Comparison of Thermal Power Plants' Efficiency

Thermal Power Plant Efficiency 

As thermal power plants had been proved effective in fulfilling the ever increasing demand, more and more research has been done to make them more efficient in every aspect to handle the complex demand of Electricity with ever increasing fuel prices and restriction due to environmental effects.

Major Thermal Power Plant Cycles

• Rankine Cycle(Steam Turbine Cycle)
• Brayton Cycle(Gas Turbine Cycle)
• Diesel Cycle(Diesel Engine Cycle)
• Otto Cycle( Gas Engine Cycle)
• Combine Cycle(Gas Turbine + Steam Turbine Cycle, Diesel/Gas Engine + Steam Turbine Cycle )

Started with Steam Cycle, efforts had been done to make it more efficient though with 

• Its inability to use working fluid(steam) temperature above 600 C.
• Its inability to handle fluctuating load demand.
• Its inability to erect in minimum time.
• Its inability to have low initial cost.

Research work shifted to other cycle like Brayton cycle and combined cycle. With Steam cycle, highest of efficiency has been achieved previously by Efforts like:

• Reheating( reheating the steam after first turbine wheel portion, to max possible temp.)
• Regeneration
• Combination of both.

But now super critical power plants of greater importance for steam cycle.

The efficiencies of Individual Type of Power Plant shall be discussed with reference to 

Following Diagram: 

 

Power Plant's Efficiency factors

Efficiency of  Power Plant 

Thermal Power Plant

Major Factor affecting the cost of thermal power plant:

2-Location

Thermal Power Plant unlike hydel power plant can be erected on more locations obviously because for hydel power station nature made route of rivers are interrupted to make a dam to produce electricity.
However, location of thermal power plant are carefully selected in feasibility reports. There are locations which are excluded for location of thermal power stations including flooded areas, places where earthquakes are frequent, electrical transmission and distribution cost is very important as it is very expensive, areas where weather doesn't go too harsh and too dynamic and soil structure etc.

3-Availability Of Water

Water is very important entity of power plant which in huge amount is used daily. So the location is selected where water is readily available in abundance. Hundreds of tons of water is needed in power plant each depending upon the capacity( MW ) and type of power plant( as steam turbine single need a huge amount of water as compared to gas turbine or diesel engine as in later two water is needed in cooling circuit which is close cycle circuit and only water lost in Cooling towers).

4-Water Quality 

Water available for power plant's usage should be better quality as the cost which would be spent to make it usable for the power plant usage, is entirely dependent upon its quality.
Quality means its turbidity, hardness, acidic salt and other salts which would be needed to be removed or lower their concentration to the level where they would be no longer harmful to the Closed water circuit material and other related equipment.

After plant erected, the running cost also depend how the equipment or personnel handling it. As if automatic valves which make the certain parameter(pH,hardness etc) to recommended value if fail to work then the manual handling could spend an additional value in the cost of chemical which are being used to maintain the quality of water.

5-Fluctuation of Electricity Load

This factor affects the running cost of power plant and is important to the low capacity (20MW to 300MW) supporting power plant as high capacity power plant aren't meant to run on fluctuating load demand.

The fuel cost when electricity load changes is highly affected because power producing machines are made to run on certain load on optimum efficiency while the efficiency in ramping up and down the load is significantly lower. That's why the fluctuation load affects the efficiency.

Efficiency Of Power Plants-1

Efficiency of Power Plant

Efficiency of power plant can be defined by how efficient a power plant converting the maximum possible power available to the electricity i.e potential and kinetic energy of water into electricity by hydel power plant and heat energy of steam into electricity by steam turbine.

Another meaning of efficiency which is more practical is installation and then running cost. Installation cost of hydel power station are highest while running cost is lowest with high rate to return while Combined cycle power plant has low installation cost while running cost is relatively high.

Robust Power Plant is another quality of efficient power plants. It meant plant capability to reach full load in minimum time. Combined cycle power plant are efficient in this criteria requiring only 1 hour or maximum of 2 hour to reach full base load while single cycle steam turbine power plant take up to 24 hours to reach full base load.

Thermal Power Plant

Efficiency of Thermal power plant depend upon many factors ranging from theoretical irreversibilities of the processes to geological and domestic factors. All these complexities end up to set a price/cost for per unit electricity. Major factors shall be discussed here.

Power plants can be classified depending upon the prime mover which is being used to drive the generator. This classification often set minimum level of efficiency for a power plant. However, the cost per unit of electricity is not entirely dependent upon this factor.

Overall final cost of single unit is dependent upon following major factor:
 

·        Fuel Cost

·        Location of Power Plant

·        Availability of Water

·        Quality Of Water

·        Fluctuation of Electrical Load

Fuel Cost
The cost of fuel is the major factor which often dominant others factors and also decide the type of power plant among thermal power plants (including nuclear power plant) including the prime mover( steam turbine, gas turbine, diesel engine etc) to be used. 

For example, coal power plants are not clean way to produce electricity efficiently and the system (conventional steam turbine and boiler system) which is used to produce electricity is not robust enough to tackle today’s challenge of fluctuating load demand. But still those countries with rich natural sources of coal or have nearby countries with these resources are considering to set-up these power plants.

With all these drawbacks, coal power plant are being erected only because their fuel cost is low enough to produce relatively cheap electricity.

Introduction To Power Plant

Power Plants

Types of Power Plants

There are some major types:

• Thermal Power Plant( Single cycle Steam Turbine power plant(Coal,Furnace Oil, Gas,Nuclear), Combined cycle Power Plant( Gas Turbine(Gas Turbine + Steam Turbine), Combined cycle Power Plant (Diesel/Gas/Furnace Engines + Steam Turbine).

• Hydel Power Plant ( Run of River, conventional Reservoir Type)(Francis,Kaplan and Pelton etc.)           
  
• Geo Thermal Power Plants (Geothermal energy to Electrical energy by steam turbine)
  
• Wind Power Plants (Kinetic Energy of Wind to Electrical energy)
• Solar Power Plants (Solar Energy to electrical Energy)
• Biomass Power Plant (Biomass heat energy to Electrical energy)

Apart from that there are many set-ups which are producing power of relatively of much lower proportion.

Hydel,Solar, Wind and Biomass famously are of Renewable resources of Energy and of next to nothing production of CO2 emissions. Among them hydel power plant is one major source of power production world wide. Almost all these sources of power production require high initial cost and hydel also require erection/construction time while running costs are relatively very low.

Thermal and geothermal are non-renewable energy resources and have major share in energy mix worldwide. Robust system with low erection time and relatively low initial cost. Running costs are relatively high but they are very good with fluctuating owing to their robust feature.

There are many types of power plant among which thermal and hydel power plant are of most important types as they produce most of world's electrical power.

Thermal power plants  burns some sort of fuel ( such fossil fuels or Nuclear) mainly to produce heat energy that is converted to mechanical energy in a primer mover(e.g Gas Turbine, Steam Turbine, Reciprocating Engine), which is further converted to Electrical Energy in a Electrical generator driven by the prime mover.

While hydel power plants convert potential energy and kinetic energy of water into electrical energy by a primer mover(e.g water turbine such Francis, Kaplan and pelton Turbine etc).

The Energy is supplied in electrical form as this form of energy has the least irreversibilities or losses.