The renewable energy world may seem very modern and urgent but search long enough and you’ll find folk who have been in the game a very long time. Trina Solar international technical director Pierre Verlinden has been testing the limits of turning sunlight into electricity since the 1970s. In June he was awarded the William R. Cherry Award for his contribution to the industry and over recent years his team has achieved world-record results in cell and module efficiencies.

The Belgian-born Australian works mainly in China and his association with Australia today is mainly through Trina’s research work at UNSW and ANU.

What did you expect for solar when you started in the industry more than 35 years ago?

I started working on solar photovoltaic technologies in 1979. At that time, the motivation behind PV research was primarily the space programs and the economic, social and educational development of Third World countries. I expected an exponential explosion of the PV market … in the next five years. For the following 15 years the expectation remained. It finally did happen by the end of 1990s. I was dreaming the development of PV market would start in the Third World countries before our well-developed countries. I was wrong. The PV market boomed in places where the baby-boomers, with lots of disposable income and with a dream of solar PV generation for their home, started to make their dream come true.

Bloomberg expects utility-scale solar to be 60% cheaper by 2040. What do you think?

I agree. The cost of manufacturing PV modules is still going down at an impressive rate, greater than 10% a year. All the other costs will continue to go down. I am fairly confident that we will reach that projection.

How will residential solar uptake be affected by growth of utilities-scale solar?

Globally, all three market segments (residential, commercial and utility-scale) will continue to grow, at about the same rate. This will vary from country to country. For example, in Australia, the PV market was essentially a residential one from 2002 to 2014. The commercial and utility-scale applications are now growing very fast in Australia. In China, the situation is almost exactly the opposite.

What holds homeowners back from residential solar in markets where uptake has been slow?

Mostly the initial investment but also ignorance about the technology. We need to continue the education of the people, not only about the technology but about the economics of PV. The current PV market can be compared to the car market in the 1960s. Even if today only a small percentage of households or commercial companies have PV, we have to expect that within 20 years every house will have its own PV array.

How do you expect solar uptake in slow markets to respond once battery costs come down?

Slow markets are driven by capital investment constraints. Batteries should be interesting mostly for retrofit; that is, people who already have made the decision to install a PV system and are unhappy with the price they receive from the utilities.

What holds us back from 100% conversion of light into energy?

The temperature of the source (the sun, in this case) and of the receiver (the solar cell) are the fundamental limiting factors for the photovoltaic conversion efficiency, keeping it below 90%. There are several concepts that would allow reaching PV efficiencies in the range of 80%. The most practical concept consists in superposing solar cells with increasing band gap and using concentrators. This concept would allow conversion of almost the entire solar spectrum while adding the voltage of all the different superposed cells. Under concentration, this multi-junction cell concept has already demonstrated 46% efficiency with a four-junction two-terminal device. There is a good chance researchers will reach the 50% efficiency threshold before the end of the decade.

What limit do you think exists for conversion?

If we think about efficiency independently of cost, I believe that by 2035 we would have multi-junction solar cells with efficiencies reaching 60%. In theory, we should be able to reach about 85% as a possible ultimate limit, but I am not sure how practical it would be and when we would reach this value. Not during this century.