Melbourne Water is using one of its major waste streams – excessive hydraulic pressure – to generate power.
The utility now has 14 mini hydro-electric power stations, generating some 70,000 MW hours each year.
“That’s enough to power about 14,100 homes, which is equivalent to 76,000 tonnes of carbon dioxide emissions, or 29,200 cars,” said Ian Royston, Melbourne Water Senior Project Manager, Major Program Delivery.
“In terms of our drinking water supply system, we now generate more in hydropower than we consume from the grid.”
In the decade to 2017, Melbourne Water installed 12 new hydro-electricity plants, starting with seven larger systems commissioned in 2008 and 2009.
“We began with the sites that would give us immediate economic benefit – those that were closest to the electricity grid and generated the most power,” Royston said.
The first technical challenge was the pressure transient risk.
“When the mini hydro suddenly disconnects from the electricity grid you get a sudden increase in the speed of the plant, which then creates a pressure transient – or water hammer – through the pipeline,” he said.
“We did extensive modelling of our water supply system to ensure that we could manage pressure transients through innovative power station design, valving and surge mitigation.”
Melbourne Water also had to negotiate electricity grid connection and complete extensive modelling to demonstrate that the plants wouldn’t affect the network.
For the smaller stage two sites commissioned in 2017, Melbourne Water took a novel building approach in order to ensure a positive financial return.
“We used a containerised modular building approach, which reduced the site costs significantly. The other thing was that we didn’t just go and build one plant – we built multiple plants, which gave us economies of scale,” Royston said.
Melbourne Water is now embarking on a third round of mini hydro projects and is in the final investigation stages for up to 10 more plants.