Flywheel Energy Storage andH2-ICE for Off-Highway

PUNCH Flybrid has launched production of its 600 Series Energy Storage system, for use with a range of off-highway construction machinery ranging from excavators to dynamically operated diesel and gas generators. The high-power density and durability of a flywheel energy storage system makes it ideally suited to the duty cycles and usage patterns typically observed on such machines. Long operational hours, with frequent high-power events, pose degradation and thermal challenges for other energy storage solutions such as batteries and super-capacitors. The flywheel captures energy that would normally be wasted when a machine decelerates to a stop or when, for example, the boom on an excavator is lowered, and deploys this energy on the next working cycle. This can be used to assist the prime power unit of the vehicle to either reduce its fuel consumption or increase its productivity.

Flywheel Technology At the heart of the 600 series system, is a patented flywheel design capable of over 80,000hrs of operation, with no degradation in performance. A key feature of PUNCH Flybrid’s flywheel technology is its vacuum seal design which allows the flywheel to run in a vacuum for maximum efficiency, while simultaneously allowing for a shaft type power take-off. This means that the flywheel can be integrated into a machine in different ways, electrically when coupled to an electric motor, mechanically via a transmission or hydraulically when connected to a hydrostatic pump. The flywheel module is constructed from materials and techniques widely adopted in the automotive industry making it efficient to produce, is ultra-reliable and also gives the flywheel a low embedded CO2 figure allowing the machine to achieve even greater CO2 savings.

H2-ICE for heavy duty vehicles While the passenger car market is moving rapidly towards increased levels of vehicle electrification as a means of reducing CO2 emissions, the requirement of heavy and expensive batteries makes this inefficient for heavy vehicles with large energy requirements such as those in the construction industry. For these types of vehicles, hydrogen offers a more sustainable and cost-effective decarbonisation route. Recent years have seen renewed interest in H2-fuelled ICEs as alternatives to fuel cells. Fuel cells tend to have a higher peak efficiency at low loads but the efficiency rapidly deteriorates in the mid to high load regime. The efficiency of an ICE, on the other hand, peaks and plateaus at the mid to higher loads. As a result, for machines predominantly operated at high loads, the efficiency of an H2 ICE is in fact comparable to that of a fuel cell. Moreover, extensive work by PUNCH Torino who are currently in the advanced stages of developing a H2-fuelled ICE, shows that for hybridised machines the engine operation can be more easily constrained to the optimal region. When combined with their lower initial purchase cost, this places H2-fuelled ICEs very favourably in terms of Total Cost of Ownership (TCO). Additionally, H2-fuelled ICEs can leverage an already existing production infrastructure, servicing network and skilled workforce.

PUNCH Power 200 for dynamically operated generators PUNCH Power 200 (PP200) was created by coupling the 600 Series flywheel module to an electric motor controlled by a variable frequency drive. Designed to seamlessly connect to any power grid, PP200 is able to rapidly inject and absorb electrical power to maintain a stable grid frequency and voltage while simultaneously reducing the required genset size. PUNCH Flybrid has conducted field trials with PP200 on numerous applications ranging from pump-jacks on oil production sites to tower cranes on live building sites. In the latter, the required genset rating is traditionally double that of the crane. The oversizing is traditionally specified because load steps to 100% of crane power are frequent and most gensets can only maintain an acceptable frequency and voltage response with a 50% load step or less. With PP200 installed, the genset can be ‘rightsized’ as the flywheel system maintains stable voltage and frequency whilst giving the genset time to achieve the target load. Testing has shown that typically the genset rating can be reduced by 50% or more, with similar reductions in fuel consumption, CO2 emissions and significant reductions of numerous pollutant emissions. These benefits will be even greater with the move to Stage V generators due to their requirement to be operated at higher base loads than current Stage III gensets. Furthermore, the changes in Red Diesel taxation will double the fuel cost and therefore will make fuel efficient sizing of generator sets even more important.

PUNCH Flybrid conducted a programme with one of its off-highway partners in which a 380kJ, 210kW flywheel module was integrated into a 37-tonne excavator. The programme included an extensive validation programme, including real world operations with a customer machine to demonstrate that the flywheel module is production-ready. Significant fuel consumption reductions of 30% are achievable with engine load levelling.