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The energy topic has become increasingly important in architecture: since buildings are big consumers of energy and architects and the public are interested in energy as never before. [Scognamiglio 2008] The Energy Performance of Building Directive (EPBD) [EU 2010] establishes that starting from 31st December 2020 all new buildings have to be Nearly Zero Energy. The main architectural implication for this condition is that if up until now the domain of design was the building itself, now it is the building and possibly other spaces, that have to be conceived for placing the energy generation devices. Photovoltaics (PV) is particularly suited for reaching the (Nearly) Net ZEB status, due to its technical features, the existing knowledge on how to use PV in buildings, and since it is the easiest and most reliable way to get the (Nearly) Net Zero Energy objectives. [Torcellini 2006] A relevant international effort on the subject of the Net Zero Energy Buildings (Net ZEBs) - Net ZEB meaning that the buildings are connected to an energy infrastructure - is ongoing in the International Energy Agency (IEA), joint Solar Heating and Cooling (SHC) Task 40 and Energy Conservation in Buildings and Community Systems (ECBCS) Annex 52, titled “Towards Net Zero Energy Solar Buildings” [IEA 2008a]. The authors of this paper, all participating in the IEA research group, investigate how the use of PV for Net ZEBs can influence the building’s design, taking into account different building typologies (e. g. new ones vs. existing ones, listed buildings, etc.). Similarities and differences between PV and Solar Thermal (ST) are discussed, too. The paper results in defining some architectural issues for using PV in NZEBs design, which implie to re-think the way buildings are designed.
Net Zero-Energy Buildings (NZEBs) have received increased attention in recent years as a result of constant concerns for energy supply constraints, decreasing energy resources, increasing energy costs and rising impact of greenhouse gases on world climate. Promoting whole, building strategies that employ passive measures with energy efficient systems and technologies using renewable energy, became a European political strategy since the publication of the Energy Performance of Buildings Directive recast in May 2010 by the European Parliament and Council. Designing successful NZEBs however, represents a challenge since the definitions are yet generic assessment method and monitoring approach are under development and the literature is relatively scarce about the best sets of solutions for different typologies and climates likely to deliver an actual and reliable performance in terms of energy balance (consumed vs generated) on a cost-effective basis. Beside this, the lessons learned from already built NZEBs examples are relatively scarce. The authors of this paper, who are participants in the IEA SHC Task 40-ECBCS Annex 52, “Towards Net Zero Energy Solar Buildings”, are willing to share insights from on-going research work on some best practice leading NZEBs residential buildings. Although there is no standard approach for designing a Net Zero-Energy Building (there are many different possible combinations of passive and efficient active measures, utility equipment and on-site energy generation technologies able to achieve the net-zero energy performance), a close examination of the chosen strategies and the relative performance indicators of the selected case studies reveal that it is possible to achieve zero-energy performance using well known strategies adjusted accordingly to balance climate driven-demand for space heating/cooling, lighting, ventilation and others energy uses with climate-driven supply from renewable energy resources.
“Net Zero-Energy Building” has become a popular catchphrase to describe the synergy between energy-efficient building and renewable energy utilisation to achieve a balanced energy budget over an annual cycle. Taking into account the energy exchange with a grid overcomes the limitations of energy-autonomous buildings with the need for seasonal energy storage on-site. Although the expression, “Net Zero-Energy Building,” appears in many energy policy documents, a harmonised definition or a standardised balancing method is still lacking. This paper reports on the background and the various effects influencing the energy balance approach. After discussing the national energy code framework in Germany, a harmonised terminology and balancing procedure is proposed. The procedure takes not only the energy balance but also energy efficiency and load matching into account.
The concept of Zero Energy Building (ZEB) has gained wide international attention during last few years and is now seen as the future target for the design of buildings. However, before being fully implemented in the national building codes and international standards, the ZEB concept requires clear and consistent definition and a commonly agreed energy calculation methodology. The most important issues that should be given special attention before developing anewZEB definition are: (1) the metric of the balance, (2) the balancing period, (3) the type of energy use included in the balance, (4) the type of energy balance, (5) the accepted renewable energy supply options, (6) the connection to the energy infrastructure and (7) the requirements for the energy efficiency, the indoor climate and in case of gird connected ZEB for the building–grid interaction. This paper focuses on the review of the most of the existing ZEB definitions and the various approaches towards possible ZEB calculation methodologies. It presents and discusses possible answers to the abovementioned issues in order to facilitate the development of a consistent ZEB definition and a robust energy calculation methodology.
The international cooperation project IEA SHC Task 40 / ECBCS Annex 52 “Towards Net Zero Energy Solar Buildings”, attempts to develop a common understanding and to set up the basis for an international definition framework of Net Zero Energy Buildings (Net ZEBs). Th e understanding of such buildings and how the Net ZEB status should be calculated differs in most countries. This paper presents an overview of Net ZEBs energy calculation methodologies proposed by organisations representing eight different countries: Austria, Canada, Denmark, Germany, Italy, Norway, Switzerland and the USA. The different parameters used in the calculations are discussed and the various renewable supply options considered in the methodologies are summarised graphically. Thus, the paper helps to understand different existing approaches to calculate energy balance in Net ZEBs, highlights the importance of variables selection and identify possible renewable energy supply options which may be considered in calculations. Finally, the gap between the methodology proposed by each organisation and their respective national building code is assessed; providing an overview of the possible changes building codes will need to undergo in the coming years.
This paper summarises the state of two research phases within the scope of the IEA Task 40 / Annex 52 "Towards Net Zero Energy Solar Buildings" [1]. The first objective is a cross section analysis of a comprehensive collection of more than 280 international zero energy buildings. The aim is to show trends, motives of actors, as well as their method to reach the zero energy balance. Secondly, an in-depth study shows a rough analysis and characteristics of 50 exemplary Nets ZEBs from different countries and climate regions, as well as their combinations of measures concerning energy efficiency and renewable energy supply.
It is shown that diverse actors with miscellaneous motives have lead to a lot of different building variations. Typical strategies can be assigned to the typology groups "small residential building", "apartment building" and "non residential building". Net ZEBs are much more energy efficient than average buildings which were built according to national construction and energy regulations. None of the leading Net ZEB examples exist without generation of PV electricity. Trends give an outlook of current and possible future combinations of technologies and passive measures for the realization of (future) net zero energy buildings.
Image restoration is a process used to remove blur (from different sources like object motion or aberrations) from images by either non-blind or blind-deconvolution. The metrics commonly used to quantify the restoration process are peak signal-to-noise ratio (PSNR) and structural similarity index measure (SSIM). Often only a small sample of test images are used (like Lena or the camera guy). In optical design research PSNR and SSIM are not normally used, here image quality metrics based on linear system theory (e.g. modulation transfer function, MTF) are used to quantify optical errors like spherical or chromatic aberration. In this article we investigate how different image restoration algorithms can be quantified by applying image quality metrics. We start with synthetic image data that is used in camera test stands (e.g. Siemens star etc.), apply two different spatially variant degradation algorithms, and restore the original image by a direct method (Wiener filtering within sub-images), and by an iterative method (alternating direction method of multipliers, ADMM). Afterwards we compare the quality metrics (like MTF curves) for the original, the degraded and the restored image. As a first result we show that restoration algorithms sometimes fail in dealing with non-natural scenes, e.g. slanted-edge targets. Further, these first results indicate a correlation between degradation and restoration, i.e. the restoration algorithms are not capable of removing the optically relevant errors introduced by the degradation, a fact neither visible nor available from the PSNR values. We discuss the relevance in the context of the automotive industry, where image restoration may yield distinct advantages for camera-based applications, but testing methods rely on the used image quality metrics.