Star Ferry’s new “green” diesel-electric ferry system, funded by taxpayers to the tune of around HK$3m of its HK$8m cost, uses the same amount of diesel fuel as regular diesel ferries, according to a report into its first few months of operations.

Fuel consumption data from an Environmental Protection Department (EPD) report shows little difference between the diesel-electric fuel consumption and fuel consumption of a 30-year-old diesel engine, meaning the carbon emissions from the green ferry will be virtually identical to older ships and would not contribute towards Chief Executive Carrie Lam Cheng Yuet-ngor’s ambitious 2050 “zero carbon” goal.

From September to November 2020, the diesel-electric Morning Star burned through 32.1 litres of diesel per hour, compared to 32.5 litres per hour for a regular ferry, Northern Star, plying a similar route. That represents just a 1.2% reduction in fuel use – and doesn’t include data from the first three months of the trial which, the report says, was “not representative” and excluded from the public eye.

“The applicant took a few months from June 2020 to Aug 2020 to optimise the most suitable operating mode for the ferry operation under the trial. In view of this, the Independent Assessor suggested that data should be collected for assessment after the completion of the optimisation of operation starting from September 1, 2020 onwards,” says an EPD spokeswoman, explaining the missing data.

A similar trial in 2018 also found statistically insignificant fuel savings from a diesel electric system, with the 2018 report finding the extra weight of environmental systems cancelled out any projected savings.

Weight problems may also affect the 2021 trial performance: Morning Star‘s net weight more than doubled after the refit, from 40 tonnes to 100 tonnes, while its passenger capacity was reduced 26%, from 540 passengers to 399.

According to the 2021 report, ferry crew were unhappy with the performance of the ferry in the first few months. “Four captains were interviewed in the reporting period and they had different opinions on the operation of the DEP [diesel electric propulsion] ferry. In general, in the first three months, they did not have very positive responses, especially they found the DEP system noisy and the propulsion system slow in response. However, in the last interview, they all expressed no problem in operating the DEP ferry and were satisfactory with its performance,” says the report.

But good news is found in terms of air pollution: particulates, smog-forming NOx and hydrocarbons were found to be significantly reduced (86%, 77% and 83% respectively), and carbon monoxide was reduced by a third. Sulphur dioxide emissions were not reduced at all, as both the traditional and new ferry use ultra-low sulphur fuel, a legal requirement since 2014.

The improvement in emissions is likely due to the diesel-electric using new diesel engines, still under warranty, while the benchmark ferry is fitted with a 30-year-old engine, the report suggests. The new engines also kept the “green” ferry working harder, with only one day downtime during the three months against 2.5 days for the traditional ferry.

The government subsidised the diesel-electric scheme under the 10-year-old New Energy Transport Fund (previously named the Pilot Green Transport Fund), which pays for up to half the cost of electric vehicles or systems in exchange for full and detailed reporting on the first two years of operation.

Norway’s electric ferries ditch diesel altogether

With a 300-passenger capacity, Norway’s carbon fibre Rygerelektra could make 45 round trips across Victoria Harbour on a single charge

The Morning Star‘s diesel electric system uses two diesel engines to power a generator, which charges batteries, which power the propellor motor. The system has potential for a ferry to be charged by electricity at the pier, with the engines firing only to keep batteries at optimal charge during a trip – but with no pierside charging in Wan Chai or Tsim Sha Tsui, the ferry’s engines are used in a very traditional way, essentially powering the propellor directly, albeit through the generator/battery/motor system rather than through a direct mechanical linkage. This is evident from noise aboard the ship, with engines screaming at “take off and landing” and reducing for the cruise across, operating much as a traditional diesel propulsion system.

The performance of the system contrasts with cleaner carbon-neutral ferry technology in other parts of the world – speaking on RTHK’s Wham Bam Tram! this Saturday night, co-host Martin Turner pointed out the progress made in Norway using electric ferries, which are charged at dock and which don’t rely on diesel fuel at all.

Norway’s popular “Ampere” all-electric ferry cuts carbon emissions by 95%, and costs by 85%, compared to its diesel counterparts. The ship, which carries 120 cars, eight trucks and 350 passengers across a 6km fjord, is also virtually silent and reduces passenger exposure to toxic diesel fumes. Meanwhile the newer carbon fibre Rygerelektra can cruise 93 km at 17 knots (31.4 kph) on 70% of its 2MWh battery capacity, all while carrying 297 passengers. Rygerelektra’s range means it could run around 45 round-trips across Victoria Harbour on one charge.

“This vessel is breaking barriers for environmentally conscious transportation and serves as a testament to what is possible with all-electric propulsion,” says its maker Brødrene Aa.