Technical–Economic Analysis of the Solutions for the Modernization of Lighting Systems

Abstract

In the context of the electricity crisis, measures are needed to reduce energy consumption. The case study was conducted on the lighting system at a university sports hall. To determine the efficiency and quality, the lighting systems and technical characteristics of the sources used were identified, lighting level measurements were made, the luminotechnical coefficients and the power of the whole lighting system were calculated and the results were compared to the values set out in the standards. Following analysis, the lighting system was found not to meet the quality requirements and was energy inefficient. For financial efficiency, only the replacement of lighting was sought, keeping the same equipment and granting the same facilities to the building users. Some lighting source options were analyzed and the option to have the highest luminous efficacy and the highest energy class was chosen. The analysis shows that the investment is amortized within a maximum of 17 months. The innovative aspect is based on linking the measurements with the determination of power and the proposal of modernization solutions, which shows the need for investments to ensure the quality of the system and the increase in energy efficiency.

1. Introduction

The European and global energy crisis, as well as the continuing rise in the price of electricity, are leading to a slowdown in activity, especially for large energy consumers, thus having a negative impact on the workforce [1]. This requires measures for the rational use and optimization of energy consumption.

In Ghana, the energy crisis between 2012 and 2015 led consumers to find new energy sources, and, respectively, to find sustainability solutions by reducing electricity demand in the long term [2]. In the case of household consumers, reducing the demand for electricity can be carried out by using sustainable and energy-efficient systems.

Worldwide, the energy consumption from the use of lighting sources represents about 19% of total consumption [3]. In some cases these light sources are high consumers of electricity and lead to alterations in the quality of the electricity by the deformation of the voltage and current waveform [4] caused by the introduction of harmonics. These reduce the power factor [5] and cause reactive energy costs. To reduce power consumption, current sources have been replaced by LED sources; they also have the advantage of a longer lifetime and a higher luminous efficacy [6]. Optimal operating solutions are also implemented to reduce power consumption (dimming depending on a pre-set timetable [7], smart remote measurement, and control systems with GPS, GPRS/4G technology) [8], automatic detection of people, environmental conditions, lighting defects [9].

Respecting the quality indicators of lighting systems is a necessity. It is known that lighting values above and below the limits given in the standards may cause certain ailments to occur to persons working in that area, such as eye fatigue, headaches, sleep disturbances [10], etc. Furthermore, appropriate lighting can also have beneficial effects such as the alleviation of depression and Alzheimer’s disease [11], improvement of disease through phototherapy, inactivation of viruses by germicidal irradiation [12], growth and development of plants by stimulating the photosynthesis process [13], etc. In the case of street lighting, an appropriate level of illumination helps pedestrians detect obstacles and recognize facial emotions [14], gives a sense of security for people who work outdoors at night [15], and can also reduce the risk of crime or robbery by the presence of ambient light [16].

Whatever the type of lighting system, certain indicators to validate the light’s quality must be provided; the values of these indicators should fall within the values set out in the standards, according to the activities carried out in the illuminated areas or by the characteristics of the illuminated streets [17].

At EU level, the decision that incandescent conventional and halogen lamps would gradually be withdrawn from the EU market from 2009 to 2012 was taken by a technical committee of experts from the European Commission, and that they would be replaced by tubular fluorescent lamps, compact fluorescent lamps (LFC), or LED lamps to ensure that the power used in interior and exterior electric lighting systems was reduced.

In many cases, current sources have been replaced by LED sources without considering the technical characteristics of the sources (luminous flux, color temperature) [18] and without photometric measurements being carried out before and after replacement. Therefore, the resulting luminotechnical indicators are no longer checked if they are within the range indicated in the applicable standards.

If after the replacement of light sources the lighting quality indicators are not within the range indicated, design optimization is required using specialized software [19], which means finding the optimal solution for positioning the stalk [20], the length and inclination of the harp [21], and the source of illumination, according to the photometric curve [22]. The quality of the electricity used/influenced by the lighting system must also be considered because the lighting system can cause the waveform to change [23] and the introduction of voltage harmonics [24].

Special attention must be paid to light pollution caused, in particular, by street lighting systems [25]. This happens when the lighting equipment is not properly placed, or the light sources are too bright. Thus, in Krakow (Poland) during COVID restrictions, street lighting was turned off for one month. Following measurements, it was found that the luminous energy radiated in the sky decreased by about 50%, also reducing the brightness in the night sky by about 40% [26]. Environmental pollution may also be caused by an inadequate collection of lighting sources; this requires that used or defective bulbs are recycled and treated properly [27].

For the rational use of energy and to ensure the luminotechnical indicators that are necessary to perform the activities alongside the optimal design are met, the correct choice of lighting system, the use of natural light to provide visual comfort, and the reduction of expenditure and pollution should be taken into account as far as possible [28].

The theme proposed aims to find solutions to modernize lighting systems to save energy, and to ensure a lighting-related climate and increase sustainability while emphasizing the role of cost accounting as a part of cost management accounting as the basis for decisions: in this case, decisions relating to the modernization of the lighting system.

Cost accounting represents the allocation of expenditure to withdrawals, such as the cost of goods/services/works that are a part of management accounting [29]. It consists of three parts that are all receivers of inputs from the “measurement of costs” procedure of conversion of incurred costs (or their obligations) in calculated costs.

In order to achieve this objective, a luminotechnical and energy analysis of the lighting system at the sports hall of Babes-Bolyai University, Reșița University Centre, is carried out in order to verify the quality indicators of the system used and determine the power installed in this system and the power consumed on a monthly basis for an average of 10 h/day operation.

Values of lighting quality indicators (average lighting level, uniformity of lighting) are compared to the values in the standards to determine system performance. The identification of the solutions for replacing the lighting sources with energy-efficient sources, capable of providing both system quality indicators and a reduction in consumption, is realized by analyzing three types of LED lighting sources.

The measurement of costs and the benchmarking carried out aim at setting the depreciation time of the investment, considering several aspects: an increase in energy efficiency, decrease in electricity expenditure, reduction in pollution, and lower costs of sport and related activities due to the positive deviation in the quantity consumed.

LED technology has all the advantages of efficient, safe, and economical use. The light reaches a maximum intensity quickly without a warm-up time and is pleasant for the eye; the bulbs do not generate heat, do not produce light in a spectrum other than the visible one, do not contain mercury, energy consumption is considerably reduced, and all the energy consumed by an LED bulb turns into visible light. However, even with so many advantages, the constraints prevent the acceleration in the pace of the replacement of outdated lighting technologies due to limited financial resources; only the costs of replacing the technology are considered [30], not the savings resulting from the reduction in consumption over time [31], and this is precisely because of the decision makers’ lack of knowledge in the field.

Other solutions that help reduce electricity consumption are the use of light dimming systems within lighting sources. A study carried out in 115 metro stations in Barcelona found that by using intelligent lighting control systems, depending on the occupancy of the stations, a reduction of 36.22% in the basic consumption of lighting systems was achieved [32]. A similar percentage reduction in electricity (30%) was also identified in the case of street lighting that uses an adaptive lighting system depending on traffic conditions [33]. Moreover, in order to ensure an adequate level of lighting, it is necessary to periodically clean the lighting systems [32].

In Romania, there are a large number of educational institutions that have outdated lighting systems and are large consumers of energy. The share of funds allocated for the purchase of lighting systems to reduce energy consumption is low. This paper shows the savings that are made just by replacing lighting sources with energy-efficient sources, without considering the use of modern technologies for detecting the presence of people or reducing the luminous flux according to a predetermined schedule or by the light from outside.

The innovative aspect of the study is that it is based on presenting the photometric measurements and the calculation of the luminotechnical coefficients, combined with the measurement of the installed power and the total installed power in each space, and with the modernization proposal, respectively, these calculations are combined with the calculation of the installed capacity in the lighting system proposed. In order to keep the investment as low as possible, we have only proposed to replace the current sources with LED sources, keeping the same luminaires.

If we replace the current lighting sources with energy-efficient ones, the electricity consumption will be reduced by more than 50%, simultaneously achieving the realization of a lighting system that meets the quality luminotechnical coefficients provided in the standards.

2. Materials and Methods

2.1. The Methodology Used to Establish the Quality Luminotechnical Coefficients and the Installed Power in the Lighting Systems Analysed

Conventional measurement methods were used for the measurement of luminotechnical parameters, using different portable meters, or modern technologies [34]. The measurement of the illumination values was performed using the digital luxmeter shown in Figure 1, the technical parameters of which are presented in

Table 1. Technical parameters of the digital luxmeter.

Measurement Unit (Lx)	Measurement Errors (Lx)
0 ÷ 20	0.01
0 ÷ 200	0.1
0 ÷ 2000	1
0 ÷ 20,000	10

[35].

The luxmeter belongs to the UNITEST range; it was manufactured in accordance with the ISO 9002—NFX 50-121 Standard, and the calibration is conducted at 3 years, using a standard light source, with a color temperature of 2856 K. The luxmeter is powered by a 9 V battery; the display is LCD digits. The use of the luxmeter for measurements is conducted only after exposing the photocell, for 15 min, to ambient lighting, to stabilize the phenomenon of photometric conversion.

For taking measurements of the illumination level of each area, its dimensions are determined, after which it is divided into squares not more 1.5 m, within which measurements are made.

For each area it is determined:

• Minimum value of illuminance, E_min, being the lowest value identified by the measurements.
• Maximum value of illuminance, E_max, being the highest value identified by the measurements.
• Mean value of illuminance, E_med, calculated as the arithmetic mean of the values of the lighting measured in this area.
• Uniformity of illuminance on the surface of the working plane, U₀₁(E), defined by the equation [36,37,38,39]

U₀₁(E) = E_min/E_med

(1)

5.

Uniformity of illuminance on the actual working plane (visual task area), U₀₂(E) defined by the equation [36,37,38,39]

U₀₂(E) = E_min/E_max

(2)

6.

Type of lighting sources, their number, and their power.

• Luminous efficacy, e_source, of the lighting sources defined by the equation [37]

  e_source = Φ_source/P_source

  (3)

  where Φ_source is the luminous flux emitted by the source, and P_source is the source’s power; both sizes are noted on the box with the nominal data of the source of illumination. These values are those indicated during the implementation. The luminous flux value decreases as the source life decreases, it follows that we expect that luminous efficacy is lower than the nominal one.

• Installed power capacity in each area (area a), calculated according to the number of lighting sources and their power [37], by the equation

P_ia = No_source × P_source

(4)

• Total installed power capacity in the lighting system at Moroasa Sports Hall, calculated according to the powers installed in each space [37], by the equation

  P_t = P_ia + P_ib + P_ic + … + P_iw

  (5)

  where the areas a, b, c, …., w are analyzed.

In order to perform the measurements, it was necessary for the lighting sources to be connected at least 20 min in advance, so that the luminous flux emitted by them was stabilized. After exposing the photosensitive cell to the luxmeter, an adjustment time was required at a certain illumination level, thus a time of approximately 5 min was required for each measurement performed, so that the measured value could be stabilized.

The values of the average lighting and the uniformity of lighting were compared with the values set out in the standards to determine the luminotechnical quality of the lighting system. It was considered that the sports hall analyzed is level 2, designated for competitive, local, regional practice [40].

2.2. The Methodology Used to Determine Modernization Solutions

The modernization solutions agreed at this stage consisted of the replacement proposal of current lighting sources with energy-efficient sources, sustainable and capable of providing the luminotechnical coefficients set out in regulations and standards.

For this, between 3 and 5 types of lighting sources were analyzed, from three different producers, power compatible with current lighting. The analysis was made with those sources that had technical luminotechnical characteristics at least equal to those existing.

For the handball court, it was decided to replace the luminaire.

For each analyzed area, by using Equations (4) and (5), the installed capacity was calculated with the three sources/appliances proposed.

According to the cost of the lighting sources/appliances analyzed, the cost of replacing them was determined and the depreciation period of the investment was calculated.

2.3. The Methodology Used to Calculate the Costs of Implementing a Solution Change on Lighting of a Sports Centre

For the analysis of the economic efficiency of the lighting system, according to the total installed capacity, the electricity consumed [37] on a monthly basis W_la, was calculated in each area at 10 h/day operation, 30 days/month, using the equation

W_la = P_ia × 10 × 30

(6)

and total monthly electricity [37]

W_tl = W_la + W_lb + W_lc + … + W_lw

(7)

The cost of C_W electricity [37] consumed according to the criterion set out must consider the cost of active electricity W_a, inductive reactive W_ri, capacitive reactive W_rc and additional fees (network extraction, system service, networking, high voltage distribution, medium voltage distribution, low voltage distribution, cogeneration, green certificates, excise duty). In the case study, inductive and capacitive reactive energy was neglected (with very low monthly average values compared to the value of active energy); for the monthly electricity cost, the following equation was established:

C_W = W_tl × (C_Wa + C_s),

(8)

where C_Wa represents the cost/1 MWh of the active electricity, and C_s represents the cost of additional fees.

3. Results

3.1. Quality Indicators and Capacity Installed in the Lighting Systems Analysed

For each area, the number of lighting appliances, the type and number of lighting sources, their power and luminous flux, and the lifetime was determined. Using Equation (3), the luminous efficacy was calculated, and using Equation (4) the installed capacity was calculated. The power consumption was also considered to determine the installed power. The results obtained are presented in

Table 2. Characteristics of the analyzed lighting system and installed power.

Area	Type of Source	No. of Appliances	No. of Sources	Power/Source with Ballast (W)	Luminous Flux of Source (Lm)	e (Lm/W)	Pi (W)	Standard Source Life (h)
Hall 1	Incan	2	1	25	200	8	50	1000
Hall 2	Fl.tub	6	4	20	1300	62	480	15,000
Toilet 1	Fl.tor	1	2	24	1200	50	48	6000
Medical office	Fl.tub	2	4	20	1300	62	160	15,000
Changing room 1	Fl.tub	2	4	20	1300	62	160	15,000
Changing room 2	Fl.tub	2	4	20	1300	62	160	15,000
Changing room 3	Fl.tub	1	4	20	1300	62	80	15,000
Changing room 4	Fl.tub	1	4	20	1300	62	80	15,000
Bathroom	Fl.tor	1	2	24	1200	50	48	6000
Gym	Incan	20	2	25	200	8	1000	1000
	Fl.tub	14	4	20	1300	62	1120	15,000
Handball court	Met.Hal	46	1	415	32,500	78.31	19,090	20,000
Shower room	Fl.tor	2	2	24	1200	50	96	6000
Jacuzzi hall	Fl.tor	2	1	24	1200	50	48	6000
	Fl.tub	1	2	20	1300	62	40	15,000
Jacuzzi room	Fl.tub	4	4	20	1300	62	320	15,000
Referee changing room 1	Fl.tor	3	1	24	1200	50	72	6000
Referee changing room 2	Fl.tor	3	1	24	1200	50	72	6000
Toilet 2	Fl.tor	1	2	24	1200	50	48	6000
Hall3 (floor)	Fl.tub	17	4	20	1300	62	1360	15,000
Classroom	Fl.tub	10	4	20	1300	62	800	15,000
Meeting room	Incan	13	2	25	200	8	650	1000
Total installed power in the lighting system							26,302 W

. In this table, the incandescent sources are noted as Incan, the tubular fluorescent sources are noted as Fl.tub, the toroidal fluorescent sources are noted as Fl.tor, and the metal halide sources are noted as Met.Hal.

Lighting level measurements were taken in each area using the luxmeter and the methodology indicated in Section 2.1 and that set out in the standards. The minimum, medium, and maximum values of the i illuminance level, and the uniformity of illuminance in the working plane, on the actual working plan, and the minimum values set out in the standards are presented in

Table 3. The values of the lighting coefficients.

Area	Measured and Calculated Values					Provisions of Standards
	Emin (Lx)	Emed (Lx)	Emax (Lx)	U01(E)	U02(E)	Emed (Lx)	U01(E)	U02(E)
Hall 1	179	465.3	942	0.38	0.19	150	0.6	0.5
Hall 2	82	250.3	520	0.32	0.16	150	0.6	0.5
Toilet 1	90.5	94.6	98.9	0.95	0.91	200	0.6	0.5
Medical office	154	324.3	422	0.47	0.36	500	0.6	0.5
Changing room 1	290	400.5	526	0.72	0.55	150	0.6	0.5
Changing room 2	273	398.2	503	0.69	0.54	150	0.6	0.5
Changing room 3	181	229.1	358	0.79	0.51	150	0.6	0.5
Changing room 4	172	221.7	346	0.78	0.5	150	0.6	0.5
Bathroom	116	200.5	265	0.58	0.44	200	0.6	0.5
Gym	134	250	400	0.54	0.33	300	0.7	0.5
	175	454	657	0.39	0.27	300	0.5	0.5
Handball court	125	140	157	0.89	0.8	200	0.6	0.5
Shower room	123	200.5	250	0.61	0.49	150	0.6	0.5
Jacuzzi hall	403	562.3	678	0.71	0.59	200	0.6	0.5
	45	136.2	230	0.33	0.2	150	0.6	0.5
Jacuzzi room	52	147.6	228	0.35	0.3	150	0.6	0.5
Referee changing room 1	134	137	140	0.97	0.96	200	0.6	0.5
Referee changing room 2	70	235.3	502	0.3	0.14	150	0.6	0.5
Toilet 2	334	573.1	883	0.58	0.38	300	0.6	0.5
Hall 3 (floor)	115	320	482	0.35	0.24	300	0.6	0.5
Classroom	116	200.5	265	0.58	0.44	200	0.6	0.5
Meeting room	134	250	400	0.54	0.33	300	0.7	0.5

.

For an overview we plotted (Figure 2) the values of the averaged illuminance (green lozenge), and the calculated values that were higher (blue squares) and lower (yellow triangles) than the normalized values.

It is noted that, in most cases, the medium illuminance is much higher than the normalized one, which may cause visual discomfort.

Keeping the same symbolization as in Figure 2, in Figure 3, we graphically represent the comparative analysis of the illuminance uniformity.

3.2. Analysis of Modernization Solutions

In order to upgrade, replacement of the current sources by LED sources was chosen. Therefore, proposed was:

• The replacement of the filament sources and tubular fluorescent sources by LED sources with an Edison socket;
• The replacement of tubular fluorescent sources by LED tubular sources;
• The replacement of metal halide sources by LED projectors.

In

Table 4. The values of the lighting coefficients.

Type of Source	Supplier	Power/Source (W)	Luminous Flux (Lm)	Color Temperature (°K)	Average Life Expectancy (h)	Energy Class	e (Lm/W)	Price (EUR)
LED with socket E 27	Supplier 1	10	1055	6500	20,000	A+	105.5	2.78
	Supplier 2	10	1400	6500	20,000	A++	140	3.798
	Supplier 3	10	1160	6500	30,000	E	116	1.984
	Supplier 4	10	1055	4000	10,000	A+	105.5	2.2
	Supplier 5	9	910	6500	20,000	F	101.1	1.796
Tubular LED	Supplier 1	9	900	6500	40,000	E	100	2.754
	Supplier 2	9	900	6500	40,000	F	100	1.984
	Supplier 3	9	900	6500	30,000	E	100	1.876
	Supplier 4	8	800	6500	15,000	A+	100	6.288
LED projector	Supplier 1	112	13,700	5700	100,000	-	122.3	150
	Supplier 2	146	21,439	4000	140,000	-	147	155
	Supplier 3	150	18,000	6400	30,000	-	120	199.2

, the technical characteristics of the sources/the proposed appliances and their price are presented.

For the analysis, it is proposed to choose the sources that have the highest luminous efficacy; the analysis is therefore made with LED sources with socket E 27 from supplier 2, with tubular LED sources from supplier 4 (considering the energy class too), and with LED projectors from supplier 2.

3.3. The Cost of Electricity Consumed in the Standard Lighting System

To determine the cost related to the electricity, the invoice of August 2021 was analysed. It was noted that for 1 MWh active energy, 55.6 EUR must be paid, and the additional fees for 1 MWh were 55.345 E.

Considering that the lighting system operates permanently in all the areas presented, for 10 h/day, 30 days/months, using the total power P_t installed in the lighting system, (Table 1), and Equations (6) and (7), the total monthly electricity is calculated W_tl

W_tl = P_t × 10 × 30 = 26302 × 300 = 7890.6 (kWh)

(9)

The cost of monthly electricity for the situation analysed would be

C_W = W_tl × (C_Wa + C_s) = 7.8906 × (55.6 + 55.345) = 875.423 (EUR)

(10)

It is noted that the electricity amount that should be paid, for the situation analysed, would be considerable, so modernization solutions should be found. In fact, this amount is much lower than the actual cost due to the fact that the lighting system works only in certain areas, and the service life and the period are much less.

3.4. Calculation of Costs Associated with Implementing a Replacement Solution Regarding the Lighting of a Sports Center

According to the solutions chosen for the replacement of the lighting sources, we have calculated the installed capacity in each area analysed (

Table 5. The power installed in the proposed lighting system and the cost of the investment.

Area	Type of Source	No. of Appliances	No. of Appliances	Power Source Current System (W)	Power Source System Proposed (W)	Pi Current System (W)	Pi System Proposed (W)	Investment Costs (EUR)
Hall 1	Incan	2	1	25	10	50	20	7.596
Hall 2	Fl.tub	6	4	20	8	480	192	150.912
Toilet 1	Fl.tor	1	2	24	10	48	20	7.596
Medical office	Fl.tub	2	4	20	8	160	64	50.24
Changing room 1	Fl.tub	2	4	20	8	160	64	50.24
Changing room 2	Fl.tub	2	4	20	8	160	64	50.24
Changing room 3	Fl.tub	1	4	20	8	80	32	25.152
Changing room 4	Fl.tub	1	4	20	8	80	32	25.152
Bathroom	Fl.tor	1	2	24	10	48	20	7.596
Gym	Incan	20	2	25	10	1000	400	151.92
	Fl.tub	14	4	20	8	1120	448	352.128
Handball court	Met.Hal	46	1	415	146	19,090	6716	7130
Shower room	Fl.tor	2	2	24	10	96	40	15.192
Jacuzzi hall	Fl.tor	2	1	24	10	48	20	7.596
	Fl.tub	1	2	20	8	40	16	12.573
Jacuzzi room	Fl.tub	4	4	20	8	320	128	50.304
Referee changing room 1	Fl.tor	3	1	24	10	72	30	11.394
Referee changing room 2	Fl.tor	3	1	24	10	72	30	11.394
Toilet 2	Fl.tor	1	2	24	10	48	20	7.596
Hall 3 (floor)	Fl.tub	17	4	20	8	1360	544	427.584
Classroom	Fl.tub	10	4	20	8	800	320	98.748
Meeting room	Incan	13	2	25	10	650	260	100.608
Total						26,302	9608	9003.281

).

For a quick comparative analysis, Figure 4, Figure 5 and Figure 6 show the installed capacities in the current lighting system and those that result after the modernization by using the LED sources proposed.

It is noted that the installed capacity in the proposed lighting system represents 36.53% of the installed capacity in the current system.

If we replace the current lighting system with the proposed sources, the monthly electricity value would be

W_tl = P_t × 10 × 30 = 9608 × 300 = 2882.4 (kWh)

(11)

C_W = W_tl × (C_Wa + C_s) = 2.8824 × (55.6+55.345) = 319.788 (EUR)

(12)

If it is considered that presence sensors are introduced in the current lighting system (except for the lighting system in the halls where there are sports activities), and the average duration of operation of the lighting sources in the analyzed spaces (except for the handball and gym rooms) is 2 h/day it is determined that:

-

the amount of energy consumed by the current lighting system would be

W_tls1 = P_t1 × 10 × 30+P_t2 × 2 × 30 = 21.210 × 300 + 5.000 × 60 = 6.663 kWh

(13)

where P_t1 represents the power in the lighting system with sensors and P_t2 represents the power in the lighting system without sensors. There is a 15.55% reduction compared to the situation in which the lighting system does not have presence detection sensors.

-

the amount of energy consumed by the proposed lighting system would be:

W_tls2 = P_t1 × 10 × 30 + P_t2× 2× 30 = 7.564× 300 + 2.044 × 60 = 2.391,84 kWh

(14)

There is a reduction in energy consumption of 64.1% compared to the situation in which the lighting system would be maintained and presence detection sensors would be introduced in transit areas, and a reduction of 69.69% compared to the current situation.

4. Discussion

If we calculate the difference between the monthly cost of electricity, according to the two situations analyzed, we conclude that we would save 555.635 EUR each month. With this saving, if the proposed lighting sources were purchased, the investment would be recovered in a maximum of 17 months, relatively fast.

The analysis can be continued with the optimal luminoengineering design, using several types of energy-efficient lighting sources.

The submitted case study reveals that the analysed lighting system is underperforming luminotechnically, as the average lighting in seven analysed areas is higher than that specified in the standards. With regard to the illuminance uniformity, it is concluded that in nine analyzed areas, this is much lower than that recommended; this is also because the luminous flux decreases as the service life increases.

As to the type of sources used in the current lighting system, it is concluded that their luminous efficacy is under 100 Lm/W, which proves their inefficacity. The high value of the capacity installed in the current lighting system causes a large amount of energy to be consumed and a high monthly cost.

For modernization, the technical characteristics and the prices of a minimum three types of lighting sources were analyzed and, for the case study, sources with a higher luminous efficacy were chosen: those belonging to the minimum energy class A. As a modernization solution, it was decided to replace the current sources with LED sources compatible with the installation, and for the handball court, it was decided for the current projectors to be replaced with LED projectors.

In the case of the implementation of the proposed solution, it is noted that the installed capacity in the lighting system represents 36.53% of the installed capacity in the current system, which would lead to a reduction in the electricity cost of 63.46%, under the above calculations.

If we invested this saving in the proposed lighting system, it would be amortized within a maximum period of 17 months, which is reasonable. Considering that the lighting system was fitted in 2016, most of the sources have exceeded their lifetime, so it is possible that they could break down at any moment. For the foregoing reasons, it is proposed to gradually replace the existing sources with energy-efficient and luminotechnical sources.

If the modernization of the analyzed lighting system only considers the replacement of sources and the installation of presence detection sensors, for the analyzed situation, the energy consumed would be reduced by approximately 69.69%, so a substantial reduction. The analysis did not take into account the energy consumption of the sensors and their frequency of use, this being the subject of a future analysis (during the pandemic, such measurements could not be made as the spaces were not used to their full capacity due to the imposed legislative restrictions).

5. Conclusions

Given the fact that the prices of lighting sources, especially of electricity, have increased a lot in 2022, the investment in replacing the classic lighting systems will be paid off quickly. Thus, the proposed solution is a priority, which will contribute to increasing energy efficiency and the sustainability of the lighting systems.

The resulting conclusions show the need for technical and economic analysis of the lighting systems used. In the context of EU government funding for energy efficiency projects, even a modernization based solely on the replacement of lighting sources leads to a substantial reduction in electricity consumption.

The solution for replacing lighting sources can be complemented by other solutions that contribute to even lower power consumption. Thus, presence detection sensors can be installed and the lighting level can be reduced by dimming systems. We can conclude that the more complete and complex the technical solution for modernizing a lighting system is, the lower the energy consumption is.