SOLAR POWER TOWER SOLAR POWER TOWER TECHNOLOGYTECHNOLOGY

Presented by:Presented by:Lokesh KumarLokesh Kumar

77THTH SEM, Electrical SEM, Electrical09012235190901223519

CONTENTSCONTENTS

IntroductionIntroduction Overview on SPTTOverview on SPTT HistoryHistory System DescriptionSystem Description Rankine's cycleRankine's cycle Benefits of SPTTBenefits of SPTT Advantages & DisadvantagesAdvantages & Disadvantages ApplicationsApplications ConclusionsConclusions

Introduction Solar power towers generate electric power from sunlight by Solar power towers generate electric power from sunlight by

focusing concentrated solar radiation on a tower-mounted heat focusing concentrated solar radiation on a tower-mounted heat exchanger (receiver).exchanger (receiver).

It uses an array of flat, moveable mirrors (called heliostats) to It uses an array of flat, moveable mirrors (called heliostats) to focus the sun's rays upon a collector tower (the target).focus the sun's rays upon a collector tower (the target).

The high energy at this point of concentrated sunlight is The high energy at this point of concentrated sunlight is transferred to a substance that can store the heat for later use. transferred to a substance that can store the heat for later use.

The more recent heat transfer material that has been successfully The more recent heat transfer material that has been successfully demonstrated is liquid sodium.demonstrated is liquid sodium.

Sodium is a metal with a high heat capacity, allowing that energy to Sodium is a metal with a high heat capacity, allowing that energy to be stored and drawn off throughout the evening.be stored and drawn off throughout the evening.

Stored energy can be used to boil water for use in steam turbines.Stored energy can be used to boil water for use in steam turbines.

OverviewOverviewThe largest power towers ever built are the 10 MW (Solar One and The largest power towers ever built are the 10 MW (Solar One and Solar Two plants). Assuming success of the Solar Two project, the Solar Two plants). Assuming success of the Solar Two project, the next plants could be scaled-up to between 30 and 100 MW.next plants could be scaled-up to between 30 and 100 MW.

As non-polluting energy sources become more favored, molten-salt As non-polluting energy sources become more favored, molten-salt power towers will have a high value because the thermal energy power towers will have a high value because the thermal energy storage allows the plant to be dispatch able.storage allows the plant to be dispatch able.

The value of power is worth more because a power tower plant can The value of power is worth more because a power tower plant can deliver energy during peak load times when it is more valuabledeliver energy during peak load times when it is more valuable

New peaking and intermediate power sources are needed today in New peaking and intermediate power sources are needed today in many areas of the developing World. many areas of the developing World.

One possible concern with the technology is the relatively high One possible concern with the technology is the relatively high amount of land and water usage.amount of land and water usage.

HistoryHistorySolar technology is not new process. Its history spans from the 7thCentury Solar technology is not new process. Its history spans from the 7thCentury B.C. to today. We started out concentrating the sun’s heat with glass and B.C. to today. We started out concentrating the sun’s heat with glass and mirrors to light fires. Today, we have everything from solar-powered mirrors to light fires. Today, we have everything from solar-powered buildings to solar powered vehicles.buildings to solar powered vehicles.

Solar One, which operated from 1982 to 1988, was the world’s largest Solar One, which operated from 1982 to 1988, was the world’s largest power tower plant. It proved that large-scale power production with power power tower plant. It proved that large-scale power production with power towers was feasible. towers was feasible.

During the operation of Solar One, research began on the more advanced During the operation of Solar One, research began on the more advanced molten-salt power tower design described. This development culminated in molten-salt power tower design described. This development culminated in the Solar Two project.the Solar Two project.

Solar Two, which is currently going through its startup phase, will generate Solar Two, which is currently going through its startup phase, will generate (in addition to electric power) information on the design, performance, (in addition to electric power) information on the design, performance, operation and maintenance of molten-salt power towers.operation and maintenance of molten-salt power towers.

Solar Two is expected to begin routine daily power production in late 1997.Solar Two is expected to begin routine daily power production in late 1997.

System DescriptionSystem DescriptionSolar power tower convert sunshine into clean electricity. The technology Solar power tower convert sunshine into clean electricity. The technology uses many large, sun-tracking mirrors commonly referred as heliostats to uses many large, sun-tracking mirrors commonly referred as heliostats to focus sunlight on a receiver at the top of a tower.focus sunlight on a receiver at the top of a tower.

The enormous amount of energy, coming out of the sun rays, concentrated The enormous amount of energy, coming out of the sun rays, concentrated at one point (the tower in the middle), produces temperatures of approx. at one point (the tower in the middle), produces temperatures of approx. 550°C to 1500°C.550°C to 1500°C.

The gained thermal energy can be used for heating water or molten salt, The gained thermal energy can be used for heating water or molten salt, which saves the energy for later use. Heated water converts to steam, which saves the energy for later use. Heated water converts to steam, which is used to move the turbine-generator. This way thermal energy is which is used to move the turbine-generator. This way thermal energy is converted into electricity.converted into electricity.

Water is the oldest and simplest way for heat transfer. But the difference is Water is the oldest and simplest way for heat transfer. But the difference is that the method in which molten salt is used, allows storing the heat when that the method in which molten salt is used, allows storing the heat when the sun is behind clouds or even at night. the sun is behind clouds or even at night.

Continued….Continued….As already mentioned there are two main fluids which are used for the heat As already mentioned there are two main fluids which are used for the heat transfer, water and molten salt. transfer, water and molten salt.

If water is used as Heat transfer fluid then it is If water is used as Heat transfer fluid then it is First generation of First generation of solar power tower plant. (i.e. Solar One)solar power tower plant. (i.e. Solar One)

If Molten salt is used as Heat transfer fluid then it is If Molten salt is used as Heat transfer fluid then it is Next generation Next generation of solar power tower plant. (i.e. Solar Two)of solar power tower plant. (i.e. Solar Two)

HELIOSTATHELIOSTAT• Heliostat is termed Greek word Heliostat is termed Greek word

Helios- sunHelios- sun

stat - stationarystat - stationary• A Heliostat is a device that tracks the movement of the sun.A Heliostat is a device that tracks the movement of the sun.• The reflected sunlight from the heliostats can generate an enormous The reflected sunlight from the heliostats can generate an enormous

amount of heat if all are oriented towards the same target. amount of heat if all are oriented towards the same target. • These are also called as sun tracking mirrors.These are also called as sun tracking mirrors.

Solar oneSolar oneSolar One was the world’s largest power tower plant. In that plant, Solar One was the world’s largest power tower plant. In that plant, water was converted to steam in the receiver and used directly for water was converted to steam in the receiver and used directly for conventional Rankine-cycle steam turbine to generate power. conventional Rankine-cycle steam turbine to generate power.

The Solar One thermal storage system works by storing heat in the The Solar One thermal storage system works by storing heat in the form of steam generated using solar energy in a tank which is filled form of steam generated using solar energy in a tank which is filled with rocks and sand and using oil as the heat-transfer fluid. with rocks and sand and using oil as the heat-transfer fluid.

The Solar One thermal storage system extended the power The Solar One thermal storage system extended the power generation capability of the plant into the night and provided heat for generation capability of the plant into the night and provided heat for generating low-grade steam for keeping parts of the plant warm generating low-grade steam for keeping parts of the plant warm during off-hours and for morning startup. during off-hours and for morning startup.

Disadvantage of solar one technologyDisadvantage of solar one technology Solar One thermal storage system was complex and Solar One thermal storage system was complex and

thermodynamically inefficient. thermodynamically inefficient. Solar One also showed the disadvantages of a water/steam system, Solar One also showed the disadvantages of a water/steam system,

such as the intermittent operation of the turbine due to cloud such as the intermittent operation of the turbine due to cloud transience and lack of effective thermal storage. transience and lack of effective thermal storage.

Solar TwoSolar TwoThe conversion of Solar One to Solar Two required a new (molten-salt) heat The conversion of Solar One to Solar Two required a new (molten-salt) heat transfer system and a new control system. This includes the receiver, transfer system and a new control system. This includes the receiver, thermal storage, piping, and a steam generator.thermal storage, piping, and a steam generator.

The Solar Two power tower is composed of a series of panels (each made The Solar Two power tower is composed of a series of panels (each made of 32 thin-walled), stainless steel tubes, through which the molten salt flows of 32 thin-walled), stainless steel tubes, through which the molten salt flows in a serpentine path.in a serpentine path.

A black Pyromark paint which is robust, resistant to high temperatures and A black Pyromark paint which is robust, resistant to high temperatures and thermal cycling and absorbs 95% of the incident sunlight is used to coat the thermal cycling and absorbs 95% of the incident sunlight is used to coat the external surfaces of the tubes.external surfaces of the tubes.

The design including laser-welding, a tube clip design that facilitates tube The design including laser-welding, a tube clip design that facilitates tube expansion and contraction, and non-contact flux measurement devices, expansion and contraction, and non-contact flux measurement devices, allows the receiver to rapidly change temperature without being damaged. allows the receiver to rapidly change temperature without being damaged.

Advantages of Using Molten Advantages of Using Molten

Salt Salt A variety of fluids were tested to transport the sun's heat, A variety of fluids were tested to transport the sun's heat,

including water, air, oil, and sodium. In that, molten salt was including water, air, oil, and sodium. In that, molten salt was selected as best. selected as best.

Molten salt is an efficient, low cost medium to store thermal Molten salt is an efficient, low cost medium to store thermal energy.energy.

Molten salt operating temperatures are compatible with today’s Molten salt operating temperatures are compatible with today’s high-pressure and high-temperature steam turbines.high-pressure and high-temperature steam turbines.

it is non-flammable and nontoxic. it is non-flammable and nontoxic.

Rankine cycleRankine cycle

A Rankine cycle describes a model of the operation of steam heat engines A Rankine cycle describes a model of the operation of steam heat engines most commonly found in power generation plants. Common heat sources most commonly found in power generation plants. Common heat sources for power plants using the Rankine cycle are liquid salts, natural gas, oil for power plants using the Rankine cycle are liquid salts, natural gas, oil etc.etc.

The working fluid in a Rankine cycle follows a closed loop and is re-used constantly.

The Rankine cycle is a thermodynamic cycle which converts heat into The Rankine cycle is a thermodynamic cycle which converts heat into work. The heat is supplied externally to a closed loop, which usually uses work. The heat is supplied externally to a closed loop, which usually uses water as the working fluid. This cycle generates about 80% of all electric water as the working fluid. This cycle generates about 80% of all electric power used throughout the worldpower used throughout the world

Continued….Continued…. There are four processes in the Rankine cycle, each changing There are four processes in the Rankine cycle, each changing

the state of the working fluid.the state of the working fluid.

The working fluid is pumped from low to high pressure, as the The working fluid is pumped from low to high pressure, as the fluid is a liquid at this stage the pump requires little input energy. fluid is a liquid at this stage the pump requires little input energy.

    The high pressure liquid enters a boiler where fluid is heated at The high pressure liquid enters a boiler where fluid is heated at constant pressure by an external heat source to become a dry constant pressure by an external heat source to become a dry saturated vapor. saturated vapor.

   The dry saturated vapor expands through a turbine, generating The dry saturated vapor expands through a turbine, generating power. This decreases the temperature and pressure of the vapor, power. This decreases the temperature and pressure of the vapor, and some condensation may occur. and some condensation may occur.

The wet vapor then enters a condenser where it is condensed at The wet vapor then enters a condenser where it is condensed at a constant pressure and temperature to become a saturated liquid.. a constant pressure and temperature to become a saturated liquid..

Benefits of Solar Power TowersBenefits of Solar Power TowersSolar power towers are fueled by sunshine and do not Solar power towers are fueled by sunshine and do not release greenhouse gases. release greenhouse gases.

Solar power towers are unique among solar electric Solar power towers are unique among solar electric technologies in their ability to efficiently store solar technologies in their ability to efficiently store solar energy and dispatch electricity to the grid when needed, energy and dispatch electricity to the grid when needed, even at night or during cloudy weather. even at night or during cloudy weather.

  

Environmental Benefits of Solar Power TowersEnvironmental Benefits of Solar Power Towers No hazardous gaseous or liquid emissions are released No hazardous gaseous or liquid emissions are released

during operation of the solar power tower plant.during operation of the solar power tower plant. Salt can be recycled if necessary.Salt can be recycled if necessary. If the power tower is hybridized with a conventional fossil If the power tower is hybridized with a conventional fossil

plant, emissions will be released from the non-solar plant, emissions will be released from the non-solar portion of the plant.portion of the plant.

Continued….Continued….

Metal Corrosion in the Molten-Salt EnvironmentMetal Corrosion in the Molten-Salt Environment All pipes, valves and vessels for hot salt were All pipes, valves and vessels for hot salt were

constructed from stainless steel because of its corrosion constructed from stainless steel because of its corrosion resistance in the molten-salt environment, while the cold-resistance in the molten-salt environment, while the cold-salt system is made from mild carbon steel. salt system is made from mild carbon steel.

Advantages of SPTTAdvantages of SPTTSolar energy comes directly from the sun it is not only renewable, but also Solar energy comes directly from the sun it is not only renewable, but also accessible in any part of the world. accessible in any part of the world.

  

Solar power is also one of the cleanest forms of energy, since it creates no Solar power is also one of the cleanest forms of energy, since it creates no pollution, and produces no greenhouse gases or waste products.pollution, and produces no greenhouse gases or waste products.

Solar Power is safer alternative to WIND & HYDRO POWER.Solar Power is safer alternative to WIND & HYDRO POWER.

Not only solar energy is non-pollutant, in terms of gases, but it also causes Not only solar energy is non-pollutant, in terms of gases, but it also causes zero noise pollution – since there are no moving parts in any of the devices zero noise pollution – since there are no moving parts in any of the devices which are used to capture the sunlight.which are used to capture the sunlight.

Maintenance costs are low as well – only occasional cleaning and periodic Maintenance costs are low as well – only occasional cleaning and periodic battery replacements are needed.battery replacements are needed.

Most manufacturers of solar panels provide twenty-year warranties for their Most manufacturers of solar panels provide twenty-year warranties for their equipment, guaranteeing long-life operation.equipment, guaranteeing long-life operation.

DisadvantagesDisadvantagesThe most obvious drawback of solar energy is its sole dependence on The most obvious drawback of solar energy is its sole dependence on the sun.  Once the weather becomes cloudy or night time strikes, energy the sun.  Once the weather becomes cloudy or night time strikes, energy collection comes to a halt.  collection comes to a halt.  

Solar panels can also be expensive, because of the materials that are Solar panels can also be expensive, because of the materials that are used to create them. This includes portable devices that utilize solar used to create them. This includes portable devices that utilize solar energy. energy.

Fortunately, there are some people who sell damaged solar cells, which Fortunately, there are some people who sell damaged solar cells, which are much cheaper. These damaged solar cells are be used to build solar are much cheaper. These damaged solar cells are be used to build solar panels.panels.

It is also true that direct sunlight is needed in order to make the most of It is also true that direct sunlight is needed in order to make the most of the sun’s energy– and to generate the highest amounts of power.  This the sun’s energy– and to generate the highest amounts of power.  This significantly restricts the placement of solar panelssignificantly restricts the placement of solar panels

Huge amount of water and land is required.Huge amount of water and land is required.

Applications Of SPTTApplications Of SPTTSolar Powered LED lighting system provides bright light charged by Solar Powered LED lighting system provides bright light charged by sunlight. Suitable for wherever the grid electricity is unreliable or sunlight. Suitable for wherever the grid electricity is unreliable or unavailable.unavailable.

  

In order to supply Electricity for street lights, solar power tower In order to supply Electricity for street lights, solar power tower technologies are used.technologies are used.

  

Solar Power can be used as Alternative for Wind & Hydro power.Solar Power can be used as Alternative for Wind & Hydro power.

  

These plants are best suited for utility-scale applications in the 30 to These plants are best suited for utility-scale applications in the 30 to 400 MW range.400 MW range.

Provides rough enough Electricity for night use & during Cloudy Provides rough enough Electricity for night use & during Cloudy weather.weather.

Solar tower technology produces air above 1000°C or synthesis gas Solar tower technology produces air above 1000°C or synthesis gas for gas turbine operation.for gas turbine operation.

SOLAR TWO POWER TOWER TECHNOLOGYSOLAR TWO POWER TOWER TECHNOLOGY

ConclusionsConclusions1. It is very efficiency system can be increased by hybridizing it

with the other conventional plants.

2. Very economy excluding initial cost.

3. Can be implemented with alternative like WIND and HYDRO power generation.

4. Molten salt has the best Heat capacity.

5. Non pollutant power technology.

6. It will be the power source for developing countries.

REFERENCESREFERENCES 11..Solar power engineering By B.S MagalSolar power engineering By B.S Magal

2.Solar energy fundamentals and applications By H P Garg and J Prakash2.Solar energy fundamentals and applications By H P Garg and J Prakash

3.www.wikepedia.org3.www.wikepedia.org

4.Stoddard, M.C., et. al., SOLERGY - A Computer Code for Calculating the Annual Energy 4.Stoddard, M.C., et. al., SOLERGY - A Computer Code for Calculating the Annual Energy from Central Receiver Power Plants, Sandia National Laboratories, Livermore, CA: May 1987. from Central Receiver Power Plants, Sandia National Laboratories, Livermore, CA: May 1987.

5.Meinecke, W., and M. Bohn, Solar Energy Concentrating Systems: Applications and 5.Meinecke, W., and M. Bohn, Solar Energy Concentrating Systems: Applications and Technologies, edited by M. Becker, and B. Gupta, Muller Verlag, Heidelberg, Germany, 1995.Technologies, edited by M. Becker, and B. Gupta, Muller Verlag, Heidelberg, Germany, 1995.

    6.Anderson, D. And K. Ahmed, The Case for the Solar Energy Investments, World Bank 6.Anderson, D. And K. Ahmed, The Case for the Solar Energy Investments, World Bank Technical Paper Number 279 - Energy Series, World Bank, Washington D.C.: February 1995Technical Paper Number 279 - Energy Series, World Bank, Washington D.C.: February 1995