Lord Corp.’s sales and technical support allowed Green Cycle Wind to reduce costs and improve performance and durability for their wind turbine.Alternative energy applications are a key focus and an emerging industry in today’s marketplace, creating new jobs and reducing the world’s dependence on fossil fuels. Harnessing energy from the sun and the wind to produce electricity is garnering interest from consumers looking for cheaper, environmentally friendly power sources.

Wind energy, used in windmills for mechanical power, wind pumps for pumping water, and wind turbines to make electricity, provide a renewable, clean power source that produces no greenhouse gas emissions. Capturing the sun’s rays through photovoltaic (PV) – converting light into electricity – also produces a clean, renewable energy source. To make these methods even more attractive to the end user, energy equipment manufacturers are seeking methods that will lower production costs while increasing product reliability.

One of the areas where manufacturers have been able to decrease costs and improve product dependability is in their choice of fastening systems. Although mechanical fasteners are commonly used for securing PV and wind turbine panels, structural adhesives are becoming more popular as an alternative. Structural adhesives offer the benefits of reduced stress points, leaks, and corrosion; resistance to extreme environmental conditions; and enhanced sealant properties.

Adhesive Benefits
According to Ian Quarmby, an Innovation Scientist at Lord Corp., a producer of general-purpose and specialty adhesives and coatings, structural adhesive bonding is an established joining method, proven in a variety of end-use markets, including cars, trucks, specialty vehicles, and boats.

“Lord Corporation’s adhesives have an established history of durability throughout the lifetime of an assembly,” Quarmby says. “Its automotive adhesives have been applied for over 25 years without any corrosion issues, and its metal-bonding adhesives are used in applications such as aluminum-skinned satellite dishes, commercial signage, and land-based military transport vehicles, where thermally induced stresses and wind loads create fatigue conditions.”

Structural acrylic adhesives offer high shear strength (from 1,000psi to 4,000psi) over a wide temperature range (-40°C to 170°C), allowing them to be as strong as welding and most other conventional fastening methods. Unlike screws, bolts, or rivets that concentrate the stress at the point of attachment, adhesives spread the stress over the entire bond area. Adhesives act as a sealant by keeping out moisture and can compensate for dimensional irregularities by filling in gaps on poor fitting parts.

Furthermore, structural adhesives offer a process-friendly solution that can save time and money, while increasing product quality.

“Depending on the assembly process or the speed of the assembly process, a manufacturer can apply adhesives from a manual cartridge or a sophisticated, high-speed robotic system,” Quarmby says. “Minimum surface preparation is required. There is no need to pre-drill holes or fill in over screw heads, and rework caused by burning from welding operations is eliminated.”

PV Panel Applications
PV devices consist of an array of cells containing various materials (such as an active silicon layer) that turn solar radiation into direct current electricity. To produce enough power for very large applications, cells are connected to form PV modules or solar panels. The active silicon layer is sandwiched between two glass panels. A metallic or composite frame encloses the panels and connects to a rack or framework structure that supports the panels. The racks are affixed to single- or dual-active tracking systems that allow the panels to follow the sun.

“There are many areas of solar panel construction where structural adhesives would be a viable alternative to mechanical fasteners including the assembly of PV panels and in the supporting framework structure,” Quarmby explains. “For the manufacturing of PV panel systems, structural adhesives can be applied between the glass and the metallic or composite frame, and are also used to attach the frame to the rack. The structural adhesives are a cost-efficient, durable alternative to mechanical fasteners such as U-bolts and screws.”

PV panel installers can also reap benefits from switching to structural adhesives in place of mechanical fasteners. In many systems, there are hundreds of bolts connecting the array to the racking and tracking systems. These bolts require continual maintenance to ensure the operating integrity of the solar panel system.

Reducing the complexity and duration of the maintenance checks not only reduces costs, but a portion of the savings can be passed along to the consumer. A typical commercial installation might have 100 to 400 solar panels, or more – at $1,200 to $1,300 per panel – with the final cost reaching upwards of a half-million dollars. Any cost savings to the consumer would make solar panel systems much more attractive as an energy option.

Other problems occur when the mechanical fasteners, used to secure the PV arrays to the supporting racks and tracking systems, loosen over time due to wind-induced and/or structural vibration. Structural adhesives not only eliminate the problem of loosening fasteners, but also eliminate the need to visit an installation site for maintenance follow-ups. Structural adhesives also eliminate the weight of mechanical fasteners and improve stress distribution, while providing a clean, streamlined appearance.

“Another potential benefit to PV installers and manufacturers is a reduction in inventory,” Quarmby comments. “Their huge inventory of bolts, washers, and screws can be replaced with one structural adhesive kit.”

Wind Turbine Application
Structural adhesives are also finding acceptance in the manufacture of wind turbine equipment. Wind turbines, made by Green Cycle Wind LLC, Schaumburg, IL, feature dual-source technology to generate electricity – natural wind and wind energy – from mechanical/HVAC-equipment-produced exhaust air. When the company changed the material of construction for its alternative energy product, they also needed an alternative fastening method.

“When we switched from using galvanized steel panels, which were too heavy and not strong enough for certain installations, to lightweight composite aluminum panels, which were more durable and more adaptable to different applications, we also had to revise our turbine design and manufacturing procedures,” says Vince Blake, founder of Green Cycle Wind. “The metal fasteners, used on the galvanized steel panels, were too heavy for the lightweight aluminum composite panels and were also prone to rusting and loosening.”

In searching for an alternative fastening method, Green Cycle Wind found that structural acrylic adhesives offered a solution that reduced weight, while also providing benefits in reduced assembly time and corrosion protection.
“Our next-generation Maxlok acrylic adhesives were able to meet Green Cycle Wind’s challenging requirements including bonding dissimilar materials, improving durability and fatigue life, reducing weight, and enhancing product aesthetics while lowering manufacturing costs,” comments John Higgins, account manager at Lord Corp. 

“Reducing assembly costs and improving fatigue life were definitely the key drivers in the successful collaboration with Green Cycle Wind’s turbine design,” says Bob Zweng, global product integrator for Lord Corp. “With Lord Corporation’s strong adhesive implementation know-how, we were able to offer immediate input, sharing best practices with novel application processes and proven joint fabrication techniques.”

Carlos Cruz, market manager, product assembly adhesives and coatings, Americas Region, Lord Corp., adds that, “with the introduction of Maxlok acrylic adhesives, which can be used for green energy technologies, Lord Corporation is able to offer an easy-to-use adhesive alternative to OEM and component manufacturers in these markets.

“In addition, Lord Corporation is able to provide fixturing, joint design, and dispensing equipment solutions for these types of applications,” he states.

Better Bonding
As less costly, environmentally-friendly energy sources become more popular, manufacturers will be looking for less expensive, more viable product construction methods. Using structural adhesives in place of mechanical fasteners will enable manufacturers to build a better product, faster, simpler, and with less cost.

“There is a big push for corporations to Go Green,” Quarmby notes. “Companies are adopting sustainability themes and their shareholders, employees, and local communities are all interested in environmentally-friendly practices. Structural adhesives offer the potential for cost-savings, along with the reassurance of product durability and environmental stability.”

Lord Corp.
Cary, NC
lord.com