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27 Cards in this Set
- Front
- Back
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What is the tilt angle of the earth?
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23.5 deg
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What does the term solstice mean?
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refers to the point at which hemisphere is tilted furthest away from (or closest to)the sun.
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What the the equinox and solstice dates?
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Autumn equinox - 21 Mar
Winter solstice - 22 Jun Spring equinox - 23 Sep Summer solstice - 21 Dec |
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At what orientation will the sun rise and set during the winter and summer solstice?
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winter solstice - sun rise north east, sun set north west.
Summer solstice - sun rise south east, sun rise south west. |
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Define latitude
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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).
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Define zenith, zenith angle and meridian.
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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. |
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On what two days of the years does the sun rise at due east and set at due west?
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Spring and autumn equinox.
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What does the phrase "Variation east, magnetic heading least; variation west, magnetic heading best" mean in navigational terms?
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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°
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Define Solar Irradiance, what is it's symbol and how is it measured?
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The rate at which solar radiation strikes a surface. Its symbol is G and it is measured in W/m sq.
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Define Solar Irradation, what is it's symbol and how is it measured?
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The solar energy that strikes a surface over a period of time. Its symbol is H and is measured in J/m sq.
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Thermal energy is measured in Joules. What is a joule equal to in terms of work done?
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1 joule is the required heat needed to raise 1 millilitre mL of water 1/4 deg Celsius.
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Explain the difference between heat and temperature.
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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.
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What is specific heat capacity? What is it's unit of measure?
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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).
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A watt is equat to 1000 joules per second. True/False
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False. 1 watt equals 1 J per sec.
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What are the three processes of heat flow? Explain each.
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Conduction, convection and radiation.
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Define Peak Sun Hours
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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. |
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What are the two components of global radiation?
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diffuse radiation and direct radiation.
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What data is available to determine the amount of solar radiation at a particular site?
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Tables of mean irradiation for each month.
Solar contour maps. Hourly irradiance charts. |
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What effect does latitude and season have on solar radiation?
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The greater the latitude the higher the seasonal variation due to the sun's lower angle.
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What is the incident angle?
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It is the angle from perpenicular to a panel and the angle of the sun's direct rays.
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What is the name of the measurement of how well a substance conducts heat?
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thermal conductivity measured in W/m.K (watts per meter kelvin)
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What do the letters G and R stand for and what are they are a measure of?
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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. |
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Describe the heat transfer coefficient, when it is applicable and its value.
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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
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What is thermal insulation coefficient?
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R-value.
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What is the R value of rockwool per 25mm
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.5
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What is thermal flux?
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The rate of transfer or heat.
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How many watts per horse power?
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736W
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