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The m.k.s. unit of energy is Joule. Joule: When a body moves through a distance of 1 m under the force of 1 N in the direction of force, then work done by the body is said to be 1J. Different forms of energy: (i) Kinetic energy: The energy possessed by a body due to its motion is called kinetic energy. i.e. KE = ½ mv 2. Here m is mass and
Energy Systems Analysis Arnulf Grubler Definitions & IS Units • Energy: Capacity to do work • Power: Rate of energy transfer • Newton (N): 1 kg m/s2 (force) • Joule (J): 1 N applied over 1 m (energy) • Watt (W): 1 J/second (power) • Example: 1 HP = 745 W (745 J/s) for 1 hr = 0.745 kWh
An energy transfer of 1 joule per second is equal to a power of 1 watt. If given two motors A and B, the motor that can do the same work faster is more powerful – as the energy is transferred at a faster rate
Describe key physical and engineering concepts for energy systems including the notions of energy and power and the fundamental laws of thermodynamics. Discuss key societal aspects of energy use and current challenges. Describe the elements of the energy transformation chain and use energy balances.
A consequence of the First Law is that in energy conversion processes involving heat to work conversion (or work to heat conversion) no more work (or heat) may be produced than 1 N. m/joule (or 1 joule/N.m).
Basic Energy Units. Joule (J) = Newton meter. calorie (cal)= 4.18 J = energy required to raise the temperature of 1 gram of water by 1 C. Btu = 1055 Joules = 778 ft-lb = 252 calories = energy required to raise the temperature 1 lb of water by 1 F. ft-lb = 1.356 Joules = 0.33 calories.
In a Joule expansion, a gas expands irreversibly from a volume V1 into a volume V2 (initially a vacuum), so that the total volume of the gas after expansion is V1 +V2. The system is thermally isolated and no external work is done on the gas, so ∆U = 0. The entropy change in a Joule expansion is (for 1 mole), ∆Sgas = Rln (V 1 +V2 V1): ATB ...
