From the University of Rhode Island, some ideas on putting waste city heat to good use. They seem to recognize what most climate scientists don’t. There’s a lot of heat in cities.
URI researchers aim to harvest solar energy from pavement to melt ice, power streetlights, heat buildings
KINGSTON, R.I. – November 9, 2010 – The heat radiating off roadways has long been a factor in explaining why city temperatures are often considerably warmer than nearby suburban or rural areas. Now a team of engineering researchers from the University of Rhode Island is examining methods of harvesting that solar energy to melt ice, power streetlights, illuminate signs, heat buildings and potentially use it for many other purposes.
“We have mile after mile of asphalt pavement around the country, and in the summer it absorbs a great deal of heat, warming the roads up to 140 degrees or more,” said K. Wayne Lee, URI professor of civil and environmental engineering and the leader of the joint project. “If we can harvest that heat, we can use it for our daily use, save on fossil fuels, and reduce global warming.”
The URI team has identified four potential approaches, from simple to complex, and they are pursuing research projects designed to make each of them a reality.
One of the simplest ideas is to wrap flexible photovoltaic cells around the top of Jersey barriers dividing highways to provide electricity to power streetlights and illuminate road signs. The photovoltaic cells could also be embedded in the roadway between the Jersey barrier and the adjacent rumble strip.
“This is a project that could be implemented today because the technology already exists,” said Lee. “Since the new generation of solar cells are so flexible, they can be installed so that regardless of the angle of the sun, it will be shining on the cells and generating electricity. A pilot program is progressing for the lamps outside Bliss Hall on campus.”
Another practical approach to harvesting solar energy from pavement is to embed water filled pipes beneath the asphalt and allow the sun to warm the water. The heated water could then be piped beneath bridge decks to melt accumulated ice on the surface and reduce the need for road salt. The water could also be piped to nearby buildings to satisfy heating or hot water needs, similar to geothermal heat pumps. It could even be converted to steam to turn a turbine in a small, traditional power plant.
Graduate student Andrew Correia has built a prototype of such a system in a URI laboratory to evaluate its effectiveness, thanks to funding from the Korea Institute for Construction Technology. By testing different asphalt mixes and various pipe systems, he hopes to demonstrate that the technology can work in a real world setting.
“One property of asphalt is that it retains heat really well,” he said, “so even after the sun goes down the asphalt and the water in the pipes stays warm. My tests showed that during some circumstances, the water even gets hotter than the asphalt.”
A third alternative uses a thermo-electric effect to generate a small but usable amount of electricity. When two types of semiconductors are connected to form a circuit linking a hot and a cold spot, there is a small amount of electricity generated in the circuit.
URI Chemistry Professor Sze Yang believes that thermo-electric materials could be embedded in the roadway at different depths – or some could be in sunny areas and others in shade – and the difference in temperature between the materials would generate an electric current. With many of these systems installed in parallel, enough electricity could be generated to defrost roadways or be used for other purposes. Instead of the traditional semiconductors, he proposes to use a family of organic polymeric semiconductors developed at his laboratory that can be fabricated inexpensively as plastic sheets or painted on a flexible plastic sheet.
“This is a somewhat futuristic idea, since there isn’t any practical device on the market for doing this, but it has been demonstrated to work in a laboratory,” said Yang. “With enough additional research, I think it can be implemented in the field.”
Perhaps the most futuristic idea the URI team has considered is to completely replace asphalt roadways with roadways made of large, durable electronic blocks that contain photovoltaic cells, LED lights and sensors. The blocks can generate electricity, illuminate the roadway lanes in interchangeable configurations, and provide early warning of the need for maintenance.
According to Lee, the technology for this concept exists, but it is extremely expensive. He said that one group in Idaho made a driveway from prototypes of these blocks, and it cost about $100,000. Lee envisions that corporate parking lots may become the first users of this technology before they become practical and economical for roadway use.
“This kind of advanced technology will take time to be accepted by the transportation industries,” Lee said. “But we’ve been using asphalt for our highways for more than 100 years, and pretty soon it will be time for a change.”
The theory makes this a potential energy source, but the economics of building the infrastructure to realise it won’t be competitive with fossil fuel or nuclear – just like windmills and solar panel arrays.
Cheap energy is the lifeblood of a thriving global economy. In this circumstance history proves that the rich get richer and the poor of the world get better nourished. The reverse always happens when energy prices are high.
My oh my. the infrastructure costs would be staggering. pipes, pumps, semiconductors, all embedded in the road, where you have to dig up the road itself to effect repairs.
that’s the problem with diffuse energy sources: solar, wind, and “asphalt water warmers.” It takes so much infrastructure to “gather” the energy that it quickly becomes cost prohibitive. And no amount of new technological advances will ever make it cost competitive with small, energy dense fuel sources: hydrocarbon, nuclear.
it’s math. you just can’t make 2+2=4. at least not here in real world outside academia.
Zeke the Sneak says:
November 9, 2010 at 2:18 pm
…Maybe we can try sleeping on hot rocks like snakes do.
Hmm! people often misspell my name. I often thought you did yours, now I know.
Winner of junior science project – now on to the real world.
Phil – Interesting read . However , it made no mention of cost effectiveness . From the photos , I would guess that such projects are hellishly expensive and would probably work only in limited areas . For instance , I doubt the viability of such a system in Minnesota .
Charles S. Opalek, PE says:
November 9, 2010 at 3:16 pm
They claim a 50% reduction in energy costs after installing the system. They also say that the paving cost for the section with the piping is about twice the normal paving cost. I don’t know if the system would be cost effective in the US, as Europe has much higher energy costs. I would suspect that they are increasing the efficiency of the heat pumps by leveraging the apparently small delta t of the asphalt collector (about 10 degrees C) to reduce the delta T they would otherwise have to deal with. I have no personal knowledge of this system, other than having read about something like it some time ago, so I can’t vouch for it or the accuracy of their claims.
Source: http://news.cnet.com/8301-11128_3-9838676-54.html
Photo-voltaic cells embedded in parking lots?
Hmm.
What happens when a car is parked in the lot?
Just asking.
You know, these ideas of distributed low level heat sounds real cool until you figure out the cost of trying to aggregate it into something useful comes into play. Other than heating your shoes it’s just not economical.
Doesn’t anybody ever consult engineers.
Why not just use wind turbines? Vertical shaft, blades parallel to the ground, stick them on the sides of tall buildings where they can catch the thermal updrafts. Don’t the birds already use those air currents?
Hey, they’re Wind Turbines, you can get federal money for them, from research to development to deployment!
Here is an idea to get rid of the UHI… built in one big glycol loop under all the streets in the cities and route that to some big heat exchangers in the country side (next to a rural weather station!!). Voila! No difference in anomaly between urban and cities.
Ray says:
November 9, 2010 at 2:23 pm
“My tests showed that during some circumstances, the water even gets hotter than the asphalt.”
Either his pump is heating the water or the zeroth law of thermodynamic is false…
That was my thought as well.
But then I got to thinking: WHAT IF the asphalt is such a good conduction medium that it both gains and loses its heat energy faster than does the water?
If the amount of heat energy transferred to the water was such that the water gained heat while the asphalt lost heat in the process, then it would ~appear~ as he states, but the reality would be that the water was now heating the asphalt.
It’s a thought.
I wonder where the placements were for the thermometric devices?
Well now, I don’t think we should write these guys off so fast…
I used to live in New York and walked every day from Grand Central Station to 9 W. 57th at the bottom of Central Park, rain shine or snow. So let’s do a thought experiment using NY as a model. Hey, we might get a grant!
There are two seasons to consider in our model:
Winter – Just when you need all that solar to melt the snow – It doesn’t show up for weeks! The little that there is, just keeps the slush from freezing into ice and the humans and taxis functional. Thank God for UHI! Drain away that heat to toastify the executive offices of XYZ hedge fund (good science fiction requires the suspension of disbelief in some law, in this case, thermodynamics) and all the people and taxi cabs of NY would be slipping and sliding into one another at a frightening pace. One bunch pumping the heat OUT of the streets for their customers, another dumping more and yet more salt on the roads to keep us all from dying.
Flash forward to Summer
Look down on NY during the Summer. How much pavement do you see lit by the sun? Why, it’s a sea of taxi cabs – all madly absorbing that useful solar energy and they using (gasp) fossil fuels to air condition the gained heat back into the air, making it even more miserable for us pedestrians. SO… if the taxis could be equipped with these new fangled energy collectors in their roofs, it could be sent away to air condition XYX hedge fund’s executive washrooms. Oh wait, cars don’t have wires. Oh wait, no problem – car tires could be impregnated with a conductive compound and each side of each lane could be an opposite polarity contact, using the same compound in the asphalt! YES.
Or, we could just paint all the roofs of all the cabs silver and harvest the gains as less fossil fuel used in the first place.
See, there are answers to these difficult questions…
M in Panama
Wait, don’t scoff. There is merit in these musings.
The eggheads will always bring numbers into the equation. Efficiencies, soo yesterday, RoR yawn, job relocations and that, pesky Canadian Gadfly, SMc is totally uncool when he applies Forensic techniques and logic to the auditing of planet-saving, peer-reviewed studies that prove mankind is as lethal to our planet as DDT is to Malaria.
I like the pizziks
Darn the fingers fumblings of an I-phoner! The point that I, so poorly: tried to make was that the most efficient utilisation of UHI is to point the probes towards the pavement, the parking lot or the air-con.
A billion dollars later, we can still come up with the meme. More research needed. Another couple of Mega$ in the cup boss, and ….
Take a time-out and read this essay: http://www.energytribune.com/articles.cfm?aid=2469
It begins: “Ed. note: A few weeks ago, I had the pleasure of hearing William Tucker speak at a conference in Washington, DC. His explanation of E = mc2 was the best I had ever heard. Even better, Tucker explained how Einstein’s equation applied to renewable energy sources like wind, solar, and hydro. His lecture was a revelation. It showed that the limits of renewable energy have nothing to do with politics or research dollars, but rather with simple mathematics. During a later exchange of emails with Tucker, I praised his lecture and suggested he write an article that explained E = mc2 and its corollary, E = mv2.”
Jonesy and Wang would point out that with only 0.05 degrees UHI, such nonsense will never work.
That’s the trend over a century, not the offset. Cities warm 0.5C more per century than rural areas. But the offset is a different story. Cities are often 5C to 10C warmer than the surrounding countryside.
I just checked the specific heat capacity of asphalt and water at http://www.engineeringtoolbox.com/specific-heat-capacity-d_391.html
For asphalt, it is 920 J/kgC and for water it is over 4 times as much at 4186 J/kgC.
So the numbers do not support the statement, at least with respect to water: “One property of asphalt is that it retains heat really well,” he said, “so even after the sun goes down the asphalt and the water in the pipes stays warm. My tests showed that during some circumstances, the water even gets hotter than the asphalt.”
As has been correctly pointed out by others, water cannot GET hotter than asphalt. Could this have been a misrepresentation of what was meant? Could it have been intended to say that after both had been forced to cool after sundown, the water retains heat longer than asphalt? And could the higher temperature of the water then be used in some productive way?
“Another practical approach to harvesting solar energy from pavement is to embed water filled pipes beneath the asphalt and allow the sun to warm the water. The heated water could then be piped beneath bridge decks to melt accumulated ice on the surface and reduce the need for road salt.”
Just one question for these researchers:
If the sun is not hot enough to melt accumulated ice on the bridge how is it going to heat up the asphalt enough to warm the water in the pipes which is to be piped to the bridge to melt the accumulated ice?
Is there a substance inhaled or ingested at colleges that selectively lowers the IQ of just academics? Something sprayed from low-flying planes or shipped in with textbooks or goods used mostly by professors. Or maybe added to the coffee at the college cafeteria, or combined with their ivy maintenance spray chemicals. “Egghead-B-Gone” (whatever it is) has struck again.
Werner Brozek says:
November 9, 2010 at 7:50 pm
The problem is that bodies in contact with each other must have thermal equilibrium. The only way for the water to get hotter than the asphalt could only be done with some sort of one way insulator that let the heat move towards the water but not the other way around. This sort of material does not exist. The asphalt is in thermal equilibrium with the water and vice versa. If the water is hotter the heat will move from the water to the asphalt. The source of heat is from the top of the asphalt towards its bulk (where the pipes are). It is thermodynamically impossible for the water to become the source of heat unless the pump is heating the water or the turbulence induced by the pump.
I would have thought it would be easier to work on the air con systems of buildings to produce power than wondering around on the roads.
James.
I dont see any reason why every surface and every rooftop in a city isn’t producing power for that city. It makes a whole lot more sense then flattening miles of desert or mountaintops for “earth friendly” solar and wind. Will it solve our energy problems.. probably not unless you have a pwr source that can be easily dialed down and back for times when the wind wont blow or the sun isn’t out. It seemed to me that Portland or Seattle was trying a pilot program very similar, wonder how that ever came out.
Hey All, what do you think about his idea?:
On a crowdfunding site (say like kickstarter.com), start a crowdfunding drive to raise USD1,000,000 in prize money. This prize money will be awarded to the first person or team that can provide conclusive empirical proof showing manmade CO2 is responsible for global warming. This competition will run for 2 years. All submissions will be checked and verified by statistical experts.
Once and for all, let’s settle this global warming argument. At the end of the competition, we will get a conclusive answer one way or the other.
If one million people contribute $1 each or 100,000 people contribute $10 each, we will have the needed prize money.
I love the hope-raising post and love the hope-dashing comments even more.
Of course it’s a daffy, expensive business, this search for alternative energy, but when you consider the potential gain on a long punt…
What exasperates me is the insistence on converting experimental to mainstream without justification. Recently I walked across much of France. I was inspired by the sight of the aging hydro-scheme on the Allier River, and by the long established nuclear reactors on the Garonne. A meeting with a retired geothermal electrician enlightened me on the great usefulness of geo-thermal…and the great limitations of the same.
These industries, the products of daring, independent and practical spirits, were in sharp contrast to the wind-turbines uselessly disfiguring the Aubrac Plateau: perfect symbols of the European Union, where everyone spends everyone else’s money, and everyone thinks everyone won’t notice.
To me, it doesn’t matter if these R. I. guys waste some money on silly lab experiments and sillier pilot programs. They tell me medieval alchemy led to some solid modern chemistry. But every time someone declares an experimental technology to be a “solution”, we start tipping the billions the wrong way. Paradoxically, it’s the people with too much enthusiasm for alternatives who are shutting the door on the future and its viable alternatives.
George E Smith
I think you are being a bit too cryptic in your reference to CARNOT heat engines. The Carnot engine is entirely hypothetical, so is an ideal solution for warmists – they should all get on their Carnot cycles and pedal happily into the sun.
Nevertheless, the subject of heat engines, and in particular the Stirling engine, is relevant to this discussion, as its use is being proposed for use in microgeneration projects and thus could be used to generate power (mechanical and subsequently electrical) as a consequence of temperature differentials between hot asphalt and cooler adjacent areas.
Another alternative is the use of thermopiles, generating electricity directly, providing a more robust solution that PV arrays.