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A research team led by Professor Eric Cheng from the Department of Electrical and Electronic Engineering at Hong Kong Polytechnic University (PolyU) has been supported by the “Innovation and Technology Support Programme (Mid-stream, theme-based)” funded by the Innovation and Technology Fund of the Innovation and Technology Commission of the HKSAR Government. The project, titled “Smart Refrigeration Truck Development Programme – Power, Solar and Intelligence Method for Logistics and Storage,” aims to transition freezer trucks from traditional fuel-driven systems to smart electric systems and promote the adoption of solar energy.
The transport sector significantly contributes to greenhouse gas emissions in Hong Kong, accounting for 19% of the total. The development of green transport is crucial for reducing air pollutant emissions. PolyU is dedicated to promoting research into green technologies to support Hong Kong’s goal of halving its total carbon emissions from the 2005 level by 2035 and achieving carbon neutrality before 2050.
The PolyU team has successfully developed an innovative freezer truck featuring a solar-powered freezer system and vehicle-connected power storage and sharing technology. This project has garnered support from the government, academia, and industry, including Sunlight Eco-tech Limited, Advanced Sunlight Pty Limited from Australia, and the Electrical and Mechanical Services Department.
Currently, Hong Kong has approximately 5,000 freezer trucks, a number expected to double in the coming years. These vehicles are powered by fuel engines, producing significant exhaust gas and noise. Conventional freezer truck technology is outdated, with the freezer system relying on the vehicle’s internal combustion engine for power, even when stationary. To maintain operation, the engine cannot be turned off, and the system typically maintains a temperature of around -20 degrees Celsius, limiting the types of food that can be refrigerated. Each vehicle consumes one to three litres of diesel per hour, producing 2.7 to 8.1 kg of carbon dioxide, resulting in annual emissions of approximately 16 tonnes. Offsetting these emissions requires planting about 760 trees.
The smart solar-powered freezer truck developed by PolyU offers flexible energy input options, featuring:
- Extensible solar photovoltaic (PV) panels: Installed on the roof, these PV panels can be extended to increase the truck’s power output, enhancing energy efficiency. The truck is equipped with an energy storage device that captures and stores the electric energy generated, providing additional power for the freezer system.
- Onboard lithium-ion battery: Besides solar energy storage, the truck has an onboard lithium-ion battery that can be connected to standard electric vehicle charging facilities for recharging. When the solar energy storage is full and the battery is fully charged, they can power the freezer system for up to four hours. Users can expand the number and capacity of batteries to extend operation time as needed.
- Powerful and versatile freezer system: The onboard refrigeration system can maintain temperatures as low as -45 degrees Celsius and can continue operating even after the electric engine is turned off, effectively transforming the vehicle into a mobile freezer unit. This feature helps address the shortage of freezer warehouses in Hong Kong.
Moreover, the freezer truck can connect to other vehicles of the same type for charging and energy sharing. With the vehicle’s smart energy management system, users can monitor and control the maximum output power of the PV panels, enhancing the efficiency of different energy sources, optimizing freezer performance, and prolonging the onboard battery’s life.
Professor Eric Cheng highlighted the government’s efforts to promote electric vehicles, including a target to cease new registration of fuel-propelled private cars by 2035 or earlier. However, the adoption rate of new energy vehicles for freight is relatively slow. This research project aims to lead the transport sector in embracing green technologies, contributing to reducing emissions and achieving carbon neutrality.
The PolyU smart solar-powered freezer truck is now ready for commercialisation, with expectations that similar vehicles will be launched soon.
