3D Printing Expands Possibilities for Renewable Energy

Earth's natural resources aren't limitless, and the search for alternatives is ratcheting up. Fossil fuels such as coal, natural gas, propane, and other carbon-based solutions come with considerable baggage, including volatility in both price and availability. Historically, so-called black swan events, including the invasion of Ukraine—have caused massive price swings in the products that industries and consumers rely on. Additionally, there are the omnipresent issues of greenhouse gases and other pollutants tied to burning fossil fuels.

Both businesses and consumers are increasingly looking for home-grown solutions that provide stability in pricing and availability. For larger companies—especially utilities—geothermal could be one of those answers. Dubbed "the sun beneath our feet," geothermal systems tap into the extreme heat of the earth to turn turbines and create clean, reliable electricity. Although you need to go deep—really deep—to get to the layers that provide enough heat to turn turbines, the benefits are clear: Geothermal sources are consistent and aren't affected by political and economic turmoil.

Realizing this, the Department of Energy (DoE) launched the American-Made Geothermal Manufacturing Prize in 2020, which offers more than $4.6 million to spike research into this renewable resource, with a focus on additive manufacturing (AM), or 3D printing, to move the field forward. In 2022, Houston-based Downhole Emerging Technologies (DET) took home one of two $500,000 grand prizes for the development of a new form of packer system—a critical element that regulates the flow of heat and steam in geothermal wells. The achievement wouldn't have been possible without AM.

One thing to remember is that Earth is anything but hospitable at these depths. Between extreme temperatures as high as 700° F (371° C)—enough to melt some metals—and highly corrosive surroundings, you need to find the right materials and part geometries to withstand such abuse. This necessitates modeling, testing, and iterating to determine the efficacy of each part.

DET's founders Ken Havlinek and Tingji "TJ" Tang worked for years in the oil and gas industry. Because wells in these applications are shallower, their packers typically are made of rubber or plastic—materials that would melt in the heat of deep Earth. For this competition, the partners ported their knowledge to the realm of geothermal energy and designed an elegant solution, and a new challenge for 3D printing.

In the past, some of these parts might have been manufactured using CNC machining or injection molding. While both make outstanding parts, the process of tweaking designs to achieve desired outcomes is more complex. With molding, you need to make a new tool (mold) for each iteration, which is time consuming and expensive.

After careful evaluation, DET thought it might be possible to print some of their parts, including the packer. Printing also made sense because time was tight. Deadlines were imminent and 3D printing offered the opportunity to quickly iterate and improve part designs. As a veteran of the oil and gas industry, Havlinek admitted that AM initially hadn't entered his mind to make the packer and some of the other parts, but the DOT award helped him see his ideas in a new way.

"Like myself, the experts that are working on these geothermal challenges don't necessarily appreciate or understand the value that additive manufacturing can bring," Havlinek acknowledged. Thanks to rapid design-for-manufacturing advice from Protolabs, DET could experiment with multiple materials, adjust geometries, and see results within days.

It was a given that the parts had to be made of metal. Nothing else would survive in the superheated, corrosive underground environment. That meant using direct metal laser sintering (DMLS), a printing process that uses powdered metals as the base material to build a part layer by layer, welding tiny grains of metal powder together by a high-powered laser. Essentially, the laser draws the part in the powder bed until all layers have been formed and the part is completed.

One of the advantages of using DMLS is the parts can include complex geometries that would be impossible to make via more traditional manufacturing processes such as casting, forging, or machining. Also, the metals have hardness qualities nearly equal to a solid block of that metal. For these reasons, many companies are turning to DMLS to manufacture intricate parts.

DMLS also offers a wide range of metals, including aluminum (AlSi10Mg), cobalt chrome, Inconel 718, two kinds of stainless steel (17-4 PH and 316L), and titanium (Ti6Al-4V). Each has different strength and tolerance to corrosives and heat.

In fact, one of DET's parts required printing on a GE Additive X Line 2000R printer. Measuring a whopping 19" (482.6 mm) tall, with a width of 4.7" (119.4 mm), that sleeve turned out to be the tallest metal part ever printed at Protolabs.

Specialized features on one of the most important parts of the packer—a large ring shape—had to have the ability to deform efficiently and consistently, in a way that required less force to compress or stretch. This was vital to the packer's success. Creating a ring with these specifications via CNC machining would have created massive metal waste, which often translates into higher costs.

In this case, however, it was simply impossible to machine the part with the internal features that are critical to its performance, so the DET team refined the part for 3D printing. AM provided greater design freedom, so the team could be creative and push the features of the structure beyond what machining could achieve. Plus, waste was all but eliminated.

"Without those features, it would have taken a lot more energy to get the job done, and we wanted to use as little energy as possible to achieve the full range of motion required during the operation of the packer system," Havlinek added. "The smaller the amount of force required, the better. Thanks to additive manufacturing, we were able to reach our design targets."

Over the next few months, DET's packer system will undergo testing and refinement before it's ready to go to market. While DoE and rapid prototyping started this dream, the result will help open a more sustainable and safe future for energy production. This experience might also open the eyes of designers/engineers at other companies to consider 3D-printed parts for their projects.

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