BACKGROUND

Single-axis tracker are becoming for the form factor of choice for utility-scale solar power plants. These arrays consist of rotating rows of solar panels oriented along a North-South line that move from an East-facing to West-facing orientation each day to follow the sun's path through the Southern sky. Until recently, single-axis trackers were constructed on plumb-driven monopile foundations. These foundations consist of rows of so-called “H-piles” are driven into the ground at each desired foundation point. Tracker system hardware is (e.g., bearing assemblies, motors, dampers, etc.) is attached to the top end of each driven pile. One reason for H-pile dominance is simplicity of installation. The piles are one-piece structures that are beaten into the ground with a vibratory or percussive pile driver and provide a uniform interface for tracker makers to design around.

Although all single-axis trackers share common features, there are differences in the design from company to company. In most tracker systems, a bearing is attached to the top of each pile and the torque tube is inserted in the bearing to rotate about its own axis. A motor on each row, or a row-to-row mechanical linkage, is used to rotate the entire torque tube at once so that the attached solar panels remain on-sun throughout each day. Some trackers, however, such as the NX Horizon Series of single-axis trackers from NEXTracker Inc. of Freemont, Calif. employ a different design designated as “mechanically balanced”. In this type of tracker, the torque tube swings like a pendulum from a bearing pin at the cusp of a cardioid or upside-down U-shaped bearing housing assembly or BHA. The tracker's drive motor is offset from the axis of the torque tube to match the axis of the bearing pins and the torque tube swings through an arc rather than rotating about its own axis. The rotational axis of this tracker is the bearing pin rather the torque tube. The purported advantage of this geometry relative to conventional single-axis trackers where the torque tube rotates about its own axis is that there is no overturning moment, regardless of tilt angle. However, because the top of the bearing housing assembly protrudes up into the module plane, it is necessary to have leave a gap between modules at each foundation point to prevent mechanical interference between the BHA and the modules. As a result, this particular tracker, and others like it, have very little tolerance for position error in the X-direction, that is, the North-South line of the torque tube.

An example of such a mechanically balanced tracker system is shown inFIGS. 6B and 6B. System10includes bearing housing assembly or BHA20that sits on right angle brackets30. As seen inFIGS. 6A and 6B, bearing housing assembly (BHA)20provides a bearing21that supports bearing pin22. A pair of torque tube photovoltaic module brackets25are attached on either side of BHA20and receive bearing pin22and also support torque tube27. For ease of illustration, only the back bracket25is shown in6A. The upside-down U-shape of BHA20limits the extent of the arc torque tube27can swing through. Due to BHA20needing to accommodate the swing of the torque tube, the foundation must be wider than the width of conventional H-pile5. The width of these beams is dictated by the web dimension; six inches is common (e.g., W6×9, W6×12, etc.). As a result, NEXTracker uses a pair of right-angle brackets30attached to the outer face of each beam flange to extend the width of H-pile5and to provide an adjustable planar base for BHA20to sit on. Bolts, hucks or other fasteners23extend from BHA20into right angle brackets30to hold BHA20in place.

Another potential advantage of the NEXTracker system is that because the torque tube is not locked in a bearing but rather free to swing, foundations do not always have to be perpendicular to the torque tube. This may be beneficial when installing a tracker on terrain that is not flat. In such situations, NEXTracker's BHA and the hardware supporting it may be adjusted in pitch to take up any mismatch between the torque tube and non-perpendicular foundations. With H-pile foundations, both X-axis and pitch adjustment relative to the foundation are accommodated by simply sliding and or rotating NEXTracker's right-angle brackets relative to the pile.

The applicant of this disclosure has proposed an alternative to H-pile foundations that converts lateral loads primarily into axial forces of tension and compression, allowing single-axis trackers to be supported with relatively less steel. Known commercially as EARTH TRUSS, this foundation system consists of a pair of angled legs extending below and above ground and straddling an intended North-South row of the tracker. The above ground ends of each adjacent leg pair are joined with an adapter or so-called truss cap that has connecting portions received in the open end of each leg and a horizontal mounting platform to support the NEXTracker BHA. The various embodiments of this disclosure are directed to adapters used to join the truss legs and support a mechanically balanced tracker such as that shown inFIG. 6A, or other tracker system requiring a wider support platform than that provided by a standard W6×9 or W6×12 H-pile.

The standard truss cap used in the EARTH TRUSS system is a one-piece casting. When paired with a NEXTracker foundation, some X-axis adjustability may be provided by slots in the top surface of the truss cap, however, because EARTH TRUSS foundations are typically installed to be perpendicular to the torque tube, the one-piece design by itself does not permit pitch adjustment. In recognition of this problem, various embodiments of the invention provide a two-piece truss cap that enable X-axis alone or X-axis and pitch adjustment when supporting a single-axis tracker such as the NX Horizon tracker or other trackers with similar geometry.

