ENGINEERS at a giant North Yorkshire power station used groundbreaking technology and innovation at every stage to transform it into the UK’s largest renewable energy supplier.

To upgrade Drax, near Selby, to use compressed wood pellets - biomass - in place of coal its engineers had to break down the entire fuel delivery and energy generating process and build a vast processing plant from scratch – without any interruption to the eight per cent of the nation’s power it generates every day. This project lies at the heart of its entry in the Business Innovation category of The Press Business Awards.

Biomass has different properties to coal, which affect the way it burns and the type of ash produced. Therefore, Drax engineers had to address these differences and worked with UK universities to develop an advanced chemistry specification for the biomass composition and a new additive for its boilers as well as modifying boiler technology; achieving an eventual unit performance more efficient than coal.

Unlike coal, biomass cannot be stored outside as the pellets become unusable if damp. The problem was how to construct maximum storage within the limited confines of a working power station, quickly yet with minimum disruption, and knit this into the infrastructure.

“The engineers came up with a space-age solution: build four, large inflatable domes – the first time this construction technique has been used in the UK.

The basic structure of the 63m by 49.2m domes was in place in less than an hour, then a protective coating of polyurethane foam, 500 tonnes of reinforcing steel and 3,500 cubic metres of concrete were applied before the dome head technology was installed.

Drax engineers took the ‘unprecedented’ step of replacing air inside the domes with inert nitrogen to help avoid spontaneous combustion, while below ground a three-storey basement was built to house hoppers taking delivery of the pellets. The team then helped to design Britain’s first purpose-built biomass rail freight wagons.

The upgrade of three of the six Drax generating units to biomass should be completed this year.