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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 ...
Likewise, a similar home in Miami, Florida, whose heating degree days for the heating season is 500, would require around one tenth of the energy required to heat the house in New York City. [7] However, this is a theoretical approach as the level of insulation of a building affects the demand for heating. For example, temperatures often drop ...
A typical coal-fired power plant works at 10,500 Btu/kWh (3.1 kWh/kWh), an efficiency of 32–33%. [25] The centigrade heat unit (CHU) is the amount of heat required to raise the temperature of one pound (0.45 kg) of water by one Celsius degree. It is equal to 1.8 Btu or 1,899 joules. [26]
The ratings are based on EPA's formula, in which 33.7 kilowatt hours of electricity is equivalent to one gallon of gasoline (giving a heating value of 115,010 BTU/US gal), and the energy consumption of each vehicle during EPA's five standard drive cycle tests simulating varying driving conditions.
For example, a 5 kW home fuel cell produces about 80 MWh of annual combined electricity and heat, compared to approximately 10MWh generated by a 5 kW solar system. However, these systems are not directly comparable because solar power is a renewable resource with basically no operating cost, while natural gas is neither.
So, for a boiler that produces 210 kW (or 700,000 BTU/h) output for each 300 kW (or 1,000,000 BTU/h) heat-equivalent input, its thermal efficiency is 210/300 = 0.70, or 70%. This means that 30% of the energy is lost to the environment. An electric resistance heater has a thermal efficiency close to 100%. [8]
The building balance point temperature is the outdoor air temperature when the heat gains of the building are equal to the heat losses. [1] Internal heat sources due to electric lighting, mechanical equipment, body heat, and solar radiation may offset the need for additional heating although the outdoor temperature may be below the thermostat set-point temperature.
≳100000 [88] in practice, phonon scattering at solid-liquid interface is main barrier to heat transfer. 2.2 Liquid helium in its superfluid state below 2.2 K House: American 2016 Wood Product Blow-in, Attic Insulation 0.0440 − 0.0448 [89] FIBERGLAS Blow-in, Attic Insulation 0.0474 − 0.0531 [90] PINK FIBERGLAS Flexible Insulation 0.0336 ...