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.”
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George E. Smith says:
November 10, 2010 at 3:14 pm
“I remember many years ago going to an Electro-Chem Society Convention; and during a session on energy; it was announced that the first Westinghouse reactor to go on line (commercially) had taken 17 years to pay back the total energy capital it took to build;”
You’re probably misremembering what they actually said (unless they got it wrong themselves). Paying back the total capital required to build a power plant is quite different (in this case wildly different) from merely paying back the energy capital. Since energy costs are ~5% of total costs, but energy ~100% of total output of a power plant, there is a factor of twenty between them. And even this includes the whole of the energy consumed for all purposes (including recreational and discretionary) by everyone employed in building and operating it, or receiving any payment or revenue, not merely the energy that is actually required for its manufacture and maintenance. People promoting an energy technology have a tendency to use the latter when they should be using the former; whereas people opposing an energy technology have a tendency to use the former when they should be using the latter. This is why partisan claims are so absurdly divergent. Even for ridiculously expensive technologies (like current wind and photovoltaic technologies) the time for physical break-even in energy is quite short.
“”””” Paul Birch says:
November 10, 2010 at 4:14 pm
George E. Smith says:
November 10, 2010 at 3:14 pm
“I remember many years ago going to an Electro-Chem Society Convention; and during a session on energy; it was announced that the first Westinghouse reactor to go on line (commercially) had taken 17 years to pay back the total energy capital it took to build;”
You’re probably misremembering what they actually said “””””
I believe I said this was the session on energy; I even remember that one of the papers presented in the session was a paper on Gallium Arsenide Concentrator Solar cells; presented by a chap named Jerry Woodall from IBM (who were doing that research). and since it was a session on ENERGY, and not a session on FINANCE, there was no reason for us to be discussing financing of energy plants. The whole emphasis on concentrator cells was for exactly that reason; that you could save a lot of energy capital with concentrator cells; which in the case of Gallium Arsenide would work well with high efficiency, even at 50 suns concentration.
So I remember what was said and what was said about that Westinghouse Reactor; and they weren’t talking about just obtaining the nuclear fuel.
And I have no partisan axe to grind; I care only about the science. And if they can make energy (available) rather than lose energy; then they will succeed economically; and there’s nothing that will stop them unless it is political.
I’m not much in the habit of mis-remebering; and if I do mis-remember; then I also forget to write about it.
“Ray says:
November 9, 2010 at 10:42 pm
The problem is that bodies in contact with each other must have thermal equilibrium.”
True, but what if we had 10 feet of normal asphalt on the SHOULDER of a highway which alternates between 10 feet of something with a layer on insulation at the bottom and then some sort of plastic water filled jugs mixed with asphalt for the next 10 feet? In the summer, everything may be at 140 F during the afternoon but in the middle of the night, the normal asphalt could be 60 F and the alternate 10 feet could be at say 90 F. Could this differential be used to light a street lamp?
Of course the 10 feet with water filled jugs, or whatever, must be able to handle the odd truck that may have to go on the shoulder. And in places where it gets below freezing, antifreeze would need to be used instead of water.
George E. Smith says:
November 10, 2010 at 7:24 pm
“So I remember what was said and what was said about that Westinghouse Reactor”
OK. So then they got it wrong (as I said before) . Whether they realised it or not, they were referring to or basing their statement on total costs (and probably including one-off research costs at that).
“And if they can make energy (available) rather than lose energy; then they will succeed economically; and there’s nothing that will stop them unless it is political.”
No, you’re making the same mistake again; conflating energy with total costs. Energy break-even and economic pay-back are two very different things. You can have either one without the other.
To be economically viable a general purpose utility power plant needs to repay its physical energy input many times over (at least 20 fold and typically of order 1000 fold). Specialised power sources may be viable at much lower ratios – in extreme cases well below unity (cf. primary cell batteries, which deliver much less energy than went into making them, but still sell well for powering electric torches).
“”” Paul Birch says:
November 11, 2010 at 4:28 am
George E. Smith says:
November 10, 2010 at 7:24 pm
“So I remember what was said and what was said about that Westinghouse Reactor”
OK. So then they got it wrong (as I said before) . Whether they realised it or not, they were referring to or basing their statement on total costs (and probably including one-off research costs at that). “””””
Well Paul; when I go to a scientific conference, I tend to start off with the assumption that the speakers do know what they are talking about.. Some times that turns out to be not so; early research is often corrected by later results; but it would appear that you know what they were computing was not correct.
Now all I have to do, is to figure out how you get somebody to do something; for which you have to pay real money; and for doing which, they consume NO energy.
So all we have to do is alter our economy to one which does valuable things at the expenditure of no energy; then our energy problems will be solved; we don’t need any !
Actually, all of my electric torches these days, use rechargeable batteries; and my flashlights too.
George E. Smith says:
November 11, 2010 at 10:42 am
“Now all I have to do, is to figure out how you get somebody to do something; for which you have to pay real money; and for doing which, they consume NO energy.
So all we have to do is alter our economy to one which does valuable things at the expenditure of no energy; then our energy problems will be solved; we don’t need any !”
Oh dear, why do people keep jumping to the conclusion that “less” means “none”? Nobody is claiming that it takes no energy to build a reactor, merely that the amount it takes is small compared to the amount it produces. Some energy is required in the production of all economic goods, as is some material, some capital, some land, some labour. But the relative amounts of each can be varied over a wide range, depending on the relative costs. The optimal production process (for a given time and place) is that which minimises the total cost per unit output – not that which minimises the cost of any one of those factors of production (such as energy) alone.
“Actually, all of my electric torches these days, use rechargeable batteries; and my flashlights too.”
There is still a very large market for primary cells. They are better than rechargeables for torches, unless you use them regularly. Rechargeables tend to have much higher self-discharge rates, which not good for a device that has to work straight out of the cupboard after being left unused for long periods.