Work on the world's largest solar bridge formally begins today as the first of more than 4,400 solar panels are installed above the new Blackfriars station platform.

The historic London site is undergoing a multi-million pound refit, which includes extending the platform along Blackfriars Bridge, a structure built in 1886.

When complete in 2012, the Victorian bridge will play host to some 6,000 square metres of photovoltaic (PV) panels, making it London's largest solar array.

Solarcentury, the UK company managing the installation, expects the panels to generate around 900,000kWh of electricity a year, providing half of the station's energy and reducing annual CO2 emissions by an estimated 511 tonnes.

"Blackfriars Bridge is an ideal location for solar; a new, iconic large roof space, right in the heart of London," said Solarcentury chief executive Derry Newman in a statement.

"Station buildings and bridges are fixed parts of our urban landscape and it is great to see that this one will be generating renewable energy every day into the future. For people to see that solar power is working is a vital step towards a clean energy future."

Other energy saving measures, such as rain harvesting systems and sun pipes for natural lighting, are also being fitted at Blackfriars, as part of Network Rail's plans to reduce carbon emissions by 25 per cent per passenger kilometre by 2020.

Lindsay Vamplew, Network Rail's project director for Blackfriars, said that the refurbishment will make the station a template for green stations around the world.

"The Victorian rail bridge at Blackfriars is part of our railway history," he said. "Constructed in the age of steam, we're bringing it bang up to date with 21st century solar technology to create an iconic station for the city."

One other solar bridge is known to exist, the Kurilpa footbridge in Brisbane, Australia, although 16,000 solar panels were laid on the top of a train tunnel in Belgium earlier this year. The array is capable of powering all of the country's trains for one day a year.