Jaideep Saraswat, Nikhil Mall
The transport sector is the third-highest greenhouse gas (GHG) emitting sector in India. Within this, road transport contributes nearly 90 percent of total emissions, with medium and heavy-duty trucks playing a disproportionate role. Although they make up a small percentage of on-road vehicles, these trucks are responsible for over one-third of total road transport emissions. This makes decarbonising the trucking sector essential for achieving broader transport sector decarbonisation.
Global push for zero-emission trucks
Countries such as China, the US, and those in Europe have made significant strides in deploying zero-emission trucks (ZETs). However, for India, transitioning to ZETs remains a challenge due to high upfront costs and limited driving range. Addressing these issues is crucial to accelerating the electric truck adoption.
Vehicle Integrated Photovoltaics (VIPV) as a game changer
A promising solution to optimise battery packs and extend the driving range of electric trucks is Vehicle Integrated Photovoltaics (VIPV). VIPV is the integration of solar PV modules directly into a vehicle’s structure, such as the roof or bonnet, using lightweight, durable, and often flexible solar technology designed specifically for use on moving vehicles. Unlike passenger EVs, trucks have significant surface area, around 20-25 m2, that can be utilised for energy generation through solar panels. By harnessing solar energy, VIPV enables:
- Extended driving range: Reducing dependence on grid charging by supplementing battery power with solar energy.
- Lower charging costs: Using solar power instead of grid electricity or fossil fuels.
- Fewer charging sessions: Reducing downtime by increasing energy autonomy.
- Improved cabin comfort:– Helps moderate interior temperature, especially in hot summers, reducing air conditioning load.
- Improved battery longevity: Mitigating deep discharges and extending battery life.
- Lower carbon footprint: Enhancing environmental sustainability by reducing fossil fuel reliance.
Barriers to VIPV Adoption
Despite these promising benefits, VIPV face several challenges to widespread adoption. The high initial cost of integrating solar technology into vehicles remains a major barrier. Additionally, complex integration and energy measurement pose further difficulties, particularly in accurately quantifying solar energy generation due to dynamic environmental factors. The lack of standardised energy yield calculations further complicates performance assessment.
Frequent orientation changes while driving impact the effectiveness of solar energy capture, while partial shading from buildings, trees, and traffic infrastructure further reduces power output. Moreover, rapid solar irradiance fluctuations cause millisecond-level variations in energy availability, making energy harvesting inconsistent. Temperature variations between parking and driving conditions also affect PV efficiency and system performance.
From a design perspective, VIPV systems must contend with curved panel surfaces, which introduce energy losses compared to flat, stationary panels, as well as mismatching and cosine losses, where self-shading effects and variations in sunlight angles reduce efficiency in multi-cell configurations. Colour-induced efficiency drops also present challenges, as coloured PV panels experience approximately 10% more energy loss compared to traditional black or dark-blue modules. Furthermore, vibration-related challenges significantly impact VIPV performance. Vehicle vibrations, which can reach frequencies up to 2000 Hz, exceed the tolerance of standard PV modules designed for low-frequency vibrations (0.1–10 Hz). This mismatch leads to structural stress, material fatigue, and potential resonance risks, ultimately affecting the longevity and reliability of the solar cells.
Advancements enabling VIPV adoption
Historically, the integration of photovoltaics into vehicles was hindered by prohibitively high costs for both solar technology and electric vehicles, including their batteries. However, in the past decade, rapid advancements have significantly reduced the cost of photovoltaics, electric vehicles, and lithium-ion batteries, making VIPV a more viable solution.
Additionally, industry efforts, such as the IEC TC82 PT600 working group, are working to establish standardised energy yield calculations, addressing a critical gap in performance assessment. This working group is developing innovative modelling techniques that go beyond simple shading ratios to shading matrix analysis to optimise energy yield by accounting for dynamic shading conditions. 4-Tensor Reflection Models have been developed to improve accuracy by considering complex light interactions on moving, curved vehicle surfaces. Additionally, Local 3D Coordinate Systems enable real-time updates to sun exposure calculations, ensuring precise energy generation assessments for vehicles in motion.
India-specific VIVP research: Vasudha Foundation’s pilot project
Recognising the importance of VIPV for India’s trucking sector, Vasudha Foundation is initiating a pilot project to determine India-specific correction factors for shading, temperature, and panel curvature. This research will help estimate realistic energy generation potential for VIPV-equipped trucks under local operating conditions.
With the right policy support and technological advancements, VIPV can significantly contribute to India’s ZET future. By leveraging solar energy, electric trucks can overcome range anxiety and cost barriers, making them a viable alternative for fleet operators.