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Author Topic: The heatpump, with more energy out than in (FACT)  (Read 59016 times)

Offline infringer

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Re: The heatpump, with more energy out than in (FACT)
« Reply #30 on: July 09, 2009, 04:00:01 AM »
Good info we all know that air can power and someone should look more into these claims...

It would be rather easy generate power with air I would assume...

Excess air interesting concept... if true.

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Offline ATT

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Re: The heatpump, with more energy out than in (FACT)
« Reply #31 on: July 09, 2009, 08:25:05 AM »
.
I don't know if anybody's missing the boat here, but do you understand that when heat-pump COP is published it's just a comparison of the power required for the heat-pump to produce x-btu/h compared to what it would take a resistance heat-strip to produce x-btu/h?

Resistance heating produces 3.41 BTUH per watt (that's inordinately inefficient).

A 1500 watt bathroom heater produces 5,115 btu/h.

So a 3-ton (nominal 36000 btu) heat-pump would be the equivalent of about seven bathroom heaters, which would draw around 10.5KW for straight resistance heating.

With a COP of 5 (COP=Rated BTU/(Unit Watts x 3.41)), the heat-pump should operate around 2.1KW .

The key word here is 'should'. If you hang an Amprobe on it and check the draw, multiplying what you get by 230 will tell the real tale.

Heat-pumps only operate within a restricted ambient temperature range ( > approx 40F ), and continue to de-rate as the ambient temp drops. After that, they kick-in with 2nd-stage (resistance) heat-strips.

They also 'freeze-up' and have to defrost their outside coils from time to time. This is because they are simply a standard air-conditioner with the addition of a reversing-valve (and maybe a receiver and additional metering device), the 'outside' coil in the winter time is what you would consider the 'inside' coil in the summer (the evaporator coil, which is usually running at about 40 degrees cooler that the air flowing over it).

The above is true for air-over heat pumps, geo-source and water-source (which can be used to extract geo-heat) may not encounter the same ambient-temp restrictions, but their output is limited by the environment they operate in, all the same.

Personally, I heat with wood, but here's a comparison of resistance-heat, heat-pump and natural-gas that gives you an idea of cost-efficiency (2009 prices in California are approximate):

BTU/H: 36000

electric-resistance heat:..10.5KWh..@..$0.20/KWh   = $2.10/h
heat-pump:.....................2.1KWh..@..$0.20/KWh   = $0.42/h
nat-gas (36kbtuh bonnet):16 cu-ft..@..$0.02/cu-ft  = $0.32/h

As you can see, electrical-resistance heat is the most cost-inefficient of the bunch and it's actually cheaper to generate your BTUs with gas than with a heat pump, especially since the heat-pump will be in 'defrost' or operating in a de-rated condition a good portion of the time.

Now, if you had a way to produce around 100 PSI+ of air-pressure (with any decent CFM) for free, you could use a Hilsch-tube to both heat and cool your house with no moving parts...all it takes is air...

Tony
.

Offline mscoffman

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Re: The heatpump, with more energy out than in (FACT)
« Reply #32 on: July 09, 2009, 04:53:04 PM »

They also 'freeze-up' and have to defrost their outside coils from time to time. This is because they are simply a standard air-conditioner with the addition of a reversing-valve (and maybe a receiver and additional metering device), the 'outside' coil in the winter time is what you would consider the 'inside' coil in the summer (the evaporator coil, which is usually running at about 40 degrees cooler that the air flowing over it).

The above is true for air-over heat pumps, geo-source and water-source (which can be used to extract geo-heat) may not encounter the same ambient-temp restrictions, but their output is limited by the environment they operate in, all the same.


I think that "ground sourced loop" heat pump would be the only
one to consider over an outdoor free heat sink heat pump for
excess energy generation purposes. This would result in a
"seasonal energy averaging" method applicable to warmer
and moderate climates. One would be using the ground or a lake
or a parking lot as an opportunistic solar energy absorber and cold
sink. If an energy conversion heat pump were ever to operate in
resistive heating mode, then system design would not make sense.

Thank you Tony, It's good to see some real numbers, by the way.

:S:MarkSCoffman

Offline Nabo00o

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Re: The heatpump, with more energy out than in (FACT)
« Reply #33 on: July 09, 2009, 10:30:27 PM »
@Infringer
You should check out the links I posted, ESPECIALLY the one named Equalizer, as this explains the main reason to why we can create much more power only by equalizing two different pressures.
When a large tank with say 6 bars of pressure is filling up a small tank (to make the reduction of pressure in the big tank a minimal) the smaller tank will have a huge increase of temperature, as a matter of fact the increase will be so much the tank needs to be cooled if not risking to explode (because of excessive pressure!). But if allowed to cool and 'equalize' its temperature with the main tank and its surroundings again no increase of pressure will stay there. This is what's so interesting, using sharp gradients of time and power to increase the effect tremendously. The equalizer will in this case be a small tank or just simple pipe which is fitted with two one-way valves and receives an 'explosion' of air inside.

Again you should read that page, I found it incredibly interesting to read, it might just show one of the ways we can change our future into a green and clean world with infinite amounts of power.

Offline Nabo00o

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Re: The heatpump, with more energy out than in (FACT)
« Reply #34 on: July 09, 2009, 10:41:50 PM »
@Tony
Just some years ago I can remember reading a electrician/automatic popular science magazine.
Of the several things discussed there a Japanese heat pump caught my attention.
The scientists who had invented and tested it claimed a COP of 12 in regular conditions and could go far past that in ideal conditions.

One more VERY interesting thing about heat pumps is that they are only used to do one thing, either to cool or to heat something. However, if they are used at both at the same time (cooling one part of the Stirling engine while heating the other ;D) the COP can be doubled.

Now.... Just think about that kind of efficiency....
If a power plant was made, then we would absolutely have used 'optimal' conditions....

Naboo
« Last Edit: July 10, 2009, 01:03:47 AM by Nabo00o »

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Re: The heatpump, with more energy out than in (FACT)
« Reply #34 on: July 09, 2009, 10:41:50 PM »
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Offline angryScientist

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Latent (hidden) heat transfer
« Reply #35 on: July 10, 2009, 12:18:14 AM »
Efficiency is created when the hidden heat or heat of latency of the working fluid is employed.

Quote
Latent : "Present or potential but not evident or active."

[Middle English, from Old French, from Latin latêns, latent-, present participle of latêre, to lie hidden.]


Imagine:

A working fluid as a liquid is introduced to a vacuum. Some where the liquid must find enough energy to reach the boiling point plus the latent energy needed to make the change from the liquid phase to the gas phase. If it fails to find the energy it will remain a liquid.

Increasing the pressure also increases the temperature. It also increases the boiling point. The benefit of a higher boiling point in that the working fluid turns back into a liquid (hopefully) at a temperature higher than the ambient temp. All that heat hidden in the phase change is released to ambient.

The latent heat is not noticed while moving or compressing the working fluid. Only in the phase changes is the latent heat visible as an increase in heat carrying capacity or COP.

Offline Nabo00o

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Re: The heatpump, with more energy out than in (FACT)
« Reply #36 on: July 10, 2009, 01:20:01 AM »
Sorry if this is too straight to the point, but are you saying that the set COP of a certain heat pump is based on an illusion or miscalculation based on the phases of the compression/decompression process and so leads to wrong numbers? I'm sorry if this is wrongly assumed but it was hard for me to understand you correctly, of course I do not have an actual theoretical training in heat pumps and heat machines in general, it is just stuff that I have picked up and learned over the years...

Help me understand   :-\

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Re: The heatpump, with more energy out than in (FACT)
« Reply #36 on: July 10, 2009, 01:20:01 AM »
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Offline ATT

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Re: The heatpump, with more energy out than in (FACT)
« Reply #37 on: July 10, 2009, 01:28:15 AM »
@Tony
Now.... Just think about that kind of efficiency....
If a power plant was made, then we would absolutely have used 'optimal' conditions....

@Nabo00o
Yes, your thread definitely is making me think in a new direction, visa vi heat-pumps.

I pulled a random specification (submittal data for a GE heat-pump) and went through the numbers to actually 'see' what, if any, possibilities there might be.

I coupled this with an Organic Rankine Cycle generator, using data from a very thorough paper on the subject (including parts list and all experimental data) and, even with a COP of 3.0, it looks 'just' doable (disregarding accumulative transitional losses).

Should the (real) COP of an HP be greater than this, and/or the Carnot efficiency of the ORC be greater than 37%, it would be pretty much a definite 'Go' for this idea.

I'd be happy to post the work-up and links to the ORC data if you like, but it's nothing very dramatic, aside from the fact that it shows the viability of your idea.

Tony

Edit:
I just noticed your reply to angryScientist after posting this. Compression is necessary to initiate a change of state in the refrigerant, this compression adds energy to the system and heat to the medium. Therefore, a heat-pump is transferring the 'sensible' heat from the ambient environment and adding what is referred to as the 'heat of compression' to that transfer medium, this is the 'latent' or 'hidden' heat that is only partially available as sensible temperature increase since work had to be done to achieve a change of state.

Does it affect your position on COP? Only if the manufacturer's stated BTU output of the device allows for this. In a strictly 'consumer' sense, I'm not sure if this sort of thing is allowable (elevating a performance characteristic beyond the 'sensible' capacity rating).

As I may have mentioned before, the manufacturer's data has to be 'real' in order to determine the ultimate viability of the idea.
.

 


« Last Edit: July 10, 2009, 01:59:51 AM by ATT »

Offline Nabo00o

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Re: The heatpump, with more energy out than in (FACT)
« Reply #38 on: July 10, 2009, 03:17:47 AM »

Does it affect your position on COP?


No. If the the COP of a given heat pump can accurately describe its efficiency at generating a potential of temperature in a given medium then I believe it is correct.

As for the theoretical bit, asymmetry explains it perfectly. The only reason to why the heat pump can do this is because it is 'not only' compressing and then decompressing its working fluid, it uses its changed state to interact and absorb potential energy from the environment and brake the symmetric change back and forth in pressure, adding and absorbing temperature. This is not about "sneaking" in extra heat from the outside air, it is about changing the way symmetry or balance forces the different potentials to work.

And yeah Tony I would have appreciated it if you could share that data here  :)

Offline angryScientist

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Re: The heatpump, with more energy out than in (FACT)
« Reply #39 on: July 10, 2009, 04:29:29 AM »
Quote
are you saying that the set COP of a certain heat pump is based on an illusion or miscalculation based on the phases of the compression/decompression process and so leads to wrong numbers?
Ya, I'm saying that the extra heat absorbed in the phase change never enters the equation of compression/decompression.

Quote
Compression is necessary to initiate a change of state in the refrigerant, this compression adds energy to the system and heat to the medium.
Compression does add heat to the working fluid.
I want to make it clear that the gas after compression is still a gas but it's temperature is now raised above that of ambient. The gas being hotter than ambient is able to let it's heat naturally flow out into the ambient air.

Quote
Therefore, a heat-pump is transferring the 'sensible' heat from the ambient environment and adding what is referred to as the 'heat of compression' to that transfer medium, this is the 'latent' or 'hidden' heat that is only partially available as sensible temperature increase since work had to be done to achieve a change of state.
That's not quite correct. The latent heat was introduced in turning the refrigerant from liquid to gas. The gas enters the compressor gets compressed and the energy needed to compress the gas is added (a small fraction of total energy carried by the fluid). With the gas (and the energy it contains) compressed into a small space the energy is now dense enough to be considered sensible heat.


You must have the working fluid at a high enough pressure that it will be a liquid if it reaches ambient temperature.

Say that your heat pump was not fully "charged" with refrigerant and could only operate in the gas phase throughout the system. Then you could never achieve a COP greater than 1 because all the losses in the system.

I'll say it again, you must have a phase change on both the high pressure and low pressure sides of the compressor. The amount of latent heat absorbed does not affect the operation of the compressor. The compressor will never ever know how much heat was absorbed in turning the liquid to a gas (and it never will). The compressor only compresses gas. The phase change parts happen wholly outside the compressor.

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Re: The heatpump, with more energy out than in (FACT)
« Reply #39 on: July 10, 2009, 04:29:29 AM »
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Offline ATT

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Re: The heatpump, with more energy out than in (FACT)
« Reply #40 on: July 10, 2009, 05:51:55 AM »
Ya, I'm saying that the extra heat absorbed in the phase change never enters the equation of compression/decompression.

That's not quite correct. The latent heat was introduced in turning the refrigerant from liquid to gas. The gas enters the compressor gets compressed and the energy needed to compress the gas is added (a small fraction of total energy carried by the fluid). With the gas (and the energy it contains) compressed into a small space the energy is now dense enough to be considered sensible heat.

@angryScientist
I appreciate the detailed explanation, you appear to have an excellent grasp of the refrigeration cycle.

At this point, I think the next thing we are wanting to know would be: Is the published heat-output from a heat-pump the actual BTU quantity delivered into the space?

I would imagine that it is, otherwise how could one accurately size a system for a load?

In the commercial world, if it wasn't, it could be grounds for a lawsuit from the Architect, General contractor, HVAC sub and owner, wouldn't you think?

What's your experience with equipment ratings such as this?

Tony
.

Offline ATT

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Re: The heatpump, with more energy out than in (FACT)
« Reply #41 on: July 10, 2009, 08:19:02 AM »
.
@Nabo00o

I found the spec for an HP with a COP of 3.2 to use as an example, but others with a higher COP could be used, this is just the one that I happened on first.
 
--------------------------------------------
GE Zoneline Deluxe Series AZ39H15DAB
14,600 BTU Packaged Terminal Heat Pump Air Conditioner with 310 Max CFM, Freeze Sentinel and Heat Sentinel.
 
Capacity
CFM Indoor Fan High:.......................310
CFM Indoor Fan Low:........................260
Cooling E.E.R. (BTUH / Watt):............10.0/10.0
Dehumidification (pts./hr.):................4.5
Heating - Reverse Cycle - BTUH:........13,400/13,200
Sensible Heat Ratio at 230 Volts:........67%


Power / Ratings
Power Factor:....................................91/92
Voltage:............................................230V/208V
Cooling - Amperes; F.L. - Cooling:..........7.0/7.5
Cooling - Amperes; L.R.:.......................38.0
Cooling - Watts:.................................1,460/1,430
Heating - Reverse Cycle - COP:.............3.2/3.2
Heating - Reverse Cycle - Heater Amps:..5.8/6.3
Heating - Reverse Cycle - Heater Watts:.1,230/1,210
--------------------------------------------


Rated Capacity:
BTU/h (heat)....= 13,400 BTU
Watts (heat)....= (230v x 5.8A) 1334W

1-Watt............= 3.41  BTU per Watt
1/(3.41)...........= 0.293 Watt per BTU

13,400 x 0.2930 = 3926.2W (@ 100% eff conversion)

COP = 3926/1334 = 2.94 (we'll say 3.0)

What this tells us is that at 100% efficiency, we can convert 13,400 BTUs to 3926 Watts with an input of 1334 Watts...now we have to consider losses.

There are several conversion methods to choose from, I decided to try a Rankine Cycle prime-mover for the generator, just to see how it would stack-up.

Rankine-Cycle generators are used in industry to recoup energy that would otherwise be lost due to waste-heat, so they usually use a heat-transfer medium like water or water and ethylene glycol rather than air, as used by the heat-pump described above.

To use water rather than air to transfer the heat off the condenser, we have to replace the original air-over condenser coil with a tube-in-shell condenser. These are available off-the-shelf and will aid us in transfering the heat we need to the ORC boiler-coil.

You might be wondering why we can't just blow hot-air over a can of freon to boil it off, we could, but the losses would be tremendous and the use of water allows for efficient heat-storage, as well as some measure of control for predictable (and constant) expander performance.

One thing, the industrial versions of ORC (Organic Rankine Cycle) generators are geared for 'industrial' size projects and typically run around $50K and up.

http://www.ormat.com

A while back, I found a complete paper on an ORC system in a size compatible with smaller heat-pumps, complete with parts list, specs and test results (University of Leige, 2007):

http://www.labothap.ulg.ac.be/cmsms/Staff/QuoilinS/TFE_SQ010607.pdf

It uses off the shelf components, has good monitoring instrumentation and can be built in a home-shop.

In matching the heat-pump to the ORC, we have to keep two things in mind:
-The ORC has to have the capacity to power the heat-pump.
-The heat-pump has to have the BTUs to power the ORC.

Since I chose this heat-pump randomly, it's not quite a match for the ORC described in the PDF, but it's 'close'.

This is where using the tube-in-shell condenser gives us some lattitude, we can 'store-ahead' to lead the potential heat requirements of the ORC.

If we used this set of components (and they were matched), we'd have this result:

(13,400 x 0.2930) = 3926.2W x .37 = 1452.6W

The efficiency of this particular ORC is 37%

The example heat-pump we're using requires 1334W to run.

Discounting the ORC pump and any unknown cumulative losses, we have a net-gain of 118.6W

That's with a HP COP of 3.0, using a nominal 1-ton HP.

No rigorous matching of HP to ORC was done simply because there are better COPs out there and this is just a thought-exercise to see if there is any viability in pursuing this idea.

On the face of it, it looks like there may be.

Tony
.



Offline ATT

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Re: The heatpump, with more energy out than in (FACT)
« Reply #42 on: July 10, 2009, 06:01:07 PM »
As was mentioned earlier by another poster in this thread, ground-source heat-pumps are probably the way to go for this application.

A good example: WaterFurnace Enviosion GSHP COP of 5.6

This preclude jumping through all the hoops I mentioned in my last post, no need for tube-in-shell exchangers and all that, just get a GSHP water heater.

I'll run-down the data on this heat-pump when I get a minute.

Tony

Offline Nabo00o

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Re: The heatpump, with more energy out than in (FACT)
« Reply #43 on: July 10, 2009, 09:27:01 PM »
Thank you Tony, this was very valuable information indeed!
Another aspect of the process which I think is very important for the efficiency is that instead of creating low volume but concentrated heat and cold, the heat pump should create high volume but low intensity heat, this will mean that the efficiency of the heat pump can be much larger.

The only thing we need then is a way to compress the heat in a concentrated and high temperature that can power the generator.
Also, remember that it is not only the btu's which are important, but also the btu's which it normally would take from the environment, this will also be used to power the cool side of the generator. So theoretically the COP should be the double of normal operation if both the cool and the hot side can be used at the same time, at least that is what I've read.

@ Angryscientist
I understand that you know this subject quite well, but when the total heat which a heat pump can supply is given, and it exceeds the electric power necessary to power it by a ratio which is the rated COP, how then can that be wrong, or something close to miss-information?
Remember, the fact that it extracts energy from another heat source is a plus in this system, so don't use that as an efficiency argument. Else I really want to know how this truly works, if it is just a stupid idea or not.
If it can work it could work really great, especially with the new experimental super-efficiency heat pumps.

Naboo

Offline ATT

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Re: The heatpump, with more energy out than in (FACT)
« Reply #44 on: July 10, 2009, 09:47:03 PM »
A few more direct-conversion of heat to electricity methods:

DARPA statement - 77% is Carnot-Limit
www.darpa.mil/dso/archives/dtec/index.htm

Thermoacoustic - approx 30%:
www.sciencedaily.com/releases/2007/06/070603225026.htm
en.wikipedia.org/wiki/Thermoacoustic_hot_air_engine
www.olemiss.edu/depts/ncpa/BasRes/ThermoIndex.htm

Thermoacoustic - possible 60%:
www.popularmechanics.com/science/earth/4243793.html

Convection (CECC) unknown% alledgedly sidesteps Carnot Limit
www.globalwarmingsolutions.co.uk/convective_energy_conversion_cycle.htm

Thermoelectric - 6-10%
www.technologyreview.com/Energy/21125/

Thermophotovoltaic - unknown%
www.macrovu.com/image/PVT/NASA/RPC/uc%3DThermoVoltaic.v3.pdf

Thermoorganic - unknown%
berkeley.edu/news/media/releases/2007/02/15_heatelectricity.shtml

Thermo-alkali-metal - unknown% alledgedly sidesteps Carnot Limit
findarticles.com/p/articles/mi_qa3864/is_200009/ai_n8926045/

Peltier-Seebeck Thermoelectric - 5-10%
http://en.wikipedia.org/wiki/Thermoelectric_cooling

Thermionics - unknown%
http://www.scienceblog.com/community/older/2001/B/200112962.html

And the list goes on...

Tony

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Re: The heatpump, with more energy out than in (FACT)
« Reply #44 on: July 10, 2009, 09:47:03 PM »

 

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