Solar panels installed on Go-Ahead buses

Local public transport operator Go-Ahead Singapore has installed solar panels on the roof of its buses. Solar panels improve vehicle efficiency, thereby consuming less diesel fuel and reducing emissions.

Following a proof-of-concept trial with two buses launched in March 2021, Go-Ahead announced in January 2022 that it would install these solar panels on 50 more buses, with completion of installation works expected by end-April 2023.

2021 Trial

On 30 March 2021, Go-Ahead Singapore launched a 6-month proof-of-concept trial for buses with roof-mounted solar panels. Two MAN A22 (Euro 6) buses received these solar panels, namely SG1798M and SG1843R, both of which were deployed to Bus Service 15 on a regular basis.


2023 solar panel rollout

In January 2023, Go-Ahead announced that it would install solar panels on 50 more diesel buses by April of the same year. These vehicles would be deployed across all Go-Ahead bus routes without being fixed to a single service. In total, these 52 solar panel equipped buses would make up around 11 per cent of Go-Ahead’s fleet.

Technical Background

Like all vehicles, buses have an electrical system (typically 24V DC) that provides electrical power to a wide variety of ancillary equipment, such as doors, interior lights, CCTV cameras, vehicle onboard computers, revenue service equipment, and so forth. This electrical system is coupled to a battery that powers these components while the engine is off.

ADL Enviro500 (Euro 6) Chassis - Alternators
ADL Enviro500 (Euro 6) Chassis – Alternators

On a typical internal combustion engine vehicle, a belt-driven alternator is used to convert the mechanical power of a running engine into electrical power. This is used to supply power to the electrical system, and to recharge the batteries.

By using solar panels to supplement the electrical power demands of the bus, less power is drawn from the engine via the alternator, leading to lower fuel consumption and carbon emissions.

In addition, solar panels allow ‘trickle charging’ of the bus battery, and supplies power to onboard systems that consume energy even while the engine is off. This reduces battery discharge cycles and prolongs the lifespan of the battery.

Solar panel specifications

The solar panels used are CIGS thin-film solar cells, which are known for being lightweight and flexible, and are well-suited for mounting on vehicles. Two such solar panels are mounted on the roof of the bus, each 1.6-mm thick, producing a combined 1000 watts.

Solar panels produce DC current, which makes for easy integration with a bus’ 24V DC electric architecture. The entire system weighs less than 20 kg in total, thus contributing minimal additional weight or wind resistance.

The solar installation is supplied by TRAILAR, a UK-based company that sells solar panel kits for a variety of commercial vehicles. In 2019, it fitted solar panels onto 18 buses operated by Go-Ahead subsidiary Bluestar in Southhampton.

Based on Go-Ahead’s Southhampton trials, these solar panels are estimated to help Go-Ahead Singapore save 1,400 litres of diesel per bus per year, which translates to about a 3 to 4 per cent reduction in the typical fuel consumption of the MAN A22 (Euro 6) bus, equivalent to 3.7 tonnes of carbon emissions per bus per year. Fuel savings are expected to be greater in Singapore’s sunnier climate, and Go-Ahead expects to recoup the cost of the trial within four years.

According to TRAILAR, its products use MiaSolé FLEX photovoltaic modules, which deliver >17% cell efficiency. MiaSolé is a leader in thin-film CIGS modules, cells and equipment. In addition, TRAILAR first entered the Singapore market a year prior, having fitted solar panels to 13 waste collection vehicles operated by ALBA W&H in 2020.

Trial Operational matters

Under the Bus Contracting Model, the Land Transport Authority (LTA) owns the buses and leases them to public transport operators such as Go-Ahead Singapore. As such, both Go-Ahead Singapore and LTA collaborated on the solar project.

According to Go-Ahead, the buses underwent rigorous safety assessments by the LTA before being approved for public road trials. The panels will initially be inspected every week for two months, after which the inspection schedule will be reviewed.

As for the bus route, Go-Ahead selected Bus Service 15, a 33 km route from Pasir Ris and looping at Marine Parade, via Tampines and Kaki Bukit, Jalan Eunos and Telok Kurau. The firm had considered conducting the trial on shorter routes such as feeder services but decided on a longer route to better test the system. A BYD K9 electric bus was previously trialled on Service 15 in 2016-2017.

If the trial proves successful, Go-Ahead would consider rolling out solar panels to more buses, including its electric buses.

Trial Results

As part of its January 2023 announcement, Go-Ahead revealed that the solar panel trial met the expected 3 to 4 per cent reduction in fuel consumption, equivalent to 3.7 tonnes to four tonnes of carbon emissions a year per bus. These were similar statistics cited in the 2021 trial.

In response to queries, The Straits Times reported that the initial trial, which was supposed to last six months, was extended to collect and analyse more data. This was because fluctuations in commuter travel patterns and bus loading during the COVID-19 pandemic had influenced fuel consumption data.

Special Advertising Wrap

The two solar panel-fitted buses are affixed with a promotional advertising wrap, with messages such as:

  • Did You Know That The Solar Panels On My Roof Reduce Carbon Emission By About 4000KG Per Year?
  • Singapore’s First Solar Panel Bus!!
  • This Bus Has A Solar Panel Fixed On Top!

SBS Transit – Solar Panel Bus

About 10 years ago, solar panels were already fitted on one unit of Volvo B10M Mark IV (Strider), registered as SBS2652G. The bus kept its solar panels until its retirement in August 2015.

The outcome of the trial is not known.

Other Bus Roof-Mounted Initiatives

In May 2019, the Garden On The Move initiative was launched at the inaugural Singapore Garden Festival Horticulture Show. 10 SBS Transit Scania K230UB Buses were fitted with GWS Living Art’s GaiaMat Green Roof System, and deployed on Singapore’s roads for at least three months.

The research study aimed to explore the use of a green roof to reduce heat transmission through vehicular roofs, leading to a reduction in the fuel consumption used for air-conditioning.


2023 Trial Expansion

Following the successful trial, 50 more buses operated by Go-Ahead Singapore will be installed with roof-mounted solar panels.


One thought on “Solar panels installed on Go-Ahead buses

  • 8 April 2021 at 7:34 PM

    I took sg1798m on 1st april while coming home from school


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