Not sure why but this isn't forming into proper paragraphs...
*"Youtube physics usually is self satisfaction of people that have no clue of the simplest things. So I almost never watch this garbage."* The video is covering the work of a company cascading heat pumps. As such the temperature differential over each heat pump is a fraction of the total over all the heatpumps, there is a potential feedback instability effect they have resolved. But cascaded heatpumps are an accepted thing with improved COP over a given total temperature difference and the video isn't making claims about the second law, that's me, and well Carnot... *"A heatpump is not a Carnot process as you obviously supply additional energy!"* It is a carnot process though and the carnot process gives us the efficiency limit. A reversible heat engine if you supply it with kinetic energy can generate a temperature differential, this is why it is called reversible, you don't get energy from it, you reverse it and put energy in to move heat. To do this you obviously need to supply it with energy just as we do with a heat pump. *"You must calculate in the Carnot conversion rate of energy gained --> electricity to get the proper conversion factor as the current for the heatpump must be produced too and subtracted!"* Yes, however the COP of a heat pump (electrical power in .vs heat energy gain on the hot side) over a low temperature differential can be 5, 10, or 30 or potentially more if the temperature differential is low enough. Note that in a single stage heatpump we can actually double that COP by just counting both the hot and cold outputs as both being beneficial outputs! If a heatpump can deliver four times more thermal energy than the power going in (and for now assuming the heat from the input power is not seeping inside) then wit has a COP of 4, but we ignore the cooling COP of 4 on the other side, that is "free cold" and in terms of a temperature differential to put a heat engine on both are sources of energy, but between the hot and cold sides is a higher conversion efficiency than between the hot and ambient and the cold and ambient. Which is the point I am making, if you divide the heat potential the COP of the heat moving ability of a heat engine or heat pump it improves relative to the energy it takes to drive it. *"The best Carnot process (multi stage turbines) today delivers a conversion rate of about 61% always target is current."* 61% is a fine conversion of heat to to energy since heatpumps can manage a COP of 30! https://www.sciencedirect.com/topics/engineering/recompression COP 30 "typically COP of 10–30 can be achieved" with a MVR heatpump. https://www.gea.com/en/assets/304829/ COP 20 You can have 30 times more heat energy moved and that's just looking at the heat energy gain, ignoring the energy below ambient on the cold side, so with that a COP of 60!... Now granted my whole point is not that this if done with a single heatpump it would not be efficient when you run steam turbines over 1C, 10C or so, so it does not matter how well it was design, because to gain efficiency for conversion of thermal energy we need as great a temperature difference as possible, but there is no reason we can't put multiple heat pumps in series each working over a small temperature range just as we put batteries in series. And we can do the same with heat engines which are just Carnot heat engines under a different name not designed to be reversible but conceivably can be redesigned to be reversible. And again, the point of this post is to point it out from the other direction, according to Carnot if a reversible heat engine can be made more or less efficient (while still not having frictional losses, poor thermal insulation etc) then the second law would fail. And as putting two in series makes it less efficient (as Carnot would himself assert if he had thought if it and apparently he managed not to)... well then the second law fails, it CANNOT be true if this is a reversible heat engine, AKA, a heat pump, as a less efficient heat engine is a more efficient heat pump! That is the message of Carnot's theorem, but another thing of Carnot's is the equation that tells us the efficiency of a heat engine. η = 1 - Tc / Th We take the cold temp in Kelvin, divide it by the hot temp and then subtract the result from 1 then multiply by 100 to get our efficiency in percent. So at -200C on the cold side and -190C on the "hot' side we have, after adding 273.15 K 73.15 K which we divide by 83.15 = 0.8797354179194227 subtracted from 1 gives us a 0.12 which we multiply be 100 to get the percent: 12% efficiency. Interestingly if we drop the cold side to 0.0001 K and the hot side to 10 K we get 0.00001 which subtracted from 1 x 100 gives us an efficiency of 99.99999%! At just 10C (K) difference! Just why the cold side being almost perfectly cold skyrockets the theoretical conversion efficiency... I am not clear on. And this should be called into question at another time, but I wonder if it is related to how hard it is to pump heat from something almost at absolute zero looking at it in reverse? IDK, but whatever. But if we have a more normal temp range for our 10C difference of 15C and 25C then... 25+273.15 = 298.15 and 15+273.15=288.15 So 288 / 298 = 0.9664429530201342 subtracted from 1 then x 100 = 3.4% Ok, staying at a middle temp of 20C... 70C (343K) hot side and 100 C/K colder at -30C or 243 K then 243/343 then subtract from 1 and multiply by 100 for percent and we get 29.15% Ok, so by having 10 times more heat potential difference we have close to 10 times more conversion efficiency at turning heat into energy. And by using 10 heat pumps each just contributing 10C difference between their hot and cold side we have a COP that might be quite high. The heat pumps each feel a mechanical feedback at about the 3.4% level (they have to input in theory 3.4% of the heat they move). 3.4 / 100 That is a COP of 29. So once we have a COP of 29 and the other way we have a conversion efficiency of 29%. Even though this is the max theoretical conversion efficiency at this temperature differential and not a real world value, the potential is clear, we can put in 100W, get 2.9KW of heat and get 29% of that back so 841W out! You can of course go further, but while for practical application the maximum efficiency of a heat engine is important, and putting too many heat pumps in series sounds absurd, we can just focus on the undeniable fact. That there is no way the second law of Thermodynamics is consistent with what we know for an absolute fact. That a heat engine and heat pump (heat engine run in reverse) have VERY different and inverse efficiencies over large and small temperature differences. It is easy (in theory even if expensive) to put 2 or 200 (reversible) heat engines in series to make them less effective as a heat engine and more efficient as heat pumps. And you can still tap the difference between the hot and cold sides to achieve a conversion efficiency in reality of above 50% And as the COP from a heat pump can be VERY high (30 and higher) it's only an issue of making this practical, not a question of if it can be done both in practice and in theory. *"But there have been some materials detected that can improve this further like thermo (Peltier-) elements."* Well it is an interesting point that between every heat pump in the series you could actually put a heat engine (which a peltier is really) and you could get a little energy out, it won't really affect anything (a little heat will be turned into energy but in this case it's not really lost, that which is transferred is meant to be transfered. This allows us to gain little bits of energy, but it is not worth the bother unless there is a suitable difference in temp, if it is 1C it's pointless (but then the max theoretical COP is 274!) the energy from it is negligible. Having said that there IS a way to do it, if you put a bunch of heat pumps in series there is going to be on the hotter half of the heatpumps, after the fluid giving up it's extra heat to the hot side and expanded it is col, likely colder than the ambient. So let’s say we have a hot revivor at 100C (+273.15 = 373 K) and 0C (0 + 273.15 K) so we 273/373 = 0.7319 subtracted from 1 = 0.268 x 100 = 26.8% Ok so 26.8% efficient. But from 100C to 50C we get an efficiency of 13.4% >From 50C to 0 C we get an efficiency of 15.4% For an average of 14.43% with 2 heat pumps in series but 26.8 for 1. This then means the only issue is how many you need given the real world issues. And I'm happy to discuss that, but first let's just basc in the (ironic) warmth of entropy being reversible. Heatpumps are reverse Carnot engines and have a much higher COP in respect to heat gained but *not to current gained!!!!!!!* Even more interesting are quantum level processes in nano particles where one could achieve the doubling of IR photon energy by suppressing some emission bands. This could be used in solar panels. J.W. On Fri, 10 May 2024 at 01:20, Jürg Wyttenbach <ju...@datamart.ch> wrote: > Youtube physics usually is self satisfaction of people that have no clue > of the simplest things. So I almost never watch this garbage. > > A heatpump is not a Carnot process as *you obviously supply additional > energy*! You must calculate in the Carnot conversion rate of energy > gained --> electricity to get the proper conversion factor as the current > for the heatpump must be produced too* and subtracted! * > > The best Carnot process (multi stage turbines) today delivers a conversion > rate of about 61% always target is current. > > But there have been some materials detected that can improve this further > like thermo (Peltier-) elements. > > > Heatpumps are reverse Carnot engines and have a much higher COP in respect > to heat gained but *not to current gained!!!!!!!* > > Even more interesting are quantum level processes in nano particles where > one could achieve the doubling of IR photon energy by suppressing some > emission bands. This could be used in solar panels. > > J.W. > On 09.05.2024 14:39, Jonathan Berry wrote: > > After 200 years (1824) the second law of thermodynamics is disproven. > > https://en.wikipedia.org/wiki/Carnot%27s_theorem_(thermodynamics) > > Simply Carnot argues that if the efficiency of a reversible heat engine > was variable based on how it is made or the gases etc, then the second law > of conservation would be broken. > > "A heat engine *cannot* drive a less-efficient reversible heat engine > without *violating the second law of thermodynamics*." (excerpt from the > Wikipedia article below the image) > > So what happens when you take 2 reversible heat engines and put them in > series (one touches the hot side, one the cold side and they join in the > middle with potentially a small thermal mass that is > thermally equidistant to the hot and cold side)??? > > Well, we know what happens, according to Carnot! > The lower the thermal potential the lower the efficiency at turning heat > into mechanical energy and therefore the less mechanical energy is > developed when driving heat (operating the heat engine as a heat pump)... > Which is to say that with a lower temperature differential a heatpump > operates with more efficiency. > > So a heat engine constructed to act like 2 or more reversible heat engines > will break the conservation of energy. > > There is a company that is making cascading heatpumps which can keep a > high COP over a much larger temperature differential. > https://www.youtube.com/watch?v=wSgv5NwtByk > > The point is that it is absolutely possible to turn uniform ambient heat > into electrical power and heating and or cooling with current technology... > And it is easily explained in a way that cannot be denied, clearly 2 > heatpumps cascading have a higher COP, same as saying clearly 2 reversible > heat engines in series have a lower conversion efficiency and therefor a > higher COP as a hatpump, precisely the scenario that made Carnot assert 200 > years ago would destroy the second law of thermodynamics. > > Jonathan > > -- > Jürg Wyttenbach > Bifangstr. 22 > 8910 Affoltern am Albis > > +41 44 760 14 18 > +41 79 246 36 06 > >
