Energy Load Curve
It is energy versus load plot of the cumulative integration of the area under the load curve starting from zero load to the particular load. It can be easily derived from the load duration curve. It is used to know the amount of energy at different demand levels. For each load interval, the area under the curve is calculated from “zero time” to time for which load interval is present. The area under the curve is calculated for a load interval is added to the previous total area to get energy for the present load. The curve always begins from energy of zero and increases with load. Let us consider the following load duration curve:
Area, A_{1} = 3 * 24 = 72 kWh
Area, A_{2} = 15 * 12 = 180 kWh
Area, A_{3} = 6 * 10 = 60 kWh
Area, A_{4} = 6 * 9 = 54 kWh
Area, A_{5} = 5 * 6 = 30 kWh
Now, Energy at different load:
At load of 0 kW, Amount of energy consumed = 0 kWh
At load of 3 kW, Amount of energy consumed = A_{1} = 72 kWh
At load of 18 kW, Amount of energy consumed = (A_{1} + A_{2}) = 252 kWh
At load of 24 kW, Amount of energy consumed = (A_{1} + A_{2} + A_{3}) = 312 kWh
At load of 30 kW, Amount of energy consumed = (A_{1} + A_{2} + A_{3}+ A_{4}) = 366 kWh
At load of 35 kW, Amount of energy consumed = (A_{1} + A_{2} + A_{3 }+ A_{4 }+ A_{5}) = 396 kWh
Figure: Energy load curve
Mass Curve
It is energy versus time plot of the cumulative integration of the area under the load curve starting from zero time to the particular time. A mass curve represents the total energy consumed by the load upto a particular time in a day. So, mass curve can be easily plotted from the chronological load curve by to summing up the energy consumed upto different times starting at the zero time. Let us consider the following load curve:
Figure: Load curve
Area, A_{1} = 2 * 18 = 36 kWh
Area, A_{2} = 6 * 35 = 210 kWh
Area, A_{3} = 1 * 24 = 24 kWh
Area, A_{4} = 3 * 30 = 90 kWh
Area, A_{5} = 12 * 3 = 36 kWh
Now, Energy at different load:
At time 6 AM, Amount of energy consumed = 0 kWh
At time 8 AM, Amount of energy consumed = A_{1} = 36 kWh
At time 2 PM, Amount of energy consumed = (A_{1} + A_{2}) = 246 kWh
At time 3 PM, Amount of energy consumed = (A_{1} + A_{2} + A_{3}) = 270 kWh
At time 6 PM, Amount of energy consumed = (A_{1} + A_{2} + A_{3}+ A_{4}) = 360 kWh
At time 6 AM, Amount of energy consumed = (A_{1} + A_{2} + A_{3 }+ A_{4 }+ A_{5}) = 396 kWh
Figure: Mass curve