Goal: Turn solar radiation into hot water
Active systems: Sun—>solar panel—>pump—>tank—> users
Passive systems: Sun —>solar panel/tank —> users (no pump needed, uses convection)
HPA systems are of two types:
Carter dorm has the active system, while Perry-Fiske and cafeteria have passive Solahart systems
Propane is used to finish these systems, making sure that users always have hot water at about 120°F. These are propane "flash" heaters, making sure that any water going to the showers/sinks/washers is always at 130°F. You can see these behind each bathroom if you are curious.
Hot water is stored in tanks, with about 10-15 kWh energy in each Solahart tank. Each Solahart system costs about $6K installed (panel and tank). To store 10 kWh using batteries would cost $13,000.
Solar thermal panels are about 90% efficient at converting solar radiation into hot water. PV panels are about 15% efficient in converting solar radiation into electrical energy.
Propane is competitive with electrical energy at about $0.25-$0.35 per kWh equivalent in our hot water heaters.
Walkthrough: Bring along FLIR camera
4x10' panel: note size, materials, if sunny hot water flow
Anna's: passive, note propane flash heaters, thermosiphon
Carter: active, note large storage tanks, pumps, sensors, insulation
Cottage 5 (if possible): note insulation, check with FLIR