urban pv+geotherm - Innovative concepts for the supply of large volume buildings/ quarters with PV and geothermal energy

The use of renewable energies in inner city locations is mostly linked to higher costs andconsidered as problematic. The aim of this project was to optimize (cost and energy) heating (and where required, cooling) using geothermic and photovoltaic for an urban, densely-built development area. With the project´s findings it will be easier to ecologically and economically plan the use of renewable energies especially in urban areas.

Short Description




Starting point/Motivation

The practical application of an energy concept involving photovoltaics, geothermal energy, heat pumps and mass storage in densely populated neighborhoods is a big challenge due to space restrictions. Implementing geothermal applications for the heating and cooling of buildings and working with various heat resources is difficult enough even without space problems.

Previous experiences have shown that ineffective planning and execution cause much lower coefficients of performance/rates of utilization of heat pumps in geothermal systems than would normally be expected. Additionally generating electricity from photovoltaic power at the highest possible percentage or using surplus energy from the grid, both procedures lead to a further optimization parameter which increases the complexity.

Contents and Objectives

The project aims to develop concepts for an energy and cost optimized combination of geothermal energy (heat pumps), photovoltaics and other locally available renewable energy sources for heating (and where required cooling) in urban, densely-built development areas. Special weight is given to storage technologies and building services engineering.

There are 17 development areas in Vienna at the moment and some of them cannot be connected directly to district heating. Renewable energies are politically preferred compared to natural gas currently.

Of particular interest, especially in a mid- and long- term view, are new concepts for the heating and cooling supply of city areas out of 100% on-site renewable energy (without involving district heating or natural gas.

The analysis and optimizations were carried out based on the city development area in the 20th district of Vienna. The master plan for apartments, offices, construction classes, etc. for this area is basically made, but the energy concept had not been prepared by then.


To start with a rough analysis of the particular geothermal and solar conditions and other locally available renewable energy sources were worked out. After setting up various scenarios, an optimization via PHPP, POLYSUN, Earth Energy Designer, FeFlow and MS Excel followed. The conditions in Graz, Linz, Salzburg and Innsbruck were also analyzed via balanced simulations.

An advisory committee discussed the outcome concerning technical feasibility, system design and economical and ecological comparative calculations. The results have been published to make the utilization of renewables in urban areas more accessible for as many builders and planners as possible.


The research results at the project start indicated that heat sources and heat sinks connected to a low-temperature distribution network, and earth probe storage systems would be advantageous. It turned out that there were a sufficient amount of renewable energy sources locally available to cover 100% of the energy demand. Solar energy (for thermal and electric usage), energy from waste water, external air and waste heat of cooling systems were identified as the relevant energy sources.

The earth probe storage systems would not be used as energy sources but as load balancing bridge elements between heat supply and demand.

The additional costs compared to a gas supply are moderate and compensable by a realistic funding approach. The project shows clearly that the realization of such concepts is not just ecologically advantageous but technically and economically feasible.

Prospects/Suggestions for future research

Locally available renewable energy sources will be a big part by designing power supply concepts for new city districts in the future. Low temperature systems such as underfloor or wall heating will be inextricably linked to the process.

Considering the current energy prices funding for innovative and sustainable technologies will be necessary to get things moving. Financing and funding opportunities for the usage of all in cities available heat sources (waste heat, solar energy, channel waste water energy, external air, etc.) would be particularly desirable.

Project Partners

Contact Address

DI Franz Zach
Mariahilfer Straße 136
A-1150 Wien
Tel.: +43 (1) 586 15 24-106
Fax: +43 (1) 586 15 24-340
E-Mail: franz.zach@energyagency.at
Web: www.energyagency.at