Originally posted by Ampster
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heating hot water with pv panels
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Originally posted by nwdiver View Post
I'm not sure thinking winter lasts 12 months counts as an opinion
It still puzzles me why there is so much negativity about HPWH. It doesn't take rocket science to know that it is more efficient to move heat than generate it. That is relevant to the title of this thread which is, "heating hot water with pv panels". It does seem that the sidetracks to the original topic are often made in order to demonstrate superior knowledge about a subject that is NOT relevant to the original posters question.
9 kW solar, 42kWh LFP storage. EV owner since 2012Comment
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Originally posted by Ampster View Post
It still puzzles me why there is so much negativity about HPWH.
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Originally posted by PNPmacnab View PostI just find it interesting that every discussion about PV water heating turns into heat pumps.Comment
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Originally posted by PNPmacnab View PostI just find it interesting that every discussion about PV water heating turns into heat pumps.
Like heat pump discussions there are circumstances where MPPT controllers may not be the best fit.Last edited by Ampster; 08-09-2019, 04:57 PM.9 kW solar, 42kWh LFP storage. EV owner since 2012Comment
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Heat pumps get rebates so it is cost effective. Supplemental water heating with PV resistance heating has an equally impressive payback. It is not really a discussion. No need for the expense of storing that electrical power and extra hot water can be stored. I heat two residences, one with each. They have their individual advantages. I see no clear winner. In low use situations HPWH is a clear looooooser.Last edited by PNPmacnab; 08-09-2019, 03:55 PM.Comment
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Originally posted by PNPmacnab View PostHeat pumps get rebates so it is cost effective. Supplemental water heating with PV resistance heating has an equally impressive payback. It is not really a discussion. No need for the expense of storing that electrical power and extra hot water can be stored. I heat two residences, one with each. They have their individual advantages. I see no clear winner. In low use situations HPWH is a clear looooooser.Comment
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Originally posted by PNPmacnab View PostHeat pumps get rebates so it is cost effective.
Supplemental water heating with PV resistance heating has an equally impressive payback. It is not really a discussion.
No need for the expense of storing that electrical power and extra hot water can be stored.
I heat two residences, one with each. They have their individual advantages. I see no clear winner. In low use situations HPWH is a clear looooooser.9 kW solar, 42kWh LFP storage. EV owner since 2012Comment
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My heat pump at home saves me 47 cents a day. That is a hard way to make money. It is natural for you to think your situation is the same as others. At my vacation home I have two hot water tanks, a 6 gallon and a 10 gallon tank in series. I initially had a 10 and a 20 given to me. The 20 was near end of life when I got it and it started leaking three years later. I had been wanting to test the practicality of a 6 gallon point of use and went for an ECOsmart with a 1500W 120V element that would be a common solution for camps. The other tank is 2,000W 120V and both work at 60V DC. This isn't heating a teapot. It is certainly practical for a segment that visits here.
Without adding any extra panels to my system I have sufficient hot water for showers and the dishwasher. The control expense was about $40. It was shocking to me just how much energy isn't utilized in a typical PV system. It demonstrates how many of those just wanting a minimal camp system can have hot water on demand for not much more than the price of a tank. I typically feed less than 300W and sometimes just 20-50W. It all adds up and at least compensates for heat loss. I am about to add another 30 gallon tank for the clothes washer because the current system turns off so early in the day.
Supplemental heating is having 500-800W of panels feeding into the lower element of the tank. Tanks stratify and there are companies that have control systems just to prevent lower elements from coming on at night and low demand. Daytime only heating usually isn't a big problem. A low number of panels is ideal. It insures that 100% of available energy is utilized. Extra energy is banked as higher temp water that maintains temperature thru the night. It is low cost, uses existing tank and everyone has room for two panels. I've seen thermal siphon heaters added externally.
The technology works and is practical. It is worth talking about and maybe demand will make these system more common in the market. It is discouraging seeing how people heat water with PV. You could PV heat water with a dead chicken as a control system and that is about what people are doing. I just find that people are just so happy if anything works at all in solar.Comment
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Originally posted by PNPmacnab View PostMy heat pump at home saves me 47 cents a day. That is a hard way to make money. It is natural for you to think your situation is the same as others.
But even with your situation of $0.47/day that's a ~7 year pay back which is better than most installed PV systems.
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Originally posted by PNPmacnab View Post........ I had been wanting to test the practicality of a 6 gallon point of use and went for an ECOsmart with a 1500W 120V element that would be a common solution for camps. ......9 kW solar, 42kWh LFP storage. EV owner since 2012Comment
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This was an actual daily measurement for the months of November and December. That would be 1,100HWH a year and I don't live there for 5 months a year. Not everyone is a family of four. If I actually had a decent place to put 500W of panels, It would be lowered more than enough to pay for the panels in 5 years even with reduced occupancy.
Put a power meter on that ECOsmart and you will see that 700WH a day meets all your needs. That is low enough for a small solar array.Comment
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Originally posted by PNPmacnab View Post....
Put a power meter on that ECOsmart and you will see that 700WH a day meets all your needs. That is low enough for a small solar array.9 kW solar, 42kWh LFP storage. EV owner since 2012Comment
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