One good use for temperature change

Changing temperature powers sensors in hard-to-reach places

From the University of Washington by

A centuries-old clock built for a king is the inspiration for a group of computer scientists and electrical engineers who hope to harvest power from the air.

The power harvester could be placed outside and runs off of temperature changes in the natural world.

The clock, powered by changes in temperature and atmospheric pressure, was invented in the early 17th century by a Dutch builder. Three centuries later, Swiss engineer Jean Leon Reutter built on that idea and created the Atmos mechanical clock that can run for years without needing to be wound manually.

Now, University of Washington researchers have taken inspiration from the clock’s design and created a power harvester that uses natural fluctuations in temperature and pressure as its power source. The device harvests energy in any location where these temperature changes naturally occur, powering sensors that can check for water leaks or structural deficiencies in hard-to-reach places and alerting users by sending out a wireless signal.

“Pressure changes and temperature fluctuations happen around us all the time in the environment, which could provide another source of energy for certain applications,” said Shwetak Patel, a UW associate professor of computer science and engineering and of electrical engineering.

The UW team will present its research at the Association for Computing Machinery’s International Joint Conference on Pervasive and Ubiquitous Computing this month in Seattle.

The system works like this: A metal bellows about the size of a cantaloupe is filled with a temperature-sensitive gas. When the gas heats and cools in response to the outside air temperature, it expands and contracts, causing the bellows to do the same. Small, cantilever motion harvesters are placed on the bellows and convert this kinetic energy into electrical energy. This powers sensors that also are placed on the bellows, and data collected by the sensors is sent wirelessly to a receiver.

A number of battery-free technologies exist that are powered by solar and ambient radio frequency waves. The researchers say this technology would be useful in places where sun and radio waves can’t always penetrate, such as inside walls or bridges and below ground where there might be at least small temperature fluctuations.

The device could be placed in hard-to-reach areas where temperatures fluctuate slightly.

For instance, the device could be placed in an attic or inside a wall, and sensors would be tuned to check for water leaks. Similarly, when used inside a bridge, the sensors could detect any cracks forming or structural deficiencies. In both cases, the sensors would send a signal to the nearby powered receiver.

A temperature change of only 0.25 degrees Celsius creates enough energy to power the sensor node to read and send data wirelessly to a receiver 5 meters away. That means any slight shift in an office building’s air conditioning or the natural outside air temperature during the course of a day would be more than enough to activate the chemical in the bellows.

The UW’s technology uses temperature changes over time as its power source. Devices called thermoelectric generators also leverage varying temperatures for power, but these instruments require a temperature difference at an exact moment, such as in a place where one side is hot and the other is cool.

The researchers have filed patents for the technology and plan to make it smaller, about the size of a D battery. A future version would include four chemicals that activate in different temperature ranges so the same device could be used in various climates.

“I think our approach is unique,” said Chen Zhao, lead author and a UW doctoral student in electrical engineering. “We provide a simple design that includes some 3-D printed and off-the-shelf components. With our Web page and source code, others can download and build their own power harvesters.”

Other members of the research team are Joshua Smith, a UW associate professor of computer science and engineering and of electrical engineering; Sam Yisrael, an undergraduate student in electrical engineering; Sidhant Gupta, a former UW doctoral student; and Eric Larson, an assistant professor at Southern Methodist University and former UW doctoral student.

This research was funded by the Intel Science and Technology Center for Pervasive Computing at the UW and the Sloan Foundation.


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Gary Pearse
September 4, 2014 4:22 am

Hmm.. 0.25C. This is an automatic “temp anomaly” detector. Put ’em all over the place and let ’em send you the data.

Reply to  Gary Pearse
September 4, 2014 4:44 am

In place of a thermistor?

Reply to  Gary Pearse
September 4, 2014 5:32 am

Wouldn’t this also expand/contract with the change in barometric pressure? So as a Temp only detector, it may not be as reliable.

Reply to  MikeH
September 4, 2014 6:12 am

No problem, you just add a pressure sensor then you work out the inverse barometer bias correct to the temperature anomaly and work out how much climate change has occurred !
You can obviously adjust the barometer correction algorithm to get the “correct” climate results.
This method shows promise for producing robust climate assessments as the world continues to warm but more research is needed to provide a working data product.

Reply to  MikeH
September 4, 2014 6:13 am

PS , wife and two children to support, please give generously.

September 4, 2014 4:46 am

Research supporting an undergrad, current doctoral student, two previous doctoral student and the professor.

Greg Locock
September 4, 2014 4:58 am

file this under pointless. Solar and wind are far higher energy density sources. I se no reason why driving a sensor off its own signal makes any sense.

Reply to  Greg Locock
September 4, 2014 8:45 am

Solar requires sunlight and regular cleaning, wind needs windy places and large and maintenance-intensive mechanical units. Neither works indoors or underground for example. To me this seems quite feasible for powering small units in difficult-to-access places.

Tom J
September 4, 2014 5:13 am

As a minor piece of trivia it may be worthy to note that the Swiss government gave John F. Kennedy an Atmos clock during his time as President, and it was in use at the White House.

Mark Bofill
September 4, 2014 5:26 am

Pretty slick! I like it.

John Slayton
September 4, 2014 5:30 am

Lemme see, now. By using one of these devices I can save 15 meters of wire? (The distance to a powered receiver) I knew copper was getting pricey, but this is ridiculous.

Reply to  John Slayton
September 4, 2014 5:37 am

This would be ideal in situations where it’s impossible or extremely difficult to route the wire. There are a whole host of reasons why it would be difficult to do so, and when I was working as an electrician I encountered almost all of them.

Reply to  John Slayton
September 4, 2014 5:42 am

There are a lot of applications, especially after construction is done, where adding wiring is very expensive. It’s one of the reasons I bought three temperature and voltage data loggers from and own a wireless Davis weather station.

September 4, 2014 5:39 am

OMG, they’re using choloethane: a powerful greenhouse gas and potent ozone deleter.
Just wait till the EPA get onto it, they’ll have them shut down for crimes against humanity and thrown into jail.

September 4, 2014 5:44 am

The system works like this: A metal bellows about the size of a cantaloupe is filled with a temperature-sensitive gas. When the gas heats and cools in response to the outside air temperature, it expands and contracts, causing the bellows to do the same.

Is there any temperature insensitive gas?
Anyway, My greatest concern would be gas leaks. Or can the device work despite of the bellows having leaks?

Reply to  urederra
September 4, 2014 5:53 am

Those sorts of bellows can last for decades. They didn’t make it, it’s a spare part for an Atmos clock. It is likely a far weaker structure than the bellows used in mechanical barometers, those use a vacuum instead of a “temperature insensitive gas” like unobtanium.

Reply to  urederra
September 4, 2014 5:59 am

yes, that was my first reaction on reading that line. PV/T=k being the basic relationship for an ideal gas.
In fact it seems to be more to do with evaporation than the gas being temperature sensitive. Chloroethane boils about 12.5 deg C apparently.
The belows are metal so hopefully done leak. If they do the it obviously will do nothing ( apart from destroying the ozone layer ).

Reply to  Greg
September 4, 2014 7:20 am

I have this crazy idea. Fill the bellows with CO2 and put a glass window on top of the bellows, so short wave IR radiation passes through the window, heats the CO2 and expands the bellows. That way you sequester CO2 inside the bellows, you trap the climate change long wave radiation and you get energy out of it.
Win-win-win situation. 😛

Reply to  urederra
September 5, 2014 5:23 pm

I think that’s clueless journalist speak for “volatile liquid”. You’re going to get a lot more PSI per degree out of a liquid at its vapor pressure than a dry gas.

September 4, 2014 5:47 am

Smidgen of a widget.

September 4, 2014 5:50 am

Mods – bad link in “Now, University of Washington researchers have taken inspiration from the clock’s design and created a power harvester that…” needs a .html on the end.

September 4, 2014 5:52 am

The linear harvesters produce massive 0.2 millijoules per bump. Enough to power their microprocessor for 52 milliseconds. There’s probably more energy in a rat’s fart.
What amazes me is that they found a radio transmitter that could work at this kind of power level. Admittedly 5m in air means they won’t but getting far if they put it inside a concrete bridge but they made it work.

Reply to  Greg
September 4, 2014 5:58 am says “The energy module ECO 200 is an energy converter for linear motion. It can be used to power the PTM 330 radio module or derivates. The energy output at every actuation of the spring is sufficient to transmit 3 sub-telegrams with a PTM 330 module.” Looks like a fun device.

Dave Ward
September 4, 2014 6:42 am

“Below ground where there might be at least small temperature fluctuations”
That’s one location where temperatures tend to be the most stable! Some of the telephone exchanges I used to work in had cable chambers under the main distribution frames, and regardless of temperatures outside (or even inside the building) there was never any detectable variation down there…

Non Nomen
September 4, 2014 9:35 am

Pretty interesting: take the London Tube, for example: each train pushes air through the pipes before it and creates a less dense atmosphere behind. An elevator shaft shows the same phenomenon…

September 4, 2014 9:52 am

“A metal bellows about the size of a cantaloupe is filled with a temperature-sensitive gas.”
What? You mean there are gases out there that are NOT temperature sensitive? Go on!
Trying to sound scientific does not work when it makes you look stupid. A non-reactive or stable gas might be better, one that will not react with the materials of the bellows. Duh!

September 4, 2014 1:55 pm

Is this how the Matrix gets its power from human bodies?

Dave Wendt
September 4, 2014 5:02 pm
September 4, 2014 6:41 pm

Wow, I’m surprised at all the negativity in this comment thread. Yes, it’s a very small innovation, but an innovation nevertheless. Is it really that hard for so many of you to consider where this could go? I can see potential, but yes considerably more work to reach any practical application is needed.
I noticed something else here as well. This is not being funded by the government, so I’m completely behind someone using their own money (not mine), to innovate and search for new ideas. This model should be the norm given our Constitution.
From the website (bold is mine)…
” Intel Science and Technology Center for Pervasive Computing
The Pervasive Computing center was launched in September 2011. It is centered at the University of Washington and brings together researchers from top-tier research universities including leaders in pervasive computing, wireless communication and sensing, artificial intelligence and machine learning, computer vision and HCI.
The ISTC-PC will bring together researchers from six top tier US research universities, including leaders in pervasive computing, wireless communication and sensing, artificial intelligence and machine learning, computer vision, human-computer interaction (HCI), and security. The University of Washington will be the hub of the center, coordinating research among the five other universities involved in the collaboration, including Georgia Institute of Technology, Cornell University, the University of Rochester, UCLA, and Stanford University. The ISTC-PC will be co-led by Dieter Fox, associate professor of Computer Science & Engineering at the University of Washington, and Anthony LaMarca, a principal engineer at Intel.
The ISTC-PC is designed to ensure a successful collaboration through an open research model that encourages widespread sharing of information and results. While Intel is funding the work of the center, the results of the research will be made widely available through open-source software releases and technical publications. By adopting this open approach Intel hopes to encourage collaboration across the pervasive computing community and to foster the development of breakthrough innovations. The freedom to share intellectual property overcomes one of the key barriers to the success of many industry-academic research collaborations, which often stumble over IP rights.”
Additionally, It’s nice to see my undergraduate alma mater doing something that isn’t entirely Socialist for a change.

September 4, 2014 11:26 pm

You can get a small amount of electrical power from radio waves also, I would think that would be far more efficient and steady then this device at a lot less cost.

Reply to  Mark Luhman
September 5, 2014 5:30 am

I never built a crystal radio, but an important part is a long antenna. Sort of defeats one of the goals of this device.
Try working through some of the math – take the effective radiated power from stations in your area, assume it goes out in a disk, figure out the percentage of the cylinder where you are (i.e. cylinder with radius being the distance to the station, height being the vertical extent of the signal, you may to guess at that one), and that will be the power available.
Compare that to the power required to raise the local air temperature and atmospheric pressure, since that’s what this device is tapping, I suspect this device has a lot more power available, though it’s too variable for a lot of purposes.

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