Navitron Renewable Energy and Sustainability Forum

HEAT PUMPS & Geothermal Energy => Heat Pumps => Topic started by: vee-tail on January 22, 2013, 01:11:44 PM



Title: Water wheel driven .. Water to air heat pump.
Post by: vee-tail 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.  :)


Title: Re: Water wheel driven .. Water to air heat pump.
Post by: guydewdney 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.


Title: Re: Water wheel driven .. Water to air heat pump.
Post by: knighty 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?


Title: Re: Water wheel driven .. Water to air heat pump.
Post by: vee-tail on January 22, 2013, 06:36:09 PM
knighty
The possibility of an overspeed on the 20 foot water wheel gives me nightmares  :o  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  :'( 


Title: Re: Water wheel driven .. Water to air heat pump.
Post by: vee-tail 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:


Title: Re: Water wheel driven .. Water to air heat pump.
Post by: smegal 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.


Title: Re: Water wheel driven .. Water to air heat pump.
Post by: Richard Owen 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.


Title: Re: Water wheel driven .. Water to air heat pump.
Post by: clivejo 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!

(http://images.powerhousemuseum.com/images/zoomify/TLF_mediums/9352.jpg)


Title: Re: Water wheel driven .. Water to air heat pump.
Post by: renewablejohn 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.


Title: Re: Water wheel driven .. Water to air heat pump.
Post by: vee-tail 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 


Title: Re: Water wheel driven .. Water to air heat pump.
Post by: guydewdney 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!


Title: Re: Water wheel driven .. Water to air heat pump.
Post by: renewablejohn 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.


Title: Re: Water wheel driven .. Water to air heat pump.
Post by: dhaslam 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. 


Title: Re: Water wheel driven .. Water to air heat pump.
Post by: vee-tail 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


Title: Re: Water wheel driven .. Water to air heat pump.
Post by: noah 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.


Title: Re: Water wheel driven .. Water to air heat pump.
Post by: derekmt on January 29, 2013, 03:50:06 PM
J...  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.
...
water is at its densiest at 4C ( in shallow water ) so as you chill it below 4C it rises to the surface...  You cant freeze the bottom of a lake or river only the top even if you are chilling the bottom.


Title: Re: Water wheel driven .. Water to air heat pump.
Post by: vee-tail on January 30, 2013, 09:39:39 PM
Quote
You cant freeze the bottom of a lake or river only the top even if you are chilling the bottom.
Posted on: January 29, 2013, 03:44:54 PMPosted by: noah 
Ah Ha so thats why the coils have to be as deep as possible, and a river better than a shallow mill leat.
But right now our river is in its's 'monster' mode, flowing very fast and turbulent, no way is a 200m brine mat going to survive in that. However a pair of 100m pipes laid in line with the flow and anchored into the bed rock might survive.  When the spates die down I can experiment and see how long they last.

Starting & stopping a heat pump compressor does appear to be a problem for a waterwheel drive; thanks noah.
I am thinking that it would be better to use the waterwheel & generator for DHW using an immersion heater and large storage cylinder.     


Title: Re: Water wheel driven .. Water to air heat pump.
Post by: renewablejohn on January 30, 2013, 10:07:07 PM
Good luck with anchoring pipes in the stream bed. Been there done that never did find all of the pipe. Hence the suggestion of doing heat exchange trash screen.


Title: Re: Water wheel driven .. Water to air heat pump.
Post by: guydewdney on January 30, 2013, 10:17:09 PM
in hindsight, I would go with the idea of the leccy generation and immersion heater system


Title: Re: Water wheel driven .. Water to air heat pump.
Post by: ecogeorge on January 30, 2013, 10:32:55 PM
Quote
You cant freeze the bottom of a lake or river only the top even if you are chilling the bottom.
Posted on: January 29, 2013, 03:44:54 PMPosted by: noah 


Starting & stopping a heat pump compressor does appear to be a problem for a waterwheel drive; thanks noah.
I am thinking that it would be better to use the waterwheel & generator for DHW using an immersion heater and large storage cylinder.     
The whole idea of using a heat pump is the efficiency of heat production,- put 3kw in get 9kw heat out!
Will you generate 3kw of electricity ?
Could you suspend some steel pipes along the river as a ground source , Navitron WR09 heatpump needs a flow of 21 litres minute (which is not much)  through the heat exchanger.
Use grid tie to start compressor (big surge) and run off water wheel electric.
At 3x the heat output with a cop of 3 which should be easy to achieve I'd be seriously considering a heatpump.
rgds George.



Title: Re: Water wheel driven .. Water to air heat pump.
Post by: RobNute on January 31, 2013, 10:16:33 AM
One thing I would say is that for simplicity and ease of control an immersion directly coupled to the generator takes some beating. That is what we have, the three phase ac from the genny goes straight to the immersion ( 3 phase ) and you can start the wheel in gear, load switched on and it comes up to a balanced speed perfectly. As the revs and volts go up together then so does the load, it just gradually speeds up until the two balance with the amount of water available.  Oversize the load slightly to be on the safe side and you will have a simple setup that will produce heat even with the smallest amount of water. We also made a great overspeed device that cuts the water if it goes over around 8 rpm, read about it here if you are interested,

http://www.navitron.org.uk/forum/index.php/topic,12399.0.html

as you mention, overspeeding wheels are frightening things!

Rob


Title: Re: Water wheel driven .. Water to air heat pump.
Post by: Ivan on February 01, 2013, 10:24:36 PM
refrigerant eventually lost through the gaps where the bearings are. True compressors are made for cars - and these would be a good starting point for a DIY mechanical-drive heatpump, but cars also need regassing on a fairly regular basis - something to bear in mind. You could base the system on propane - it works quite well as a refrigerant, but probably not as efficient as some of the gases (some of the CFCs were really good in terms of performance, but not so good environmentally.)


Title: Re: Water wheel driven .. Water to air heat pump.
Post by: Other-Power on February 05, 2013, 09:44:05 PM
Just grid tie it and buy a suitably sized electrical unit. A small unit can be found here http://shoebox.kensaengineering.com/ (http://shoebox.kensaengineering.com/).  I think it would be cheaper and easier.  You can defantly take the heat out of the stream.


Title: Re: Water wheel driven .. Water to air heat pump.
Post by: knighty on February 05, 2013, 11:19:49 PM
in hot places, where people have aircon installed which works as a heat pump in the winter... most systems are available with a built in inverter off the shelf... so you can control how hard/fast the unit works, and so control how much power it uses...

no idea how easy it would be to adjust it's power use depending on how much you're generating (or exporting) but it's worth looking at ?