Roofs as a city resource – energate messenger Austria

Vienna (energate) – Climate protection is decided in the cities. Michael Strebl, Wien Energie Managing Director, is convinced of this, as he made clear at the beginning of a lecture at the International Energy Industry Conference (IEWT) of the Vienna University of Technology. In the future, around 70 percent of people will live in cities. Cities are already responsible for around 76 percent of energy consumption and 70 percent of CO2Emissions responsible. For this reason, from an ecological and economic point of view, there is no alternative to the energy transition. In this context, Strebl said the roofs are the city’s natural resource.

The goal must be to equip all roof areas with PV systems where this is also technically feasible. Strebl estimates that this is possible on around 25 percent of the roofs in Vienna. Wien Energie currently operates 270 solar power plants with an output of around 70 MW. The aim of the energy supplier is to install around 600 MW of PV capacity by 2030, the equivalent of electricity for 250,000 households. However, the use of roof areas alone will not be sufficient for the PV expansion. Open spaces will also be required, Strebl said.

Challenge: heat transition

Much more decisive and also more challenging than the transformation of the electricity system, however, will be the turnaround in heating. While the electricity sector is responsible for around 20 percent of emissions, the value for heat is a good double, i.e. around 40 percent, according to Strebl. In this context, the City of Vienna wants to be free of oil and natural gas in space heating by 2040. The district heating system would already have the best prerequisites for an environmentally friendly redesign through the use of geothermal energy, for example.

The climate-friendly transformation of the around 500,000 gas boilers in the city, the equivalent of around 4.6 billion kWh, is more difficult. Here the energy supplier is working on concepts with heat pumps. Estimates by the energy supplier assume that the city of Vienna will have a total heat demand of around ten billion kWh in 2040. Up to 87 percent of this could be covered with decarbonised heat. The remainder must then be covered with the use of seasonal storage and green gas, such as hydrogen.

Challenge: fluctuating generation

Michael Strugl, CEO of Verbund, referred in his lecture to the challenges associated with the goal of a 100% electricity supply from renewables by 2030. This requires a complete overhaul of the previous energy system. An energetic increase of around 27 billion kWh means an increase in output of 19,500 MW. The current power plant output in Austria is around 24,000 MW. Since a large part of the generation will come from photovoltaics and wind power, i.e. from sources with fluctuating generation, the expansion of the network infrastructure and the creation of storage options are of great importance, according to Strugl.

Estimates assume that around ten billion kWh of electricity will have to be shifted seasonally from summer to winter. Currently, however, the storage facilities in the country are not sufficient. The necessary technologies for storage must also be discussed. Strugl assumes that these will not only be about hydraulic accumulators. He sees the main challenges for the transformation of the electricity system on the one hand in creating regulatory and legal frameworks and on the other hand in increasing acceptance among the population for the expansion of renewable energy projects. /of

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