Application of Exergy-based Methods for Technical, Economic and Environmental Assessments of Nuclear Cogeneration Marc A. Rosen Past-President, Engineering Institute of Canada
Professor, Faculty of Engineering & Applied Science University of Ontario Institute of Technology Oshawa, Canada Outline
Exergy Exergy and efficiency Exergy and environment Exergy and economics Example: allocating cogeneration emissions Illustration: utility cogeneration in Ontario Introduction
Efficiency of energy systems must be understood to increase it Energy a misleading efficiency measure Exergy can help improve understanding of efficiency efficiency Exergy also helps efforts to improve economics, environment, sustainability Objectives
Improve understanding and appreciation of exergy
Show exergy can improve nuclear cogeneration EXERGY What is Exergy?
Maximum work obtainable in reference environment Potential to cause change Measure of quality usefulness value Merger of first and second laws Key Exergy Feature I
Not conserved (unless reversible)
“Destroyed” in real processes Key Exergy Feature II
Energy forms differ:
Work
Heat
Cold
Matter Key Exergy Feature III
All energy is equal, but not all energy is equally valuable Exergy & Reference Environment
Exergy dependent on system and reference environment
Exergy-environment tie has implications for environment EXERGY AND EFFICIENCY Exergy Analysis
Helps analyse, design & improve Clarifies: losses - locations, types, magnitudes efficiencies - always approach to ideal, unlike for energy Identifies margin available to design more efficient systems Applications All Energy Systems (and More)
Use
Supply
Conversion Illustration Ideal Heat Engine
Energy efficiency = 50% (yet device ideal)
Exergy efficiency = 100% Carnot engine operating between 600 K and 300 K Illustration Pickering Nuclear Power Plant Illustration Pickering Nuclear Plant Results
Energy outputs Exergy outputs & consumptions EXERGY AND ENVIRONMENT Exergy and Environment
Exergy linked to environmental impact (measures departure from environment)
Increasing exergy efficiency reduces environmental impact by reducing exergy losses
emissions
destructions Exergy & Environment Relations Exergy & Sustainability EXERGY AND ECONOMICS Exergy & Economics
Exergy normally consistent measure of economic value (energy sometimes is)
Exergy-based economic analyses:
recognize exergy, not energy, of value
assign costs/prices to exergy variables
help allocate economic resources optimally EXAMPLE: ALLOCATING COGENERATION EMISSIONS Cogeneration
Thermal Heat Winter Power Electricity Recovery Heating Generation Load
Fuel CO2 Allocation Methods for Cogeneration
Energy content of products
Exergy content of products
Economic value of products
Incremental fuel use to electricity production
Incremental fuel use to heat production
Shared emission savings between electrical and thermal energy
Agreement
Other factors 120
100 Allocation of emissions for Cornwall 80 cogeneration and district heating system
60 ) % 40
20 ission allocation (
Em 0 Based on Based on Incremental Incremental Shared Based on exergy of energy of fuel to fuel to heat emission economic products products electrical production savings product -20 production values Emission allocation to thermal product Overlap for electricity/heat cost ratios of 1.5-2.5 Emission allocation to electrical product Trigeneration Expanded Cogeneration
Thermal Heat Power Winter Electricity Recovery Generation Heating Load
Fuel Absorption Summer Chiller Cooling Load Extension to Economics
Exergy can similarly be used to allocate costs among cogeneration products more rationally, yielding better pricing, for cogeneration and related processes ILLUSTRATION: UTILITY COGENERATION IN ONTARIO Ontario, Canada
13.5 million people
1 million km2
Industrial heart of Canada
Large electric utilities (nuclear, hydro, fossil) Scenarios for Utility- Based Cogeneration
Basic Residential- cogeneration commercial network sector
Industrial sector Advanced cogeneration Combination network Results I
Base-case annual energy use
Base-case Elec- Gas & Oil & Coal Other Uran- Total energy use (PJ) tricity NGL's Petrol. ium Utility sector - - 14 286 - 640 940 Prov. (no util.) 477 824 782 21 158 - 2260 Province (total) 477 824 796 307 158 640 3200 % Reductions in values (Scenario A)
Utility sector - - 0 17 - 6.8 10 Prov. (no util.) 5.3 2.8 0.5 0 0.5 - 2.4 Province (total) 5.3 2.8 0.5 17 0.5 6.8 4.6 Results II
Base-case annual emissions to environment Material emissions (kilotons) Ther- Radi- mal ation Pollu (1015 SO NO CO CO Partic- VOC Spent 2 X 2 -tion Bq) (1000) ulates Uraniu (PJ) m Utility sector 321 92 32 4 11 0.5 1.04 591 11 Prov. (no utility) 1060 526 132 3500 837 775 - - - Province (total) 1380 618 164 3504 849 775 1.04 591 11 % Reductions in values (Scenario A) Utility sector 17 17 17 17 17 17 6.8 15 6.8 Prov. (no utility) 1.2 0.7 1.2 0.7 0.3 0.5 - - - Province (total) 4.9 3.2 4.2 0.8 0.5 0.5 6.8 15 6.8 Results III
Heat demand satisfied % reductions in some % of fuel by cogeneration (PJ yr-1) key utility parameters cogenerating for utility Scen- Residen- Indust- Total Coal Uran- Elec- Coal Uran- ario tial/ rial use ium tricity ium Commer use Produc- -cial tion A 46 0 46 17 7 5 12 8 B 206 0 206 41 30 24 77 49 C 0 26 26 13 3 3 6 4 D 0 54 54 16 5 6 13 2 E 46 26 72 20 9 8 22 12 F 206 54 260 47 35 30 100 49 Results IV
Annual reductions in health & environmental effects/costs
Cogen- Health effects Costs (million $) Environmental effects eration Mortality Mor- Lost Health Health and Yield loss (%) Lost scenario bidity work environment fishing Fish Crops (1000 (1000 days) days) Base 18.9-25.7 1,043 1,691 42.2 122.3 0.046 0.378 43.9
A 3.0-4.2 165 286 8.4 17.9 0.008 0.065 7.5 Implications
Utility-based cogeneration beneficial for Ontario:
substitute nuclear energy for other fuels
increase efficiency
reduce emissions and related health impacts
reduce energy consumption
reduce costs (observed elsewhere) Conclusions
Exergy can play significant role in understanding and increasing efficiency improving economics reducing environmental impact Exergy useful for nuclear energy systems nuclear cogeneration Exergy Recognition