Low-emission vehicles: the advantages in heavy transport

Low-emission vehicles

The topic of low-emission vehicles is no longer confined to the automobile industry. Indeed, in recent years, the discussion has spread like wildfire to also concern heavy-duty vehicles, a sector that has become the subject of numerous directives in more and more countries around the world in the interest of reducing pollutant emissions. 

In the European Union alone, trucks, buses and coaches are responsible for more than a quarter of greenhouse gas emissions from road transport and over 6% of total greenhouse gas emissions (1).

We already have the technologies to curb the impact of heavy vehicles on our environment—namely the use of alternative fuels, the implementation of more efficient engines, and electrification. Indeed, there are many avenues that can be pursued. Among these, cost-effective and high-potential photovoltaics should certainly be mentioned, being able to provide additional clean energy from an inexhaustible source that is the sun. 

A solution that can combine environmental and economic benefits.

Technologies adopted to reduce emissions in heavy-duty vehicles

Heavy transport is a key pillar in global economies, but its environmental impact is significant due to high emissions of greenhouse gases and pollutants. To address this challenge, the transportation industry is increasingly moving towards adopting technologies to develop low-emission vehicles, focusing on innovative solutions to reduce pollution and promote greater sustainability. As reported following the recent study carried out by the International Council on Clean Transportation (ICCT) in “A Comparison of The Life-Cycle Greenhouse Gas Emissions of European Heavy-Duty Vehicles and Fuels” (2), these solutions count on hydrogen, natural gas, and Battery Electric Vehicles (BEVs). 

  • Hydrogen vehicles

Fuel cell electric trucks and buses powered by hydrogen produced from fossil fuels reduce greenhouse gas emissions by 15% to 33% compared to their diesel counterparts. Reducing emissions depends largely on the source of the hydrogen, which today is produced mainly from natural gas. With hydrogen garnered exclusively from renewable electricity, emissions drop by up to 89%.

  • Natural gas, biomethane, electrofuel vehicles

At best, natural gas vehicles marginally reduce GHG emissions in comparison with heavy-duty diesel vehicles. If short-term Global Warming Potential (GWP) for natural gas is utilized, the climate impact of natural gas HDVs is even greater than that of diesel vehicles. For natural gas trucks and buses sold in 2021, the ICCT estimates a lifetime emissions reduction of 4% to 18% compared to their diesel counterparts.

  • Battery-operated electric vehicles

Battery electric trucks and buses outperform their diesel, hydrogen, and natural gas counterparts in reducing Greenhouse Gas Emissions. The 2021 vehicle models produce at least 63% less in emissions throughout their lifetime compared to diesel versions. Emissions are projected to be reduced by 92% when using 100% electricity from renewable sources.

When we talk about innovative technologies, mention must be made of those aimed at extending range. In fact, unlike cars, trucks offer large surfaces that can be exploited to generate additional energy. 

The spaces available on trailers, trucks, coaches, and buses lend themselves well to the integration of solar power systems that ensure the production of clean energy that can meet the energy needs of auxiliary services, as potential solar farms on the move. 

Indeed, it is good to remember that trailers also have important services that need power—one of the most energy-intensive being the cooling system, for example, which is often characterized by obsolete and highly-polluting refrigeration units that invalidate the efforts made by manufacturers to achieve low-emission vehicles.

To overcome this problem, solar energy can be harnessed by creating a system consisting of panels together with a battery that collects solar energy to then be redistributed in the form of electricity in a programmed manner, with appreciable long-term benefits in terms of reduced emissions and cost savings. 

Technologies for refrigerated trucks

Refrigerated trucks are designed to achieve temperatures ranging from +7° C to 0° C, to even -18° C or below, as required by frozen products. Reaching these temperatures involves a distinctly high energy expenditure, which in most cases is sustained by dated diesel engines that are not subject to any emissions regulations.

In Europe, emissions from non-road mobile machinery, which precisely includes refrigeration units, have only been regulated since January 2019 with the entry into force of the new 2016/1628 regulations. In most cases, the numerous Transport Refrigeration Units (TRUs) in circulation are pre-2019.

Research conducted in 2018 in the UK alone helps us understand the implications of such a scenario, equating the emissions from the refrigeration systems of the 34,000 refrigerated trucks on UK roads with that of 1,800,000 Euro 6 diesel cars (3)

The road to low- and zero-emission vehicles is thus leading manufacturers and fleet owners to implement less-polluting solutions in this field as well, with the use of all-electric, hybrid-electric, or standby-electric TRUs (eTRUs), taking advantage of hydrogen fuel cell technology or availing of cryogenic systems, as well as analyzing useful solutions to extend the range of refrigeration units such as regenerative braking and solar assist (4).

Focusing on the latter case, the energy produced by photovoltaics can prolong the operation of a battery-electric TRU by reducing its recharging frequency and duration.

The solar panels used in this type of application utilize high-efficiency monocrystalline silicon cells encapsulated in flexible mounts that can withstand the vibrations and mechanical stresses typical of mobility.

These photovoltaic modules are mounted on the roof of the trailer, with a charge controller being responsible for optimizing the power coming from the panels and managing the delivery of electricity to the battery pack. 

Photovoltaic power generation is subject to the influence of various factors, including sunlight intensity, irradiation duration, temperature, and possible shading. Nonetheless, significant advances in technology have led to the development of extremely efficient photovoltaic cells and solar power systems capable of generating considerable power even when space is limited. The presence of solar panels also offers benefits related to the use of batteries, which undergo fewer deep discharges and power surges as a result, meaning longer life cycles. This in turn reduces maintenance costs and even allows battery replacement costs to be spread over a longer time frame.

Zero or Low-emissions vehicles?

A future shift from low to zero emissions in heavy transport is by no means idealistic, especially considering the many solutions seen to date. Combining different technologies seems to be the most promising way to achieve significant results not only for traction but also for powering important services involved in refrigerated transport.

For example, by combining a Solbian flexible solar panel system fitted only to the roof of the trailer with the electric axle, a refrigeration system totally independent of diesel generators and fossil fuels can be achieved.

This result is potentially achievable even just with photovoltaics by extending the application to the sides of the trailer plus connection to a suitably sized battery. This configuration could power a full electric refrigeration system. 

These are two examples of how the benefits of solar power can already be harnessed in heavy transport. Still, there are multiple international case studies, which we have collated in this very in-depth e-book on transforming trucking fleets into sustainable fleets.

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Flexible photovoltaic panels: Examples of application

State-of-the-art technology applied to road transport and other vehicles.


  1. European Commission (2023). Reducing CO₂ Emissions from Heavy-Duty Vehicles (https://climate.ec.europa.eu/eu-action/transport-emissions/road-transport-reducing-co2-emissions-vehicles/reducing-co2-emissions-heavy-duty-vehicles_it)
  2. International Council on Clean Transportation. Adrian O’Connell, Nikita Pavlenko, Georg Bieker, Stephanie Searle (February 2023). A Comparison of the Life-Cycle Greenhouse Gas Emissions of European Heavy-Duty Vehicles and Fuels (https://theicct.org/wp-content/uploads/2023/02/lca-ghg-emissions-hdv-fuels-europe-feb23.pdf)
  3. Auto Express/Hugo Griffiths (September 2018). Exclusive: UK Refrigerated Truck Emissions Equal to 1.8 million Cars (https://www.autoexpress.co.uk/car-news/104582/exclusive-uk-refrigerated-truck-emissions-equal-to-18-million-cars)
  4. California Air Resources Board (October 2022). 2022 Technology Assessment: Non-Truck Transport Refrigeration Units (TRU). Trailer TRUs, Domestic Shipping Container TRUs, Railcar TRUs, and TRU Generator Sets (https://ww2.arb.ca.gov/sites/default/files/2022-10/CARB%202022%20TRU%20Technology%20Assessment%2010-14-22.pdf)

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