Impact of Auxiliary Equipments’ Consumption on Electricity Generation Cost in Selected Power Plants of Pakistan

This study focuses on higher generation cost of electricity in selected TPPs (Thermal Power Plants) in Sindh, Pakistan. It also investigates the energy consumed by the auxiliary equipment of the selected TPPs in Sindh, Pakistan. The AC (Auxiliary Consumption) of selected TPPs is compared with that in UK and other developed countries. Results show that the AC in selected TPPs in Sindh, Pakistan exceeds the average AC of the TPPs situated in developed countries. Many energy conservation measures such as impeller trimming and de-staging, boiler feed pump, high voltage inverter, variable frequency drive, and upgrading the existing cooling tower fan blades with fiber reinforced plastic are discussed to overcome higher AC. This study shows that harnessing various available energy conservative measures the AC and unit cost can be reduced by 4.13 and 8.8%; also adverse environmental impacts can be mitigated. Results show that the unit cost of electricity can be reduced from Rs.20 to19/kWh in JTPP (Jamshoro Thermal Power Plant), Rs.9 to 8.8/kWh in GTPS (Gas Turbine Power Station) Kotri and Rs. 11 to 10.27/kWh in LPS (Lakhara Power Station). Thus, electricity production can be improved with the existing capacity, which will eventually assist to manage the current energy crisis and ensure its conservation.


INTRODUCTION
renewable energy sources [2] and its severity towards the environmental destruction is one of the major issues of recent research [3][4]. There are various alternative energy resources available through which world energy demands and its crisis could be coup up without affecting global environment. E nergy demand is increasing day by day all over the world due to rapid growth of population, enhanced standard of life and development in technologies [1]. Currently, about two-thirds of world's energy demand is accomplished by harnessing non-Pakistan is the 6th largest country by population which is over 190 million with GDP (Gross Domestic Production) growth rate of 4.4% and inflation rate of 1.8% [5]. Pakistan is facing electricity short fall of around 23.53-29.41% for last few years. This has negative effects on GDP that in turn causes various socio-economic and political problems. However, annual energy demand of Pakistan is increasing by about 4-5% and that will continue for coming 10 years. The share of different energy sources in electricity generation in Pakistan is oil (35.2%), hydel (29.9%), natural gas (29%), nuclear and others (5.8%) [6].
It is reported that in Pakistan about 67% of electricity is generated by TPPs based on fossil fuels, in which oil, gas and coal contributes 55.96, 43.94 and 0.1%, respectively in 2012-2013 [7][8].The energy efficiency of CCGT (Combine Cycle Gas Turbine) power plant is as low as 34.41% [9]. There are two major factors of this low efficiency; one is ageing of TPPs and the other is energy losses [10]. The low efficiency of most of the fossil fuel based power plants and higher line losses are estimated to be 23-25% that causes electric power shortfall and higher generation cost [11]. The generation of electricity from different resources in different countries is demonstrated in Fig. 1 [12][13][14].
In Fig. 1 the generation of electricity from various sources such as fossil fuel (oil, gas and coal), nuclear, hydel and other renewable in Pakistan is compared with other developed countries. It is clearly shown in Fig. 1 that most of the electricity is generated from fossil fuel i.e. greater than 65% in Pakistan. Notably, 35% of total electricity is produced from oil which is an expensive source and mostly imported. The coal is regarded as cheapest source for electricity production. However, abundant coal reserves are available in Pakistan yet its use in the country for electricity generation is less than 1%. Natural gas contributes about 30% in electricity production, greatly affecting the ample supply to domestic, commercial and industrial sectors of the country.
Consequently, the levelized cost of electricity is also remaining at higher side as compared to neighboring countries.

Auxiliary Consumption
In TPP the equipment that are not directly generating the power but are assisting in the process of power generation such as pumps, fans and compressors are known as auxiliary equipment and power consumed by them is called AC. It is reported that most of the fossil fuel fired TPPs in India have an efficiency ranging from 30-40% [10], which is lower than that in developed countries [14][15]. The decrease of energy conversion efficiency of TPPs in India is due to high consumption of auxiliary equipment that ranges from 6.5-8.5% [16,17].

Impact of Auxiliary Equipments' Consumption on Electricity Generation Cost in Selected Power Plants of Pakistan
In 2012 a case study shows that gas based power stations had an AC ranges from 1.4-1.8% while AC ranges from 6.5-9.6% in coal based power stations [18,19].

PROBLEM STATEMENT
The generation cost of electricity is high in selected TPPs of Sindh Pakistan due to multiple reasons which include high auxiliary consumption and use of costlier fuel.

OBJECTIVES
This paper aims to focus on the issue of generating electricity at higher price from fossil fuels. For this purpose, some TPPs in Sindh, Pakistan are taken as a case study.
The power consumption of the auxiliary equipment's in TPPs is considered. Finally, methods are devised to reduce higher consumption of auxiliary equipment in order to reduce unit cost of electricity generation and CO 2 emission from selected TPPs.

ELECTRICITY GENERATION COST
The electricity generation cost in Pakistan is high due to multiple reasons, including inefficient power plants and production of electricity from costly fuels. These two reasons contribute in raising the unit cost of electricity in Pakistan, while comparing with other developed countries as given in Table 1.
It is given in Table 1

Impact of Auxiliary Equipments' Consumption on Electricity Generation Cost in Selected Power Plants of Pakistan
Mehran

Jamshoro Thermal Power Station
JTPS is situated in Jamshoro district and fulfills the energy demand of interior Sindh. It consists of one 250MW Japan based furnace oil fired unit and three 200MW China based dual fired (i.e. Gas and Furnace Oil) units ( Table 2).
The data of JTPS for the month of July 2013 shows that 344.5GWh units of electricity was produced at a cost of Rs.6873.46 Million/month i.e. Rs. 19.95 per kWh [37]. It is shown in Fig. 2  The gross unit generated and AC of JTPS is given in Table 3 [38]. However, the efficiency of these units has been falling

Lakhra Power Station
LPS is situated inJamshoro district. It is the only power generation company based on coal in Pakistan. The installed capacity of LPS is 150 MW but unfortunately, out of three only one unit of 50MW capacity is operating.
The only operational unit has a capacity of 30MW while remaining two units are out of operation. All three units are based on coal, which is being recovered by  [39] primitive underground mining method from Lakhra coal mines, 25 kilometers from LPS. However, the gross electric power generated from LPS could be increased from 30-90MW by operating the closed units. It is reported that cost incurred on rehabilitation of closed unit is estimated around Rs.2 billion and it could be recovered with payback period of 9 month [40].

FIG. 3. GROSS UNIT GENERATED (GUG) AND AUXILIARY CONSUMPTION AT GTPS KOTRI
According to the available data for the month of October 2013, the total operating hours were calculated as 650hrs, during that nearly 13.78GWh units of electricity were generated with the expenditures on fuel cost as Rs.154.4 Million. Accordingly, levelized cost of the plant in that month is calculated as Rs.11.20 per kWh. Data shows that AC in LPS is around 27% which is higher than the permissible limits of the AC of coal based TPPs in developed countries.  (1) Retrofitting of various inefficient auxiliary equipment with most efficient one.

Impact of Auxiliary Equipments' Consumption on Electricity Generation Cost in Selected Power Plants of Pakistan
(2) Operating TPPs on optimum load factor.

Reduction in Generation Cost in Jamshoro Thermal Power Station
The AC in Jamshoro thermal power station contributes a major share towards the levelized cost of the plant.  Table 7.
The effects of different remedial measures on auxiliary consumption and unit cost of electricity generated in JTPS are given in Table 7. It is demonstrated in Fig. 4 that unit cost of electricity generated in JTPS is linearly related to its AC. The line in Fig. 4 shows the variation of unit cost generated in JTPS with variation of its AC within the prescribed limit AC in developed countries.

Reduction in Generation Cost in Gas Turbine Power Station Kotri
Since generation cost of electricity in GTPS Kotri is very high. It is mainly because of the fact that power consumption within the power plant is outside the acceptable limits. If the AC is decreased to the average AC  Table 8.
The effects of different remedial solution on AC and unit cost of electricity generated in GTPS are given in Table 8. The variation of unit cost with respect to AC of GTPS is demonstrated in Fig. 5. As seen in Fig. 5, the unit cost increases as the AC of GTPS increases. The present unit cost of electricity generated in GTPS Kotri can be reduced from Rs.9/-Rs.8.8/kWh by implementing the various remedial measures, which are given in Table   9.  cost of electricity are given in Table 9.
The effects of different remedial measures on AC and unit cost of electricity generated in LPS are given in Table   9. The variation of unit cost with AC of coal based thermal power plants is demonstrated on Fig. 6. As seen in Fig. 6 Implementing these measures will also help to increase output to a dependable capacity of the plant.

Overall Impacts on Generation Cost of Electricity Due to Recommendations
Here analysis is carried out to investigate the impacts of different proposed remedial measures on generation cost of electricity from fossil fuels and energy crisis in Pakistan.
It is estimated that based on different remedial measures As shown in Fig. 7 that present unit cost of electricity generated in selected TPPs is compared with its modified value of unit cost. As seen in Fig.7 that the maximum unit cost occurs in oil based TPP i.e. Rs.20/kWh, minimum  selected TPPs by enhancing their net electric output.

Impact of Auxiliary Equipments' Consumption on Electricity Generation Cost in Selected Power Plants of Pakistan
Therefore, it is concluded on the basis of Fig. 8  whereas CO 2 emission can be reduced by 5.9% in selected power plants.