Page 15 - North American Clean Energy September/October 2019 Issue

This superior mesh contact translates to higher torque capacity and greater shock load resistance. Double- enveloping gear sets can optionally
be spring loaded to be self-adjusting, which helps to compensate for wear and maintain zero backlash integrity (where there is no clearance or lost motion caused by gaps between the teeth and the thread). This is crucial for accurate positioning. As a result, the double- enveloping worm gear set has become
a preferred solution for maintaining the ultraprecision required for efficient CSP operations. Across the globe, double- enveloping worm gearing technology can be found in virtually all manner of modern heliostat designs.
There is no such thing as a simple CSP installation; power producers must lean on trusted suppliers to overcome major obstacles. The
right technology for the job is one requirement, while the ability to coordinate large-scale deployments across continents is another critical consideration for keeping CSP projects on schedule. Take time to identify suppliers with a proven track record for completing large projects on schedule. After all, the sooner power generation starts,
the better. Working with a partner that offers extensive CSP market expertise and a collaborative engineering approach can be invaluable to achieving the best results.
Jacob Randall is Director of Strategic Markets at Cone Drive, a leader in precision motion control technology for diverse markets including solar, automation, aerial platforms, and food and beverage. In the
renewables market Cone Drive produces gear sets for trackers that position solar panels.
Cone Drive /// conedrive.com
Added Structural Stability
The high gear-to-worm contact ratio of double-enveloping worm gear sets also helps to provide stability for heliostats, which are frequently subject to extreme environmental forces. Because heliostats often measure 25 square meters or greater in size, they can act as large sails when strong winds kick up across wide open expanses. Desert windstorms can pack peak gusts up to 190 miles per
hour - heliostats must possess excellent structural rigidity to continuously withstand these forces, while holding their position to within fractions of an inch. They must also effectively resist any sand or debris carried along by these potentially damaging winds.
This requires high torsional stiffness, which is an inherent feature of double- enveloping worm gear sets, and mission critical to keep heliostats exceptionally stable. And while gear set designs with less inherent contact between the thread and the teeth can sometimes be sized up to withstand higher loads and stresses, this is not ideal for several reasons.
More weight means more material costs, as well as extra transportation and installation expense, and may also require design modifications to heliostats (to accommodate the larger gear set and added weight).
Additional Considerations
Regardless of the gear set design, it is important for CSP operators to ensure that heliostat gearboxes are properly sealed. Depending on the location
of the facility, moisture or salt spray infiltration can pose a threat to reliable heliostat operation. This is in addition to sand, dirt, and debris. Heliostat gearboxes should be designed for zero maintenance - lubricated internally, and sealed up for the life of the device. Some gearboxes must be greased every three to five years, which can quickly amount to a major maintenance headache when it comes to regularly relubricating tens of thousands of units operating in harsh conditions.
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Learn more about our solar services at www.dnvgl.com/solar.
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North American Clean Energy
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