# A Machine Learning Approach for Solar Power Technology Review and Patent Evolution Analysis
## 4 Solar Technology Patent Review and Analysis
### Statistical Analysis of Patent Metadata  
Statistical information provides experts with a preliminary understanding of emerging patent trends. In this research, there were a total of 2280 patents found that matched the search domain and included 2054 DWPI (Derwent World Patents Index) families. Based on this search result, statistical analysis and text mining were applied. The objective was to analyze the leading assignees, IPCs, countries and patent publishing trends. From these results, it is possible to illustrate and describe global industrial development of solar power. China owns the most patents in this domain, which accounts for over 90% of overall patents. The US owns the second most patents, but only accounts for 4.3%. China is the world's largest market for solar photovoltaics and solar thermal energy and is the second largest country in energy consumption. Greater energy demand may be driving the Chinese government's efforts to revise their energy policies to support sustainable energy development [61]. The patent publishing trend shows that the number of patents published have continued to increase over the last 10 years with China the largest contributor of solar power technology. China is the world's leading solar PV installer, and the solar photovoltaic industry in China is a growing industry with more than 400 companies. During the period of the 11 th Five-Year Plan (FYP) from 2006 to 2010, China's PV industry developed rapidly and became one of the few industries that could compete globally. China has been the largest PV manufacturing nation since 2008 when it became the largest producer of solar panels in the world. During 2011 and 2012, in China government implemented a series of incentives, including direct subsidies for solar PV installations and a national feed-in tariff scheme [62]. China's domestic PV market has seen steady growth with increasing cumulative installed capacity. However, China's PV products rely heavily on foreign markets. The orders from the European and American markets have declined due to the economic crisis and tariff protection around 2008, which decreased the number of patents published. In 2012, the US Department of Commerce ruled on imposing anti-dumping duties on Chinese solar photovoltaic module products exported to the US [63]. Along with the PV subsidy policy cancellation in European countries, the reduced orders led to China's overcapacity and subsequent decline in R&D patenting in 2014 [64]. In November 2016, The Commonwealth Scientific and Industrial Research Organization [65] signed a technology patent transfer agreement with the Chinese solar company Thermal Focus. The concentrating solar thermal power generation technology (CSP) developed in Australia was transferred to China which may have influenced the patent publishing numbers as they dropped in China during 2017. The top seven assignees are all from China including four academic institutions (universities) and three energy-oriented technology companies. It means that China owns the largest share of IP technologies in terms of solar power supported by development and innovation from academia and industry. Wuxi Tongchun Energy Technology Corporation is the assignee that owns the most patents and much more than the top two assignees. The company is creating new energy products, epoxy boards, and other innovations such as sun loungers for the elderly in smoggy weather. The fifth largest assignee, State Grid Corporation, is an institution and state holding company that has been approved by the State Council of China to conduct state-authorized investment. The company constructs and operates the China Power Grid and supplies national electricity. The number seven assignee, Fuzhou Aquapower Electric Water Heater Corporation, is focusing on the development, manufacture and sale of solar water heaters. Wuxi Tongchun used to be the largest technology developer before 2015, however, Tianjin University and State Grid Corporation became the top assignees during the following three years.