Assessing Gaps and Needs for Integrating Building Performance Optimization Tools in Net Zero Energy Buildings Design
September 2013 - PDF 0.6MB
This paper summarizes a study undertaken to reveal potential challenges and opportunities for integrating optimisation tools in Net Zero Energy Buildings (NZEB) Design. The paper reviews current trends in simulation-based Building Performance Optimisation (BPO) and outlines major criteria for optimisation tools selection and evaluation. This is based on analyzing user’s needs for tools capabilities and requirement specifications. The review is carried out by means of a literature review of 165 publications and interviews with 28 optimisation experts. The findings are based on an inter-group comparison between experts. The aim is to assess the gaps and needs for integrating BPO tools in NZEB Design. The findings indicate a breakthrough in using evolutionary algorithms in solving highly constrained envelope, HVAC and renewable optimisation problems. Simple Genetic Algorithm solved many design and operation problems and allowed measuring the improvement in the optimality of a solution against a base case. Evolutionary Algorithms are also easily adapted to enable them to solve a particular optimization problem more effectively. However, existing limitations including model uncertainty, computation time, difficulty of use and steep learning curve. Some future directions anticipated or needed for improvement of current tools are presented.

A Control-Oriented Simplified Building Modelling Strategy
August 2013 - PDF 1.3MB
This paper discusses the development of control-oriented simplified modelling strategy (COSMOS) for model-base predictive control (MPC) in buildings. In MPC, a model of the system is used along with forecast information for optimal planning. A model that is as simple as possible --but accurate enough for the purpose at hand -- facilitates the implementation of a MPC strategy. This paper discusses desirable features of models intended for the specific needs of advanced control applications. A path for the creation of such models is presented, based on low-order resistance-capacitance (RC) thermal networks and their equivalent state-space formulation; such an approach provides physical insight while facilitating the treatment of the problem. The model parameters are found by applying an optimization to match the output of a building simulation model. Results include an assessment of the uncertainty of the model outputs.

An Optimization Procedure Based On Thermal Discomfort Minimization To Support The Design Of Comfortable Net Zero Energy Buildings
August 2013 - PDF 1.03MB
The European standard EN 15251 specifies design criteria for dimensioning of building systems. In detail, it proposes that the adaptive comfort model is used, at first, for dimensioning passive means; but, if indoor operative temperature does not meet the chosen long-term adaptive comfort criterion in the “cooling season”, the design would include a mechanical cooling system. In this case, the reference design criteria are provided accordingly the Fanger comfort model. However, there is a discontinuity by switching from the adaptive to the Fanger model, since the best building variant, according to the former, may not coincide with the optimal according to the latter.

Computational Optimisation For Zero Energy Buildings Design: Interviews Results With Twenty Eight International Experts
August 2013 - PDF 1.04MB
This paper summarizes a study that was undertaken to reveal potential challenges and opportunities for integrating optimisation tools in Net/Nearly Zero Energy Buildings (NZEB) Design. The paper reviews current trends in simulation-based Building Performance Optimisation (BPO) and outlines major criteria for optimisation tools selection and evaluation. This is based on analyzing users’ needs for tools capabilities and requirement specifications. The review is carried out by means of interviews with 28 optimisation experts. The findings are based on an inter-group comparison between experts. The aim is to assess the gaps and needs for integrating BPO tools in NZEB Design. The findings indicate existing limitations including model uncertainty, computation time, difficulty of implementation and steep learning curve. Future directions anticipated or needed for improvement of current tools are presented.

Design of Nearly Zero Energy Buildings Coupled With an Earth to Air Heat Exchanger in Mediterranean Climate: Development of an Analytic Model and Validation Against a Monitored Case Study
August 2013 - PDF 0.92MB
At the Passivhaus of Cherasco, located in Pianura Padana (Italy), an earth to air heat exchanger (EAHE) and natural night ventilation (in summer) are used to deliver comfort conditions with very low energy consumption. One year and a half of continuous measurements have been carried out in order to evaluate the energy and comfort performances of this building, which combines the Passivhaus concept with local architectural solutions. We present an analysis of the system constituted by building envelope and EAHE. Monitored data (with a particular focus on cooling potential) were evaluated with the use of established indicators and compared with simulations performed by coupling dynamic simulation software (EnergyPlus) and an analytic model for the EAHE. Based on this analysis a simplified steady-periodic model is developed to provide an estimate of the behaviour of the coupled system building envelope (including night ventilation) and EAHE from the point of view of energy and comfort, over a period of few weeks. The model is validated towards monitored data and shows a good agreement in terms of temperature profile, with a slight phase discrepancy, as expected based on the simplifying assumptions about thermal capacity effects.

Time-Lapse Photography and Image Recognition to Monitor Occupant-Controlled Shade Patterns: Analysis And Results
August 2013 - PDF 1.13MB

This paper presents a high-level overview of a methodology for analysing windows shade use is existing buildings. Time-lapse photography is paired with a robust image recognition algorithm to facilitate assessment of shade use and identify any possible trends. The methodology applied on a high-rise building consisting of multiple open plan offices. The analysis showed that the mean shade occlusion and the shade movement rate depend on facade orientation, with the near-south facade having the highest values and the near-north facade having the lowest ones. An average shade use rate of 0.5/day was observed, with the 72% of the shades never adjusted, throughout the period of observation.

Tool for Design Decision Making: Zero Energy Residential Buildings in Hot Humid Climate
August 2013 - PDF 1.2MB
Informed decision-making is the basis for the design of Net Zero Energy Buildings (NZEBs). This paper investigates the use of building performance simulation tools as a method of informing the design decision of NZEBs. The aim of this study was to develop a design decision making tool, ZEBO, for zero energy residential buildings in hot climates and to evaluate the effect of a simulation-based decision aid, on informed decision-making using sensitivity analysis. An assessment of the role of the BPS tools used in informing the decision-making was ascertained through cases studies, usability testing and several self-reported metrics. The paper provides results that shed light on the effectiveness of sensitivity analysis as an approach for informing the design decisions of NZEBs.

Optimization of Net-Zero Energy Solar Communities: Effect of Uncertainty Due to Occupant Factors
August 2011 - PDF 0.38MB
This paper applies an energy optimization methodology to evaluate the impact of occupant factors on the net-energy consumption or generation of a community of net-zero energy or near net-zero energy homes located in Montreal, Quebec. The building simulation software EnergyPlus was used for energy simulations and Canadian national statistics were used to model occupant behaviour. Results showed that diversifying building designs can decrease the impact of variability of occupant behaviour and reduce peak loads.

Strategies for Reducing Peak Demand in Net-Zero Energy Solar Homes
August 2011 - PDF 0.62MB
This paper investigates strategies to reduce peak loads in net-zero energy solar homes through the coordination of different design and operation strategies. The concept of net-zero energy homes, roughly defined as grid-tied houses that supply their energy needs with renewable energy sources over a period of interest, has gained in popularity in recent year. In spite of the clear advantages of this design approach, it is necessary to address the issue of peak loads and their impact on utility grids. Even if the net-zero energy goal is achieved during the period of assessment (e.g., one year), significant imbalances may be observed at smaller time scales. For instance, in northern latitudes, the generation of PV panels typically exceeds the energy use of the house during the summer months, while in winter the energy use of the house is larger than the generation of the PV system. Fluctuations of the ratio generation/use are also registered during the daily cycle. If a net zero energy house draws energy from the utility grid during peak periods, its impact on the grid will be similar to that of a conventional home, with the subsequent need for increased generation and transmission capacity.

Energy Performance, Comfort and Lessons Learned From a Near Net-Zero Energy Solar House
June 2011 - PDF 1.63MB
This paper examines the performance of a Canadian near net-zero energy solar house known as ÉcoTerra located near Montreal. The total energy consumption and energy end-use breakdown are presented and several findings from the energy analysis are discussed such as the importance of occupant behavior, occupant comfort and the improvements that could lead to achieving full net-zero energy performance . It was demonstrated that large reductions in energy consumption can be achieved with little effect on comfort. Occupants affect the loads significantly and need to be educated and given specific feedback about their energy use patterns in order to help them adjust their behavior for energy efficiency. Although already far below the typical home in energy consumption (about 90%), this paper shows how ÉcoTerra could consume even less energy and how similar houses could be designed or upgraded to achieve net zero energy.

Applying A Design Methodology for a Net Zero Energy House to Evaluate Design Processes and Tools
Eurosun 2010 Paper
March 2010 - PDF 0.05MB
EcoTerra is a house near Montreal that combines passive solar features (large windows and integrated thermal mass) and active solar features (a BIPV/T roof and thermal storage system) to achieve near net-zero energy (NZE) [1]. This paper presents and applies a methodology for redesigning the house to achieve net-zero energy. The objectives are: 1) to demonstrate the use of tools of varying degrees of model resolution and 2) address any weaknesses and new useful features in existing tools.

Design Optimisation Methodologies for a Near Net Zero Energy Demonstration Home
Eurosun 2010 Paper
March 2010 - PDF 0.21MB
This paper applies an energy optimization methodology to identify improvements to an existing near net-zero energy house located south of Montreal, Canada. As many of the design performance parameters are strongly coupled, a hybrid evolutionary algorithm was used to ensure full solution space exploration, and harmonized parameter variation. This paper presents a set of ‘lessons learned’ to be applied to the design of future net-zero energy homes.

Design, Optimization, and Modeling Issues of Net-Zero Energy Solar Buildings
Eurosun 2010 Paper
March 2010 - PDF 0.21MB
The design of net-zero energy solar buildings (NZESBs) presents a challenge because there is no established design strategy to systematically reach this goal and many of the available tools have limited applicability for such advanced buildings. This paper reviews current design practice and tools for designing NZESBs through a literature review and a survey. It also summarizes the results of some redesign and optimization case studies of existing NZESBs that Subtask B of the IEA SHC Task 40/ECBCS Annex 52 is performing. The outcome of this study identifies effective strategies for the use of design and optimization tools in establishing near optimal NZESB designs.

Solar 2002: A Belgian Pilot Project for Zero Energy Buildings
Eurosun 2010 Paper
March 2010 - PDF 0.37MB
This paper describes the “Solar 2002” building in Berlaar (Belgium) that was constructed by the Flemish non-profit organization Mondo vzw. The aim of this retrofit of an existing single family dwelling was the creation of an example project, demonstrating the potential of solar energy for the energy needs of buildings in a temperate, rather cloudy climate. This has led to a “Net-Zero Energy” building, that finally supplies more energy to the grid, then it consumes on an annual basis. This paper focuses on the energy-aspect for the building in use. Technical details of the building and the employed renewable energy technologies are given.