Most effective us of active solar systems currently is to heat water for use in place of domestic hot water.
Several systems: Either a type of open or closed loop system
Flat plate collector system
Tubes either have flat fins or attached to large metal collector surface.
Surface = insulated heavily on back and sides with cover plate
cover plate = typically high transmissivity glass or plastic on the front
Focusing collector system
parabolic trough with interior surface of reflective aluminzed mylar
tube = clear or black running through focal line of the trough.
clear tubes = size of fluorescent tube filled with colored collector fluid
black tubes = copper or steel pipe, water running through them
Fresnel lense = Same curvature with steps in lense, controls focal point without having to use a thick lense
E.G. = A car headlight
Open Loop system = Means that fluid going through the loop is the fluid that will be consumed.
EG. water used for cooking or washing
Closed loop system = One fluid medium in the collector and connected piping runs through a water storage tank warming the water without being mixed with it.
Antifreeze is usually used in the collector.
Doesn't freeze in collector overnight like water can.
Drain back or drain down system = Empties the collector when temp. drops too low.
Senses temp. differential, opens valves, gravity drains fluid into a reservoir.
Failsafe, collector only full while operating.
Pump shuts off, everything drains back
Pump only turns on when temp. in collector is higher than storage
Batch system = a storage tank exposed to sun, often encased in an insulating box with a glass face.
Also called "breadbox"
Thermosiphon system = Storage tank higher than the collector and adjacent to it.
Water circulates by convection instead of pumping.
Warm water rises, cold water siphoned from base of tank to collector for warming.
If tank outside, must be well insulated
time: 0.5 6:45-7:15pm 6/16/09
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