Archive for July, 2008
New Material to Generate Electricity From Heat - Twice the Efficiency of Other Materials
On July 29, 2008 in Uncategorized
From Renewable Energy World:
Material May Help Autos Turn Heat into Electricity
by Pam Frost Gorder, OSUOhio, United States [RenewableEnergyWorld.com]Researchers have invented a new material that could potentially make cars more efficient, by converting heat wasted through engine exhaust into electricity. The researchers say that the material has twice the efficiency of anything currently on the market.
“We’d been working for 10 years to engineer this kind of behavior using different kinds of nanostructured materials, but with limited success. Then I saw this paper, and I knew we could do the same thing we’d been trying to do with nanostructures, but with this bulk semiconductor instead.”
– Joseph Heremans, Ohio Eminent Scholar in Nanotechnology, Ohio State University.
The same technology could work in power generators and heat pumps, said project leader Joseph Heremans, Ohio Eminent Scholar in Nanotechnology at Ohio State University.
The materials are known as thermoelectric materials, and they rate the materials’ efficiency based on how much heat they can convert into electricity at a given temperature.
Previously, the most efficient material used commercially in thermoelectric power generators was an alloy called sodium-doped lead telluride, which had a rating of 0.71. The new material, thallium-doped lead telluride, has a rating of 1.5 — more than twice that of the previous leader.
What’s more important to Heremans is that the new material is most effective between 450 and 950° Fahrenheit — a typical temperature range for power systems such as automobile engines.
Some experts argue that only about 25 percent of the energy produced by a typical gasoline engine is used to move a car or power its accessories, and nearly 60 percent is lost through waste heat — much of which escapes in engine exhaust. A thermoelectric (TE) device can capture some of that waste heat, Heremans said. It would also make a practical addition to an automobile, because it has no moving parts to wear out or break down.
“The material does all the work. It produces electrical power just like conventional heat engines — steam engines, gas or diesel engines — that are coupled to electrical generators, but it uses electrons as the working fluids instead of water or gases, and makes electricity directly.”
“Thermoelectrics are also very small,” he added. “I like to say that TE converters compare to other heat engines like the transistor compares to the vacuum tube.”
The engineers took a unique strategy to design this new material.
To maximize the amount of electricity produced by a TE material, engineers would normally try to limit the amount of heat that can pass through it without being captured and converted to electricity. So the typical strategy for making a good thermoelectric material is to lower its thermal conductivity.
In Heremans’ lab, he used to work to lower the thermal conductivity by building nanometer-sized structures such as nanowires into materials. A nanometer is one billionth of a meter.
Those nanostructured materials are not very stable, are very difficult to make in large quantities and are difficult to connect with conventional electronic circuits and external heat sources.
For this new material, he and his colleagues took a different strategy: they left out the fancy nanostructures, and instead focused on how to convert the maximum amount of heat that was trapped in the material naturally. To do this, they took advantage of some new ideas in quantum mechanics.
Heremans pointed to a 2006 paper published by other researchers in the journal Physical Review Letters, which suggested that elements such as thallium and tellurium could interact on a quantum-mechanical level to create a resonance between the thallium electrons and those in the host lead telluride thermoelectric material, depending on the bonds between the atoms.
“It comes down to a peculiar behavior of an electron in a thallium atom when it has tellurium neighbors,” he said. “We’d been working for 10 years to engineer this kind of behavior using different kinds of nanostructured materials, but with limited success. Then I saw this paper, and I knew we could do the same thing we’d been trying to do with nanostructures, but with this bulk semiconductor instead.”
Heremans designed the new material with Vladimir Jovovic, who did this work for his doctoral thesis in the Department of Mechanical Engineering at Ohio State. Researchers at Osaka University — Ken Kurosaki, Anek Charoenphakdee, and Shinsuke Yamanaka — created samples of the material for testing. Then researchers at the California Institute of Technology — G. Jeffrey Snyder, Eric S. Toberer, and Ali Saramat — tested the material at high temperatures. Heremans and Jovovic tested it at low temperatures and provided experimental proof that the physical mechanism they postulated was indeed at work.
The team found that near 450° Fahrenheit, the material converted heat to electricity with an efficiency rating of about 0.75 — close to that of sodium-doped telluride. But as the temperature rose, so did the efficiency of the new material. It peaked at 950° Fahrenheit, with a rating of 1.5.
Heremans’ team is continuing to work on this patent-pending technology.
“We hope to go much further. I think it should be quite possible to apply other lessons learned from thermoelectric nanotechnology to boost the rating by another factor of two — that’s what we’re shooting for now,” he said.
This research was funded by the BSST Corporation; the State of Ohio Department of Development’s Center for Photovoltaic Innovation and Commercialization at Ohio State University; the Beckman Institute; the Swedish Bengt Lundqvist Minne Foundation; and NASA’s Jet Propulsion Laboratory.
Pam Frost Gorder is an assistant director of research communications at Ohio State University.
Couple this with some heat from the sun, a wood stove, a propane stove, a clothes dryer, or just about anything else that loses a lot of efficiency through heat output, and things would become a lot more interesting. I’m kind of miffed about the working temperature though, wish it was a bit lower.
SolarNetwork - Open Source Monitoring Project
On July 27, 2008 in Uncategorized
Found this on Slashdot:
http://www.solarnetwork.net/
“solarNetwork.net is an open-source project and experiment to test a method of distributed energy production. It relies on continuous participation and cooperation of an online community.
We hope this community develops to both 1) build out the infrastructure of the network, and 2) provide the real-world know-how and data to support a new type of energy company.”
“An Experiment
The project aims to construct the framework of equitable cost sharing that will underlie a business method outlined in the provisional patent.
Through solarNetwork.net, solar photo-voltaic energy is collected, consumed, measured and recorded locally at sites around the globe, called solarNodes. Data from each solarNode is aggregated at a central database of solar energy information.
SolarNetwork.net members, in theory, would not share electricity with each other; but they do share the savings that their local-energy generation delivers.”
“solarNetwork.net is being studied as part of a Masters thesis in the department of Electrical and Computer Engineering at the School of Engineering at the University of Auckland, to be completed December 2008.
Until fairly recently solar energy has been sidelined as an unrealistic form of energy generation for the home.
In reality a large amount of solar energy falls on people’s roofs each day - maybe not enough to power your house, but at least enough to take note of.
Let’s say you live in San Diego, have a couple of 80 Watt solar panels, some motorboat batteries, and an inexpensive inverter. You set up the panels on your roof to fill the batteries under sitting your house during the day, so you can use the electricity in the evening. On a really sunny day you might be able to store a few Amp Hours in a battery which you could use later - maybe a few hours of a desk lamp’s light.
Clearly, it’s not a lot of energy, but we’d all agree: it’s not absolutely nothing. And if you actually used this system on that sunny day, maybe a few cents were shaved off your bill.
Now imagine that you had 2 houses with this solarNode setup: one in San Diego, and one in Sydney, and you kept track of the energy collected, using a very-low-power computer, and a charge controller. It might be a sunny day in SD, and an overcast day in Sydney, so that only one house (the SD house) would report full batteries to power that San Diego desklamp that evening. However, if there were a cooperative agreement between the two houses, that 12 cents of savings from solar electricity generated in San Diego could conceivably be shared between the two houses.
That’s right: 6 cents each. And maybe the next day, Sydney was beautifully sunny, and San Diego was grey. Or maybe, they both had sunny days - it’s just weather and we can’t control it. But, we’re pretty sure that it will follow the model of a Markov Chain, according with the predictable seasonal variances (i.e. Summer: hot, direct sunlight, Winter: colder, indirect sunlight) based on the hemisphere of the earth you live on. That helps a little.
Gathering the data streams from these small-sized generators is an interesting project, and crucial to the rollout of the software and network. But a few desklamps aren’t going make a difference to the power consumption and energy policy of a significant number of people, let alone the planet’s population. However, because we can extrapolate from this data set fairly well, we should have a very powerful bunch of “What-If” scenarios to run.”
The basic SolarNode client consists of a low-power computer attached to a charge controller. On a periodic basis, the SolarNode queries the controller to take a snapshot of the power being generated, and reports it to the SolarServer.
I would suggest checking this out, if you want to or are willing to contribute.
MIT Researchers Improve Solar Cell Performace
On July 14, 2008 in Uncategorized
From http://web.mit.edu/newsoffice/2008/solarcells-0710.html but found on Slashdot
This is something I am very excited for, and hopefully the rest of you are as well. Especially the fact that it can be adapted to existing solar cells without having to just switch technologies. What a very appealing and uplifting ‘invention.’
Thanks MIT!
MIT opens new ‘window’ on solar energy
Cost effective devices expected on market soonImagine windows that not only provide a clear view and illuminate rooms, but also use sunlight to efficiently help power the building they are part of. MIT engineers report a new approach to harnessing the sun’s energy that could allow just that.
The work, to be reported in the July 11 issue of Science, involves the creation of a novel “solar concentrator.” “Light is collected over a large area [like a window] and gathered, or concentrated, at the edges,” explains Marc A. Baldo, leader of the work and the Esther and Harold E. Edgerton Career Development Associate Professor of Electrical Engineering.
As a result, rather than covering a roof with expensive solar cells (the semiconductor devices that transform sunlight into electricity), the cells only need to be around the edges of a flat glass panel. In addition, the focused light increases the electrical power obtained from each solar cell “by a factor of over 40,” Baldo says.
Because the system is simple to manufacture, the team believes that it could be implemented within three years–even added onto existing solar-panel systems to increase their efficiency by 50 percent for minimal additional cost. That, in turn, would substantially reduce the cost of solar electricity.
