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Author Topic: Water wheel driven .. Water to air heat pump.  (Read 6316 times)
vee-tail
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« on: January 22, 2013, 01:11:44 PM »

Hello can anyone give me some advice on a water source heat pump for my water mill?
The river is presently only a few degrees above zero, and not much hotter in summer, but it is a large low temp heat source.
Is it possible to use the river as heat source for a water to air heat pump?  Air being the best low temp choice as I don't have under floor heating, and radiators need a much higher temperature.  The water wheel could drive the heat pump, if it had a low speed compressor. But it might be easier to use a conventional electrically driven heat pump.  Any comments very welcome.  Smiley
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guydewdney
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« Reply #1 on: January 22, 2013, 05:02:46 PM »

I investigated exactly this a while back - I was told in no uncertain terms that it wasnt possible, as the externally driven compressor wasnt possible due to leakage. Personally, I think they were talking bollix, as car / lorry / plane / train a/c systems work fine with external drives, and a heat pump is just an air con unit. You sound like a diy'er, go get an air con unit from a train or coach?

I bought an off the shelf unit made by navitron - a 9kw one iirc.

I dropped my pipes into the tail race to use the near infinite amount of heat there, rather than pipe the actual water through the system as my leat is quite silty at times, and I didnt want to muck about with filters.

In the end I wasnt happy about the noise levels and efficiency, it seemed to take more power than it made. Maybe I had a duff one, even one of the reps said that it sounded too noisy.
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knighty
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« Reply #2 on: January 22, 2013, 05:51:41 PM »

easiest way is to generate power from your water wheel, grid tie it, and then buy a mains powered ground source heat pump, and put the ground loop pipes in the water....

if you want to power it directly from the wheel, you could get a fridge unit from the front of a big truck - one of the engine driven ones - becauswe the compressors on those are belt driven and... bodge it to work... but I think it would be tricky to control the speed of the wheel?
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vee-tail
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« Reply #3 on: January 22, 2013, 06:36:09 PM »

knighty
The possibility of an overspeed on the 20 foot water wheel gives me nightmares  Shocked  So a direct drive to the compressor might not be a good idea.

Guy
A heat pump expert also told me that using the river as a heat source would not work.  Interesting that we seem to have come up with similar ideas.   I have e-mailed some of the heat pump manufacturers linked on John Cantor's website. If they confirm that river water in winter is too cold for a heat source then I guess we will have to abandon that one  Cry 
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vee-tail
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« Reply #4 on: January 28, 2013, 02:30:20 PM »

Just had a phone call from a very helpful guy at Kensa Heat Pumps.  Seems they do a brine filled mat secured to the river bed for the heat source.  He assured me that it would work OK for a water to water heat pump even if the river water temp was near zero.  I am not sure why the brine filled mat would not become a massive ice block in the river, but apparently that will not happen.
He did not recommend air as heating output, since although the rooms would be at a comfortable temp, the occupants would feel cold drafts. Lacking underfloor heating, it would be best to use double the usual number of radiators running at around 45 degrees.
However from Kensa's experience, wild Welsh rivers present big problems in securely anchoring the brine mat to the river bed.  For sure our river can go from a 10m wide 1/2m deep 'pussycat', to a roaring 2m deep with waves and boulders and fallen trees monster.  horror
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smegal
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« Reply #5 on: January 28, 2013, 02:46:55 PM »

Seems they do a brine filled mat secured to the river bed for the heat source.  He assured me that it would work OK for a water to water heat pump even if the river water temp was near zero.  I am not sure why the brine filled mat would not become a massive ice block in the river, but apparently that will not happen.


I guess that the frozen water would be carried away by the current.
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Richard Owen
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« Reply #6 on: January 28, 2013, 02:53:09 PM »

I ran my ground loop pipes in my stream for a couple of years and they were fine.

I took them out eventually because I had to put them in coiled and they kept silting up.

Although I have no empirical evidence, I think they worked better than the loops I now have in the ground.

I certainly wouldn't bother with one of those mats if you could get away with 100m of 25mm mdpe in your tail race.
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clivejo
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« Reply #7 on: January 28, 2013, 04:44:30 PM »

I am not sure why the brine filled mat would not become a massive ice block in the river, but apparently that will not happen.

From wikipedia "Brine is a common fluid used in large refrigeration installations for the transport of thermal energy from place to place. It is used because the addition of salt to water lowers the freezing temperature of the solution and the heat transport efficiency can be greatly enhanced for the comparatively low cost of the material."  

Also being at the bottom of the river with running water over it will help keep it from freezing.  

I would be with Richard on this one.  Why go to the expense of a mat when a length of piping will do the job.  Circulate salty water through it to improve the thermal transport.

I really cant see why you couldnt couple up a compressor directly to the water wheel!  I remember years ago seeing a really old fridge system which was driven via a belt by a Lister CS engine from the flywheels!

« Last Edit: January 28, 2013, 04:46:07 PM by clivejo » Logged



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renewablejohn
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« Reply #8 on: January 28, 2013, 07:48:43 PM »

If it was me I would incorporate the trash screen as the coils for your heat pump. With flowing water you can forget about freezing.
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vee-tail
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« Reply #9 on: January 28, 2013, 09:39:30 PM »

Some really useful responses ... thanks everyone.

However I now see the weak point in my setup ... All the inner shafts & pulleys run on Cooper bearings, with no probs.
But the 5 rpm waterwheel drives a huge 10 foot dia spur gear, which meshes with a 12 inch cog, bringing the rpm up to 50. Although the cast iron teeth are odd on the gear / even on the cog to reduce wear & chatter ... but there is no proper lubrication. I just regularly slosh heavy grease over the teeth, which is fine for relatively short running, but not so good for continuous use. As in driving a big heat pump compressor for example.
It might be possible to fabricate an oil bath over the bottom section of the gear where the cog is located.  Ah well back to the drawing board ... facepalm 
« Last Edit: January 28, 2013, 10:00:48 PM by vee-tail » Logged
guydewdney
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« Reply #10 on: January 28, 2013, 10:36:26 PM »

I use a Lincoln lubrication pump, which is a self contained grease / heavy oil dispenser, with a timer, pump, reservoir and manifold all built in.

This lubricates my inner bronze? Bearing. My chain drive, ten to one, is splash lubricated.

Lincoln pump was fifty quid on ebay, look for crane, hiab, lorry, etc automatic lubrication. Like this:-

http://www.ebay.co.uk/itm/Interlube-GX3103-Oil-Pump-for-use-on-a-centralised-lubrication-system-/160965169582?pt=LH_DefaultDomain_3&hash=item257a4591ae

But a bit cheaper!
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renewablejohn
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« Reply #11 on: January 28, 2013, 10:42:23 PM »

Some really useful responses ... thanks everyone.

However I now see the weak point in my setup ... All the inner shafts & pulleys run on Cooper bearings, with no probs.
But the 5 rpm waterwheel drives a huge 10 foot dia spur gear, which meshes with a 12 inch cog, bringing the rpm up to 50. Although the cast iron teeth are odd on the gear / even on the cog to reduce wear & chatter ... but there is no proper lubrication. I just regularly slosh heavy grease over the teeth, which is fine for relatively short running, but not so good for continuous use. As in driving a big heat pump compressor for example.
It might be possible to fabricate an oil bath over the bottom section of the gear where the cog is located.  Ah well back to the drawing board ... facepalm 


Cant really see a problem. Just disconnect the 12 inch cog and replace with a hydraulic pump with suitable cog then connect to suitable hydraulic drive motor on heat pump. Might be worth also looking at a hydraulic drive generator as an alternative. If you cannot replace the cog you could always attach a chain and sprocket system.
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dhaslam
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« Reply #12 on: January 29, 2013, 01:45:34 AM »

The truck air conditioning  unit sounds like a good  option as an experiment.  Normally they would have air in and air out  but instead there would need to be two heat exchangers for a water to water system.  Apart from getting the  proper rotation speed  for the compressor  there is   the problem  of connecting up the  two heat exchangers with refrigeration fluid, including an expansion valve  on the hot to cold connection.    You may need to use a magnetic clutch on the drive  that cuts out on over temperature or pressure  in the refrigeration  circuit. 

It is a fairly  difficult  exercise  but it should be  quite  efficient. 
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vee-tail
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« Reply #13 on: January 29, 2013, 11:34:49 AM »

Fascinating stuff ... I wish this site was up and running 20 odd years ago when I started tinkering with hydro ... would almost certainly have done things differently  ballspin
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noah
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« Reply #14 on: January 29, 2013, 03:44:54 PM »

Running a compressor (especially at low speed) off a waterwheel is problematic. This is because of the stop/start nature of the load, especially on single pot compressors.
I ran a two cylinder fridge compressor off my wheel for years but  it had to run at around 500 rpm minimum because of (a) the inherent lumpiness of the load and (b) if run at too low a speed most compressors will seize due to lack of oil splash lubrication.
Even at 500 rpm I needed a pretty hefty flywheel (about 1/2 ton) to smooth out the bumps.
A multi-cylinder compressor would be better or maybe a non piston type such as hydrovane.
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