Technoeconomical analysis of stand-alone photovoltaic led street lighting systems for seven geographical regions of Turkey

Demand for energy increases rapidly due to population, economic growth and technological developments. While accompanied by greater prosperity, rising demand creates new challenges. Consumers require more energy resources and higher consumption of fossil fuels leads to higher greenhouse gas emissions, particularly carbon dioxide (CO2), which contribute to global warming. Photovoltaic technology, which does not need fossil fuel, can provide a green and sustainable alternative to energy consumption needs by reducing CO2 emissions. Structures of solar energy systems are suitable for meeting the energy consuptions of street lighting installations. Today, stand alone solar LED street lighting systems, which can only be feasibly used in rural areas where transportation is difficult and grid electricity does not reach, is becoming attractive in the rest of the world due to the decrease in photovoltaic panel, battery and LED luminaire costs. Developments in material technology have made it possible to use lower powered LED luminaires in street lighting systems which led to make smaller photovoltaic panel and battery sizings in stand alone street lighting systems. In this study, technoeconomic analysis of stand alone solar LED street lighting systems for seven regions of Turkey have been carried out. Literature review has been made over existing studies and solar energy potential of Turkey has been investigated. Structure and components of stand alone photovoltaic LED lighting systems have been introduced. Street lighting criteria, national regulations and technical specifications have been explained and information about modelling and simulations of the systems have been given. DIALux software has been used for street lighting calculations and HOMER software has been used for modelling and simulations. Calculations for seven geographical regions, three street lighting classes (M3, M4 and M5) and maximum - minimum pole spacing scenarios have been made and in addition to current case, future projections have been carried out for cases of 1) %25 increase in electricity unit prices, 2) %25 decrease in photovoltaic panel and battery costs, 3) %50 decrease in photovoltaic panel and battery costs and 4) %25 increase in electricity unit prices and %50 decrease in photovoltaic panel and battery costs. As a result of DIALux calculations; 46W and 25W luminaires for M5 street lighting class with one sided pole arrangement, 67W and 39W luminaires for M4 street lighting classes with one sided pole arrangement, 73W and 39W luminaires for M3 street lighting classes with two sided opposite arrangement and 2x73W and 2x46W luminaires for M3 street lighting classes with double davit median arrangement have been selected in order to compare maximum and minimum pole spacing scenarios. As a result of HOMER simulations; battery-PV sizes and PV tilt angles have been determined due to the loads which operates at the time of street lighting. Values such as initial costs, maintenance&operation costs, the total net present costs, costs of energy, amount of energy productions and consumptions, autonomy, CO2 mitigations etc. have been determined over the simulations. In the study, the lowest costs of energy have been found in Antalya among the seven provinces. Antalya is followed by İzmir, Van, Gaziantep, Ankara, Samsun and Istanbul respectively. It has been seen that the usage of high powered luminaires in the systems decreases the costs of energy. However, in the cases except Antalya and İzmir, this situation reverses after certain luminaire load levels which is related with the maximum PV panel capacity that can be used in stand alone solar lighting. Considering PV capacity that can be mounted on a lighting pole is limited, maximum PV capacity is taken as 1 kW in this study. While in Antalya and İzmir systems did not need to exceed the maximum PV capacity, in other provinces the maximum PV capacity became insufficient after certain load levels for the sunshine and solar irradiation characteristics of those provinces and systems which could not increase their PV capacities anymore, increased their battery sizes instead which were more costly. As a result of the study, it has been seen that the investment of stand alone solar LED street lighting systems will not be economically feasible for any geographical regions of Turkey in the current situation and the payback period of the systems can not reach below the system life of 20 years. Minimum payback period has been reached in the current situation is 27,82 years in Antalya among the seven provinces. In case of increase in electricity unit prices and decrease in photovoltaic panel and battery costs, payback period can be reduced to 12,37 years. Dimming control has been applied for the system with the lowest payback period in the current sitation. It has been seen that by dimming, total net present cost of the battery + PV for a single pole system decreases by %22 from 1933 $ to 1506 $. System installation cost for 1 km decreases by %14 from 62526 $ to 53559 $. For a single pole system, cost of energy production due to battery and photovoltaic panel decreases from 0,225 $/kWh to 0,210 $. In the case of dimming, the LED luminaires which are in operation for 3961,16 hours in a year operate 2183,91 hours with reduced power (51,5W) and 1777,26 hours with full power (73W). The annual electricity consumption per kilometer decreases by %16,5 from 12144,95 kWh to 10136,19 kWh. By dimming, the current payback period of the system reduces from 27,82 years to 26,38 years. In the case of %25 increase in electricity unit prices payback period of the system would reduce from 22,25 years to 21,10 years. In the case of %25 decrease in PV+battery prices payback period of the system would reduce from 21,61 to 20,70 years. In the case of %50 decrease in PV+battery prices payback period of the system would reduce from 15,46 to 15,04 years. In the case of %25 increase in electricity unit prices with %50 decrease in PV+battery prices payback period of the system would reduce from 12,37 to 12,03 years. In the study, it has been seen that stand alone solar LED street lighting systems can not payback themselves in the current situation. Battery and PV sizing were made according to the lowest irradiaton and sunshine durations during winter months in order to meet street lighting criteria even in the worst conditions which led to increase in the cost of the systems. Thus, most of the electricity produced is not consumed. Nonetheless, these systems can be less costly than on-grid systems if they are installed in rural areas where the grid electricity is not reachable and new transmission lines are required to energize the street lighting systems. The systems also have benefits such as contributing to the reduction of CO2 emissions, increasing awareness of environmental and sustainable policies and supporting studies and experimentations on solar lighting.