FABRICATION OF SOLAR REFLECTOR FOR POWER PRODUCTION USING STIRLING ENGINE

S.SHIVA TEJA 11119D117

K.P. THEJESWARA KUMAR 11119D126

T.VAMSHI KRISHNA 11119D127

V.CHANDRA SEKHAR 11119D133

Y.PHANINDRA 11119D143

Under the guidance of…MR.R.ELLAPPAN(ASST PROF)..MECH

PRINCIPLE OF CONVERGENCE

When light rays pass through convex lens they get converged and when they fall on a concave mirror they get reflected and converge at a point

This point is called as focal point or point of convergence

REFLECTOR ARRANGEMENT

STIRLING ENGINE

It’s a heat engine operated by cyclic compression and expansion of air or other gas as working fluid at different temperatures

High efficiency compared to normal heat engines

Three types of Stirling engines are used they are Alpha, Beta, Gamma

Alpha type Stirling engine contains two power pistons in separate cylinders one at hot and other at cold and the temperature difference is around 90deg c

Beta type Stirling engine works with a single piston in a cylinder hot at one end and cold at other end. piston drives the flywheel at it’s end

A gamma Stirling is simply a beta Stirling in which the power piston is mounted in a separate cylinder alongside the displacer piston cylinder, but is still connected to the same flywheel.

RADIATION OF HEAT RECEIVED BY EARTH

TIME VS SOLAR RADIATION

OVERVIEW

Several mirrors are arranged on a concave surface

When sunrays fall on a concave reflecting surface they get converged at a point

This point of convergence produces enormous amount of heat

This heat energy is used to run a stirling engine

Stirling engine consumes heat and produces mechanical energy

Mechanical energy is converted into electrical energy by an alternator

FLOW CHART

SUN RAYS

REFLECTOR

CONVERGENCE POINT

STIRLING ENGINE

ALTERNATOR

ELECTRICAL ENERGY

LAYOUT

SPECIFCATIONS

Power : 2-4watts Voltage : 3-5v Speed : 1300-1500rpm Material : Steel ,Copper ,Aluminium Base : Stainless steel Arc length major axis: 74 minor axis:60 Chord length major axis: 70 minor axis:57 Temperature at convergence:170-200deg c

PRINCIPLE FOCUS OF REFLECTOR

Let “n” , be the ratio of chord length to length of the arc.

For ellipse, The arc length of the minor axis = 60, The chord length of minor axis =57, Then, n=57/60 =0.95 Let us assume that X=1 radian,

(1) X1 = X-[f(X)/f’(X)] = 1 –[sin1-(n*1) / cos1-n] = 1-[0.108529/0.409697] = 0.735099(2) X2 = X1 –[sinX1-(n*X1) / cosX1 – n] = 0.735099 – [0.027683/ 0.208235] = 0.602157(3) X3 = X2 - [sinX2 – (n*X2)/cosX2 – n] =0.602157-[0.005627 / 0.125884] = 0.557457(4) X4 = X3 -[sinX3-(n*X3) / cosX3-n] = 0.557457-[0.000554/ 0.101396] =0.551993(5) X5 =0.551910(6) X6= 0.551910 radians =31.622degrees =31.622*2 = 63. 24degrees

Radius= 28.5/sin31.622

R =54.356cm Now, to find the focal point f1=R/2 =54.356/2 f1 = 27.178cm

Similarly, we have to find for major axis Length of the chord = 70 Arc length =74n =70/74 =0.9459

We get 31 degrees,= 31*2=62 degrees

Radius = 35/sin31 = 67.956cmFocal point f2=R/2 =67.956/2 f2 = 33.978cm Therefore ,the focal point lies between f1 & f2 i.e., between 27.178cm & 33.978cm

EFFICIENCY OF STIRLING ENGINE

The efficiency of the Stirling engine can be determined by using CARNOT CYCLE. The method is derived from heat side and cold side temperatures TH and Tc. Details are shown on PV diagram of carnot cycle.

TH is the explosion temperature.TC is the exhaustion temperature.η = (TH - TC) / TH TH = 130 oCTC = 85 oCTherefore , the efficiency can be given by:η = ( 130 – 85) / 130 = 45/130 η = 0.346Therefore, the efficiency of the Stirling is 34.6%

CONCLUSION:

The temperature required to run a beta type Stirling engine is 150deg c and an alpha type Stirling engine can run at higher temperatures than this and works with higher efficiency

For better efficiency of a Beta type Stirling engine make a shaft instead of flywheel and keep it in a magnetic field so that it acts as a generator

REFERENCES:

AT Kearney and ESTELA, 2010, Solar Thermal Electricity 2025 – A.T. Kearney, www.atkearney.com.

IEA, 2010a, Concentrating Solar Power Technology Roadmap – International Energy Agency, Paris 2010, www.iea.org.

IEA, 2010b, Energy Technology Perspectives 2010, International Energy Agency, Paris2010, www.iea.org.

Mark powell et al.(2009), The Suncatcher: a highly efficient, solar-powered Stirling engine.

Guimaraes et al,(2014) , Stirling engine for cogeneration

Roelf J. Meijer et al. (1987), solar powered Stirling engine, Stirling thermal motors, Inc