13-Feb-19 Economics of Power Generation Economics of Power Generation Electricity consumption per capita is the index of living standard of people of that In whatever we do, energy plays an important role. country. There can be numerous energy resources. Country Electricity Consumption Human Development Index Choice of a particular energy resource depends on availability of energy resource and (kWh) per capita in 2018 (HDI) 2018 its life cycle cost. USA 12071 13 For example, for generation of electricity, there are two options: centralized or local China 4475 86 decentralized. Japan 7371 19 For centralized production lots of T&D infrastructure is required, there are advantages of ‘Economy of Scale’ and upkeep and maintenance is easy. Norway 26006 1 For local centralized production, there are no T&D hassles but there is O&M UAE 16195 34 requirements. India 1122 130 To choose between the two, economics of power generation needs to be assessed. Pakistan 405 150 Energy Mix in India (up to 31.10.2018) Economics of Power Generation India has fifth largest coal reserves in the world. Resource Installed capacity (MW) The problem with fossil fuel based power generation is scarcity concerns and environmental Thermal (coal) 195993 concerns (1 kWh electricity generated from coal, produces 0.94 kg of CO 2 ) . Thermal (gas) 24937 With current production and consumption level, proven coal reserves will last for 110 years, oil Thermal (oil) 838 reserves for 50 years and gas reserves for 52 years. Hydro 45487 To maintain ‘intergeneration equity’ there is dire need to reduce reliance on fossil fuel based Nuclear 6780 power generation and promote more and more renewable based power generation which is Renewable 72013 sustainable and at the same time environment friendly. Total 346048 1
13-Feb-19 CO 2 Emissions due to Electricity used in an Electric Geyser Carbon Dioxide Mitigation Potential of for a Single Bath Domestic Solar Water Heating System Details Energy Requirement Form of Energy Additional Parameters Rated Capacity of Domestic Solar Water Heating System (SWHS) = 200 litres /day Energy required to heat 30 kg (30 kg) (4.2 kJ/kg o C) Useful Energy Sp. Heat of water Initial temperature of water = 15 o C water from 15 o C- 40 o C (40-15) o C = 3150 kJ = 4.2 kJ/kg o C Design delivery temperature of water = 60 o C Electricity used by electric geyser 3150 / 0.95 Final Energy Efficiency of electric geyser = = 3316 kJ 0.95 Annual Capacity Utilization Factor for Domestic SWHS = 0.75 Electricity dispatched from the 3316 / (1- 0.15) Secondary Transmission and Distribution Density of water = 1000 kg / m 3 power plant = 3901 kJ Energy losses of electricity = 15% Annual useful energy delivered by the domestic SWHS Amount of energy contributed by 3901 / 0.4 Primary Energy Overall efficiency of coal coal at the thermal power plant = 9752 kJ thermal power plant = 40% = (0.75) (365 days/year) (200 kg/day) (4.2 kJ/kg o C) (60 – 15) o C Amount of Coal used 9752 kJ / 20000 kJ/kg ------ Lower heating value of Coal = 10347750 kJ per year = 0.488 kg = 20 MJ / kg Amount of CO 2 released (0.488) (0.6) (44/12) ------ Carbon fraction in Coal = 0.6 (100) = 1.073 kg Fraction of carbon oxidized = 1.0 Carbon Dioxide Mitigation Potential of Domestic Solar Water Heating System Economics of Power Generation It is assumed that prior to the installation of the domestic SWHS, the household uses an electric geyser (efficiency of electricity utilization = 95%) with the electricity being produced Technology Capital Cost ($/kW) Operating Cost ($/kWh) in a coal thermal power plant. Coal-fired combustion turbine $500 — $1,000 0.20 — 0.04 Transmission and Distribution losses of electricity = 15% Overall efficiency of coal utilization in coal thermal power plant = 40% Natural gas combustion turbine $400 — $800 0.04 — 0.10 Carbon fraction in coal used = 0.60 Coal gasification combined-cycle $1,000 — $1,500 0.04 — 0.08 Lower heating value of coal used = 20 MJ / kg (IGCC) Annual amount of coal saved due to use of domestic SWHS Natural gas combined-cycle $600 — $1,200 0.04 — 0.10 10347750 kJ 1601 kg of coal Wind turbine (includes offshore $1,200 — $5,000 Less than 0.01 ( 0 . 95 )( 1 0 . 15 )( 0 . 40 )( 20000 kJ / kg ) wind) Nuclear $1,200 — $5,000 0.02 — 0.05 Amount of CO 2 emissions likely to be mitigated annually = (1601.819) (0.6) (44/12) = 3524 kg of CO 2 Photovoltaic Solar $4,500 and up Less than 0.01 = 3.5 tonnes of CO 2 Hydroelectric $1,200 — $5,000 Less than 0.01 2
13-Feb-19 Economics of Power Generation Economics of Power Generation When planning a power plant, two basic parameters to be decided are: Total installed capacity can be determined from: Total installed capacity Maximum demand Size of the generating unit Growth of demand Reserve capacity required Load Curves for a Power Plant Economics of Power Generation The Load Curve is a Graph, which represents load on the generation station (the load is Size of generating unit depends on: in kW/MW) recorded at the interval of half hour or hour (time) Variation of load during 24 hours It is a curve which is drawn between loads versus time in sequential order. They are Maximum startup and shut down time drawn on daily basis data, weekly or monthly basis data. Maintenance programme Total capacity connected to the grid Plant efficiency versus size of unit Prize and space demand per kW versus size of unit 3
13-Feb-19 Load Duration Curves Load Curves for a Power Plant When the load elements of a load curve are arranged in the order of descending The Load Curve gives following Information: magnitudes, the curve thus obtained is called a load duration curve. The load duration curve is obtained from the same data as load curve but the ordinate The daily load curve shows the variation of load on the power station during different representing the maximum load is represented to the left and the decreasing loads are hours of the day. represented to the right in the descending order. The area under the daily load curve gives the number of unit generated in the day. Unit generated/day= Area (in kWh) under daily load curve. The highest point on the daily load curve represents the maximum demand on the station on that day. The area under the daily load curve divided by the total number of hours gives the average load on the station in that day. Area (in kWh) under the daily load curve Average load 24 hours Load Duration Curves Factors affecting cost of generation The load duration curve provides following useful information: Load factor The load duration curve readily shows the number of hours during which the given load Capacity factor has prevailed. Reserve factor The area under daily load duration curve (in kWh) will give the units generated on that Plant use factor day. Demand factor The load duration curve, helps to give information about annual load duration curve. Diversity factor 4
13-Feb-19 Factors affecting cost of generation Plant Load Factor Load factor : Plant Load factor : The ratio of number of units actually generated in a given period to number of units which It is a measure of average capacity utilization. If the PLF is affected by non-availability of could have been generated with the same maximum demands is called as load factor for fuel, maintenance shut-down, unplanned break down and no offtake (as consumption the station. pattern fluctuates lower in nights), the generation has to be adjusted. A power (electricity) storage is not feasible. Generation of power is controlled to match the offtake. For any OR such duration, a power plant generates below its full capacity. To that extent it is a capacity loss. The Ratio of Average Load to the Maximum Demand during a given period is known as load factor. Average load • Higher the load factor, greater is the total output. Load factor Peak load • A power plant shall be less efficient at lower load factors • A high load factor means fixed costs are spread over more kWh of output. kWh generated in an year Load factor max kW 8760 Plant Load Factor in India Factors affecting cost of generation Plant Load factor : Capacity factor The Plant Capacity Factor is the ratio of average demand on the Power Station divided by Year National PLF (Coal) NTPC PLF (Coal) the maximum installed capacity of the power station. (In percentage) (In percentage) 2007-08 78.5 92.2 OR It is the ratio of actual energy produced to the maximum possible energy that could have 2008-09 77.2 91.1 been produced during a given period. 2009-10 77.5 90.8 Average load Capacity factor 2010-11 75.1 88.3 Rated capacity of the plant 2011-12 73.3 85.0 kWh 2012-13 70.0 83.0 generated Capacity factor kW 8760 installed 2013-14 64.62 79.14 5
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