πΈπΈπΈπΈπΈπΈπΈπΈπΈπΈπΈπΈ (ππππβ) = β« π΄π΄π΄π΄π΄π΄π΄π΄πΈπΈπ΄π΄ π΄π΄ππ πΈπΈπΈπΈπΈπΈπΈπΈπΈπΈπΈπΈ πππΈπΈπ΄π΄πππ΄π΄πππΈπΈπππ‘π‘0π‘π‘π‘π‘ (ππππβππ) (1) The legend is as follows:
β’ kWh is the amount of energy generated from the system
β’ t0 and tx are referring to the duration time of the cycle
β’ kWh-e is the energy generated by the system
kWh is estimated to be produced for alternating current for a month. From the statement and observation in the simulation, the amount produced by the trains could be able to generate the energy required by the area i.e. stationary equipment, stations and traction auxiliary supply system. The scenario of the study is notable different where the Traction Power Supply System is located far away in some of the cases.
This also noted that the result from the simulation is an indicator for the energy storage system to be implemented at the location where the traction power system is located. In certain locations, the Traction Power Supply system is isolated from the stations where the station load of the system is much larger. In this case, the scenario considers at the location of Traction Power Supply System location either the location is located near to stations or far away from the stations.
4.5.1 Design of Energy storage system
It is observed that in the modelling of the railway power supply and distribution system, the energy produced during the operation on non-regenerative and regenerative braking observed that the energy that able to be retrieved from the system amount at 42.1 kWh. The required capacity of the Energy Storage System (ESS) is calculated as the formula :
P = E/t (4.4) where
P = power, kW E = energy, kWh t = time, s
From the modelling of the railway and graphical in figure 3.5, the maximum duration time for the regenerative braking is up to 30 seconds. Based on the literature review, current implementation of the Energy Storage System (ESS) and the outcome from the result, the supercar technology is chosen to store the regen. The supercapacitors are chosen based on this benefit (a) Capability of charging and discharging time with balancing energy storage, (b) its capability
to charge in a short duration of time and (c) wide-ranging in operating temperature (-40F to 150F). From the equation at 3.3, the capacity of the Energy Storage System is
P = E/t ο¨ P = 42.1 kW(3600)/30 = 5,052 kW.
With the safety factor to be considered in the design, 1.25 safety factor shall be considered to govern the worst condition scenario. The final capacity of the Energy Storage System is
P = E/t ο¨ P = 42.1 kW(3600)/30 = 5,052 kW x 1.25 = 6,315 kW
In consideration of the capacity, it is noted that the capacity of the Energy Storage System is estimated at 6,315 kW. The power conditioning for the system shall be designed to accommodate the size of the Energy Storage System. With the current design, a redundancy power supply system in the train and consideration in the train power system design shall consider this requirement.
Other factors also shall be considered in the design i.e. temperature, power losses due to cable resistance, power conditioning losses. The design of the power conditioning is as per the modelling graph in Figure 4.10. It is observed that the cumulative power during regenerative braking contributes a large amount of energy compared to non-regenerative braking. From Figure 4.10 (b), the maximum power captured during the regenerative braking is 2960 kW. The requirement of the power conditioning shall be rated at modelling capacity. It is also noted that the safety factor shall be considered to accommodate the fluctuation in the electronic component and other factors i.e., power losses, harmonic loss. The final capacity of the power conditioning is
P = E/t ο¨ P = 2960 kW = 2960 kW x 1.25 = 3700 kW
(a)
(b)
Figure 4.10 Commutative power by trains during operation (a) all trains (b) 6 minutes duration by the trains
From the result above, the Energy Storage System and Power Conditioning design as Table 4.2
No Energy Storage System Capacity
1. Supercapacitors Bank 6315 kW
2. Power Conditioning (Inverter/Converter) 3700kW Table 4.2 Summary of the Energy Storage System
-4000 -3000 -2000 -1000 0 1000 2000 3000 4000 5000
6:00:00 AM 6:00:59 AM 6:01:58 AM 6:02:57 AM 6:03:56 AM 6:04:55 AM 6:05:54 AM 6:06:53 AM 6:07:52 AM 6:08:51 AM 6:09:50 AM 6:10:49 AM 6:11:48 AM 6:12:47 AM 6:13:46 AM 6:14:45 AM 6:15:44 AM 6:16:43 AM 6:17:42 AM 6:18:41 AM 6:19:40 AM 6:20:39 AM 6:21:38 AM 6:22:37 AM 6:23:36 AM 6:24:35 AM 6:25:34 AM 6:26:33 AM
Power (kW)
WO Regen W Regen
-4000 -3000 -2000 -1000 0 1000 2000 3000 4000 5000
6:00:00 AM 6:00:15 AM 6:00:30 AM 6:00:45 AM 6:01:00 AM 6:01:15 AM 6:01:30 AM 6:01:45 AM 6:02:00 AM 6:02:15 AM 6:02:30 AM 6:02:45 AM 6:03:00 AM 6:03:15 AM 6:03:30 AM 6:03:45 AM 6:04:00 AM 6:04:15 AM 6:04:30 AM 6:04:45 AM 6:05:00 AM 6:05:15 AM 6:05:30 AM 6:05:45 AM 6:06:00 AM 6:06:15 AM 6:06:30 AM
Power (kW)
WO Regen W Regen
CHAPTER 5
CONCLUSION AND RECOMMENDATION 5.1 Conclusion
This chapter sets out the outcome from the studies and the information shall be concluded and explained according to the result achieved from the exercise. The outcome context of the research is important to the nature of the field of study.
The nature of the analysis, the significance of the study and the design of the research structure will be concluded and future exploring the information which incorporated the other factor recommended by other researchers and authors.
The focus of the studies to overview the 3 objectives is as follow
a. To investigate the characteristics of energy generated from the regenerative braking
The characters of the system had been evaluated based on the simulation and the result from the simulation had been recorded and captured in section 4.
The energy produced and could be harvested from the system has been estimated at approximately 42.1 kWh. The amount of the energy had been explained based on the finding by the author for future reference and studies.
b. To design an energy storage system to recover the energy from the regenerative braking
From the studies, the energy from the regenerative braking was observed to be estimated at 42.1 kWh. The amount of the energy is been explained in Figure 25.1 which had shown the amount of energy that could be harvested and reused by the local supply requirement i.e., stations, ancillary building and traction power supply system. The energy harvested from the train operation is considerable large and able to feed to the vital equipment in event of any power failure in the railway system. It is noted that the design is also covered by the Uninterruptable Power Supply (UPS) were to cover the essential and critical components in the system. The result from the studies shows that the energy generated by the train operation is a value-
added to the design implementation and recommendations on the energy storage system shall be widely integrated into the power system design study.
c. To evaluate the performance of the system developed
The energy produced by the model is largely able to power up the essential and critical supply without relying on exporting the energy from the grid power supply. It is also noted that the grid power supply is important to initialize the power for the railway operation but the renewable energy implementation i.e., the energy storage system is one of the options to reduce the current focus by all countries to reduce global warming and toward the green environment. As mentioned in previous chapters, it is supplementary to using the battery type for two (2) main purposes either Compensation Voltage Sagging or Fixed Energy Storage System.
The aim of the studies is covered by the achieved 3 objectives and could be addressed other detail requirement by recommended by other authors i.e., operation strategy. The commitment to reusing renewable energy is part of the world commitment to preserving nature and renewable energy could also reduce the dependency on fossil raw materials.