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Energy Engineering Fundamentals (EN 110) SB/2024 Energy Engineering Fundamentals (EN 110) SB/2024 Outline...

Energy Engineering Fundamentals (EN 110) SB/2024 Energy Engineering Fundamentals (EN 110) SB/2024 Outline Topics Lectures Topic 6 -Power system 11 (Sept. 23, -Power plants 24, 26, 30, -Electricity tariff Oct. 1, 3, 7, 8, 10, 14, -Power factor 15) Electrical Systems -Power generation -Gas turbine cycle -Steam turbine cycle -Combined cycle and cogeneration -Solar thermal 1 2 Energy Engineering Fundamentals (EN 110) SB/2024 Energy Engineering Fundamentals (EN 110) SB/2024 System Load Time intervals – daily, weekly, seasonal, annual, etc. Power System Usage – Residential, industrial, commercial, agricultural, etc. End-usage – Lighting, air conditioning, pumping, etc. 3 4 EN 110 Notes 1  Energy Engineering Fundamentals (EN 110) SB/2024 Energy Engineering Fundamentals (EN 110) SB/2024 Load Curve Annual Load Curve Graphical representation of electrical load (i.e., power) as a function of time The area under the curve represents the energy requirement 20 Important for plant 15 Demand (kW) operation 10 (preparation, 5 take-off, shut down, 0 0 2 4 6 8 10 12 14 16 18 20 22 24 coordination, etc.) Time (hour of the day) 5 6 Energy Engineering Fundamentals (EN 110) SB/2024 Energy Engineering Fundamentals (EN 110) SB/2024 Typical Load Curves Understand Load Curve Industrial plant with single shift Commercial shops Partial peak Demand Demand Demand Off-peak Off-peak time time Urban load curve Street lighting Evening Morning peak peak Demand Demand time time 7 Time of the day 8 EN 110 Notes 2  Energy Engineering Fundamentals (EN 110) SB/2024 Energy Engineering Fundamentals (EN 110) SB/2024 Load curve of a typical day – Delhi Load curve of a typical day – Delhi https://www.delhisldc.org/Loadcurve.aspx?Loc=0805 https://www.delhisldc.org/Loadcurve.aspx?Loc=0805 9 10 Energy Engineering Fundamentals (EN 110) SB/2024 Energy Engineering Fundamentals (EN 110) SB/2024 Peak and Average Load System Load Factor Peak load System load factor (Load factor) – maximum demand – Defined as: average load/peak load – Growth of peak load – Pertaining to the demand capacity addition – Represents the variation in the demand Capital cost investment – One of the planning objectives is to increase Average load system load factor – total energy/time duration – Operating cost, as it is related to energy 11 12 EN 110 Notes 3  Energy Engineering Fundamentals (EN 110) SB/2024 Energy Engineering Fundamentals (EN 110) SB/2024 Capacity Factor Capacity Factor: Typical Values Capacity factor (Plant load factor, PLF) – average load/plant capacity – Total energy produced/maximum energy production possible – Pertaining to the generating plant – Represents the part load operation – Efficient utilization of the plant Steam-based power plants: 40 % ― 95 % – Representative operating cost of the plant Gas turbine: 20 % ― 80 % Wind farms: 20 % ― 60 % – Recovery potential of invested capital Photovoltaic: 15 % ― 30 % Hydro-electric: 10 % ― 99 % 13 14 Energy Engineering Fundamentals (EN 110) SB/2024 Energy Engineering Fundamentals (EN 110) SB/2024 Load & Capacity Factors Load & Capacity Factors Load factor and capacity factor ≤ 1 Load curve, normalized with respect to the Inadequate utilization of installed capacity peak load and total duration, represents Part load operation of the plant load factor when integrated Reduction in efficiency (as part load Load curve, normalized with respect to the efficiency is poor) implying more fuel plant capacity and total duration, consumption (and higher operating cost) represents the average capacity factor when integrated Rapid rate of increase of load may cause system instability 15 16 EN 110 Notes 4  Energy Engineering Fundamentals (EN 110) SB/2024 Energy Engineering Fundamentals (EN 110) SB/2024 Utilization Factor Connected Load & Diversity Factor Connected Load Utilization factor – sum of the continuous (or nameplate) ratings – Peak load/plant capacity of equipment. – Extent up to which plant capacity is utilized to Demand factor satisfy the peak demand – Peak load/connected load – Related to the reliability of the power system Diversity factor – Helps in planning capacity addition – Sum of individual peak load/actual peak load Reserve factor – Helps in improving load factor and economic – Load factor/capacity factor operation – Inverse of utilization factor – Inverse of diversity factor is coincidence factor 17 18 Energy Engineering Fundamentals (EN 110) SB/2024 Energy Engineering Fundamentals (EN 110) SB/2024 Diverse Load Curves Total Power Plants Shop Industry Residential 19 20 EN 110 Notes 5  Energy Engineering Fundamentals (EN 110) SB/2024 Energy Engineering Fundamentals (EN 110) SB/2024 Power Plants: Dispatchability Dispatchable Power Plants Dispatchable power plants Benefits of dispatchable power plants – Power plants that can generate and dispatch power – Provides spinning reserve on demand Helps in frequency control and enhance reliability – Coal, natural gas, nuclear power plants – Balances the electric power system – Renewables such as hydro, biomass, geothermal are Helps in following load dispatchable – Optimum dispatch strategy Non-Dispatchable power plants Reduction in operating costs and environmental – Operators do not have control over the generation pollution and dispatch of power – Wind and solar – Can be converted to dispatchable using storage (cost increases) 21 22 Energy Engineering Fundamentals (EN 110) SB/2024 Energy Engineering Fundamentals (EN 110) SB/2024 Peak Load Power Plants Base Load Power Plants Peak load power plant Base load power plant – Plants used for a small fraction of time – Runs almost throughout the year – Operating cost is not very important – Operating costs should be very low – Capital investment should be low – Capital investment may be high – Low start-up time – Coal plants, nuclear plants, etc. – Response time should be very fast Intermediate power plant – Gas turbine, small hydro, etc. – Both capital and operating costs are important – Combined cycle, cogeneration, etc. 23 24 EN 110 Notes 6  Energy Engineering Fundamentals (EN 110) SB/2024 Energy Engineering Fundamentals (EN 110) SB/2024 Non-dispatchable Power Plants Non-dispatchable Power Plants Non-Dispatchable power plant Non-dispatchable power plant – Variable power pants, Intermittent power plants – Low carbon footprints – Solar, wind based renewable plants – Ramp up with polluting peak plant – Production varies with resource variations – Transmission line construction – high variability (low reliability) – Good for distributed generation – low capacity factor – high capital cost – Do not match with load curves – Storage is an option, cost increases 25 26 Energy Engineering Fundamentals (EN 110) SB/2024 Energy Engineering Fundamentals (EN 110) SB/2024 Electricity Tariff Residential - Block - Energy charge Agricultural – Horsepower Industrial – Two part –Energy, Demand Commercial – Block Electricity Tariff Public Works 28 EN 110 Notes 7  Energy Engineering Fundamentals (EN 110) SB/2024 Energy Engineering Fundamentals (EN 110) SB/2024 Electricity Tariff-Components Maximum demand Charges Energy Charges Power factor penalty or bonus rates Fuel cost adjustment charges Electricity duty charges levied w.r.t units consumed Meter rentals Time Of Day (TOD) Power Factor Penalty for exceeding contract demand Surcharge if metering is at LT side in some of the utilities 29 Energy Engineering Fundamentals (EN 110) SB/2024 Energy Engineering Fundamentals (EN 110) SB/2024 Representation in Phasor diagram Basics of Power e j  cos  j sin  Imaginary or j axis V  V P (t )  v (t )i (t )  2V cos(t   ) 2 I cos(t   ) I  I  2VI cos(t   ) cos(t   ) 2 cos A cos B  cos( A  B )  cos( A  B )   P (t )  VI cos(   )  VI cos( 2t     ) Real Axis Constant w.r.t time Sinusoidally varying 31 w.r.t time 32 EN 110 Notes 8  Energy Engineering Fundamentals (EN 110) SB/2024 Energy Engineering Fundamentals (EN 110) SB/2024 Basics of Power Power terms T P 1 P  T  0 p ( t ) dt S  VI kVA  Q P  VI cos kW S  VI cos(   ) QVIsin kVAr cos(   ) Power factor S – Apparent Power    Phase angle difference between V and I S  P 2  Q 2 P – Active Power power factor angle Q – Reactive Power 33 34 Energy Engineering Fundamentals (EN 110) SB/2024 Energy Engineering Fundamentals (EN 110) SB/2024 Power factor correction P Capacitor rating =Q1-Q2  2  1 S2 Q2 Power Generation  P(tan(1)  tan( 2))kVar S1 Q1 Maximum Demand Saving = S1-S2 kVA 35 EN 110 Notes 9  Energy Engineering Fundamentals (EN 110) SB/2024 Energy Engineering Fundamentals (EN 110) SB/2024 Power Generation: Thermal Route Fuel Fossil Fuel Conditioning Combustion Fission Biomass Concentration Nuclear Solar Power Gas Turbine Cycle Electrical Energy Thermal Energy Cycles Thermal Power Plants Thermodynamic cycles Working fluids 37 Energy Engineering Fundamentals (EN 110) SB/2024 Energy Engineering Fundamentals (EN 110) SB/2024 Gas Turbine Cycle Ideal Brayton Cycle Simple gas turbine plants are open cycle. Also called Ideal cycle consists of compressor, combustion combustion turbine chamber and turbine For analysis: close loop approximations are made Energy balance equations Tmax 3 Represented as Brayton (or Joule-Brayton) cycle Qin  mc p (T3  T2 ) Wt Qin – George Brayton first proposed the cycle in 1870 Qout  mc p (T4  T1 ) 2 4 – Consists of two isentropic work transfer processes Temperature-pressure Wc and two constant pressure heat transfer processes  1 Qout T3 T2  P2    1      rp   Tmin 1 Simplified analysis is with air-standard assumption: – Air is working fluid T4 T1  P1  Entropy – Closed loop cycle Efficiency and Power  T   – Air is an ideal gas with constant properties   1 1 and w   3 1  1   rp( 1) /   1 – Combustion and fuel has no effect rp( 1) /  c pT1  T1  rp( 1) /    – Cycle is internally reversible 39 40 EN 110 Notes 10  Energy Engineering Fundamentals (EN 110) SB/2024 Energy Engineering Fundamentals (EN 110) SB/2024 Brayton Cycle: Modifications Modified Brayton Cycle intercooler reheater Increase in specific work output Process flow diagram 2 3 6 7 8 5 Intercooling: cooling of combustion air in between two of regenerative-reheat- compressors intercooling cycle 4 9 1 – Small increase in cycle efficiency 10 regenerator – Not used in gas turbine plants, used in stand-alone 6 compressor systems Tmax 8 Reheating: heating of combusted gas to high temperature (through another combustion chamber) in T-s diagram 7 9 5 between two turbines 4 10 – Slight decrease in cycle efficiency 3 2 Increase in efficiency Tmin 1 Regeneration: recovery of heat from turbine exit to increase the temperature of combustion air Entropy 41 42 Energy Engineering Fundamentals (EN 110) SB/2024 Energy Engineering Fundamentals (EN 110) SB/2024 Regenerator Brayton Cycle: Non-idealities Regenerators are gas-to-gas heat exchangers. actual work Tin  Tout Low heat transfer coefficient demands large heat Turbine efficiency: T   ideal work Tin  Tout , s transfer area Its heavy and have large pressure drop ideal work Tout , s  Tin Compressor efficiency: C   Used only for stationary power plant and not in moving actual work Tout  Tin plant Pressure drop at inlet, regenerator, combustion chamber, Maximum temperature depends on the material used. exit etc. For stainless steel, it is around 900K Effectiveness: actual heat transfer to maximum possible heat transfer 𝜖 = = Effectiveness of regenerators for most modern gas turbine plants are in the range: 0.85-0.9 43 44 EN 110 Notes 11  Energy Engineering Fundamentals (EN 110) SB/2024 Energy Engineering Fundamentals (EN 110) SB/2024 Steam Power Cycle Simple plant has ideal Rankine cycle Consists of two isentropic work transfer processes and two constant pressure heat transfer processes – Thermodynamically equivalent to Brayton cycle. Steam Turbine Cycle Working fluid is different 5 5 Qin 3 Wt 4 4 6 2 Wp 3 6 1 Qout 2 1 Entropy 46 Energy Engineering Fundamentals (EN 110) SB/2024 Energy Engineering Fundamentals (EN 110) SB/2024 Modified Carnot Cycle Rankine Cycle: Calculation To avoid pumping two- 5 phase fluid, condense to Basic equations: Qin 3 saturated liquid Qin  mh5  h2  4 W t 2 During expansion, liquid Qout  mh6  h1  Wp droplets are formed WT  mh5  h6  1 Qout 6 These droplets can WP  mh2  h1   mv1  p 2  p1  damage turbine blades Entropy Enthalpies and other properties to be read from steam due to corrosion and table impact Turbine and pump efficiencies, pressure drops, etc. can Superheating the vapor Entropy be taken into account It can also increase the Dryness fraction at state 6 should be more than 0.8 thermal efficiency of the Steam rate is approximately 1 kg/s/MW cycle 47 48 EN 110 Notes 12  Energy Engineering Fundamentals (EN 110) SB/2024 Energy Engineering Fundamentals (EN 110) SB/2024 Reheat Cycle Regeneration Cycle One reheater may be employed between turbines Steam extracted or bled from the turbine used Optimal pressure ratio is 0.2-0.3 for feed water heating 3-4 percentage point improvement in efficiency Feed water heater Reduction in specific work output 5 5 Improvement in cycle efficiency 3 7-13 feed heaters are used in modern power 4 4 2 plant 6 10-13% improvement in cycle efficiency has 3 1 6 been reported. 2 1 Entropy 49 50 Energy Engineering Fundamentals (EN 110) SB/2024 Energy Engineering Fundamentals (EN 110) SB/2024 Deaerator Removal of dissolved gases to avoid corrosion Combined Cycle 51 EN 110 Notes 13  Energy Engineering Fundamentals (EN 110) SB/2024 Energy Engineering Fundamentals (EN 110) SB/2024 Combined Cycle Combined Cycle Combining two or more basic thermodynamic cycles Brayton Cycle Heat rejected by one is utilized by other Range of temperature increases and overall efficiency Plant a b c d Rankine Cycle Topping + bottoming cycle Tmax (avg) K 1000 600 680 1000 Most popular Brayton + Tmin (avg) K 520 300 300 300 Rankine Cycle, connected Efficiency (%) 48 50 56 70 through heat recovery steam generator (HRSG) CC  T   B  T B 53 54 Energy Engineering Fundamentals (EN 110) SB/2024 Energy Engineering Fundamentals (EN 110) SB/2024 Utility Options PROCESS Electricity Heat Cogeneration Electricity Heat Fuel Heat BOILER CHP Plant Electricity Fuel Power Plant Fuel SHP Cogeneration 55 56 EN 110 Notes 14  Energy Engineering Fundamentals (EN 110) SB/2024 Energy Engineering Fundamentals (EN 110) SB/2024 Cogeneration for Industry Self generated electricity in Chemical Process Industry– 42% of total electricity demand of which 86% from cogeneration plants Average price – only 57% of grid price Solar Thermal Purchased electricity declining (-0.4%), self generated electricity increasing at 21.3% per year Evaluate viability of Cogeneration If heat/power loads small-Cogeneration for group of industries 57 58 Energy Engineering Fundamentals (EN 110) SB/2024 Energy Engineering Fundamentals (EN 110) 60 SB/2024 Solar Thermal/PV National Solar Thermal Power Testing, Simulation and Research Facility 1 MWe Solar Thermal Power Plant National Test Facility Development of Simulation Package Integration of two different solar thermal technologies Industrial consortium 59 EN 110 Notes 15  Energy Engineering Fundamentals (EN 110) SB/2024 Further Readings W.D. Marsh, Economics of electric utility power generation, Clarendon Press, 1980 P.K. Nag, Power Plant Engineering, Tata McGraw-Hill Education, 2002 Schlabbach, J. and Rofalski, K.H., 2014. Power system engineering: planning, design, and operation of power systems and equipment. John Wiley & Sons. Seifi, H. and Sepasian, M.S., 2011. Electric power system planning: issues, algorithms and solutions. Berlin: Springer. R.W.Haywood, Analysis of Engineering Cycles, 4th Edition, Pergamon Press, Oxford, 1991 A.B.Gill, Power Plant Performance, Butterworths, 1984 Desai N.B., S. Bandyopadhyay, Energy, 34(10), 1674-1686, 2009 S. Bandyopadhyay, N. C. Bera, S. Bhattacharyya, Energy Conver & Mgmt, 42(3), 359- 371, 2001 D. Lane, “Brayton Cycle: The Ideal Cycle for Gas-Turbine Engines in Relation to Power Plants,” available at http://web.me.unr.edu/me372/Spring2001/Brayton%20Cycle.pdf T. Heppenstall, Advanced gas turbine cycles for power generation: a critical review, Applied Thermal Engineering 18 (1998) 837-846 S.P. Mavromatis, A.C. Kokossis, Hardware composites: A new conceptual tool for the analysis and optimisation of steam turbine networks in chemical process industries. Part I: principles and construction procedure, Chem Eng Science, 53(7), 1405-1434, 1998 A.B.Gill, Power Plant Performance, Butterworths, 1984 A. Bejan, Advanced Engineering thermodynamics, John Wiley, 1988 61 EN 110 Notes 16