New thermophotovoltaic materials could replace alternators in cars and save fuel.
Researchers at MIT are developing new technology for converting heat into light and then into electricity that could eventually save fuel in vehicles by replacing less-efficient alternators and allowing electrical systems to run without the engine idling.
A "thermophotovoltaic" (TPV) generator burns fuel to heat a material that emits light (labeled "radiator"). The light is then filtered and converted into electricity in photovoltaic (PV) cells. (Image courtesy of John Kassakian, MIT.)
The technology, called thermophotovoltaics, uses gasoline to heat a light-emitting material, in this case tungsten. A photovoltaic cell then converts the light into electricity. The idea has been around since the 1960s, says John Kassakian, MIT electrical engineering and computer science professor. But until now, the light emitters for the photovoltaics produced inefficient and very costly systems. Improvements in the materials used in these latest devices -- possible in part because researchers can modify the material structure at the nanoscale -- are now making much more efficient systems, Kassakian says.
According to Kassakian, the system could potentially be a more efficient way to power electrical systems in a vehicle than the current alternator-based one, which wastes energy in two stages: the internal combustion engine converts only about 30 percent of the energy in fuel into movement, and then the alternator is only 50 percent efficient in converting the mechanical energy into electricity. He says a small prototype thermophotovoltaics device that could confirm the system's improved efficiency might be ready in a year.
The researchers modified the surface structure of the light emitter, etching into it nano-sized pits to tune the wavelengths of light emitted to precisely those a photovoltaic cell can convert most efficiently into electricity. They further refined the device with the use of filters that allow the desired wavelengths of light to pass through to the photovoltaic cells, but reflect other wavelengths back to the light emitter. The reflected light carries energy that helps keep the emitter hot, reducing the amount of fuel needed.
In addition to replacing the alternator with a thermophotovoltaic module, says Kassakian, the technology could be part of an air-conditioning system for vehicles that doesn't require a compressor. Because this would significantly decrease the load on an engine, it could make it possible to turn off the engine when the vehicle stops in traffic and easily restart it. Today's hybrids use this technique to save gas, but require large batteries to provide electricity for the radio and lights, and to restart the engine, and they have to turn the engine back on when the battery charge runs out. In the new MIT system, these batteries wouldn't be necessary.
A new way to convert heat into electricity could lead to more efficient solar power.
Guest (Sam Tuole)
Isnt there already so much heat
Cant the heat thats wasted in enormous amount in the engine be used for something useful ?
Guest (Bob Downs)
re: isn't there already so much heat..
I'm no expert but I would think that the heat now wasted could be utilized as the driver for a device
similar to that described in the article. A typical alternator puts out something like 1 kw. Not sure
how much heat a typical engine puts
out(radiated plut the exhaust heat) but it has to be in the range of at least 10 times that much so the device would not have to be very efficient. However, it would have
to operate in the presence of pretty high temperatures.
Guest (Jonas Norrby)
A car engine is assumed to be 30% efficient. Assuming a car engine to have a average power rating of 80 kW that would mean an excess of heat in the order of 56 kW. There was an article before on TR about advance in thermoelectric materials which convert heat directly into electricity. These have been used before in space systems but have a rather poor efficiency which was improved upon.
Guest (CKE)
engine has heat, just can't convert it
There's plenty of heat from the engine. But it's at too low a temperature to give off photons that a TPV device like MIT's could use. And using a Peltier wouldn't work much better because there's too small a delta-T. Low grade heat is tough to turn into electricity.
Guest (Techno)
Engine heat to supplement only
They can use the engine heat to bring the thermophotovoltaic alternator to operating temperature(maybe half way) and the unit can raise the temperature to power generating point. The battery and supply the necessary power until the engine reach operating temperature. A penny save is a penny earned. A few degree save in heating fuel is a few degree earned.
Guest (Nick Kearney)
engine has heat, just can't convert it
Heat basically is infrared radiation isn't it? there is another group of scientist who are using quantum Microdotting to create full spectrum solar pannels.
I wonder if their reseach could aide the MIT crew?
lbl.gov/Science-Articles/Archive/MSD-full-spectrum-solar-cell.html
I also think they overlook something simple as well the thermal imager the technology behind that turns heat into visible light as well.
Of course this is just a thought.
If enough of scientist come together they can make the difference.
N~K
Guest (lee mcclune)
Yes, there are thermoelectric or TCs that are used to produce electricity from heat, a CO in AZ
makes and markets them,, LFM
Guest (Jonas Norrby)
I'm intrested in how much tungsten they use and how much tungsten is available? Basically the kW/kg tungsten compared to kg tungsten/Tons tungsten available. The problem with materials which are not common is that the demand can kill any advantage due to increases in the price. For example PV cells based on silicon where the material is now becoming the bottleneck due to possible greater demand than availability.
Guest (CKE)
To sustain combustion, a good amount of heat will go up the flue with waste gases via convection. As for undetectable in the field - ever heard of infrared cameras? There will be a heat plume visable from far away. Past TPV (thermovoltaic) efforts have fooled with light filters, special emmitters, etc. As I understand, they have not cracked 30% efficiency either. I wonder if at the end of the day, system efficiency is not much better than the common ICE/alternator.
Guest (Techno)
There is a new engine design call toroidal engine that is much more efficient that the existing inline IC engine. You can check it out at http://www.rotoblock.com/
Guest (Jim)
designs claiming to be more efficient internal combustion engines have been around since it was invented, but unfortunately, most are dead ended. This one is very complicated and the frictional losses of 8 pistons probably will be its downfall. ICEs are simply inefficient by nature. Some ways to improve efficiency are to run at higher temperatures like a F1 engine which runs at about 140-150 deg C and has minimal surface area. (How about 750 HP from a 100kg engine.) Ceramic coatings on cylinders and exhausts combined with turbochargers allow higher specific output from smaller engines and better efficiency, but not enough.
Guest (JimD)
How efficient can these devices get?
I'm imagining a vehicle entirely powered by these devices. Fuel -> light -> electricity -> motion might become competitive with the ICE. And I think you could control emissions more easily in a system designed solely to extract heat from the combustion of fuel.
Guest (Jim Dodds)
With all this nanotech why can't we design a filter that traps all the combustion products and produces some kind of useful byproduct?
jemd@wcvt.com
Guest (Ben)
Another great idea that you'll that will never be put to practical use.
"It will be several years before the technology can used in vehicles, though."
I've lost count of the number of times I've read about some great new idea only to see that sentence or a variation of it at the end of the story. Another tease!
Here's some ideas: stop having so many babies and ride a bicycle.
Guest (CKE)
I must have seen this tagline at the end of dozens of these R&D articles: "The authors feel this technology will be ready for commercial introduction in 2 years"
Guest (Jeff)
Using PV cells, in order to say get 14vdc@60 amps, minumal for todays cars, your talking more square footage of PV cells than your avererage 40' semi has. Unless they have come up with something new, I don't see the application being viable. Maybe they should just put it over the fireplace as a cute lightbulb
Guest (mARK)
they're only talking about running the lights, not moving the vehicle.
Guest (Steve)
Yes, you do need the amount of power that Jeff mentioned (60A). Your electrical system is far more than just lights - blower motors, stereos, gages/displays, computers, valves, etc. Even the smallest cars have 80-90A alternators. Do a little check - add up the amps of all the fuses in your fuse box.
Guest (Simon)
I'd rather go from heat straight to electricity
More research needs to go into thermoelectric(Seebeck) effect. Reference http://en.wikipedia.org/wiki/Peltier-Seebeck_effect
I would think you'd get better efficiences by skipping the light conversion. Great research though. Any improvement is good improvement.
Guest (Ron Wagner)
How could you get better efficiency?
How would you do it? I am more interested in home and industry based systems using biomass and waste heat, and solar heat.
Guest (CKE)
This is a very weak effect. In addition to a strong source of heat (we have this), it also needs a capacious source of cold - a large capacity heat sink. This is what's missing.
Cars use the Delta T of the radiator and the air to cool the motor. Isn't this a heat sink
Gr.
Guest (sterling)
Guest (Jonathan)
Thermophotovoltaic is one of the coolest words I have ever seen, regardless of how well this technology works currently.
Guest (Ron Wagner)
Home heat and electricity from biomass
Clean burning biomass might be able to supply electicity for hybrid vehicles and homes with this or other technologies. Industries also could produce their own electricity with waste heat. Simple solar devices could build enough heat to fuel these systems in hot climates.
Guest (CKE)
These alternative energy schemes all work better when they are stationary, and can take up a lot of space and weight. Hence, they should be used to create electricity as power plants. And another scheme on how to get the electricity into the cars (charging batteries, or making fuel) should be found.
Guest (Brandon B)
Couldn't you just use the Seebeck Effect and convert the heat directly to electricity. You would get 1 volt per degree difference from every 2 million pieces of nano-metal. You could pack a lot of them on anything of macroscopic size so this should work right?
Guest (Brandon B)
Going by those figures you should be able to get 5 volts of electricity per degree difference for every square centimeter of surface area.
To turn oscillations in to unidirectional rotations easily fabricated design available at http;/ww.ljsite.com/unigear.htm
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Guest (C.N.Guerriere,M.D.)
thermophotovoltaic technology
Wouldn't this technology be useful in aircraft as well,or would the weight to power ratio be too high?
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Guest (Patrik)
thermophotovoltaic tech
Wellwellwell, why don't they just put a second one of those things next to the exhaust.. that way they get heat for free.
Reply