Solar thermal systems use the sun’s energy to heat water for home use or space heating. These systems make the most efficient use of the sun’s energy – approaching 80% efficient – compared to PV’s (solar panels) 15% system efficiency. On top of that, these systems are much less expensive when measured by BTU (British thermal unit, a measure of power) delivered and can have a pay back period of less that 5 years.
A domestic hot water system can be coupled with an existing electric hot water heater or built from scratch. The basic system:
- Thermal collector panels can be mounted on your roof or elsewhere on a structure.
- Plumbing to connect the collectors to a storage tank.
- The storage tank will be sized based on the end usage of the hot water – domestic hot water will require a smaller tank size than space heating in general.
Different system styles will also require various pumps and controls based on the type of system designed.
We prefer to design domestic hot water systems or space heating systems that are either a closed loop glycol or drainback system, depending on the site layout and amount of heat needed.
The closed loop glycol system has a pressurized closed loop between the collectors and tank heat exchanger. A directly PV powered pump or AC powered pump circulates a glycol solution (an organic compound in the alcohol family which won’t freeze) to deliver heat from the collectors to the storage tank via an integral or external heat exchanger.
With a drainback system the collectors must be above the storage tank so that they can drain back into the storage tank once the circulation pump shuts off. These systems rely on gravity – which is pretty reliable — to drain the collector fluid from the collectors so they won’t freeze. These systems can use one or two pumps to deliver heat from the collectors to the storage tanks via an internal or external heat exchanger. Most large and space heating applications will be designed using this type of system.
Depending on your current fuel source for hot water or space heating these systems can quickly pay for themselves and deliver a large portion of your heating needs for free – years into the future.