Master's Thesis Lutz Schiffer


Optimized Design of the Energy Supply System and the Building Envelope

In the context of the energy transition Germany attempts to reduce the greenhouse gas emissions
by 40 % of the level of 1990. This goal can be achieved by extending renewable energy sources and
increasing the energy efficiency of energy conversion processes. Buildings use about 40 % of the final
energy demand and represent a high a potential which can be exploited by using modern energy
supply systems in combinationwith increasing the building envelope’s thermal insulation standard.
In this thesis a method is developed for optimizing the simultaneous design of the building energy
system and the building’s envelope. The state of the art in the area of building’s design is to use
an approximative algorithm for solving optimization problems. First approaches which use mixed
integer linear programming (MILP) calculate the heat demand with a static or simplified building
To consider the building envelope in a dynamic way within the MILP, a modified building model
adapted from ISO 13790 is implemented in this research.
In this model the energy demand can be covered by a number of demand-orientated energy systems
like combined heat and power units, heat pumps, electric heaters and boilers, renewable energy systems
like photovoltaic systems and solar thermal collectors as well as thermal and electric storage
technologies. The optimal composition of the building’s envelope is determined out of a predefined
number of walls, floors, roofs and windows.
The validation of the used building model by ASHRAE-Standard 140 exhibits that the heating and
cooling demand of the considered scenarios lie in the range of the reference results. The Comparison
to a more detailed model adapted from VDI 6007 shows a major deviation in annual heat
demand of 6,3 % for the considered test buildings.
A closing scenario points out the functianlity of the developed method. The optimal configuration
of the considered residential building is composed of light constructional components for the building’s
envelope in combination with an energy supply system comprising a boiler, a thermal storage
unit and a photovoltaic system.