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We all know the sun is a great source of heat, and it takes heat to process plastic. So what if the two could be combined to create an innovative molding process that doesn't use fossil fuels? LightManufacturing LLC, founded in 2010 as a solar thermal technology company, announced last month that the United States Patent and Trademark Office issued it a patent covering the use of concentrated solar thermal energy for molding plastic.

Clare Goldsberry

April 22, 2014

5 Min Read
Firm receives patent for zero-fuel solar plastic molding system

The proprietary technology, Solar Rotational Molding (SRM), allows low-cost manufacturing of large plastic objects like water tanks and boats without the use of fossil fuels. The patent describes the use of heliostats (sun-tracking mirrors) to concentrate heat in a plastic molding system.

"Our technology eliminates the energy costs of roto-molding or vacuum-forming plastic parts," said Karl von Kries, LightManufacturing founder and CEO, "while offering opportunities to simplify and reduce the cost of the molding system."

A mechanical engineer by training, von Kries worked for several in the plastics industry. "It always struck me as strange that one moment you're investing all this energy to heat this mold, then the next moment trying to throw the heat away as fast as possible," von Kries told PlasticsToday. "After moving to California, I was using solar for heating water at my house. I thought, ‘why can't we use solar to melt plastic and not throw money out the window during the cooling phase?'"

Temperatures can reach whatever is needed to melt the resin being used, von Kries explained. For more heat, all that is required is deploying a larger heliostat array that targets the molds. Cooling time (de-targeting the array) is at 50% of the heating cycle time. "Interestingly, we're seeing more rapid cooling than in traditional rotomolding," said von Kries. "We think this is due to less total mass at ‘oven temperatures.' In other words, we carefully target the mold with the heat beam, and do not heat the rest of the machinery. That means the mold is the hottest object in the system, and there is less heat to remove from the molding armature, the surrounding chamber, etc."

At first, von Kries thought that surely someone else had already developed this technology using solar, but to his surprise no one had. So he set about to prove that the technology was possible and could actually do the rotomolding process. "We've run the financials on the process and learned that it's not only technically feasible but highly economically competitive," he said.

The company's SRM systems are delivered pre-integrated into 20-foot ISO shipping containers, and can be dropped onto unimproved land. No building, concrete pad, or grid energy connection is required. "This ease of installation means customers can put inexpensive production capacity in new markets, or put manufacturing close to customers to reduce transport costs," von Kries explained.

Heat for melting the plastic powder for the rotational molding process comes from an array of the company's H1 heliostats, and a photovoltaic array on the roof of the container provides energy to rotate the molds and operate other equipment. The company estimates that the now-patented processes can be deployed on over 49% of the Earth's land area.

One interesting point, von Kries notes, is the impact on logistics. "Companies that mold these very large rotationally molded parts such kayaks, canoes, trash bins, and large containers, have a 200 to 300 mile radius in which their shipping is competitive, but beyond that distance, shipping becomes cost prohibitive," he said. "Locating smaller production cells close to customers means you can have essentially a lightweight ‘factory in a box,' and can justify the cost of a solar system. It reduces the costs significantly."

While shipping costs are important in the U.S. and other developed countries, the SRM technology is even more impactful in places in the world that do not have good infrastructure, von Kries explained.

"There's a host of benefits in addition to totally eliminating the cost of fuel, which is variable," he explained. "Molders are at the mercy of energy markets forever. If you have the advantage of getting rid of the cost of energy and pollution, and getting lower equipment purchase costs along with the ability to put these SRM cells in many more places than a traditional factory, it will allow rotomolding to spread globally, and expand well beyond its current market where it's constrained by capital and location."

Von Kries added that it is possible to retrofit the heliostat array onto an existing building if a rotomolding company wants to implement the solar technology, however some locations might not have a logical place to put a heliostat array. "We'd have to determine if it's feasible," said von Kries. "Some have their rotomolding machines deep inside a building, which would make it more challenging to get the light to them. But if the machines are located on an exterior wall, it's more feasible and in some cases can be retrofitted to existing equipment."

While many solar technology firms develop methods for generating electricity, LightManufacturing differs by concentrating solely on applying solar heat to manufacturing processes. Currently, LightManufacturing is working on additional plastic processes for its technology. "We started with rotational molding because we know that process the best," said von Kries. "The next phase will be vacuum forming, in which solar technology will be used to soften the sheet prior to moving it over the mold for forming. We have several more patents in the pipeline. The plastics industry is first area of focus, but there are more areas where we can use thermal energy that we're pursuing."

LightManufacturing was a winner of the SPE GPEC's Best Emerging Technology alongside some big names such as Ford and Dow, von Kries noted.

"The overarching message is that solar has the power to transform the plastics industry in many ways," von Kries stated. "Using older technology with newer technology to improve manufacturing and reduce costs with thermal energy in an industry that uses heat for all its manufacturing - the impact is tremendous. The bottom line is that solar thermal can do a lot more than make hot water."

About the Author(s)

Clare Goldsberry

Until she retired in September 2021, Clare Goldsberry reported on the plastics industry for more than 30 years. In addition to the 10,000+ articles she has written, by her own estimation, she is the author of several books, including The Business of Injection Molding: How to succeed as a custom molder and Purchasing Injection Molds: A buyers guide. Goldsberry is a member of the Plastics Pioneers Association. She reflected on her long career in "Time to Say Good-Bye."

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