The Power of New Wind Energy.

Wind is the movement of air from an area of high pressure to an area of low pressure. Wind exists because the sun unevenly heats the surface of the Earth. As hot air rises, cooler air moves in to fill the void. As long as the sun shines, the wind will blow.

Once called windmills, the technology used to harness the power of wind has advanced significantly over the past ten years. The golden area of the windmill has not faded into a shadowy relic of the past. It has ignored the barriers and is now implicated as a witness of authoritative, advancing technologies.

The environmental and economic logic of clean energy is growing steadily more obvious. Every forecast shows rapid growth in the world’s electricity demand, even as we near (or perhaps already passed) peak oil. Climate resilience is an organizing principle effect such that renewable energies are finding capitol faster than fossil fuels.

Most wind energy comes from turbines that can be as tall as a 20-story building and have 200-foot long blades. The wind spins the blades, which turn a shaft connected to a generator that produces electricity. Because air is viscous (like very thin honey) and “sticks” to the ground, the wind velocity at higher altitudes can be many times higher than at ground level.

Figure 1: Axial force windmill tower manufacturing load cells.

Wind energy is the kinetic energy of air in motion. Total wind energy flowing through a silhouetted windmill surface with area A during the time t is:

The above equations show wind power in an open-air stream is proportional to the third power of the wind speed, so the available power increases eightfold when the wind speed doubles.

A US company is building the next generation of towers for the future generation of wind power.

Their spiral-welded technology is a breakthrough in tower manufacturing, making possible to support larger next generation turbines. The cost can be lowered dramatically and enable turbines to reach higher into stronger winds for greater energy capacity.

Spiral welding of wind towers combines all the production steps for making large diameter steel shells into one process, greatly reducing the cost, footprint, and time required to produce a steel tower on site.

In the quest for harnessing the most advanced on site manufacturing methods Stress-tek was requested to design and manufacture customer force sensing load cells to integrate within this manufacturing process. The center of gravity in multi-vector load cell design lies in the science of stress analysis. Attention must be paid to the causes and methods of allowing certain force components to be measured and others rejected. The rational of the design is inseparably connected with the ability to evaluate the stresses for a 3-dimensional force vector.

The load cells are specifically designed to measure an axial force related to the hydraulic pressure pushing the steel sheets together. The total force is a 3D vector where only this axial vector component is desired to be measured for control and feedback of the welding machine. The other two component vectors must be ignored by the force sensor. Using creative design to control the measured stress patterns, Stress-tek separated the three stress components and aligned Micro Measurements strain gages in specific directions. The strain gages are located on the neutral axis of one force directional axis rendering it invisible, a moment canceling technique is used on another axis making it transparent, which then allows accurate capture of the desired axial force component.

Automation of advanced manufacturing using force sensing give the spiral tower welded design a strong cost advantage improving quality and consistency. These innovations enable on-site tower manufacturing to be deployed in less than a month allowing for larger towers to reach higher into stronger winds unlocking vast swaths of low cost, renewable energy.

Figure 2: Load cell calibration of the axial force load cell in the Stress-tek laboratory.

The on-site tapered spiral welding technology enhanced with load cell force sensing allows for construction of modern wind turbine towers that are far larger than can be shipped by road or rail. Sheet steel is shipped flat on standard highway trucks and is welded together during fabrication using force sensing to control pressures used to push the steel sheets together for welding. A single machine completes the joining, rolling, fit-up, welding and severing of a tower sections tapered diameters and variable wall thickness.

There is no more halfsies on climate change, the message is clear from pole to pole that science is telling us the basic rule of thumb for dealing with climate crisis is – to stop burning things. Within that realm, Stress-tek remains devoted to the analysis of stress and strain and the relating conditions of equilibrium within load cell system design while partnering with companies, adding punctuation to new discoveries, and showcasing innovations within industry.

Figure 3: Load cell calibration of the axial force load cell in the Stress-tek laboratory.

Figure 4: Load cell calibration of the axial force load cell in the Stress-tek laboratory.

ABOUT STRESS-TEK:

Stress-tek has extensive experience in the design and manufacturing of strain gage based sensors and load cells, applying strain gages to element bodies and providing stress analysis services. It has complete in-house capability in engineering, machining, assembly, and testing. 

Stress-tek was founded in 1978 to provide professional consulting services in the areas of strain gaging, transducer design, and experimental stress analysis. Since then they have evolved to designing and manufacturing of custom and high volume weighing, force measurement, pressure, and deflection sensors requiring accuracy and reliability. The result is an extensive line of shear beam load cells, bending beam load cells, shear pin load cells, tension and compression load cells, deflection transducers, hydraulic and air pressure sensors. Stress-Tek, also designs and manufactures digital, two-wire electronics to integrate with our load cells and sensors to provide complete solutions.

In 2015, Stress-tek became part of Vishay Precision Group, Inc. (VPG), an internationally recognized designer, manufacturer and marketer of sensor and sensor-based measurements systems specializing in the growing markets of stress, force, weight, pressure and measurement. VPG is a market leader of foil technology products, providing ongoing technology innovations in precision foil resistors and foil strain gages, which are the foundation of the company’s force sensors products and its weighing and control systems.