Presentation on theme: "SOLAR CHIMNEY Solar Energy I Physics 471 2001-02-1 Instructor : Prof. Dr. AHMET ECEVIT Presented by : Yusuf SIMSEK."— Presentation transcript:
SOLAR CHIMNEY Solar Energy I Physics Instructor : Prof. Dr. AHMET ECEVIT Presented by : Yusuf SIMSEK
TABLE OF CONTENT PAGE 1.Introduction 4 2.The Collector 7 2. Structure of the Collector 8 3. Glazed Collector 9 4. The Energy Storage in the Collector Chimney Solar Chimney Prototype at Manzanares (Spain) Turbines How Does Collector Work? 17
9. Collector Efficiency The Chimney The Turbine The Appropriate Charesteristic Curve Typical Dymensions for Solar Chimneys Termodynamics Operation Technical Data Quantities Energy Production Costs Conclusion 47
1.INTRODUCTION Solar chimney converts the solar radiation into electricity. It consists of three simple parts: –– Glass roof collector –– Chimney –– Turbine Basically, air is heated by solar radiation under the glass roof and it starts to move toward to the chimney. Turbines which are placed at the base of the chimney converts this mechanical power into electricity (Fig. 1.).Basically
“A single solar chimney with a suitable large glazed roof area and a high chimney can be designed to generate 100 to 200 MW continously 24 h a day. Thus even a small number of solar chimneys can replace a large nuclear power station. Solar chimneys operate simply and have a number of other advantages: –– The collector can use all solar radiation, direct and diffused. –– Due to the heat storage system the soalr chimney will operate 24h on pure solar energy. –– Solar chimneys are particularly reliable and not liable to break down, in comparision with other solar generating plants. –– Unlike conventional power stations (and also other solar thermal power station types), solar chimneys do not need cooling water.
–– Unlike conventional power stations (and also other solar thermal power station types), solar chimneys do not cooling water. –– The building materials needed for solar chimney, mainly concrete and glass, are available everywhere in sufficient quantities. –– Even in poor countries it is possible to build a large plant without high foreign currency expenditure by using their own resources and work forces .”
2. The Collector Collector is the part of the chimney that produce hot air by the green house effect. It has a roof made up of plastic film or glass plastic film. The roof material is stretched horizontally two or six meter above the ground. The height of the roof increases adjacent to the chimney base, so that the air is diverted to the chimney base with minimum friction loss. “This covering admits the short wave solar radiation component and retains long-wave radiation from the heated ground. Thus the ground under the roof heats up and transfers its heat to the air flowing radially above it from the outside to the chimney .” Collector Chimney Turbine Fig. 1.Parts of the Solar Chimney
3. Structure of the Collector The structure of the collector changes to the covering material we used. If we use plastic film we can construct the skeleton by adjusting the space between the rods as 6 meter. In this type skeleton attaching plastic film is easy and it is particularly suitable for very large collector surface in remote places because of the small quantites of the materials needed and low transportation cost. “The m 2 of the prototype were covered with various plastic film and glass to establish the optimum and cheapest material in the long life term .”
4. Glazed Collector A flate glazed roof must have much more durable skeleton. Besause glazing increases the mass of the roof. Its rods are more stronger and they are attached like in the picture below (Fig. 2.). A collector roof of this kind has a very long life–span. “With proper maintanence this can easilly be 60 years or more .” Fig. 2. Collector Glass Roof of Solar Chimney Prototype at Manzanares from Inside
“A flate glazed collector can convert up to 70% of irratiated solar energy into heat, dependent on air throughput, a typical annual average is 50%. Also the ground under the roof provides natural energy storage at no cost .” Clearly, the temperature increases towards to the tower and energy loss increases near the chimney. We can increase the ability of the collector roof by double glazing about the tower (Fig. 3). Fig. 3. Aerial View of Solar Chimney Prototype at Dusk.
5. The Energy Storage in the Collector “Water filled black tubes are laid down side by side on the black sheeted or sprayed soil under the glass roof collector (Fig. 4). They are filled with water once and remain closed thereafter, so that no evaporation can take place. The volume of water in the tubes is selected to correspond to a water layer with a depth of 5 to 20 cm depending on the desired power output. Since the heat transfer between black tubes and water is much larger than that between the black sheet and the soil, even at low water flow speed in the tubes, and since the heat capacity of water (4.2 kJ/kg) is much higher than that of soil ( kJ/kg) the water inside the tubes stores a part of the solar heat and releases it during the night, when the air in the collector cools down .”
Fig. 4: Principle of heat storage underneath the roof using water-filled black tubes.
“The chimney is the plant’s actual thermal engine (Fig. 5). Its optimal surface- volume ratio decreases friction loss and makes it like a pressure tube. “The upthrust of the air heated in the collector is aproximately proportional to the air temperature rise ΔT in the collector and the volume of the cchimney. In a solar chimney the collector raises the temperature of the air by about ΔT= 35 o C. This produce an updraught velocity in the chimney of about V=15m/s .” 6. Chimney Fig. 5. Chimney
“The sheet metal was only 1.5mm thick 150m high 10m diameter The debt of beading was 150mm The sheets were abuted vertically at intervals of 8.6m and shiftened every 4m by exterior trussrirelers .” 7. Solar Chimney Prototype at Manzanares (Spain) (Fig. 6) Fig. 6. Solar Chimney Prototype at Manzanares
Fig. 7. Prototype of the solar chimney at Manzanares. chimney 195 m high and 10 m in diameter surrounded by a collector 240 m in diameter.
The turbines, the air current is converted into mechanical energy. The turbines are always placed at a height of 9 meter at the base of the chimney. According to the size of the turbine, they placed horizontally (Fig. 8) or verticaly (Fig. 9) and also the number of the turbines can vary. 8.Turbines Fig. 8. Horizontal Fig. 9. Vertical
When solar radiation pass through the transparent roof it is absorbed by the ground elements and it converts into heat energy. When air is heated it starts to rise up and, starts to move toward the chimney and gains a velocity (Fig. 10). 9.How Does A Collector Work? “A solar chimney collector converts available solar radiation G onto the collector surface A coll into heat output. Collector efficiency n coll can be expressed as ratio of the heatoutput of the collector as heated air Q and the solar radiation G (measured in W/m 2 ) times A coll .” Fig. 10. Solar Chimney Power Plants
Collector Efficiency Heat Output Collector Area Solar Radiation
Mass flow Spesific heat capacity of the air The temperature differences between the collector and out flow
Air speed at collector outflow/chimney inflow Chimney cross-section area Spesific dendsity of air at temperature T o + ΔT at collector outflow/chimney inflow
10. Collector Efficiency
Additionaly valid for heat balance collector: Effective absorption coefficient of the collector Loss correction value (in W/m 2 K), allowing for emission and convection loss Thus collector efficiency can also be expressed like this:
In order to find velocity
These equations are independent of roof height because friction loses and ground storage in the collector area neglected. = = 5-6 W/m 2 G=1000W/m 2 ΔT=30 0 C Typical Values: =% 62
11.The Chimney “The efficiency of the chimney (i.e. The conversion of heat into kinetic energy) is particularly independent of the rise of air temperature in the collector; it is essentially determined by the outside temperature T o at ground level (the lower the better). Thus solar chimneys can make particularly good use of the low rise in air temperature produced by heat emitted by the ground during the night and even the meager solar radiation of a cold day. Comparing with the collector and turbine, the chimney efficiency is relativelly low, hence the importance of size in its efficiency curve. For example, at a height of 1000 meters, chimney efficiency is somewhat greater than 3% .”
HCHC Outher air is cold relative to the air inside the chimney Pressure in outher enviroment is different from the inside the chimney. P(pressure) under the gravity changes with respect to h in differatial form And g : acceleration due to gravity H C : Chimney height : density Fig. 11 Chimney Height T0T0
Out of the chimney Inside of the chimney Air density in outer environment Air density in the chimney HCHC Fig. 11 Chimney Height
Thus ΔP tot increases with chimney height. ΔP tot is consist of two components The static pressure difference drops at the turbine, the dynamic component describes the kinetic energy of the air flow. (dynamic and static) so P tot = Δp tot V C,max A C Efficiency of the chimney can be established ΔP S = O ΔP tot =ΔP d ΔP tot =ΔP S +ΔP d Power volume
Actual division of the pressure difference into a static and a dynamic component depends on the energy taken up by the turbine. If the turbine is left out, a maximum flow speed of V C,max is achieved and the whole pressure difference is used to accelerate the air. Toricelli Equation: T 0 ambient temperature at ground level ΔT Temperature rises between collector inflow and collector outflow /chimney inflow
This basic simplified explanation one of the basic charesteristic of the solar chimney,which is that the chimney efficiency is fundamentaly dependent only on chimney height. Flow speed and temperature rise in the collector do not come into it. Thus the power contained in the flow
12.The Turbine “Turbine in a solar chimney do not work with staged velocity like a free-running wind energy converter, but as a closed pressure-staged wind turbogenerator, in which, similarly to a hydroelectric power station, static pressure is converted to rotational energy using a cased turbine- in this aplication installed in a pipe. The energy yield of a cased pressure-staged turbine of this kind is about eight times greater than that of a speed-stepped open-air turbine of the same diameter. Air speed before and after the turbine is about the same. The output achieved is proportional to the product of volume flow per unit time and the fall in pressure at the turbine. With a view to maximum energy yield the aim of the turbine regulation system is to maximize this product under all operating conditions .”
Blade pitch is adjusted during operation to regulate power output according to the altering air speed and air flow (Fig. 11). As soon as the wind speed in the chimney exceed 2.5 m/s the turbine is started automaticaly and cut into the public grid. The output power of the turbine is adjusted by limiting the rotation frequency of the turbine. This can be adjusted by changing the blade angle automatically (Fig. 12). Fig. 11. Turbine Propeller Fig. 12. Blade Angle
The pressure drop Theoretical useful power Power wt at turbine Power wt =V C A C ΔP S Electrical Power W = V I Volume Flow And finally we get the equation
13. The Appropriate Charesteristic Curve 2/3 ΔP tot ΔP tot ΔPsΔPs P=VΔP S. O. V Power wt takes a minimum between these extreme at: Fig. 13. Characteristic Curve
Thus mechanical power taken up by the turbine is: Power wt,max = (2/3)n coll n c A coll G Power wt,max = (2/3)n coll (g/C p T o )H o A coll G
Chimney Height H C : –––––––– 750m Collector Diameter D coll : –––––––– 2200m Solar Irradiation G: –––––––– 1000W/m 2 Mechanical Efficiency n wt : –––––––– 0.8 Collector Efficiency n coll : –––––––– 0.6 Heat Capacity of the Air C P : –––––––– 1005j/kgK Ambient Temperature T 0 : –––––––– 20 0 C Gravity Acceleration g : –––––––– 9.81m/s 2 P electric : (2/3)(0.8x0.6)[9.81/(1005x293)]x750x x1000 P electric : 30 MW
14. Typical Dymensions for Solar Chimneys With Different Power Power Block Size MW Collector Diameter D coll m Chimney Height H C m Chimney Diameter D C m Annual Energy Production GWh/y With 2300 kWh/m 2 y global radiation Dymensions Table. 1: Typical Dymensions for Solar Chimneys With Different Power
15. Thermodynamics Power Block Size MW Temperature rise in Collector oKoK Updraft Velocity in Chimney (ful load) m/s Total Pressure Difference Pa Pressure Loss by Friction (Collector And Chimney) Pa Pressure Drop at turbine Pa With 2300 kWh/m 2 y global radiation Table. 2: Thermodynamics Data
Pressure Loss at Chimney Top Pa Average Annual Efficiency Collector%56.24%54.72% Chimney%1.45%2.33% Turbines%77.00%78.30% Whole System%0.63%1.00% % 3.10% 80.10% 1.31% Table. 2: Thermodynamics Data
Power Block SizeMW Annual Energy Production TotalGWh/y Per m 2 kWh/m 2 y Annual Operating Hours h/y Full Load Hours h/y Capacity Factor%31.7%33.3%34.8% Night Energy Production GWh/y Operation Table. 3: Operation Data
Power Block SizeMW Collector Diameter m Glass Collector Roof- interior Diameter m Total Covered Aream Glass Roof Area Total m2m Double Glazed 2x4mm m2m Single Glazed 1x4mm m Technical Data Quantities Table. 4: Collector Data Quantities
Glass Roof Area m Chimney Aream2m Glass Roof Height (external) m Glass Roof Height (internal ) m Total Quantity 4mm Raw Glass km Table. 4: Collector Data Quantities
18. Energy Production Costs “With the support of construction companies, the glass industry and turbine manufacturers a rather exact cost estimate for a 200 MW solar chimney could be compiled. We asked a big utility "Energie in Baden-Württemberg" to determine the energy production costs compared to coal- and combined cycle power plants based on equal and common methods (Table. 5) .
Table. 5: Comparison between the energy production costs of a 2 x 200 MW solar chimneys and 400 MW coal and combined cycle power plants according to the present business managerial calculations.
Fig. 14. Energy production costs from solar chimneys, coal and combined cycle power plants depending on the interest rate.
CONCLUSION “No ecological harm and no consumption of resources, not even for the construction. Solar chimneys predominantly consist of concrete and glass which are made from sand and stone plus self-generated energy. Consequently in desert areas - with inexhaustible sand and stone solar chimneys can reproduce themselves. A truly sustainable source of energy! .”
REFERENCES: 1.The Solar Chimney. The use of three “old“ technologies. Retrieved 1 December 2001 from; aultview/0DED34BF3EB9A985C F09E/$F ile/SolarChimney_short_version.pdf aultview/0DED34BF3EB9A985C F09E/$F ile/SolarChimney_short_version.pdf 2.Schlaich, J. (1995). Solar Chimney: Electricity from the Sun. Stuttgart; Edition Axel Menges, p Schlaich, J. (1995). Solar Chimney: Electricity from the Sun. Stuttgart; Edition Axel Menges, p Schlaich, J. (1995). Solar Chimney: Electricity from the Sun. Stuttgart; Edition Axel Menges, p.17.
5.Schlaich, J. (1995). Solar Chimney: Electricity from the Sun. Stuttgart; Edition Axel Menges, p The Solar Chimney. The energy storage. Retrieved 1 December 2001 from; aultview/0DED34BF3EB9A985C F09E/$ File/SolarChimney_short_version.pdf aultview/0DED34BF3EB9A985C F09E/$ File/SolarChimney_short_version.pdf 7.Schlaich, J. (1995). Solar Chimney: Electricity from the Sun. Stuttgart; Edition Axel Menges, p Internet sayfasini bul 9.Schlaich, J. (1995). Solar Chimney: Electricity from the Sun. Stuttgart; Edition Axel Menges, p.52.
10. Schlaich, J. (1995). Solar Chimney: Electricity from the Sun. Stuttgart; Edition Axel Menges, p Schlaich, J. (1995). Solar Chimney: Electricity from the Sun. Stuttgart; Edition Axel Menges, p The Solar Chimney. Energy Production Costs. Retrieved 1 December 2001 from; ltview/0DED34BF3EB9A985C F09E/$File/ SolarChimney_short_version.pdf ltview/0DED34BF3EB9A985C F09E/$File/ SolarChimney_short_version.pdf 13. The Solar Chimney. Energy Production Costs. Retrieved 1 December 2001 from; ltview/0DED34BF3EB9A985C F09E/$File/ SolarChimney_short_version.pdf ltview/0DED34BF3EB9A985C F09E/$File/ SolarChimney_short_version.pdf
Fig. 2. Collector glass roof of solar chimney prototype at Manzanares from inside. Retrieved 30 November 2001 from; 328e30a3e 2c c67f/A ECAD96C A66F /$File/glass_roof_from_inside.jpg 328e30a3e 2c c67f/A ECAD96C A66F /$File/glass_roof_from_inside.jpg Fig. 3. Aerial View of Solar Chimney Prototype at Dusk. Retrieved 30 November 2001 from; Open&840A07E8A8A6A557C EEDF8 Open&840A07E8A8A6A557C EEDF8 Fig. 4. The energy storage; Principle of heat storage underneath the roof using water-filled black tubes. Retrieved 1 December 2001 from; /0DED34BF3EB9A985C F09E /$File/SolarChimney_short_version.pdf /0DED34BF3EB9A985C F09E /$File/SolarChimney_short_version.pdf
Fig. 5. Solar Chimney prototype during construction. Retrieved 30 November 2001 from; 80db7dc125680f /1982AF C F7395/ $File/SolarChimneyManzanaresChimneyConstruction.jpg 80db7dc125680f /1982AF C F7395/ $File/SolarChimneyManzanaresChimneyConstruction.jpg Fig. 6. Solar Chimney Prototype at Manzanares. Retrieved 30 November 2001 from; 80db7dc125680f / EE820787FC CF03F/ $File/manzanares_air.jpg 80db7dc125680f / EE820787FC CF03F/ $File/manzanares_air.jpg Fig. 10. Solar Chimney Power Plants. Retrieved 30 November 2001 from; Fig. 14. The Solar Chimney. Energy Production Costs. Retrieved 1 December 2001 from; /0DED34BF3EB9A985C F09E/$File/SolarChimne y_short_version.pdf /0DED34BF3EB9A985C F09E/$File/SolarChimne y_short_version.pdf
Table. 1: Schlaich, J. (1995). Solar Chimney: Electricity from the Sun. Stuttgart; Edition Axel Menges, p.36. Table. 2: Schlaich, J. (1995). Solar Chimney: Electricity from, the Sun. Stuttgart; Edition Axel Menges, p.37. Table. 3: Schlaich, J. (1995). Solar Chimney: Electricity from the Sun. Stuttgart; Edition Axel Menges, p.37. Table. 4: Schlaich, J. (1995). Solar Chimney: Electricity from the Sun. Stuttgart; Edition Axel Menges, p.38. Table. 5: The Solar Chimney. Energy Production Costs. Retrieved 1 December 2001 from; view/0DED34BF3EB9A985C F09E/$File/Sola rChimney_short_version.pdf view/0DED34BF3EB9A985C F09E/$File/Sola rChimney_short_version.pdf