Street lighting is important to establish the safety and comfort of drivers, riders, and pedestrians. The safety aspects of street lighting include the prevention of accidents and injuries while also reducing the risk of crime and violence. In terms of comfort, street lighting can increase the quality of life when outdoor activities take place at night. Nowadays, street lighting also functions to beautify an area by creating beautiful scenery with landscape illumination. In recent progress, there has been a huge increase in the number of street users globally, and it has become increasingly important to ensure the safety and good visual performance of the users through reliable street lighting systems [1
About 2.3% of the global electricity consumption is contributed by the public lighting particularly the street lighting [4
]. However, there is also huge potential for energy savings in street lighting. Lobão et al. [5
] predicted that there is more than 50% energy savings potential in street lighting, and they ascertained five criteria that influence the selection of efficient street lighting, namely price, power consumption, conductor loss depletion, beneficial life, and interest rate. Since it is critical to reduce the power usage as well as maintain good quality lighting surroundings and user safety, the major focus should be given on energy usage, production patterns, and energy efficiency programmes to promote energy efficiency of street lighting [6
]. The earlier road lighting technologies included high-pressure sodium (HPS), low-pressure sodium (LPS), and metal halide (MH) lights [7
]; however, more recent advances in lighting technology have enabled the development of solid-state lighting sources using LEDs. LEDs are preferable because of their high luminous efficacy, long lifetime, and high colour rendering index compared with conventional gas lights such as HPS and MH lights [9
Malaysia has been using LED for road lighting illumination since 2012 [10
]. Nonetheless, a local technical report by TEEAM [12
] did not recommend LED adoption during that time after they found out that LED does not have advantages over the existing road lighting technology based on five criteria, namely energy-saving, cost-saving, maintenance cost over 20 years, safety and security, and environmental impact [12
]. In addition, Mohd Yunin, Shabadin, Mohd Zulkifli and Syed Mohamed Rahim [11
] remarked that the LED for road lighting should not be installed in areas prone to fog and rain since it leads to glare in the eyes of drivers. Nevertheless, Malaysia’s electricity demand is largely fuelled by gas and coal (refer to Figure 1
) and the demand continues to rise for the past three decades [13
]. In adition, the electricity’s share of the total energy consumption increased from 17.9% in 1998 to 20.3% in 2018 [13
]. Hence, the Ministry of Energy and Natural previously known as the Ministry of Energy, Green Technology and Water targets a reduction of 10% in electricity consumption by 2025 from the energy efficiency sector [14
The energy price in Malaysia has also been increased as its price or electricity tariff is determined by Tenaga Nasional Berhad (TNB), the only electricity utility company in Peninsular Malaysia and the largest public-listed power company in Southeast Asia. The electricity tariff in Malaysia has been revised three times since 2008, and the latest revision took place in 2014. For street lighting use, there are two types of electricity tariffs; one that includes the maintenance work by TNB, which is currently at the current price of RM0.305/kWh after an increase from RM0.261/kWh, and the other rate that does not include the maintenance cost, which is currently priced at RM0.192/kWh from RM0.164/kWh [15
With the increased price of energy, the recent development of LED lighting technology, and increased awareness of the encouraging environmental impact of adopting street lighting technology, there is a need to revisit the feasibility of LED for road illumination. To date, the existing literature has not come to an agreement on the need to switch from conventional lighting to LED lighting, as well as aspects regarding the energy, cost, and environmental concerns particularly in the Malaysian context [11
]. These three aspects (energy, cost, and environmental concerns) are very crucial in adopting sustainable street lighting technology but lack of clear insights from these different perspectives would hinder the implementation of necessary measures. Therefore, more in-depth study is needed to apprehend the impact of adopting LED for road lighting in Malaysia.
In this light, the purpose of this study is to investigate the performance of LED in substitution for high-pressure sodium vapour (HPSV) road lighting in Penang Bridge, Malaysia using the Data Envelopment Analysis (DEA), a frontier-based optimisation approach, by modelling energy, cost, and environment together. The performance of LED and HPSV road lighting in this study will be measured by the technical efficiency and eco-efficiency of LED and HPSV road lighting. The remainder of this paper is organised into five sections. Section 2
delves into the concept of efficiency in DEA and introduces the theoretical aspect of the variables selected for the optimisation model from the review of the existing literature. We demonstrate our DEA model in Section 3
, the efficiency performance analysis of LED and HPSV road lighting in Section 4
, and the concluding remarks in Section 5
4. Results and Discussion
This section demonstrates the empirical findings from the Techno-Economic Analysis (TEA) and Data Envelopment Analysis (DEA) approach which help to give some insights into the performance of HPSV and LED road lighting in the Penang Bridge highway.
4.1. The NPV, IRR, ROI, Cash Flow, and Payback Period
This section describes the findings from the analysis on NPV, IRR, ROI, cash flow, and payback period. The lantern lifetime in the unit of year was computed to project the number of lanterns for the period of 11 years and the results are presented in Table 4
From Table 4
, at a daily usage of 12 h and an expected lifetime of 50,000 h, an LED lantern could last for approximately 11.42 years, while an HPSV lantern with an expected lifetime of 20,000 h could only last for 4.56 years. For the projected 11 years of implementation, the projected number of HPSV and LED lanterns to be acquired are 1191 and 397, respectively; that is HPSV lanterns require three times more replacement as compared to LED lanterns. In consequence, the installation cost for the implementation of LED lanterns would be much lower than HPSV lighting. More importantly, with a smaller number of more environmentally friendly lanterns to be implemented, the concentration of carbon dioxide emission can be reduced to a great extent for a period of 11 years. The implementation of LED lighting technology for road lighting promotes sustainable practices through the smart use of energy that not only meets the present needs, but also conserves them for future necessities.
summarises the costs related to the investment in HPSV and LED lanterns and the period of analysis for the investment made was assumed at 11 years, based on the findings from Table 4
reports the investment in LED lanterns. Annual saving is obtained by adding the annual electricity cost and replacement cost of HPSV lighting, then subtracting it from the annual electricity cost of LED lighting. Hence, the annual saving on replacing HPSV with LED lanterns is RM310,204.76 per year. By dividing the investment cost of LED lanterns by annual savings, the simple payback period for LED lantern replacement is 2.77 years. Therefore, the investment cost to be paid in the eighth month of the third year is as portrayed in Figure 2
. A simple cash flow from the investment in LED lanterns made for the 11-year period is shown in Figure 2
illustrates the negative values of cash flow representing the amount of investment made while the positive values represent the savings obtained. The first two years are the early phase of the LED adoption, which involves a large amount of investment in purchasing and installation of new lanterns. As such, Figure 2
depicts a negative cash flow because the investment needs a period of recovery before the return of investment can be achieved. From the third year onwards, positive trends are observed as the investment starts to contribute positive income through the savings from the replacement of HPSV with LED lanterns. Hence, in the eleventh year, the positive income obtained is RM2,552,747.40. In a total duration of eleven years, nine years of positive income can be preserved before the next phase of LED lantern replacement.
Information in Table 5
was further used to calculate the NPV, IRR, ROI, and discounted the payback period. The results are reported in Table 6
, where discount rates of 5% and 10% are considered [39
From the results in Table 6
, at a 5% discount rate, an investment of RM859,505.00 generates an NPV of RM1,717,184.26, an IRR of about 34.73%, and an ROI of about 1.08. The discounted payback period for this investment is 3.06 years. As the discount rate increases to 10%, the same amount of investment on LED lanterns will decrease the NPV to RM1,155,293.86, maintaining IRR and ROI at 34.73% and 1.08, respectively, and increases the discounted payback period to 3.42 years. NPV is at positive rates of 5% and 10% discount. Hence, the utilisation of LEDs for road lighting should be able to proceed due to the positive NPV even though a higher discount rate has been used.
A positive NPV indicates that the investment has a positive cash flow, in this case, results in savings. Additionally, an IRR of 34.73% for both 5% and 10% discount rate can be used as a reference to future ranks of LED lighting projects since it is a powerful evaluation index for investigating the profitability of projects. A total of 34.73% of IRR suggests that the probability of getting a profitable investment is almost as high as 35%. As the ROI is 1.08 or 108%, it suggests that RM1.08 is obtained for every Malaysian Ringgit (MYR) value of investment made on LED lanterns, and the range of 3 to 4 years is required to recoup the investment.
4.2. Technical Efficiency
This section illustrates the results using the DEA approach under the constant returns to scale (CRS) assumption on technology of the CCR model. This technical efficiency accounts for input variables (investment cost, operation cost, and energy consumption) and desirable output (lantern’s lifetime). The technical efficiency score
is acquired from Equation (6) in Section 3.2.1
. The results of the technical efficiency scores and ranks are presented for HPSV and LED road lighting in the Penang Bridge highway according to the type of road lighting technology. The average efficiency score for each type of road lighting is calculated to determine a summary of the road lighting technical efficiency. The technical efficiencies and ranks using the DEA model with CRS assumptions for HPSV and LED road lighting in the Penang Bridge highway together with the most important input variables are presented in Table 7
From Table 7
, there are nine DMUs with scores less than 100% that are regarded as inefficient. Inefficient scores are ranging from 14.11% to 83.76% and the only technical efficient or fully efficient DMU with a 100% score is LED4. LED2 ranked in the eighth place, out of ten, with a score of only 31.69%, while the other DMUs scoring lower than three HPSV road lighting technologies (HPSV4, HPSV3, HPSV1). This exhibits that LED2 does not utilise the input resources appropriately during its operation. Hence, it performs poorer than the conventional road lighting technology of HPSV.
In addition, the performance of DMU of HPSV4 is as good as LED5 and LED3, with scores of 65.98%, 61.94%, and 54.15%, respectively. One of the possible reasons for this finding is the less economical performance of LED lighting compared to the HPSV lighting. Tähkämö, Räsänen and Halonen [46
] found that although LED technology offers improved colour characteristics and lighting controls as compared to high-intensity discharge (HID) lights such as High-Pressure Sodium (HPS), HPS is more economical as compared to LED. As there are two input variables related to cost utilised in this study, the good performance of HPSV4 is not surprising.
Additionally, in the last column of Table 7
, it is found that for each evaluated DMU, the installation cost is the most important item in evaluating the performance of road lighting technology for this study except of LED2. It is because the DMU of LED2 demonstrates that the operation cost is the most important item in evaluating its performance. Therefore, with the inefficient score of 31.69%, LED2 could potentially reduce its operation cost by approximately 68.31%.
As mentioned in Section 3.3.2
, there are two important components of operation cost, namely electricity consumption cost and maintenance cost. The maintenance cost is influenced by the maintenance work done on the lanterns. According to PLUS Malaysia Berhad [45
], as LED technology is still new for the study site, the need for maintenance work such as the cleaning of the optics remains uncertain.
The other aspect of operation cost is the electricity consumption cost which is dependent upon on the electricity or energy consumption and the electricity tariff. Although it can be observed that there is a decrease in energy usage (based on Table 3
) by adopting LED lighting technology in Penang Bridge, none of the DMUs reflects the significance of energy consumption in deriving the technical efficiency scores. In addition, there are no changes in the electricity tariff during the study period. Hence, there is no evidence of electricity consumption cost contributing towards the operation cost at that point of time.
The installation cost of LED, however, are found and known to be higher than the conventional road lighting technology [4
], and, at the same time, the LED prices have continued to reduce due to the estimated 38 billion total sales of LED lighting products over the last five years [57
]. Therefore, it can be observed that two DMUs from LED lighting technology (LED4 and LED1) ranked in the first and second place, surpassing HPSV lighting technology. Still, the DMU of HPSV4 positioned in the third-rank. Thus, a future study can investigate the competitiveness of the current LED price as compared to the HPSV price as this is considered the limitation of this study.
In a DEA convention, a group of fully efficient DMUs serves as reference peers. From Table 7
, it can be observed that the only fully efficient DMU is LED4. Therefore, all inefficient DMUs have only one reference peer which is LED4. This indicates that for all evaluated DMUs to operate efficiently, their performance must be improved to operate similarly to LED4.
However, again, the mean efficiency score of LED road lighting technology is 66.31%, which is two times higher than the HPSV road lighting, with only 37.38%. This reflects that the efficiency of road lighting on the Penang Bridge highway has been improved with the adoption of LED technology. The inefficient scores in Table 7
further suggest the possible extent to which certain point inputs could be minimised while maintaining the existing outputs. The excellency and deficiency among the DMUs in this study is simply a relative relationship based on input and output components.
4.3. Comparing Technical Efficiency Groups Test
This section aims to compare the technical efficiency scores of HPSV and LED road lighting. To validate the difference in technical efficiency scores between HPSV and LED, a non-parametric Wilcoxon Signed-Rank Test is utilised, and Table 8
presents the results.
As the results in Table 8
show a p
-value of less than 0.05 (p
< 0.05), it can be concluded that there is a statistically significant difference in the technical efficiency scores between HPSV and LED road lighting.
The eco-efficiency using the DEA model accounts for input variables (investment cost, operation cost, and energy consumption), desirable output (lantern’s lifetime), and undesirable output (carbon dioxide emissions). The eco-efficiency score using the DDF approach is acquired from Equation (11) in the methodology section. The results of the eco-efficiency scores and ranks are presented for HPSV and LED road lighting in the Penang Bridge highway. The average efficiency score for each type of road lighting is calculated in order to determine the eco-efficiency of road lightings. With CRS assumptions for HPSV and LED, the DDF eco-efficiencies are presented in Table 9
The eco-efficiency scores in Table 9
show the level of undesired output reduction. For instance, the DMU of LED1 was 90.81% efficient. This finding suggests that LED1 could decrease its undesirable output by 9.19% to achieve full efficiency. In addition, it can be observed that the DMU of HPSV1 and HPSV3 have almost the same performance as LED2, with the scores of 30.41%, 33.92%, and 36.88%, respectively.
Additionally, the HPSV road lighting technology DMUs are the most eco-inefficient DMUs, ranked in the seventh place and below, except for the DMU of HPSV4 which ranked in the first place, together with LED4. It means that, as compared to other DMUs in this study, the DMU of LED4 and HPSV4 are the most eco-efficient DMUs. This shows that HPSV road lighting can perform as good as LED lighting technology when energy, cost, and environmental concerns are considered altogether in the model.
The eco-efficiency scores are quite similar to the technical efficiency scores for all HPSV DMUs except for the DMU of HPSV4. HPSV4 is ranked at third by technical efficiency score and rises to first by eco-efficiency score. This shows the importance of the environmental variable in the model as when the carbon dioxide emission variable is included in the model; the result demonstrates that HPSV lighting technology is able to perform as good as LED lighting technology. This finding supports the findings by Tähkämö and Halonen [17
] from their environmental performance assessment using life cycle assessment (LCA) of road lighting. Although they found that the environmental performances of the HPS and LED luminaires are on the same level during the study period, none of the previous studies has included energy, cost, and environmental concern altogether in one model.
The average eco-efficient score for LED road lighting technology is 74.77%, and this is way above the performance of the HPSV road lighting, which is only at 40.06%. Our finding concurs with the findings of Khan and Abas [79
] who support LED luminaires that are being recognised as environmentally efficient solutions for roadway lighting [47
4.5. Comparing Eco-Efficiency Groups Test
This section aims to compare the eco-efficiency scores of HPSV and LED road lighting by performing the non-parametric (Wilcoxon Signed-Rank Test) test. Table 10
presents the results.
The results in Table 10
show the results of the Wilcoxon signed-rank test, where the p
-value of 0.068 is more than 0.05 (p
> 0.05). However, as p
< 0.10, it can be still concluded that the eco-efficiency scores between HPSV and LED road lighting are still statistically different but at the 10% significance level.
4.6. Comparative Efficiency between CCR and DDF Approach
This section compares the findings in Section 4.2
) and Section 4.4
) from the DEA CCR and DDF approach summarised in Figure 3
. Findings from Figure 3
clearly depict the better performance of LED, thus emphasizing the importance of the environmental factor in measuring the impact of adopting LED road lighting technology in the Penang Bridge highway.
From Figure 3
, there is an increase in the number of fully efficient DMU when we considered the environmental concern variable in the model. By the CCR model, only LED4 is considered fully technical efficient but with the DDF model, HPSV4 is also recognised as fully eco-efficient, together with LED4. It can be also observed that the eco-efficiency score is less than the technical efficiency score for HPSV lighting technology except for HPSV4. The increase of the eco-efficiency score as compared to the technical efficiency score for LED lighting technology is in accordance with the findings from Enongene, Murray, Holland and Abanda [66
] and Khorasanizadeh, Parkkinen, Parthiban and Moore [20
]. The study revealed that the implementation of LED lighting produces much lower carbon dioxide emissions as compared to the conventional lighting of CFL and incandescent lamps in residential buildings. Hence, this proved the environmental benefits of LED lighting technology. Carbon dioxide is the primary greenhouse gas (GHG) emission and the main contributor to climate change [80
]. This study has also proven that carbon dioxide emission is an important variable that should not be neglected when measuring the impact of adopting road lighting technology.
This study employed Techno-Economic Analysis (TEA) and Data Envelopment Analysis (DEA) to measure the performance of HPSV and LED road lighting technology in the Penang Bridge, Malaysia. Under the TEA approach, this study applies the payback period, cash flow, net present value (NPV), internal rate of return (IRR), and return on investment (ROI) to appraise the profitability of investment on LED road lighting adoption in the Penang Bridge. The positive NPV and IRR obtained indicate the opportunity of possible profitable returns. The ROI of greater than one signifies that the investment can bring profit after 3 to 4 years of LED road lighting adoption. Therefore, there is positive evidence in terms of the financing costs and structures when adopting LED road lighting technology.
Specifically, the application of CCR DEA techniques in this study evaluates the performance of LED in substitution for high-pressure sodium vapour (HPSV) road lighting in the Penang Bridge. By modelling energy (energy consumption), cost (installation cost and operation cost), and environment (carbon dioxide emissions), the findings reveal that the mean performance of technical efficiency for LED road lighting technology is two times higher than HPSV road lighting, with 66.31% and 37.38%, respectively. This study confirms that the efficiency of road lighting on the Penang Bridge highway is improved with the adoption of LED, where the installation cost is the most important item in evaluating the performance of road lighting technology. The crucial aspect in the installation cost is the lantern price; thus, a future direction of this study is to investigate the competitiveness of the current LED price as compared to the HPSV price which further encourages the adoption of the latest LED technology.
The other significant empirical finding is discovered from the DDF DEA model, in which the average eco-efficient score for LED (74.77%) exceeds the performance of HPSV (40.06%) road lighting. By comparing efficiency of the CCR and DDF models, it can generally be observed that the HPSV technology produces lower eco-efficiency than the technical efficiency scores while the LED technology generates higher eco-efficiency compared to its technical efficiency scores. This finding could suggest that environmental-friendly road lighting technology would further improve the efficiency level of road lightings or lanterns, and undesirable output is an important variable that must be taken into account when measuring the impact of adopting road lighting technology.
Nevertheless, not considering the variables for the meteorological conditions in the model development of this study is a limitation of this study. Future study may include weather and meteorological parameters in modelling the performance of LED road lighting.
The substitution of energy-inefficient lights with energy-efficient lights in road lighting is a very crucial step to reduce the costs energy generation as well as the emissions of carbon dioxide. This study demonstrates that LED road lighting technology has a great potential in energy savings, powerful and quality lightings besides promising investment returns. Moreover, carbon dioxide emission is a critical variable that should not be neglected when assessing the performance of road lighting technology. With the exponential increase in the number of streetlights, there would be a rapid increase in the energy demand and the most preferred road lighting technology would be the one that is not only cost effective, but significantly reduces carbon emissions. The LED renewable energy industry that promotes zero carbon emissions has the potential to establish an affordable, clean, carbon-free energy system for road lighting both in the urban and rural areas.