The usage of discarded solar panels in this manner will help to address the problem of solar photovoltaic waste
A group of scientists at the Indian Institute of Science (IISc), Bengaluru have found a new use for discarded solar panels: to be used as building material.
The group has developed a few products to extend the useful life of End-of-Life (EOL) panels by another 20-30 years.
“In 2007, we had built a demonstration building unit,” Monto Mani, associate professor, at IISc’s Centre for Sustainable Technologies, said.
“From this project, we had a few old panels that were scrapped off. So, we decided to put them to use. And this is how the new facility was built entirely out of EOL photovoltaic (PV) panels and a few other products — like a table and chopping board,” he added.
The usage of discarded solar panels in this way will have an important use.
India has an ambitious solar power programme but no proper policy or mechanism to address the waste from solar panels which may impose serious health and environmental threats. It is estimated that by 2050, India may generate 1.8 million tonnes of solar PV waste.
The cost of building the super structure is between Rs 250 and 500 per square foot (sq ft) for a MS frame structure (procured new) but the cost could go down by another Rs 50-100 /sq ft if the material for framing is sourced from a scrap yard, Mani said.
For instance, a 1.6 x 0.8 metre waste panel weighing about 12 kilograms could cost about Rs 200. This cost could increase with demand.
But what about the safety of these panels as building material?
There two types of panels. The silicon-based have a toughened glass top, with a polymer (Polyvinyl Fluoride or PVF) back sheet while the other thin film panels have a glass top and a glass bottom (glass-glass) configuration.
The majority of the EOL panels that are currently emerging are in the first category, with waste from the latter expected within this decade, said Mani.
“Glass has traditionally been the safest of materials. The panels are designed for a working life of 25 years, and the back sheet is extremely durable,” Mani said.
He added: “We are currently attempting to study any possible toxicity associated with short- and long-term exposure to back sheet in the indoor environment. Since we are unsure of this, in the current set-up as a building material, we are using two panels placed back-to-back, with glass facing outside and inside.
“Other configurations are glass on the outside with plywood inner lining or even an earthen wall to offset the slightest of risk associated with indoor exposure to PVF.”
The glass-glass configuration PV panels offset the risk completely and would be much safer to integrate into the buildings.
Any breakage leads to a shattering (like in an automobile wind shield) of the toughened glass cover, generally exposing the polymer (ethylene vinyl acetate or EVA) that encapsulates the PV cell.
EVA is stable. However, its long-term environmental implications, when disposed, are still emerging. When the EVA is ruptured, the risk of leaching from the cells is high (depending on where the damaged cells are disposed), Mani cautioned.
Points to remember before using panels for product design
1. Provide a strong frame to strengthen the edges
2. Avoid damage to the rear sheet
3. Sealing (with silicone adhesive) the exposed contact at the junction box
4. Avoiding any impact from a sharp object on the toughed glass
5. Working with the available size of PV panels (as these cannot be cut/resized)
6. Design in such a way that the indoor environment or product is exposed or in contact with the glass part of the PV panel
7. Most EOL panels still generate electricity. Innovative ideas could be brought in to harness this energy for low grade uses such as charging mobile phones and operating indoor lighting.
8. When used in a roof or wall with high solar exposure, a thermal mass backing such as plywood or earth is recommended.
A sanitation unit entirely out of EOL PV panels is expected soon. The team also plans to build a rapid self-powered sanitation unit which can power its own flushing system, lighting and possibly disinfection as well.
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