Quick Answer
Solar thermal systems can be used during cloudy days for heating, but the efficiency may be reduced. This is because solar thermal systems rely on direct sunlight to heat water or a fluid, which then provides heat for a hydronic radiant floor system. While some systems can store heat for later use, cloudy days can significantly reduce the amount of energy generated.
Solar Thermal System Components
A typical solar thermal system for a hydronic radiant floor system consists of a solar collector, a heat exchanger, a storage tank, and a circulating pump. The solar collector is usually a flat plate or evacuated tube system that absorbs sunlight and converts it into heat. The heat exchanger transfers this heat to a fluid, which is then pumped to a storage tank for later use.
System Design Considerations
When designing a solar thermal system for a hydronic radiant floor system, it’s essential to consider the storage tank capacity. A general rule of thumb is to size the storage tank to provide at least 2-3 days of heat in the event of cloudy weather. For example, if the radiant floor system requires 10,000 BTUs of heat per day, the storage tank should be sized to hold at least 20,000 to 30,000 BTUs of heat.
System Performance During Cloudy Days
While solar thermal systems can be used during cloudy days, their performance will be reduced. On a cloudy day, the system may only produce 20-30% of its peak performance. To compensate for this reduced performance, the system designer should consider increasing the size of the solar collector or the storage tank to ensure that the radiant floor system receives the required amount of heat.
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