Many governments around the world use some variation of the ’20-20-20′ framework for setting renewable energy and efficiency targets. Such a framework, pioneered by the European Union, consists of rules to reduce emissions by 20%, energy consumption by 20% and increase renewable energy to 20% of total capacity, all by 2020.
Much too modest, says a team of analysts from Thompson Reuters' Intellectual Property (IP) and Sciences group in the U.K. Solar power is primed to become the Earth's dominant form of energy by 2025, bar none.
‘We don't have a crystal ball, obviously,’ says Bob Stembridge, a patent expert with Thompson Reuters' IP services business and a co-author of a new report on ascendant technologies. ‘But what we do have is access to some fantastic sources of information that allow us to identify emerging research fronts.’
In particular, Stembridge and his colleagues use the company's Web of Sciences database to map out promising areas of scientific research and cross reference those with its World Patents Index. Analyzing the number of times a published scientific paper has been cited by other papers can give researchers a good indicator of how promising a particular area of research is. The number of patents that have been issued for a given technology gives a good indication of a technology's commercial potential.
This nexus of research and commercialization gave the Thompson Reuters team the confidence to make what is inarguably an optimistic prediction that solar power will lead the world's generating sources in the next 11 years. However, Stembridge says such optimism is not borne by wide-eyed idealism, but by clear considerations of need and some serious number-crunching.
‘Worldwide power consumption is expected to double in the next three decades because of increasing world population and rising demand for energy in developing countries,’ Stembridge says. ‘The sun provides a fantastic source.’
The notion that the sun could serve as a useful source of energy for mankind is not exactly a new one. By some calculations, the local star delivers 120,000 terawatts of energy to the Earth's surface daily, which Stembridge estimates is 6,000 times the present rate of global energy consumption. Of course, the challenge is to harness that.
One of the most fertile areas of research is the work on organic photovoltaic cells. The most highly cited solar-related paper in the Thompson Reuters Web of Sciences database concerns heterojunction solar cells made from conjugated polymers and a fullerine derivative. In a nutshell, Stembridge says, the paper describes energy conversion efficiency as being a function of the band gap and the energy levels of the conjugated polymer.
‘That paper was from 2006, but quite clearly it is foundational and fundamental to the development of organic photovoltaic cells,’ he says.
When the Thompson Reuters team wrote their predictions, the paper had been cited over 1,600 times. As of early August, the paper has been cited over 1,900 times, so it continues to be very influential.
As always with emerging scientific trends, there is a lag between fundamental research and the application that comes through in patents. Stembridge says the commercialization indicators for organic PV technologies are not yet evident in the form of patents. One of the other drivers for looking at organic PV cells, he says, is they are probably cheaper and easier to produce.
Organic materials are abundant. That's the good news. The bad news is that organic PV cells have conversion efficiencies of below 10%. However, Stembridge says the drive to achieve higher conversion efficiencies is reflected in the research as well. The Thompson Reuters databases reveal a lot of work devoted to employing dye sensitizers to help improve that efficiency.
‘There is every reason to suppose that work will continue and be successful,’ Stembridge says. ‘Therefore, this gives us a practical alternative to the current technology.’
That's not to say that existing inorganic solar cells aren't being worked on as well. Another paper highlighted in the report describes the formation of a novel heterostructure of titanium-oxide nanorods modified with cobalt-oxide. That paper, emerging from research at Chongqing University in China, is the most highly cited paper in the solar field written in the last two years.
Stembridge says this research also focuses on the efficiency problem. By modifying the titanium-oxide with that cobalt-oxide material, it enhances the visible light photochemical response compared to just plain titanium-oxide rods.
‘That would seem to offer good possibilities for applications in solar cells and photocatylists,’ Stembridge says.
Of course, no discussion of the future place of solar power in the world can be complete without some accommodation for storing this power. The Thompson Reuters team found what they describe as a ‘wow moment’ in research into photochemical storage, originating at Chalmers University of Technology in Sweden and University of California, Berkley.
The Chalmers-Berkley researchers found that if they irradiate a fulvalene diruthenium synthetic molecule with solar energy, the molecule rearranges itself into a transition state and then moves into a high energy state, which is stable. The material can be stored and transported. The energy can then be released as heat by reversing it back to its low-level state.
In May, the U.S. Department of Energy awarded $10 million through its SunShot Initiative to six research teams in order to develop a new generation of chemical storage technologies that could be incorporated into concentrating solar power stations.
Still, 11 years to a solar-powered world? Laura Gaze, a spokesperson for Thompson Reuters IP services business, stands behind the prediction, but says the real story is the methodology used to make it.
‘The essence of why we worked on the project was to show the kind of insight you can get from studying research and analyzing scientific patent information,’ Gaze says. ‘We want to show what you can extract from scientific and patent information and how valuable those insights can be.’