SINGAPORE – Public bus operator Go-Ahead Singapore will install ultra-thin solar panels on the roofs of 50 more buses after a proof-of-concept trial in 2021 showed positive results.
By end-April, a total of 52 diesel-powered buses will be fitted with flexible, 1.6mm-thick solar panels, and the vehicles will be deployed across the 31 services operated by the company here, it said on Monday.
These buses, which will not be fixed to any one service, make up about 11 per cent of Go-Ahead Singapore’s roughly 450-strong bus fleet, which also includes several electric buses.
When all 52 buses with solar panels are fully deployed here, the company said it expects the carbon emissions from the vehicles to be cut by about 200 tonnes annually. This is equivalent to the annual carbon emissions of 43 passenger cars.
The roof-mounted solar panels weigh less than 20kg in total, and they can generate 1,000 watts of energy, which is enough to power a small kitchen appliance.
The solar panels help to save fuel by charging the bus battery, which would otherwise have to rely on the vehicle’s alternator. This, in turn, reduces the load on the bus engine.
The bus battery is typically used for ignition and to provide power to the bus when the engine is turned off.
In March 2021, two Man A22 Euro 6 diesel buses were fitted with the solar panels to test whether they were effective in harnessing solar energy under Singapore’s tropical climate and traffic conditions.
The buses were used on service 15, which starts and ends at Pasir Ris Bus Interchange, and the panels were also evaluated on whether they were robust enough to withstand the higher temperatures and daily washing.
Go-Ahead Singapore said the trial showed that the buses were able to achieve fuel savings of 3 per cent to 4 per cent a year, which translates into about 3.7 tonnes to four tonnes of carbon emissions a year per bus.
These were the results that the bus operator had predicted when it started its trial here. The projections were based on data from a similarly successful trial conducted in Southampton, Britain, that used larger solar panels with a higher total capacity.
The trial in Singapore, which was supposed to last six months, was extended to collect and analyse more data, Go-Ahead Singapore said in response to queries.
This was because fluctuations in commuter travel patterns and bus loading during the Covid-19 pandemic had influenced fuel consumption data, the company said.
Go-Ahead Singapore said the decision to install solar panels on more buses came after consultations with the Land Transport Authority (LTA). The authority owns all bus assets here under Singapore’s bus contracting model.
Go-Ahead Singapore added that the solar panel initiative is also in line with parent company Go-Ahead Group’s ambition to be a net-zero carbon business by 2045.
In a statement, Go-Ahead Singapore managing director Andrew Thompson pointed to Singapore’s commitment to have a 100 per cent cleaner energy bus fleet by 2040.
“During this period of transition, we can focus on the fuel efficiency of existing diesel-powered buses to decarbonise,” he said. “Installing roof-mounted solar panels on diesel-powered buses is one alternative in which we can make the buses greener and more efficient until the end of their useful life,” he added.
In March 2022, Transport Minister S. Iswaran said that LTA will replace more than 400 diesel-powered buses with fully electric ones by 2025. More electric buses will also be added as diesel buses that reach their statutory lifespan of 17 years are replaced.
Go-Ahead Singapore did not say how much the installation of the solar panels on the 50 buses will cost.
But it previously said that it expects to recoup the cost of the 2021 trial within four years from the savings that result from the reduction in fuel consumption.