Solar energy: shining example of auxiliary power for commercial vehicles

Solar panel technology is developing quickly and can provide an option for powering auxiliary equipment in commercial vehicles and is likely to become increasingly important as take-up of electric vehicles increases.

Like many logistics providers, McCulla (Ireland) Ltd is looking for ways of reducing their carbon footprint, as well as maintaining their bottom line.

The Northern Irish company has taken several measures to that end recently, including investing in Iveco Stralis NP trucks, which are fuelled with biomethane gas produced by McCulla’s own anaerobic digester plant. In June, the company also invested in 25 Schmitz Cargobull S.KO COOL SMART refrigerated semi-trailers with Carrier Transicold Vector HE 19 units, fitted with specialised solar panels designed for use on vehicles, supplied by fleet technology specialist Genie Insights. The solar panels keep fridge batteries topped up to avoid breakdowns and to prolong the battery’s life.

The Genie panels use thin film solar cell technology, known as CIGS – standing for Copper Indium Gallium Selenide – that allows the manufacture of robust and flexible photovoltaic (PV) panels which are better suited to use on vehicles than traditional glass solar panels.

“At McCulla we have made a strong commitment to the environment and the arrival of these new trailers represents a further important step in the reduction of our carbon footprint,” says Brian Beattie, McCulla’s operations director. “Crucially, the solar panels prolong battery life and improve battery reliability, so they save us downtime and money.”

New technology

The solar panels fitted by Genie Insights come from a core technology and manufacturing process initially developed by a joint R&D collaboration between industry (Tata Steel), academia (Swansea University) and with support from the Welsh Government, according to Billy Dougan from Genie Insights.

“The panels have been used successfully in the construction sector for a number of years and the manufacturer, Newport-based MiPV, has had some success in the leisure and blue light sectors,” Dougan adds. “In 2020, Genie Insights initiated a partnership with MiPV to develop a product specifically for the temperature-controlled commercial trailer market.”

The solar panels developed are more suited to commercial vehicles than traditional solar panels that have been manufactured using glass or silicon. “Neither of which are well suited to commercial vehicles because they are too easily damaged for mobile applications and don’t typically perform well enough,” says Dougan.

“Our photovoltaic solution uses CIGS technology, which is flexible, robust and highly efficient. CIGS panels are just 3mm thick (bonded) and extremely lightweight, plus they can ‘flex’ with the contour of the vehicle body. This means there is no drag or effect on payload and because they sit flush with the vehicle roof, are much less susceptible to damage than traditional panels that typically require a mounting frame.”

The solution also requires almost zero maintenance once installed, Dougan adds. “They have a truck wash friendly EFTE non-stick topcoat, similar to Teflon, which means they remain clean, weatherproof and maintenance-free.”

Modular solution

The flexible solution is designed to be modular, and Genie Insights can manufacture more than 140 different sizes ranging from 40w to 360w and with panel lengths up to 5m long. “This, coupled with the ability to carry out accurate computer modelling, means solutions can be completely tailored to ensure optimal performance,” says Dougan. “It is important at the initial consultation stage with customers to fully analyse their electrical draw so that the solution does not over- or under-perform. Ideally, we want it to perform well in winter but not generate significantly more power than it needs in summer. 

“Our high efficiency 50w panel for refrigerated trailers could be considered ‘one-size-fits-all’ because the research and modelling has now been done for this application.”

The time it takes to produce a custom panel depends on the complexity of the application, Dougan adds. “We first need to ascertain the amount of draw that the vehicle’s ancillary equipment is taking from the battery, which tells us how much wattage of solar we need to maintain a healthy battery state or to power the equipment, depending on the objective.

“In some cases, we look beyond the solar panel and work with other key partners to deliver a full system including lithium battery combinations and/or ‘smart’ charge controllers, for example. 

“If a solution hasn’t been modelled previously, the analysis, development and testing phase can take as little as a few months but ideally, we prefer a solution to be tested during a real-life winter before rolling out to the remainder of a fleet.”

Challenging perceptions

Genie Insights’ solution also addresses one of the traditional criticisms of solar power – that it won’t get enough sunlight to work properly, given the propensity for rain and cloud in the UK. “There is a negative legacy perception from older solar technology, which just didn’t perform for commercial vehicles,” admits Dougan.

However, by using CIGS, the modules absorb light up to 100 times more effectively than conventional materials and they start producing energy earlier in the morning and continue for longer in the evening than traditional solutions, Dougan adds.

“In addition, most solar panels only contain three bypass diodes which significantly limits performance in shaded or cloudy conditions. If one cell is shaded, total power reduces by one-third. In contrast, our product incorporates bypass diodes in every other cell so if a pair of cells is shaded, the current is able to move to the next cell. The only performance loss, therefore, is from the shaded cells. This means our panels will work efficiently in less favourable conditions including low light, shading from buildings, cloudy days and if partially damaged or covered, for example, by snow or bird droppings.

“When we are developing a product for a customer, we run performance tests on computer modelling software and these are carried out based on an average winter in Scotland. Typically, if the panel performs efficiently under modelling tests, it has been proven to outperform modelling in real-life.  We have completed many successful, real-life trials over the course of the 2020 and 2021 British winters and during operation in the highlands of Scotland.”


Solar panels can also bring savings to operators, although not always for the primary intended reason, Dougan adds. “While solar panels on commercial vehicles have been shown to deliver significant fuel savings, this is a bonus in some applications rather than the primary reason for installing them,” he says. “Genie Insights believes the greatest benefits come from improvements in battery performance and reliability. Solar panels keep batteries charged which reduces battery degradation to improve battery health and longevity.

“By ensuring that the battery is continually trickle-charged, the length of time the fridge alternator needs to run is reduced. This will result in reduced fuel consumption, but the real savings are made from reduced breakdown and callout costs, reduced late delivery fees due to battery-related breakdowns and reduced battery replacement costs, alongside the marginal fuel cost reduction.

“Some of our customers have been spending tens of thousands of pounds on battery-related issues each year so the return on investment is fairly instantaneous.

“Having said that, we are currently working on some projects that aim to provide an autonomous power supply via solar so in these applications, fuel saving will key.”

Tech alliance

UK-Swedish transport refrigeration provider Hultsteins was another trailer manufacturer to partner with a transport solar power provider recently, in this case Trailar, to facilitate a ‘free-at-the-point-of-use’ solution for users of their sustainable fridge systems.

The technological alliance will provide operators with permanent savings on fuel, maintenance and emissions – areas of key focus for operators needing to adapt to the environmental challenges which lie ahead, according to the companies.

“Our hydraulic-drive fridge systems draw a small amount of energy from the truck via an engine-mounted PTO,” says Graham Usher, who looks after Hultsteins sales in the UK and Ireland. “But despite the very small amount of fuel required for this, Hultsteins systems achieve diesel savings of around 80 to 90%, in comparison to a diesel TRU.”

Usher explains that the solar energy captured is fed into the vehicle, which then reduces the energy required by the engine to run the fridge system. This process more than compensates for the small amount of diesel the fridge requires via the PTO.

Adam Buckley-Mayes, principal sales engineer and head of customer operations at Trailar adds: “This is a really exciting collaboration where together, we can bring a truly diesel free refrigeration unit to the market. This means that customers can gain a huge amount of savings on their fuel and maintenance spend whilst also doing their bit in the fight against carbon emissions and creating a greener planet.”

“The solution is designed, manufactured and assembled in Manchester and includes the first specifically designed solar controller for transport. Typically, solar solutions will provide a maintenance charge to batteries to ensure they are kept at optimal health. This is a third benefit within the Trailar solution, with the first and second being the fuel and CO2 savings, and the operational insights gained from the units telematics and our unique customer portal. We utilise leading solar matting (CIGs) and solar controller (MPPT) technology alongside our 4G telematics device to deliver the solution.”

According to Hultsteins, a typical Trailar system for a rigid vehicle saves about 600 litres a year, while a Hultsteins fridge only requires an average of 250-300 litres running 1,500 hours per year, during road use. The combination of a Hultsteins fridge connected to a solar system, dramatically reduces annual diesel usage, cuts running costs by a significant margin and reduces emission pollution.

The system is also designed to be simple, and with a ‘plug and play’ approach, installation times are quick. At the heart of this is the Smart Charge Controller, which is designed specifically for logistic applications and regulates the transfer of energy from the alternator and solar matts to the vehicle battery.

Special sensors monitor all electrical characteristics, allowing for fuel and CO2 savings to be calculated. Savings which, say Trailar, enable rigid operators to see a return on investment in under 18 months.

Data analysis

Trailar’s head of marketing, Matthew Summers, adds that Trailar’s technology means each of its systems allow customers access to telematics data. “Customers will access this data using the Trailar Insights web-platform, where they will be able to see asset utilisation, live and historic GPS tracking, battery health reporting, tail-lift counts plus fuel and CO2 saving figures,” he explains.

Using Internet of Things cloud technology, millions of data points are automatically collated and analysed from fleets around the globe. The data is viewable in the web platform, as well as being able to be exported, to enable further offline analysis with other datasets.

Another benefit of utilising cloud technology is that it allows Trailar to provide over-the-air updates to the system, minimising the need for any physical servicing. Battery health reporting is also detailed enough to enable operators to proactively schedule battery replacements, removing unplanned downtime from operations.

“As an ex-operator, most carbon-reducing or green technologies aren’t commercially viable for a lot of businesses,” Summers says. “The benefit of having a simple solution that pays for itself and more, provides fuel savings without having to manage driver performance, as well as significantly improving battery life is invaluable. The telematics then goes a step further, giving the operator valuable and actionable information.”

OEM potential

OEMS are also scoping out the potential of solar power. For instance, in May, truck manufacturer MAN Truck & Bus and Sono Motors signed a Letter of Intent agreeing to investigate the technical and economic feasibility of integrating Sono’s solar technology into MAN’s eTGE electric transporter.

Three applications are to be equipped with Sono Solar technology and investigated by the companies: MAN’s eTGE panel van, eTGE combi with a powerful on-roof air conditioning system and the eTGE with a refrigeration system.

The spokesperson said that both parties soon expect to have a clear picture of which of these cases are not only sustainable, but economically viable as well. “The companies are currently aligning on the different use cases and certain detailed technical requirements,” they said. “We hope to start the first joint project in the coming months, depending on resources from both sides.”

Sono Motors sees great potential across many sectors for solar power, the spokesperson adds. “Following the passenger vehicle trend, this decade is the decade of electrification within the commercial vehicle industry,” they said. “Through our solar-integrated products, we expect to provide our customers within this segment with a great total cost of ownership (TCO). We also aim to reduce their dependence upon the charging infrastructure.”

Of course, different applications take up varying amount of energy, depending on their use. “Certain things have to be taken into consideration, such as temperature, trailer size and the amount of doors opened throughout a delivery route, for example. Additionally, there is the issue of potential effects on the vehicle’s range when diesel generators used for cooling, for example, are replaced with electric counterparts. This solution consumes additional energy from the main high voltage (HV) battery.

Sono Motors sees potential applications for solar power for powering auxiliary elements and extending a vehicle’s range. “We see the market making a huge shift towards electric vehicles, regardless of their size,” the spokesperson said. “Auxiliary systems, for example, need to take power from the HV battery which has a tremendous effect on the vehicle’s range. Solar integration has the potential, however, to extend the vehicle’s range, offsetting these effects.

Solar power also has potential applications on rigid trucks and trailers, the spokesperson added. “First of all, the area of both the roof and the sides creates large space and opportunity for solar integration,” they say. “This can then be used to cover a large proportion of the energy needed for electric cooling units or other energy intensive applications.

“Second of all, those types of large vehicles are mostly exposed to a large amount of sunlight on motorways or large car parks, for example, which makes them ideal for solar applications. Finally, long-haul trailers face additionally large energy consumption when transporting goods that need to be refrigerated.

Future for solar

Solar energy could become mainstream for operators in years to come, the spokesperson adds. “Solar energy is already one of the cheapest forms of energy at €0.05 per kWh,” they say. “Furthermore, our technology can provide our customers with outstanding TCO and help them overcome hurdles such as missing charging infrastructure on highways and logistics hubs. Sono Motors is at the forefront of vehicle integrated photovoltaics and is confident about shaping the future of sustainable transportation.”

Buckley-Mayes agrees: “Solar can have a hugely positive impact in the move over to electric vehicles,” he says. “Not only does the harnessed energy aid the range of the vehicle, but the influence it can have on the grid charging capacity when the vehicles are back at the depot can be massive. Particularly with our unique solar controller, the system operates in the same way as on the diesel vehicles. By pushing the solar energy into the vehicle first, we reduce the load on the main vehicle battery. Other standard solar solutions would again only provide a maintenance charge and would not gain the benefits of range extension.

“More and more ancillary equipment is being placed onto vehicles which all require a source of power. As we move into alternative fuels, all available technology will need to be brought together to ensure we can keep all our comforts and get the most out of our vehicles, while also driving to reduce emissions. Solar has a big part to play in this, especially as the technology evolves and the cells become more efficient.”

Dan Parton
Dan Parton
Dan Parton is a former editor of Truck & Driver, the UK’s biggest selling truck magazine. He is now writes for The Van Expert and The Truck Expert.

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