48688175 solar tower technology

8/6/2019 48688175 Solar Tower Technology

http://slidepdf.com/reader/full/48688175-solar-tower-technology 1/36

PRESENTED BY : RANJAN MISHRALU ID # L20236096

APRIL 26 TH 2011



` Introduction` Definition Of Solar Tower` Parts Of Solar Tower

` Functional Principle` Typical dimension And Electricity Output` Examples` Advantages` Disadvantages` Conclusion` References



` Sensible technology for the wide use of renewable energymust be simple and reliable, accessible to the technologicallyless developed countries that are sunny and often have limitedraw materials resources.

` It should not need cooling water and it should be based onenvironmentally sound production from renewable or recyclable materials.

` The solar tower meets these conditions. Economic appraisals based on experience and knowledge gathered so far haveshown that large scale solar towers (� 100MW)are capable of generating electricity at costs comparable to those of conventional power plant.



` This is reason enough to further develop this form of solar energy utilization, up to large, economically viable units.

` In a future energy economy, solar towers could thus helpassure the economic and environmentally benign provision of electricity in sunny regions.

` The solar tower's three essential elements solar air collector,

chimney/tower, and wind turbines-have been familiar for centuries.



` A solar tower sometimes also called 'solar chimney' or solar updrafttower power plant.` It is possible to produce electricity using solar system without

concentration of sunlight. The Solar Tower is a large-scale solar thermal power plant ( 200MW).

` Solar Updraft Towers are like an inverted funnel, with a wideskirt(circular greenhouse collector) to collect air then turn a turbinein the tower.

` Since there is temperature difference between greenhouse area andtop of the tower natural convection causes air heated in the collector to rise and escape through the chimney.

` This air flow drives pressure staged turbines to generate electricity.If heat is store during the day this can also be used to produceelectricity.



.



` Hot air for the solar tower is produced by the greenhouse effect in asimple air collector consisting of a glass or plastic glazing stretchedhorizontally several meters above the ground.

`

The height of the glazing increases adjacent to the tower base, sothat the air is diverted to vertical movement with minimum frictionloss.

` This glazing admits the solar radiation component and retains long-wave re-radiation from the heated ground.

` Thus the ground under the roof heats up and transfers its heat to theair flowing radially above it from the outside to the tower.



` There is no limitation for the surface area. The larger the area, themore energy generated from the chimney.

` Covering materials may be different, such as; glass, plastic film or glazed collector. The most efficient one is glazed collector. It canconvert up to 70% of irradiated solar energy into heat . Also with

proper maintenance, its life span can easily be 60 years or more .



` Using turbines, mechanical output in the form of rotational energycan be derived from the air current in the tower.

` Turbines in a solar tower do not work with staged velocity like free-

running wind energy converters, but as shrouded pressure stagedwind turbo generators, in which, similarly to a hydroelectric power station, static pressure is converted to rotational energy using casedturbines.

` The specific power output (power per area swept by the rotor) of

shrouded pressure-staged turbines in the solar tower is roughly oneorder of magnitude higher than that of a velocity staged windturbine.



` Airspeed before and after the turbine is about the same. The outputachieved is proportional to the product of volume flow per time unitand the pressure differential over the turbine

` With a view to maximum energy yield, the aim of the turbinecontrol system is to maximize this product under all operatingconditions.

` To this end, blade pitch is adjusted during operation to regulate power output according to the altering airspeed and airflow.

` If the flat sides of the blades are perpendicular to the airflow, theturbine does not turn.



` If the blades are parallel to the air flow and allow the air to flowthrough undisturbed, there is no pressure drop at the turbine and noelectricity is generated.

` Between these two extremes there is an optimum blade setting theoutput is maximized if the pressure drop at the turbine is about 80%of the total pressure differential available.

` The optimum fraction depends on plant characteristics lie friction pressure losses.



figure 5- Arrangement of largeturbine

Figure 6- Arrangement of small turbines



` The tower itself is the plants actual thermal engine. Its a pressuretube with low friction loss (like a hydro power station pressure tubeor pen stock) because of its favorable surface volume ratio.

` The updraft velocity of the air is approximately proportional to theair temperature rise in the collector and to the tower height .

` In a multi-mega watt solar tower the collector raises the air temperature by about 30to 35 K.

` This produces an updraft velocity in the tower of (only) about15m/sat nominal electric output, as most of the available pressurePotential is used by the turbine and therefore does not accelerate theair.



` It is thus possible to enter into an operating solar tower plant for

maintenance without danger from high air velocities.` There are two types of different chimneys using for the plant. Free

standing chimneys and guyed tubes.` The life span of a free standing chimney is longer than that of the

Guyed tubes. It lasts about a hundred years, while the guyed tubes

is much shorter.



Figure 7- Free-standing tower Figu re -8 Guyed tower



Hot air

Ambient air

Functional Principle



` The solar tower¶s principle is shown in figure . Air is heated by solar radiation under a low circular transparent or translucent roof open atthe periphery; the roof and the natural ground below it form a solar

air collector.

` In the middle of the roof is a vertical tower with large air inlets at its base. The joint between the roof and the tower base is airtight. Ashot air is lighter than cold air it rises up the tower. Suction from thetower then draws in more hot air from the collector, and cold air comes in from the outer perimeter.



` Continuous 24 hours operation can be achieved by lacing tightwater-filled tubes or bags under the roof. The water heats up during

day-time and releases its heat at night. These tubes are filled onlyonce, no further water is needed.

` Thus solar radiation causes a constant updraft in the tower. Theenergy contained in the updraft is converted into mechanical energy

by pressure-staged turbines at the base of the tower, and intoelectrical energy by conventional generators.



Solar power towers consist of a large field of sun-trackingmirrors, called heliostats, which focus solar energy on a

receiver atop a centrally located tower. The enormous amountof energy, coming out of the sun rays, concentrated at one point(the tower in the middle), produces temperatures of approx.550°C to 1500°C. The gained thermal energy can be used for heating water or molten salt, which saves the energy for later use . Heated water gets to steam, which is used to move theturbine-generator. This way thermal energy is converted intoelectricity.



` Any solar chimney power plant is depend on mainly two factors. One iscollector area and other is height of tower.` As the area of Collector and height of tower is increases then much air is

heated and much air is passed through tower ,more power is generated.` So there is table which shows that power is directly proportional to height

of tower.Capacity MW Tower height

mTower Diameter m

Collector diameter m

ElectricityoutputGWH/A

5 550 45 1250 14

30 750 70 2900 99

100 1000 110 4300 320

200 1000 150 7000 680

At a site with annual global radiation of 2300kwh/(m²a)



Prototype In Spain

The new solar thermal power plant outside Seville in southern Spain.



1 . Tower height 194.6meter

2. Tower radius 5.08meter

3. Collector radius 122meter

4. Roof height 1.85meter

5 . No. of turbine 1

6. No. of turbine blade 47. Output of plant 50KW



1. Location Midura (New south wales)

2. Tower diameter 150meter

3. Tower height 1000meter 4. Thickness of tower 25cm

5. Collector diameter 7000

6. Output of plant 200MW

7.Company Enviro Mission Limied

8. No. of turbine 32 each of 6.25MW



1. Solar chimney power stations are particularly suitable for generatingelectricity in deserts and sun-rich wasteland.

2. It provides electricity 24 hour a day from solar energy alone.3. No fuel is needed. It needs no cooling water and is suitable in extreme drying

regions.4. It is particularly reliable and a little trouble-prone compared with other power

plants.5. The materials concrete, glass and steel necessary for the building of solar

chimney power stations are everywhere in sufficient quantities.6. The used technology not complex.7. No ecological harm and no consumption of resources. will reduce production

of over 900,000 tons of greenhouse gases annually



1. Huge Land requirement

With respect to ³land used Vs electricity output ³,

Land used is more than that of nuclear or coal power plants.



5 00 MW coalpower plant 1-

1 .2 5 billiondollars.

27 00 MW Nuclear Power plant cost 6

billion dollars

` 2) H igh initial investment:

Heliostats account for 30 % of the cost.Estimated cost of 300 MW solar plant isaround 2 billion dollars.



` The updraft solar tower works on a simple proven principle, its physicsare well understood. As efficiency of the plant increases with tower height, such plants have to be large to become cost competitive.

`

Large plants mean high investment costs, which are mostly due tolabour costs and in addition no costly consumption of fossil fuels. Thelatter reduces dependence on imported oil and coal, which is especially

beneficial for the developing countries releasing means for their development.

` There is no ecological harm and no consumption of resources, not evenfor the construction, as solar towers predominantly consist of concreteand glass which are made from sand and stone plus self-generatedenergy.

` Consequently in desert areas with inexhaustible sand and stone solar towers can reproduce themselves. A truly sustainable source of energy!



1. µOur Energy Future Resources alternative and environment´ by Christian Ngo, Joseph Natowitz .

2. http://www.wikipedia.org/wiki/solar_udraft_tower

3. http://www.solarmissiontechnologies.com/project.htm

48688175 solar tower technology

Documents