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Low-cost, High-efficiency FLYwheel Energy Recovery System for On-highway Commercial Vehicles

Periodic Reporting for period 1 - FLYwheel (Low-cost, High-efficiency FLYwheel Energy Recovery System for On-highway Commercial Vehicles)

Reporting period: 2017-02-01 to 2017-06-30

Currently there are very few Kinetic Energy Recovery Systems (KERS) for commercial vehicles that are attractive for OEMs and operators where the energy and CO2 saving is significant at a sensible price point. For example, full electric buses cost roughly double the price on conventional buses with a payback significantly greater than 10 years assuming the battery does not need replacing. Flybrid has previously produced a Flywheel KERS that had a significantly better payback than equivalent electric systems, but reducing fuel price and squeezed operator margins meant that taking this product to market was not economically viable.
This project was to determine if a Flybrid’s standard Flywheel Module developed for the off-highway, which stores energy in a high speed rotating flywheel and is significantly cheaper than a bespoke KERS system, could be connected to a commercial vehicle driveline with off-the-shelf components to produce a cost effective KERS. Pictures of the Flybrid Flywheel Module, module with hydraulic pump attached and an off-highway specification flywheel are attached.
The overall benefit for such a system would be a reduction in CO2 emissions from the commercial vehicle fleet. Typically a KERS can save 10-20% CO2 on the standard LUB regulatory drive cycle depending on the system specification and its efficiency. Reducing CO2 emissions is currently an important issue for society and a cost effective way of doing with a short payback could provide significant overall benefits.
The overall objectives for the project were as follows:
- Evaluate how the Flybrid’s standard Flywheel Module can be connected to a commercial vehicle using off-the-shelf hydraulic or electric components.
- Determine the CO2 reduction that can be achieved by optimising the performance of the system through simulation.
- Work closely with Tier 1 companies to define the specification of the hydraulic or electric components and the overall cost.
- Present the solutions to multiple OEMs, providing a business case including payback time and continue discussions to develop demonstrator vehicles and commercial relationships.
Initially work was performed to model the Flybrid Flywheel Module connected to a commercial vehicle driveline with hydraulic motor components and transmission components of varying levels of complexity. The vehicle model which had previously been validated with testing of a bus on Millbrook’s VTEC dyno was run over the standard LUB drive cycle to determine the fuel efficiency improvement that was possible for each of the hydraulic configurations. The initial results showed that either fuel efficiency improvements were not sufficient to hit the pay back targets, or the system had to be overly complex, which is not in-line with the objective to having a standard Flybrid Flywheel Module for multiple applications.
An alternative approach using an electrical system to connect the Flybrid Flywheel Module to the vehicle driveline was considered. The main concern with this approach was cost of the electrical system which consisted of two electric motors and their controllers. After consultation with a number of Tier 1 motor suppliers, it appeared that with the advent of mass produced electric cars, the cost of motors and their controllers was now at an acceptable cost point. An Electrically Connected Flybrid Flywheel Module Model was created and simulated with the vehicle model. After development of the control system and some optimisation of the strategy, Flybrid were able to demonstrate that use of the Electrically Connected Flybrid Flywheel Module has a potential fuel consumption improvement of >18% on a bus application. Additionally several methods of making further fuel savings were identified. Results also demonstrated that the flywheel connected motor generally operated close to the maximum efficiency point of the motor with the used strategy.
Discussion with Tier 1s on costs, OEMs on operating conditions for commercial vehicles and combining this with the expected fuel saving enabled the payback time to be determined. The result was a payback period of approximately 2 years which given Flybrid’s research is very attractive to OEMs and their customers.
The product appears to be at a very attractive price point, therefore the costs used are currently being verified and detailed discussion are being held with all major Tier1 electric motor manufacturers. Flybrid are also in the process of validating the concept to ensure that the performance predictions can be achieved.
These results are currently being disseminated to many commercial vehicle OEMs across Europe with expectation of generating interest in the system and making progress to developing a demonstrator system with a long term view on commercial production.
In parallel with this feasibility study, Flybrid have been evaluating other markets for the Flybrid Flywheel Module. This process has identified two additional market areas where the same system can be used to give significant additional benefits. The first market would be off-highway diesel electric powertrains, where a cost effective Electrically Connected Energy Storage Module can provide significant benefits by recovering kinetic energy, load levelling the engine load to improve engine efficiency or performance boosting to improve productivity. The second market is power generation where an electrical system can be used with electricity generator sets, to improve transient performance of the generator set, allowing the generator set to be optimally sized working at the best engine load without risk of any issues resulting from transient load steps. This also enables cleaner gas engines to replace diesel engines for many applications.
For the commercial vehicle application, if 5% of the market for commercial vehicles >3.5 tonnes (15,000 vehicles per year) could be fitted with this system, then the predicted fuel economy improvement would result in a 2 million tonne reduction in CO2 if those 15,000 vehicles were used for 15 years. This would be a significant contribution to CO2 output reduction, particularly for vehicles where full electrification is not practical today.
For diesel electric and in particular power generation applications, there is significant additional CO2 reduction benefits that could be realised with the same system. The overall potential CO2 saving is being analysed, but if a single 500kW generator set run at an average 75% load is able to deliver transient responses that previously required a 1500kW generator set running at an average 25% load, then typically fuel consumption is reduced by 18% or 22 litres/hour. This equates to a saving of 500 tonnes of CO2 per year per generator set. If this could be achieved for 266 generator sets, then the annual CO2 saving could be equivalent to fitting the system to 15,000 commercial vehicles. Exactly how many generator sets this saving can be made on is currently being validated.
Flybrid Flywheel Module
Flybrid Off-Highway Flywheel
Flybrid Flywheel Module with Hydraulic Motor