Flashcards in Solar Deck (28)
Heating Systems fall into two categories:
Active system: which use a pump to control water
Passive system: which use no pump
Potable water circulates and thus the heat collecting fluid is the same potable water that is in water heater
the fluid that circulates through the collector may be domestic water or another heat transfer fluid
Differential Controlled (AD)
The circulating pump operates when sensors located at the top of the collector and bottom of the storage tank reach a preset difference of 5 to 20F. Water circulates through the collector only when sufficient solar energy is available to increase the water temperature.
Photovoltaic Controlled (AD)
A PV module generates power for a DC pump that circulates water through the collector and back into the storage tank.
Timer Controlled (AD)
Used in tropical climates where temperatures are mild year-round. Timer turns on a pump in mid morning and switches it off in late afternoon.
Flat Plate Collector
Designed to heat water to medium temperatures (140F). Contains: enclosure, glazing, glazing frame, insulation, absorber and flow tubes.
Smaller solar collecting surface because this surface must be encased by an evacuated glass tube. Deliver higher temperatures 300F.
Flooded Evacuated-tube Collector
The absorber (surface inside the vacuum tube) itself forms a tube through which the heat collection fluid is pumped. Used is passive thermosyphon systems.
Heat pipe evacuated-tube collector
A flat absorber plate running the length of the tube covers a heat pipe filled with a fluid that evaporates at relatively low temperatures.
ICS - Integral Collector Storage
Incorporate 4" or larger diameter horizontal metal tanks connected in series by piping from a water inlet at the bottom of the tank to an outlet at the top.
Usually is made of just one black-painted metal tank inside an insulated enclosure covered with some type of glazing.
Water storage tank is located above the collector. Cold water from the bottom of the thermosiphon system's tank flows through a pipe to the bottom of the solar collector.
A collector and its mounting structure need to be able to withstand intermittent wind loads up to _____ miles per hour which corresponds to a pressure of about ____pounds per foot.
Wind loads: 146 miles per hour
Pressure: 75 pounds per square foot
A ground mounted collector should be at least ____ foot above the ground.
Recommended flow rate through a collector?
1/2 gpm for each 40ft square-area of panel
For residential forced circulation systems, use a minimum of ____ ID pipe for total runs of 100 feet
When the flow requirement is greater than 1 gpm and the pump is less than 1/20hp use ____ pipe
For a thermosiphon system, use of ____ piping helps eliminate undesirable resistance to fluid flow.
If two or more collectors are to be connected in parallel, use ____ pipe for interconnections.
Use ____ thick rubber type insulation on all piping.
Install all piping with a continuous slop of ____ per foot toward the drains.
Low-temp sensor of the differential controller is placed:
Attach near the bottom of the storage tank
The high-temp sensor may be placed in one of the following three places:
1. On the outlet pipe of the solar collector
2. In the air space between the collector absorber and the transparent cover
3. Against the absorber surface
Water returning to the tank will be hotter than the water stratified at the the top of the tank. Therefore the returning water is placed about ____down the side of the tank.
When wiring the collector and freeze sensor, what wiring configuration allows it close or open?
Parallel: if the freeze sensor closes on temperature fall Series: if the freeze sensor opens on temperature fall
What is the typical voltage between the positive and negative terminals of the PV module?
Given almost any amount of sunlight, this open-circuit voltage should be between 14 and 22 volts.