Solar facades to help create sustainable cities

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The European SmartFlex Solar facades project trials a photovoltaic 'second skin' on a building in Eastern Europe.

The European Union (EU)-supported SmartFlex Solar facades project has completed its test operation.  

A glass facade featuring a wide range of semi-transparent solar modules that were custom-designed but industrially manufactured was installed as a “second skin” on the office building of the Lithuanian glass processor Glassbel.

Solar facade provides increase in earnings

The 75 glass modules generate around 12.5MW hours of electricity every year. The photovoltaic system, which has an output of more than 15kW peak, was installed on a surface area of 600m² on the south and west facades of the Glassbel office building in Klaipeda, Lithuania, in November 2016.

The solar facade provided the architects with a wide range of design options-15 types of glass modules were used on the building.

“Printed module glass, laminating films of various colours and differently coloured solar cells can be used to custom design solar facades any way you like. The biggest challenge with our solar façade was producing the glass-glass modules, which were very large and very heavy. The largest were 3.6m long and 1.7m wide,” says Tomas Lenkimas, Head of Glassbel’s R&D department.

“In contrast, applying the photo print onto the module glass was relatively easy. The installation of the facades, which was carried out by a specialist facade engineering company, also went very smoothly.”

To measure the yield, one of the project partners, Photovoltaik-Institut Berlin (PI Berlin), installed a weather and measuring station on the roof of the office building and tested the modules on-site.

“The PV system has now been operational for six months. Based on the monitoring data we’ve gathered so far, we predict that the system’s specific yield could be up to 800kWh per kWpeak,” explains Thomas Weber, project manager at PI Berlin. Improvements during the project led to a 25% increase in earnings in parts of the plant.

Solar facades material is price competitive

According to the calculations of the project partners, the acquisition costs of a “second skin” solar facade – at around €550/m2 – are approximately the same as for a facade made of stone or metal, but are significantly lower than those of a glass-window facade, which can cost up to €840/m2.

“We even identified further cost-saving potentials during the project. But it is already clear from the test system that customised solar facades represent not only an aesthetically attractive, but also a financially viable alternative to other types of facades,” says Dr Juras Ulbikas, Senior Researcher at the Applied Research Institute for Prospective Technologies (ProTech) in Lithuania and Coordinator of the SmartFlex project.

“Furthermore, installing solar facades can help in the effort to meet statutory climate protection targets for buildings.”

An unexpected side effect of the solar facade is that it keeps the building cool. While the partial shading from the solar cells improves the heat transfer through the facade, building occupants still have an unimpeded view from their building. The second facade keeps the wind and weather at bay so windows can be opened on a rainy day.

Solar facades create sustainability

Solar power is a critical part of the puzzle when it comes to creating a sustainable city.  

However, solar power has relatively low energy densities, thereby requiring significantly larger areas to produce the relevant amount of electricity. Our cities are characterised by high-density populations, thus creating the need for even more high-rise buildings. As a result, available roof space for solar panels is limited. This is where facades and other forms of building integrated photovoltaics come into play.  

Although vertical solar panels receive less solar radiation than roofs and horizontal surfaces, in particular in the summer months, and are more affected by the compactness of the urban layout, facades feature large surface areas; in a building with 4 floors, the area of the facades can be about four times the area of the roof.  If the entire surface area is used for solar panels and shadings from nearby buildings, the total annual electricity production would triple that of the roof. 

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