Solar Charging for Public Transport Electric Buses

Dr. Dev Ranjan Daliah Posted on: 2023-10-06 07:10:00 Viewer: 3,234 Comments: 0 Country: India City: New Delhi

Solar Charging for Public Transport Electric Buses

When electric buses (EBs) are charged from the electric grid, the electricity they receive often originates from fossil fuels. This means that while EBs have negligible tailpipe emissions, their overall environmental impact may not be entirely emissions-free. To achieve true decarbonization, EBs must be charged using renewable energy sources.

Renewable energy-based charging stations source their power from renewable sources like solar, wind, hydro, or biomass. These sources can be located near the charging station or connected to the grid from a remote location. Solar photovoltaic (PV) systems have been particularly popular in this application. Solar energy is a clean, emission-free electricity source.

This article explores solar PV systems for EB charging, including their advantages, challenges, the role of battery storage, locational considerations, the need for subsidies from the authorities required for successful implementation in public transportation.

The Solar photovoltaic (PV) system

A solar photovoltaic (PV) system harnesses sunlight to generate electricity. It uses photovoltaic cells, typically made of silicon, to convert sunlight into direct current (DC) electricity. This power can be fed into a depot's electrical grid, reducing the need for electricity from the main power grid.

A solar PV system consists of three main components:

  • Solar panels: These panels absorb sunlight and convert it into DC electricity.
  • Inverters: Inverters change DC electricity into the AC form used in most electrical systems.
  • Mounting structures: These structures hold the solar panels in place and include components like racks, wiring, and connectors.

Intermittency and Mismatch

Bus operators require a consistent and reliable energy source to keep their buses running. A key challenge with solar PV is its intermittency. Solar panels produce electricity only when there is sunlight, making their output dependent on weather conditions and time of day. This means that solar energy production can fluctuate significantly.

Additionally, the timing of bus charging and solar energy production often mismatches. Buses are typically charged at night when there is no sunlight, while solar panels generate maximum power during the day when buses are operating on routes. This mismatch further highlights the need for a storage solution.

A power storage system can help address the intermittency and mismatch issues. By storing excess solar energy generated during peak production times, the system can release it later when buses need to be charged, ensuring a more consistent and reliable power supply.

The Need for Battery Energy Storage Systems (BESS)

To address the intermittency and mismatch issues, a battery storage system is crucial for public transport operators using solar PV systems for electric buses. These systems store surplus solar energy generated during the day and release it when needed, such as during periods of high demand, cloudy weather, or at night. This ensures a consistent energy supply even when solar generation is low.

Battery storage systems offer several advantages:

  • Consistent energy supply: They provide a reliable power source, even when solar generation is low.
  • Grid stability: They reduce strain on the national grid by absorbing excess electricity during periods of high generation and releasing it during periods of high demand.
  • Cost management: By reducing reliance on grid electricity during peak hours, battery storage systems can help manage energy costs.
  • Improved reliability: They provide backup power during disruptions like storms, ensuring uninterrupted bus operations.

In conclusion, battery storage systems are essential for effectively utilizing solar energy to power electric buses. They help overcome the challenges of intermittency and mismatch, ensuring a consistent and reliable energy supply.

Locational Considerations for Solar PV Installations

Solar PV systems are versatile in terms of installation location. For public transport electric buses, solar panels can be installed in various places to maximize space utilization.

Rooftop installations at bus depots and maintenance yards are common choices due to their large, open spaces. In urban areas with limited rooftop space, solar canopies over parking lots can be an effective solution. These canopies not only provide space for solar panels but also offer additional benefits like reducing heat buildup in parked buses, leading to energy savings for air conditioning.

The space needed for a rooftop solar power plant depends on factors like:

  • Roof orientation: The direction the roof faces relative to the sun's movement.
  • Roof shape: The shape of the roof, such as flat or sloped.
  • Solar panel generation capacity: The power output of the solar panels.

As a general guideline, approximately 10-14 square meters of space per kilowatt is required for rooftop solar power plant installations.

Power Output of Solar PV Systems

The power output of a solar PV system is measured in kilowatts (kW) or megawatts (MW), depending on its size. Factors like installation size, location, and sunlight availability influence output.

A Turkish depot (1) equipped with 862 solar panels generated an average of 802.03 kWh of electricity per day. This accounted for 22% of the depot's electric bus charging needs. The solar panels have an average efficiency of 20.6%.

Solar panels installed on rooftops and parking lots at public transport depots can produce 4-5 kWh per square meter per day. These systems can significantly contribute to electric bus charging, especially when combined with battery storage. As a general rule, 10 square meters of solar panels can generate about 1 kilowatt of electricity.

Cost and Investment Aspects

The cost of installing solar PV systems for bus companies varies depending on factors like installation size, location, and the inclusion of battery storage systems.

While specific costs for solar-powered charging stations at bus depots are difficult to find, estimates range from $55,000 to $100,000 (2). Beyond the initial cost, maintenance is minimal, primarily involving regular cleaning and upkeep of the solar panels.

Although upfront costs can be high, the return on investment (ROI) is often achieved within 5-7 years. This is especially true in areas with high electricity prices and favourable solar conditions. Additionally, government subsidies, tax incentives, and grants can reduce the financial burden, making solar PV installations more financially attractive for bus companies.

Subsidy & Incentives

Governments are offering subsidies and incentives to encourage renewable energy use in electric vehicle operations. Some regions provide incentives for installing solar-powered EV charging stations, while others offer tax credits for purchasing charging equipment.

For example, two cities in India received subsidies for solar-powered EV charging stations. These incentives included a capital subsidy of up to 25% of the project cost (3). In the United States, solar investment tax credits (ITC) are available, and commercial entities can also benefit from accelerated depreciation schemes.

Conclusion

Integrating solar PV systems into public transport electric bus operations is a crucial step towards sustainable urban mobility. Solar PV offers a clean, renewable energy source that, when combined with battery storage, provides a reliable and cost-effective way to power electric buses. Although upfront costs may be significant, the long-term benefits – including reduced operational expenses, improved air quality, and energy independence – make solar PV a worthwhile investment for cities seeking to reduce their environmental impact.

By utilizing solar energy, public transport agencies can contribute significantly to the global transition to a low-carbon economy. This ensures that the future of urban mobility is both environmentally friendly and sustainable.





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