BIG project Solar tubes to heat Pool And Garage

[armstrr]

ok, so i have just applied for a variance from my local city council to build a shop larger and taller than i am supposed to. if approved it will be 22x44'ish. the 44' side is on the south side of my lot and....faces SOUTH! ok, we also plan on installing a pool...hopefully soon. We live in Sarnia, Ontario Canada (think climate of Detroit or New York).

my original plan was to use a heat pump to heat the pool and a gas fired radiant tube heater for the shop. total combined for those two systems would likely be in the area of $6000 after hookups etc...and probably more. however, it seems wasteful to use electricity and gas to heat amenities. i would love to do it with solar even if the up front costs are a little more, i know the operational price will be virtually free. and since i have plans for the energy all 12 months, and the low temperature of the pool water and concrete slab, the system should be quite efficient.

originally, i was thinking of using Radiantec to help engineer and supply my system since they realllllllly seem to have it all together when it comes to practical approach. In fact the best reading i have found are from these two pages

http://www.radiantsolar.com/solar_technology_improvements.php

http://www.radiantsolar.com/solar_options.php

unfortunately, they won't design a system for me since they only design solar systems that include domestic hot water...and what i'm after is a closed loop. they say they ONLY use flat panels and run their solar arm as non-profit...so i'm looking for some help doing some calculations and choosing system components...or to even hear if what i want to do is feasible.

basically, i want a solar system that during the summer can dump all available heat into a swimming pool. i assume to to this i would need a tube and shell heat exchanger and the pool pump running whenever solar energy was available. i would need to find the lowest horse power pool pump since it will be running from sun up to sun down.

then in the winter, i could switch the system to dump its heat energy to the garage concrete slab and sand mass underneath the slab. i figure this could be done directly. ie, no heat exchanger...just pex tubing in the slab and in the sand underneath. just like the radiantec web page suggests...the slab/sand mass would be insulated.

so...here i am...excited about the propects of this, but not reallllly having the know how to size the system and select the components or even figure if it is feasible.

so, am i headed in the right direction, or am i crazy?

do i need to use evacuated tubes or can flat plates do the job...both for the pool and for the shop? and for the shop,

i don't need high temps for the shop. if i went for the overhead tube heater, it would only be used to heat the shop when i am woodworking, and i would only need it to be 58-60ish. i figure this will be no problem with a radiant slab system. the building will have 6" walls insulated with blown in dense packed cellulose. that should be r-24ish...and the ceiling will be 12" dense backed cellulose. so the building should be tight and well insulated. the benefit of the radiant slab is it is heated for free...and it will not have to be preheated before i go out to work, so the shop will get more use. also, if i house the pool equipment, winterizing should be less intense and if i do any work on my cars...lying on the floor will be a welcomed event.

so any input, questions, clarifications etc?

thanks in advance. i always appreciate feedback from those willing to share knowledge with people willing to learn.

[Mike90250]

You need to insulate the slab somehow, otherwise, you are putting heat into damp ground. Get planned on the PEX tubing, O2 blocker, and recirc pump.

Here's a great article on a collection unit:

http://www.builditsolar.com/Projects/SpaceHeating/SolarShed/solarshed.htm

Water based, hot water heating panels, circulating to heat house in Montana, DIY.
A small solar PV array could run the pumps for this. Switch from pool to slab with just a couple valves.

[armstrr]

thanks Mike! i just finished reading that and my head is spinning with possibilities. I thought that because of the climate i lived in that evacuated would be the only way to go. how does a drain back system work? obviouly air is somehow left in the system. i guess when i think of pluming i think of all air purged out in a closed system. i assume this would have to drain to a tank and then a heat exchanger would be required to get the heat to the slab...but that wouldnt be a big deal since i need this arrangement for the pool anyway although i was trying to avoid the expense of a tank all together...the cost savings of a diy approach would likely make up for it several fold.

and yes as for the slab, i would use at least 4" on the side of the slab and go down as far as possible and likely 2" on the bottom.

as for the pv cell...this will be a fully equiped woodworking shop, so getting electricity won't be a factor

what make/model of controller should i look at?

THANKS

[Mike90250]

what make/model of controller should i look at?

Did they list anything in the article ? A "differential" controller for a drainback system, would be what you want, I think. I don't have that system, I just envy it.

[russ]

With the evacuated tube type you will be using an antifreeze and a pressurized system with forced circulation. The heat exchanger would be in the hot water tank. The circ pump is quite small. What they show on builditsolar.com is a pressurized system.

The antifreeze loop (for the panels) and the loop for radiant heating are separated by the heat exchanger.

The tank is no big deal - just a coil inside to for the heat exchanger and real good insulation.

[armstrr]

ultimately, i guess my decission between evacuated or flat panel should come down to cost/btu. i assume diy flat panel using the prefabed heat plates will be the most economical even if i need a few more than i would if i went evacuated.

if the solarshed used a glycol system under pressure, why did he ensure that he sloped the piping? i assumed this was to drain back. i suppose it could also be to force all air to the top of the panels and to the return piping?

[russ]

The evacuated tube types are able reach considerably higher water temperatures than the flat plate.

The only drain back systems I am aware of use a head tank that sits over (above) the panels.

They do not use a heat exchanger as it is all one closed loop - from the collectors to the storage tank through the hydronic 'in floor' heating system. For use with pool water you would need the exchanger. You don't want to run anything but 'clean' solution/water in a closed loop through the collector system.

They say no antifreeze but I would not do it that way - if it ever froze due to any reason you would be in deep stuff - anti freeze is cheap. They also say no air purge valves but again. I wouldn't do it like that.

My air source heat pump generates 3.5 m3/hr of heated water - to get that volume would take a rather large amount of collectors so I only use flat panels for hot water in my present house.

[armstrr]

rereading the article. his solar loop is a drainback

"Our system is designed to be as simple as possible. It uses a design in which water drains back from the collectors into the storage tank for freeze protection. Because it uses plain water and the system is vented to the atmosphere, there is no need for expansion tanks, pressure relief valves, vacuum breakers, antifreeze or heat exchangers. The collector loop plumbing consists of a few feet of pipe and a circulation pump — that’s all. This simplicity reduces the cost and labor to put the system together, and the absence of heat exchangers increases efficiency."

[russ]

Hi Amstrr - How they make the drain back work I am not at all sure - using pressure from the mains for charging maybe?

Good luck - follow their instructions carefully - there are some parts that I would do differently but that is life. A pressurized system is easier and simpler (in the long run) to me. An expansion tank, purge valves etc are no big deal.

With the pool and the shop both you are talking about a different system. A heat exchanger is certainly required.

You do not want tap water running through the hydronic or collector sides! That would be asking for trouble!

I suggest you spend extra bucks now, build it right and enjoy life - not suffer later.

They used the type of evacuated tube where the water passes through the tube - look on the net and see the other type using a heat pipe - that would simplify the piping very much.

Not to complain about someones design but I feel it is necessary to worry about all details upfront as it is your (or my) money and time being spent. When I don't understand how or why something works I try to get farther into the topic. I have solar water heating systems in all our new homes. I would love to be able to make solar hydronic fit my situation but haven't been able to yet.

[mtmtntop]

i will give you an idea of what i did and if you think some of the info is transferable, ask me questions. I live in montana and put in an indoor endless pool- about 2500 gallons. I heat this pool and the floor of that room with a 75 evacuated tube array facing straight south. I have the opposite priority, i run the heat primarily into the pool, because the room gets alot of solar gain so it is warm by mid morning. the floor is ceramic tile on to of what is called mudpack. 2" of sand/mortar mix with pex tubing.
sounds like our difference is that this solar array shares a boiler loop and the boiler serves as a backup. right now, i use it when we have several cloudy days in a row. if it is sunny every day, i use the boiler once a week or so. i also have this hooked into my dhw but as of now, there is not enough heat to do it all. i have my array at 70 degrees to maximize it in the winter.my latitude is 46. finally, i have an air handler to dump excess heat, and an emergency loop that runs off a small pv panel in the event of a power failure it is essential to continue circulation through the tubes or they will quickly overheat. I have the last of the bugs worked out and it is virtually automatic now. if part of this interests you, feel free to ask about it. i learned this stuff the hard way and found no one that could answer my questions. good luck!

[Jason]

Welcome mtmtntop,

I wanted to say thank you for registering to share the information. I appreciate your willingness to help others on the forum.

I look forward to reading more from you!

[Mike90250]

i will give you an idea of what i did and if you think some of the info is transferable, ask me questions. I live in montana and put in an indoor endless pool- about 2500 gallons. I heat this pool and the floor of that room with a 75 evacuated tube array facing straight south.

snip

Wow, awesome project. Start a new thread if you like, and post photos and hints if you don't mind.

Mike

[armstrr]

i will give you an idea of what i did and if you think some of the info is transferable, ask me questions. I live in montana and put in an indoor endless pool- about 2500 gallons. I heat this pool and the floor of that room with a 75 evacuated tube array facing straight south. I have the opposite priority, i run the heat primarily into the pool, because the room gets alot of solar gain so it is warm by mid morning. the floor is ceramic tile on to of what is called mudpack. 2" of sand/mortar mix with pex tubing.
sounds like our difference is that this solar array shares a boiler loop and the boiler serves as a backup. right now, i use it when we have several cloudy days in a row. if it is sunny every day, i use the boiler once a week or so. i also have this hooked into my dhw but as of now, there is not enough heat to do it all. i have my array at 70 degrees to maximize it in the winter.my latitude is 46. finally, i have an air handler to dump excess heat, and an emergency loop that runs off a small pv panel in the event of a power failure it is essential to continue circulation through the tubes or they will quickly overheat. I have the last of the bugs worked out and it is virtually automatic now. if part of this interests you, feel free to ask about it. i learned this stuff the hard way and found no one that could answer my questions. good luck!

that sounds like a very nice system, indeed! yes, i am sure i will have lots of questions for you and others.

the biggest similarity we have is year round heating priorities. My first question is why you chose evacuated tubes over flat panels? (that was the direction i started looking into, but see most people go flat over evacuated).

is there an article, web page or calculator that can calculated btus harvested by evacuated vs flat? obviously the evacuated is more efficient. since i will have a large roof surface to work with, space is not at a premium, so i am after the best btu/per doallar. with manufactured tube/fin absorbers available for a diy'er to buy and build into an inulated frame, I need to calculate how many of each i would need to accomplish my goals.

the 1st step will be to determine the heating requirements for the pool and for the shop....hopefully they will be close. otherwise i'll need to figure out which to design for.

i know i have lots of reading to do and i need to/want to learn...not just have someone tell me the answers. if anyone knows of a good site to determine pool heating requirements...specifically when heating with solar and the same for radiant heating of a building, please let me know.

[Jason]

snip

Wow, awesome project. Start a new thread if you like, and post photos and hints if you don't mind.

Mike

I second that!

[mtmtntop]

its cold where i live so the insulating ability of the tubes was important. but after running this system for a year, i would point out something else that i have seen very little about anywhere else. maybe i have not been looking in the right places. anyway, these tubes can run much hotter than a flat plate setup. i have experimented with several temperature ranges to see what happens and for awhile had them operating at 175. and there is no reason they could not go higher. however, the lag time between when the pumps start and when the array starts to cool is critical to know to keep the array from getting out of control. from what i understand the flat plates will not go that high. using heat exchangers seems to work alot better with the higher temps, especially when the days are so short. i know my hydronic mudpack floor should not have glycol over 130 running in it so i have a mixing valve to keep that temp down. not sure what temp you can run in a concrete slab, but i suspect it can be as high as you want to go. but the pool heat exchanger takes the full temp of the panels and uses it.

i run glycol so i do not worry about a drainback system . i decided to eliminate that whole issue and use less efficient glycol but not worry about the pitch of my plumbing. but you should decide if you are doing a drainback system before you start either the tubes or flat plate so you make sure you can physically plumb it correctly.

Also, i never could find anyone that could figure out the btu need of the pool. it is because so much depends on the external environment. mine is indoors. the metal sides are insulated with 2" rigid foam. and there is 2" of rigid foam under the bottom slab (very important!) the surface area that is losing temperature is important. the bigger the surface, the faster it loses temperature. and two things i found that are simple but very important are the bubble wrap layer sitting right on top of the water and secondly, the pvc piping of the pool. we have the bubble wrap layer off in the summer and alot of heat is lost with just this one change. (but we have heat to spare in the summer because of the long days)
since the circulating pump is going several hours a day, all that pvc acts as a radiator. i noticed a substantial difference when i insulated all my 1 1/2 pvc even though it is in a heated crawlspace area. also, my pool has a roll up cover that fits into a track making the whole thing airtight. finally, another factor is how much and how often you add water. since this water probably will be cold, if you have to add alot of water, you have to bring the new water to temp and maintain the temp in the pool itself.
that all said, i have calculated i need 2-3 degrees of heat each day in a 2700 gal pool. its hard to know all this without the pool set up and running.

1 btu raises i lb of water 1 degree. a gallon is 8.77 lbs. so you need 8.77 btu to raise 1 gal 1 degree. so for me this is 47000-71000 btu per day (2700*8.77*2 or 3). my array is 75 tubes. i rarely have heat to dump with my tubes at a 70 degree angle. I do have heat i use in the floor, but the room does not need much due to the solar gain.

so all this is stuff to think about. it all fits together and all affects each other. If there was a table out there somewhere that said how much it takes to heat a pool, i would be wary. the factors i have talked about above have a huge impact on the amount of heat the pool needs.