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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correction, 1st para: “pedal happily into the sunset.”
The ideas described in the article are worth pursuing but as has already been pointed out similar work has been done elsewhere. Phil mentioned an old project in the Netherlands. In Britain, despite our cloudy skies, work is also been done in this field. The article below mentions car parks and school playgrounds as been suitable places for thermal energy storage.
Thermal Energy Storage using ThermalBanks to store heat energy
http://www.icax.co.uk/thermal_energy_storage.html
The idea of storing heat in this way certainly seems more sensible than covering large parts of the British countryside with solar panels – something that is seriously being considered by the government!
Solar mania will cast a shadow over Britain, Daily Telegraph 8 November 2010
http://www.telegraph.co.uk/earth/energy/solarpower/8116609/Solar-mania-will-cast-a-shadow-over-Britain.html
Perhaps the reason for the solar panel idea is to make wind power look good! At least Britain, being an island, tends to be windier than many parts of the European mainland but the idea of using agricultural land to generate solar energy instead is beyond belief.
Going back to the asphalt idea I don’t know why so many people on this blog are keen to rubbish it. One of the most ridiculous criticisms is that if the idea were worthwhile the market would have already exploited it. That argument could be used against any idea.
Whatever you think of the debate about anthropogenic global warming ideas for reducing our dependence on oil, gas and coal, and for exploiting non-polluting sources of energy deserve serious consideration. They do not deserve to be rubbished by cynics who are trying to prove how smart they are.
I’d far rather see money spent in this sort of area than on telling us we’re all gonna fry and it’s all our own fault. At least it is adding to the sum of our knowledge.
Correct me if I’m wrong, it takes as much energy to heat water from 0-10C as it does from 10-100C. If that’s right, it could be very useful.
John Kehr says:
November 9, 2010 at 2:50 pm
My immediate thought exactly – low grade heat is close to useless unless it is very conveniently located near the few things that can actually make use of it.
The idea of running water pipes close to the surface in asphault has so many immediate obvious problems I almost spit my coffee when I read it. Have the morons ever seen asphault roads being paved, repaired, and how they wear under normal use? Almost everyone I should think has seen these things happening and it doesn’t take any skill to imagine how difficult it would be to place and maintain water pipes and how the surface would wear differently. Mind bogglingly stupid.
Then there’s the idea of putting photovoltaics on median dividers to power streetlights and signs. Now there’s a nifty idea but it’s hardly original. I have PV hazard lights on my boat dock to help dipthongs like those featured in the OP avoid killing themselves at night by driving into it. That’s still no guarantee though. Someone last year saw the hazard lights and turned toward shore instead of away from shore to go around it. He zipped right over the ramp from shore to dock in about 12 inches of water. It must have launched his boat about 3 feet high. I’m amazed there was nothing more than some boat paint on my ramp, a bit of bent metal and gouged wood, and a few hefty aluminum shavings from his lower unit where it caught the side of the ramp and kicked up. That must have been one “Holy crap! WTF just happened?” moment for that dope.
Roads get too hot in summer and too cold in winter; so what we want is to transfer the warmth from summer to winter (also day to night). There is ample thermal mass directly below each roadway. The problem is getting enough heat deep enough into the ground. The simplest and most reliable technique may be to ram a grid of heavy aluminium rods (~6cm diameter x ~10m long, hexagonal spacing ~1m) down through the surface – carefully avoiding buried utilities! This would roughly double the depth to which heat penetrates and provide significant mitigation of the temperature extremes, at a cost ~£100/m2 (or ~£5000/person in the urban area). For greater effect additional rods could be added at any time. Being completely passive, they would require no maintenance. This would certainly be an affordable system, but whether the benefits would be sufficient to justify it is another matter; I would be inclined to doubt it. Active systems (such as antifreeze flowing through pipes) could shift more heat, but would likely be a maintenance nightmare, so would probably not have a net advantage over the simpler passive arrangements.
paulhan,
Any place where the water consistently reaches 0 Celsius will also require heating for that same water to prevent the precious pipes from bursting or an evacuation system for removing the water which will require electricity for pumps and a holding tank well below the frost line. In Saskatchewan we do geothermal. You obviously do not live any place where winter turns the dugout into a hockey rink. Then there’s the snow cover to deal with as it reflects a whole lot of sunlight… a new use for carbon soot maybe?
Peter Plail says:
November 10, 2010 at 2:08 am
The Carnot cycle describes the theoretical maximum amount of work that can be produced through a temperature gradient. There are a great many quite real engine designs that use the Carnot cycle. For instance the Rankine and Stirling cycles are pratical implementations of the Carnot cycle.
@Peter Plail (con’t)
One of the great practical limitations in exploiting the Carnot cycle is that efficiency greatly improves with larger temperature gradients. A Rankine cycle engine used in a power plant can get up to about 70% efficient when waste heat is extracted and used for a pre-heater. Nonetheless they still must use dry steam at well over 1000F to drive the turbine.
Theoretically much smaller temperature gradients can be exploited but as a practical matter you need larger pistons or turbine fans as the temperature gradient decreases in order to maintain the same efficiency. Early steam engines used pistons the size of 55 gallon drums (or larger) to get just a few horsepower so an engine the size of a small building only generated as much useful work as a small modern lawn mower engine.
For climate study it’s a different story. A thunderstorm is a Carnot cycle engine that uses just a few tens of degrees F temperature gradient. They work on such a small gradient because the expansion chamber is hundreds of cubic miles in size.
Paul Birch says:
November 10, 2010 at 7:34 am
Where many people go wrong, you included, is failing to take into account the energy required to produce the working parts of the design in question. Producing aluminum is incredibly energy intensive. The commodity price of raw aluminum essentially tracks the price of oil. I seriously doubt whether the energy required to produce the aluminum rods you propose would reach break-even during their service lifetime.
Some people have calculated that the energy required to build a nuclear power plant exceeds the energy produced by the plant over its service lifetime. Nuclear plants require a huge amount of concrete and steel both of which, like aluminun, require a lot of energy to produce and also track the price of oil. If that calculation is correct then the ROIC (return on invested capital) is entirely a matter of the basic stock market strategy of buying low and selling high – i.e. the plant is built with an initial investment of cheap energy when cost of capital is low and over its ~25 year service life it sells energy at a more or less constantly rising price that exceeds the cost of capital invested in it.
I had a great unexpected windfall when the price of oil shot up over the last decade. I happened to have built or purchased a buttload of aluminum, copper, steel, and concrete right around the year 2000 with profits gleaned from selling off my high tech stock portfolio. Little did I realize that in just the course of the next few years the price of those materials would double or triple along with the price of a barrel of oil.
paulhan says:
November 10, 2010 at 4:59 am
Consider yourself corrected. It takes one calorie to heat one gram of water by one degree C. Therefore it takes 10 calories to heat 1 gram of water from 0C to 10C and 90 calories to heat the same gram from 10-100C.
The big energy inputs are in changing one gram of ice at 0C into one gram of water at 0C (334 calories) and in changing one gram of water at 100C into on gram of steam at 100C (2260 calories). Note the temperature doesn’t change at all even though very large amounts of energy are input. These are called, respectively, the latent heat of fusion (melting) and the latent heat of vaporization (boiling). Water is rather unique in the very high latent heat of vaporization which is why steam is used so ubiquitously as a working fluid in various applications involving converting heat to work and in transporting energy from one spot to another.
These same latent heats are also what bedevils climate models as they fail to adequately account for it especially in the heat pump represented by convective cells driven by evaporation at the surface and condensation kilometers higher in the atmosphere.
So the city is warmer Hmmm. well if you extract the heat to make electricity then the homes will need more electricity for heating. There was another project also dumb, but not as dumb, using piezoelectric in the roads, as cars drove by they generated electricity.
Vuk etc. says:
November 9, 2010 at 3:43 pm
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.
@vuk. And Enneagram.
I don’t know where you are getting this snake thing. It’s sneak. S-N-E-A-K.
Of course, for grant money I might like to lay on a warm rock in Cancun, claiming my STUFF is incontrovertible, and hiding my error bars. (No one has ever actually seen me doing it though.) 🙂
Roy says:
November 10, 2010 at 3:16 am
“Whatever you think of the debate about anthropogenic global warming ideas for reducing our dependence on oil, gas and coal, and for exploiting non-polluting sources of energy deserve serious consideration. They do not deserve to be rubbished by cynics who are trying to prove how smart they are.”
Roy, just think about it for 5 minute! It is the pursuit of hare-brained schemes like these that is wasting good money which could be spent of existing technology which is know to deliver, like hydro, natural gas and nuclear. This is were the money needs to be invested if we are to have economic and secure ‘home-grown’ energy supplies for the future.
“”””” Dave Springer says:
November 10, 2010 at 9:22 am
paulhan says:
November 10, 2010 at 4:59 am
Correct me if I’m wrong, it takes as much energy to heat water from 0-10C as it does from 10-100C. If that’s right, it could be very useful.
Consider yourself corrected. It takes one calorie to heat one gram of water by one degree C. Therefore it takes 10 calories to heat 1 gram of water from 0C to 10C and 90 calories to heat the same gram from 10-100C.
The big energy inputs are in changing one gram of ice at 0C into one gram of water at 0C (334 calories) and in changing one gram of water at 100C into on gram of steam at 100C (2260 calories). “””””
And consider yourself corrected also; just a typo I’m sure; but YOUR numbers are more likely Joules per gram; not Calories.
LH of freezing is 80 Cal/gm roughly and about 590 for boiling (at 100 deg C); so your numbers would be in Joules.
Dang ! I have been trying to convert myself from cal to Joules for ages; and there you go giving me the correct nummers.
And this is just a courtesy correction; not a criticism correction; so we don’t pass out incorrect information; those AGW fans, are just waiting for some slipup.
And you’re welcome Dave.
Have any of these people ever had enginnering economics or experience with detailed Life Cycle Cost Analysis? The LCCA for these projects are excessive in the very best case. Research for research sake is great, but leave the applications to engineers and scientist that have to sell this to their clients.
“”””” Dave Springer says:
November 10, 2010 at 8:15 am
Peter Plail says:
November 10, 2010 at 2:08 am
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
The Carnot cycle describes the theoretical maximum amount of work that can be produced through a temperature gradient. There are a great many quite real engine designs that use the Carnot cycle. For instance the Rankine and Stirling cycles are pratical implementations of the Carnot cycle. “””””
Dang ! and here I thought I had created a really sexy name for something; and you chaps tell me someone else already used it; what a pity !
But Peter; What is this all about ? “””your reference to CARNOT heat engines.””” Can you point me to my reference to “CARNOT heat engines ” . Only thing even close I could find was this :-
“”””” I would call it the “CARNOT” Energy source; has a sort of norty connotation to it; should really sell !! “””””
Now I think that a “heat engine” might require an “energy source”; but I wouldn’t say an energy source was a heat engine; and it looks like I didn’t.
Sometimes it is really hard to find words, that are simple for people to read; maybe everyone is texting so much that nobody even bothers to read any more.
But thanks for the hint on that Carnot thing; maybe I will look it up.
Has someone offered a new multimillion dollar X-prize that I haven’t heard about? From the tenor of a multitude of recent press releases it would seem that something has seriously incentivized the academic community to come up with schemes to generate the world’s most expensive Btu or Kilowatt. If Prof. Lee’s class of engineering students took more than a half hour to come up with at least 50 reasons why this project was a complete waste of time and resources, he really ought to give back his paycheck.
As an alternative I suggest we recruit a bunch of homeless guys, station them on bridge decks with sacks of currency and Bic lighters and have them sprinkle any ice that appears with flaming bills. If we restrict the denominations to 10s or 20s it should be just about as economically sensible as this scheme.
Dave Springer says:
November 10, 2010 at 9:04 am
“Where many people go wrong, you included, is failing to take into account the energy required to produce the working parts of the design in question. Producing aluminum is incredibly energy intensive. The commodity price of raw aluminum essentially tracks the price of oil. I seriously doubt whether the energy required to produce the aluminum rods you propose would reach break-even during their service lifetime.”
I have not “failed to take into account the energy required”. That is automatically included in the cost I gave. Since the technique is intended to ameliorate temperature extremes, not generate power, the notion of energy break-even has no relevance. You might just as well ask whether a television set reaches break-even. Nor, as totally passive objects, would the rods have any “service lifetime”; they’d last for thousands or even millions of years. For what it’s worth, such rods could be expected to transfer the quantity of energy required to manufacture them in roughly 100 years.
“Some people have calculated that the energy required to build a nuclear power plant exceeds the energy produced by the plant over its service lifetime. ”
Nonsense. Energy break even should take a few days’ operation at most.
@Dave Springer, @george E. Smith
Thank you both very much. I stand corrected :-). If George E. Smith’s figures are correct, then to go from freezing to 10C and 10C to 100C would take the same amount of energy, but I hold my hands up, I meant it the way that Dave interpreted it.
Paul Birch,
Why not just use existing ground source heat pump technology instead of the rods?
Djozar says:
November 10, 2010 at 12:53 pm
“Why not just use existing ground source heat pump technology instead of the rods?”
Because passive rods don’t require maintenance. Heat pumps, with fluid filled pipes, would be difficult to engineer with adequate reliability (think of the hammering the road and its substrate gets from heavy traffic).
Problem: Roads freeze at night.
Heat source: Sunshine.
Heat storage device: Water
As Werner Brozek’s comment pointed out the specific heat capacity of water is four times that of asphalt. So any road engineer with a little spare cash can place plastic food containers of water (they don’t have to be pipes) under the road surface, and close enough to the surface to pick up some of the daytime warming and release it at night.
Loads of savings on gritting lorries. (The engineer won’t save on snow ploughs because no warmth is going to melt the amount of snow that needs a snowplough, and hey – if it’s snowing the road isn’t black anymore and will not absorb heat during the day!)
This is easy, cheap stuff. But hang on! The road will collapse under the first lorry unless we start to engineer these containers out of steel. Rust-less steel. And the road must stay absolutely flat – not settle around these containers as the asphalt consolidates.
Oops – so now it’s starting to look expensive. It’s starting to look like every long road has to be constructed to the same engineering standards as a short length of bridge.
So we’ve established this is a non-starter. Next !
Surely the KISS principle still applies, even to these junior school scientists?
“””” paulhan says:
November 10, 2010 at 12:43 pm
@Dave Springer, @george E. Smith
Thank you both very much. I stand corrected :-). If George E. Smith’s figures are correct, then to go from freezing to 10C and 10C to 100C would take the same amount of energy, but I hold my hands up, I meant it the way that Dave interpreted it.
Say Paulhan; I think maybe some information got lost in the shuffling.
When you say going from “freezing” to 10 deg C; you should be specific about “which side” of freezing you start from.
Ye; IF you start from x grams of ICE at the freezing point (zero deg C) then it will take 80 Calories per gram; just to go to the OTHER side of freezing; aka ice water and then ten more calories to get you to 10 deg C or 90 Total, and then 90 calories more would take you to the water side of boiling at 100 deg C.
So if you meant starting from ice at zero and ending at water at 100, then you are quite correct; the half way point heat wise is at 10 deg C.
Dave just got his Calories and Joules flipped; but that can happen to anyone.
I think the boiling water to Steam transition is even more dramatic; sicne the latent heat is 590 Cal/g at that phase change; so steam at 100 deg C contains seven times as much heat as water at 100 deg C; which is why steam burns are so deadly. You get a gram of steal at 100 deg C on your skin; and it dumps 590 Calories immediately and then another 63 calories as it cools down to body temperature (37 deg C).
I think it is less confusing if you keep the latent heats at phase changes separated from just temperature changes.
But you were right if you meant from ICE to boiling WATER.
“”””” Paul Birch says:
November 10, 2010 at 12:29 pm
Dave Springer says:
November 10, 2010 at 9:04 am
………………………………..
“Some people have calculated that the energy required to build a nuclear power plant exceeds the energy produced by the plant over its service lifetime. ”
Nonsense. Energy break even should take a few days’ operation at most. “””””
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; If I remember correctly they were just in the process of refuelling it; and they figured it had another 17 years of service life; before it would be just too costly to maintain.
Maybe they have gotten better since then.
You have to start with ALL of the raw materials being in their natural state ; presumably somewhere on planet earth; and that of course includes whatever equipment and machinery you need to mine those raw materials, and process them, and use in the construction; all of which will get pretty much consumed by the time the project is finished.
We know that stored chemical energy is viable; since that is what got us to where we are today; manual labor would never have done the job.
“”””” Correct me if I’m wrong, it takes as much energy to heat water from 0-10C as it does from 10-100C. If that’s right, it could be very useful. “””””
So Paulhan; the way you actually stated the problem; you didn’t have it correct; you said to heat WATER, not ICE.
I’m sure that you just misread whatever source you originally learned it from.
From ICE to boiling WATER; yes.
From ice WATER to boiling WATER; no
From ICE at zero to STEAM at 100 definitely not.