Inspiring architects to make buildings green and good looking

Technology that integrates solar panels in roof tiles, windows and other building materials is becoming mainstream as costs drop and products become aesthetically attractive

Buildings have lots of surfaces. This may sound obvious, but until now solar photovoltaic systems have been largely installed on roofs and then as add-ons rather than as intrinsic parts of a building. The solar industry and architects believe the time has at long last come for building-integrated photovoltaics (BIPV), or solar skins, to become a mainstream solution to curbing carbon emissions and increasing renewable energy sources for buildings.

BIPV technology can be integrated in traditional building materials, such as windows or roof tiles, be flat or curved, and placed on virtually any building surface. The need for no extra space is an important advantage in cities where large solar arrays, requiring significant amounts of space, are rarely an option.

BIPV is not new. But high costs and a lack of market visibility has kept the technology in the shadows. Solar photovoltaic generating capacity worldwide reached 480 gigawatts (GW) by the end of 2018, says the International Renewable Energy Agency. In 2016, just 5 GW of BIPV was installed globally, concludes an EU-funded report on the industry.

Installations are mainly in Europe and the US, which account for around 70% of global market share. “Investments in the following years are expected to exponentially grow in these regions,” says the EU report, which predicts slower growth in other regions, most notably China and Japan. Falling prices, improved technology and growing regulatory pressure to slash carbon emissions from buildings in cities by reducing demand for grid electricity through an increase in local use of renewable energy are the main reasons for growth predictions. Europe will lead the market’s development, says the report, forecasting that installed capacity of BIPV in the region will exceed 11 GW by 2020.

The future is where your imagination takes you

“BIPV is back,” exclaimed Eric Scotto, CEO of Akuo Energy, a French renewable energy company during an event on the technology at EU Sustainable Energy Week in Brussels in June 2019. In addition to economic and energy transition arguments, Scotto insisted the industry had now mastered the aesthetics of solar skins. Previous incarnations of BIPV were “not beautiful” and for this reason dismissed by architects, he said. A big change brought in by his company three years ago was to add colour to BIPV roof tiles so they match local roofing materials and can be used on classified monuments.

Akuo’s conclusions were backed at the event by Alfonso Ponce-Alvarez, associate partner with the architecture firm Foster and Partners. Ten to 15 years ago, it was possible to argue against the technology because of questions around its environmental credentials, technical challenges, concerns about how to measure performance and a lack of clarity on supranational regulation governing the industry and buildings, he said. This is no longer the case, added Ponce-Alvarez. But he insisted on the need for awareness raising and training to make architects and the wider construction industry aware of the technology. Despite some of the controversial buildings designed by his company’s founder, world renowned architect Norman Foster, Ponce-Alvarez insisted that architects in general “operate in a very conservative and traditional sector”.

The solar sail on the Cité Musicale de L’lle Seguin, Paris, moves with the sun and shades the glass facade throughout the day while collecting optimal sunlight. Image: ISSOL

Attractive investment

In terms of costs, industry group SolarPower Europe says: “Years of intensive research and development have resulted in lower costs and improved efficiency for BIPV solutions. In addition, longer warranties and enhanced product performances, lower needs for component replacements, and a payback time often less than ten years, make BIPV installations an attractive option for most buildings.”

Potential financing solutions are the same as those for traditional solar panels, with a general agreement that, as Scotto said, “public money is very rare” and private investment is needed. He suggested owners should start thinking about roofs and potentially other parts of their buildings as elements of the sharing economy. Instead of claiming ownership, people should think about leasing roofs for BIPV projects. “We don’t own a roof, we use a roof,” he said. ISSOL, a Belgian company making solar skins for a variety of clients across Europe, including the Palais de Justice in Paris, says the cost of BIPV depends on the particular product in question. But if a traditional passive building façade costs around €250 a square metre (m2), a BIPV façade would cost around €350/m2, according to ISSOL estimates. Akuo’s Scotto said his company’s BIPV tiles cost the same as a zinc tile and a solar panel combined. With more promotion and a bigger market, the price can drop by 20% in the next two years, he added.

For Scotto, the options are endless. After the fire in Paris’ iconic Notre-Dame cathedral in April 2019, he said he received many calls about replacing the old roof with BIPV tiles. “The future is where your imagination takes you. We want to inspire.”

This article by Philippa Nuttall Jones is part of our special series looking indepth at how cities hold the key to the energy transition at FORESIGHT Climate & Energy




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