Turning Waste Heat Into Electricity

ScienceNOW ^ | 4 May 2011 | Robert F. Service

[neverdem]

Enlarge Image

Energized. Spiking a conventional thermoelectric material with sodium and selenium creates regions in the crystal that conduct electricity more readily (blue and gold), boosting the material's performance.

Credit: Adapted from Y. Pei et al., Nature, 473 (5 May, 2011)

Engineers have come up with a handful of uses for computer chip-like devices that chill objects when plugged in or convert waste heat into electrical power—stuff like car seats that cool drivers on hot days and coolers that chill drinks when plugged in. But by-and-large, these devices, known as thermoelectrics, have remained too inefficient to make much of a real-world impact. Now, researchers in the United States and China report that they've come up with a new way to boost the performance of one of the most common thermoelectrics on the market, an advance that could pave the way for more widespread use in converting waste heat from cars and other mechanical devices into useful electricity.

Although efforts to improve thermoelectrics haven't paid off in a big way, it's not for want of trying. Physicists realized in the early decades of the 1800s that heat flowing in a circuit between two different conductors could generate an electric voltage. They also discovered the opposite effect -- electricity fed into such a device would heat one conductor and cool the other. The devices work because heat can push electrons around, and the motion of electrons can carry heat. Researchers have long tried to enhance the effect to make the devices practical. In doing so, the goal is typically to increase a property in the materials known as ZT, which depends on a set of factors that include a material's ability to conduct heat and its electrical conductivity. An alloy of lead telluride (PbTe), for example, which has long been used to generate electricity aboard satellites, has a ZT of around 0.8.

To increase ZT, researchers typically try to increase a material's electrical conductivity as much as possible while holding down its thermal conductivity. In 2008, researchers led by Jeffrey Snyder, a materials scientist at the California Institute of Technology in Pasadena, spiked PbTe with thallium, which boosted the ZT to 1.5. The group later determined that the thallium altered the electronic structure of the crystal, improving its electrical conductivity.

But thallium is toxic, so Snyder and his colleagues wanted to determine if they could match the improvement with other additives. Earlier this year, Snyder and his team at Caltech reported in Energy & Environmental Science that substituting sodium for thallium produced a ZT of 1.4. Now, Snyder's team, in combination with researchers from the Chinese Academy of Sciences' Shanghai Institute of Ceramics, report online today in Nature that adding selenium and sodium gives them a maximum ZT of 1.8. The selenium not only further improves the electrical conductivity, it also reduces the thermal conductivity, Snyder explains.

"It's excellent work," says Gang Chen, a thermoelectrics expert at the Massachusetts Institute of Technology in Cambridge. "It shows there's still room to improve existing materials," he says Snyder notes that the same strategy should improve the electrical conductivity, and thus the ZT, of other conventional thermoelectrics. With any luck, the improvements will be large enough to push thermoelectric devices out of niche applications and into the mainstream.

[doc1019]

Calling Dr. Epps ... please give this to us in untreatable examples. Bite size and digestible.

[doc1019]

untreatable = understandable, sorry.

[dila813]

So now turning the waste heat on internal combustion engines will boost their efficiency into a new realm. Environmentalists aren’t going to like this.

I suspect they will ban it soon.

[bigbob]

Peltier-Seebeck effects are opposite side of the same coin - a long-understood property for converting heat into electricity or electricity into the absence of heat (cooling). Used in everyday products like the valve in gas appliances or the type of cooler that runs on 12 volts.

See http://en.wikipedia.org/wiki/Thermoelectric_effect

Since well over half of the gas we burn in our cars turns into waste in the form of heat, this could be significant. Anything that improves the efficiency of thermoelectric materials is cool...or the opposite.

[Kevmo]

Thermionics has a future, though it’s likely to be a bumpy ride.

http://peswiki.com/index.php/Directory:Eneco_power_chip

Eneco power chip
From PESWiki
Jump to: navigation, search
Eneco is a development stage company that claims to have invented and patented a “solid state energy conversion/generation chip” that will convert heat directly into electricity or alternatively refrigerate down to -200 degrees Celsius when electricity is applied.

On Jan. 11, 2008, the company filed for Chapter 11 bankruptcy. (more)

Contents [hide]
1 About
1.1 Official Website
1.2 Latest Developments
1.2.1 Jan. 11, 2008
1.2.2 November 2006
1.3 Key Characteristics
1.4 How It Works
1.4.1 Thermionic Energy Conversion
1.5 Independent Validation
1.6 Patent
1.7 Company Profile
1.7.1 US Magnesium Corp
1.7.2 Other “Eneco” Company
1.8 In the News
1.8.1 PES Network News Coverage
1.8.2 Other News Coverage
1.9 Comments
1.10 Contact
1.11 See also

About
Official Website
http://www.micropower-global.com - Company has bought the IP to the Eneco technology.

http://www.eneco.com/
Technology Overview
The Science
Key Attributes
Advantages
FAQ
Patents
Publications
Latest Developments
Jan. 11, 2008
ENECO Files for Chapter 11 Protection - ENECO, one of the oldest LENR-related firms, filed for chapter 11 bankruptcy on Jan. 18. The firm’s focus is now primarily on thermal to electric conversion devices. Harold “Lew” Brown said that funding challenges were a significant factor that led to the filing. They are still in operation. (New Energy Times; March 10, 2008)
November 2006
Press conference held by Dr Lew Brown, president and CEO of Eneco [1]
Key Characteristics
According to http://www.eneco.com/co_about.html

Energy density efficiencies far in excess of all other available technologies.
Its energy density (a measure of power production for a given weight or size) is 5 times better than current lithium-ion-batteries and 2-4 times better than future micro fuel cell capabilities projected for 2010.
Reduced weight and size to fit with the new portable power needs of consumer electronics.
Semiconductor technology that allows for efficient manufacturing, high reliability, long life, and low maintenance.
Ability to convert waste heat economically and directly into electric power without moving parts to wear or make noise.
Readily scaleable from very small to very large applications without losing efficiency or cost effectiveness.

[neverdem]

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FReepmail me if you want on or off my health and science ping list.

[The Antiyuppie]

These devices are generally extremely inefficient. That’s why they are used where simplicity is paramount. they are “rugged”, but they don’t last forever generally due to thermal fatigue (these materials aren’t all that physically sturdy and the electrical bonding generally fails first).

I think it would take a 5x improvement in efficiency to get them out of the niche that they are in now, and that might be flat impossible without violating the laws of physics and thermodynamics - but then, it would be great to be proven wrong.

[neverdem]

Thanks for the links & text.

[ottbmare]

Isn’t there already a city in Sweden that is using its own garbage to manufacture its own electricity? It’s supposed to be pretty much independent and have extremely low electric rates, hence petroleum products are needed only to run vehicles.

[mosesdapoet]

“Peltier-Seebeck effects”
About 12 years ago I picked up an portable 12v Igloo cooler/warmer chest using that effect and it worked pretty good. During 90 degree weather in Chicago the ice cube tray formed ice cubes and kept the frozen food in a stable state. It also used a hell of a lot less juice than a normal refridge would. The only problem was that it created a lot of RFI when using the 120 ac/ 12v dc transformer when used in the apartment. Still have it in storage.

[thackney]

these devices, known as thermoelectrics, have remained too inefficient to make much of a real-world impact. Now, researchers in the United States and China report that they've come up with a new way...

The article states the old problem in enefficiency, then never mentions it again. It makes believe that the new and improved didn't make that much of a difference in the real problem.

[thackney]

Isn’t there already a city in Sweden that is using its own garbage to manufacture its own electricity?

There are many cities in the US that burn trash to generate electricity.

http://www.livinggreenmag.com/archives/energy_conservation/electricity_trash.html

[Ole Okie]

I had an Igloo that we sat between the seats of my Pontiac, and it did a good job.

My dad had one that was heated by propane. It was heavier duty than my electric one.