Final presentation( sajjad)
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The document describes a project to operate a Stirling engine using solar energy concentrated by a convex lens. A group of 7 students and their advisor are modifying an existing Stirling engine demonstration to be powered by sunlight rather than gas. Their objectives are to generate electricity using solar power to reduce grid dependence and provide environmentally friendly power. The design changes focus on increasing heat input through the solar concentrator and improving heat transfer to increase efficiency.
Final presentation( sajjad)
- 2. Group members Roll NO. Sajjad Ahmed ( Group leader) 26 Ghulam Sarwar 14 Nasir Ali 07 Abdul Baqi 09 Shoaib Ahmed 23 Shafique Rehman 01 Project advisor: Engr. Bashir Ahmed Leghari
- 3. Overview The engine used for the demonstration of Stirling cycle in the thesis presented in Department of Mechanical Engineering BUET Khuzdar during 2011 was operated by CNG/LPG gas. we wanted to operate that with direct solar radiation using concentrating convex lens.
- 4. Introduction Convex lens is used to converge the solar radiation to a single point so that high amount of heat energy is obtained. This heat energy is used to heat the displacer cylinder of the stirling engine. When the air inside the cylinder is heated its pressure increases that pushes the displacer. The displacer is connected to the flywheel by the help of a connecting rod. The reciprocating motion of the displacer is converted into rotational energy of the flywheel by the help of crank. This mechanical energy can further be used to produce electric power.
- 5. Objective Of the Study The objective of this project is closely linked to the energy problem with a specific focus on electricity generation using solar power To reduce the Grid dependence by building a residential based cost effective and renewable power supply. To provide for relief work in disaster affected areas like earthquake, flood etc. To avoid burning of fossil fuel for power generation and provide a environment friendly power technology.
- 6. Solar Energy Solar energy is the heat energy obtained from the Sun In sheer size, solar energy has the potential to supply all energy needs: electric, thermal, transportation etc It is regarded as the solution for reducing the use of fossil and nuclear fuels and for a cleaner environment. Solar energy is very diffuse and is scattered, it therefore, needs systems and components to capture and concentrate it efficiently for conversions to any of the uses.
- 7. Solar-Electric Conversion Systems There are many different types of solar energy systems that will convert the solar resource into a useful form of energy. CSP systems use lenses or mirrors and tracking systems to focus a large area of sunlight into a small beam. PV converts light into electric current using the photoelectric effect.
- 8. Concentrated Solar Power Concentrated solar power (CSP) technologies use lens or mirrors to reflect and concentrate sunlight onto receivers. The receivers collect the concentrated solar energy and convert it to high-temperature heat that can drive either heat engine domestic heating create steam to drive a turbine desalination
- 9. Different CSP techniques Solar Parabolic Trough Fresnel lens Concentrated Photovoltaic
- 10. Cont… Solar Power Tower Solar Dish-Engine Systems
- 11. Stirling Engine A Stirling engine is a heat engine operating by cyclic compression and expansion of air or other gas. The working fluid, at different temperature levels such that there is a net conversion of heat energy to mechanical work. The external combustion aspect enables a Stirling Engine to operate equally well on multiple types of fuel, such as natural gas, gasoline, diesel, or even heat from the sun
- 12. Cont… The Stirling engine is noted for its high efficiency (up to 40%). It operates Quietly and the ease with which it can use almost any heat source. In this case the sun's heat is used for operating the engine. Stirling engine is a closed-cycle regenerative heat engine permanently working on gaseous fluid.
- 13. Stirling engine configurations Alpha engines It has two pistons in separate cylinders which are connected in series by a heater, regenerator and cooler. Seals are provided on both the hot and cold pistons to prevent the escape of gas from the engine cylinders.
- 14. Cont… Beta Engines The Beta engine has both the displacer and the piston are in the single cylinder. A beta Stirling has a single power piston arranged within the same cylinder on the same shaft as a displacer piston.
- 15. Cont… • Gamma Engines A gamma Stirling engine is simply like a beta type but the power piston is mounted in a separate cylinder adjacent to the displacer piston cylinder. both pistons are connected to the same flywheel. The gas in the two cylinders can flow freely between them.
- 16. Operation /working cycle 1-2 const. Volume heating 2-3 isothermal expansion of the gas 3-4 const. Volume cooling of the gas. 4-1-Iso thermal compression of the gas.
- 17. Major Components of the Stirling Engine Displacer- To shift the volume of gas from one end of cylinder to an other. Power Piston - The work of the power piston is to compress the gas at low temperature to expansion space. Bush - Used to align the displacer rod and connecting rod. Flywheel - It is used to store energy during the expansion of displacer and provide the same energy during compression to the power piston. Sealing- To reduce leakage of gas and maintaining the pressure.
- 18. Cont… Regenerator- It captures the heat from the gas after expansion and provide this heat to the gas when it moves from cold end to the hot end of the engine. Connecting rods- It transmits the mechanical work of the displacer to the flywheel. Cooling fins- Fins are made over the cold end displacer cylinder for dissipation of heat to the sink. Pressure Regulating Screw- It is used to regulate the pressure.
- 19. The Solar Concentrator It is used to refract light, converging the beam. A simple lens consists of a single optical element. A compound lens is an array of simple lenses (elements) with a common axis. The use of multiple elements allows more optical aberrations to be corrected than is possible with a single element.
- 20. Types of simple lenses Lenses are classified by the curvature of the two optical surfaces.
- 21. Convex Lenses Typically made of glass or transparent plastic, a convex lens has at least one surface that curves outward like the exterior of a sphere. it is the most commonly used. A convex lens is also known as a converging lens. A converging lens is a lens that converge rays of light that are traveling parallel to its principal axis
- 22. Concentration of light through convex lens
- 23. Site Characteristic This residential based power generation system is made for the District Khuzdar. The overall direct normal solar radiation in Pakistan is shown:
- 24. Geographic location of Khuzdar Geographic coordinates of Khuzdar, Pakistan Latitude: 27.74N , Longitude: 66.64E Elevation above sea level: 1218 m = 3996 ft
- 25. Average monthly climate conditions for The year 2012 in Khuzdar Months T TM Tm PP V VM Jan 10.1 17.1 2.4 14.74 2.1 6.7 Feb 11.7 19.6 3.8 0 3.8 9.4 March 19.6 26.1 10.8 13.97 4.5 12.4 April 24.1 29.7 17 27.17 5.2 13.7 May 29.8 36.4 22.6 23.88 5.7 15.1 June 31.5 37.5 24.3 2.03 7.1 17.4 July 32 38.9 24.7 5.33 5.4 15 Aug 32 37.5 25.6 1.02 1.5 12.7 Sep 26.7 32.4 20.7 54.09 3.5 12.8 Oct 22.9 30.5 13.9 0.76 4.9 14.4 Nov 18.1 25.8 9.3 0 4.4 13.4 Dec 12.5 19.4 4.5 25.91 2.7 10.2
- 26. Solar Parameters The solar parameters are taken for 3rd july in selected site where the maximum temp is 41.5 C Labels HGloCS- Horizontal clear sky Global Radiation HDifCS- Horizontal clear sky Diffuse Radiation HBmCS- Horizontal clear sky Beam Radiation The sum of the diffuse and beam irradiance is equal to the global irradiance.
- 27. Legal Time HGloCS W/m2 HDifCS W/m2 HBmCS W/m2 06am 14 11 3 07am 192 43 149 08am 432 69 364 09am 660 90 570 10am 852 107 745 11am 990 119 872 12noon 1067 125 942
- 28. Legal Time HGloCS W/m2 HDifCS W/m2 HBmCS W/m2 01pm 1076 126 950 02 pm 1016 121 895 03 pm 892 110 782 04 pm 713 95 618 05 pm 492 75 418 06 pm 252 50 201 07 pm 42 20 22
- 29. Design Specifications Our objective is to operate the stirling engine and produce electric power using solar energy by the help of convex lens to avoid the use of fossil fuels and develop a renewable energy technology. Since the amount of heat energy produced by a convex lens is comparatively less than that of fossil fuels so we had to make the design changed. The parameters that we worked on are as follows:
- 30. Data for the Already Existing Stirling Engine Dimensions and temperature data Inner diameter of displacer cylinder, Di = 32mm Length of stroke, l = 36mm Temperature of source, T1= 250C0 Temperature of sink, T2 =100C0 Swept Volume, Vs=28.95X10-6 m3 Clearance Volume, Vc = 8.84X10-6 m3 Compression ratio, r = Vs/Vc = 3.27 Total Volume, Vt = Vc + Vs = 37.74X10-6 m3
- 31. Cont… Heat Rejected to Sink, Q4-1=-126.99KJ/Kg (Compression) Heat supplied from hot source, Q2-3 = 177.80 KJ/Kg Net work done, Wn= Heat supplied – heat rejected =50.81 KJ/Kg Efficiency, η = 28.6 % Minimum Speed (at the start) = 80 r.p.m Maximum Speed (at the peak revolutions) = 422 r.p.m
- 32. Design Specifications Hot side temperature T1 Cold End temperature T2 Swept Volume Vs Clearance volume Vc Compression ratio r Heat rejected to the sink Q4-1 Heat supplied to the hot end, Q2-3 Reduce Losses ( Leakage, conduction and convection)
- 33. Cont… Hot side temperature ( T1) Since T1 depends on heat energy supplied from the source. It depends on the solar concentrator (lens). Like: Area of the lens No of lens Concentration ratio
- 34. Cont… Cold end temperature (T2) The cold end temperature is reduced by increasing the fin surface area and number of fins to increase the heat dissipation. Swept Volume (Vs) Vs =(π/4) D2l D = inner diameter of the displacer cylinder l = length of stroke Increased swept volume by increasing the Diameter of displacer and length of stoke.
- 35. Cont… Clearance volume (Vc) Vc =(π/4) D2 l1 l1= clearance length By reducing the clearance length l1 we reduced the clearance volume. Heat supplied to the hot side (Q2-3) Q2-3 = R T1 ln ( Vs/Vc) By increasing T1, Vs and decreasing Vc the amount of heat energy supplied is increased.
- 36. Reduce Losses Leakage losses- Air leakage is a big problem at the heating section. To prevent leakage we used O-Rings between support collar and expansion cylinder. Conduction losses To reduce conduction losses the heat cap and the displacer cylinder is made as thin as possible. Convection losses Convection from hot side to the surrounding is very difficult to stop but by placing the engine in a certain area where the natural air circulation is comparatively low the convection loss of heat is prevented.
- 37. Modified design specification Inner diameter of the displacer cylinder, Di = 48.5mm Length of stroke, l = 38 mm Clearance length , l1 = 10 mm Hot end Temperature, T1 = 200C Cold end temperature, T2 = 50C Swept volume, Vs = 70.2x10-6 m3 Clearance volume, Vc = 18.5x10-6 m3 Total volume, Vt = 88.7x10-6 Compression ratio, r = Vs/Vc = 3.80 Heat supplied to hot end Q2-3 =180.8 KJ/Kg Then heat rejected to the sink, Q4-1= -123.7 KJ/Kg Net Work done Wn = 57.1 KJ/Kg Thermal Efficiency of the engine η =31.7%
- 38. Solar concentrator For concentrating the solar energy onto the receiving section of the stirling engine to heat it up we used convex lens. Parameters for the convex lens are given below: Type of lens used is biconvex Diameter of the lens, d= 130 mm Focal length, L = 20cm Area of lens, A= (π/4) d2 = 0.0153m2 Diameter of the beam at the focal point, di = 10 mm Concentration ratio, C = d/di = 130/10 = 13
- 39. Cont… In our site selected ( Khuzdar) the average horizontal clear sky Global irradiance from 7.am to 6.pm is calculated to be =720 W/m2 The amount of solar radiation intensity that can strike our lens is: = 720x area of the lens =720x0.0153 = 11.01 W/ lens Since the concentration ratio is, C= 13 then the amount of solar energy produced by the lens at the focal point is =11.01x13 = 143.2 W/lens
- 40. Test Results Time HGloCS W/m2 Temperature at hot end (C0) Angular Speed (RPM) Thermal effiiency 7:00 am 192 17 0 0 8:00 am 432 20 0 0 9:00 am 660 72 150 6.3% 10:00 am 852 180 180 28.6% 11:00 am 990 191 262 30.0% 12:00 pm 1067 195 280 30.9% 1:00 pm 1076 199 303 31.5% 2:00 pm 1016 197 250 31% 3:00 pm 892 194 230 30.7% 4:00 pm 713 140 175 21.7% 5:00 pm 492 124 65 18.6% 6:00 pm 252 65 0 4.43%
- 41. Test Results
- 42. Test Results
- 43. Conclusion Old Design Modified Design Source of energy input Fossil fuel Net work done Wn = 50.81 KJ/Kg Thermal efficiency η = 28.6 % Source of energy input Direct solar thermal energy ( convex lens) Net work done Wn = 57.1 KJ/Kg Thermal efficiency η = 0.317 = 31.7%
- 44. Future Recommendation The following recommendations are given for future work:- That the Fresnel lens which is made of plastic can be more successful. That it is also recommended that helium gas is used instead of air due to its better thermodynamic properties. The overall efficiency can be improved, if increase the size of the lens used in the system. The efficiency of the system can be improved by using automatic tracking.