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Re: reverse cycle air conditioning heating is more efficient??


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We are being serious. Of course you can't get energy for nothing, or
get more energy out of something than you put in in total, and nobody
is claiming that is the case.
The thread is about reverse cycle aircons, and they *are* more efficent
than electric heaters for what they are designed to do, and they *are*
rated in kW of *heat energy* that is greater than the electrical energy
in kW put into it.
There is a big difference between kW of heat energy and kW of
electrical energy.

Dave :)


Re: reverse cycle air conditioning heating is more efficient??


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Where does stealing come into this? As far as the sun is concerned, the heat
and light energy is free for all and any to use. So, in your idea, plants
steal the energy to grow?
Yes it is a finite scource, but no one will be around to see that energy
disappear. When this energy is utilised, it is still free,  the only cost,
as I have stated, is the cost of extracting it for our needs.
 



Re: reverse cycle air conditioning heating is more efficient??



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OK, instead of quoting faint memories i decided to pull out the uni
books and dust them off. Seems I was right, so i decided to hound
wikepedia for some quotes.

First is

http://en.wikipedia.org/wiki/Second_law_of_thermodynamics

which is a full of mathematical formula, so not so easy to read.

Next is my physic book from first year eng. @ QUT, Serway & Beichner.

This is a direct quote:
In a refrigerator or heat pump, the engine absorbs heat energy from a
cold reservoir and expels energy to a hot reservoir. This can be
accomplished only if work is done _on_ the engine. From the first law,
we know that the energy given up to the hot reservoir must equal the
sum of the work done _and_ the energy absorbed from the cold
reservoir. Therfore, the heat pump transfers energy from a colder body
to a hotter body. In practice, it is desirable to carry out this
process with a minimum of work. If it could be accomplished without
doing anywork, the the heat pump would be 'perfect'. Again, the
existance of such a device would be in violation of the second law of
thermodynamics, which in the form of the Clauius statement states:
    "It is impossible to construct a cyclic machine whose
    sole effect is the continious transfer of energy from one     
    object to another object at a higher temp without the
    input of energy by work"
In simpler terms, *energy does not flow spontaneously from a cold
object to a hot object*

Serway & Beichner then go on to provide examples of how to calculate
thermal efficiency then go on to further describe the theoretical
carnot engine (which is the most efficient engine).

SO I went on to check the second law efficency, and find that
wikepedia describes exactly what i described here:
http://en.wikipedia.org/wiki/Exergy_efficiency

"It should be noted that the energy efficiency quoted by appliance
makers is the "first-law" thermodynamic efficiency; it only tells one
how well the particular appliance converts one form of energy, usually
electricity, into another, usually heat. It does not tell one how the
appliance compares to, say, a Carnot heat engine or any other cyclical
process."

Folow the link to:
http://en.wikipedia.org/wiki/Thermodynamic_efficiency
 we see "The thermal efficiency () is a dimensionless performance
measure of a thermal device "
and
"Heat pumps, refrigerators, and air conditioners, for example, move
heat, rather than convert it, so other measures are needed to describe
their thermal performance. The common measures are the
Coefficient-of-performance (COP), Energy Efficiency Ratio (EER), and
Seasonal Energy Efficiency Ratio (SEER).
"
Which i think someone else described.

LAst but not least, this sums it all up very well
http://en.wikipedia.org/wiki/Heat_pump


So to claim that a reverse cycle air con is 500% efficent is not true,
but rather if you were to say that it were 500% more efficient
relative to a resitive element, then you are probably right.




Re: reverse cycle air conditioning heating is more efficient??


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Could have sworn I said that a few posts ago ;-)
http://groups.google.com.au/group/aus.electronics/browse_frm/thread/e59e50ca3137b39b/1b613c22f65eb10d?lnk=arm&hl=en#1b613c22f65eb10d

Dave :)


Re: reverse cycle air conditioning heating is more efficient??



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Cant you read? That's what I said, without writing a novel about it..
The suns energy is free. The only energy required is the energy to make it
useful.
Argue all you want, the facts are the facts. The sun was given to us to
utilise any way we want.
I dont care who created which law or rule, the suns energy id free.

Prove me wrong!




Re: reverse cycle air conditioning heating is more efficient??



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What I am proving here is that no matter what you do it is not
possible to have a heat pump that is more than 100% efficient.
Therefore the energy in your home is not free, its provided by using
energy to move energy. Sum total = more in than out. My response was
not directed specificially at you, more so at the posters claiming
that heat pumps can be greater than 100% efficient.

Re: reverse cycle air conditioning heating is more efficient??



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Food and water was free once too, until they found a way to charge people
for it.
In fact they already charge for solar energy when it's added to the
electricity grid.

MrT.





Re: reverse cycle air conditioning heating is more efficient??


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Food and water is still free if you grow it and capture it yourself.

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It's still free if you have your own solar cells, solar air heater,
solar hot water or whatever ;-)

Dave :)


Re: reverse cycle air conditioning heating is more efficient??



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Please let me know where you get the "solar cells, solar air heater, solar
hot water or whatever" free?

MrT.



Re: reverse cycle air conditioning heating is more efficient??


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Just *how* did I know you were going to ask that!

Of course they are not free, but there is this thing thing called a
payback period, perhaps you've heard of it?
Once that payback period is over the suns energy is FREE.

Dave :)


Re: reverse cycle air conditioning heating is more efficient??



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solar

Because it was so obvious blind Freddy would have expected it?

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Yes, and someone else calculated his payback period is after his death. :-)
But in fact they will probably need replacing before then, so back to square
one!
It's like the greenies claiming trams and trains are non polluting, whilst
screaming that brown coal power stations are filthy polluters :-)
There is a reason why all power is not generated from solar, it's still
uneconomical at current costs.

MrT.



Re: reverse cycle air conditioning heating is more efficient??


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Food costs us money because people (ie farmers) have to put a lot of labour
into bringing it to market. No argument. If you want to complain about what
we pay for food, complain to woolies and coles.

Water, well, there is the biggest government rip off known to man. We were
told we had to pay for water until the drought was ended (in the eighties).
The drought ended and they are still charging for water. This is the best
example of legalised theft that exsists. Water costs absolutely NOTHING.
There is nothing wrong with charging us for the delivery of water, but to
charge for the water itself is a precursor to charging for the air we
breathe.
As a result of water charges, the water authority are the largest landowners
in the country.

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Hah! That is another government rip off. All those greenies pay extra for
their power bills for the same power normal people know is no different. If
it's on the grid, the same power goes to every household, call it what you
like.



Re: reverse cycle air conditioning heating is more efficient??



"Phil in Melbourne"
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**  The "heat pump" technique works for water heaters too:

http://www.solco.com.au/products/solco_water_heaters/solco_revolution


What a * warm *  idea  !




.......   Phil





Re: reverse cycle air conditioning heating is more efficient??



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**Yeah, I thought about that one too. I also looked at Solar hot water,
heating, until I got the quotation. My average hot water bill is around
$18.00/quarter. At that rate, it would take around 75 years to payback the
cost. I figure with a $18.00/quarter hot water bill, I'll leave well enough
alone. My figuring is this: At the old place I had an outdoor 210 Litre off
peak system. It cost around $70.00/quarter. I now have an indoor, 420 Litre
off peak system and my bill is less than $20.00/quarter. I figure the
efficiencies from being indoors and the fact that there is less surface area
to radiate heat from puts me well ahead.


--
Trevor Wilson
www.rageaudio.com.au
 



--

Re: reverse cycle air conditioning heating is more efficient??


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Quantum Energy are another Australian company doing hot water systems using heat
pumps instead of rooftop panels.

http://www.quantum-energy.com.au /

I always thought it would be neat to have a combination heat pump/rooftop panel
system, but I haven't seen one of these yet.

Re: reverse cycle air conditioning heating is more efficient??



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Er NO. Efficiency is power out divided by power in. You forgot the power in
contributed by the sun in your calculation!

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See, now you remember :-)

MrT.



Re: reverse cycle air conditioning heating is more efficient??



Mr.T wrote:
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No, I didn't forget, I deliberately left it out!

I put in 25W of electrical energy and I get out 500W of heat energy.
The sun is free ;-)

Dave :)


Re: reverse cycle air conditioning heating is more efficient??



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    Only because the politicians haven't figured out a way to tax it
....  yet.

Bob



Re: reverse cycle air conditioning heating is more efficient??


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Only after John  Howard has figured out how to sell it.



Re: reverse cycle air conditioning heating is more efficient??



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in

Which of course was your mistake when calculating efficiency rather than
running cost!

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But you made no calculation of cost, only efficiency!

MrT.




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