SIMPLE Active solar systems

The simplest solar water heating systems do not use pumps (batch and thermosyphon design...); they rely on the use of gravity and water instead of pressure mechanisms and antifreezing fluids. But using pumps and glycol or other antifreezing fluids add versatility to a solar powered system, and it is their use that characterizes the so-called active solar designs.

Typical active solar systems have a small and cheap circulator pump (many with just 10 watts). Small thermostatically controlled pumps - often powered by a photovoltaic module - are very common.

The advantage of adding a pump

Adding a pump to a solar system opens a new possibilities. With a pump, the solar panels and the tanks have not to be located on the roof, and common problems associated with extreme temperatures (risk of freezing pipes, or damages caused by excessively high temperatures) can be overcome in a easier way.

Elements of Active solar Water Heaters

Simpler solar active designs are also technically called open systems due to the fact that they use water instead of glycol or other non-freezing fluid at the collector level.

Besides the solar panels, the storage tank and the pump, active solar systems also incorporate an electric tank and a set of valves, controllers and sensors to link the whole system.

Collectors & Active Solar Systems

Flat solar panels are largely used in the simplest active solar heaters, due to their lower prices; tube solar panels are preferable for more demanding applications, in colder climates.

The electric tank

Standard 50-gallon/200-litter electric tanks are common in active solar water heater systems. But since electric components are rarely hooked up, the tank is often used as a storage tank, feeding an existing backup gas/electric water heater.

Other elements

Active solar water heaters comprise elements like air vents at the higher point of the solar panel in order to purge air, and standard sensors to control the temperature in the tank.

The image on left (EERE) includes the components of a closed-loop water heater system. The difference between this system and the active solar system described in this page, resides on the fact that active solar water heaters use water at the collector level instead of a freezing fluid used in closed loop systems.