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sundug

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Reply with quote  #1 
With the proper panels, collectors, and system type, a solar hot water heater will benefit the planet and your wallet.

The solar thermal systems that I promote provide a return on investment between 5 and 15 percent, depending on the type of fuel you’re replacing, your location, and which state utility incentives are available. A residential solar water heater will offset greenhouse gas emissions by three-quarters of a ton of carbon dioxide every year — the equivalent of an average driver cutting 1,300 miles from their annual commute. Moreover, solar water heaters qualify for the 30 percent federal tax credit until 2020, so the time to install is now!

If your plumbing and wiring skills are up to snuff — and code — you’ll have no trouble assembling a solar water heater for your home. For everyone else, a commercially available system is the best recourse. This article will present four initial steps to take and the general options to consider when shopping for solar thermal systems.

 


http://www.motherearthnews.com/renewable-energy/solar-power/solar-hot-water-heating-systems-for-home-zm0z16aszbre.aspx?newsletter=1&spot=headline&utm_source=WhatCountsEmail&utm_medium=email&utm_campaign=MEN%20GEGH%20eNews%208-12-16&utm_term=MEN_GEGH_eNews&_wcsid=800AB0AA6664C53343359F90C7740FB20C480FA9988D2421

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stmbtwle

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I live in Florida and I have a solar thermal water heater. While it IS "green", I'm not impressed with it as an investment. I've already had to replace a tube absorber, which wiped out any savings. I think the new PV/heat pump systems would be a better investment.

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sundug

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Quote:
Originally Posted by stmbtwle
I live in Florida and I have a solar thermal water heater. While it IS "green", I'm not impressed with it as an investment. I've already had to replace a tube absorber, which wiped out any savings. I think the new PV/heat pump systems would be a better investment.


There are several different types of solar water heaters, my PV pumped closed loop flat plate SWH has performed well for 26 years with only an expansion tank failure. It has paid for itself many times over. The collector is over 35 years old.
http://www.builditsolar.com/Projects/WaterHeating/DougsSolarWater.htm#Dougs

The heat pump water heaters have been having their problems, GE is a popular brand- https://www.consumeraffairs.com/homeowners/ge_water_heater.html
1.4 stars on Amazon-
https://www.amazon.com/GE-GeoSpring-Hybrid-Heater-GEH50DNSRSA/product-reviews/B006UA7930

Rheem gets 2.8 stars- https://www.amazon.com/Rheem-HP50RH-Water-Heater-Gallon/product-reviews/B003UHURTY

As a retired HVAC guy, I'll take the simplicity, efficiency and lower cost of a stand alone SWH over a heat pump anytime. Sundug
http://www.builditsolarblog.com/2012/03/dougs-solar-projects.html

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SolarBuff

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Reply with quote  #4 
A few unbiased reviews for home solar water heaters: http://www.toptenreviews.com/home/hvac/best-solar-water-heaters/

Solar Buffalo
http://www.solarbuffalowny.com/
stmbtwle

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My issue with ANY stand-alone system is that once you reach limit temperature or full charge, the system shuts off, and any more incoming energy is rejected. A thermal collector will overheat, PV will just sit there and cook. Either indicates wasted energy. A PV/heat pump setup is grid tied, so once the water is at limit the energy from the PV automatically goes to other uses.

Even my normally off-grid houseboat is grid tied. The batteries have priority, but once they are fully charged the power goes to other loads. I realize this COULD be done with thermal, but it wouldn't be as easy.


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sundug

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Quote:
Originally Posted by stmbtwle
My issue with ANY stand-alone system is that once you reach limit temperature or full charge, the system shuts off, and any more incoming energy is rejected. A thermal collector will overheat, PV will just sit there and cook. Either indicates wasted energy. A PV/heat pump setup is grid tied, so once the water is at limit the energy from the PV automatically goes to other uses. Even my normally off-grid houseboat is grid tied. The batteries have priority, but once they are fully charged the power goes to other loads. I realize this COULD be done with thermal, but it wouldn't be as easy.


 Drainback systems will shut off and drain the collector, not overheat. My PV pumped closed loop antifreeze system has no high temp shutoff, and I have not had an overheating problem in the 26 years it's been in service here in southern central TN. Highest temp I've seen is 155*F coming into my 40 gallon electric tank, which is 34 years old, BTW. The inhibited Propylene Glycol I use doesn't start to break down until 250*F. Properly sizing collector to storage and both to usage prevents overheating. PV panels can sit in the sun while disconnected without harm. I don't see this as wasted energy, as it's free energy and when storage is full, you have all you need immediately on hand. The heat pumps have slow recovery and can be unable to keep up with high demand. They also cool the air around them, fine in FL, not so great in northern climes. Sundug

Here's some more info I found on them-

Heat-pump water heaters:

Need a lot of space — roughly 1,000 cubic feet of air space around the unit. They also need to be located in a spot in your home that consistently remains between 40 degrees and 90 degrees so they can draw on warm surrounding air. And because the heat pump is on top, a hybrid water heater needs as much as 7-feet clearance from floor to ceiling.
Have an average lifespan of eight to 15 years.
Cost: $1,100 to $3,000. Installation costs add $1,400 to $2,000. They require condensate drains.

While standard electric water heaters have no moving parts, heat-pump water heaters have compressors (to compress the refrigerant vapor causing it to condense into liquid) and fans (to circulate room air across the heat exchanger so that heat can be extracted from it).   

Noisier than other water heaters

Be aware that these mechanical components produce noise—often significantly louder than a refrigerator. Heat-pump water heaters I’ve examined have noise ratings from 55 to 65 decibels (dB), which is a large range of variability (65 dB is ten times as loud as 55 dB). Most refrigerators are 40-50 dB.

If you are particularly sensitive to noise and don’t have an acoustically isolated place to install it, the energy savings from a heat-pump water heater might not be worth it.


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stmbtwle

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Reply with quote  #7 
Admittedly a heat pump has moving parts and will make some noise. But not many are installed in the bedroom, more likely in the laundry room or garage.

Heat pumps today are sealed units and last a long time, air conditioners and refrigerators 10, 20 years or more. I really don't think that would be an issue.

A stagnated collector can easily reach boiling, and scale can be a problem. I'm already getting scale in the plumbing to my 8 year old unit. How long before it becomes a problem I don't know. This may be common to ALL water heaters.

As PV panels keep getting cheaper, the less efficient heating element MAY turn out to be more cost effective than either a thermal collector or the heat pump, and it's certainly simpler. Also with PV, leaks and freezing are not a concern, and the energy produced is not dedicated to a single purpose.

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SunFun

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Reply with quote  #8 
We have a heat pump installed in the basement. Does it make a noise? I suppose it must make some noise but, even when I have been down there next to it for extended periods, it is not something I have ever really noticed.

I imagine the scale problem will vary by location, depending on how hard your water is. I have not checked it on my solar panel plumbing; perhaps I should. I doubt it is a serious issue even if present, though. My plumbing is all 22mm so it would take a lot of scale build up to prevent flow. With small bore pipework it might be more of an issue.

I have had my panels stagnate a couple of times during power cuts when the pump stopped working. It is not good and if possible you should arrange the pipework so thermosyphon will ensure some flow even without power. I did/could not do that, which I regret.
stmbtwle

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Reply with quote  #9 
Even a drainback collector will get hot without any water flow, and when your storage reaches the set point the pump WILL shut off. Otherwise you'll overheat the tank and may set off the relief valve. Without the water flow to cool it the collector will just get hotter and hotter, there's simply no place for the heat to go. Then the pump comes on and pumps cooler water into it. I know thermal collectors are tough, but one wonders how much of this cycling they can take before a connection or something else fails.
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