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Solar Trackers. Analysis of Inventions

One of the options to substantially increase the efficiency of solar technologies is the implementation of trackers, devices that follow the solar position and correspondingly orient photovoltaic panels or mirror reflectors. There is a multi-level classification of trackers based on their functional capabilities. First of all, passive and active trackers can be distinguished. In the latter case special actuating mechanisms such as electric motors or hydraulic devices are used for mechanical movement of solar elements. Another important classification feature of trackers is the number of axes around which the adjustment can be performed. Here, main options are Single Axis Tracking and Dual Axis Tracking. In detailed sources more specific tracker features are additionally mentioned, for instance, Horizontal Single Axis Trackers or Azimuth-Altitude Dual Axis Trackers.

Employment of solar trackers is an indispensable condition for concentrating solar energy technologies. In this case it is the precise adjustment of parabolic or flat heliostats and concentrated energy receivers towards the sun that ensures the performance of solar power stations of this type in principle. In the last years the employment of solar trackers is being extended in photovoltaic applications as well. According to a number of economic and technological studies, employment of Single Axis Trackers allows the efficiency of solar energy conversion to be increased up to 25% and even to 35%, while for Dual Axis Tracking – up to 40%. In addition, for solar tracker market a yearly average growth of 13-16% is forecasted in the nearest future.

Currently, there are several large manufacturers of solar trackers on the market, having many years of positive operational experience and whose supply rates of various tracking devices amount to hundreds or even thousands. Among them the following should be highlighted: AllEarth Renewables, Array Technologies, Inc., First Solar, Inc., and DEGERenergie GmbH.

PV solar panel with tracker unit

However, use of solar trackers in photovoltaic applications is controversial. Main deterrents here are their high costs and additional maintenance expenses. Solar tracking systems and, particularly, actuating mechanisms are complex and vulnerable structures that require regular maintenance by trained personnel. Often, implementation of trackers can double the cost of solar power plant, thus neutralizing the additional benefits of increased solar generation efficiency. Therefore, presently the use of trackers in the solar power industry is limited, excluding, as mentioned above, concentrating solar power facilities.

Overcoming this barrier in the majority of cases comes down to raising the organizational level of solar power plant management and engineering improvement of solar tracker design. A significant part of effective technical solutions aimed at the development of these technologies is concentrated in patent documents registered with various patent offices. EnerTechUp company performed a systematic search of patent documents on this subject, prepared a unique patent database, and conducted a thorough statistical analysis of the patenting activity results. The database includes about 8 thousand patent documents published in generally-accessible sources all over the world during 1994 and 2021. Statistical analysis of patent documents was performed for a twenty-year period between 2002 and 2021. Results of the statistical analysis are generalized and provided in the patent review.

In total, 7756 patent documents (2453 patents and 5303 patent applications) were found for the present review. The most active registration of patent applications took place in 2010-2019. 173 patent families had three patent documents and 102 families had four documents. 6 patent families comprised more than 20 patent documents. The most popular patent offices with applicants were CNIPA (China), USPTO (US), and KIPO (KR).

Breakdown of inventions by patent offices. Patents, 2002-2021 (left); Applications, 2017-2021 (right)

Representatives of 46 countries around the world participated in the patenting process. The largest number of patents were granted to the residents of China, South Korea, and the United States. The residents of China (41.8%) and the United States (22.3%) filed the largest number of patent applications in the last five years. The largest number of patents were issued to non-residents by CNIPA (China), USPTO (US), KIPO (KR), KPO (JP), and EPO.

In 2002-2021 patents related to Solar Trackers were granted to 1575 applicants from 33 countries. Among them, the residents of China were granted more than 32% of patents, South Korea – about 20%, The USA – 18.3%. The largest number of applicants who were granted patents in 2002-2021 were the residents of China (548), South Korea (467), the USA (239), Spain (96), Japan (64). In 2017-2021 patent applications were registered by 928 applicants from 34 countries. The residents of China account for 42.6% of applications, the USA – 22.7%, South Korea – 6.3%.

Countries participating in patenting process. Number of patents obtained by resident applicants in 2002-2021

Between 2017-2021 the largest number of applicants who filed applications of inventions were the residents of China (542), South Korea (103), and the USA (103). The top 10 applicants account for 11% of patents and 18% of applications. The share of the top 10 applicants in the intellectual property register (market involvement ratio) comprised 10.5% (for patents) and 17.6% (for applications).

The leaders by the number of patents granted in the 20-year period were American companies SunPower Corporation and NEXTracker Inc – 73 and 46 patents, respectively. Also, NEXTracker Inc. registered the largest number of new patent applications during 2017-2021 – 102. However, taking into account a large number of participants of the patenting process, the shares of the leaders in intellectual property registry remained small – about 3% for SunPower Corporation and about 2% for NEXTracker Inc.

Top 10 applicants by intellectual property market involvement. Patents, 2002-2021

Volume ratio - share of applicant documents in total number of documents.
Ownership ratio - applicant's participation share in total number of documents.
Market involvement ratio - volume ratio multiplied by ownership ratio.

A detailed statistical and technological analysis of patent documents related to solar trackers was conducted for individual patent groups containing documents with similar technological attributes. The groups were selected on a trade-off basis, taking into consideration the technological importance of a subject, its popularity with inventors, the possibility of unambiguous interpretation of technological attributes of a group, and reasonable number of the groups.

List of individual patent groups includes:

Tracker support structures
Tracking mechanisms
Tracking systems
Maintenance and mounting of trackers
Single-axis trackers
Dual-axis trackers
Floating solar trackers
Flat-panel trackers
Concentrating collector trackers

From the list of ten elaborated technology elements, Tracking systems, Flat-panel trackers, Tracker support structures, Dual-axis trackers, and Tracking mechanisms were mentioned in patent documents more than others. Each of them was encountered in at least four out of ten patent documents. Technology elements Concentrating collector trackers, Single-axis trackers, and Sensors were considered in approximately every fifth patent or patent application. Technical solutions related to Maintenance and mounting of trackers and Floating solar trackers were mentioned less often than others.

Major manufacturing operations and equipment. Breakdown of documents by mentioned technology elements. Patents, 2002-2021 (left); Applications, 2017-2021 (right)

Tcc - Concentrating collector trackers; Tda - Dual-axis trackers; Tfl - Floating solar trackers; Tfp - Flat-panel trackers; Tmm - Maintenance and mounting of trackers; Tms - Tracking mechanisms; Tsa - Single-axis trackers; Tsp - Tracker support structures; Tsr – Sensors; Tss - Tracking systems; Tu - Trackers - other and unclear

After comparing the percentage of mentions of each of the elaborated technology elements mentioned above for patents and patent applications published in the last five years, it was established that the share of mentions of Flat-panel trackers has grown more than others, by almost 25%. The registered growth of interest towards Single-axis trackers, Tracker support structures, and Maintenance and mounting of trackers was at a far lower level; noticeable decrease can be seen in the shares of mentions of such technology elements as Concentrating collector trackers, Dual-axis trackers, Tracking mechanisms, and Sensors.

PV solar panel, tracker and gear rack

In the years to come a growth should be expected in the number of granted patents related to Flat-panel trackers. This technology element demonstrates a sufficiently high A/P coefficient value (Relationship of number of applications to total number of patent documents by year), and about 60% of patent applications published over the last few years pertain to the start ones i.e., not related to any existing patent family. For Flat-panel trackers the top 10 applicants include the representatives of the United States, China, Spain, France, and Taiwan. The largest number of patents between 2002-2021 were granted to SunPower Corporation.

Flat-panel trackers. Examples of technical solutions:

Torque limiter devices, systems and methods and solar trackers incorporating torque limiters / P: US10042030B2 / IPC: F24S30/00, F24S30/425, F24S40/00, G01S3/786 / Corio Ronald P / Corio Ronald P, Array Tech Inc / Appl. date: 21/02/2017; Publ. date: 07/08/2018 / United States Patent and Trademark Office / Technology elements: TR, Tda, Tfp, Tms, Tsa, Tsp / Claims: 27 / Rating: 17
The invention discloses torque-limiting assembly and method for tracking solar panels. The torque-limiting device is connected to and depends on the drive system (a torque limiting clutch in case of a one-way gearbox; a linear slip device in a push/pull linked tracker; a pressure relief valve in a hydraulic system). According to the claims, in the torque-limiting assembly of the invention “…when a hinge moment force causes a level of torque on the drive system to exceed a pre-set limit the torque limiter passively allows rotational movement of the tracker row in the direction of the torque, thereby allowing the hinge moment force to rotate the tracker row about a pivot axis such that hinge moment is reduced or eliminated as a result of a new rotational position of the tracker row independently of a plurality of tracker rows”. According to the authors, the invention aims to minimize dynamic forces the tracker is exposed to, at the same time allowing for a lighter and cheaper tracker structure.


                      Image from: US10042030B2                                                                                   Image from US10848097B1

Solar tracker system / P: US10848097B1 / IPC: H02S20/32, H01L31/0475, H02S30/00 / Needham Christopher Thomas, Oudheusden Frank Carl / Fcx Solar Llc / Appl. date: 12/08/2020; Publ. date: 24/11/2020 / United States Patent and Trademark Office / Technology elements: TR, Tfp, Tss / Invention types: D / Claims: 20 / Rating: 15

A damping system for a solar tracker is described in the invention. The described damper provides two damping ratios, depending on the loading conditions on the tracker. A chamber, a movable piston inside the chamber, the piston having two ports with the first and second diameters, with the second diameter being larger than the first one; and a valve to open the second port at a first damping rate conditions or close it at the second damping rate conditions. The tracker system is controlled by an actuator and a controller, but the damper transitions from one ratio to the second ratio are independent of the controller. With reference to the prior-art systems, the authors of the invention outline risks of displacement of trackers in heavy weather conditions and increased costs of preventing this issue.

A complete version of the database and patent review can be found at