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Solar Panels 2.0 - Have your computer power itself!
Tomanta
Registered User regular
Registered User regular
So a new material has been developed that can generate electricty from heat (or, infrared rays).
Daily Tech
I've excerpted a few parts. If I'm reading the article right, once the electrical issues are resolved (how do we convert that much AC power into DC?) your computer case could be lined with this stuff. The heat your computer generates would be absorbed and turned into electricity which would then power your computer. Laptops could have almost unlimited battery life.
Outside of that application, what other uses for this could there be? Could this be a major solution to energy problems? (It won't be a 100% solution, as the energy transfer rate is not perfect). How would you design a car to use this?
Daily Tech
Daily Tech wrote:The new cells consist of massive arrays of nanoantennas, which can collect energy from light and other sources. The INL team discovered a way to mass produce these arrays on flexible sheets of plastic. The only crucial problem remaining unresolved is developing additional components to harvest the collected energy by transforming it to electricity.
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The nanoantennas absorb a targeted wavelength range of mid-infrared rays. The Earth continuously emits these rays thanks to the solar energy that it absorbs during the day. This would allow for continuous solar panel operation, in theory. Traditional panels can only absorb visible light and thus are idle at night.
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Gold was selected after testing it, manganese and copper's reactions to IR rays. After careful computer design, an antenna which could collect 92 percent of the energy from infrared rays was achieved in theoretical simulations.
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Current cells only have an efficiency of around 20 percent, due to the inherent inefficiency of the chemical reactions used to harvest visible light.
I've excerpted a few parts. If I'm reading the article right, once the electrical issues are resolved (how do we convert that much AC power into DC?) your computer case could be lined with this stuff. The heat your computer generates would be absorbed and turned into electricity which would then power your computer. Laptops could have almost unlimited battery life.
Outside of that application, what other uses for this could there be? Could this be a major solution to energy problems? (It won't be a 100% solution, as the energy transfer rate is not perfect). How would you design a car to use this?
Tomanta on
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92% is theoretical which means most likely the actual absorption is a third of that to start with if not lower.
being able to mass produce them does not mean that making them is cost effective
So, computer emits 80%, system gathers 92% (assuming the system itself can be thermally isolated from the computer so it doesn't heat up by conduction) which it then converts 30% of into electicity.
This would then supply 22% more electricity back to the system. There is an iterative step here that I can't be bothered to solve, but it would mean your computers power supply could be about a fifth weaker, meaning battery life could go 20% longer.
This is an interesting breakthrough, but the AC current generated is effectively useless, all it would do is make the material hot.
not to mention that while these nano solar antenae might get you 20% more power, it might cost 100% more...
edit - 330 K source and 293 K bath, Carnot efficiency = 1 -(293/330)^0.5 = 6%
Typically a well designed power station can get about half of its Carnot engine efficiency, so your looking at about a 3% conversion rate to electricity.
in 20 years we may just have mini nuclear reactors powering our entire house.
the power supply in your computer is really just a transformer anyway it gets its power from the wall.
Still, 3-6% conversion from incident energy to electricy isn't useless as a thermal energy panel, it's just useless for recharging your computer from it's own heat. It's much more likely to see use wrapped around a nuclear plants waste heat pipes, or next to it's boiler. Now there you probably have a heat source at say 400-500K and can still use ambient as background.
Like much of these announcements, they try to get people excited with some miracle tech like eternal batteries or phones that recharge inside, but what the actual excitement will be is a few % extra power from power stations. You could also layer them in behind normal solar panels to up their efficiency a bit, since they get damn hot.
Nope, it would still only work during the day. To generate work you need a heat gradient, when the sun is up, you can use it as your hot source and the ambient air as your cold reservoir. Once the sun goes down what is your hot source? The ground might perhaps be 1-2 degrees warmer than the air, but thats going to cut your conversion efficiency down to a few tenths of 1%.
It would make more energy during the day, but only a tiny fraction of that at night.
Seriously, this is for indoor use in power stations, or for supplementing other sources. If it's super cheap then you could just stick it everywhere and use it that way, but I reckon the converter to useful electricity will be what costs a lot of cash.
Imagine placing this on rooftops in a city, or on houses. Wouldn't there be plenty of stored heat to last the night?
It's not about how much energy there is, it's about how much 'hotter' that energy is than the ambient heat bath. Clearly the city contains a huge amount of heat energy, however its all only a few degrees above the energy in the air. Thus you get a tiny rate of conversion on the energy you absorb in the panel into electricity.
The energy also comes off very slowly, and not all of it is radiated. Much of the heat in your homes and so forth is conducted away into the ground, or the air. The rate of heat energy loss through radiative transfer falls off rapidly at lower temperatures.
that shit gets hot at night!
Trombe wall.
The heat stored in a trombe wall could be used far more efficiently to simply heat the house the trombe wall was attached to. A trombe wall won't get more than 20 degrees above ambient, and it certainly doesn't radiate out an enormous amount of heat (since that is it's exact purpose, to store heat for nighttime use, not radiate it all away)
I'm not seeing why it couldn't be used to produce electricity overnight while it also heats the home...
Because its not hot enough compared to the ambient temperature to justify the increased expense of installing the panels unless these things are as cheap as paper.
With a few tens of degrees of difference above room temperature your maximum conversion efficiency from radiated thermal energy to electricity is a few %, so 100W of incident IR would correspond to about 2~3 W of electrical output.Conversely designing the system simply to minimize radiative losses (the opposite of what you would do to get electricity out) would allow you just to use hot air directly to warm people in the house. Just allowing natural expansion of hot air to circulate warm air into a room can be much more useful than trying to turn it into electricity.
To make things efficient at doing anything other than heating something up you need a "hot source" which can be hundreds of degrees kelvin above ambient.
You're on the right track. Or you would be, if we were talking about Stirling engines. The stuff referenced in the OP isn't using thermal differentials so Carnot efficiency doesn't apply here.
You're probably correct about Trombe walls - collecting nighttime radiation from the wall for use as electricity would likely be too expensive. Small temperature differences aren't the reason why, though.
Let's say you have a heater that runs on electricity with these panels inside, wrapped around or whatever. You turn it on like normal, drawing the same amount of electricity as a normal one. Once it heats up, the panels kick in and turn some of the heat into extra power, thereby lowering the amount of electricity you're drawing from the grid, which also lowers your bill.
Correct? Though I wonder if the extra heat that's being drawn off wouldn't make the heater work harder, which will take more energy.
Ayliana Moonwhisper Ecksus Cerazal
Drawing off the theory as presented in the original article, not the science behind it that makes it really impractical (you can look at other posts for that):
Sort of. Except it turns the heat into electricity, the process of which causes it to loose energy. Turning that back into heat (which somewhere along the line it would need to do to power the heater) causes more energy loss. It ends up being a net loss of electricity, which means you are drawing more power from the grid to power the heater.
It doesn't work with the heater because the heater is being used to heat the house - creating electricity from that heat just means the heater has to work harder. With a computer, you WANT to draw off heat. So, theoretically, you start the computer. It heats up, these panels draw off the heat and converts it to electricity to power some the computer and keeps it cool. If the transfer could be made efficient enough, the computer wouldn't waste electricity. That would lower your grid usage.
EDIT: I want to study up on some physics, and it seems we have a few people here who know a bit. Anyone have a good starting point?
I think efficiency is really a moot point. Nighttime radiation is next to nothing compared to daytime radiation, so the whole 24/7 thing doesn't matter.
I think carnot efficiency gives you the maximum possible efficiency you an possibly get with any machine doing work which isn't a low temperature heater (since there waste heat is what you want). Just because it isn't a steam boiler doesn't mean it can do better than the Carnot efficiency, it just means it is usually more complicated to calculate the 'temperature' of the energy involved. Except that it isn't here, because the energy comes from a source with a temperature which can be found.
edit - "Carnot's theorem is a formal statement of this fact: No engine operating between two heat reservoirs can be more efficient than a Carnot engine operating between the same reservoirs." is the basic principle of Carnots theorum. These solar panels constitute an engine, and they cannot break the 2nd law of thermodynamics, so they can't be more efficient that a Carnot engine.
edit2 - Hmm, although it does state "mechanical work". Still, the entropy diagram and conceptual thought is for a black box taking in heat energy, outputting work, and waste heat. I think it might still be accurate.
edit3 - It seems that a photovoltaic cell is in fact not limited by carnot efficiency. Hmm, that doesn't make any sense. Then surely I could run this device backwards and violate the conservation of entropy by making it into an IR beam and heating something up with it.
For example, a thermal "blackbody" will always absorb radiated energy, regardless of what temperature it reaches. Of course, in reality, there's no such thing. Not that we know of, anyway.
Yeah, I was looking online but I'm not at work so I can't read the whole papers. From what I can gather there is certainly some sort of analogous "carnot" effect for quantum systems, its just much more complex and uses lattice vibrations as the "heat bath" or something
The big deal isn't so much that "Oh hey, we can pick up power from radiated EM fields at different frequencies" - that's been done for decades (see: Crystal radios, AM/FM, cellphones, wireless network) - it's more that a manufacturing process has been discovered that can reliably produce antennas at the small sizes necessary to act as antennas for infrared frequencies.