LightManufacturing uses solar power to rotomold off the grid

Arroyo Grande, Calif.-based LightManufacturing Inc., a machine builder and contract manufacturer, has developed a solar rotational molding system that improves performance and portability and could take clean technology to new heights.

The SRM4 — the name refers to the project being its fourth-generation system — has the most powerful heliostats, wirelessly controlled, sun-tracking mirrors to concentrate solar-thermal power, ever developed by LightManufacturing, and the system is so compact it can be transported as a factory in a box.

"At 14 feet high, the SRM4 is the physically largest thing that you can get on the federal highways and under the bridges. We pushed it to the max," company founder Karl von Kries said in a phone interview.

The SRM4 is a containerized system capable of molding kayaks, industrial pipes, architectural elements, road barriers and products as large as 2,000-gallon water tanks with a significant savings on energy and utility costs. The patented system needs no natural gas, propane or water, and it can process thermoplastics used in traditional rotational molding, such as polyethylene, polypropylene, PVC, nylon and polycarbonate with no emissions.

During the SRM process, mirrors focus thousands of watts of solar heat on a rotating mold, while photovoltaic cells provide electricity to run motors and other equipment.

The mold is heated radiatively, like standing in front of a space heater, as opposed to convectively, such as sitting inside an oven. This means the SRM4 can have complex electronics in the chamber, including servo and stepper motors and systems to monitor temperature, mold surface, mold position, beam intensity and more.

"The time has come for zero-carbon molding that's incredibly high quality," von Kries said.

He started the central coast company in 2010 to focus on technology to replace the use of fossil fuels in industrial processes with concentrated heat. Since then, new algorithms, better heliostats (branded as H1), and more advanced software, electronics and sensors have improved performance and quality.

"This is not some aspirational technology that you really hope it works and then you never hear about it. This is competitive and ready for prime time," von Kries said. "We've perfected this to the point where we're making large products with very low porosity and very high impact strength."

As a contract manufacturer, LightManufacturing makes products and parts for theme parks, the military and other customers.

As a machine builder, the company now will license the technology to partners wanting to set up factories in a box at their own site to expand capacity or get closer to customers to reduce transportation costs.

Forty-nine percent of the Earth's land area is suitable for an SRM4 operation, and in North America, the systems could change the economics of rotational molding, von Kries said.

"The inputs of heat, plastic, labor and capital expenses have been essentially fixed for 50 years. While there's been some innovation, the economic fundamentals haven't really changed until now," von Kries said.

"We're going to delete your cost for energy. How does that change your business? And we're going to make this factory much less expensive and much smaller. You're able to put it close to customers. Maybe you had to ship products some 300 miles. Now you can cost-effectively put this right in their backyard."

The business case for the SRM4 is strong and entry barriers are low, von Kries said.

"The idea of being able to decarbonize is great, but if you can decarbonize and save on capex [capital expenditures] and save on opex [operating expenditures] at the same time, why not," he said. "Even someone who doesn't care about climate change should still want this because of the competitive advantages of a cheaper, better process."

Setting up the SRM4 system can be done quickly on undeveloped land and cost-effectively. No concrete foundation needs to be poured. No utilities have to be hooked up.

Von Kries estimates the capital expenditures for SRM is 10 percent of the machine, building and infrastructure costs of a new traditional molding facility. Then, depending on local market and energy conditions, the product costs 15-30 percent less to make with SRM than traditional equipment, von Kries said.

In addition to California, LightManufacturing has a facility in a lava field of Kona, Hawaii, using solar-thermal energy to manufacture food-grade polyethylene water and aquaculture tanks for sale directly to consumers. Production of the tanks is overseen by a single operator, who can control the system by smartphone or laptop through a web browser, von Kries said.

The operation produces three sizes of tanks (290, 500 and 950 gallons) mostly for customers on the islands of Hawaii, Maui, Oahu and Kauai.

"Hawaii has very strong demand for water tanks with much of the population using rain harvesting for washing, drinking water and sanitation," von Kries said. "In many communities there is no city water option. Our factory there is able to sell water tanks at a 30 percent price advantage vs. traditional molders, who have to pay for very expensive imported propane to run their factories or vs. tanks imported via ship from the mainland, which is also very expensive."

LightManufacturing's Hawaii operation serves as a great example of a market where the SRM process has advantages over the status quo, von Kries said.

"There are a lot of similar markets where traditional molding is difficult due to logistics or energy costs," he said. "Recall that the energy cost component of rotomolded products is 15-30 percent, depending on the market, so our ability to eliminate this cost entirely offers a big competitive advantage."

In Hawaii, LightManufacturing can best serve the market by selling directly to consumers as opposed to contract manufacturing, von Kries said. Going forward, other business arrangements, such as licensing, will be considered.

"We have kept the SRM technology in-house until now. With the release of our flagship SRM4, we are opening the door to collaborations with other processors and brands seeking reduced part cost and improved sustainability," von Kries said. "We're interested in licensing and other financial models to get the technology into the hands of plastics processors that want to add it their existing facility."

The SRM4 is the largest, most powerful — yet quietest — system built by LightManufacturing. The processor only needs to add molds and plastic.

The "factory" system consists of two arms, a solar power system with panels and advanced battery, a wireless computer control system, the heliostats with mirrors, a tracking system and support pods, and a license to use several core patents.

The heliostats are set up nearby on freestanding space frames, or weighted pods, that require no digging yet can withstand high winds. The sun-tracking mirrors concentrate solar-thermal energy on a rotational mold. The heat from the sun directly warms the mold, melting the plastic with zero greenhouse gas emissions at zero fuel cost.

In terms of efficiency, solar rotational molding converts around 75 percent of available solar energy to useful heat, in contrast with the standard 20-25 percent efficiency of solar photovoltaics in converting energy to electricity.

This efficiency, combined with LightManufacturing's heat management, positioning and process control software, allows mirror arrays as small as 30 square meters (323 square feet) to generate sufficient heat to mold objects 1 by 1 meter in size. Put another way, 35 heliostats reflect enough heat to mold a 2,000-liter water tank.

The radiative heating directly heats the metal as opposed to convective heating and also warms the air around the metal. This means the process can achieve desired molding temperature at much lower surface/air temperature, which, in turn, allows the system to place electronics inside the molding chamber.

"The difference with us is that, because we're radiatively heating the mold, we can build a lot of advanced technology right in the molding chamber because it's not being exposed to 300° C (572° F) air but rather around 170° C (338° F)," von Kries said. "That means our systems can be highly automated and use sensors and computers inside the molding chamber, which is not possible with traditional rotational molding. That means we have a much more automated process than is typically possible: It can adapt to changing solar conditions and help the operator."

Automation technology frees operators during the long rotational molding heating cycles that can take around 30 minutes for products like water tanks. Sensors placed inside the molding chamber check internal and external temperature and feed that data onto a control system that monitors the heating process.

"Through programming, we can preferentially speed up and slow down the mold as it passes through the beam to build thicker walls or thinner walls," von Kries said. "You can make the top of the water tank thinner, where you don't need as much strength, and then as the bottom of the tank comes through the beam, you can slow it way down, heat it up more and build up a thicker bottom layer for strength. This gives us this very powerful control over wall thickness that you can't just do with the traditional machine."

If the sky turns cloudy for a period, then the system automatically extends the heating cycle until the mold is at the desired temperature.

"The operator doesn't sit there thinking, 'It's a little cloudy; let's extend this by two minutes,'" von Kries said. "You sit back and drink a glass of water while the machine takes care of all of that."

Cooling is also automated. Once the first mold is at temperature, the system automatically stops the heating cycle and reroutes the heliostats to direct heat at the second mold, starting a second heating cycle. In the meanwhile, cooling fans are automatically turned on in the first mold. Once the whole process is finished, a buzzer alerts the operator to remove the finished products from the molds.

Overall, the system is quiet, von Kries added, likening the sound to an electric vehicle hum.

"The birds around the site are louder than the machinery of the site," he said. "This is also one of the easiest systems to maintain. You can make a quick swap of mirrors if one gets degraded or damaged. It's really easy to repair it in place."

The SRM4 can operate in any generally sunny area. LightManufacturing uses software that analyzes 15 years of solar data across the globe to determine what processors can expect on a monthly and yearly basis.

"We're not just crossing our fingers and hoping for productivity. We can predict quite accurately what people will be able to make," von Kries said. "The Southwest U.S. is fantastic, and much of Mexico is very good. Latin America has many great places for it, like Argentina, Chile and Brazil, and so does Australia, much of Asia, southern Italy, Spain and much of the African continent."

Von Kries has talked to some brands looking at SRM to eliminate what he calls "social pleading" for consumers to pay higher prices for products made sustainably.

"Our process delivers sustainability and lower cost by eliminating fuel costs and emissions and reducing capex, unlike many sustainable technologies that ask you to pay more to do the right thing," von Kries said.

He has also talked to skeptics. Von Kries said he responds from experience.

"I'm amused to hear folks claim that solar rotomolding doesn't work, when we've been doing this for over 10 years and have thousands of parts serving customers like Disney, the U.S. military, the NFL and so on. With the launch of the SRM4, we're ready to bring sustainable molding to the global market," he said.

LightManufacturing is currently focused on applying its technology to rotational molding, but von Kries said the company plans to eventually start covering vacuum forming and compression molding applications.

Concentrated solar could also be used as a pre-heating or partial heating input for injection or blow molding, von Kries added. Given that those manufacturing processes tend to operate 24/7, concentrated solar would only act as a heating "boost" during the day.

Sustainable Plastics Associate Editor Beatriz Santos contributed to this story.