On Site Solar Hot Water on Haeger Ave, Arcata Presentation by Alan Cook

Solar hot water systems are also referred to as solar thermal heating systems. In a thermal heating system water runs through the panel in a closed loop to gather heat from the solar collector. The cold water is pumped from the bottom of the storage tank when there is a 16 degree difference between the tank and the solar collector. Heat is gathered from the collector and brought back down to the storage tank.

Due to expansion of water when frozen the solar collector cannot have water in freezing temperatures. Freezing temps are only in the morning at this location so draining the system when not in use would resolve the issue. At this site the system uses drain-back gravity feed unit which holds the water at the end of the day. Solar collectors are susceptible to extreme temperatures. Alan believes wind drag can be reduced by flush mounting the panels to the roof. Estimated use of hot water is approximately 20 gallons per person per day. It would take about 6-7 years (depending on use) to payback the cost of the system.

System overview:

  • 2 4x6.5ft flat solar collectors
  • 80 gallon water storage container (converted water heater)

Power offset:

  • 70-80% of their water heating is covered


  • $9,500 installed


  • no info given
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