Shuji Nakamura, together with colleagues Isamu Akasaki and Hiroshi Amano, invented the blue light-emitting diode LED in 1993, and for this, 21 years later, received the Nobel Prize in Physics. A discovery that proved sensational for its ability to increase energy efficiency and help cut CO2 emissions, responsible for climate change. On 5 May, Nakamura visited Como for the inauguration of the Festival of Light (the science outreach festival promoted and supported by the Città della Luce association and organised in collaboration with the Fondazione Alessandro Volta, running until 25 May). In this interview he spoke about the spread of his invention around the world and about the future of the energy sector and lighting.

Let's start with the award you received two years ago for inventing LEDs. How did you feel when you found out you had become a Nobel laureate?

I invented LEDs in 1993. From that year on, the Japanese press and media would come to my house regularly on the day before the Nobel Prize announcements. Every year from 1993. The press had been expecting it for some time. So I wasn't surprised. Though, given that more than 20 years had passed, I was beginning to think they would never award it to me.

LEDs took years to become commonplace and even today are not widespread enough. Given the time lag between science and consumer uptake, what is research in the lighting sector working on today that will probably become a standard in 20 years' time?

I think the slow uptake is due to the fact that initially the colour of LEDs was white, but cold. Europeans, on the other hand, love warm colours and so nobody wanted to use them. Now the warm white light of LEDs has enabled them to spread across the world. I think that in 20 years they will still be the most efficient form of lighting. LEDs now provide the same illumination as old incandescent bulbs but use one tenth of the energy. An LED bulb can last up to fifteen years. Practically a lifetime. It also saves on the use of resources and raw materials. In any case, if I were to make a prediction, laser light could be the new form of lighting, but research is still at an early stage, so I don't think it can come to market in less than ten years.

Energy efficiency is very often paired with renewable sources. When you want to turn a home into a passive house, the lighting is very often changed and solar panels are installed. What will be the energy source that definitively moves us away from fossil fuels?

I think hydrogen. Solar, wind and biomass are excellent technologies, but they have one major problem: there is no way to store the energy. Or rather there is, but only in the short term. The only limitation of renewables is that when you produce energy, you have to consume it. Whereas energy produced through hydrogen can be stored in gas form for longer periods. Hydrogen has greater potential as the energy carrier of the future.

Is hydrogen already widespread in Japan?

There are car manufacturers, such as Toyota, that have developed hydrogen-powered car models. In some cases it is also used to "power" homes, but it is very expensive and therefore not very popular.

What role do LEDs play in improving the living conditions of the 1.5 billion people who still do not have constant access to electricity?

In regions where people do not yet have access to electricity, oil lamps are usually used. But the problem is that they depend on kerosene, on petroleum, which turns out to be very expensive for developing countries. A kerosene lamp needs to be refuelled at a cost of 150 dollars a year. Now, however, it is possible to use LED lamps that run on a battery recharged by solar energy during the day. This system is very affordable and also clean. The purchase of a lamp costs around ten dollars, but these are lamps that last about three years, so three dollars a year. If they were to last longer, the annual cost would be practically zero. As if they were free.

Where do things stand, on the other hand, with their uptake in industrialised countries?

These countries are converting to LEDs, albeit gradually. In the United States we are at around 5–10 per cent uptake, in Japan over 50 per cent. But in my country there was the earthquake and the nuclear disaster at Fukushima, which led to the shutdown of all nuclear power plants. So we found ourselves facing an energy crisis, virtually without power. The Japanese government therefore asked all citizens to make their lighting systems more efficient. Now many governments are raising public awareness about the use of this new light source, because people are often inclined to choose cheaper bulbs, such as incandescent ones… which in reality last very little time. LEDs, by contrast, despite a higher initial cost, are far more cost-effective in the long run. It is a system that pays back the investment over the years.