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Renewable Energy
As a responsible department, DSD has been playing an active role in mitigating global warming through best practices of energy saving. We have also been enhancing our policy on total energy management at Sewage Treatment Works (STW) and making use of more renewable energy technologies, including the application of solar, and regeneration of energy from biogas.
Solar Energy
Solar energy has been used at various DSD facilities, which include solar water heaters installed at various STWs providing hot water for daily usage; photovoltaic (PV) panels at some remote locations supplying electricity to equipment; and large scale grid-connected PV systems supplying electricity to part of the equipment at various major DSD facilities.
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Solar water heater at Shek Wu Hui STW |
PV panel system for remote gauging station for flood warning at Wong Chuk Yeung Tsuen, Fo Tan |
Grid-connected PV system at Yuen Long STW |
Biogas
DSD’s major secondary STW in Sha Tin, Tai Po, Shek Wu Hui and Yuen Long employ anaerobic digestion process in sludge treatment. During the treatment process, biogas, a mixture of around 65 per cent methane gas and the rest being carbon dioxide, is produced as a by-product. It is produced by the biological breakdown of organic matters in the absence of oxygen, and is a renewable fuel
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Biogas water boiler at Tai Po STW |
Biogas Hot Water Boiler
In these four sewage treatment works, biogas has been used as fuel for gas boiler for generation of hot water to sustain the digestion process at a specific temperature.
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Generation of Electricity by Biogas
1. Dual Fuel Engine Generator
Dual fuel engine generators are installed at the Shatin STW for supplying equipment with electricity. Cooling water and heat released from flue gas are also transformed to hot water for maintaining the temperature required for sludge digestion. |
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Dual fuel engine generator at Sha Tin STW |
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2. Combined Heat and Power (CHP) Generation System
CHP generator is to obtain energy from a single fuel (e.g. biogas) by means of combustion, where heat and power (electricity) are generated simultaneously so as to improve the overall energy usage efficiency.
Since March 2006, DSD has installed three CHP generation systems which use biogas as fuel. These include one 330 kW and one 635 kW CHP generator at Shek Wu Hui Sewage Treatment Works and another 625 kW CHP generator at Tai Po Sewage Treatment Works. The generated electricity was supplied to the facilities within the sewage treatment works while the recovered thermal energy is for pre-heating the recirculation water which provides heat to support the sludge digestion process as required. Another set of 630 kW CHP generator will be installed at Tai Po Sewage Treatment Works in mid 2013 to provide electricity for the facilities within the two plant. |
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A 330kW CHP generator at the Shek Wu Hui STW to generate electricity and heat for use of plant facilities |
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