Urban heat island phenomenon in Central Europe

The urban heat island (UHI) phenomenon is characterized by significantly higher temperatures in metropolitan areas as compared to the surrounding suburban and rural neighborhoods. In this context, this paper presents a preliminary report pertaining to an ongoing EU-supported research project, which investigates the urban heat island phenomena in Central Europe. First, the background and general scope of the UHI phenomena are discussed. Subsequently, the paper investigates the manifestation of the urban heat islands phenomena (especially in the city of Vienna) and evaluates possible mitigation and adaptation strategies

Monitoring and modeling of the urban micro-climate

Urban heat island phenomenon (UHI) is considered to be one of the major challenges encountered this century by the human kind. This phenomenon is characterized mainly by air temperatures in the city that are higher than those in the surrounding areas. Reasons are, amongst other things, the morphology and density of urban spaces as well as the thermal and radiative properties of outdoor surfaces. The UHI effect represents a challenge for careful and proper building design and operation, as micro-climatic data are typically available only for few locations in the city. As a result, planning, retrofit, and mitigation measures for buildings cannot count on reliable weather information for the exact locations of intended building projects. In this context, this paper presents results of an ongoing research project, which is concerned with prevention, adaptation, and mitigation measures pertaining to the urban heat island phenomenon. An important component of this project addresses the variation in the mirco-climatic conditions in different locations in the city and if and how such variations could be accounted for. Specifically, weather information was collected with a mobile weather station at various locations within the city of Vienna. Collected data from multiple - morphologically differentiated - locations around the city were compared with the simultaneously monitored general weather conditions via a stationary weather station. The findings are expected to support the development and validation of high-resolution climatic boundary condition models for building design and operation support

Short-term occupancy implications of digitally provided outside views in window-less rooms

This paper investigates the perception and performance of occupants in rooms with and without visual connection to outside. Thereby, experiments were conducted with two groups of participants in a laboratory containing two test cells. One of the cells is equipped with a flat panel display, which acts as a virtual window. The other cell has no such display. Participants in the experimental group were exposed, via the virtual window, to different scenes. The control group in the window-less room was not exposed to such treatment. During the experiments, participants were asked to fill in a questionnaire regarding indoor environment. Additionally, they were asked to perform a number of typical problem-solving tasks. The discussion of the experimental results addresses the question, if and to which extent the existence of a virtual connection to the outside world in window-less spaces can improve occupants' perception and performance

Multi-stage optimal design of energy systems for urban districts

Urban districts develop in a dynamic manner over multi-year horizons with new buildings being added and changes being made to existing buildings (e.g. retrofits). Nevertheless, optimization models used to design urban district energy systems (DES) commonly consider a single, “typical” year for the design. This practice, however, does not allow for energy design decisions to be made in multiple phases in order to reflect a district’s development phases. This paper addresses this issue and presents a novel optimization model that allows the multi-stage optimal design of urban DES. The model identifies the cost-optimal technology investment decisions across a horizon that spans multiple years, while also calculating the energy system’s optimal operating patterns in order to meet the district’s energy demands. The evolution of the district’s energy demands and aspects like the evolution of technology costs and energy carrier prices are considered in the model. The model is applied to a new urban district in Zurich, Switzerland, for which 5 development stages are considered with new buildings of various types constructed in each phase. A multi-stage DES design plan is developed for the period 2021-2050, which includes large energy technology investments for each new development phase, but also smaller ones in the intermediate years between 2021 and 2050. The model specifies the amount of energy generated by each technology installed in each year, as well as the contribution of renewable energy in covering the district’s energy demands

Assessment of Renewable Energy Integration for a Village Using the Energy Hub Concept

AbstractThe built environment represents a major share of global energy consumption. To effectively reduce the energy consumption of urban conglomerations, concepts to sufficiently integrate and manage energy from renewables are necessary. In this paper the energy-hub concept will be applied, which describes the relation between input and output energy flows and can be used to optimize the energy consumption during planning and operation. The concept will be used to evaluate a number of future energy scenarios for a village in Switzerland which has the goal of eliminating the consumption of fossil fuels. As a starting point the existing situation concerning the energy demand of the village with respect to different uses, the different energy carriers, their origin, their distribution and networks is captured and analyzed. In the next step the potential for different means of decentralized energy production is evaluated. Decentralized energy production includes building integrated or local renewable energy production by photovoltaics, biomass, or small hydro power. In the third step, different future energy scenarios for an energy sustainable community are defined. These different scenarios are distinguished by their scale of implementation. Finally an energy hub model of the village is developed and used to evaluate the different energy scenarios

A GIS based methodology to support multi-criteria decision making for the retrofitting process of residential buildings

This paper presents a workflow to support the decision making for building retrofit and building systems update at urban scale. The workflow includes i) a method to extract information from a geographical information system including information on building characteristics, building systems and building typology, ii) a method to evaluate the current and future energy demand of buildings using a dynamic building simulation tool, and iii) an updated version of the energy hub approach to evaluate best performing options in terms of energy systems update. The developed method is applied to the city of Zurich to evaluate the optimal energy system update for all existing buildings within the city. Modelling results include best performing options in terms of CO2 emissions, renewable energy share, or energy efficiency while minimizing resulting costs for possible system and retrofitting solutions

A critical case study of decision criteria in architectural competitions

This paper analyzes a number of design proposals submitted within the framework of a large architectural competition in view of their eco-efficiency. As all new or refurbished buildings in Central Europe need to meet certain minimum energy performance requirements, many architectural competition announcements encourage participating planners to propose low-energy, passive or even plus-energy buildings, and also to take into account the ecological performance of building parts. Especially for public buildings, which are often seen as role models, competition announcements feature many environmental criteria addressing building envelope, HVAC-systems, and eco-impact of materials. It is difficult to compare project submissions (for example in terms of energy performance), as the quality and amount of information for each project varies widely. In most competitions, a professional jury chooses the “best” projects and it is debatable if ecological and energy performances are considered in the process. In this context, this paper presents results of a case study conducted in Austria. The entries of a competition for refurbishment and extension of a school building are analyzed using submitted project narratives as well as simple heating demand calculations. The outcome is subsequently compared with the Jury's final ranking of the submissions. The results can shed some light on the following questions: Do the competition entries provide sufficient information to evaluate their thermal and ecological behavior in general? Did the ecological and thermal performance influence the outcome of the competition and final Jury's ranking of the submitted proposals