Which Solar hot water system?

Getting into the nuts and bolts of wind and solar power components, installation and performance issues, ask technical questions, answers and tips

Re: Which Solar hot water system?

Postby gpigeon » Mon Nov 05, 2018 2:02 pm

Gordon-Loomberah wrote:With evacuated tubes the ambient air temp is largely irrelevant- most important is radiation intensity. They can still boil water when the air temp is only 10C if the sky is clear and the sun high enough up!


Gordon, you may well be correct in what you say, but......right through winter even with our lovely perfectly clear skies, I did not have any problem with high temps. It has only been the last couple of days since the ambient temp went to 33+ that the water has boiled again. That curtain has been up there for a couple of months but the opportunity to test it out is only just arising now.
btw...the roof angle is 26deg. + maybe?? another 15deg. for the frame and my latitude is around 28degS.Facing north!
gpigeon
Solar Crusader
Solar Crusader
 
Posts: 160
Joined: Sat Sep 26, 2009 5:37 am
Location: NSW (Northern Rivers) - Origin (ex Country Energy)

Re: Which Solar hot water system?

Postby Gordon-Loomberah » Mon Nov 05, 2018 2:15 pm

In winter the sun is above the horizon for a lot shorter time, and at a lower angle, so not face on to the tubes, plus extra atmosphere for the radiation to travel though, scattering and absorbing the light, so any SHWS is less likely to get super hot in winter, even with clear skies. Rapidly increasing day length around the spring equinox will change things significantly though. I've had boiling water in mid winter in my hydronics evac tube system when not using the hot water.

I've had the 30 tube hot water system more than half covered with 70% shade cloth since August, when the pressure-temperature relief valve started releasing water - something we've had very little of this year, having to cart it from about 35km away in town :(
http://gunagulla.com Loomberah weather and astronomy including live solar radiation intensity and UV + Gunagulla aquaponics, organic eggs and cherries
User avatar
Gordon-Loomberah
Community Moderator
 
Posts: 5754
Joined: Thu Sep 24, 2009 9:41 pm
Location: Loomberah NSW Australia

Re: Which Solar hot water system?

Postby australsolarier » Mon Nov 05, 2018 2:23 pm

the diversion feature on my heatpipe system (100 pipes, 3200 liter hot water storage) kicks in too in the winter when no hot water for heating is used. i heat now mostly with the air conditioners as i have plenty of solar panels. however on really cloudy days i can fall back on all that hot water.
i have however also programmed the timer from 3am to 7am to run the radiators when there is plenty of hot water available, just so not to "waste" it. (solar electricity is "wasted" then atstead.
when things get really tough, i light the wood cooking stove. this is about 2 x a year. but could easily be tided over with no major consequence.
australsolarier
Solar Crusader
Solar Crusader
 
Posts: 483
Joined: Sun Mar 28, 2010 9:27 am

Re: Which Solar hot water system?

Postby gpigeon » Tue Nov 06, 2018 5:40 am

australsolarier wrote:the diversion feature on my heatpipe system


Mornin' "australsolarier"....what is this "heatpipe" system you have? How does it work? Do have a sketch of it?
What aircon system do you run from your off grid system? I am thinking of getting a split system from Harvey Norman or others.
Thanks.
Bill.
gpigeon
Solar Crusader
Solar Crusader
 
Posts: 160
Joined: Sat Sep 26, 2009 5:37 am
Location: NSW (Northern Rivers) - Origin (ex Country Energy)

Re: Which Solar hot water system?

Postby australsolarier » Tue Nov 06, 2018 2:48 pm

gpigeon,

i just run normal split reverse cycle aircons. 2. the smallest size i could get. good quality, panasonic. (small sizes are more energy efficient)(another aircon in the power room to keep the electronics cool). each is about 1500$ with installation. 500$ there of is installation cost. you could probably safe this if you know what you are doing, requires a vacuum pump.

heatpipe, vacuum pipe, different word for the same thing. the 100 heatpipes heat up the two tanks via a circulation pump. the controller can vary the speed of the pump. when 82 C is reached at the top of the tank the controller activates a relay. this turns on the bypass pump and opens a shutoff valve to the bypass loop. this loop travels to an outdoor stainless steel tank. dips into it and then goes back to the manifold of the vacuum pipe assembly. as a consequence the water in the tank does not go much over 82C.
i was considering about manually covering up heatpipes in the summer. but. humans are humans. you forget to either cover the pipes up or uncover them.
the vacuum pipes, the stainless steel tanks and the solar controller are made in china. no problem so far with that side yet. the circulation pumps are a different matter though. i removed the made in china pumps and installed grundfos pumps. they are quieter, use less power, don't rattle with pwm speed controll and don't stall when you tap them with the screw driver.
there is a fourth pump to circulate water to the solahart tank. (a loop in the hotwater tank. so when the sun doesn't shine for a day or too i can move heat from the large tanks to the small solahart.) another pump is used for the radiators.

with hindsight, and if you start anew. i would do floor heating.
with more hindsight i would have spent the money in more pv, etc and skipped the hydronic system. it was however much fun to build and turn out to be very reliable after some fine tuning and mods. it also acts like a battery insofar as it keeps heat for a few days. and makes for redundancy. also heating at night or in early morning doesn't discharge the battery.

i have come to the conclusion domestic hot water is most efficiently and financial wise heated with a heat pump from pv. pv works heaps better in cloudy weather than hot water panels. and in the winter.

as for the schematics, it is fairly basic stuff. any manual for a hot water controller should have a drawing.
australsolarier
Solar Crusader
Solar Crusader
 
Posts: 483
Joined: Sun Mar 28, 2010 9:27 am

Re: Which Solar hot water system?

Postby Tracker » Wed Nov 07, 2018 6:52 pm

just run normal split reverse cycle aircons. 2. the smallest size i could get. good quality, panasonic.


So you start with a conventional Air-Cond device and suck the heat from the return pipe which would be typically HOT, from the heat removed from the property.. or
are you using a dedicated Air-Cond to simply heat water ( Like the old Conergy System )

How do you couple to this pipe if you are using a conventional Home Air-Cond and recovering the heat.. Do you have an extra length of pipe running thru a heat exchanger..

One assumes that you never use the Air-Cond for heating as that same pipe would be cold, during heating..

..
.
Retired Engineer and keen PV experimenter - Always ready to learn and share.
2 x CMS2000 (fan cooled) GCI and SE 170W panels
1.7kW First Solar/Outback Island circuit - Peak Replacement Power
Governments won't save the world :-) They will just TAX it :-(
Tracker
Solar Crusader
Solar Crusader
 
Posts: 5111
Joined: Wed Sep 23, 2009 5:54 am
Location: SYDNEY --- EA - Network, Retailer - EA

Re: Which Solar hot water system?

Postby Tracker » Wed Nov 07, 2018 7:00 pm

..
There is another and cheaper method, that I use..

That is the Catch-Power system that uses "Excess Power" that would otherwise, go to the grid, and use that to heat a storage HW tank.. (Then use GAS to boost when needed (LIKE TODAY - where NO ENERGY went to the HW tank)

The only issue is that you don't have the heat amplification of an A/C system, but it is super simple..
..
.
Retired Engineer and keen PV experimenter - Always ready to learn and share.
2 x CMS2000 (fan cooled) GCI and SE 170W panels
1.7kW First Solar/Outback Island circuit - Peak Replacement Power
Governments won't save the world :-) They will just TAX it :-(
Tracker
Solar Crusader
Solar Crusader
 
Posts: 5111
Joined: Wed Sep 23, 2009 5:54 am
Location: SYDNEY --- EA - Network, Retailer - EA

Re: Which Solar hot water system?

Postby australsolarier » Thu Nov 08, 2018 5:57 am

tracker,
you misunderstood my air conditioners. the take the heat from the air. so the vacuum pipe space heating system and the air conditioners run parallel not in series, so to speak.
was however thinking using a heat pump to boost the water temperature in the space heating system if the temperature gets low. this is probably more efficient then what i have now. (the problem is finding an air conditioner trades man that is willing to understand what i am doing, and then is willing to do what i want without costing a years income. i already have a heat pump for this purpose. needs to be connected to an exchanger though.

and, i am not worried about electricity being fed into the grid and "wasted". i am concentrating on getting by when the days are short and dark overcast. that is when you need "most". so your diversion electric hot water device will not do any water heating at all. i still want hot water in overcast. and a warm house in the dark overcast.
the diversion thing saves money though. but is costly. so i think hot tank with heat pump is still cheaper in the long run.
australsolarier
Solar Crusader
Solar Crusader
 
Posts: 483
Joined: Sun Mar 28, 2010 9:27 am

Previous

Return to Components, Installation And Performance

Who is online

Users browsing this forum: No registered users and 2 guests

new solar power specials