Photovoltaic panels on the roof of the car. Researchers study profitability

Published: Updated: Estimated reading time: 5 minutes

The convergence of renewable energy and transportation electrification brings optimism for dependable and environmentally friendly energy sources. Scientists have diligently explored diverse methods to integrate these two elements, ultimately achieving success. An exciting breakthrough entails affixing photovoltaic panels onto car roofs. Yet, the key question remains: Is this investment economically viable? What is the anticipated payback period? And how might this innovation bolster the vehicle’s driving range? These intriguing queries will be further explored in the forthcoming discussion.

A consortium of European scientists embarked on an endeavor to compute electricity generation, the levelized cost of electricity (LCOE), and the period required for investment payback concerning photovoltaic installations integrated into electric vehicles.

What was the research about and who conducted it?

The primary objective of this research was to evaluate the economic viability of permanently integrating photovoltaic panels onto the roofs of electric vehicles, in contrast to utilizing a “follower system” (single-axis) – a mechanism that adjusts the orientation of photovoltaic cells to track the sun’s movement and optimize electricity generation.

This investigation into the profitability of both approaches was undertaken by an international consortium of researchers deeply engrossed in this subject matter. Collaborators from universities in Ukraine, Slovakia, and Latvia united their efforts to conduct this project.

Research assumptions and methodology

The study used a Volkswagen electric car, the e-Golf VII EV series from 2017.

Volkswagen, e-Golf

The researchers established that the available roof space on the vehicle measured 1,468 mm x 1,135 mm. Guided by these dimensions, they posited that the car’s roof could accommodate two 120W solar panels along with a single 50W monocrystalline module, all provided by the Chinese manufacturer Xinpuguang. These three panels were interconnected in a parallel configuration, culminating in a peak power output of 257.92 W.

For the sake of simplification, the study presumed that the car would solely recharge during halts. The analysis factored in data from January, April, July, and October. These findings were subsequently compared against outcomes from vehicle assessments performed under the New European Driving Cycle (NEDC) and the US Environmental Protection Agency (EPA) protocols.

What were the results?

The results revealed that during the month of July, a vehicle-integrated photovoltaic (VIPV) system integrated into the roof could generate 1,587 Wh of electrical energy. This quantity of power would allow a Volkswagen automobile to extend its travel distance by:

  • 7.98 km according to the EPA standard,
  • or 12.64 km in accordance with the NEDC.

This is respectively 3.99% and 6.32% of the maximum travel range when the battery is fully charged.

In January, the permanent VIPV system generated 291 Wh, which means an additional range of 1.55 km (EPA) and 2.32 km (NEDC) – this is respectively 0.77% and 1.16% more than the maximum range.

Volkswagen, e-Golf

Additionally, the study indicated that the sun-tracking system yielded the equivalent energy output as the permanent VIPV system during the summer months. However, the tracking system exhibited superior outcomes in January, April, and October. Its most notable performance was in January, where the tracking mechanism facilitated energy production to enhance the range of the Volkswagen by:

  • 3.01 km according to the EPA standard,
  • or 4.52 km based on the NEDC assessment.

These increments correspond to 1.51% and 2.26% of the maximum achievable driving distance per battery charge, respectively.

Important:

The actual benefits may be less than those foreseen due to the energy used to adjust the roof platform to follow the sun and possible constraints preventing perfect orientation.

When assessing the real value of the increased range using the tracking system, it must be remembered that part of the generated energy is used to adjust the angle of inclination of the photovoltaic modules.

What are the costs of both systems and the payback period?

The researchers conducted an analysis of the Levelized Cost of Electricity (LCOE) and arrived at the following conclusions:

  • The cost of generating electricity from the vehicle-integrated photovoltaic (VIPV) system was approximately USD 0.6654 per kilowatt-hour (kWh).
  • The cost of producing electricity from a single-axis tracking system was about USD 1.1013 per kWh.

In terms of payback time for each system:

  • The VIPV system is projected to achieve payback in 5.32 years.
  • The tracking system is expected to recover its costs in 5.07 years.
electric car charging costs

What do scientists say about these results?

Indeed, while the single-axis tracking system demonstrates a slightly faster payback period, the researchers acknowledge that its installation and operational complexity pose challenges compared to the permanent VIPV system. The inclusion of moving components in equipment introduces a higher potential for mechanical failures. Such failures not only result in additional costs for repairs but can also lead to interruptions in operation, which can significantly impede the system’s overall efficiency and effectiveness. These considerations highlight the trade-offs that need to be considered when choosing between these two solar integration approaches for electric vehicles.

Given the small difference in [payback period], the casual EV driver might be happy with a non-tilt-adjustable system, as the sun-tracking rooftop platform requires a much higher initial investment and is more difficult to install.

Sources:

Sun tracking vs. fixed vehicle-integrated PV, PV magazine

Application of photovoltaic panels in electric vehicles to enhance the range, Heliyon

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