Several manufacturers have explored equipping their vehicles with solar panels. Initially, this seems logical; while the car is parked, you can gain extra range without any direct costs, using clean energy that benefits the environment. Additionally, fewer trips to charging stations sound convenient. However, the reality isn't as simple as it appears upon closer inspection. Let's delve into the details.
Understanding Solar Panel Functionality
While we won't delve too deeply into technicalities, it's crucial to note a few practical aspects of having solar panels on a vehicle. The nominal power output of solar panels is often expressed in watt-peak (Wp), indicating the output under optimal conditions—full sun exposure and ideal temperature.
In practical situations, however, the output is typically less than nominal due to factors such as temperature. Each solar panel comes with a temperature coefficient—ranging from 0.2% to 0.5%—which signifies output loss for every degree above 25°C. For example, a panel exposed to direct sunlight in southern Europe can exceed 65°C, resulting in an output degradation of 8% to 20%.
Shade also significantly impacts solar panels. Panels are usually connected in series, meaning that if even a small portion of a cell is shaded, the output of the entire panel can drop dramatically. A shaded row often results in a complete loss of output. If multiple panels share the same inverter—which is common due to cost-saving measures—a single underperforming panel can lower the efficiency of the entire system.
These issues necessitate careful planning for traditional solar panel installations, where positioning and angling are strategically considered to minimize shading. However, with solar panels mounted on cars, these favorable conditions are virtually nonexistent. Cars are often parked near buildings or other vehicles, resulting in a significant reduction in electricity generation.
Now, let’s explore the core arguments against solar panels on cars.
Not as Economical as It Seems
The solar roofs offered by Hyundai on certain models and Toyota on the Prius are priced around €1,500 to €2,500, depending on the market. For instance, the Hyundai solar roof has a nominal output of 204Wp, while the latest Prius model provides a mere 60Wp, insufficient for battery charging and only capable of powering some ancillary systems.
According to a map from Global Solar Atlas, the expected annual yield from solar panels varies significantly based on location. In Gibraltar, optimally positioned panels can yield about 1,550Wh for every watt-peak installed. If laid flat—as on most car roofs—this yield drops to around 1,400Wh. In London, the yield is only 820Wh, and these figures do not account for shading losses.
Under optimal scenarios, the Hyundai solar roof could generate 280kWh annually. However, this number drops to just 164kWh in London, without factoring in additional energy required for cabin cooling due to parking in direct sunlight. At commercial charging station rates of €0.50 per kWh, it would take 10 to 20 years just to break even, not factoring in other issues that further reduce output efficiency.
Moreover, vehicles like the Lightyear 0 offer more solar panel coverage, but the company has yet to disclose exact output numbers. They project an additional yield of 11,000 km in sunny regions, which assumes optimal placement away from shadows. Such estimates yield around €528 in energy savings when measured against the cost, dropping to €265 in less sunny areas like Glasgow.
Although Lightyear has plans for cheaper models and other companies like Sonos are exploring more accessible solar vehicles, past promises do not guarantee successful production. Doubt surrounds the feasibility of making solar cars practical within the next decade.
Environmental Concerns
While it may seem beneficial to produce clean energy, the reality is more complex. The rapid rise in solar energy adoption is constrained by production limitations; the capacity to manufacture solar panels is insufficient. In a market where supply is limited, it is more prudent to allocate production resources to solar farms, where panels can be positioned for optimal performance, rather than on vehicles.
The complexity increases with smaller installations, which do not benefit from economies of scale. This often results in a higher carbon footprint per watt-hour produced.
Questioning Convenience
While convenience is subjective, the presence of solar panels on cars introduces several complications. The aesthetics of solar panels may not match the sleek lines of modern vehicle designs. Additionally, parking becomes a consideration; optimizing the power output potential requires parking in optimal locations.
Furthermore, the efficiency of solar panels will diminish with dust accumulation, necessitating regular cleaning. In winter conditions, solar panels generate significantly less power—roughly one-third of what is possible during summer months. For instance, in ideal situations, a vehicle such as the Ioniq 5 may only gain 1.5 kilometers of extra range per day in winter.
Considerations like the wish for sunroofs, roof rails, or rooftop storage boxes complicate designs with solar panels, as they often conflict with functionality. Repairing damages is also more challenging, as solar panels are fragile compared to traditional roofs and require specialized replacement—making them harder to source.
In the case of vehicles like the Lightyear 2 or Sonos Sion, sacrifices include a reduction in design features, such as the absence of rear windows, which may deter potential buyers.
Alternative Solutions
For the cost of a solar roof on a Hyundai, one could invest in a small solar installation at home that could generate significantly more renewable electricity. For those wishing to integrate solar energy into their vehicles, options exist. Enhancing your home charging station may lead to faster charging rates, or improving vehicle efficiency through better tires and wheels could yield better results.
Depending on location, purchasing more electricity from renewable sources is a viable alternative. The potential savings from not opting for unnecessary car features can contribute to utilizing greener energy sources as they become more accessible.
In the future, when solar panel technology has advanced, and supply levels meet or exceed demand, revisiting the idea of solar-equipped vehicles might be feasible. That, however, is likely decades away.
