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27 Cards in this Set

  • Front
  • Back
What is the tilt angle of the earth?
23.5 deg
What does the term solstice mean?
refers to the point at which hemisphere is tilted furthest away from (or closest to)the sun.
What the the equinox and solstice dates?
Autumn equinox - 21 Mar
Winter solstice - 22 Jun
Spring equinox - 23 Sep
Summer solstice - 21 Dec
At what orientation will the sun rise and set during the winter and summer solstice?
winter solstice - sun rise north east, sun set north west.
Summer solstice - sun rise south east, sun rise south west.
Define latitude
The angle between the equator and the required location (ie sun, satellite) from the centre of the earth. Nothern hemisphere angles are positive, southern hemisphere angles negative (by convention).
Define zenith, zenith angle and meridian.
Zenith: a point directly overhead.
Zenith angle: the angle between a vertical line and the direction of the sun's rays.
Meridian: a line drawn directly overhead from north, through zenith, to the south.
On what two days of the years does the sun rise at due east and set at due west?
Spring and autumn equinox.
What does the phrase "Variation east, magnetic heading least; variation west, magnetic heading best" mean in navigational terms?
If the local variation is 12° east, the magnetic heading will be the true course minus 12°, e.g. true course 010°, magnetic heading 358°. If the variation is 2° west the magnetic heading will be the true course plus 2°, e.g. true course 010°, magnetic heading 12°
Define Solar Irradiance, what is it's symbol and how is it measured?
The rate at which solar radiation strikes a surface. Its symbol is G and it is measured in W/m sq.
Define Solar Irradation, what is it's symbol and how is it measured?
The solar energy that strikes a surface over a period of time. Its symbol is H and is measured in J/m sq.
Thermal energy is measured in Joules. What is a joule equal to in terms of work done?
1 joule is the required heat needed to raise 1 millilitre mL of water 1/4 deg Celsius.
Explain the difference between heat and temperature.
Heat or heat energy is the amount of energy contained in an object while temperature is a measure of the level of heat. A bath and a cup of water may be at the same temperature but the bath tub will have much larger amount of heat energy.
What is specific heat capacity? What is it's unit of measure?
Is the amount of heat required to raise the temperature of one unit of mass of material by one unit of temperature. i.e. the heat required to raise the temperature of 1 kilogram of substance by 1 Kelvin. Different materials have a different specific heat capacity. It is measured in Joules per kilogram Kelvin (J/kg K).
A watt is equat to 1000 joules per second. True/False
False. 1 watt equals 1 J per sec.
What are the three processes of heat flow? Explain each.
Conduction, convection and radiation.
Define Peak Sun Hours
Units which often used in the4 design of solar PV systems. 1 PSH = 1 kWh/msq
PSH equates to the equivalent number of hours of midday sun on a clear day.
What are the two components of global radiation?
diffuse radiation and direct radiation.
What data is available to determine the amount of solar radiation at a particular site?
Tables of mean irradiation for each month.
Solar contour maps.
Hourly irradiance charts.
What effect does latitude and season have on solar radiation?
The greater the latitude the higher the seasonal variation due to the sun's lower angle.
What is the incident angle?
It is the angle from perpenicular to a panel and the angle of the sun's direct rays.
What is the name of the measurement of how well a substance conducts heat?
thermal conductivity measured in W/m.K (watts per meter kelvin)
What do the letters G and R stand for and what are they are a measure of?
G = thermal conductance which is the property of a substance with size and shape to transfer heat (W/K).
R = thermal resistance which is the reciprocal of thermal conductance. It is analogous to electrical resistance.
Describe the heat transfer coefficient, when it is applicable and its value.
Usually when dealing with containers whose walls have large area relative to thickness. Similar to thermal conductance but not related to area. U-value measured in W/msq K
What is thermal insulation coefficient?
What is the R value of rockwool per 25mm
What is thermal flux?
The rate of transfer or heat.
How many watts per horse power?