diy solar

diy solar

PV direct heat pump water heater?

Smeeg

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Joined
Oct 23, 2022
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Was looking at the Rheem heat pump water heaters & the EG4 Hybrid AC/DC Solar Mini Split. & that got me thinking does anyone make a heat pump DC/PV direct water heater? Ie no batteries or inverter just plug solar panels in?
 
This gets discussed a bit.

The bottom line seems to be that solar water heaters (no photovoltaic panels) are way more efficient and globally “ better” at heating water.

Is there generally considered a “best” company for off grid use?
 
For the solar water tube heat things? I don’t know but would be interested. Someone mentioned that “take off” tend to become available cheap(er). New, they are not cheap.

I’ve got a half baked idea to make my own with copper pipe or pex. If the coils are below the insulated storage container, they self circulate. Lots of diy vids on this type thing.
 
For the solar water tube heat things? I don’t know but would be interested. Someone mentioned that “take off” tend to become available cheap(er). New, they are not cheap.

I’ve got a half baked idea to make my own with copper pipe or pex. If the coils are below the insulated storage container, they self circulate. Lots of diy vids on this type thing.

Yes I was wondering about commercial products as nearly everything I see is DIY
 
Deye(EG4) makes a couple of units which literally appear to use the same condenser unit to pump refrigerant.


 
Deye(EG4) makes a couple of units which literally appear to use the same condenser unit to pump refrigerant.



Wow very interesting can we not get this in the USA yet?
 
This gets discussed a bit.

The bottom line seems to be that solar water heaters (no photovoltaic panels) are way more efficient and globally “ better” at heating water.
Agreed solar thermal is way more efficient.

But retrofitting a hot water heater for a hybrid hot water heater is pretty much plug and play, running a pipping and pumps controller and additional storage (maybe a back up as well?) for a solar thermal system is pretty complex plus there is maintenance involved.
 
For the solar water tube heat things? I don’t know but would be interested. Someone mentioned that “take off” tend to become available cheap(er). New, they are not cheap.

I’ve got a half baked idea to make my own with copper pipe or pex. If the coils are below the insulated storage container, they self circulate. Lots of diy vids on this type thing.
Back in The Day, when I was a kid and dirt was new, my dad built a solar water heater in the back yard. He took the tank out of an old water heater, plugged the excess holes, painted it flat black and built a plywood box to face it south at 45deg. Some of the mylar insulating foam inside and a plexiglass top and that water would get pretty hot pretty quick.
 
In the Mexico bush I thought similar type systems were also common, black poly tanks on the roofs, gravity feed and boom you’re done.

Alas for most of us you have to deal with freezing temps more than 100f days, so it’s either a drain back system of a glycol system. Then you have to worry about stagnation (systems at max temp) and how it deals with excessive heat.
 
My house has a big solar hot water heater system, and I originally thought it would be better to rip it off and just go for a hybrid HW Heater during a re-roof project. Boy was I wrong. I have (3) 4x10' flat collector panels and 240 gallons of storage and use about 10kWh/year on water heating with the resistance elements. Quite happy with it... but I don't have to deal with freezing temperatures.

If you live in a cold climate, the evacuated tube systems are much more effecive for year-round use. Even if it can just pre-heat your water on the worst days it is still going be cheaper than a hybrid system. You want plenty of storage though.
 
This gets discussed a bit.

The bottom line seems to be that solar water heaters (no photovoltaic panels) are way more efficient and globally “ better” at heating water.
except at night, depending on how much thermal storage you have. I could see adding ESS powered heat pumps for assisting at night
 
I don't need one of the heat pump hot water heaters but I have thought about getting one anyways since it would cool the workshop while it was heating the water :)

Also since I have a 30 gallon hot water heater in the kitchen I might put one in there to cool the kitchen some too.....
 
The bottom line seems to be that solar water heaters (no photovoltaic panels) are way more efficient and globally “ better” at heating water.
I agree and have installed two thermal hot water system in the past 45 years. The last one was in 2005 and since then the price off PV solar panels has dropped significantly. Despite the great efficiency of solar water heaters, I have found that a GT PV system with an AC coupled heat pump water heater is optimal for me. It all depends on where you are standing.
 
I'm always standing with my wallet tightly clinched in my fist. lol
Best bang for your buck might be a direct from the panels dc electric pre heater.
You don't get the improved COP from a heat pump, but you don't need to buy an expensive heat pump either.
It will probably require about three times as many solar panels for the same heat, but its still going to cost way less.

It really depends what you are trying to do.
 
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