PV opportunity hot water heating

[SolarMusher]

Mr. Felix
I was looking at your email about adding a Geyser-RO to your system. There are a few problems. First, an old, gas heated, water tank is nothing but a huge radiant heat loss. If you were to look inside a direct fire tank, it's nothing but a steel tank that has a huge hole in the middle that is uninsulated. The heat pump would have to run all the time to try to keep up with the inevitable heat lose that that would be incurring. As the tank temperature came up, the rising heat would act like a chimney and would pull heat out of the tank. The inefficiency of that system would be atrocious. I try to get customers with old inefficient water tanks to get rid of them and spring for something new with lots of insulation. It's hard to convince people that it's more cost effective to more spend money upfront and get a good quality, well insulated high efficiency water heater or tank. Over the life of the tank, the long term costs of an inefficient tank get rather high. It makes the payback of the Geyser Heat Pump a lot longer and sometimes not at all. Even if you get your electricity for free from solar panels, the Geyser Heat Pump would run for the designated time and heat the tank as best it could but that heat would quickly be radiated away. The Geyser Heat Pump will heat water at a rate of 12.5 gallons per hour @ 120 degrees tank temperature and at 60 degree water supply. It would take over 3 hours to heat that 40 gallon tank but the tank sits for 21 hours cooling off.
Your system sounds like it would supply the necessary amount of power but the switching would the problem. The power plug would have to be plugged into an outlet that was switched on and off by a relay. The Aux mode can be either a dry relay or a 12 volt signal. 120 volt line power could be run though the dry relay to power the heat pump or the 12 volt signal could be used to turn the Solid State relay to power the heat pump. That would be up to you. The Geyser starts with 12-13 amps so the inverter would have to handle that large surge for about a second. If the voltage drops too much during compressor start-up, the relays in the Geyser could chatter and stick because the voltage necessary to hold the relays would be insufficient. Allotting 600-800 watts is going to be a little on the light side. It would be best to have 1000/1200 watts available be cause of the amp pull during start-up. The Geyser will "run" just fine on the inverter, it's the start-up that can cause problems.
The Geyser heat pump needs to be located in an area that is over 50 degrees F. Under that temp, they have to run a lot to make hot water and it kills the efficiency.
The price for a Geyser-RO is $899 plus $160 for the shipping. If you want to become dealer, you can get them at dealer pricing.
We don't have a lot of experience integrating the Geyser into a PV array so there is only one way to see if the Geyser-RO wil work and that is to get one, install it and see how it works. It looks, in theory, that it should work fine.
Alan Simberg

Here is the reply fom Nyle to my questions about the Geyser in a renewable energy system.
Erik

[mtdoc]

Erik,

I'm sure your Magnum inverter will handle it just fine.  Interesting about the heat loss from an old gas fired water heater - it makes sense.  Perhaps find a non functioning electric water heater to use as a cheap storage tank.  Of course you can build one for cheap if you have the time see HERE

I looked back and found what I paid for my Geyser RO.  It was $799 plus $92 shipping.  It was on "sale"at the time.

Not cheap but a worthwhile investment IMO. It's nice to be able to heat my water efficiently with 120 VAC from PV - at least for part of the year....

[SolarMusher]

Hi mt,
After watching carefully my old gas tank, I've to say he's right. Did a quick search on used electric tank here, but nada!
I've finally found a brand new Giant 40gal for 339$. Another idea would be to use my old gas tank and to insulate burner and chimney with mineral/glass wool (total cost 0$) but the problem is that I pump from the lake and I'm afraid of dirt in tank that could flow through the Geyser 
Even with a new tank, it makes sense. For sure, it will reduce my propane bill by 40/50%, not so bad!
Do you think I really need a heat sink to run this DC/AC SSR on 120Vac/6-8amps for 3-4hrs?
Thanks for the link, mt. Very interesting!
Erik

[jim k.]

If your thinking of spending that much money just to heat water go buy a good quality tankless heater, I have a Rheem tankless water heater and a propane kitchen range, just filled my tank yesterday and used 164 gallons for 17 months, also sounds like you need a $60 whole house water filter on your water supply , I have about $700 in my water heater.

[dgd]

Do you think I really need a heat sink to run this DC/AC SSR on 120Vac/6-8amps for 3-4hrs?

I was quite surprised to find how hot these AC SSRs can get. Although I'm switching 230vac at about 6 amps for 3 to 5 hours each day and the ambient temp here is quite high 19 to 24 degC.  Definitely use a heatsink.

dgd

[SolarMusher]

I was quite surprised to find how hot these AC SSRs can get. Although I'm switching 230vac at about 6 amps for 3 to 5 hours each day and the ambient temp here is quite high 19 to 24 degC.  Definitely use a heatsink.

Thanks for the info dgd , I have never used SSR before, always used 12V relay to power little loads from 48V. I will follow your tip and use a heatsink. I was also looking for a solution to switch off Ac lights x10 in lodge when people are fishing on sunny day  , I think I have found it... 

If your thinking of spending that much money just to heat water go buy a good quality tankless heater, I have a Rheem tankless water heater and a propane kitchen range, just filled my tank yesterday and used 164 gallons for 17 months, also sounds like you need a $60 whole house water filter on your water supply , I have about $700 in my water heater.

Hi Jim,
Why do you want me to buy/add another gas heater that don't meet my needs (8/10 pers) and spend more money on propane when I've right now enough PV energy which would be lost to run/preheat an efficient electric heater  The way I'm looking, could save me a lot on propane on a large part of the year. Of course, it could be built cheaper but IMO, a large residential off grid system needs to be oversized to meet the needs on an annual basis and then generates excess that would be wasted if not used.
A tankless heater would be interesting on a smaller system but the goal here is to use a max watts generated from PV 
Just my opinon,
Erik

[Westbranch]

I was also looking for a solution to switch off Ac lights x10 in lodge when people are fishing on sunny day  , I think I have found it... 
Erik

there have been several threads that beat on that topic heavily, and it seems to keep coming back...tell us more?

[jim k.]

I do everything on a cost to benefit  ratio , I have a 1635 sq ft home,  a 1650 watt pv system which is going to increase by 1000  watts and propane where it is more efficient than electrical and wood heat, if I put heating coils in the wood stove then I could really get with the program which is something I 'm considering.  Yes it cost to fill the tank every two yrs ($345.00) but it also cost to maintain my solar system, like the inverter I smoked last week experminting, these are a couple of the reasons for my thoughts, I'm not always going for the cheapest but what makes my life simpler and interesting.   

[SolarMusher]

I was also looking for a solution to switch off Ac lights x10 in lodge when people are fishing on sunny day  , I think I have found it...

Erik
there have been several threads that beat on that topic heavily, and is teems to keep coming back...tell us more?

Hi West,
I was just thinking doing this using Aux2 Nite Light with SSR supplying a dedicated subpanel, but all other ideas are welcome.
Erik

[Westbranch]

what about motion sensors on your most troubling lights?  ie bathroom, bedroom?  bathroom fan/light timers?

[dgd]

I do everything on a cost to benefit  ratio , I have a 1635 sq ft home,  a 1650 watt pv system which is going to increase by 1000  watts and propane where it is more efficient than electrical and wood heat, if I put heating coils in the wood stove then I could really get with the program which is something I 'm considering.  Yes it cost to fill the tank every two yrs ($345.00) but it also cost to maintain my solar system, like the inverter I smoked last week experminting, these are a couple of the reasons for my thoughts, I'm not always going for the cheapest but what makes my life simpler and interesting.

Cost to benefit ratio was the rationale, for many years, behind my energy make or buy decisions. This held me back from getting into the RE business by 5 to 10 years. In 1990 the payback or cost recovery time for a PV based modest system was way longer than the life of the system. In any case the folklore then was that it cost more energy to manufacture a PV  panel than the panel could produce in its lifetime. So cost too high, benefit to me and environment too low.
I stopped using that rationale about 1995 and planned to become energy self sufficient AFAP. Never looked back, off grid 2000. Neighbours think Im eccentric or maybe just crazy.
Cost of LPG refills $180 a year, cooktop and hot water only - installed  LPG instant hot water system, removed electric cyclinder when I went off grid.
Now with the Classic and PVs costing under 10% of 1995 prices I decided to remove LPG system install hot water cyclinder with AC element and let the Classic work it.
Now the doing something interesting, feeling good, making free energy, self satisfying smugness, and non reliance on a  greedy price gouging profit focussed corporate that the fools in govt (in New Zealand) sold the public owned power generating industry too, is way better than even sparing a nanosec considering costs to benefits.

dgd

[jim k.]

I get what you are saying, but I've got the same kind of neighbors, they think I' crazy and my pv system is a waste, but when the storms hit this winter and the grid went down my life didn't change, this is the first winter with no gen set running.

[Westbranch]

DGD, is your avatar supposed to be a Kia? its so small I cant make it out...
Q 2  did you mean too = also or to = to in this...  sold the public owned power generating industry too either way it makes sense and is not good

[dgd]

DGD, is your avatar supposed to be a Kia? its so small I cant make it out...
Q 2  did you mean too = also or to = to in this...  sold the public owned power generating industry too either way it makes sense and is not good

West..  avatar is a Chattering Lory, one of my many pet exotic birds.  The Kia is a NZ native protected species so no private ownership. too

HaHa.. well spotted too, the too should be a to too..

dgd

[Roy]

Hello and thanks to all who have made it possible for me to have a winter of waste not powered hot showers! I set it up pretty much as Chris White describes
At first I was worried about that flickering light problem but got over it until I was giving myself my self inflicted spring haircut.  The surging power to the hair clippers made me wonder what harm I may be doing to the compressors on my fridge and freezer.
Anyone?