Solar Thermal Concentrating Power Plants

Solar thermal plants utilize the heat from the sun's rays. The sun’s rays are concentrated via reflectors in an absorber to heat a fluid that generates water vapor using a heat exchanger. The water vapor is used to drive turbines and generators as in conventional thermal power plants. Solar thermal power plants include parabolic trough, Fresnel and solar tower power plants. Dish Stirling power plants are a special variant where concentrated sunlight directly drives a Stirling engine that in turn drives a generator.

In systems where the sun's rays are concentrated from heliostats on absorbers in solar towers, the tracking systems of the mirrors must be moved with high precision and high accuracy. The bearing supports must operate using the lowest possible friction and high rigidity.

Improved Performance in Tracking Systems with High-Precision Bearing Supports

Rolling and plain bearings such as maintenance-free half shells with a metal-polymer composite sliding layer are used in tracking systems. In parabolic trough structures that can measure almost 200 meters in length, they minimize the torsion of the long axis that compromises the reflection of the sun's rays on the absorber pipes.

Schaeffler supplies rigid angular contact roller bearings with high load carrying capacity for two-axis gearboxes for heliostats that measure 120 m², for example. These components enable the high loads generated by the weight of the mirrors and wind forces to be reliably supported. This means the power plant precisely tracks the sun's path.

With its AXS axial angular contact roller bearings, Schaeffler has developed a bearing series with a particularly small cross-section that is capable of supporting very high loads.

Typical applications are reflector adjustment systems. These rolling bearing supports facilitate the movement of the azimuth and elevation axis in double-axis drive units.

Axial angular contact roller bearings AXS comprise thin-walled drawn bearing rings and injection-molded plastic cages with cylindrical rollers. They can support axial forces as well as radial forces and tilting moments. When fitted in pairs, they can transfer very high loads safely. Axial angular contact roller bearings are suitable for O and X arrangement.

INA slewing rings are used in solar power plants for the precise alignment of particularly large reflectors and collectors, for example in double-axis tracking systems with two separate drives. In the case of separate drives, slewing rings are used in the bearing supports of azimuth axes.

INA slewing rings are known worldwide as premium products in the field of rolling bearing technology. A single bearing can reliably support radial, axial and tilting moment loads. It is therefore possible in many cases to replace bearing supports comprising a combination of radial and axial bearings by a single bearing, despite the high loads involved. This reduces, in some cases considerably, the costs and work required in the design of the adjacent construction and the fitting of bearings.

Slewing rings are sealed on both sides and lubricated with high-quality lubricating grease. They can be lubricated via lubrication nipples. The bearing rings are supplied without gear teeth or, in order to achieve simple drive solutions, are available with external or internal gear teeth. Customer-specific special solutions are also possible. INA slewing rings are available as single or double row four-point bearings as well as crossed roller bearings.

Depending on the power plant involved, radial insert ball bearings and housing units of cast iron, sheet steel and plastic are used to support the elevation axis in single-axis tracking systems. These bearings are available in various designs with anti-corrosion protection, for example with Corrotect® coating. INA radial insert ball bearings and housing units are filled with lithium soap grease that is especially resistant to corrosion and aging. They are also available with square and hexagonal bores. To make the mounting process easier, split housings are also available that can also be used with various plain bearing types.

INA track rollers are used on the rail systems for adjusting the azimuth axis of solar modules or for swiveling the parabolic mirrors. They are used in photovoltaic, Stirling and solar tower power plants. The rollers are designed as needle roller bearings, ball bearings or plain bearings. These bearings can also support high radial forces and axial forces in both directions. Our INA track roller range comprises more than 3,000 basic designs for all current applications.