Skip to content

Vulcanaer: Air Hybrid for Diesel Engines

Regenerative hybrid engine system that harvests braking energy during deceleration, reducing emissions and saving fuel.

Published: 11th December 2018
Vulcanaer: Air Hybrid for Diesel Engines
Please note, header image is purely illustrative. Source: Dan Benedict Banaag, Flickr, CC BY 2.0


While the all-electric transport revolution is awaited, existing bus and truck diesel vehicle fleets need to meet emerging civic requirements for cleaner air in cities. The long life span of such vehicles mean that many will be in operation for many years to come. Vulcanear will enable existing diesel vehicles to meet the requirements of reduced emissions as well as providing operators with fuel cost savings.

In urban transport systems there is a significant waste of energy due to frequent acceleration and deceleration. There is an opportunity to modify existing diesel engines to harvest the energy ‘wasted’ through deceleration thereby reducing CO2 and NOx emissions and saving on fuel costs.

In busy urban areas, where there is a requirement for buses to turn off their engines when stopped to reduce emissions from idling, there are issues with the need to then restart the engine. This uses the battery and an electrical starter, both of which wear out quickly, resulting in broken down buses requiring expensive replacements. Vulcanaer provides a solution to this problem with the added benefits of additional cost savings on fuel.

Technology Overview

Vulcanaer is a novel regenerative hybrid engine system that converts the vehicle engine into an air pump during decelerations. It harvests the braking energy and stores it as compressed air for subsequent use to restart the engine in stop/start operation, saving battery and starter motor life. It also saves fuel as the compressed air also assists the normal engine-driven air compressor. Furthermore it can enhance the turbo thus reducing black smoke during acceleration from stationary.

First generation system trials on a Yuchai bus in China showed fuel savings of 5% to 9% on an urban bus operating cycle. A second generation retrofit system has been demonstrated to be feasible on a 9.6L bus engine in the UK with no adverse effect on driveability.

Vulcanaer is protected by a family of patents with granted cases in multiple countries.

Figure 1: Vulcanaer converted engine


  • The technology enables both reduction in CO2 and NOx emissions and fuel savings.
  • The mechanical system is simple and fail‑safe. It only engages when the vehicle brakes therefore not affecting normal driving.
  • Suitable for retrofit with conversion taking less than a day without the need to remove the engine.
  • Low cost (typically £4000) providing fleet operators with payback in less than 2 years.
  • Also suitable for original equipment manufacturers.


Diesel transport systems, particularly urban busses and delivery trucks, where there is frequent acceleration and deceleration and a need to reduce emissions.


Searching for investors and / or partners interested in commercialising the technology.

IP Status
  • Patented
  • Commercial partner
  • Seeking investment