This publication was authored by several members of the Austrian Universities and other leading scientific institutions dealing with the issue of energy and efficient use of energy. Head of the authorteam is Ao.Univ. –Prof. Dipl. Ing. Dr. Techn. Wolfgang Streicher. The publication is a survey as part of the government initiative “Sustainable Development”. The initiative is under the patronage of the Federal Ministry for Traffic, Innovation and Technology.
Motivation
The energy demand of new buildings has been decreased significantly during the last 25 years. This is due to the development of new building materials and building technology. Whereas 10 years ago common windows had a U-value of 3 W/(m²K) today’s U-values are half of this at the same price. Similar developments have been achieved for other building materials which results in a specific energy demand of only one sixth (50 kWh/m²a) of today’s buildings compared to buildings 30 years ago without additional costs. With little higher investment cost the energy demand can be decreased even further. Low energy buildings (or passivehouses) have different demands for the heating systems than conventional buildings. This research project deals with these demands and an analysis of various heating systems with respect to end-use and primary energy demand, greenhouse relevant emissions, heat delivery costs (including capital costs) and qualitative criteria.
Content
Following a general introduction two passivehouses which were energetically monitored within the EC-project CEPHEUS were simulated in TRNSYS. The results were compared to the measurements and a sensitivity analysis of various parameters for the simulation compared to the measured room temperature course was undertaken.
A set of user behaviour patterns (ventilation, room temperature, presence, internal gains ..) was developed using a questionnaire in 53 apartments of low-energy multi family buildings, the measurements in the EC-project CEPHEUS, and an additional literature research. Using these data two reference multi family buildings, insulated according to passivehouse criteria, were set up for the simulation.
Following this, nine different heating systems for such buildings (4 air heating and 5 water heating systems) with the heat sources decentralized air/air/water heat pump, central ground coupled heat pump, central pellets or gas burner, and decentralized pellets or tiled stove were described and qualitatively analyzed. Four out of these systems (decentralized air/air/water heat pump, centralized ground coupled brine/water heat pump, centralized gas- and pellets burner, all centralized systems using two-pipe heat distribution systems) were simulated in detail using the simulation tool TRNSYS. They were compared according to end-use and primary energy demand, CO2-equivalent emissions, heat delivery costs (including capital costs), and their sensitivity for changing user behaviour.
Additionally a sociological analysis using questionnaires and additional literature review was undertaken to evaluate the user demand and user acceptance for the various heating and heat delivery systems. Aims of the project The main goal was the development of a comprehensive evaluation method for heating systems for buildings insulated according to passivehouse criteria.
Methods used in the study
Questionnaire, measurements and literature review; evaluation using statistical methods, set up and use of
simulation models using the tool TRNSYS.