Make standard heat pump more efficient with solar preheat?

I wonder if anyone has thoughts on improving the heating efficiency of a normal heat pump by warming the air around the outdoor unit? It seems like a "poor man's" version of the geothermal heat pumps to me.
Here's the idea. For a few $ build a passive solar water heater with antifreeze in the water. Let the water circulate through radiators positioned around the standard outdoor heat pump.
Of course you could more directly use the energy in your house but that requires modifying the inside, things the wife might not approve of. Heating the air around the heat pump could all be done outside with cheap surplus parts.
Possibly not worth the trouble but it might make a fun experiment.
gb
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I've often wondered similar things, but usually after some careful consideration, I've abandoned such ideas. The first thing that comes to mind about this is that you probably don't want to obstruct the airflow in or around the AC/heat pump unit, which is exactly what your radiators might do - unless they're far enough away to not block the airflow, in which case they'll be too far away to do any good.
Now, if you've got a real interest in solar heating, you could consider piping the heated water/glycol solution into the basement and using it to preheat your water prior to the water heater. Some internet searching might even yield up some plans for such systems, and depending where you live might you might find some government incentives for installing a solar system.
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For the life of me, I can't think of the name, but company out there that makes a heat exchanger pipe that goes on the sewer drain line that will preheat the water going to the water heater.
Here's a link to a site that mentions that HX. http://oikos.com/esb/49/gfx.html
AND here's the link! http://gfxtechnology.com /
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Why not add solar panels to offset the heat pump's power use?
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Probably the initial $$$ of the panels and other equipment necessary for it. At least this is what puts most people off when thinking about solar power. The solar hot water is much easier to build panels for I think, almost to the point of being within the realm of a DIY project for a really well-informed and ambitious person.
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When I was in college I made a solar water heater for the trailer I was living in. It consisted of a 4 x 8 box with insulated sides and clear plastic on the top. Inside was 500 feet of 1/2" black plastic hose. It was plumbed into the bottom of the water tank and worked with no power as a thermosiphon. Even on cloudy days we got 170 degree water out of it. Plenty for the three of us. However when it got a kink in it one day, I came home to a leaking box and a blob of melted plastic. Never underestimate the power of the sun!
LJ
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According to one article I read, simple solar panels like this capable of up to 400F, so, some care is needed in design to avoid blowouts or meltdowns. Ie: pressure relief valves.
I've seen a design which consists of a similar box. The innards consists of two 3/4" headers, one at either end, with 6 or so 3/8" lines running between the headers. The plumbing is all copper, is soldered to thin copper sheet, and the whole thing painted black and inserted in the box. Kept the costs down by silver soldering the copper instead of using fittings. Cover is preferentially glass. Various slight improvements, ie: a fiberglass or rockwool insulation batt under the copper, thermopane glass, etc.
Parts cost around $100-150 per unit (cheaper than 500' of 1/2" PVC ;-)].
There are also at least two different manufacturers of an inexpensive solar unit - mainly used for pools. 2x8 panels made from recycled auto tire rubber with the water lines molded into it. If I recall correctly, $100-150 or so each.
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Wouldn't it be easier to just build a mini greenhouse over the compressor that you could remove during the summer?
Or
just get some mirrors and use them to aim the sun at the compressor?
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