My role as an expert in solar energy is to help the Property Management administration to decide which buildings are best suited for fitting solar cells, in preparation for the contractors.
The criteria that I look at together with other colleagues at COWI are technical, financial and geographical. To put it simply, if the solar cells are to be efficient, they have to be south-facing. The roof of the building must not be too old, to ensure that the roofing materials will be in place at least as long as the solar cells.
We also have a requirement that any given installation must not be smaller than 30 kilowatts – the bigger we build, the lower the cost per kilowatt produced. Another requirement is that no more than 50% of the electricity should go out into the grid. The value of the electricity we produce and use ourselves is roughly one Swedish crown (SEK) per kilowatt-hour, while we are paid just 0,35– 0,40 SEK for the energy we feed into the grid, so there is an economic aspect as well as the matter of sustainability.
If we look further ahead, perhaps 20–25 years, I believe things will look very different. Tests are already being carried out with perovskite, a mineral which will enable solutions where solar cells can simply be painted onto walls and roofs. Then you simply connect a cable and you have electricity. Other solutions in the pipeline involve direct current networks. That’s because the solar cells produce direct current and the devices they are intended to power use DC too, so we simply lose energy converting to alternating current in between.
Storing electricity is a challenge, particularly here in Sweden where there is such a big difference between summer and winter. Batteries are developing all the time, but I personally think that hydrogen gas will be more usual in the future. We can use electricity and water to generate hydrogen, which can then be storied until the energy is needed.
I also think we will see more diversification in pricing – in 15 years, it may be free to charge an electric car when the sun is shining, but twice as expensive when it is dark.
We will also see more innovative ideas – e.g.to use new electric cars as temporary charging stations while they are waiting to be delivered to customers. There will be more. I am looking forward to the journey ahead.