By 2040, the amount of energy used in the water sector is likely to double due to trends including increased desalination, large-scale water transfers, and increasing demand for wastewater treatment, as well as higher levels of treatment.
The energy used to supply water and clean used water is responsible for around 3–8% of global greenhouse gas emissions. With global demand for water projected to increase by 55% by 2050, a business-as-usual scenario will see emissions increasing by 50% in the same timeframe.
Hong Kong Proactively Promoting Renewable Energy
DSD has been proactively promoting the use of renewable energy, including solar power, hydropower, and biogas to reduce electricity consumption by around 4% by 2024–25, as compared to 2018–19. At present, DSD’s renewable energy installations generate around 28 million kilowatt-hours of electricity per annum, constituting around 9% of the utility’s annual energy demand.
DSD has installed photovoltaic (PV) systems at selected facilities. As of March 2020, PV panels have been installed at 14 sewage treatment plants, 13 sewage pumping stations, and one stormwater storage facility. The solar farm at Siu Ho Wan Sewage Treatment Works is currently the largest installation, generating up to 1.1 million kilowatt-hours of electricity per annum. In the coming years, DSD will install PV systems in its facilities, including thin-film PV panels at Stonecutters Island Sewage Treatment Plant to utilise space as much as possible, with locations such as sedimentation tank covers occupied for solar power generation.
DSD has installed a hydro-turbine system at Stonecutters Island Sewage Treatment Works. The system utilises the hydraulic energy from the flow of sewage to drive the turbine and generate electricity for in-house use. The system is fully automated and the generator speed is regulated according to the sewage flow rate. Overall, the system can generate up to 120,000 kilowatt-hours of electricity per annum. Due to the success of the system, a second hydro-turbine system will be installed at Stonecutters Island Sewage Treatment Works.
A total of six combined heat and power generators and three gas turbines (running on biogas) have been installed in DSD’s sewage treatment plants to generate electricity and heat for in-house use. Each year, the total energy generated by biogas amounts to 26.7 million kilowatt-hours. Furthermore, DSD is cooperating with the Environmental Protection Department to commence operation of the Food Waste/Sewage Sludge Anaerobic Co-digestion Trial Scheme at Tai Po Sewage Treatment Plant to generate electricity and heat for the sewage treatment plant, reducing municipal solid waste while increasing biogas production.
Water utilities can become renewable energy powerhouses.
Robert Brears is the author of Urban Water Security (Wiley) and Founder of Our Future Water.
This article was originally published on Medium on November 24, 2021 and was respublished with the kind permission of the author.
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