Solar solutions: ‘MacGyver engineering’ extends PV panel life

Seth and Hanrath designed a package filled with sodium sulfate decahydrate – also known as Glauber’s or Globus salt, which is commonly used as a horse laxative – that attaches to the back of a PV panel. When the panel reaches 32.4 degrees Celsius (90.3 degrees Fahrenheit), the material melts and starts passively sucking heat from the panel, cooling it in the process. At night, when the temperature drops, the material releases the heat and transitions back to a solid.

Glauber’s salt is complex to engineer, but the material is inexpensive and has the right properties for New York state temperatures. The material also happens to be the natural byproduct of battery recycling, which means that repurposing this waste makes it a sustainability twofer.

To build a prototype, Seth took a decidedly DIY approach. He went to Lowe’s and bought barbecue bags, of the sort used to grill vegetables, and ordered a few supplies off Amazon. He placed about 1 kilogram of Glauber’s salt in a test bag, reinforced it with duct tape and attached the package to the back of a PV panel with Gorilla Glue that also contained metal shavings, to boost its conductive properties.

“It’s economical. It’s easy to put together,” Seth said. “It’s a very bootstrapped way of looking into how we can do things without overcomplicating the technology.”

Hanrath had plenty of modules to experiment with. In 2019, he rescued 1,200 damaged panels from a utility-scale solar farm near Ithaca that were bound for the landfill. Since then he has worked with the student group Cornell University Sustainability Design to refurbish hundreds of them, usually with polyurethane, resin, epoxy and good old-fashioned elbow grease. Such efforts highlight a perennial challenge of photovoltaic design. Even well-functioning panels can’t avoid the landfill forever.

“In terms of the energy transition, and especially in solar, it’s not an issue of just installing more panels, but to seriously ask the question of, have we looked far enough ahead?” Hanrath said. “The panels that were installed 20 years ago will be obsolete in about 10 years, and it’s going to be thousands of tons of waste if you don’t do it right. The thing that I’m hopeful about is that more thought is given to design for recycling, design for sustainability, and how do you close the materials loop in 20 years?”

Seth and Hanrath built their package prototype last summer, and in the first week of August they set up a public demonstration panel in front of Olin Hall with a thermal imaging camera to capture the process.

“We could clearly see not only the reduction of temperatures while the sun was shining, but also evidence of the PCM solidifying and releasing heat when the sun set,” Seth said.

The panel’s average operating temperature during the day was 43 degrees Celsius (109.4 degrees Fahrenheit), and the prototype succeeded in reducing the temp by an average of 5.2 degrees Celsius (9.3 degrees Fahrenheit).

The researchers estimate that a PCM package could therefore increase a panel’s lifespan by 75%, extending its usage from 20 to 35 years. That would lead to an economic benefit of about $280 per panel.

The prototype couldn’t last nearly that long, given the disposable nature of barbecue bags, but it succeeded as a proof of concept, according to Seth, who envisions creating weatherproof packaging and optimizing the PCM so it can function across a larger span of temperatures and seasons.

“This is where material science comes into play, to kind of look at what we can do to adjust this phase-change material, to tune its properties to match our use case,” Seth said. “There are a few techniques that can be used to ensure that it performs well after one, 10, 100, maybe even 1,000 cycles, and has that same heat storage capacity.”

The Engineers for a Sustainable World (ESW) student team is now working with Seth on the project, which has been dubbed Solar-Tune, short for Smart Optimized Lifecyle Advances for Retrofitting Thermal Upgrades Next-gen Sustainable Energy.

The road to technology development, commercialization and public adoption is long and unpredictable, but Seth and Hanrath remain pragmatic in their approach.

“We’re trying to be as scrappy as we can to make it work, whether it’s using barbecue bags or a phase-change material that can be sourced rather economically easily and has lower emissions associated with it,” Seth said. “We’re just trying to keep that approach in mind while we progress in this journey, and we make prototype on prototype and eventually perfect the technology.”