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  1. #1
    Extreme Koi Member Rank = Hassai Frich's Avatar
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    Solar water heater experiment

    Hi

    i have decided to try an experiment with using vacuum solar heating tubes to try and keep the pond above 14 degrees during winter.

    at the moment i have hooked the system up to a swimming pool with 8000 liters, to learn more about how it works and how to control it (without boiling my fish)
    so the plan is to run the system for a year to gather data, and to build a proper control system to adjust the temperature.

    the goal is to be able to run the system and keep the pond (35000L) above 14 degrees during the winter months, without having to cover it.

    my main concerns are overheating (heat dump would need to be implemented), and large temperature fluctuations during night time.
    if any of you have any experience with this type of heating for the pond, i would love to get advice



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  5. #3
    Extreme Koi Member Rank = Mature Champion Trace's Avatar
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    Quote Originally Posted by Frich View Post
    Hi

    i have decided to try an experiment with using vacuum solar heating tubes to try and keep the pond above 14 degrees during winter.

    at the moment i have hooked the system up to a swimming pool with 8000 liters, to learn more about how it works and how to control it (without boiling my fish)
    so the plan is to run the system for a year to gather data, and to build a proper control system to adjust the temperature.

    the goal is to be able to run the system and keep the pond (35000L) above 14 degrees during the winter months, without having to cover it.

    my main concerns are overheating (heat dump would need to be implemented), and large temperature fluctuations during night time.
    if any of you have any experience with this type of heating for the pond, i would love to get advice
    I don't have any experience of panels being used the way you are ... but we do have a couple that were here when we moved in to heat water that I thought were going to be rubbish but have actually turned out to be pretty good. I will say we also just switched over to those digital grundfos pumps your using and they are brilliant ... supercheap to run compared to the old fixed wattage pumps doing the same job ..

    I'll be watching this with interest ...
    About me: Back by popular demand ...

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  7. #4
    Extreme Koi Member Rank = Hassai Frich's Avatar
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    well started up the system mid afternoon and the temperature on the heating loop reached 52 degree's and the pool water was 27,2 after the heat exchanger.
    inlet on the heat exchanger was 15,8, so an increase of 11,6 degrees at the heat exchanger.

    air temperature was 16,2

    lets see how much it drops over night and how much it can increase the water during tomorrow.

    main thing now is to test it during summer to make sure the temperature doesnt go too high, and then later to see the performance during winter with all the air cooling of the water

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  9. #5
    Quote Originally Posted by Frich View Post
    well started up the system mid afternoon and the temperature on the heating loop reached 52 degree's and the pool water was 27,2 after the heat exchanger.
    inlet on the heat exchanger was 15,8, so an increase of 11,6 degrees at the heat exchanger.

    air temperature was 16,2

    lets see how much it drops over night and how much it can increase the water during tomorrow.

    main thing now is to test it during summer to make sure the temperature doesnt go too high, and then later to see the performance during winter with all the air cooling of the water
    Very interesting experiment - please share your results as you go.

    I would think you may need rather large well insulated heat accumulation tank for Koi pond use of your solar heater setup - as day / night temperature fluctuation should not exceed 1,5 - max 2 deg. C - as otherwise it will stress your koi thus leading to greater vulnerability to sickness / pathogens / parazites attacks. Also such heat accumulation tank will assure no steep temperature rise on sunny day as you do not want too warm water entering your pond. Just food for though I guess....

    Looking forward to your next posts!
    Last edited by milaz; 09-06-2019 at 08:56 PM.
    You get what you pay for - or better - what you make yourself.

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  11. #6
    Extreme Koi Member Rank = Hassai Frich's Avatar
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    yeah will most likely have to have a heat storage tank, but thats a small problem.
    currently the main problem is controlling the temperature, basicly how to "stop" the heat on a sunny day.

    my current options is either dumping excess heat into a tank or air, or to have a shutter door roll over the tubes depending on how much heat is needed.
    but if it works, it should give me a potential of 6kw of heat for the price of 10w for the circulation pumps.

    i will need to make a temperature logger, that can log 4 temperatures, but i will look into that when i go back to work next monday. (raspberry pi)

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  13. #7
    Extreme Koi Member Rank = Jussai bowsaw's Avatar
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    I know a few folks that have bed sheets over theirs all summer as they provide way to much heat for their swimming pools in the warmer months,
    the slow pond build thread

  14. #8
    Moderator Rank = Supreme Champion Feline's Avatar
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    I have a slightly bigger scale solar experiment on the go here. I've had an 8kW PV system installed on the main house roof. It's been up and running for 3 months now and looking at what we are generating we are thinking of adding a Tesla battery wall to the system so I can run the heat pump at night rather than in the day on solar. We also have an electric car that's part of this setup.

    Since the installation I reckon we have cut our electricity bill by approx 3/4, although that won't be the case all year round. We also have a FIT so are paid for half of what we generate at the moment whether we use it or not. We have a nifty gadget wired up to the immersion heater so that if we are exporting anything to the grid it uses it to heat the hot water instead until its up to temp.

    I don't know if any of that technology can work with a system that isn't wired into the grid though.

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  16. #9
    Extreme Koi Member Rank = Hassai Frich's Avatar
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    bowsaw

    yeah that's a bit of what i was afraid off, that's why it's set up in the pool, can allways just put some cold water in if it gets too hot

    Feline

    solar panels is for sure something i have been looking at, especially because i am using ground water heating system in the house. but i have not been able to find a way to get the economy to work on them, mainly since most of my power usage is during the winter, and most of the production from solar panels is during the summer time where i have little need for power.
    there is no subsidy plan in Denmark

    as for running it "off grid" that's is defiantly possible, i set up a small system last year in Australia to run our internet microlink connection on site.

    but in Denmark the cost of solar is still quite high, an 8kw system without battery support is around 12.000 GBP, and still doesn't fix the problem with the heat at night.
    i think my best option down the road will be a small 10kw wind turbine. but that's also a bit expensive.

  17. #10
    Quote Originally Posted by Feline View Post
    I have a slightly bigger scale solar experiment on the go here. I've had an 8kW PV system installed on the main house roof. It's been up and running for 3 months now and looking at what we are generating we are thinking of adding a Tesla battery wall to the system so I can run the heat pump at night rather than in the day on solar. We also have an electric car that's part of this setup.

    Since the installation I reckon we have cut our electricity bill by approx 3/4, although that won't be the case all year round. We also have a FIT so are paid for half of what we generate at the moment whether we use it or not. We have a nifty gadget wired up to the immersion heater so that if we are exporting anything to the grid it uses it to heat the hot water instead until its up to temp.

    I don't know if any of that technology can work with a system that isn't wired into the grid though.
    Just food for thought - instead of Tesla PowerWall you may want to look at much better option from Germany - https://sonnengroup.com/sonnenbatterie/

    Recently Shell bought majority stake in this very well performing startup (generating good profit from year one - contrary to Tesla - which still has to show first profitable year I guess) - the main difference is, that Sonnen uses much better battery technology - LiFePO4 - which is much better as it allows many more charge / recharge cycles than Lithium batteries used by Tesla - check out their website and references - if interested.

    Also their system is more flexible in terms of configuration and programming to specific needs - off course all possible also via smartphone app.

    I am right now discussing it with their local installer as addition to my PV - a bit bigger than yours- 16.9kWp - three phase system I have installed on our roof back in 2009 - to use three phase Sonnenbaterie ECO 7,5KWh as buffer balancing out electricity production with demand at each phase - our house is also heated by ASHP - 14.5kW - in summer reversed for cooling as well.

    The beauty of Sonnen system is, that it is easily extended by 2,5kWh battery banks simply added to the base version if such need arises.

    Just my five cents....
    You get what you pay for - or better - what you make yourself.

  18. #11
    Quote Originally Posted by Frich View Post
    yeah will most likely have to have a heat storage tank, but thats a small problem.
    currently the main problem is controlling the temperature, basicly how to "stop" the heat on a sunny day.

    my current options is either dumping excess heat into a tank or air, or to have a shutter door roll over the tubes depending on how much heat is needed.
    but if it works, it should give me a potential of 6kw of heat for the price of 10w for the circulation pumps.

    i will need to make a temperature logger, that can log 4 temperatures, but i will look into that when i go back to work next monday. (raspberry pi)
    You would probably need two heating loops - one from solar to heat accumulation tank and second from Koi pond to heat accumulation tank - this one can be controlled rather easily - just solenoid to stop the flow from pond to heat exchanger inside your heat accumulation tank controlled by simple on / off thermostat - with 1K switching difference - solenoid should be on the same power loop with your koi pond pump pumping pond water through the heat exchanger inside your heat accumulation tank - quite simple setup easy to control.

    If you will go to wind turbine, this would give you probably greater power output in the winter than solar - given the weather pattern typical for Denmark - in such case you can also work with heat accumulation tank - this time heated by the electricity generated by the wind turbine - and solenoid controlled flow of pond water through it.

    But given you have ground heat pump, your best alternative - my opinion - would be to add desk heat exchanger to your house heating system in the place close to your pond - and run through it pond water with separate pump - again - solenoid controlled by thermostat - this is by far the most economical way of heating your koi pond in the winter - this is what I have installed two years ago - and use our main ASHP 14.5kW Zubadan to heat our house and koi pond in the winter - my ambition though being to keep koi pond at 7 dC - not any higher - during NOV - FEB - for rest of the year I have separate 5kW ASHP heating only the koi pond - to bring it fast from 7 to 15 dC in the Spring - and than maintain 21 dC JUNE - SEP.

    Desk heat exchanger.jpg
    Just food for thought I guess - good luck!
    You get what you pay for - or better - what you make yourself.

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  20. #12
    Extreme Koi Member Rank = Hassai Frich's Avatar
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    Quote Originally Posted by milaz View Post
    You would probably need two heating loops - one from solar to heat accumulation tank and second from Koi pond to heat accumulation tank - this one can be controlled rather easily - just solenoid to stop the flow from pond to heat exchanger inside your heat accumulation tank controlled by simple on / off thermostat - with 1K switching difference - solenoid should be on the same power loop with your koi pond pump pumping pond water through the heat exchanger inside your heat accumulation tank - quite simple setup easy to control.

    If you will go to wind turbine, this would give you probably greater power output in the winter than solar - given the weather pattern typical for Denmark - in such case you can also work with heat accumulation tank - this time heated by the electricity generated by the wind turbine - and solenoid controlled flow of pond water through it.

    But given you have ground heat pump, your best alternative - my opinion - would be to add desk heat exchanger to your house heating system in the place close to your pond - and run through it pond water with separate pump - again - solenoid controlled by thermostat - this is by far the most economical way of heating your koi pond in the winter - this is what I have installed two years ago - and use our main ASHP 14.5kW Zubadan to heat our house and koi pond in the winter - my ambition though being to keep koi pond at 7 dC - not any higher - during NOV - FEB - for rest of the year I have separate 5kW ASHP heating only the koi pond - to bring it fast from 7 to 15 dC in the Spring - and than maintain 21 dC JUNE - SEP.

    Desk heat exchanger.jpg
    Just food for thought I guess - good luck!
    100% correct, i would love to just heat the pond with ground heat pump. but without the wind turbine, i am afraid that the heating bill would be massive.
    the ground heater i have now is 12kw, but it is allready keeping 310m2 heated during winter and supplying the hot water. but i am constantly upgrading the insulation as a go thru renovating the house

    the biggest problem i have thou, is the fact that i did not insulate the pond when i built it. that annoys me a bit

    as for the extra heat loop, that is a must, at the moment i am just trying to collect data, in order to be able to calculate the capacity of the heat dump. and how to control it. in my head i have an idea of having a hidden insulated tank where i can store heat to heat up the pond during the night time, and basicly run the water backwards in the system to drain the heat again.

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  22. #13
    Extreme Koi Member Rank = Rokusai AlanF's Avatar
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    Hi

    I had a home made solar water heating panel running for a while but it is currently awaiting a rebuild after a few pipe problems. While it was working it added a reasonable boost to temps but I have my doubts that it would work consistently enough over a winter without back up heating to prevent too rapid cooling when poor weather blocks sun. In summer it worked too well and needed shutting down at times before it took temps over 30C. Like you, I have not insulated pond but I think that may be an advantage with solar heating as the masonry/soil act as a heat sink which smooths the day/night fluctuation. Pond is 20000L with a 1.5 M2 flat plate collector covered with an old double glazed patio door. It is mounted on a tiltable frame which means I can alter angle to maximise winter input(also used to reduce summer input if required). The whole thing rotates to follow the sun which roughly doubles the output compared to static.
    Your evacuated tubes will be ideal in as much as they will be optimal for cold weather performance, bit too expensive for me plus I enjoy the DIY element. I look forward to seeing how much heat you can extract from them and I wish you good luck. I hope to get mine rebuilt and working this Autumn ready for the winter.

 

 

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