Energy, and new methods of harvesting renewable energies are becoming very important and heavily researched in today’s energy thirsty world. We have identified thermoelectric technologies as an innovation that could potentially be a game changer in power generation. These thermoelectric modules are still in their infancies as a technology, and are extremely inefficient at power generation. Our goal is to unlock the true potential of thermoelectric power generation by increasing its efficiency.
This device is planned to be compact enough to be easily moved by a single user. It will include an input for sunlight, that will then be converted into heat. In order for the thermoelectric modules to create energy, a temperature difference will need to be provided. This will be achieved by having heat generated from sunlight on one side of the module, and some source of cooling and heat removal on the opposite side of the module. The energy created will then be used to charge an internal battery, that can be used even when the generator is not functioning, and then be used to charge electrical devices such as a cell phone. The user will have to turn on the device, but it should be able to run with minimal input from the user. The goal is to design a portable and safe power generation module that provides reliable and renewable power.
Proof of Concept
With this Proof-of-Concept (POC) device, the team is attempting to answer two main questions. The first question is how the heat generated from a pin point heat source generated by magnified sunlight would distribute itself through a thin piece of copper plate. The second question the team is trying to answer is if the heat distribution through copper will still create a high enough temperature differential to generate useful power with a thermoelectric generator.
The POC will be constructed from a 6” x 6” piece of 1/8” copper plate, one PVC Fresnel lens, four wooden dowels to secure the lens a fixed distance from the copper plate, thermal interface adhesive, and then a thermoelectric generator (TEG) module to show that the thermal energy from concentrated sunlight will be enough to create useful power. For the final device, the team has established the ability to charge a cell phone as a benchmark, so the generator will be required to produce a minimum of 5 Volts and 3 Amps. For the purposes of the POC, the team needs to show that these benchmarks can be reached by using less than 15 TEG modules.
The POC will be tested in two ways. First, the team will mark various points on the bottom side of the copper plate, where temperature readings will be made. Using an infrared thermometer, the team will then take temperature readings at the predetermined locations over a set amount of time, showing a temperature distribution with respect to time. After this test has been completed, a TEG module will be attached to the bottom side of the copper using a thermal interface adhesive. Voltage and current readings will then be measured over time to give the team an idea of if the generator will be able to create the required power to meet the projects benchmarks. This POC will help the team fine tune the final design, as well as identify any flaws in the concept or obstacles that will prove to be more difficult to overcome than others.
The purpose of the STEG (Solar to Thermo-Electric Generator) device is to create a clean renewable source of energy from a solar input. This is not a traditional solar panel device that is on the market. The STEG system focuses sunlight to heat a small thermoelectric module that uses a temperature difference between two ceramic plates in order to create electricity. This process is designed to be a new and more efficient way of extracting solar energy. The project/ team hopes to promote the thermoelectric technology. The thermoelectric generator brings value to the customer by providing clean and renewable energy completely off the grid.
Cut enclosure and support boards to size. Be careful when using rotary saw to keep all extremities away from blade.
Slots for lens and polycarbonate front pannel were cut using a jig and hand router. A 1/8” bit was used for the front pannel and a 1/16” bit was used for the lens.
Holes were drilled for the mounting nuts on the side panels. A 3/8” drill but was used. The insert has an outer diameter of 0.395”, so use of a smaller drill bit ensures a snug fit. The inserts were installed by hammering them into the hole.
Pilot holes were drilled in all enclosure panels using a 3/32” drill bit with a counter sink attachment. The holes were drilled slightly deeper than needed to ensure the holes would have enough room to be filled in later. 1 ½” #6 wood Screws were then used to join the enclosure boards together.
Once the enclosure was fastened together, holes were drilled in the back panel of the enclosure for the water tubes leading to the heatsink. The outer diameter of the tubing is ½”, but a 5/8” bit was used to allow for ease of installation as well as extra room for the electrical wires coming from the thermoelectric module to exit the enclosure.
All screw holes and exterior joints were then filled with Bondo. This ensured there would be no material shrinkage, and that the surface would be easy to sand smooth.
All joints and Bondo were then sanded smooth using an electric sander.
The support arms were fastened to the support plate using the same 1 ½” #6 wood screws used on the enclosure. 3/8” holes were drilled on the upper portion of the support arm for the ¼” threaded support rod.
The enclosure and support sub assemblies were put together to ensure movement and funtionality.
The thermoelectric module and heat sink assembly was fastened into the base using ½ “ #4 pan head wood screws.
All surfaces were whipped with denatured alcohol and a lint free cloth to remove particulate. A thin polyurethane coat was applied to the exterior of the enclosure to ensure a smooth painting surface.
Finally, all surfaces were finished with black spray on rubber to ensure a weatherproof and watertight seal. Though the device itself is not weatherproof, the extra protection on the enclosure and support will prevent the wood from expanding or becoming waterlogged in the event that the device becomes wet.
Testing and Results
- Gather All required materials for testing: Bucket, water, prototype, Water input/output hoses, pump and power supply, extension cord, multimeter with hook leads.
- Insert water input/output hoses in the device. Connect to heatsink. Attach pump to one hose and submerge in water bucket.
- Attach hook leads from multimeter to thermoelectric module positive and negative wires.
- Connect extension cord to wall outlet, but do not plug in pump.
Testing will be conducted in stages, with voltage measurements being made and recorded every minute for at least 30 minutes. A team member will record the measurements in real time on an excel sheet with a graph present, so as to visually asses the establishment of a voltage equilibrium. The first stage will be a dry test of the device (no water flow to heatsink) to establish that everything is connected correctly and the TEG is outputting DC voltage as expected. This phase will also be used to establish if an equilibrium output will be reached without the use of the heatsink. Phase two will be the wet test (Water flow to heatsink). Measurements will continue to be made every minute, and an equilibrium output will be established. Phase three will consist of short iterations of both phase one and phase two, to validate the previously established voltage equilibriums.
After following the previously established testing procedures, the following data was collected and formatted graphically.
The data shows that during phase one, an equilibrium voltage of approximately 0.5V was established. This value is greater than any member of the team had expected. Much to everyone’s surprise, the voltage immediately shot up to approximately 2.5 V once the pump had been turned on. This value fell to about 0.7V when the team realized the lens was being partially blocked by an obstruction. The voltage rose again to establish an equilibrium voltage of 0.87V. The pump was then turned off, and a sharp drop back to 0.5V was observed. Once equilibrium had again been established, the pump was switched on again where a similar but lower voltage spike was recorded. Once the voltage appeared to be approaching the previously established equilibrium of 0.87 V, the test was ended.
These results far surpass those obtained from both of the teams previously tested Proof of Concept (POC) devices. The team had established an equilibrium voltage of 0.5V as the benchmark for a successful prototype, so the team was extremely pleased with the results. This device exceeded the standard for success by over 70%, and the team believes the device to be scalable. A larger lens to increase the energy input to the device is believed to yield a higher equilibrium temperature. The team also believes that perhaps reducing the water flow through the heatsink will also raise the equilibrium. Because the date collected in test one so clearly should the voltage equilibriums and trends, the team decided to only test the device once.
This device was intended to be an alternative look at collecting solar energy, and to assist with the transition from fossil fuels to renewable energy. It was marketed towards the portable energy market, but from testing, the team no longer believes this technology to be a suitable competitor to traditional photovoltaic or solar-thermal sources of energy. While the Device cost under $400 to manufacture, it does not produce enough electricity to effectively charge a portable battery as previously intended. It is also significantly larger and heavier than some portable solar chargers already on the market today. By making the lens for the device larger in order to increase the available power, the device would become even more expensive and heavy. The device also requires constant adjustment to keep the sunlight focused on the thermoelectric module. This would be entirely too cumbersome to effectively compete with similar existing products. Although the device is not a suitable market replacement for solar cells, the team learned much about designing and optimizing a device. The lessons learned from this project will be carried through the careers of every team member, and they have all become better engineers because of it.
Meet the Team
Mitch Warden is a mechanical engineering student at the University of Nevada, Reno. He is 23 and was born and raised in Reno, Nevada. Mitch is graduating in December of 2017 with a Bachelor of Science in Mechanical Engineering and a minor in Entrepreneurship. Mitch is currently a Research and Development Engineering Intern at Hamilton Company. Mitch’s hobbies include riding motorcycles, skiing, and fishing.
Zach Ballen, age 23, is a student at the University of Nevada, Reno studying mechanical engineering. Zach is graduating in May 2017 with a Bachelor of Science and a minor in Mathematics in December of 2017. He was born in Las Cruces, New Mexico, but grew up in Cameron Park, California. Before UNR, he spent two years studying general education at Folsom Lake Community College. After obtaining his degree, Zach plans to go in the field of renewable energy.
I was born in Long Beach, California and grew up in Buena Park, California. Living in southern california I began riding motocross for most of my youth until high school. I graduated from John F. Kennedy High School where I played football all four years. In the time of playing football, I became a varsity captain while acquiring leadership and teamworking skills. After High School I enrolled into the University of Nevada, Reno where I began pursuing a mechanical engineering degree. I am currently a senior at the university maintaining a 3.0 GPA and will be graduating in the Fall of 2017. Once graduated, I plan to pursue my professional engineering license in HVAC and refrigeration or thermal and fluid systems. This last summer of 2016, I was an intern for SmartWatt Energy Inc. where I designed mechanical plans for HVAC renovation. The ultimate goal is to acquire a professional engineering license and open a privately owned engineering firm.
Andrew Sheets is a 21 year old mechanical engineering student at UNR. Grew up in the San Francisco bay area. Hobbies include skiing, playing basketball, mountain biking, and more. Interested in pursuing renewable energy development and aerospace engineering.
Kevin Whitehouse is a senior, majoring in Mechanical Engineering at the University of Nevada, Reno, and is expected to graduate in December of 2017. He was raised in a military home, so he grew up in many different places, but has lived in Vacaville, California since 2003. He attended Solano Community College for two years after high school, after which he attended Arizona State University for a semester before settling in at the University of Nevada, Reno. During the summer of 2015, he worked as an undergraduate researcher in the Composite and Intelligent Materials Lab at the University of Nevada, Reno. In this position, he primarily performed tasks in design and fabrication, but also assisted with material testing and data collection. In addition to this research experience, he has also maintained above a 3.0 GPA during his studies. After graduation, Kevin plans to pursue a commision as an officer in one of the branches of the military and become a pilot, like his father and grandfather. He would eventually like to become a test pilot or work in aviation as an engineer.
Team 28-Electric Magma would like to thank our faculty advisor, Prof. Yan Wang, for his assistance on the project. Prof. Wang has been assisting the team with conceptual and design related issues for the entire ten months that it has taken to complete. His contributions to the success of the prototype have been innumerable.
The team would also like to thank our course instructor, Nick Maus, for not only teaching the class, but also donating the thermal paint that was used on the top of our thermoelectric module. Without this paint, the team would not have received the results that were collected.
Finally, the team would like to thank all of the teaching assistants- Patrick Stampfli, Nick Zerbel, Kai Carl, and Pedram Safaei- that assisted with the class. Without their hard work grading assignments, placing purchase orders, and giving technical advice, the project would not have been as successful as it was. Thank you all so much for your contributions to our project. We are immensely grateful.