Transcript Waste Heat Recovery

By
John Yee
 Organic Rankine Cycle (ORC)
 Same working principle as Rankine cycle
 Organic – pentane, propane, ammonia, and coolants
 Uses for ORC
 Low-grade heat waste recovery
 Energy generation is conventionally done using Rankine
cycle with steam
 Water needs to be superheated to ~600C to prevent
condensation during expansion.
 Organic fluids
 Evaporation at lower temperatures and pressures
 Lower temperature of waste heat can be used
 Energy generation from temperatures as low as 80C to
100C is possible
 Carnot efficiency: 𝑛𝑡ℎ = 1 −
𝑇ℎ
𝑇𝑐
 Utilizes wastes (wood shavings, barks, sawing, chips)
of a big sawmill
 Thermal and electrical energy
 Thermal heat and hot water
 Nearby schools and hospital
 Case 1: Max energy production ~5MW
 Electrical efficiency: 15.5%
 Net electrical + useful thermal: 33%
 Case 2: Max thermal load
 Electrical efficiency: 9.5%
 Net electrical + useful thermal: 71.8%
 Similar systems have appeared in the lumber industry
 Trigeneration – combined cooling, heating, and energy
generation
 Heating: Condenser Q,out
 Cooling: Single-effect absorption chiller
 mixture of lithium-bromide (Li-Br) and water.
 ORC working fluid
 Octane(C8H18): Boiling point 125C
 Overall efficiency: ~76%
 Electrical efficiency: 15%
 Ratio Electrical:Cooling: ~4
 Ratio Electrical:Heating: ~0.2
 Geothermal heat sources vary in temperatures from 50 to
350C.
 High-temp >220C are most suitable for commerical
production of electricity with dry steam and flash steam
systems.
 <220C is most commonly available.
 Commercial cogeneration using natural gas
 Few common working fluids with different characteristics
modeled
 Overall efficiency increase of ~5%
 41.8% -> 47.1%
 Low temperature thermal electric generation
 Non-tracking concentrated solar collectors
 180-200C
 Working fluid: HCFC-123
 Short half life
 Irradiation: 750 W/m2
 Al-Sulaiman, Fahad. “Performance comparison of three trigeneration
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Pei, Gang, Jing Li, and Jie Ji. “Analysis of low temperature solar thermal
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