Solar space heating in Canada

[randen]

I had recieved some requests from some fellow eco-renovators for some more details of our solar install with some pictures. If it may help any others who are thinking of solar space heating we have had some very good results.

Four years ago the decision was made for our family that burning furnace oil was no longer an option for us. The cost sky-rocketed. Our home is 11 yrs old with heated concrete floors. Although the heating method was extremely effiecient we couldn't afford it. We had to find a better way. Some research resulted with Geo-thermal GSHP and some solar hot water information popping up. Only finding one example at the time and many people blogging about solar hot water space heating, it seamed plausible that one could heat their home. Noticing just one sunny day and with our southern exposure the air temp in the house would climb about 4 deg.C. One other trick we had already taken advantage of was utilizing black floor tile to absorb any solar gain thru the windows. And it is amazing in the dead of winter how warm that concrete floor gets with that sunshine. Hey, "this solar heating could work" We fully realized that solar won't supply all our heating requirments so GSHP would be the most economically to operate back-up.

The same time period that the oil prices spiked we found our home needed some major repairs. During the original construction, the stucco was not installed correctly and had become loose. With that the windows and structure had become damaged with moisture and all became rotten. All had to replaced. It was a very expensive and heart-breaking time that our relatively new home needed massive repairs due to ignorant contractors. The only up-side was the installation of solar hot water panels could be done as an integral part of the re-constuction therefore all the tubing could be routed within the insulated wall. It made for a really nice looking install as the solar panels are set into the new stucco/styrofoam.

A Geo-thermal contractor was hired to install the geo-thermal in Sept. 4 yrs back. We removed the chimney and all things related with oil. The oil fired hot water tank was retained and a hole with a 1" pipe fitting was welded into the side to install a heating element. This was to provide domestic hot water for 3 months until the rest of the system was installed.

During that time I had constructed a combination Solar/geo-thermal buffer tank. The tank is actually two tanks one on top of the other sharing a common partition between. The tank has the top portion for domestic hot water with a electric element and copper heat exchanger for the solar input. The bottom tank that shares the partition and has a copper coil for the solar input as well , 6 electrical heating elements (for future wind energy dump) and the input for the GSHP. The really neat thing is the shared partition between the top & bottom tank is: the heat from the GSHP warms the top domestic tank with in-expensive heat. And if need be can be further heated with the electrical element. The tank is made entirely of stainless steel and insulated with 3" of rock wool with a polished stainless jacket. The lower tank recieves the hot water from the GSHP or from the copper solar heat exchanger and circulates it thru the hydronic floor heat.

Randen

[randen]

The installation of the solar collectors started with two purchased panels. (Solcan Canada)(Very Helpfull) They were installed vertically on the exterior wall between the patio doors. After reading about Garys solar shed (Builditsolar) and vertical collectors being a good thing for not collecting too much heat in the summer months and most heat during the winter months with the sun being lower angle, vertical mounted they were. (Thanks Gary Good advice)

The planned solar install was for 240 sqft of collector. I had decided to make my own panels to complete the install. It ended up taking me 3 years to get it all completed with all the other constuction going on. I did it in stages; 1st year 2 panels the results were on a really sunny day I could warm the floor about 2-3 Deg C. 2nd year added 4 more panels and WOW with the six panels we were able to heat the floor through 6 deg C. This would mean again on a really totally sunny day we would have enough heat to warm the concrete floor up and it would keep us warm till the next day to maybe get the next recharge of heat. This would be without any heat input from the GSHP. (FREE HEAT FROM THE SUN) Now the problem was not everyday is totally clear, some clouds do occure. There are some days with some thin high overcast that also reduces our solar gain. One other problem during the 2-3 weeks around summer solstice June 21 We were not always able to collect enough heat for the domestic hot water with the sun being directly overhead. The solution is for the last solar collectors to be able to be tilted. So far this tilted panel is performing exceptionally well. I'm seeing a difference of 10 deg.C. between the vertical and tilted panels.

In true eco-renovator style the panels that I had made were from some recycled materials. As mentioned in some other postings the risers were from the furnace oil supply lines straightened and soldered to copper fin purchased from the scrap yard. The tilting solar panels tempered glass is from the patio doors that had to be replaced. The stainless frame material is also from the scrap-yard.

The temperatures that are in the photos are average. The temps on the fluke multimeter of 53 deg. C.(photo wouldn't fit) are sometimes seen up to 66 deg. These are the glycol temps. from the panels. The temps on the Taylor are the domestic HW and usually finish the day 50+ deg. This would be 250 Ltr (60 gals.) of hot water till the next day. Lots for morning showers.The temps on the Rancor are for the floor heat and depending on the zones requiring heat. The supply temp can be anywere from 28 to 50 deg. (The set temp for the GSHP is 43 deg C) During the depth of winter a floor temp of 32 deg.C. is very nice and over night it may drop as low as 25 deg. C. but still comfortable. That would relate to an air temp 24 to 20 deg.C.

The controls are fairly simple with a differential controller. By about 10 O clock in the morning the pump may start. This signal also operates a timer/relay to open the circuit for the GSHP. This timer is set for 30 min. In the event that a cloud may roll by and the solar circulation pump stops momentarially we wouldn't like the GSHP to start. But 30mins after the sun is no longer producing enough heat the GSHP starts, if there is a requirement from the floor thermostats. But if we have recieved lots of solar heat the floor temps are above the set temps so no requirement for the GSHP to start.

For the last 3 weeks the GSHP has been switched off with the exception of 2-3 days (overcast) both domestic and space heat has been via solar. NICE. If anyone is thinking about solar heating it works. But the key things: The house needs to be very well insulated and air tight. 10-30 % solar collector per sqft. of floor space. For us, concrete floor for heat retention. Other source of heat for back-up is nessisary. DIY is possible with great results.

Randen

[sunspot]

Wow! Nice work. Great write up too. Thanks for taking the time to put that post together.

What size is the rough in plumbing to the collectors?

Thanks, Greg

[Daox]

Very nice write up! Thanks for the info.

What is your home's square footage? How well is it insulated and do you know your ACH?

I'll be installing 200 sq/ft of collector this summer and I've calculated I'll get ~25% (based on past natural gas usage and historical sun information) of my heat in December (worst month) from the solar array. Of course that number will increase as I seal up and insulate the house better. In summer I plan on having more hot water than I know what to do with. I'm planning to mount my collectors at 70 degrees.

[randen]

Happy new year.

It is now 6 yrs since we had installed the solar hot water system. It has performed well for all those years. We had the odd hiccup but nothing bad. A hose-clamp needed tightening, add a little more anti-freeze. Nothing serious.

The last couple weeks I happen to notice the heat-pump was running a little longer Hmm. About 8:00pm one night I went and felt the tube up to the solar panel- it was HOT -Oh not good.

Thermal syphoning heated back out to the panel. The problem is a sticky zone valve. My hard earned heat heading back to the heavens.

That night with outside temps of -18 Deg. C. was actually overpowering the geo-thermal heat-pump and cooling the homes heated floor.!!

A while back I had purchased a couple circ. pumps one for the shop and the other for our homes solar hot water system. Both pumps installed on the home solar collector and the shops DIY HP were used (inexpensive) and had lower flow rate curves. The change out was on my to-do list but up until now I hadn't found the time to change them out. So here's the impetus. Since I have to open the system to change the valve out anyway.

These new pumps are a larger capacity pump three speed Grundfos. (U26-99). I had found that lots of hot water was available but isn't pumped to the heat exchanger. I did consult flow charts and panel extrapolation of collector area and there seems to be a lot of wiggle room for the pumping capacity.

I had also run my idea by Mikesolar who does this for a living and he did question my endeavor. He did say that over capacity pump will not move anymore heat if its not available and if the heat-exchanger is not large enough. All the components of my system are DIY and the engineered data is a little vague. My other defense to change the pumps out is the used components have done their duty and hopefully the new pumps and valves will last a long time before causing me grief. The only other downside is the pumps do require a few more watts, but that's only a few more pennies a day.

The current performance heating my space is this. A bright cloudless day will provide enough heat that the heated concrete floor will carry us though 24 hrs without the back-up Geo-thermal HP starting. This is while outside temps are around the -10 deg. C. which is about average nightly winter temps. However much colder with wind and we may have the HP start before the next morning.

My thoughts are that increasing the flow will offer more heat up to the in floor heating. So possibly on the less than ideal partly sunny days I will get that whole day heat charge.

Now the last detail of the system up grade is another differential controller to the domestic hot water circuit. This will close the solar heated return as the temp. slowly falls as the suns energy tapers off in the late afternoon. As it is the valve was on the same circuit as the floors buffer tank and it would continue to supply heat to the floor and operate from a temp at high noon close to 60 Deg C. down to 36 Deg. C.

With this additional differential controller after the domestic hot water tank has peaked the valve will close maintaining the 60 Deg C. and not follow the heated floors buffer tank down to the lower temps.

As I had mention the system has worked flawlessly for many years saving many dollars and in true DIY fashion the system can be improved.

If there are eco-renovators on the fence it works well.

I would also like to thank Gary Reysa over at Builditsolar for his inspirational work.

Randen

Photos yard view of the panels, grey pump changed out to the larger red, replacement valve above red pump, differential controller mounted to valve

[pletby]

Thanks for the update! I've read your thread several times and am glad to hear how your system is performing.

[SDMCF]

Let me add my 2 cents to this topic, since my system is similar but different. Similar in that I have both solar and GSHP and I use the solar for both space heating and hot water. Different in that the solar and GSHP are coupled in an entirely different way.

My solar collectors are 100 evacuated tubes, vertically mounted on the (south-facing) end of my house. The hot fluid from the panels can be diverted to one or both of two heat exchangers (or to pipes under our front steps to clear ice & snow).

The house is heated with radiators and one of the heat exchangers is connected to the return line from one of the radiators. This way the heat gets into the space heating system for the whole house and the GSHP just sees the return flow being warmer and so doesn't need to run, or doesn't need to run so much.

I like this approach because it is simple. Heat collected by the solar panels contributes to our space heating and reduces the GSHP run time, but does not require any link between the solar kit and the GSHP other than the heat exchanger. Either one can and does operate independent of the other, with no conflict.

Our use of radiators rather than under-floor heating is because this is an old house which already had radiators and retro-fitting under-floor heating was not a practical option. Under-floor heating would be better, but the radiators do work OK.

The second heat exchanger I mentioned is used to put the heat into the DHW system. That is not used so much for various reasons.

The solar panels produce about 7000 kWh per year and most of that goes into space heating. Ours is a large old house and in our climate for most of the year we can use all the solar heat we collect.

We installed the solar panels in 2005 and the GSHP in 2007. Both have been reliable until now, but we currently have problems with both. The GSHP currently only runs for an hour or so and then gives an alarm. I believe the pump which circulates fluid through the field loop is the culprit. A replacement is on order and we should have that on Wednesday. Plus the fluid in the solar panels froze. It has anti-freeze in it and has been fine for years, so why did it freeze now? I don't know. I have it thawed out now and I'll get more anti-freeze today. Losing either of these system would be awkward but losing both together when the temperatures have been around -30C (-22F) has been a pain. So just at the moment things are a bit chilly but overall both the solar panels and the GSHP have been good investments.

[pletby]

Originally Posted by SDMCF

Plus the fluid in the solar panels froze. It has anti-freeze in it and has been fine for years, so why did it freeze now? I don't know. I have it thawed out now and I'll get more anti-freeze today..

Hi SDMCF, I was wondering how often you replaced your anti-freeze since install and what strength you were mixing at. I suppose if it hadn't been replaced regularly that could be the reason for the freeze.

Did your panel or plumbing sustain any damage from the freeze?

[SDMCF]

I have never replaced the anti-freeze as such. On occasion I have changed the plumbing around a bit and have topped it up then, but I have no good measure of its strength. All a bit disorganized really.

How often should I replace the anti-freeze?

There has been no damage caused by the freeze. By pure chance I caught it before it froze too hard, and thawed it out. (Today was warmer anyway (-15C) so no repeat problem). I happened to be checking the system because of the GSHP problem, plus it was the first bit of sun for ages and I was hoping for a significant contribution from the solar panels.

[randen]

Daox

Its been a number of years and you had tabled a question (04/26/2012) the home has about 1800 sq ft on the first floor and about 3600 total Plus a heated garage of about 600 sq ft but we don't warm it to room temp.

The insulation is R 36 in the walls and R50 in the roof. The ACH has been tested at 1.9/hr

Did you get your 200 sq.ft. up and was it what you had expected.?


Randen