Growing appetite for solar cells among Property owners

Energy Insights

10.01.2020 / Ulrik Pettersson

Things are moving fast in the field of solar cells, and the hope is that in the future they may be ‘painted’ directly onto the roof. The challenges right now are to show where solar energy can be used, varying access to sunlight over time, and how the energy should be stored, says Ulrik Pettersson from Buildings Department in Sweden.

Solar cells are getting cheaper and more efficient all the time, and this trend is expected to continue over the next five years. At the global level, we can expect to see annual growth of around 15–20%, 

Especially, the markets for solar energy will be growing in Asia, and probably also in the oil-producing countries in the Middle East. There is an acute need for cheap electricity in China, for example, and the bottleneck is often the grid, which cannot keep pace with the rapid expansion.

Closer to home, developments in Germany, Austria and Switzerland have also been going on for some time. A big reason for this is that the willingness to invest among home-owners is generally greater than in the UK or Sweden. But things are starting to happen here too. In fact, the solar cell market in Sweden is now expanding by 100% year on year.

One example of this development is the EST project (“Optimised Refurbishment for Efficient Solar Roofs”) headed by RISE (Research Institutes of Sweden) together with property-owners, the City of Gothenburg, Chalmers University of Technology and consultants including COWI.

The project aims to build on previous research findings in the solar cell area and embody them in actual refurbishment projects with the emphasis on costs and efficiency.

Technical challenges

The project is going well so far, despite some minor problems along the way, including planning permission. Other issues have concerned purely technical details with existing installations. The interest among property owners is increasing all the time, particularly with technical innovations arriving thick and fast.

The engagement from the industry has increased continuously since the project was launched. Several of the major players like Lindab, Soltech, and Midsummer are interested as they start to see the potential in this area.

Among others, we are translating the experience gained from another project we did with the Property Management administration in Gothenburg. Their job is to manage around 2,000 buildings, mainly schools, kindergartens and housing for the elderly.

They have taken a policy decision that 60% of the electricity used in these buildings should come from renewable energy, particularly solar cells. In fact, they have committed to spend SEK 30 million a year on installing solar cells, both on existing buildings and on new developments.

Solar roofs on a large scale

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.

Solar cells that can be ‘painted on’

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 – 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.


I have been in the industry since 1999, when I graduated from Mälardalen University College. I also studied Civil Engineering in Linköping. Solar energy has always fascinated me – the ability to generate so much power from something that is there anyway is just amazing. There is no downside to solar cells; of course it takes energy to manufacture them, but the investment pays for itself in two years. And we avoid burning fossil fuels.
What I like about my job is being involved from the original idea to seeing the finished product in place and in use. From idea to reality – that appeals to me.

Get in contact

Ulrik Pettersson
Head of Section
Buildings, West, Sweden

Tel: +46 768 56 19 82