Q2. What is the role of CNG in the transportation industry?
In view of the long way to large-scale adoption of electric vehicles, CNG is viewed as an appropriate transition fuel towards a greener transportation sector [14].
Q3. What are the main categories of energy efficiency of energy converting systems?
Energy efficiency of energy converting systems falls into four general categories of equipment efficiency, technology efficiency, performance efficiency and operation efficiency [32, 33, 34, 35].
Q4. What is the main reason why the compressor stays off during the morning peak?
Since the compressor stays off during the morning peak electricity pricing period, the compressor has to be switched on to satisfy gas demand for the standard electricity pricing period.
Q5. What is the main reason for the growth of CNG fuelling stations in Johannesburg?
Introduction of public service vehicles powered by CNG as well as growth in the number of CNG fleet customers has resulted in the growth in number of vehicle fuelling station in the city of Johannesburg and Pretoria.
Q6. What is the first method used in the optimization of water pumping systems?
The first method is the Pretoria method proposed by [73] and used subsequently in optimization of the performance of water pumping systems [63, 74].
Q7. What is the effect of motorists fuelling before travelling?
Increased late afternoon and evening fuelling activity is also as a result of motorists who fuel prior to travelling the next day.
Q8. What is the effect of the ambient temperature on the filling of the vehicle?
Using thermodynamic laws and mass balance, [44] studied the effects of initial conditions and ambient temperature on the filling of the vehicle on-board cylinder and achieving of the target pressure.
Q9. How can the optimization of the compressor be done?
This can be done by changing the algorithm on the existing programmable logic controller that operates the compressor so that it is time-scheduled according to the results of the optimization, instead of the pressure limit cycled operation employed by the existing system.
Q10. How many on/off switching instances does the compressor have?
Although this optimization regime minimizes the compressor action during the peak periods of electricity pricing thereby reducing electricity cost, the number of on/off switching of the compressor is too high at 14 and increases the probability of failure through fatigue to the compressor components which will results in an increase in maintenance cost [68, 81].
Q11. What is the common scenario for a vehicle to arrive with a high tank pressure?
It is possible in some scenarios for the vehicle to arrive with a high tank pressure that can only be filled from the high pressure reservoir since it is almost full or from the medium pressure reservoir followed by the high pressure reservoir.
Q12. How is the mass of gas in the reservoir maintained?
The mass of gas in the reservoir is maintained at a high level before the beginning of the second electricity peak pricing period, to reduce the activity of the compressor in the undesirable time band between, 17:00 and 19:00.
Q13. What are the control variables in the current problem?
The status of the compressor switch u and the status of the priority panel valves uhp, ump and ulp are the control variables in the current problem.
Q14. What is the main condition that could affect the performance of the strategy in a real life scenario?
The main conditions arising from assumptions in this study that could affect the performance of the strategy in a real life scenario is a difference between the forecast and actual minimum and maximum temperatures over a control horizon which can result in unexpected changes in pressure.
Q15. How does the approach prevent compressor activity in the second peak electricity pricing period?
The approach also succeeds in preventing compressor activity in this second peak electricity pricing period, furtherreducing the cost of electricity consumed for the day.
Q16. What is the main reason why the authors did not study the impact of limited infrastructure on the electric?
Their study recognized limited infrastructure as a major technological barrier to the market penetration of CNG vehicles in the United States of America.