Solar Heating
radiant floor (also "warm-floor" heating):

Since this type of heating is most compatible with the use of flat-plate solar collectors due to the design temperatures, several approaches have been developed to marry them. A major factor in the design is the architect or homeowner’s decision to use mass floors, such as cement, stone, or brick rather than non-mass floors such as wood.

1. Solar-Direct Injection

This, the simplest solar-heated radiant floor design, simply creates a closed loop between the floor tubing and the collectors. This approach works well with a well-insulated mass floor in a sunny climate, or when heating is only needed during the day. It is also used for snow-melt systems.

In such a system, fluid is pumped whenever the sun is shining, circulating through the collectors and the floors. Heat is picked up by the fluid in the collector, and deposited in the floor. A tempering valve is used to regulate fluid temperature in the floor, mixing supply and return fluids together as needed. This system does not use a storage tank, but relies only on the mass of the floor to radiate heat through the night.

2. Primary-Loop Injection and Distribution

This is most common type of solar heating system supplied by Cedar Mountain Solar. It allows for controlled incorporation of multiple heating sources, including solar, boiler, geothermal heat pump, etc. with multiple heating loads including warm floors or baseboards, pools and spas, and domestic hot water.

In a primary loop system, a loop of copper is installed, typically in a mechanical room. This copper loop has a dedicated pump constantly circulating fluid. The loop has inputs and outputs connected to heat sources and heating loads respectively. The solar collectors feed heat into this loop, as does the boiler or any other heat maker. Similarly, the different heating loads draw heat from this loop. These can include warm floors, baseboards, domestic hot water, pools and spas, and water storage tanks. The system is controlled to prioritize the use of solar heat when available, and can also be controlled to prioritize some heating loads over others and to dump excess heat as needed.

There are several advantages to installing systems in such a configuration. The loop provides an obvious place for all control sensors to get information. The flow rate through the loop is also regulated, whereas the flow rates through solar collectors, boiler, heat exchangers, etc. may vary widely depending on application, friction loss, and other factors. Similarly, the heating loads and sources all operate at different temperatures; water heaters at 140, boilers at 180, and collectors at 120 degrees F, for example. The loop mitigates the effects of these differences. A primary loop basically provides the system designer and installer with a means of organizing the system for greatest effectiveness.

3. Solar Pre-heat Systems

In a solar preheating system, solar collectors can be used to heat fluid, which then passes directly or indirectly through a boiler or other heat source. The fuel consumption of the boiler is therefore reduced, as less fuel is required to raise fluid temperature by 40 degrees than by 120 degrees.

Controls for these systems must be handled with care, to ensure that the potential benefits of pre-heating are realized.