3.2 The Concept of Energy
49
the zero-phase angle, it can be derived 4 that the arithmetic mean of the current
power
−
p represents the effective power P e f f [He+2018, p. 73]:
P e f f =
−
p =
1
T
T
0
u × i dt
(3.15)
The measurement of the electricity consumption of the production machines
is in fact the measurement of the effective power.
The explanation of the terms apparent power and reactive power is omitted
as these are not considered in the course of the work. The interested reader is
referred to [HMW2012, pp. G25–G27].
3.2.2 Energy Efficiency
As already stated in the previous section (equation 3.8) efficiency can be defined
as the ratio of an output to the necessary input of a system. Transferred to the
energy industry understanding, energy efficiency in production means keeping
the energy used to produce goods as low as possible.
“An exergy analysis (second law of thermodynamics) reveals that the overall
global industry efficiency is only 30%” [Jo+2012, p. 516]. The more efficient final
energy is used, the more it reduces the amount of primary energy required.
Energy efficiency in manufacturing systems can be divided into several different levels, starting with the process level efficiency (Figure 3.7). The process
level efficiency considers energy losses by the physical mechanisms that are involved in the process itself. On the next higher level, the machine efficiency level, the
energy use of the machine for the process itself as well as for peripheral aspects
of the process are being looked at. “Finally, one has to consider the production
line level and the entire factory level, where energy efficiency is mainly a function
of production planning” [Fy+2013, p. 629]. As the percentage of energy spent on
the process itself is very small compared to the share spent on machine level to
perform processes, for coolant pumps or lubrication supply, the optimization of
the process level energy use will not be the main focus of this book.
4 A detailed derivation is not provided here. The interested reader is referred to the detailed
descriptions in the literature, especially in Hering et. al [He+2018, pp. 68–74], Hering,
Gutekunst and Martin [HGM2013, pp. 52–57] and Niedrig and Sternberg [NS2012,
pp. B166–B170].
49
the zero-phase angle, it can be derived 4 that the arithmetic mean of the current
power
−
p represents the effective power P e f f [He+2018, p. 73]:
P e f f =
−
p =
1
T
T
0
u × i dt
(3.15)
The measurement of the electricity consumption of the production machines
is in fact the measurement of the effective power.
The explanation of the terms apparent power and reactive power is omitted
as these are not considered in the course of the work. The interested reader is
referred to [HMW2012, pp. G25–G27].
3.2.2 Energy Efficiency
As already stated in the previous section (equation 3.8) efficiency can be defined
as the ratio of an output to the necessary input of a system. Transferred to the
energy industry understanding, energy efficiency in production means keeping
the energy used to produce goods as low as possible.
“An exergy analysis (second law of thermodynamics) reveals that the overall
global industry efficiency is only 30%” [Jo+2012, p. 516]. The more efficient final
energy is used, the more it reduces the amount of primary energy required.
Energy efficiency in manufacturing systems can be divided into several different levels, starting with the process level efficiency (Figure 3.7). The process
level efficiency considers energy losses by the physical mechanisms that are involved in the process itself. On the next higher level, the machine efficiency level, the
energy use of the machine for the process itself as well as for peripheral aspects
of the process are being looked at. “Finally, one has to consider the production
line level and the entire factory level, where energy efficiency is mainly a function
of production planning” [Fy+2013, p. 629]. As the percentage of energy spent on
the process itself is very small compared to the share spent on machine level to
perform processes, for coolant pumps or lubrication supply, the optimization of
the process level energy use will not be the main focus of this book.
4 A detailed derivation is not provided here. The interested reader is referred to the detailed
descriptions in the literature, especially in Hering et. al [He+2018, pp. 68–74], Hering,
Gutekunst and Martin [HGM2013, pp. 52–57] and Niedrig and Sternberg [NS2012,
pp. B166–B170].