yes it does. The choice to use inefficient lighting systems indicates that they intentionally made that system a dual lighting heating system. And It has a central cooling system which won’t ever be needed to operate as a heater.
Did it work out ? perhaps the technology was too fragile for wearing, and only works in at times when there is snow on the ground ? (it needs the higher temperature difference to make any power.)
You might have insight into a broad range of questions like this by reformulating your mental image of where useful work comes from in a heat engine. A flow of heat from the hot source to the cold sink is being partially diverted to produce useful work, just as a flow of water downhill can be tapped by a waterwheel to produce useful work. But notice a waterwheel requires a source of water above it, and a place for water to go below it. You can’t put a waterwheel in still water at high or low altitude and extract useful work. You have to put it between water at high and low altitudes. Similarly, a heat engine requires both a place from which the heat flows (the heat source) and a place to which the heat flows (the cold sink). Without either one, no heat flows and no work can be extracted.
From that point of view, you can easily see that you may regard the “origin” of useful work in a heat engine as the cold sink, if you like. That’s just as legitimate as regarding the origin of the work as the heat source. Without the cold sink, heat doesn’t go anywhere and no work can be extracted.
In the case you mention, where is the cold sink? To where is your waste heat supposed to be induced to flow? For the most part, the essential nature of waste heat is that it is at nearly the same temperature as the surroundings. That’s what makes it “waste.” That means in order to extract useful work from it, you need to find a cold sink at a significantly lower temperature than ambient. Needless to say, that’s unusual, and it’s hardly economical to construct one for the purpose.
The role of the cold sink tends to be overlooked because we use the ambient atmosphere for it, most of the time, and therefore need the heat source to have a much higher temperatue than ambient. But every now and then people think: hey, even at or near ambient temperature, there’s a lot of heat energy in things. Why can’t it be used? Well, the lack of a cold sink – but that requirement usually escapes them because they didn’t notice its important to the typical heat engine (car, power plant).
A famous case of this error is called the “Zeromotor,” a brilliant perpetual motion machine of the 2nd kind that fooled a lot of people many years ago.
The only thing I can think of where “waste” heat is put to useful work is in combined-cycle power plants. Primary power generation is by a natural gas-fired gas turbine, and the heat expelled by that heats water to run a steam turbine.
Once the cost of energy and makes the capital investment worthwhile it happens.
In my town we are now using the waste heat from the crematorium to heat the water in the nearby swimming pool; both are operated by the Town Council. A factory near my house makes zinc castings. The machines have to be cooled and the waste heat not only heats their building, but their two neighbours in winter. They are now looking at ways to utilise it in the summer - maybe to generate electricity.
Any large, newly-developed building will use assorted equipment connected through a hydronic network to maximize energy efficiency when managing the internal environment. Hospitals are the best example, as they are quite complex environments: Patient rooms, offices, restaurants, laboratories, computer rooms, retail spaces, enclosed vehicle spaces, classrooms (some hospitals), etc, with those spaces each placing specific demands on the overall system.
Excess heat generated in one part of the building is transferred (through heat recovery chillers and/or heat pumps) to areas that can use that heat. Usually, the cooling load and heating load do not balance out perfectly and the overall building imbalance is rectified by rejecting/recovering heat to/from the outdoors through coils, dry coolers, etc., when possible.
When it’s really cold outside and the people, computers, and equipment simply don’t generate enough heat to keep things warm enough, the boilers kick in.
Really, it’s not unlike a complex reef tank: Keep all the little critters, each in their own sub-environment, alive, happy, and healthy.
It’s all computer-controlled and monitored in real-time so as to minimize the instances of, say, blowing -30 °C air into the neonatal unit. It’s so advanced nowadays that one can literally manage a hospital’s entire climate control system from an iPhone.
In a stirling cycle external combustion engine, the vapor exhausted from the motor passes through the liquid that is enroute to the heater, exchanging its heat and raising the temperature of the liquid so that less heat is needed to boil it. They can be very efficient compared to other types of engines.
Presumably, thermocouples could produce electricity from waste heat, if you use enough of them, but you have to send that heat elsewhere for them to work, so at the very least, some of their output would probably have to be used to drive the cooling system.
Well, a turbocharger basically uses waste energy from the exhaust to operate a compressor that increases the density of air that enters the engine. Since you can cram more air into the cylinders, you can burn more fuel, and this allows you to build a smaller engine that produces the same peak power output as a larger one. If the engine is mostly operated at low loads, as most car engines are, the smaller engine can be more efficient than the larger one because pumping and frictional losses are lower.
This is becoming a very popular mechanism for improving fuel economy in modern cars. For example, Ford has been very successful developing and selling a turbocharged V6 in their F150 as a more-efficient alternative to a V8 that delivers the same power.
Wait? What? I can’t quite grasp where heat is moving here and where you’re extracting energy.
Thermopiles (large collections of thermocouples in series) can be used to generate electricity from heat energy without mechanical motion (e.g. not a thermodynamic “heat engine”) via the Seebeck effect, but the amount of energy produced is generally trivial in comparison to the complexity of the system. However, with nanomaterials with very low resistivity and large effective surface areas, recovery of so-called waste heat may be a practical power source for nanoscale devices, or to power low powered macroscale devices via nanothermoelectric supplies.
In general, the temperature differential of waste heat is just too low to recover useful work, hence why the energy is considered to be “wasted”, but as others have noted, the energy can be used to heat the ambient environment or recovered for cogeneration, albeit with a cost of greater complexity of the system. This is gernally only practical with large, fixed facilities such as buildings or power plants where the amount of heat energy is large despite the modest temperature differerntial. Devices powered from, say, the waste heat of a human body (especially internal medical devices such as pacemakers) are desireable but very challenging as the absolute amout of heat energy available is pathetically small compared to typical power requirements.
Stranger
I understand how extracting energy from the flow of heat works. I was reacting to this part of the statement “but you have to send that heat elsewhere for them to work, so at the very least, some of their output would probably have to be used to drive the cooling system.”, which to me reads a lot like “To keep the temperature differential high enough we use some of the energy to cool the heat sink.”
One of our houses has a gizmo that uses the waste heat from the AC to pre-warm the water going into the hot water heater. It’s not uncommon.
For a heat engine, the heat energy does have to flow from a high temperature source to a low temperature reservoir (heat sink), doing mechanical work in the process. In the case of the Seebeck effect, the heat transfer between dissimilar metals results in an organization of charge and net flow of current. There is still a requirement for a high temperature and low temperature reservoir (“Thermodynamics – It’s the law!”) but there is no mechanical work being done. If, for instance, you were using a thermocouple to measure the temperature of boiling water, your measurement bridge or meter has to be outside the water in a cooler environment, otherwise there is no net current or flow of electrons. So you can’t generate energy from the ambient environment without a cooler reservoir to reject the lower energy “waste heat” into.
It is worthwhile to note that it is impossible to “create” a heat sink. Any effort you make generates heat, so you can’t just enclose a volume and push all of the heat out of it without having somewhere colder to push it into. The way heat pumps and the like work is to take some existing volume of fluid with an ambient energy level, pump some of the fluid up to a higher temperature, and then reject it into a lower temperature reservoir. But in order to do so you still need a cold temperature reservoir to reject heat from all of the work you are doing on the fluid. Cold temperature reservoirs are a natural resource, and one that is ultimately limited by the background temperature of the universe (cosmic microwave background). We can make colder sinks but only by increasing the average temperature somewhere else.
Stranger
An once again I’m no closer to grasping what eschereal was intending to say.
As has been said, most times the only reasonable thing to do with waste heat is to use it to heat something you want heated. So if you’ve got a refrigerator that makes cold water and a water heater that makes hot water you can use the waste heat from the fridge to preheat the water. Just like you use waste heat from your car engine to heat the passenger cabin of your car on cold days. But on hot days when you want to cool the passenger cabin of your car you need to run your engine even harder to run the AC.
I think you got it. If you want to create a temperature differential to do useful work with waste heat, you end up impeding the operation of the primary machine, or having to add a cooling mechanism for the heat sink, etc.
this is not a bad idea; the A/C condenser needs to be cooled anyway, and since it takes an enormous amount of energy to raise the temperature of water, a little “head start” doesn’t hurt.
True, but it’s important that the desuperheater is used just for pre-heating rather than trying to handle all the water heating, because otherwise it will run the a/c system excessively and blow away any potential savings. This usually requires a two-tank system, with a pre-heat tank that’s “cool” enough for the desuperheater to dump its heat into. That tank might be kept at between 80 and 90 degrees and is connected to the cold water supply. That tank then feeds into the main hot water storage tank that has booster elements to get it up to 120 degrees before sending it out to the house.
Another option is to have a buffer tank that then feeds an instantaneous water heater. They require less electricity/gas to produce the same amount of hot water when the inlet water temperature is higher. Even if you had smaller instantaneous heaters scattered around the building at each use point (to minimize time for hot water to reach the faucet) the booster tank would ensure that the inlet water temperature was always at least as warm as the building, rather than the 40-60 degrees it is coming out of the ground.
I meant that you must somehow drive off the heat on the cold side, because, AAUI, thermocouples do effect a heat transfer through the body of the device. Or, for instance, if you have the cold side in the river, you have to pump the waste heat to the hot side (though there are heat pipes that could, in theory, do this more or less for free).
We’re missing a simple rule here.
Think in terms of absolute temperature. If you can let heat flow from a high temperature to someplace cooler where the temperature is x% of the high temperature, then, at a bare minimum, x% of the heat must remain in energy form of heat, and only (100-x)% of the original heat can be converted to another kind of energy – and that is a hard and fast maximum, which real heat engines can only try to approach.
If something is 6 degrees C above room temperature, its absolute temperature is 299 K and the heat gets to flow to 293 K, which means 98% of the original heat energy must stay in the form of heat and only 2% is accessible for conversion to some other form. At the very best.