Experimental Analysis of Parabolic Reflectors in Solar Energy Collection

Abstract

In today’s ever growing field of renewable energy, it is to no surprise that solar energy plays a pivotal role in harnessing free energy for tremendous growing needs. Experimental setup is being designed to test and compare the efficiency of different parabolic solar reflector made of Stainless steel and Mirror. Our goal is to achieve maximum temperature output of highest possible for circulated water flow. It will involve all default calculation necessary for parabolic reflectors. The setup opens door to several parameters combination which shall be attempted.

Introduction

A parabolic trough solar collector uses a mirror or mirror finished sheet in the shape of a parabolic cylinder to reflect and concentrate sun radiations to a receiver tube located at the focus line. The receiver absorbs the incoming radiations and transform into thermal energy which is carried fluid medium circulating within the tube. The Temperature of delivery tube can be increased by decreasing the area from which heat losses occur.

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The collectors are used based on the temperature requirement such as heating, thermal energy generation, refrigeration, and desalination, etc. In last decades various designs implemented and tested for concentrating solar collectors. The design of the Concentrators is of reflector or refractor, sometime is cylindrical or flat, and can be continuous or separate. The Collector can be flat, concave or convex and can be covered or uncovered.

Solar reflectors can be classified as follows:

• Parabolic Trough
• Dish Concentrators
• Solar Towers and
• Flat plate collectors

Design and Experimental Setup

The frame for the parabola was made out of plywood.

It would be attached to a base which would allow for proper angling or Tracking of the parabolic trough as per sun Direction. The receiver used is 6mm diameter of copper pipe, because of its high thermal conductivity and it is relatively inexpensive. The water source was planned as a reservoir located above the trough, with gravity assisted flow through the trough. For testing, a simple flow regulator was used between the tank and copper pipe to regulate the flow as per requirement. This is easier and more efficient, as well as significantly less expensive. Based on the initial design sketches materials were bought, 4*8 foot sheet, 23/32 inch outdoor plywood, 3meters long piece of copper pipe, an Iron strip of 150 cm, measuring tape and different types of screws (M6 wood screws, nails and screws) were purchased.

The next step consists of drawing of parabolic shape with required thickness on the plywood, followed by a slot for sheet to be inserted. Next the strip is measured and marked at the proper lengths provided for copper pipe and to attach with parabolic frame, can be found in fig 5. Consulting with two different shop techs at the hanger, it was concluded that the best method would be to cut one piece and use that as a template for the next piece, so a reciprocating cutting machine was used. Then the strips were cut at the proper lengths using the hack saw. Finally, the two pieces of the parabolic frame of plywood were attached and sanded to achieve the best possible parabolic curve. A holes was drilled in each plywood pieces to attach L-plate, with help of this setup was attachment to the base.

To attach the stainless steel sheet to the frame, the slot it was cut into shape by which the sheet is inserted into the frame. Holes were drilled in strip so that the copper pipe can be inserted and kept at focus point which is attached to plywood frame. Next the SS sheet was bent down into the parabola with help of bending machine and attached to frame. Finally, a T-joint was fitted to the copper pipe at the outlet for placement of thermometer. The setup was brought to the test site, and using the bolts, nuts, and washers the trough was attached to base.

Design Process:

1. Constructing the parabolic frame from plywood.
2. Attaching the frame to a base for sun tracking.
3. Using a copper pipe as the receiver due to its high thermal conductivity.
4. Incorporating a simple flow regulator for water circulation.

Calculations

Solar Radiation Calculation:

• Average distance of the sun from the earth: 1.5×10^8 km.
• Calculation of direct radiation involves considering the zenith angle, which is determined by the latitude, declination angle, and time of day.

Zenith Angle Calculation:

cosZ=sinγsinδ+cosγcosδcost

Where:

• Z = Zenith angle
• γ = Latitude of location
• δ = Declination angle
• t = Hour angle

Direct Radiation Intensity:

Id=S0cosZ=1353 W/m2cosZ

Water Flow Calculation:

Q=TimeVolume

Average distance of the sun from the earth ( ) = 1.5×km.

Consider a sphere radius ( = 1.5xkm with the sun at its centre.

= cross sectional area of the earth

AE=π=3.142{(6.4×) × (6.4× )}

= 1.287 x

Let = surface area of this imaginary sphere

=4π = 4x3.142 {(1.5×) (1.5×)} = 2.828×m2

Percentage sun’s output = [() x100]

= {x100}

= 0.0000000455%

This means that the earth receives only 0.0000000455% of sun's energy output. The world's approximate average annual energy consumption is 9.262xkWh. Hence, India would receive radiation at that rate:

Let = extraterrestrial radiation;

A = continental land area;

= extraterrestrial solar constant;

Therefore

=1353×

= 87945

Therefore, for a yearly average sunshine hour of 9hours/day = 87945x × (366x9)

= 28969083

Assuming a clearness index of 50% since 47% of extra-terrestrial radiation reaches the earth surface.

The part of solar radiation that reaches the surface of the earth without being scattered, absorbed or reflected is direct radiation and it is the most intense. The intensity of the direct radiation reaching the surface of the earth is a function of time of the day, latitude of location and declination angle. To calculate the direct radiation reaching to earth surface by considering time of the day (t), for a location (γ) with the sun at declination (δ).

Experimental Results

Experimental results are tabulated to show the average temperature variations throughout the day across three weeks of observation. The findings demonstrate the efficiency of parabolic reflectors in heating circulated water, with variations observed between the two materials used.

Conclusion

In experiment with parabolic reflectors of the order of 610 x710 dimensions. Attempts were made to analyse the performance of the parabolic reflectors. The parameters chosen were that of the material used for making the reflective surface of the parabola. Having used glass strips and SS sheet with high buffing finish we were able to get average temperature data for the major part of the day for about 21 days. However it could observed that for glass strip parabola there seems to be a constant temperature despite the varying magnitudes of suns radiation but less temperature. This phenomenon was observed due to the pack of the parabolic profile while using straight strips.

References

1. Abbas, S.M., Ranga, Y., Verma, A.K., & Esselle, K.P. (2014). A Simple Ultra Wideband Printed Monopole Antenna with High Band Rejection and Wide Radiation Patterns. IEEE Transactions On Antennas And Propagation.
2. Ullah, H., Tahir, F.A., & Khan, M.U. (2017). A Honeycomb-Shaped Planar Monopole Antenna for Broadband Millimeter-wave Applications.
3. Saito, K., Pellegrino, S., & Nojima, T. (2014). Manufacture of Arbitrary Cross-Section Composite Honeycomb Cores Based on Origami Techniques. Journal of Mechanical Design.
4. Lee, K.F. (2015). A Personal Overview of The Development of Patch Antennas.
5. Roopan, S.S.S., Bhatoa, R., Sharma, S., & Sidhu, E. (2016). Novel High Gain Honeycomb Shaped Slotted Ground Microstrip Patch Antenna Design for Broadcasting Fixed Satellite, Mobile Satellite and Downlink Frequency Applications.
6. Neville, R.M., Chen, J., Guo, X., Zhang, F., Wang, W., Dobah, Y., Scarpa, F., Leng, J., & Peng, H.X. (2017). A Kirigami shape memory polymer honeycomb concept for deployment. Smart Mater. Struct.
7. Tok, R.U., Ow-Yang, C., & Sendur, K. (2011). Unidirectional broadband radiation of honeycomb plasmonic antenna array with broken symmetry.
8. Barfield, W.L. (1994). The Design And Analysis Of A Phased Array Microstrip Antenna For A Low Earth Orbit Communication Satellite.