April 19, 2018

Cutting-edge construction: Plus Energy Office Building at TU Wien

© TU Wien | Alexander David

Austria's largest plus-energy-office high-rise building with the largest photovoltaic system integraded into the façade is located at Getreidemarkt in Vienna where several faculties of TU Wien are located. The building is the world‘s first office tower that produces more energy i than is required to operate AND use the building.

On April 12, 2018 Class 2017-2019 of the MSc program Renewable Energy Systems visited this innovative high rise building as part of the Module „Solar Energy – Solar Heating and Photovoltaic“.
The Plus Energy Office Building is a unique research and construction project implemented by TU Wien in cooperation with the Federal Ministry of Science, Research and Economy (BMWFW) and the Federal Real Estate Company (BIG).

The approx. 55 m-high building was constructed 1969-71 and was rebuilt during a three year planning and building period. Today it has a net floor space of 13,500 m² over 11 floors for around 800 TU Wien employees, and a capacity for up to 1800 individuals incl. seminar rooms and lecture halls.

Solar energy is converted directly into electrical energy (current) via the photovoltaic system mounted on the roof and integrated into the facade (in total 2,199 m²), while a smaller quantity of electrical energy is obtained through the energy recovered from the lift. If energy requirements are less than the energy output, the surplus is transferred to and used by neighbouring buildings at TU Wien's Getreidemarkt campus.

The basement of the building houses a server room, and it is the waste heat from this that is used to heat the building in the colder months. If there is insufficient waste heat available from the server at any one time, extra heat (thermal energy) is obtained from Vienna's district heating network to cover this shortfall. In the warmer months, the waste heat from the server cannot be put to good use and has to be dissipated to an energy sink, i.e. into the ambient air and harnessed via two hybrid cooling towers. Depending on the temperature of the ambient air, cold air is obtained directly from the cooling towers via free cooling, or indirectly via an ultra-efficient chiller. This cold air is then used to cool both the server room and the building itself.

The building also has a night ventilation system that helps considerably to cool down the building. If the surrounding conditions are right, the night ventilation windows and flaps open automatically and allow the cool night air to flow through the building.

The local energy sources available for energy production supply a limited amount of energy. To ensure that this covers the consumption by all the energy services and achieves the overriding goal of a 'comfortable indoor temperature', energy efficiency must be increased. By reducing heat loss and input, the building is uncoupled extremely well from the surrounding environment. This is guaranteed by a number of different measures: extremely good insulation and an air-tight building shell, shutters providing shade, an ultra-efficient ventilation system with heat and moisture recovery, and insulation of pipework, fittings and units.

Internal loads also need to be reduced. Every component of the Energy-plus office tower block that consumes energy was investigated and optimized. As a result, only energy-efficient equipment is used, and only when it is really needed. This applies to all energy consumers in the building – the computers, the emergency exit lighting, and even the coffee machines. Intelligent technology is integrated into the building, consisting of well-planned, need-based systems as well as intelligent algorithms to control these systems. The building automatically attempts to reach a state in which the lowest amount of energy is consumed, but gives users the option to manually override certain functions if needed.

In total about 9300 components have been optimized to minimize energy consumption: From 803 kWh/m2 gross floor area per year in 1970 down to 56 kWh/m² per year in 2017. With this project TU Wien was awarded  a lot of prizes … a surprise to no one.

Highlight of the tour for our students was as every year the roof top terrace in the 11th floor. There you can see the PV-modules in detail, but also enjoy a great view over Vienna.
Final conclusion: An exceptionally interesting project – the term of energy efficiency will take on a whole new dimension!

For more impressions, visit our Photo Gallery!

Detailed information on the MSc program Renewable Energy Systems: newenergy.tuwien.ac.at

Next program start: November 15, 2018

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