1. Group members Roll NO.Sajjad Ahmed ( Group leader) 26Ghulam
Sarwar 14Nasir Ali 07Abdul Baqi 09Shoaib Ahmed 23Shafique Rehman
01Project advisor: Engr. Bashir Ahmed Leghari
2. Overview The engine used for the demonstration of Stirling
cycle inthe thesis presented in Department of MechanicalEngineering
BUET Khuzdar during 2011 was operated byCNG/LPG gas. we wanted to
operate that with direct solarradiation using concentrating convex
lens.
3. Introduction Convex lens is used to converge the solar
radiation to a singlepoint so that high amount of heat energy is
obtained. This heat energy is used to heat the displacer cylinder
of thestirling engine. When the air inside the cylinder is heated
its pressure increasesthat pushes the displacer. The displacer is
connected to theflywheel by the help of a connecting rod. The
reciprocating motion of the displacer is converted intorotational
energy of the flywheel by the help of crank. This mechanical energy
can further be used to produce electricpower.
4. Objective Of the StudyThe objective of this project is
closely linked to the energyproblem with a specific focus on
electricity generation usingsolar power To reduce the Grid
dependence by building a residentialbased cost effective and
renewable power supply. To provide for relief work in disaster
affected areas likeearthquake, flood etc. To avoid burning of
fossil fuel for power generation andprovide a environment friendly
power technology.
5. Solar Energy Solar energy is the heat energy obtained from
the Sun In sheer size, solar energy has the potential to supply
allenergy needs: electric, thermal, transportation etc It is
regarded as the solution for reducing the use of fossiland nuclear
fuels and for a cleaner environment. Solar energy is very diffuse
and is scattered, it therefore,needs systems and components to
capture and concentrateit efficiently for conversions to any of the
uses.
6. Solar-Electric Conversion SystemsThere are many
differenttypes of solar energysystems that will convert thesolar
resource into a usefulform of energy. CSP systems use lenses
ormirrors and tracking systemsto focus a large area ofsunlight into
a small beam. PV converts light intoelectric current using
thephotoelectric effect.
7. Concentrated Solar PowerConcentrated solar power (CSP)
technologies use lens ormirrors to reflect and concentrate sunlight
onto receivers.The receivers collect the concentrated solar energy
andconvert it to high-temperature heat that can drive either heat
engine domestic heating create steam to drive a turbine
desalination
8. Different CSP techniquesSolar Parabolic TroughFresnel
lensConcentrated Photovoltaic
9. Cont Solar Power Tower Solar Dish-EngineSystems
10. Stirling Engine A Stirling engine is a heat engine
operating by cycliccompression and expansion of air or other gas.
Theworking fluid, at different temperature levels such thatthere is
a net conversion of heat energy to mechanicalwork. The external
combustion aspect enables a Stirling Engineto operate equally well
on multiple types of fuel, such asnatural gas, gasoline, diesel, or
even heat from the sun
11. Cont The Stirling engine is notedfor its high efficiency
(up to40%). It operates Quietly and theease with which it can
usealmost any heat source. In this case the sun's heat isused for
operating the engine. Stirling engine is a closed-cycleregenerative
heatengine permanently workingon gaseous fluid.
12. Stirling engine configurations Alpha enginesIt has two
pistons inseparate cylinders which areconnected in series by
aheater, regenerator andcooler. Seals are provided on boththe hot
and cold pistons toprevent the escape of gasfrom the engine
cylinders.
13. Cont Beta Engines The Beta engine has both thedisplacer and
the piston arein the single cylinder.A beta Stirling has a
singlepower piston arranged withinthe same cylinder on thesame
shaft as a displacerpiston.
14. Cont Gamma Engines A gamma Stirling engineis simply like a
beta typebut the power piston ismounted in a separate
cylinderadjacent tothe displacer piston cylinder. both pistons are
connected tothe same flywheel. The gas in the two cylinderscan flow
freely between them.
15. Operation /working cycle 1-2 const. Volume heating 2-3
isothermal expansionof the gas 3-4 const. Volume coolingof the gas.
4-1-Iso thermalcompression of the gas.
16. Major Components of the StirlingEngine Displacer- To shift
the volume of gas from one end ofcylinder to an other. Power Piston
- The work of the power piston is tocompress 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 theexpansion of displacer and provide the same energyduring
compression to the power piston. Sealing- To reduce leakage of gas
and maintaining thepressure.
17. Cont Regenerator- It captures the heat from the gas
afterexpansion and provide this heat to the gas when it movesfrom
cold end to the hot end of the engine. Connecting rods- It
transmits the mechanical work of thedisplacer to the flywheel.
Cooling fins- Fins are made over the cold end displacercylinder for
dissipation of heat to the sink. Pressure Regulating Screw- It is
used to regulate thepressure.
18. 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
allowsmore optical aberrations to be corrected than is possiblewith
a single element.
19. Types of simple lenses Lenses are classified by the
curvature of the two opticalsurfaces.
20. Convex Lenses Typically made of glass or transparent
plastic, a convexlens has at least one surface that curves outward
like theexterior of a sphere. it is the most commonly used. A
convex lens is also known as a converging lens. Aconverging lens is
a lens that converge rays of light thatare traveling parallel to
its principal axis
21. Concentration of light throughconvex lens
22. Site Characteristic This residential based power generation
system ismade for the District Khuzdar. The overall directnormal
solar radiation in Pakistan is shown:
23. Geographic location of Khuzdar Geographic coordinates of
Khuzdar, PakistanLatitude: 27.74N , Longitude: 66.64EElevation
above sea level: 1218 m = 3996 ft
25. Solar Parameters The solar parameters are taken for 3rd
july inselected site where the maximum temp is 41.5 C LabelsHGloCS-
Horizontal clear sky Global RadiationHDifCS- Horizontal clear sky
Diffuse RadiationHBmCS- Horizontal clear sky Beam RadiationThe sum
of the diffuse and beam irradiance isequal to the global
irradiance.
28. Design Specifications Our objective is to operate the
stirling engine andproduce electric power using solar energy by
thehelp of convex lens to avoid the use of fossil fuelsand develop
a renewable energy technology. Since the amount of heat energy
produced by aconvex lens is comparatively less than that of
fossilfuels so we had to make the design changed. Theparameters
that we worked on are as follows:
29. Data for the Already ExistingStirling EngineDimensions 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
30. 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, = 28.6 %
Minimum Speed (at the start) = 80 r.p.m Maximum Speed (at the peak
revolutions)= 422 r.p.m
31. Design Specifications Hot side temperature T1 Cold End
temperature T2 Swept Volume Vs Clearance volume Vc Compression
ratio r Heat rejected to the sinkQ4-1 Heat supplied to the hot
end,Q2-3 Reduce Losses ( Leakage,conduction and convection)
32. ContHot side temperature ( T1) Since T1 depends on heat
energy supplied from thesource. It depends on the solar
concentrator (lens).Like: Area of the lens No of lens Concentration
ratio
33. ContCold end temperature (T2) The cold end temperature is
reduced by increasing the finsurface area and number of fins to
increase the heatdissipation.Swept Volume (Vs)Vs =(/4) D2lD = inner
diameter of the displacer cylinderl = length of strokeIncreased
swept volume by increasing the Diameter of displacer and lengthof
stoke.
34. ContClearance volume (Vc)Vc =(/4) D2 l1l1= clearance
lengthBy reducing the clearance length l1 we reduced theclearance
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 heatenergy
supplied is increased.
35. Reduce Losses Leakage losses- Air leakage is a big problem
at theheating section. To prevent leakage we used O-Ringsbetween
support collar and expansion cylinder. Conduction lossesTo reduce
conduction losses the heat cap and thedisplacer cylinder is made as
thin as possible. Convection lossesConvection from hot side to the
surrounding is verydifficult to stop but by placing the engine in a
certainarea where the natural air circulation is comparativelylow
the convection loss of heat is prevented.
36. Modified design specificationInner diameter of the
displacer cylinder, Di = 48.5mmLength of stroke, l = 38 mmClearance
length , l1 = 10 mmHot end Temperature, T1 = 200CCold end
temperature, T2 = 50CSwept volume, Vs = 70.2x10-6 m3Clearance
volume, Vc = 18.5x10-6 m3Total volume, Vt = 88.7x10-6Compression
ratio, r = Vs/Vc = 3.80Heat supplied to hot end Q2-3 =180.8
KJ/KgThen heat rejected to the sink, Q4-1= -123.7 KJ/KgNet Work
done Wn = 57.1 KJ/KgThermal Efficiency of the engine =31.7%
37. Solar concentratorFor concentrating the solar energy onto
the receiving section of thestirling engine to heat it up we used
convex lens. Parameters for theconvex lens are given below:Type of
lens used is biconvexDiameter of the lens, d= 130 mmFocal length, L
= 20cmArea of lens, A= (/4) d2= 0.0153m2Diameter of the beam at the
focal point, di = 10 mmConcentration ratio, C = d/di= 130/10 =
13
38. ContIn our site selected ( Khuzdar) the average horizontal
clear sky Global irradiancefrom 7.am to 6.pm is calculated to
be=720 W/m2The amount of solar radiation intensity that can strike
our lens is:= 720x area of the lens=720x0.0153= 11.01 W/ lensSince
the concentration ratio is,C= 13then the amount of solar energy
produced by the lens at the focal point is=11.01x13= 143.2
W/lens
39. Test ResultsTime HGloCS W/m2Temperature at hotend
(C0)Angular Speed(RPM)Thermaleffiiency7:00 am 192 17 0 08:00 am 432
20 0 09:00 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%
40. Test Results
41. Test Results
42. ConclusionOld Design Modified Design Source of energy
inputFossil fuel Net work doneWn = 50.81 KJ/Kg Thermal efficiency =
28.6 % Source of energy inputDirect solar thermal energy (convex
lens) Net work doneWn = 57.1 KJ/Kg Thermal efficiency = 0.317 =
31.7%
43. Future RecommendationThe following recommendations are
given for futurework:- That the Fresnel lens which is made of
plastic can be moresuccessful. That it is also recommended that
helium gas is usedinstead of air due to its better thermodynamic
properties. The overall efficiency can be improved, if increase the
sizeof the lens used in the system. The efficiency of the system
can be improved by usingautomatic tracking.
