Subject is drifting off OP subject but nicely into something interesting to me.

Don't forget the pump power penalty with a pump and dump system (especially if you have to lift it 300+ feet!).  Also, a mistake I made in the past is forgetting that for closed loop systems you only factor friction loses, no lifting or head loses should be included (e.g.  elevation between pond and heat exchanger is not a factor).

I have a Climatemaster T27 pump and dump system in West Michigan.  Well is 5", 95' deep, with the water level at around 65'.  I have a single constant pressure variable speed well  pump to do the geo, UG sprinkling, and domestic water. 

My pump draws about 800 watts to pump 4.5 gpm through the heat exchanger and out to the drainfield, and 1.2kW  for 6gpm (1st stage and 2nd stage).  I'm loosing a good chunk of energy every hour it runs to pump around 300 gallons out of the ground, pressurize it to 65 psi, only to bleed it out through my discharge control valve.   

Based on other postings here it seems like a closed loop pump might take less than 100 watts to run, this would save me 700 watts per hour run time, but this would be reduced somewhat by the impact of more adverse enterign water conditions.  

As was also mentioned on this site somewhere,  well water quality can change over time, so you have to ensure the savings are worth the current/future risks and maintenance costs associated with open loop.  

Having said all that, I'm VERY happy with my open loop performance thus far.  I'm just coming through the 3rd winter.  Open loop has given me some advantages:

- Didn't have to factor increased loop costs, when comparing different sizes. So I sized my unit for full heating load (with some spare for future expansion), so no backup strip heat is installed. 
- I can do very aggressive set backs with no impact to efficiency, no strip heat, and no diminishing output
- I get excellent (warm) EWT all winter long. 
- most importantly for me:  reduced upfront cost, which was the only way I was going to get any geo system through the other half of the appropriations committee


If your willing to take the risk and have enough info about the ground water in the area from closeby long-term users, you would want to look hard at dual pump system.  Use a low pressure primary pump (hp supply taps from here) AND a secondary boost pump for the irrigation and domestic (high pressure needs).     The deeper your well the quicker the payback on this type of dual pump setup.    Adding tanks to reduce cycling doesn't save any pump energy cost  as long as you still are pumping it all to a high pressure level then bleeding out to a drain.