Paul's House Heating -- Solar Shed

  Update -- August, 2008

Paul  has added a new storage tank that replaces the oil barrel based tank described below.

Details on the new tank here ...



Paul M. in Nova Scotia, Canada is building the solar heating system shown below.  In Paul's system, the collectors are mounted on a new storage shed that he is building, and the water heated by the collectors is piped to a thermal storage tank inside the nearby house, where it is then used for heating domestic water, and potentially for space heating soon.


Paul's system is similar to the one I am building for my house, and we have been exchanging ideas for several months on doing various parts of the job.  I'd like to really thank Paul for taking the time to provide the detailed photos and descriptions below!


The finished Solar Shed


While under construction -- showing pipe line from shed to house


Overview of the new shed with the solar collectors mounted.  The ditch for the pipe that brings the heated water to the house is also visible.  The storage tank, heat exchangers and pump are located in the house. 

This is a closed loop system with antifreeze to prevent freezing.


One thing to note is that by making some good decisions and looking around for bargains, Paul managed to build a complete system with substantial heating capability for hundreds of dollars rather than thousands of dollars.





The Solar Shed

Paul decided to mount his solar collectors on the new storage shed he was building.  The collectors are then connected to the house via a pipe line to transfer the hot water to the house for water or space heating.  This method has some advantages over trying to find a space on your home for the collectors.



Gravel base:
The gravel base was the first step after the ground was leveled as well as an excavator could scratch the bed rock which came up to the surface. Originally I thought I would get away with deck blocks or cement columns in the ground but a shed of this size requires a good solid base so I went with $60 for the excavator and $150 for gravel then $200 for concrete. It also involved another $80 for wire mesh and rebar before pouring the concrete. (24 X 8 feet)


Another picture of the roof without the strapping on.



The framing took a lot of 2x4s. There is a beam along the peak made of two 2x6s supported by a post and the rafters on the long roof side are made of doubled 10 foot 2x4s. Each 3x8 foot panels weights about 100 pounds when filled with water. The horizontal boards are deck flooring used as strapping. They are 1x4 inches. The metal roof screwed into this.

Me on roof:
At this point I was screwing the peak of the metal roof on. This roof was used and was just taken off a large church. It is 24 gauge steel which is strong compared to the usual 30 gauge used for common residential roofs. It was heavy to put on (my wife helped me). It was $250 compared to $500 for new 30 gauge roofing .



The Collectors

The used Collectors:
The panels were quite used when I got them, about 15 years old but in good shape. The major problem was the roofers who removed them cut the end of the manifold pipes off. I did manage to clean them and get enough pipe sticking out to resolder the threaded unions back on. I bought 12 panels for $65each (my friend took 6 of them)

Panel fittings:
The panels were designed with these threaded unions which I don't really prefer. They are difficult to get water tight unless they are new. I polished these with sandpaper and still had leaks. I ended up using a lot of Teflon tape and silicon caulking inside the union. Plumbers say you shouldn't need anything to seal them. I called the company that makes these panels and they said the only time there is a problem is if the unions are over tightened with a pipe wrench and become out of round. I know that did happen to one.


These are the threaded unions between the panels. A lot of Teflon tape and silicon caulking made them leak proof.

Mounting rails:
The panels need a good solid mounting which can allow for adjusting the position of each panel. This style of "truss" uses a nut which fits into the slot and can slide inside the channel. Once it's tightened it doesn't move. This way the threaded unions can be brought together and tightened or loosened and pulled apart for maintenance.

Panels clamps;
These are the original clamps that were salvaged from the roof they were taken from. They are shaped to fit on the rubber gasket near the glass edge.


Air Vent;
There are two manual air vents at the top of the panels to allow air collected at the top to escape. It's just like a tire valve. I will go up about once a month to check for accumulated air.

The Pipe Line

This pipe line circulates water through the collectors, and back to the house where it is used for water and space heating.

Pipe line;
The pipe line trench is only 15-18 inches deep.
(those rocks must have been fun)


Pipe insulation;
The white or clear pex pipe was given to me so I used it. It is 5/8 inch. Because pex can't handle the higher temps it is used for the return line to the panels. It's cooled by the heat exchanger in the tank and shouldn't exceed 160-180F. The other copper line is half inch. It will be the hotter line from the panels to the tank. I didn't know if the grey insulation can handle the possible 200 plus temps so I insulated first with insulating foil tape then put on the foam. 
The ground is hard and sandy, good to support the pipe. Because I'm using antifreeze the frost and cold in the winter won't be a concern.


Cement drill;
This huge drill was rented from Home Depot. It weighs about 15 lbs and the tip is for a 5 inch hole. The pipe is a 4 inch septic pipe. The extra inch is for inaccuracies in the hole angle. With a 4 inch drill the hole would have to be perfectly straight. It took about 20minutes to drill the hole.

The Tank, Heat Exchangers and Plumbing


Furnace oil tank:
This tank turned out to be the cheapest (free)  and the fastest to have complete for the project. I used a reciprocating saw, cut one end off, painted it and carried it down my basement with help from a friend. It holds about 150 gal. It is a 200gal tank in it's original state. With the top cut off it's easy access to plumbing like heat exchanger coils dropped down into the water.


Pex coil:
The heat exchanger was first made from 50ft of half inch PEX plastic pipe with the metal oxygen barrier which makes it keep it's shape when bent. It's a bad idea. Very poor heat transfer into the water. It didn't heat the water in the tank or cool the  water in the coil of pipe. So, I made a 100ft coil of copper half inch tubing about one foot in diameter and it is much better.


Tank in the corner
Here you can see how well the tank fits in the corner of the basement. It holds 150 gal. The circulator, pressure tank, pressure gauge and fill/drain valves are all here.

Filling the System:
For filling the system with antifreeze I used a common 1/6HP submersible sump pump. The pump sucks the antifreeze from the bucket. Pumps it into the fill valve through a clear hose (in the picture it's red) As the system fills it comes out of the drain line which is a green garden hose. While it's filling I watch for a  steady flow with no bubbles coming from the drain line. Once the steady flow comes I close the valves. At this point it should be full with no air. The pump will circulate easily now.


Tank and Heat Exchangers:
This photo shows the top of the tank. The output coils are visible near the top of the water and the rest of the plumbing. The circulator pump should be mounted in a vertical pipe not in a horizontal one as this because the air bubbles can get stuck in the pipe and the pump may loose it's prime and stop pumping.

The top two 3/8 inch coils are 50ft each connected together to give the equivalent of 100 ft. At the time I couldn't get it in 100ft lengths. These are output to domestic water. The larger coil (harder to see in the bottom) is 100ft of half inch tubing is the heat supply from the panels. This is at the bottom because the hot water will rise to the top where the output coils are.  Domestic hot water is pre-heated heated in a single pass through the 100 ft coil before it goes on to the regular hot water tank.  See diagram below.

Some space heating is also provided via radiation from the bare metal storage tank into the room.   Paul will probably work out a way to hook the solar heating  system into his existing radiant floor heating system for the next heating season.

System diagram



Tank with insulating cover.  Plumbing system and control electronics on the wall.

The pump is a 3 speed Gundfos 15-58U.


Controls and Instrumentation


Controls for the system.

The HI unit is a differential controller that turn the collector circulation pump on when the collector temperature exceeds the storage tank temperature by a set margin. 

The EM100 measures power consumption, and also records the pump on time, which accumulates the total time the collectors were collecting useful heat.   The cost was only $25 Canadian.



As another bit of instrumentation, Paul uses this remote sensing cooking thermometer to monitor the storage tank temperature.  Using this, you can monitor the tank temperature from up to 100 ft away.  The cooking thermometers are good for this, in that they register up to 400F -- much more than the usual thermometers.    About $50.


Additional Notes


Space Heating:

Right now the system provides water heating, and some space just via radiation from the metal storage tank.  Paul is thinking about tying this into his radiant floor heating system for next year.  The system would appear to have enough collector area to make this worthwhile.



Results to Date:

As for results, After a full sun day the water goes from about 100F in the morning to 160F by 5pm. This is about six and a half hours of sun. We washed dishes in the kitchen and filled our whirlpool tub half way with HOT water. There was still lots more. The tank still showed 125F.
Without insulation on one side of the tank I loose about 10F over night and another 10F through the day without using water. Which isn't bad because another partly sunny day brings it back up another 30-40F.


Note: the 20F total loss from the 150 gal (1245 lb) tank would indicate that the tank is providing space heating to the tune of about:  (1245 lb)(20F) (1.0 BTU/lb-F) = 25000 BTU per day just from the tank losses to the room.




Paul and Gary 10/15/06