Thermal panels are magical. These devices absorb the sun’s heat and, using a system of pumps, collect the heat in a reservoir to be utilized as needed by the home.
There are as many variants on the basic types of panel as there are manufacturers.
But for simplicity’s sake, we will discuss the basic types.
The two fundamental types of thermal collection devices are: flat panels and evacuated tube.
Flat-panel thermal collectors use large, thin copper or copper-bronze plates to absorb the suns radiation and transmit the heat into a manifold of copper piping, or in some types, the piping is integrated into the battens, as the copper plates are known.
The glycol or water circulated through the collector, transfers the heat to the storage tank.
The entire arrangement of battens and piping manifold is encased in its own frame, insulated on the back, and covered on the top with a polycarbonate or glass covering, to allow maximum transmission of light while minimizing thermal losses.
Flat panels are generally recommended to be used in what is known as a drain back system which uses solar powered pumps to lift water to the collector during the day when sunlight is available.
The circulating water picks up the heat from the sun and delivers it back to the storage tank where it can be utilized by the home for hot water heat or space heating.
At the end of the daylight, the water pumps shut down and the water drains back into its storage tank.
The chief advantage is reduced cost due to eliminating the use of glycol.
Evacuated tubes use glass cylinders to absorb the sun’s radiation.
Being that each tube is actually two concentric tubes sealed together, the outside surface of inner glass tube is coated with layers of aluminum-nitrogen within an aluminum base.
This layer absorbs and converts the maximum amount of solar radiation (including infrared light) into heat, whilst having very minute radiation losses.
The space between outer and inner glass tubes contains a vacuum, which insulates the tube, allowing sunlight to penetrate while preventing heat loss.
Evacuated tubes are available in two models.
The first is a straight-forward evacuated tube in which a controlled circulation of glycol is pumped through the collector manifold.
The advantage to this collector is a lower price.
But it is not as efficient as the heat pipe evacuated tube manifold and cannot be used in pressurized systems.
It is suitable for heating swimming pools, as an example.
The heat pipe evacuated tube thermal manifold is designed for higher efficiency, uses less glycol than the simple low-pressure evacuated tube, produces more heat and is designed to be used in pressurized under-floor systems.
No matter what the need, there is a thermal panel available to meet it.
They provide a good supplement to your water or space heating needs with BTU outputs in the 50,000 BTU per panel per day range.
Not bad for a little sunshine.
Lorne Oja is an energy consultant, power engineer and a partner in a company that installs solar panels, wind turbines and energy control products in Central Alberta. He built his first off-grid home in 2003 and is in the planning stage for his second. His column appears every second Friday in the Advocate. Contact him at: lorne@solartechnical.ca