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A kilowatt-hour (unit symbol: kW⋅h or kW h; commonly written as kWh) is a non-SI unit of energy equal to 3.6 megajoules (MJ) in SI units, which is the energy delivered by one kilowatt of power for one hour. Kilowatt-hours are a common billing unit for electrical energy supplied by electric utilities.
As total energy consumption is in kilowatt hours and heating degree days are [no. days×degrees] we must convert watts per kelvin into kilowatt hours per degree per day by dividing by 1000 (to convert watts to kilowatts), and multiplying by 24 hours in a day (1 kW = 1 kW⋅h/h). Since a 1 °C temperature change and a 1 K change in absolute ...
The SI unit of irradiance is watts per square metre (W/m 2 = Wm −2). The unit of insolation often used in the solar power industry is kilowatt hours per square metre (kWh/m 2). [11] The langley is an alternative unit of insolation. One langley is one thermochemical calorie per square centimetre or 41,840 J/m 2. [12]
The therm (symbol, thm) is a non-SI unit of heat energy equal to 100,000 British thermal units (BTU), [1] and approximately 105 megajoules, 29.3 kilowatt-hours, 25,200 kilocalories and 25.2 thermies. One therm is the energy content of approximately 100 cubic feet (2.83 cubic metres) of natural gas at standard temperature and pressure. However ...
Power is the rate at which energy is generated or consumed and hence is measured in units (e.g. watts) that represent energy per unit time. For example, when a light bulb with a power rating of 100 W is turned on for one hour, the energy used is 100 watt hours (W·h), 0.1 kilowatt hour, or 360 kJ. This same amount of energy would light a 40 ...
units: 1 horsepower [21] 7.5 × 10 2: astro: approximately the amount of sunlight falling on a square metre of the Earth's surface at noon on a clear day in March for northern temperate latitudes: 9.09 × 10 2: biomed: peak output power of a healthy human (non-athlete) during a 30-second cycle sprint at 30.1 degree Celsius. [22]
The actual direct solar irradiance at the top of the atmosphere fluctuates by about 6.9% during a year (from 1.412 kW/m 2 in early January to 1.321 kW/m 2 in early July) due to the Earth's varying distance from the Sun, and typically by much less than 0.1% from day to day.
The langley (Ly) is a unit of heat transmission, especially used to express the rate of solar radiation (or insolation) received by the earth. The unit was proposed by Franz Linke in 1942 [ 1 ] and named after Samuel Langley (1834–1906) in 1947.