Harnessing the heat of the sun

Published Tuesday, June 9, 2015 in the New Brunswick Telegraph Journal and the Fredericton Daily Gleaner.

When talk turns to solar panels, most people immediately think of photovoltaic panels, the kind that produce electricity.  But there are other types of panels that are even more efficient at turning the sun’s rays into energy we can use to lower our bills and reduce our carbon footprint.  Here’s a quick overview of solar thermal energy. 

Rationale

As opposed to passive solar energy (which is using nothing more than logic and smart design to get free heat from the sun), solar thermal energy means using specialized panels to actively capture the sun’s rays and use their energy to heat air or water. 

Solar thermal panels make sense because hot air and hot water are the very forms of energy we most need and consume in our homes.  Home heating and hot water make up 80 per cent of the energy used in a typical home, and in New Brunswick that energy is usually electricity.  So every bit of heat or hot water produced by a solar thermal panel reduces our power bill and, by extension, greenhouse gas emissions.  

Solar hot air

Solar air heaters are simple and pay for themselves quickly.  There are two main kinds, glazed and perforated wall.

Glazed panels resemble large, dark windows.  They consist of a rectangular frame covered by a glass-like material, with a heat-absorbing material enclosed within.

They work on a very simple principle: sunlight enters through the glass-like cover, strikes the heat-absorbing material inside and heats the surrounding air.  A small fan then blows that heated air to where it’s wanted.

Popular glazed solar air heater brands include Solarsheat and CanSolAir (manufactured in Newfoundland).  Many backyard inventors have built their own panels; the internet abounds with functional DIY designs. 

Do solar air heaters work?  A supplier once told me the best testimonial he’d ever heard came from a lady who had installed one.  “I don’t know how they work,” she’d said.  “All I know is that, when the sun comes out, my furnace turns off.”

The second type of solar air heater is the perforated solar wall.  Solar walls are installed on the south side of buildings instead of usual exterior cladding.  They consist of a dark metallic material with many tiny perforations.  A fan draws air through the tiny holes into an airspace behind, warming the air in the process.  

Solar walls have become popular on commercial buildings in over 30 countries, and they are very effective.  The solar wall on Saint John Transit’s bus garage was installed in 2009 and has resulted in estimated annual savings of $10,000.

Another big advantage of solar air heaters: they last for decades and require virtually no maintenance.

Solar hot water

Among solar hot water systems, one application stands out for simplicity and rapid payback: pool heaters.  If you have a pool and don’t heat it with solar, you’re missing out on big savings.

Solar domestic hot water systems work very well too; Enerworks and ThermoDynamics are two Canadian manufacturers.  They are more expensive, require some maintenance and have longer paybacks, but I can attest to their effectiveness: our home has a ThermoDynamics system functioning in tandem with a conventional electric hot water heater.  In winter, the solar system takes the chill out water before feeding it into the electric tank for topping up, but from spring until early fall, the solar system produces more than enough blistering hot water for our family’s needs.

In the future, look for systems that use summer sunshine to heat water that is then stored to provide heat in winter; that’s already happening in some countries.

The sun never sends a bill.  So, whether through passive solar design, photovoltaic panels or solar thermal, it’s wise to take advantage of its free heat.