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Integrate Solar Thermal Energy

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INTEGRATE SOLAR THERMAL ENERGY

Solar thermal systems use the heat from the sun to heat water as opposed to solar photovoltaic (PV) which uses solar energy to energize a home. This system allows it to depend less on electric water heating and reduce costs. This strategy focuses on explaining how the system works, how to purchase it, and how to install it.

Strategy in Action

1. Identify Home Hot Water Needs

2. Choose the System

3. Install the System

4. Connect the System

WHAT YOU NEED TO KNOW

  • A solar thermal collector is a device that transfers radiation from the sun to heat water for household use. It is typically located on the roof and must have access to the plumbing system.
  • There are two types of solar thermal systems:
    • Thermosiphon: passive; does not require energy from the grid
    • Flat Plate: active; does require energy from the grid 
  • Water is pumped to the roof and then stored in a home water storage tank for household use.
  • Consult a structural or civil engineering to verify that the home’s roof can hold the weight.
  • Solar systems with higher solar energy factor (SEF) and solar fraction (SF) perform better.
  • Identify the system’s warranty with your contractor or vender to ensure you are protected should it fail due to possible defects.
  • Identify distance between the solar system on the roof and electric tank location.
  • When the system is installed, check that the hot water delivery temperature valve is correctly set and not exceeding 130 degrees Fahrenheit.

 

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STEP 1 - IDENTIFY HOUSEHOLD HOT WATER NEED
  • A family of four using 52 gallons of hot water (125 Fahrenheit) would consume about 5.2 kilowatt- hours (kWh) per day.
  • The appliances that are used for heating water (sinks, bathtubs, washing machines) determine how much hot water you will need. Using a flow meter is the most accurate way of identifying how much hot water you are using. in absence of a flow meter, collecting (weighing) a sample (timed in seconds) of hot water out of each faucet or shower is the most accurate way to identify how much water per person you are using.
  • The more water conservation practices you have in place, the smaller your appliance and the less water you will need to heat with your solar thermal system.

 

DISCLAIMER

  • The system and its components should be certified by an accredited testing institution following international code and standards.
  • Use a programmable 24-hour timer with battery backup clock to prevent the use of electric resistance heating. Program it according to your weekly occupancy. schedule.
STEP 2 - CHOOSE THE SYSTEM

THERMOSIPHON

 

  • Used by itself with integrated storage, connected, or added to an existing tank to backup electric storage water heater and increase hot water capacity.
  • Unlike an active system, the thermosiphon does not use an active pump.
  • A thermosiphon collector heats water within the collector where hot water rises by convection into the top of the storage tank. Cold water flows down from tank to the collector therefore establishing a slow, natural flow without the use of a pump.
  • Solar systems with higher solar energy factor (SEF) and solar fraction (SF) perform better. Look for an efficient system, with a SEF between 1.2 and 1.9 and a SF between 26% to 52% (.26 to .52).

 

 

 

 

 

 

 

 

 

FLAT PLATE

 

  • Utilizes hot water circulation pump to provide higher level of efficiency.
  • Utilizes a single larger storage tank (usually 50-120 gallons) depending on collector size or number of multiple collectors.
  • Alternating current (AC) pumps provide higher pumping capacity, compared to direct current (DC) ones.
  • Recommended for:
    • Homes with an integrated renewable energy system in place
    • Works for residential or commercial applications
    • When little power is needed for the pump to circulate water
  • Solar systems with higher solar energy factor (SEF) and solar fraction (SF) to perform better. Look for an efficient system, with a SEF between 2.0 and 4.5 and a SF between 50% to 75% (.50 to .75).

 

 

 

 

 

 

 

 

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THERMOSIPHON

SOLAR COLLECTOR

  • Consists of an insulation, absorber plate and flow tubes.
  • Absorbs the sun’s light energy and transfers heat to water via pumped fluid circulating through the collector tubes.
  • Can Use up to 3 collectors connected to a integrated 120 or 80 gallon tank size

INTEGRATED SOLAR STORAGE TANK

  • Stores heated potable water in a separate tank with backup electric resistance element.

DRAIN VALVE

  • Allows draining, filling, and servicing of the system.

ANTI-SCALD / MIXING VALVE

  • Tempers hot water from the solar storage tank with cold water to maintain an adequate temperature of the hot water delivered to its end use.

COLD WATER CUT-OFF VALVE

  • Isolates the system from incoming water supply.

 

FLAT PLATE

SOLAR COLLECTOR

  • Absorbs the sun’s light energy and transfers heat to water via pumped fluid circulating through the collector tubes.
  • Can Use up to 3 collectors connected to a integrated 120 or 80 gallon tank size

AUXILIARY/MAIN STORAGE TANK

  • Stores heated potable water as it circulates in a separate tank with backup electric resistance element.

SOLAR LOOP EXPANSION TANK

  • Allows for the expansion and contraction of heat transfer. Outdoor solar systems should be equipped with temperature and pressure relief valves. The expansion tank will absorb thermal expansion of hot water from the solar system and prevent hammer shock when opening fixtures.

SERVICE DRAIN VALVES

  • Pumps air out of circulation lines to allow proper water circulation.

ANTI-SCALD / MIXING VALVE

  • Tempers hot water from the solar storage tank with cold water to maintain an adequate temperature of the hot water delivered to its end use.

AIR VENT

  • Purges air from the collector.

DIFFERENTIAL CONTROLLER

  • Controls alternating current (AC) over a timer, sensing the temperature at the bottom of the tank and outlet of the collector. It activates the pump when temperature is prime and prevents activation in case of overheating, overuse, or when the home is empty (so no water is used).

SOLAR PUMP/CONTROLLER

  • Controls the operation of hot water circulation to the collector.water circulation.


       

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      STEP 3 - INSTALL THE SYSTEM
      • Install in accordance with local regulations and through a certified PV contractor as determined by Puerto Rico’s regulations.
      • Install a heavy-duty commercial grade 240VAC (30-amp) toggle switch that is easily accessible to cut-off power to the backup water heater. This is in addition to the existing 240VAC circuit panel breaker (20-amp for 120VAC small capacity water heaters).
      • Utilize a tank wrap to prevent heat loss from storage tank.
      • Install a mixing valve to prevent excessive hot water delivery to the use point. Note: most anti- scald mixing valves prevent hot water flow during pressure loss of city water mains; a thermostatic mixing valve is an alternative.

       

      ORIENTATION

      • The optimal angle for installation is usually pre-set by the rack support system supplied by the installer/manufacturer providing the optimum performance.
      • Collector should face south and be free of shading.
      • Incline 18 degrees, close to Puerto Rico’s latitude. On the thermosiphon system, an inclination of less than 8 degrees or more than 30 degrees is unacceptable.
      • Orient portrait facing south to reduce air bubbles.

      LOCATION

      • Place on a concrete slab, heavy- duty platform, or concrete roof.
      • Ensure roof can hold the load of the equipment. The system can be more than 800 pounds.
      • Proximity between tanks and equipment reduces piping losses.
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