A Multi-sensor Office-building Database for Experimental Validation and Advanced Control Algorithm Development

Data from multiple sensors and actuators has been recorded from December 2001 to March 2008 at the LESO-PB building of the EPFL campus, using the EIB/KNX bus standard. Sensors and actuators provided data on room temperature, presence, lighting level, windows opening, blinds position, electric lights and heating power. Weather data has also been collected and includes ambient temperature, solar radiation on a horizontal surface (direct and diffuse components), wind speed and direction and rain alarm. The data was written continuously to a MySQL database, each EIB/KNX telegram being recorded into the database. The primary goal of that setup was the experimental validation and checking of advanced control algorithms for the actuation of solar shadings (outside fabric blinds), electric lighting and heating equipment. With the aid of the database it was shown that such control algorithms were able to reduce significantly the energy consumption while keeping the same comfort or even improving it. Since 2002, the database has been used in various research projects carried out in LESO-PB. As of 2014 the database has been made freely accessible to the scientific community as a tool to work on.

Building envelope and solar energy optimization: a new “wizard” for architects

Marja Edelman, Maria Cristina Munari Probst, Christian Roecker

When designing a project, architects are facing more and more constraints on the building’s energy efficiency. Tougher values on insulation and energy consumption are now often combined with compulsory implementation of active solar systems - photovoltaics or solar thermal. With natural lighting, passive and active solar all competing for envelope areas, comparing results of architectural variants becomes more important and at the same time more complex. To help overcome this situation, a renowned “energy balance calculation/certification” software tool has been improved and adapted, proposing a wizard developed to meet a growing demand: obtain a quick feedback on building envelope, energy efficiency and solar strategies, especially in the early design stage, when strategies are defined. The wizard helps fulfilling various norms of different European countries, allowing architects to compare variants during this crucial phase. By simplifying data entry using smart default values derived from appropriate general choices, and by presenting a clear and intuitive user’s interface, this new tool offers practicing architects an easy access to building envelope and solar energy use optimization.

Université Catholique de Louvain-la-Neuve2011

Optimisation of Urban Form by the Evaluation of the Solar Potential

Marylène Montavon

What will the cities of tomorrow look like? This is a crucial question because in the four and a half billion years of its existence, the Earth has never been so threatened, as it is today. Since 2008 half of the world's population has lived in towns – more than 70% in rich nations. Three quarters of CO2 emissions are produced in towns, 75% of the world's energy is consumed in towns. The battle for our climate, for the continuation of our species and all other life, will be largely waged in cities. Will it be possible to create the ideal ecological town? The objective of this study is to compare actual and theoretical urban forms in order to explore the diverse effects of daylighting and solar potential on densely built-up sites. Indeed, the search for ideal solar orientations has been a persistent problem from the 19th century until the beginning of the 20th. Even today, for all our scientific knowledge and empirical experience of solar energy, making the correct choice has still not crossed the boundary from an enigmatic, tricky art into the field of an exact science. As a first step, six existing urban sites in Switzerland and Brazil, as well as two projects in the United Kingdom, a few generic models and a utopian city, were modelled and analyzed. The goal was not merely the construction of new, exemplary districts but also the transformation of existing towns. The findings have been used to assess the potential of façades and roofs located in urban areas for active and passive solar heating, photovoltaic electricity generation and daylighting. The results obtained from these different case studies revealed large variations of the potential for solar energy collection on the buildings' façades and roofs. Ideally, these investigations are expected to help architects and town planners understand how to optimise solar collection on buildings design. In addition, a study was made of the Contemporary City of Three Million Inhabitants created by Le Corbusier. According to the latter, the Contemporary City could increase the urban capacity and at the same time improve the urban environment and the efficiency of the city. Therefore the present study extracted the solar potential of this utopian city in order to assess Le Corbusier's propositions. Since 1922, Le Corbusier's studies have influenced architects and town-planners in their choice of orientations and urban forms: it was therefore crucial to discover if this reliance on Le Corbusier was justified. Solar irradiation and illuminance values obtained through numerical simulations form the core part of the method. The method adopted for the entire set of computer simulations consisted in modelling — via a computer-aided drawing piece of software, namely AutoCAD — the digital model of each building or group of buildings prior to exporting them to an urban performance analysis software (PPF/RADIANCE software package). Spatial distributions of solar irradiation and daylight fluxes over the overall building façades and roofs were calculated using ray-tracing simulation techniques to determine the appropriate placement of different solar technologies (passive and active solar, photovoltaic and daylighting). Performance indicators were used to assess the solar utilisation potential of the urban sites (e.g. statistics of sky view factors and daylight factors) in order to determine the optimal solar strategies for a given urban context. In addition, various works and sun-related recommendations that have appeared mainly since the end of the nineteenth century, together with the various scientific models and software tools pertaining to this topic, are presented in this study.

EPFL2010

Advanced Window and Lighting Technologies in net Zero Energy Buildings

Jean-Louis Scartezzini

Light has an important visual and non-visual impact on humans. Most of our information exchange, especially within office working spaces, occurs through it, our circadian rhythms are directly influenced by its presence. On the other hand, artificial lighting is responsible for a large fraction of electricity consumption in non-residential buildings. The latter becomes even more dominant within net Zero Energy Buildings (nZEB) where yearly net heating and/or cooling loads are reduced almost to nil by the way of energy savings measures and renewable energy technologies. Anidolic Daylighting Systems (ADS) are very effective façade-integrated daylighting systems which can collect and redirect diffuse daylight deep into office rooms under almost any climatic conditions: several studies have demonstrated their efficiency in the Northern and Central European regions, as well in sub-tropical climates. Recent studies have shown that their integration with high efficacy electric light sources and efficient luminaries can lead to very low lighting power densities (e.g. 3 - 4 W/m2 instead of 12 – 15 W/m2), as well as an improvement of visual comfort, visual performance and contribution to human health. As such, they offer excellent opportunities to reduce the electric lighting load in solar buildings and nZEB. An integrated day- and electric lighting system has been implemented in the south-facing office rooms of the LESO solar experimental building located on the EPFL campus in Lausanne (Switzerland). Objective visual performance and subjective visual comfort assessments were carried with 20 subjects, confirming the adequacy of this approach regarding human response factors, as well as from an energy savings perspective. A ceiling integrated anidolic daylighting system was also implemented last year in an nZEB, located in Singapore and erected through the refurbishment of an existing building. The system was based on a former study carried out on the EPFL campus by the way of a 1:1 scale mock-up office room equipped with a comparable device. Significant electricity savings, as well as visual comfort and performance improvement, were also observed in this case.