Solar thermal panels: A trend begins

Millions of businesses and homeowners use solar panels to generate the electricity they need. Most use solar electric (photovoltaic) panels as a simple, cost effective source of renewable energy. However, electric paneling systems were not the first generation of solar energy solutions. Solar thermal panels helped to popularize the generation of electricity from the sun. While not nearly as widespread as electric panels, thermal panels can still be found in many homes and buildings. Below, you'll learn how solar thermal panels work, the difference between passive and active systems and how flatbed and evacuated tubes are involved.

How solar thermal panels work

The old method of absorbing energy and generating heat from sunlight required the use of copper pipes. The pipes used material that could collect and absorb the heat directly from the sun. In doing so, the absorbed solar energy could be used to warm a water supply. A simple example of this concept is a garden hose. If left in the sun, the water that initially comes from the hose is warm. This same concept is the foundation upon which solar thermal panels work. The old methodology of using copper pipes that could absorb heat was employed throughout homes to warm the water used for cooking, bathing, washing clothes and even to heat swimming pools. Today, copper pipes have largely been replaced with more efficient models of heat absorption.

Passive and active systems

When a solar thermal paneling system is called "passive" or "active," the terminology refers to whether the water is heated by deploying pumps and other moving parts or by the simple use of thermodynamics. The decision regarding which type of system to use is usually dependent upon climate and weather conditions. Specifically, in locations where temperatures plummet below freezing, active systems are used to heat water (often in conjunction with antifreeze). In areas that don't experience such harshly low temperatures, a passive system that relies upon a self-perpetuating circulation method is usually sufficient.

Flatbed vs. evacuated tubes

Most solar thermal panels come in two varieties: flatbed and evacuated tubes. Flatbed panels are designed with a sheet of metal that sits underneath glass. The glass is used to prevent the release of heat from the metal sheet. Flatbed systems are often inexpensive when compared to evacuated tubes. The primary drawback of using flatbed plates is that their conversion efficiency drops quickly when they're not exposed directly to sunlight.

Evacuated tubes use strips of metal (again, placed under a sheet of glass) within a vacuum. The objective of the vacuum is to control loss of conduction throughout the system. This type of solar thermal paneling is more efficient than flatbed plates during times when direct exposure to sunlight isn't possible.

Making room for solar electric panels

While many companies that manufacture solar thermal panels strive to make them more efficient, the trend is moving toward implementing solar electric panels. They're usually easier to install and maintain despite applying a more complex method of collecting energy and converting it to electricity. Also, the trend toward using solar energy facilitates the need for more flexible applications. For example, campers can use portable photovoltaic panels to generate heat and electricity. This would be all but impossible to do with flatbed plates or an evacuated tube system. While solar thermal panels are largely responsible for the widespread use of solar energy in homes and businesses, electric paneling systems have become a more popular solution.