Has anyone used solar to increase the water temp coming from the ground loop (or open loop) prior to the water going into the geo unit? This would greatly increase the efficiency even if the incoming water temp raises a couple degrees. This could greatly reduce, maybe eliminate the elect. back up strips from coming on during cold outdoor temps.  You would want a bypass in the non heating seasons.
Or have your water heater connected to the solar, then have a heat exchanger w/ a bypass that the geo loop water goes through prior to entering the geo unit?

I just read in another thread (solar area) someone else asking similar question...

In principle I like the idea, but don't see it as a great idea from a contractor/marketing stand point. ROI would be lengthy in most cases. Might be better utilized making warm air or DHW. A hydronic fan coil with solar heated water could heat the home without the compressor running for instance.

But, could you do it and would it work, sure. Make sure to employ storage tank and tempering (so you don't exceed EWT limit).

Joe

Just to add a little to what Joe said.
The trick is getting enough solar capacity. Since solar is producing the most when you need heat the least, it's not a great match.
At night time, when the system is running hard, the solar panels may actually cool the water because the solar panels will be radiating heat to the night sky - sucking heat out of the water.
An additional problem is that a typical 4x8 solar panel collects 20,000-25,000 BTUs per day under good conditions. A house might need 500,000 BTUs for heating for a day.

There are ways to improve these situations. As Joe said, a storage tank, would make a huge difference. You would heat the water and store it during the day, then use the stored heat as needed for the heat pump. This would also eliminate the nighttime cooling issue because you would run the solar system as normal, with the circulators running during the day.

I believe there is a guy on another website who has reported that he (somehow) connected his solar to his geo and was taking advantage of the warmer water temps produced by the solar. It's the website that tends to be for contractors only.

Is the solar collector was evacuated it would work better since it would lose hardly anything at night. Basically just having a control on the solar panel that would turn on the field circulating pump once the panel got warm and just circulate the field through the collector. Then during the day it would slowly warm up the field if the geo unit was off and could absorb as much as the solar collector could throw at it. If the geo system turned on it would continue to run as normal. The big catch would be to make sure the panel could handle the flow needed from the geo system. You could do a similar setup using a heat exchanger on the field lines and the solar collector.

You could use your current loop (and thus the ground) as storage - one loop and pump for solar to ground loop and another loop/pump for the geothermal to ground loop (ground loop is part of both parallel circuits). Agreed, I'd look at the numbers before actually building such a thing.

Thanks for the replies! I like the idea of the insulated storage tank to hold the water (or antifreeze) that is heated from solar during the day. This could preheat the water heater basically year round (with heat exchanger) and give the geo a boost during the heating season.

Jere,
There is a guy in my neighborhood (SW lower MI) that is doing that. I NEED to get over to his house and see how it working out for him. He has several hot water solar panels on his rooftop (probably 6 or more 4x8 panels) which are connected up to (2) 1500 gal underground storage tanks. I think he then pumps out of one of the tanks to his GHP and returns to the other. If I remember right he hopes to elevate his water temp in the summer as high as he can get it, then use the stored hot water in the winter for his GHP. P.S. The tanks are underground well below the frost line and are heavily insulated with closed cell foam (all around them). Thanks for bringing up the question and jogging my memory. I'll go see him soon.

Sounds like that system isn't ground coupled; assumes all needed heat will be available from solar panels, unless you've left out a description of the ground loop and how it interacts with the storage tanks.

Let us know.

Jere,
Got over to his house today and got a fiew more details (Wow what a setup!!!). He has (3) 4500 gallon stainless steel tanks underground hooked in series. Each of the tanks are insulated to R26. These tanks aren't yet hooked up to the solar panels yet (he's still trying to decide on the best solar panels) but he estimates he will need 12 of them on the roof. He showed me a complex spread sheet containing all the data. His calculations (based on avg temps and no. of sunny days per year from NASA's website) suggested the solar collectors could heat the water to 160F (maybe 180F) during the summer months here in SW Lower MI. The water temps would then slowly drop over the fall and winter months but still well above freezing (thus providing higher performance to his GHP). If all goes well he should be up and running later this year and with some real time data to show how the system is working. I told him about the WEL (Web Energy Logger) system. It would be nice to see the data on his system over time.

I wonder what the plan is for AC.

Engineer,
He has AC just like everyone else who has GHP. His system is a very complex array of pipes, valves, pumps, tanks, etc. During the summer months when the solar panels are heating the underground tank water the closed loop from the tanks to the geo are presumably closed. The GHP then switches over to either a conventional pump and dump off the well or (if I understand this correctly???) a different closed loop system which includes a buffer tank (80 gal) and a heat sink/dump under his garage slab. Hopefully this is somewhat clearer.

rjdalga,
must be a ground loop as well, 1500 gal isn't going to last long.

Jonr,
you crack me up......" Agreed, I'd look at the numbers before actually building such a thing."..... (just not before suggesting it)

j

No idea what your point is. Perhaps you are confusing "could" with a recommendation. Or you think the sentences should have been in a different order (like that makes any difference).

I have a similar set up in Virginia. Four 4x10 flat panels (drainback) heating a 500 gallon tank. In winter, GTHP pulls preheated water out of the 500gallontank until tank temp drops to about 45F, then switches to a standing column well (SCW) system for BTU's. Cooling the 500gallon tank down at night also helps with the solar panel efficiency (greater deltaT) during the day. Heat distribution is via RFH. For AC, we rely solely on the SCW and chilled water with blower units. For heat during swing season, GTHP only uses solar tank, Winter both solar and SCW. In Summer, panels provide 100% of DHW. So far this has been up and running since the Summer of 2009 and doing well. Too hard for me to determine efficiency compared to previous system as a lot of other changes were concomitantly made to the house.

With the solar rebates in Virginia, I hope to add some more panels for essentially no significant additional cost.

"must be a ground loop as well, 1500 gal isn't going to last long."
How does 3x4500 equal 1500? I hope you have someone else do the math on your bids.

Manners, Arkieoscar.

About 7 posts back there's mention of paired / opposed 1500 gallon tanks.

Folks here do a pretty good job of keeping a civil tongue and I ask you to hew to that standard. Gratuitous public insult to a veteran member, or anyone for that matter, is inappropriate and rude.

If you feel absolutely compelled in future to communicate such a comment kindly avail yourself of private messaging.

As long as this works both ways, and is not a double standard, I agree for here and elsewhere.

" He has several hot water solar panels on his rooftop (probably 6 or more 4x8 panels) which are connected up to (2) 1500 gal underground storage tanks. I think he then pumps out of one of the tanks to his GHP and returns to the other."
Correct my math if I'm mistaken, but if I pump out of one tank and discharge into a second, then I think I'm only using 1500 gallons for space conditioning.
j