Photovoltaic and Energy Storage Design for Auxiliary Loads of Electric Light Weight Train: Case of Addis Ababa Light Rail Transit

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Addis Ababa University


In recent decades, the world has turned its attention to renewable energy supply in an attempt to fight climate change and global warming. While renewable energy provides a cleaner and less expensive energy source, it is critical to assess the possibility of installing of solar PV systems with storage on electrical rail vehicles. In many developing countries, the reliable access to electricity is still a big challenge and about 55.7% of Ethiopians still have no access to the national electric grid or any other significant electricity source according to published studies. Some of the population depend on dry-cell batteries, or off-grid electrical energy supply which does not cater enough for ancillary services or basic energy needs. On the other hand, a total number of 41 train vehicles operate daily on the two lines namely E-W line and N-S line of the AALRT and consume a huge amount of energy that is entirely drawn from the national grid. Part of this energy goes to the auxiliary power supply unit to feed some AC and DC loads onboard of rail vehicle such as those that are captious to its effective and safe operation. A portion of this energy could be saved and used to supply some of the Ethiopians who have no access to electricity at all. This research proposes a strategy of onboard auxiliary supply system of light weight train using photovoltaic and battery energy storages. The structure proposed here is to install the solar panels on the train’s roof with onboard batteries. Data were collected, and an in-depth analysis was performed to assess the possibility of supplying them using roof-top PV and battery storages in the case of AALRT. A demand-supply analysis was carried out in this study to compute the system availability and reliability. Accordingly, the PV system was optimally sized along with a battery control strategy. The study included details on MPPT algorithm, and energy management strategy of system. Results of the study prove that a combination of PV system with existing onboard batteries can help to save 3.33MWh daily. It has been demonstrated that the system would return the investment within 20 months through the payback period approach. Shading analysis of the proposed PV system has also been carried out for two identified locations with potential shadow-cast building and it has shown that only 0.8% and 1.3% for case 1 and case 2, can be lost. This loss is negligible for since we considered the worst-case scenario. The availability of regenerative energy has also been briefly analyzed and the performance of the designed system has been evaluated.



Energy Storage Design, Auxiliary Loads, Electric Light Weight Train, Addis Ababa Light Rail Transit