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Wind turbine heat pump - Page 8

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Posted by markzoom on February 24, 2007, 8:15 pm
 

Glad you're having fun.


That's why I asked for "experts" to comment.


I weigh up the comments made.
The bottom line is that a wind generator driven heat pump WILL give
more heat output than an electrically driven one, with the added bonus
of providing refrigeration and needing FAR FEWER COMPONENTS than an
expensive electricity generating turbine driving an expensive electric
air conditioning unit.



You do that. The rest of us can see the vast scope of an efficient
wind driven heating unit.



Posted by RamRod Sword of Baal on February 24, 2007, 11:19 pm
 


=======================

You can see what ever you want, that does not make it correct.

A few facts of life..

An electrically driven (sealed unit) puts out more heat in a heat pump
operation than a open (belt driven) unit, as the heat from the electric
motor is included in the output, simple as that.

For instance a 2 Hp motor uses around 1500 watts of power, that is over 4500
BTUs and in a sealed unit heat pump this is picked by the refrigerant and
can be collected for the heating process.

You cannot drive any old compressor at any speed you want, why, because the
oil pump will not supply oil to the various parts if the speed is not fast
enough, that goes for sealed units or open units (belt driven) which
includes automotive compressors.

If any compressor is driven too slow, it will seize up through lack of
lubrication.


-------------------

While talking in general about the possibility of using a wind turbine to
drive a compressor to run as a heat pump, has anyone any idea just what size
a windmill would need to be to turn such a thing, it would be very large, if
not huge.

It would pose certain engineering problems to get a compressor (belt driven)
to start at a certain windmill speed, and stop before the speed fell too low
so that the compressor lubrication would fail.

There would be a minimum size limit on such a system because of heat losses
in the pipework etc which would have to be overcome before any useful heat
for heating is obtained, so some micky mouse size system is not an option.

Heat pumps in a sealed unit situation (which means they have the heat from
the motor) breaks even generally around 45 f with resistance (element)
heating, below 45, they are LESS efficient than electic elements.
 IE the more heat outside the more efficient they become.

Below 45 F ice forms on the outdoor coil and heat pick up is hindered by the
insulation on the pipework by the ice. I am sure with clever engineering
this could be lowered a little, but here we are talking generally about
unskilled people trying to engineer  build problem such a device.......

In well designed heat pump systems, below 45 f de-ice circuits are brought
into service to control this icing problem, which would be difficult on a
straight out heat pump operation unit wind driven device. These de-icing
circuits do tend to keep the coils somewhat free of ice, but reduce the
overall heating effect obtainable. IE when the go onto a de-ice cycle, then
while on this operation, no heat is available for the conditioned space.

Not a problem with a well designed system, as you can bring addition heat on
in the form of electric elements during this period, or have a larger than
required unit to help overcome this problem.

Anyone considering such a system must be advised that you would have to
think of fans to drive the air over both the heating and coiling coils, or
they would become really huge.

I have seen where someone tried to use a static condenser (one with out a
fan) on an air conditioning system. It was a 2 hp sealed unit system and the
condenser coil was 6 feet long, 2 feet wide and 5 inches deep, the condenser
coil came from a 50,000 BTU condenser originally and there was no way it
could handle the 20,000 or so BTU output of the 2 HP compressor without fan
assistance. They even tried water sprays to help, but it did not work.

The cost would be prohibitive for such size coils.

=================



Posted by markzoom on February 25, 2007, 12:56 am
 wrote:

Already said so, which is why efficiency would be "only" twice input
power.


I know.


OK, so I'll use one that can.

You are forgetting oil-less compressors.


??? Heat pumps come in any size. A 500 watt turbine would run a
heatpump that would require a 500 watt motor, more or less.
Why would you want to use an air compressor instead of an HVAC
compressor?


No. Car air conditoning systems run at any speed up to maximum as
someone said previousy.


An average fridge only uses about 100 watts intermittantly.
Refrigeration is quite a large expenditiure on annual energy bills.


Good point. (As it happens where I am, it never goes below 10C at
night).
In places where it goes below 7.2C (45F), it would probably only be
any use as part of a ground source system.



Interesting.
As you point out, below certain temperatures heat pumps as heaters
appear only useful as part of a ground source system.
There is still the other side of the equation, cooling in hot
climates.




Posted by RamRod Sword of Baal on February 25, 2007, 2:58 am
 

Let me know when you find one, as working in the industry for around 40
years and I have yet to see one.......


No, tell me where you can get an oil-less refrigeration compressor.

The only air-less compressors I have heard about are air compressors, and
they certainly would not be suitable for use in a refrigeration system.




Do you ever read before you type, never have I mentioned air compressors,
the types I have mentioned are sealed units, belt driven and automotive
compressors, which of course also fall into the catogery of belt driven, all
of which are refrigeration compressors.

So heat pumps come in all sizes, like to show me an ad for one that is 500
watts?

Are you trying to say that you would put all the cost and effort into
building a heat pump system that would only need 500 watts to drive it?

The amount of heat you could collect would not be worth the cost or effort.



Wrong, they do not run at all speeds, the slowest they run is at the vehicle
idle speed usually around 500 RPM or above, and then they are usually geared
up by the pully system to a much higher speed. Compressors run of a turbine
or windmill have no such lower speed limit and can run down very low speed.




The subject is "Wind turbine heat pump" and that has little or nothing to do
with domestic refrigetaion.

.

Again the subject is heat pumps. You are throwing out red herrings.


Think about this, say you build a heat pump running off a mill or turbine,
and you actually get it to work, what happens when there is little or no
wind and it is cold........


You need quite a strong wind to turn a compressor, if in doubt look up what
they recommend for generators of the size you are thinking of. It at least
gives you some idea of what you are looking at.

Here is something for you to look at. It is a 400 watt wind generator, it
has a blade diameter of 1.15m (About 4 feet) and it needs a 27 mile and hour
wind to get up to around 400 watts. At 15 MPH it puts out less than 100
watts...........

http://www.solarshop.com.au/wind%20turbines%20page.htm

Here we have a 1000 watts generator, it has over a 3 metre diameter blade
(almost 10 feet), and it produces its rated capacity at around 9 metes per
sec which is over 20 miles per hour.

http://chinapeople.en.alibaba.com/product/0/51232237/Wind_Turbine__1kW_.html

Now there are commercially available units, not home made.............

IE you need a lot of constant strong wind, and a big blade. A big blade
meens a big tower, which all equals money.

If you wish to build such a device, please go ahead, but I have told you
many limitations about such a venture, so go ahead at your own risk.

I would not, and I have experience in the field of heat pumps.

I have seen a multi compressor units 6 x 100 HP heat pump system that was
designed by experts, and there were major problems with it, it took years to
overcome the problems.

I have seen domestic units designed by large manufactures of air
conditioning equipment that did not work properly, so designing such a
system is not all that easy, and they did not have to contend with wind
speed, or lack of it.









Posted by Duane C. Johnson on February 25, 2007, 1:31 am
 Hi RamRodl;


 > For instance a 2 Hp motor uses around 1500 watts of power,

Ok, A unit of power.

 > that is over 4500 BTUs

But of course, this is not a unit of power.

Please be more careful.

Duane

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