Harnessing solar energy using photovoltaics
Sunlight is a resource which, alone, could provide many times more energy than required to sustain human activity at its current level. Its importance as an energy resource has been appreciated for many years, but no more so than now, as a global energy crisis takes hold and our reliance on fossil fuels has become exposed in the wake of the war in Ukraine.
The International Energy Agency has predicted the sun could be the largest source of electricity by 2050, with solar photovoltaic (PV) systems generating up to 16% of the world’s electricity. Investment strategists at RBC Wealth Management have called solar power “the fastest-growing form of renewable energy”.
By the end of 2018, global cumulative installed photovoltaics capacity reached about 512GW. Solar power supplied about 3% of global electricity demand in 2019.
Furthermore, in the U.K. – despite the ongoing Covid-19 pandemic – 2021 was one of the most significant years for solar PV. According to Solar Energy U.K., the U.K. added 730MW of new solar capacity during the year –. an increase of 36% on 2020, when 538MW was installed.
Photovoltaics (PV) is the conversion of light into electricity using semiconducting materials that exhibit the photoelectric effect. Here, we analyse the patent climate in the field of PV and provide insights into the trends and direction of innovation.
Appleyard Lees’ analysis
Our analysis shines a light on the current state-of-play in solar energy, including:
- Global patent activity
- Key players
- The materials and technologies enabling large scale deployment of PV
The PV circuit includes one or more solar cells (generally arranged in “modules”) and a Balance-of-System (BOS). A solar cell contains a semiconducting material used to convert sunlight into electricity. The BOS refers to all components of the PV circuit other than the cells or modules themselves, such as mounting structures, inverters, and batteries for electricity storage.
In this part of our report, we analyse the direction of innovation of semiconducting materials and the BOS, as well as the emerging technologies set to improve commercially available PV. Through these technologies, it is possible to obtain higher conversion efficiencies, improve integration into the grid, and solve anticipated problems associated with accessing the necessary raw materials. Therefore, we have investigated:
- Emerging semiconductor materials and architectures, such as perovskites and multi-junction solar cells
- The use of artificial intelligence (AI) to manage distributed energy resources
Global patent activity – visible effects of the “solar shakeout”
In the past few decades, the PV industry rapidly scaled up mass manufacturing of solar cells. Around 2012, there was a market consolidation, or “shakeout”, where many companies could not operate in a cut-throat price environment. Also, state subsidies for PV diminished.
Figure 1 shows global filing for patents in PV materials and their manufacture. The number of annual patent filings has been decreasing since a peak in 2010 and annual filings in the past five years are at their lowest number since the 1970s.
Figure 1: Twenty year trend: global priority filings – PV materials & their manufacture
Figure 2 shows global filing activity for patents relating to the BOS. In contrast to Figure 1, the number of annual patent filings has been increasing in recent years.
Figure 2: Twenty year trend: global priority filings – BOS
Figure 2 shows global filing activity for patents relating to the BOS. In contrast to Figure 1, the number of annual patent filings has been increasing in recent years.
Whilst innovation in the BOS was probably affected by the solar shakeout (see the temporary decrease in filing numbers in 2012), it has been more resilient, likely due to the BOS being less monopolised by a small number of manufacturing giants. This enabled competitive innovation whilst still obtaining a good return for R&D investment.
Figure 3 shows comparative trends in patent filings in solar cells and the BOS. Notably, there has been a recent upsurge in patent filings grouped in codes relating to frame structures (H02S30/10), moveable supporting structures (H02S20/30) and solar tracking (H02S30/32). In contrast, patent filings grouped in codes relating to solar cell devices (H01L31/04) and their manufacture (H01L31/18) have declined in the same period.
Figure 3: Filing activity 2016-2020: global patent filings - specific technology groups
Therefore, we can conclude that innovation in solar cells has stagnated whilst innovation in the BOS is advancing.
Key players – movement in the market
Patent filings for solar cells and their manufacture have dwindled, probably because of a few dominant companies between the late 2000s and early 2010s.
Figure 4 supports this view and shows that in 2012 the top three filers (Sharp, Mitsubishi and LG Chemical) were each filing more patent applications than the fifth to tenth highest applicants combined.
Figure 4: Filing activity 2008-2020: top ten patent applicants for solar cell & solar cell manufacture technology
However, looking at innovation in the BOS, Figure 5 shows that the number of patent applications filed by each of the top 10 applicants in recent years is uniform, indicating a competitive space. Sunpower Corp. is the top filer, despite being the 18th top filer in the solar cell field. Other relatively smaller companies, including German inverter manufacturer SMA Solar Technology (fourth) and the French Alternative Energies and Atomic Energy Commission (sixth), also feature.
Figure 5: Filing activity 2008-2020: top ten patent applicants for BOS
Silicon
Silicon continues to be the semiconductor-of-choice for solar cells and dominates growth in real-world deployment of PV.
Figure 6 shows filing numbers for silicon solar cells, which peaked in 2010 followed by a drop-off to numbers only twice those of the early 2000s. This may be due to difficulties in competing with the large silicon cell manufacturers such as those identified in Figure 4 above.
Figure 6: Twenty year trend: global priority filings – silicon solar cells
It is unlikely that silicon solar cells will be replaced by new technology any time soon. However, there is a need for efficiency improvements not possible using silicon alone. This is one of the motivating factors for research into alternative materials and more complex cell architecture, as discussed below.
Perovskite
Perovskite is a material structure developed over one hundred years ago, but first used in energy conversion in 2009. Perovskite cells can be more efficient than silicon cells at lower light intensities. Furthermore, thin-layer architectures and a high degree of transparency are also possible with perovskites, lending them to a variety of novel applications. Additionally, the materials required to manufacture perovskite solar cells are cheap and abundant.
Figure 7 shows an increase in patent filings for perovskite solar cells since 2013. Filing numbers have remained stable since their 2017 peak, with about 150 new priority filings per year.
Figure 7: Filing trend 2009-2020: global priority filings – perovskite solar cells
Other advances in solar cell technology
The recent, record efficiencies for converting light into electricity were all obtained using multijunction (or “tandem”) solar cells. Each junction is designed to optimally produce electric current in response to a specific band of light wavelengths. So, providing multiple junctions which each respond to a different wavelength band makes greater use of the solar spectrum for converting into electricity.
Patent filings for multijunction cells peaked in 2009 but, over the past five years, annual filing numbers were between 60 and 80 new priority patent applications. However, high costs are a barrier to large scale deployment of multijunction solar cells.
The recent top patent filer is Azur Space Solar Power. While costs in space PV are already high, the multijunction solar cell’s improved resistance to cosmic radiation is invaluable.
Our analysis also showed that patent filing numbers in quantum dots for use in multijunction solar cells and organic solar cells have been stable in recent years.
AI and solar
Artificial intelligence (AI) is being applied across a vast range of industries and photovoltaics is no exception. AI can analyse large volumes of historical and real-time data from satellites, weather stations, and IoT devices to recognise patterns and predict weather that could impact energy generation.
Figure 8 shows that patent filing numbers for AI photovoltaic inventions jumped between 2018 and 2019 and continued to grow in 2020.
Figure 8 - Filing trend 2013-2020: global priority filings – AI photovoltaics
The French Alternative Energies and Atomic Energy Commission obtained granted European patent EP2211300B1 which relates to “forecasting electricity production of photovoltaic means”. This is a good example of how AI is being applied to photovoltaics and illustrates that patents can be obtained for such uses.
Tom Gregory European Patent Attorney
Paul Beynon Senior Associate