An Arduino controlled linear Fresnel reflector

Taylor Grubbs and Liam M. Duffy, Department of Chemistry & Biochemistry, the University of North Carolina at Greensboro, Greensboro NC

An Arduino controlled Linear Fresnel Reflector

Submission is for research1Student author - Taylor Grubbs, Undergraduate Physics

Faculty Advisor - Dr. Liam Duffy Department of Chemistry and Biochemistry, UNC Greensboro

Student contact info: (919) 498-4462 tegrubbs@uncg.eduAdvisor contact info: (336) 263-8015 liam_duffy@uncg.edu

We have designed and constructed a simple, low-cost method of maximizing the amount of solar energy captured by a single solar vacuum tube using a linear Fresnel reflector. This is accomplished through several features. The first of these is giving the concentrator the ability to “follow” the sun, that is, the mirrors and the frame of the reflector automatically rotate as the sun moves throughout the day. The movement of these is controlled by modification of an Arduino solar tracking program created by the institute of Earth science research and education2. Instead of using light-sensing hardware, the Arduino microcontroller continuously calculates the sun’s position with the aid of a battery controlled Real Time Clock (RTC). This program was modified to control the motion of a small stepper motor that rotates a timing belt to which each mirror is linked. The second feature is that the frame of the collector is made entirely of prefabricated T-slotted aluminum, making the reflector both lightweight and durable. Each mirror along with the vacuum tube itself are held by 3-d printed plastic components which were designed and printed in our lab. Assembly of this model is simple and relatively short, making it appealing to the average solar hobbyist or experimentalist. We hope to use this device to power a Duplex Stirling- engine-heat pump that would reduce heating costs for a typical home. Further work on the device can also be done to create a much more consumer friendly and marketable product. The device could also be modified for solar power generation and/or solar desalination. In summary, using modern microcontrollers, pre-made aluminum framing, and simple 3-d printed parts we have developed a new device that provides consumer friendly access to solar energy.

1. This project was funded by a Triad Interuniversity Project (TIP) grant as part of Four University Solar Consortium between Wake Forest University, Winston-Salem State University, NC A&T State University, and UNC Greensboro. 2.Brooks, D. Arduino Uno and Solar Position Calculations. Institute for Earth Science Research and Education. Pennsylvania. February 2015.

Abstract

Solar Vacuum Tubes

Appalachian Energy Summit, Appalachian state University, July 13-15, 2015 Boone, NC

Control Applications/Conclusion

An Arduino Uno calculates the position of the sun and updates mirror orientation via a small stepper motor, providing maximum collection throughout the day. This single motor controls a pulley that rotates each of the 29 mirrors of this model. A sample of the calculation code from the Institute for Earth Science research and education is shown below.

Linear Fresnel reflector

Solar vacuum tubes offer a cheap method of transporting energy reflected by the LFR.Heat is captured by the vacuum tube and transported via a vapor to an external reservoir.The combined reflection of the mirrors will be delivering about 3.2 kilowatts to the solar tube.

This Linear Fresnel reflector was designed with 5 purposes in mind:

1)Operation of a Stirling engine

2)Hot water generation

3)Heated oil generation for thermal heat storage and home heating

4)Evaporative water desalination

5)Possible incorporation of photovoltaic cells

It is these applications that this LFR model will be adapted to withfurther research.

Our linear Fresnel reflector directs all light incident upon a surfaceto a single line. This model is designed for use with residential housing as modeled below.

Solar Vacuum tubes

The collection surface area of this model is about 4.3 meters.

The user must enter only their latitude and longitude. The time information is controlled by a Chronodot® Real Time Clock. This clock is batterypowered so even in the event of a power outagethe LFR will not lose its place.

Note the use of 3-D printed parts

All of the models shown here depict the LFR with its tilt fixed at one angleour most final design enables the user to adjust this tilt to compensate in the change is solar elevation.