CABE Maintenance or Refurbishment Award

Winner Onyx Solar demonstrates good practice and innovation for its restoration Essen Customs Warehouse project.

Onyx Solar designs and produces solar photovoltaic glass for buildings. In this restoration project, the Essen Customs Warehouse was rescued from years of decay and neglect. Onyx Solar supplied 758m2 of transparent glass, installed as a skylight and curtain wall, to help breathe new life into the 1902 Flemish neo-Renaissance-style transhipment station. Here is Onyx Solar’s winning entry.


Photovoltaic glass generates free and clean energy from the sun, provides high thermal and acoustic insulation and protection from harmful solar radiation (filtering out 99% of ultraviolet radiation and 95% of infrared radiation). It minimises the energy demand of any property while increasing its value. The glass can be installed using two cutting-edge technologies (amorphous silicon and crystalline silicon). It is fully customisable in terms of size, shape, colour, degree of transparency and finishing, and it is able to replace conventional glass in different parts of the buildings: skylights, curtain walls, canopies, fence and the building envelope in general. Onyx Solar has even developed the first photovoltaic walkable floor, as well as photovoltaic furniture, capable of charging electronic devices.

Project participants     

The company has already completed more than 250 projects in five continents. It has a production capacity of 200,000m2 per year. Its certifications (IEC, UL, ISO, UNE-EN) ensure quality and have made it the most-awarded company in the photovoltaic sector, with more than 75 awards and recognitions.

In the old customs warehouse specifically, the amorphous silicon glass offers the combination of aesthetics and functionality. This solar PV glass shows the same mechanical properties as a conventional, architectural glass used in construction. It follows the most stringent safety standards in construction required for architectural glass. It also generates free and clean energy thanks to the sun (active solar properties). It works very well under diffuse light conditions (overcast), when it produces more power than crystalline silicon glass, and in high temperatures. It offers different visible light transmittance levels – up to 30% – as well as design flexibility since it can be tailored to the architectural needs.

“The PV skylight both illuminates the complex naturally while generating free, clean electricity from the sun”


The customs warehouse in Essen is a well-known Urbex location that has long been empty. In its heyday it was the most critical border station between Belgium and the Netherlands. The Antwerp-Roosendaal railway line, built in 1854, ensured that in the 19th century Essen became an important border post with an associated station, customs warehouse and quarantine stables. This customs warehouse was originally between the tracks and parallel to the station.

The building was designed in 1901 by the architect Wisselez and built in 1902 by the Antwerp firm Bolsée and Hargot. It is an elongated neo-Renaissance, brick-built goods shed. The front and rear façades were the entry and exit areas, and the long central aisle has raised loading bays on both sides. The roof construction with light bead is made of riveted steel English trusses and at the front of the hall on the left and right, were the office areas above a basement and oil well.The building primarily served as a transhipment shed. Wagons with goods were shunted under the roof next to the shed, then – after everything had been checked by customs – the cargo was transferred to other wagons in the shed. The locomotives turned on a turning triangle and stored water and coal. Animals were also unloaded and loaded at the quarantine stables. In the past there were more buildings – such as a wagon shed, dormitories and a water tower – on the site, but most were demolished, except for the customs warehouse. After 1975 the shed was of little use as its duties were taken over by the Antwerp docks and pile sites. The tracks leading to the shed were removed in 1993, and since 2003 the building has been listed as a monument.

After 1975 the customs warehouse was of little use and in 1993 the tracks leading to the wagon shed were removed


CABE’s conclusion

Onyx Solar demonstrated that it understood the project’s needs from the very beginning. It considered both the active and the passive properties of this new construction building, working on the photovoltaic glass design and the photovoltaic fins solution, and worked with the architectural firm on the design, adapting the configuration for their needs. Onyx Solar has proved itself invaluable, from designing to delivering the solution and providing support to the design team, the client and all stakeholders involved. Its role was to develop and provide a unique solution and a building material that pays for itself. This future-focused paragon of clean energy generates thermal and acoustic insulation as well as offsetting approximately 420 tons of CO2 and generates enough clean power to feed 1,230 light points per day. On hearing of the win, the team at Onyx Solar said: “This photovoltaic skylight installation leads the way for refurbished monuments to be made more sustainable. For us, it is a real pleasure that our innovation is once again awarded in the 
CABE Awards.”

The municipality purchased the building in 2010 with the ambition to breathe new life into it; to combine the latest technology and sustainable materials in a building of the early 20th century; and to save it for future generations. To that end, Onyx Solar supplied amorphous silicon photovoltaic glass with a medium degree of transparency (20%) for the central skylight area of the building, by incorporating 440 glass modules within the insulating chamber. The supplied modules have the dimensions of 2,200mm x 766mm.


The photovoltaic skylight is part of an Interreg Flanders-Netherlands European project in which several partners are investigating how monuments can be made more sustainable. Sustainability was paramount in the restoration and repurposing of the customs warehouse. To that end, transparent solar panels were introduced in the skylight (a long glass section in the roof), enabling environmentally-friendly electricity to be generated without solar panels marring the view of the monument. At the same time, the glass allows sufficient sunlight to pass through for a pleasant indoor climate. Rangeerloods will enjoy the benefits of 758m2 of transparent photovoltaic glass, installed as a skylight and curtain wall.

The PV skylight both illuminates the complex naturally while generating free, clean electricity from the sun. It simultaneously offsets approximately 420 tons of CO2 emissions, drastically improving the building’s energy efficiency and reducing its carbon footprint. This clean energy will avoid the use of 369 barrels of oil, which is equivalent to 58,600 litres of this polluting energy. Essen Customs Warehouse generates up to 625MWh of clean power, enough energy to feed 1,230 points of light every day. As an example, the annual energy generated would provide enough power to drive 100 electric cars along 6,840km (4,250 miles) per year.

In addition, Onyx Solar has launched an initiative to plant a tree on behalf of its clients for every square metre of photovoltaic solar glass manufactured #OneMeterOneTree. Its goal is to, on the one hand, avoid CO2 emissions into the atmosphere with its glass and, on the other hand, with the trees it plants to absorb the CO2 already emitted (“One square metre of photovoltaic glass to avoid emissions, a tree to absorb them”). Thanks to this project, in Belgium Onyx Solar has planted 758 trees in the Amazon rainforest, which will absorb 113 tons of the CO2 already in the atmosphere and help to protect the natural habitat, the restoration of the soil and local farmers as well.


The warehouse was restored for the new technological educational centre, Robotland. Technical students will have adapted practical lessons in workshops with the latest technologies in the building. Hailed as the Technopolis of the Noorderkempen, a spokesperson commented: “Thanks to the latest technologies in Robotland we can launch an industrial sciences training course in Essen for the first time.”

The building’s restoration is a good example of turning a disused space into an accessible building that will benefit and educate future generations.

Client satisfaction

Clients, users and local parties have been quick to laud its achievements.

“The installation fits perfectly in the building. The panels will generate around 20,000kWh each year. Electricity will probably be used by Robotland, an educational technology park that will be located in the building,” said Gaston Van Tichelt, Mayor of Essen.

“In recent years we have been investigating how protected monuments can be made more sustainable”, said Kathleen Helsen, Co-President of Kempens Landschap and Deputy of the Province of Antwerp.

“We set to work in a hygrothermal study. Specifically, it was calculated what type of solar panels would allow sufficient light to pass through and would not have a negative impact on the underlying steel structure of the historic roof. The result is an operational skylight that has been integrated fantastically into the restored shed,” said Jan De Haes, Deputy of the Province of Antwerp and Co-President of Kempens Landschap.    

See the project video at

The restored building now provides space for a new technical education centre – Robotland – which will benefit future generations

Winner in numbers

758m2 of photovoltaic fins
offsets 420 tons of CO2
avoids 369 barrels of oil
it generates enough clean power to feed 1,230 light points a day
the annual energy generated would provide enough power to drive 100 electric cars 6,840km (4,250 miles) per year
758 trees were planted in the amazon forest as part of the restoration of essen customs warehouse #OneMeterOneTree



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