energy storage

The Charge to a Greener City: How Skeleton's R&D is Reshaping Public Transport

Future city transport will be autonomous, cost-efficient, with minimal grid impact and emission-free. This vision is taking shape, thanks to our Senior Electrical Engineer Tanel Sinijärv and Software Engineer Fred-Georg Pääro, the driving forces behind Skeleton's ground-breaking engineering R&D project—a supercapacitor-to-supercapacitor fast charging system designed for public transport vehicles.

Tanel and Fred with autonomous bus
Fred-Georg Pääro and Tanel Sinijärv

In 2021, the Estonian Business and Innovation Agency provided essential support for our R&D initiative aimed at developing a supercapacitor-to-supercapacitor fast charging system. Our goal was to create an efficient and cost-effective charging system that could automatically power public transport vehicles within seconds, allowing them to operate seamlessly along their routes with the flexibility to charge at stops. Fast forward to September 2023 and we've achieved remarkable advancements, evolving our technology from a desktop prototype to demonstrator level. 

To bring this project to life, we partnered with Auve Tech, the Estonian autonomous vehicle company that provided one of its shuttle buses. Skeleton developed a supercapacitor-based charging station, integrated supercapacitors into the Auve Tech vehicle and engineered an automated control system for charging through an inverted pantograph.

Autonomous bus and charging station

Tanel, vehicle and charging station.

Power in numbers

The charging station boasts 16 modules rated at 102V each, while the vehicle carries an equal number of 51V modules. This setup enables a peak charging capacity of 600 kW, comparable to the instantaneous energy consumption of approximately 500 U.S. households. 

Drawing such a considerable amount of power directly from the grid to charge the vehicle is unfeasible due to the potential for major disruptions. To address this, we leverage high-power energy storage solutions. Our supercapacitors, drawing a manageable 15 kW from the grid, achieve full capacity in just 7 minutes and subsequently charge the bus rapidly within seconds.

Cableless roof-charging

Automated cableless roof-charging using a pantograph system.

Larger climate context

European Union targets at least a 55% reduction in greenhouse gas emissions by 2030 and a 90% reduction by 2050. However, based on the latest data from the International Energy Agency, transport still heavily depends on oil products for approximately 91% of its final energy consumption. This is a mere decrease of 3.5 percentage points since the early 1970s. 

OECD reports highlight that cities account for roughly 70% of global greenhouse gas emissions, with a third of these emissions originating from urban transport. Addressing emissions from city transportation is pivotal to climate change mitigation, underscoring the urgency to innovate our urban mobility paradigms. Among various strategies, electrification of road vehicles has emerged as the foremost solution to enhance conversion efficiencies and diminish emissions. Advancements in charging technology can further improve the efficiency of public transport, ensuring smoother operations and progress towards sustainable transport.

Autonomous bus

The road ahead

Our work continues. We aim to refine the technology and identify new areas of application. Skeleton remains steadfast in its mission to integrate technology and sustainability for a more promising future. We extend our gratitude to Enterprise Estonia for their support and our dedicated partners for their efforts. Collaboration remains at the heart of our approach at Skeleton for reaching truly innovative and sustainable outcomes.

Read our white papers on supercapacitor fast charging for urban public transportation and supercapacitor and SuperBattery fast charging.

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