Solar Water Heating in Northern BC

Solar water heating works very well in northern BC. Solar water heating does not require hot temperatures. With the proper equipment, it will work extremely well at -30C as long as the sun is shining. Solar thermal collectors come in three varieties, unglazed for pool heating, flat plate, and evacuated tubes. Flat plate collectors have a single layer of glass between your hot water and the outside air. Therefore, they produce little hot water during our cold winter months but work great in the summer. Evacuated tube collectors have a double glass wall with a vacuum between the two layers. This vacuum works like a Thermos bottle, insulating the heat collection surface from the outdoor air temperature. They work amazingly well in cold temperatures.

November, December, and January are our poorest months for solar energy production. By the time February rolls around, it is still cold but the daylight hours are increasing and we get less cloud so solar production starts climbing rapidly. For more details, look at the performance data links below.

You may have seen the book called "Solar Hot Water Systems - Lessons Learned 1977 to Today" (published in 2004). The book contains a lot of useful information and the author, Tom Lane has great credentials with one exception. He has never lived in northern Canada. Tom is no fan of evacuated tube collectors but then his solar water heating career has been spent in the southern United States where flat plate collectors are the appropriate technology. That is an entirely different climate than ours. Here, evacuated tubes are the appropriate technology. Apricus is a manufacturer of both high quality evacuated tube collectors and flat plate collectors. They are available from a plumbing wholesaler in Prince George so any plumber in the area can get them. For more information, go to the Apricus web site.

Solar photovoltaic, (PV) systems can also be used to heat water using electricity. Until recently, the price of PV modules (formerly called panels) was much too high to use for this job. However, that has all changed in recent years and a case can now be made for using an electric water heater on a grid tied PV system. Doing this has several advantages but the major one is that you don't have to run insulated plumbing from the basement to the roof and add a second pre-heat tank to the system. Heat radiating from the second tank, the pumping station, and the pipes also adds more heat to the house in the summer when you don't want it. With a PV system, there are no changes at all to your plumbing system.

One source estimates that adding just 6 solar modules to an existing grid tied solar power system will supply enough energy to cover the annual cost of water heating. Depending on the system, that could be done for as little as $3,000 compared to roughly $8k for a new solar thermal system. Of course, if you don't already have a PV system, it will cost more than $3k.

I tried to verify the six module number but found that statistics on how much hot water people use are virtually non existent. For one thing, water heaters don't come equipped with data loggers and secondly, everyone's habits and routines are different. I have met two women in my life who say they "fill the tub" and soak in it every night, then shower when they get up 7 or 8 hours later. This is so wasteful that when one of them installed a hot tub, their energy bill actually went down! Don't get me started on people who install shower stalls with 7 shower heads! Obviously six solar modules won't cover their excessive wastefulness. The best usage data is just estimates and they vary widely. Of all the estimates that I looked at, the daily average seems to be about 66 liters per person or 130-175L per household. this works out to about 3,400 kWh/year (283 per month or 9.4 per day). Using those numbers and the solar performance data for this area, the estimated 6 PV modules is a realistic minimum as long as they are large modules rated at 250 watts or more.

Solar Space Heating Information

This Apricus evacuated tube solar hot water collector is located at 53.5 degrees north latitude, near Prince George, BC. The 30-tube collector is mounted on an Apricus stainless steel frame which is tilted to optimize production during winter months. This angle also reduces the output somewhat during the summer to prevent over heating. The house is not situated at the ideal angle so the collector faces a few degrees east of true south.

The steep angle helps the snow to either slide off the collector or to not stick in the first place. During the winter of 2008-2009, the first winter of operation, the area received a total of about 1.2m (4 feet) of snow but only two days of hot water production were lost due to snow on the collector.

The winter performance of this collector has far exceeded the owner's expectations. In February, there were over 3 weeks of clear cold days with overnight temperatures dipping to -35C and daytime highs of around -20C (zero on the antique scale) With two people in the house, and 300 liters (80 US gallons) of hot water storage, it was almost  sufficient to carry over the few cloudy days in that month. 

Another unexpected benefit of this high mounting angle is that in the summer, late in the day when the sun is behind the collector, it shines on the back of the tubes and the collector keeps producing hot water.

2011Performance Data
2010 Performance Data

2009 Performance Data

This flat plate solar domestic hot water (SDHW) system is located in the College Heights subdivision in Prince George. The collector is mounted on the garage roof, facing south-south-west. The low angle relative to the sun optimizes hot water production in the summer when the sun is the strongest. The flat angle and asphalt roof don't help to shed the snow.

The collector feeds a drain-back system to preheat the water that is fed to the existing natural gas water heater.

Winter performance is almost zero but without a data logger in the system, we don't have any scientific data on its performance.

This Enerworks flat plate collector installation in the Hart Highlands subdivision of Prince George was a challenge because of the 12/12 pitch (45 angle). We had to work off ropes and scaffolds and over the skylights.

Being flat plate collectors, winter performance suffers.
 Performance Data

The Enerworks package added to a standard electric hot water tank makes a nice neat installation.

Most pumping stations are designed to be mounted on the wall and can be some distance from the tank.

drain water heat exchanger
Drain Water Heat Exchanger

When you shower, you are both using and dumping hot water simultaneously. The heat that is being wasted by dumping it down the drain can be recovered. A drain water heat exchanger recovers the waste heat from the used shower water and uses it to preheat the cold water that is feeding into your hot water tank.

A drain water heat exchanger is installed vertically in the main drain pipe leaving the house. The sewage goes down the inside copper pipe and the water feeding your hot water tank flows through the copper tubing that is wrapped around the large pipe.

Based on personal experience, I can confirm that the temperatures shown in the animated illustration on the manufacturer's web site are accurate.

Shorter but less efficient models are available for locations with insufficient room for the full length version.

There are several sizes available and they are made in Saskatchewan by WaterCycles.