en.Wedoany.com Reported - A Bangladeshi research team has conducted a technical and economic modeling study of rooftop solar photovoltaic systems along the MRT Line 6 of the Dhaka Metro. The results indicate that building a 20.38 MW solar PV system can effectively meet auxiliary power demands and generate favorable financial returns.
As Bangladesh's first metro line, MRT Line 6 spans 21.26 kilometers and commenced commercial operations at the end of 2022. The line is elevated, connecting Uttara North station in northern Dhaka to Motijheel station in the south, with 16 stations along the route.
The study employed two complementary simulation methods: high-resolution station-by-station technical modeling of all 16 stations and 5 depot facilities using PVsyst software, and techno-economic optimization of a PV-grid-battery hybrid system using HOMER Pro software. Corresponding author Rahat Redwan stated that this is the first time detailed station-level PV design has been combined with zone-based hybrid optimization, incorporating a comprehensive sensitivity analysis for a South Asian metro system.
Redwan noted that the team plans to advance subsequent research in multiple directions, including adopting actual load measurement data from operational stations to replace the currently assumed operating schedules, and exploring PV integration options for trackside and elevated guideways, while conducting in-depth techno-economic comparisons of battery chemistries and secondary battery options for metro applications.
In the PVsyst modeling, the team evaluated all 16 elevated stations and 5 depot buildings within the Diabari depot in Uttara, northern Dhaka. After deducting transparent roof areas and reserving a 10% area loss, the total usable rooftop area was determined to be 250,469.61 square meters, including 60,347 square meters for stations and 67,052.8 square meters for selected depot buildings. The modeling used commercially available 595-watt monocrystalline PV modules and simulated module orientation, inverter configuration, shading effects, and system losses to estimate annual energy generation, performance ratio, and overall system efficiency.
The simulation input the Dhaka Rasha specific meteorological dataset, covering parameters such as global horizontal irradiance, direct normal irradiance, diffuse horizontal irradiance, ambient temperature, relative humidity, wind speed, and Linke turbidity. The system was designed as grid-connected, equipped with a lithium iron phosphate (LiFePO₄) battery energy storage system, supporting bidirectional power flow, prioritizing self-consumption, with surplus electricity fed into the national grid under a feed-in tariff model. The project lifecycle assumes an annual PV module degradation rate of 2%.
The modeling ultimately determined a total capacity of 20.38 MW PV system distributed across 21 sites (16 stations and 5 depot buildings), generating over 25.5 GWh annually. The system can offset a significant portion of the metro's auxiliary power demand and reduce approximately 235,297 tons of CO₂ emissions over a 20-year operational period, delivering substantial environmental benefits.
Redwan expressed surprise at the strong economics in the public transit sector: the project has a payback period of six years, a return on investment of 234.1%, a net present value of $20.05 million, and the entire project is fully funded by equity without debt financing.
The study further conducted zone-based optimization using HOMER Pro, dividing the metro corridor into three zones: Zone A (Uttara), Zone B (Agargaon, Shewrapara, Kazipara), and Zone C (Motijheel, University of Dhaka, Secretariat). This zoning approach allowed system design to be locally adjusted based on specific load distribution and environmental conditions in each zone. Among them, Zone B was the most cost-effective, with a net present value of $1.63 million and a levelized cost of electricity between $0.063/kWh and $0.125/kWh. Zone C had slightly higher costs but achieved the highest emission reductions due to its stronger renewable energy integration capability.
Redwan added that although Zone C was not equipped with battery storage and relied entirely on PV-grid interaction, it still achieved a renewable energy share of up to 70%, exhibiting the best emission performance among the three zones. Sensitivity analysis revealed a strong interaction between grid buyback tariffs and solar irradiance, jointly determining whether configurations with or without batteries are more optimal, and small tariff changes could completely alter the preferred system architecture.
The related research findings were published in the journal Energy Reports under the title "Towards sustainable urban transit: Design of a solar-powered metro rail system." Researchers from Ahsanullah University of Science and Technology (AUST), European University of Bangladesh, Bangladesh University of Business and Technology (BUBT), Rajshahi University of Engineering and Technology, and the Military Institute of Science and Technology in Bangladesh jointly participated in this work.
