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igem news – yppc

To enhance the biogas utilisation TABLE 1 ADVANTAGES AND DISADVANTAGES OF COMBINED HEAT AND POWER (CHP) TECHNOLOGIES
efficiency and balance the thermal load,
a tri-generation system was proposed CHP technology Advantages Disadvantages
as a retrofitting scheme for the CHP
system at the Shatin sewage treatment Gas engines Wide range of sizes (110- Requires continuous cooling
works. Tri-generation is a thermal 4000kW) May need fuel pre-treatment
system, also known as a combined Higher electrical and to avoid potential engine
cooling, heating and power (CCHP) cogeneration (electrical damage or efficiency loss
system, mainly comprising a CHP thermal) efficiencies
Reliable, well-proven
module for generating electricity and technology from several
heat and a thermally-driven chiller for manufacturers
producing cooling. Non-specialised maintenance
District cooling for nearby office Gas turbines Higher thermal efficiency Available in a limited number
buildings via chilled water produced by Reliable, well-proven of larger sizes (>1,500kW)
the absorption chiller technology from several Lower electrical efficiency
Energy saving and emissions manufacturers Warm weather and elevation
reductions are the main benefits of the Fewer moving parts, generally reduce electrical efficiency
tri-generation system and the chilled require less frequent Require high pressure fuel
maintenance
Specialised maintenance
water produced by the absorption Clean exhaust emissions
chiller can be used for two purposes: Suitable for unattended
• District cooling for nearby office operation
buildings or residential buildings
• Cooling the power house to Micro-turbines Smaller sizes (30-250kW) Lower electrical and thermal
maintain a standard working Low levels of NO and CO efficiencies
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condition for the CHP unit, especially exhaust emissions Lower exhaust temperatures
in the summer Quiet and suitable for outdoor Limited number of vendors
With a view to satisfying different installation without adding a Require fuel gas clean-up
cooling and heating demands in separate building Poorer track record
different seasons, strategic control of
the tri-generation system is adopted Improvement of thermal efficiency with average thermal energy efficiency of
for capturing the thermal energy from the adoption of absorption chiller a CHP system is only 13.6 per cent,
CHP. In the summer, exhaust gas The results show that the absorption much lower than 18 per cent found
and jacket hot water are used by the chiller improves the thermal in a tri-generation system. Therefore,
absorption chiller for chilled water, efficiency of the system by using the thermal efficiency is improved by
while the hot water after the chiller is excess heat for chilled water 32.4 per cent. Meanwhile, it provides
used for heating the sludge digestion production. Comparisons of the multiple services simultaneously,
tank. In the winter, digester heating is thermal energy efficiency between avoiding the requirement for operating
given priority and the surplus waste the tri-generation system and CHP a boiler and providing more accurate
heat is used for cooling. system are shown in Figure 5. The control of the sludge temperature.

FIGURE 2 STRATEGIC FRAMEWORK OF UTILISATION OF BIOGAS

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15/09/2021 12:12
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IGEMNews_YPPC.indd 2 15/09/2021 12:12