solar (water) collector on roof - tank in house - pump Q.

al128al128 Solar Expert Posts: 65 ✭✭✭✭
Hi there,

I plan on having some 200ft2 (20m2) of hotwater solar collector (probably a trickle system) on the roof that feed a 500gal tank inside the house ... similar to the solar-shed on builditsolar.com

the roof will be some 9-11 ft above the tank

I am currently looking into pumps and leaning towards the shurflow 8000 "solar" series ( http://www.shurflo.com/pages/new_industrial/industrial/solar/8000.html ) , as those are rated pretty high temp wise (aprox. 75°C)

- but I am open to suggestions and input

any guesses/thoughts/experiences on what pump to get?

can I run those directly from a PV ? (or would I need a bat. in between to keep voltage around 12V)?

thx for sharing your thoughts,
al

Comments

  • BB.BB. Super Moderators, Administrators Posts: 32,220 admin
    Re: solar (water) collector on roof - tank in house - pump Q.

    I would suggest reading through the links in this post...

    This specific link is very interesting. Guy installed solar hot water (with backup) in his barn. Very detailed, with parts lists, and photos how he installed everything... Including his mistakes (causing problems with trapping air and wrong pump orientation causing shortened pump life).

    Yes, you can run some pumps directly from a solar panel, and the guy I just typed about made (and is now selling) his own low power thermal controller that runs off of battery/solar (don't know anything else about guy or his products other than what I read on his website).

    -Bill

    Guess I should ask--you will have two different pumping systems... One for the solar panels and one for your home heating loop? So--you can probably get away very nicely with solar for your solar panel loop--but would want a battery powered pump for the home heating loop--unless you can get thermal siphon to work (probably not).
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • al128al128 Solar Expert Posts: 65 ✭✭✭✭
    Re: solar (water) collector on roof - tank in house - pump Q.

    thx BB:

    I am well aware of both links - as a matter of fact the solar-shed project was a great inspiration.

    OK, here is my masterplan:

    I will be building a passive solar house next year and I am currently testing some prototype "trickle" collectors (to be installed on the roof) that will feed a large tank that will be w/in the house.

    During the summer and on sunny winter days (when no heating is necessary) the tank will be isolated to R20 with a heat loss of aprox. 1-3ºC per day ...

    During longer periods w/out sun in the winter, the isolation will be selectively reduced to liberate heat into the house - anywhere from 5kW to 40kW worth of heat per day (loosing 3-7ºC per day of tank temp). At least this is my current plan. The tank could be called a "thermal battery" within the house.

    and from the tank i need a pump to get the water circulating through the collector on the roof (flows back into the tank at night). this was my original Q.

    the tank would also sirve to pre-heat (heat exchanger) our hot water (shower, etc...)

    I envision this tank similar to a masonry heater, a place where you could sit/lie on ...

    any thoughts or observations (do's dont's) are highly welcome.

    al


    ps: for what its worth I do live in Santiago, Chile, with a rather meditaranian climate, hardly ever any freezing temps in the winter (I guess similar to SF)
  • icarusicarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: solar (water) collector on roof - tank in house - pump Q.

    I have had good luck with shurflo's in many forms, although non in continuous duty. My only comment is that the diaphram pumps are quite noisy. My submersible shurflo makes a pretty good low hum, even though the pump is 125' from the p-tank, with plastic pipe. The smaller shurflos in pressure service can really rattle the pipes.

    Tony
  • BB.BB. Super Moderators, Administrators Posts: 32,220 admin
    Re: solar (water) collector on roof - tank in house - pump Q.

    Unless you need the high pressure of a diaphragm pump--I would probably want to look at ones designed for circulating hot water--rated upwards of 120C or so...

    With the 75C pump--you would probably need to put some sort of limit switch in with the pump to prevent hot water damage...

    Plus, to drive the water into your home/space heaters, it is probably better to pump under pressure the hot water (probably over 75C) than to try and draw water/vacuum using the diaphragm pump.

    My two cents worth.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • al128al128 Solar Expert Posts: 65 ✭✭✭✭
    Re: solar (water) collector on roof - tank in house - pump Q.

    again, thx for your thoughts ...

    the problem with circulating pumps (Ivan "El sid", etc...) seems they dont have enough head to drive water from ground level to the roof ... the biggest El Sid has 4ft of head ...

    fwiw (and future reference): here is a good link with suppliers of pumps

    http://www.builditsolar.com/References/Suppliers/SolarHeating.htm

    I will dive into those a little further during the weekend and report back any findings ;-)

    cheers and again thx!
    al
  • mike95490mike95490 Solar Expert Posts: 9,462 ✭✭✭✭✭
    Re: solar (water) collector on roof - tank in house - pump Q.

    when all the air is "purged" you are just moving water, and there is no "Head" anymore. You may have to use a vacuum of some sort at the high point to start/prime the system, but once ALL the air is out, you should be fine. Also, as "Head" goes up, flow rate goes down, so it may take minutes to get the pipe pumped up, but it may still work. Or the pump could be placed higher in the system (but it won't self-prime)
    Maybe 2 pumps, in parallel, one to "start" and the other to maintain.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • BB.BB. Super Moderators, Administrators Posts: 32,220 admin
    Re: solar (water) collector on roof - tank in house - pump Q.

    I would guess that you are not using Anti-Freeze in your system?

    If so, then how will you manage the very occasional freeze? The two main types are Drain Back and or using a Thermal valve that opens when the water drops below ~2-5C and "leaks" cold water out--hopefully to be replaced with warmer water from the tank/plumbing system in the home...

    In both cases, you should probably be pressurizing your system (use your domestic water pump, or the diaphragm pump to pressurize), and just using the pumps as circulatory--so head at the collector does not directly mater (except when you first pressurize the system--and have a good sized Air over Water Expansion Tank)--As Mike says. Vapor locks and air locks are quite a problem in these types of systems and should be accounted for.

    You probably don't want an unpressurized system because the water can easily boil on a hot day (especially if there is a vacuum in the collectors/system distribution somewhere).

    I am not sure exactly what a "trickle" collector is--so I don't know how the above suggestions/observations would affect your design.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • icarusicarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: solar (water) collector on roof - tank in house - pump Q.

    I have built a couple of simple flat plate collectors that live in freezing climates. Using potable water, I control freezing with a pair of of solenoid valves. (I have used washing machine inlet valves because they are cheap). The collector pump is controlled with an aquastat. During non freezing weather, I by pass the solenoid valves so that they don't draw power. During freezing weather, when the pump quits, the valves open, depressurising the system. A low point drain is installed that opens ~5psi. A radiator automatic vent valve is installed at the high point to bleed the air out when it refills when the stat calls for the pump.

    I use a small 1/25 hp 80 watt grunfos pump to circulate the water.

    Tony

    PS This is not at my off grid location, but built as a beta for a on gird friend.
  • al128al128 Solar Expert Posts: 65 ✭✭✭✭
    Re: solar (water) collector on roof - tank in house - pump Q.

    Hi folks - good discussion ...

    a few things that I feel necessary to clear up ...

    the system I envision is an open - drain-back - non-pressurized system ...

    - the tank will be "open" (i.e. non pressurized) something like this - but nicer - and of course with lid:-) Again, it will also be the "thermal battery" that should perform heating duty on non-sunny winter days by being stripped of its isolation

    SolShed0610160015.JPG

    - there will be tubes going up to the roof where the open trickle collectors are ...

    MTD.ht2.jpg

    MTD.ht4.jpg

    a simple way to describe a trickle collector is water running down a black corrugated sheet of metal roofing material (behind glazing). At the lower edge of the collector is a sump where the warmed water is being picked up and delivered to the tank.

    - if you allow my an analogy: its like having a pond in the living room, where water is being pumped up to a waterfall that pours water over hot rocks and then this water is being picked up again and stored in the (now also warmer) pond.



    So - pls correct me - this system will always have "head" against which the pumps have to work.

    There will be no glycol in the system, as the pumps will be PV driven and water will flow back into the pond upon sunset.


    The reasons for the open system is that I want to keep things as simple as possible, without any expansion tanks, valves, etc ....



    any thoughts on the system? ... I am currently prototyping the trickle collectors, but of course the darn bilge pump I used [email protected] out on me


    again, thx for hanging in there with me

    Al
    Chile
  • mike95490mike95490 Solar Expert Posts: 9,462 ✭✭✭✭✭
    Re: solar (water) collector on roof - tank in house - pump Q.

    > trickle collectors

    Looks like a grand solar still. With all the open air in them, expect to loose a lot of your heat, as the water evaporates off. (even if the glass is sealed on, you will have a still, not a heater !)

    If you invest in some copper 1/4" tube (20' coils) and bond (solder) it to your plate, that will be a great improvement in collection gain.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • al128al128 Solar Expert Posts: 65 ✭✭✭✭
    Re: solar (water) collector on roof - tank in house - pump Q.
    mike90045 wrote: »
    > trickle collectors

    Looks like a grand solar still. With all the open air in them, expect to loose a lot of your heat, as the water evaporates off. (even if the glass is sealed on, you will have a still, not a heater !)

    If you invest in some copper 1/4" tube (20' coils) and bond (solder) it to your plate, that will be a great improvement in collection gain.


    not really true - here are some good links to read up on the materia ....


    http://www.geocities.com/davidmdelaney/shurcliff/shurcliff-trickle.html - a good discussion of the overall principal


    www.ece.villanova.edu/~nick/Solar_Heat.pdf - a customs station on the US-Canada border that uses this concept for 20+ yrs


    http://www.builditsolar.com/Experimental/MTD/MTD.htm - exhaustive info on some prototypes (ver 1.0 and 2.0) - very visual ...

    quote: "
    The spreadsheet below provides performance data for one sunny, mid-winter day. The performance is for a bank of 6 collectors, three of the collectors are Version 1 and three are version 2. It appears to me that the performance is quite good, and very comparable to high quality commercial collectors.




    happy reading!

    cheers
    al
  • icarusicarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: solar (water) collector on roof - tank in house - pump Q.

    Interesting concept. My initial reaction was the same as Mikes,,,evaperative loses would be terrible, but as I think about it now, (without reading all the links however!) perhaps it gains efficiency because of the when the change of phase , the gross number of btu's absorbed is greatly increased. (I don't remember my physics, but if memory serves, the amount of energy required to turn water to steam, ice to water was huge. I'm sure someone smarter than me will chime in).

    My area of concern would be contamination of the water course over time with micro-organisms, or algae, that could contribute to air born hazzards. Another area of concern would be freeze protection. In the case of the customs house link it isn't clear how it is freeze protected.

    Tony
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