requires much greater temperatures than such panels.
This can take the form of either troughs of parabolic mirrors to collect light, or a “power tower” design, in which tracking mirrors move with the sun and reflect it toward a central heat collector. One major advantage of these systems is that they can retain heat for some period of time, allowing power to not be entirely limited to times of good sunlight, but also be stored for a short time after.
Unfortunately, such systems are really only suited to areas with a lot of direct sunlight, such as deserts. And the cost to energy ratio is not that much better than photovoltaics.
Here are a few examples:
“Nevada Solar One” is one of the latest attempts using a “Trough” design. It should become operational in a few years.
It is currently under construction.
Maximum Power Output- 64 Megawatts (summer, Daytime)
Average Power Output – Unknown. Estimated around 30-50 Megawatts
Land used: Approximately 250 acres for collectors.
Cost: Proposed at roughly $240 million. New estimates may be as much as a half billion dollars!
The system involves pumping fluid through piping to be heated by the solar mirrors and then collected and used to power a thermal engine. Unfortunately it seems this may have issues with leaks and need for maintenance and operating costs.
“Solar Two” is one of two experimental solar “Power Towers” which the United States DOE constructed. Each uses hundreds of mirrors pointed at a tower, which contains a system of molten salts and heat exchangers which can power a thermal engine. In experiments, the system proved capable of producing approximately 30 megawatts. However, only 10 megawatts could be produced continuously and reliably. Over a billion dollars have been spent on research and construction of solar thermal systems in Mojave desert of the US. It also takes up a considerable amount of space. The mirrors alone take up about 30 acres.
(Notice from the construction crane. This thing is quite huge)
The first fully-operational, grid-power system is scheduled to be built in Spain within the next few years. It will be larger than the Solar Project prototype systems built in the US and will have up to 2493 highly reflective mirrors, mounted on a complex system of gimbals and actuators, in order to focus the sun as it moves.
The system, dubbed Solar Tres, is expected to produce 15 megawatts continuously and will cost a projected 100 million US Dollars.
What does a solar car look like?
Okay, but how long until they get it so that regular sized and shaped cars can be powered by solar energy?
It simply cannot happen. The car shown above hardly qualifies as a “car” it’s high efficiency electric motors drive at a reasonable pace, but it’s occupant sits in a tiny, unairconditioned seat, in a tiny, ultralight weight car, made of flimsy materials, with no radio, no power steering, not even power breaks. It is designed for absolute efficiency and covered with highly efficient solar cells. Even so, it does not even have enough spare power for blinkers, and it must be followed by a safety vehicle.
The reason it will never be a full sized car? If you covered every inch of a car with solar cells, you would simply not be able to get enough energy from light to propel and operate the car. Even if the solar cells were nearly 100% efficient. And forget about A/C, power windows, radio or anything else. There is a certain amount of energy which is required to move a vehicle over hills, against air and to accelerate to a reasonable speed from a stop. And the amount of light which falls on the surface of a vehicle contains nowhere near that energy. You can’t break the laws of physics.
Solar energy has an important place for certain tasks. For operating remote sensors or equipment that cannot be accessed and is away from power sources; for providing energy to space probes and satellites; for redundant power for low-consumption items, solar is a natural choice. But for a major source of grid electricity? It is unlikely that the issues inherent to solar energy will ever allow it to be economical or practical for large power needs. It may be affordable to individuals, but only if they take advantage of the government incentives. And despite how it may seem, Uncle Sam does not have unlimited funds. And certainly not enough to make a solar powered society a realistic possibility. It would cost trillions upon trillions, if it ever even could be done.
Sources for info:
(Why isn’t it all footnoted and numbered? Because it’s a blog post, not a graduate thesis. Still, the information is factually accurate. If it isn’t, then prove it. And I’ll have to eat crow. But… that isn’t going to happen.)
This entry was posted on Tuesday, August 28th, 2007 at 12:28 am and is filed under Bad Science, Enviornment, Website. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.
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