The solar panels were a joint effort between the Solar Team and many other Solariders. Kaia Liisa Hakk, one of Solaride’s female engineers, was responsible for manufacturing. She managed to get the teams main objective, which was to manufacture functioning solar panels, done in the fastest compared to other teams and their tasks. The Solar Team also received help from fellow engineers as well as marketers, leading to around 10 people being involved in the manufacturing of 5 solar panels.
In simple terms, a solar panel is a large plate that is made up of tiny solar-powered batteries that produces solar energy and a solar cell, or photovoltaic cell, is an electrical device that converts the energy of light directly into electricity. The car’s roof has 294 single crystal silicon elements acquired from Maxeon that are then equally divided into 5 solar panels.
Installing the solar panels on the roof of the concept car. On the photo: Katriin Kristmann, one of Solaride’s engineers
Solaride found out about Maxeon’s single crystal silicon elements thanks to Lightyear, a Dutch solar car producing giant, whose roots as a company also lead to a student project very similar to ours. Andres Nõps, the head of the Engineering Team from our first season, says that Lightyear’s representatives were the ones to suggest Maxeon’s single crystal silicon elements based on their own experience. This advice was also factually confirmed - when regular elements’ effectiveness was tested, they only clocked out at around 21-22%, but Maxeon’s elements clocked in with percentages of 24.3% and higher. Nõps mentions that the dutch ran their own tests, where they received effectiveness levels of over 25% leading to an obvious choice regarding Maxeon.
Maxeon Solar Technologies is an enterprise that is currently one of the global leaders in solar innovation which operates in more than 100+ countries. Co-operation with a tycoon like Maxeon is a massive morale-boost for us at Solaride. The leader of the solar panel team Kaia Liisa claims that Maxeons single crystal silicon elements are the most effective out of all the options on the market - one element costs 10.25 euros.
Kaia Liisa Hakk, the leader of the solar panel team, soldering silicon elements using a clamp designed by herself
The manufacturing process for the solar panels began in December 2021 and was completed in August of the same year. Let’s have a deeper look into how the construction took place.
The first thing our Solar team had to decide on was the amount of solar panels needed for the project. The choice was made using information from an MPPT, or Maximum Power Point Tracker, which simply put is a converter that changes the electrical current produced by solar panels into energy that can be used by solar batteries.
An agreement was then quickly reached that the optimal amount of solar panels would be five and that the single crystal silicon elements would have to be distributed amongst the panels as equally as possible, so the outgoing current would be even.
On the left: The original blueprint for the positioning of the elements on the roof of the solar car. On the right: the current positioning
The clamp or fastening tool, that Solaride’s engineers designed was specifically made with the intention of soldering solar elements together as precisely as possible in the correct position. The construction of the clamp started in December and the manufacturing process took many months, until the final product was ready to use.The first task in the development of this clamp was, well, the development. Kaia Liisa says that the team had many drafts and ideas, and that the prototype looked completely different from the finished product. During this endeavor Kaia Liisa had her first opportunity ever to design a clamp, this meant that she frequently asked for advice from our engineering mentor Tiit Liivik as well as other Solaride engineers. Her goal was to make a clamp that would not only work for solar elements, but would be useful in the future as well. The base of the clamp was made out of aluminum, as it is a great heat conducting metal.
While testing out the product our team came prepared and thought a few steps ahead, installing resistors on the clamp itself that would release heat if an electrical current was sent through them. This is important, because soldering creates something called thermal shock when it’s being done on the connections of the solar elements- the tin heats up to 250 degrees Celsius but the element itself stays at room temperature. Thermal shock also increases the chance of the element itself fracturing, which is why it was important that the areas which were being soldered were at an equal temperature throught-out the process.Kaia Liisa says that the final version of the clamp came through a rigorous process of trial and error. After making the base for the prototype clamp, it was understood that something needed changing, but they weren’t quite sure what exactly. They hypothesized for example that the space between the jaws should be wider. Our friends over at INTAR eventually came and helped us out with their laser cutter, thus providing us with a proper base. But our clamp also had to be tested out before we would make the final product.
The team got together at Viljandi at least once a month, if not more, for the purpose of testing. Getting a feel for the soldering was time consuming and rough to say the least, as they didn’t want to mess up the expensive hardware. This meant that the team used elements that were ten times cheaper or just cheaper Maxeon alternatives to practice soldering.Rows of solar elements, all connected by connectors . The elements on the picture are facing backwards, because the connections for Maxeon elements are located on the back. Photo: Tiit Liivik
Kaia Liisa Hakk: “It bewilders me to this day, that we genuinely managed to solder the solar panels. This process is something that requires extreme precision and I am honestly surprised they actually worked and produced an output necessary for us, as we had 7-8 different people working on this project simultaneously.”
Visits to the Solarstone factory were frequent after the initial testing phase, when the manufacturing of the panels were just beginning, as it was time to finally make a finished product. Our solar panels were made up of five layers: a transparent film on the back, EVA (Ethylene-vinyl acetate) glue, solar elements, more EVA and the frontal transparent film.
Maxeon elements had to be soldered by hand, making the entire process very time consuming. Our team estimated that everything to do with the solar panels eventually equated up to a price tag upwards of 10 000 to 15 000 euros, making this the most expensive part of the whole project.
Lamination process is on-going. From the left: Tiit Liivik, Andres Nöps, Mait Kukk
Silicon elements must be handled with care - they are easily susceptible to fingerprints and bending and can break if tapped on too heavily. If even one element breaks, it can affect the entire production capacity of an entire panel. During the soldering process the “+” and “-” is marked so that it’s easier to double-check the connections later on. With this kind of work it is also extremely important to check that the elements themselves are functional and that the solar elements all produce power.
The layers of a solar panel on a sheet of glass. Photo: Tiit Liivik
The materials are cut with little room for error and expert precision. To make the solar panels, a glass surface is needed. This has to be continually maintained and cleaned from glue residue, because this may harm the solar elements.
From the left: Armin Mere, Katrin Kristmann and Andres Nöps making their final preparations before sending off the solar panels to be laminated. Photo: Kaia Liisa Hakk
While setting up the elements it is important to remember that they are placed equally apart from each other and that they are placed in the center of the material. While making the series connections it is important to check if the elements that are glued together with EVA aren’t already melted in place before they enter the lamination machine. And as always, you must check if the connection is working before the lamination process begins.
A solar panel entering the laminator for 17 minutes
Before the second layer of EVA and the final layer of transparent film is added, double-check for small pieces of dust or anything else that may ruin the lamination process, only then are the aforementioned layers added to the pile. They then proceed to go into the laminator alongside the solar elements for 17 minutes at 140 degrees Celsius. After that, remove the panel from the laminator and let it cool off. A solar panel has just been born!
The Solar Team is a wonderful example of how preparation and training leads to stunning results. The Solar Panel Team reached its goal - making the solar panels - much earlier than the other teams at Solaride achieved theirs. The Solar Team also provided other solariders with the opportunity and experience of a real manufacturing process, regardless if they had an engineering background.