Development of affordable building equipment and services for future "Energy Plus houses" (Plus-Hybrid)

"Plus-Hybrid" integrates knowledge and experience from current activities and complement them by adopting a holistic approach, considering the intelligent interconnection of components as well as managing the planned efforts and human resources in time. The goal of this project was to develop affordable building equipment and services for future "Energy Plus houses".

Short Description




Starting point/Motivation

Solar hybrid systems in combination with other technologies have not proven to be attractive, efficient and economic alternatives to matured individual technology systems yet. The research project "Plus - Hybrid" will integrate knowledge and experience from current activities and complement them by adopting a holistic approach, considering the intelligent interconnection of components as well as managing the planned efforts and human resources in the given time frame. The goal of this project is to develop affordable building equipment for future "Energy Plus houses".

Contents and Objectives

The hybrid system consists of two matured technologies, namely PV/T-collectors and heat pumps combined with ground heat storage. An adapted control of the overall energy management will be implemented. Following the principles towards a reasonable and visible market position of future Energy Plus houses interrelated work packages are planned within this project. According to the requested contract amendment the smart design of the application will be set up and related performance targets will be achieved within 33 months.

Those are:

  • Integrated building concept
    The innovative combination of energy efficient components such as hybrid collectors (water cooled Photovoltaic), heat pumps and novel storage concepts can lead to an increase of solar electric gain of up to 20%. Furthermore ground storage of the absorbed heat energy significantly improves the COP of the used brine heat pumps.
  • Decentralised Energy Plus houses
    The integration of renewable energy sources in buildings generates energy for domestic hot water, heating and electricity where the energy is used. The surplus of the solar electricity will be supplied partly into batteries and partly to the public grid.
  • Concrete Implementation and analytical monitoring
    Potentials for optimization will be generated from data collected by a monitoring system within an outdoor laboratory (Haus K.) and by empirical data. The focus lies on feasibility of the system and towards the envisaged market segment.
  • Costs vs. benefits
    The objective is to demonstrate the expected significant performance improvements in terms of economic feasibility in comparison to existing technologies.


Plus-Hybrid intends to produce onsite more solar electricity as consumed (especially by the heat pumps) to substitute fossil and nuclear shares of the electricity in the grid and to provide the surplus to the surrounding settlements/districts. Improving overall energy efficiency of single family and terraced houses and promoting a sustainable path is the goal of this project. For validation the co-action of the used components are monitored in one outdoor laboratory. Results and conclusions will be transferred into the industrial optimisation process with respect to the design and size of the hybrid collectors, the brine heat pumps and the ground heat storage facilities.


During the first project period, an integrated building concept was developed and adopted to the first case study (Haus R.). An optimization of all Plus-Hybrid components as well as a risk assessment of possible extreme weather conditions were conducted. Unfortunately the first outdoor laboratory was cancelled unexpectedly by the building developer. Therefore further building developers were contacted and several information and promotion events were held, at which the Plus-Hybrid concept was presented.

Through dissemination activities (complete list of events can be found in chapter 4), the innovative idea has been spread among target groups of interested investors. One of them and his willingness to cooperate could match the different interests and the outdoor laboratory respectively the demonstration object could be realized during the last quarter of the project (Haus K.). Since then, the demonstrator undergoes a monitoring program, which will be continued above the project end. Some main findings of the project will be outlined hereafter:

  • Investment costs for HVACR are around 250 - 470,- € / m² (net floor area) depending on the site conditions.
  • The comparative analysis with competitive technologies yield that the investment costs for Plus-Hybrid is roughly 60 - 80% of sustained competitors.
  • Of relevance for follow-up projects might be also the utilisation of the following cost saving possibilities.
  • For new buildings the height of the ground heat storage can be significantly lowered (45cm instead of 2m excavation).
  • The larger the area of the ground heat storage with sizes of e.g.1.000 to 5.000 m, the lower the specific costs per m².
  • Hybrid collectors should undergo manufacturing related developments in order to upgrade them in a sense of using the 'Economy of Scale" of this product.
  • Integrating an energy management system allowing the adjustment of the different components is recommended. The challenge is to use synergies from the early planning phase onwards, as products are using distinctive software often not compatible with each other.

Prospects / Suggestions for future research

Starting point of investigating niche markets for Plus-Hybrid has been the European KISPIMS project3. Specific investment costs from different European studies have been examined and synthesised with realisation potentials till 2020. Thereafter the cumulated investment volume for renewable energies will be in the range of 28 Bill. € in Austria. Out of this estimated volume nearly 25% or 7 Bill. € are expected to be invested into building integrated energy solutions.

In order to achieve more experiences similar to the Plus-Hybrid, outdoor-laboratories will be needed. The construction of another reference building, using the same hybrid technologies as Plus-Hybrid, has already begun and will be completed in 2014.

The necessary allowances from the local authorities have been given and its realisation is foreseen in 2014. Furthermore new investors are waiting for feedback from building users of the outdoor-lab regarding the performance of the chosen solutions The awareness campaign triggered by Plus-Hybrid project seems to work properly.

Solar hybrid systems in combination with ground heat storage could demonstrate to be an attractive efficient and economical alternative to matured individual technologies within the Plus-Hybrid outdoor-laboratory. Nevertheless, the project team recommends more flagship projects in order to underline the found results. For a robust market introduction impact assessments on the influence of current market values should be part of the supposed flagship projects.

In order to transfer conclusions from the "rural area" towards the "urban areas" some actual co-financing opportunities might be of interest. Call for proposals with regard to "City of tomorrow" and to the "Smart City Initiative" of the EC are published for the time being. Its accompanying measures might be used to underpin the main outcomes of Plus-Hybrid.

Project Partners

Project management

Univ. Prof. Arch. DI Dr. Martin Treberspurg
Institute of Structural Engineering, University of Natural Resources and Life Sciences, Vienna

Project or cooperation partner

  • Ing. Helmut Schmiedbauer-Wenig
  • DI Wilhelm Hofbauer
  • WSB Blockhaus GmbH
  • Josef Seidl

Contact Address

Univ. Prof. Arch. DI Dr. Martin Treberspurg,
Institute of Structural Engineering, University of Natural Resources and Life Sciences, Vienna
Tel.: +43 (1) 476 54 5260