Collectors’ efficiency
Flat
A part of solar radiation reaching the collectors is “lost” as a result of
reflection and absorption. Optical efficiency takes into accout this loss.
During the process of collectors’ heating up the heat is given back to the
surroundings through the process of heat conduction, heat radiation and
convection.
Tubular-vacuum
If the difference of the collector’s temperature and the temperatue outsie is
zero than the collector does not have any heat loss outside and its maximum
efficiency is reached. Than we can talk about optical efficiency.
The degree of covering the demand for energy by solar systems
The degree of covering the demand for energy by solar systems
 Flat
collectors
The degree of covering the demand for energy by solar systems gives the
proportional annual contribution of energy provided by them in comparison to the
amount of energy needed for usable water heating. The area of an absorber should
be adjusted in a way that it would be possible to avoid the production of
excessive amounts of energy during summer. When the degree of covering the
demands of solar system is high then the efficiency is lower because the high
degree of covering the demands raises the level of solar system’s temperature.
It causes the raise of heat loss of the entire system.
 Tubular-vacuum
collectors
The diagrams present the accessible levels of covering the demands by using
different types of collectors with reference to:
• Meteorological conditions of areas in Poland (around 1100 kWh/m2 x a),
• Roofs directed to the south,
• Roof’s slope at 45 degree
• Temperature of usable hot water (45oC) inside a heater
Given values are only approximate.
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