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FIORELLA BELLORA Universidad de la República, Uruguay
MICHELE DE CARLI
Università degli Studi di Padova
abstract
1. Introduction To date, real estate and the construction sector are responsible for 40% of global CO2 emissions. Over the next 20 years built areas will increase by 50%, and that will have a significant impact on the resolution of the environmental crisis. Therefore, the design of the built environment is essential to approach sustainability and architects must reformulate our traditional techniques, where the project goes linearly from the architect to the engineer, for an integrated process, where all the members of the design team work collaboratively from the primary phase. The conventional techniques have been abandoned for a new concept where energy is integrated to architecture. Sanford Kwinter (2001) calls this new paradigm thermodynamic architecture. In addition to that, Iñaki Abalos (2008) says that architects must design buildings as living organisms, and solve their proposals with permanent energy exchanges with its environment. To move towards this new paradigm it is necessary to abandon established traditional practices in favour of new combinations concerning an integrated design project. Therefore, we have to redefine the relationship between architecture and engineering as not only technological, but genetic and turn it into a new operative dimension, a new territory where architecture, landscape and environmental techniques are combined, a new approach for projective practices, sharing and expanding our disciplinary area looking forward to an hybrid aesthetic where massive energy building systems come together with high technology.
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This study aims to contribute on the interaction between energy and the architecture design process in order to accomplish a Nearly Zero Energy Building (NZEB). The design of the built environment, from a house to a city, is transcendental to re-conduce the inefficient models of our societies towards a new direction to sustainability. We must search actively for mechanisms that allow the built environment to make a positive contribution in sustainability matters. Therefore, choices on design and the incorporation of renewable energies become crucial in reducing the environmental impact of buildings. The issue of sustainability has transformed the design processes of architects and engineers, turning them into a bioclimatic position interacting with other disciplines. There has been a shift from the “mechanical” to the “energetic” paradigm. The modern theory of modulation based on serialization and industrial materiality has been abandoned for a new concept where energy is integrated to architecture. Sanford Kwinter (2001) calls this new paradigm thermodynamic architecture. Architects must change our design techniques towards integrated design by combining traditional construction with emerging technologies to restore a deep connection with the climate, the culture and the natural landscape of the site of each intervention. Therefore, we need to have a holistic approach between architecture, energy and technology. In this study, it is proposed to analyse the integration between energy and architecture from the first stages of the design process, that is to say energy efficiency and renewable energy to accomplish a NZEB. A Building Performance Simulation Software (TRNSYS) is going to assist the decision-making. The case study is a University Technical Institute in Colonia, Uruguay.
ENVIRONMENTAL PERFORMANCES & REACTIVE MATTERS
an integrated design process
Strategic field: Planning/ Designing Topic: Fire/ Eco-systems
ENERGY ON ARCHITECTURE:
We need to have a holistic approach between architecture, energy and technology from the first stages of the design process. The possibility of counting with Building Performance Simulation (BPS) tools that can simulate dynamic performances of integrated solutions offers a wide range of optimization and improves the architectural and technological choices at the primary phase as well as at the final verification.
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Is usual to use BPS tools to support the design of NZEBs during later design stages. Nevertheless this phase is when many detailed decisions have already been taken. For example, building orientation and an appropriate geometrical configuration are very important decisions for energy efficiency, and are taken in the primary phase. Nowadays, there is a growing awareness to integrate BPS tools during early design phases (Attia et al. 2011). The potential impact of the building simulation is more important when it is used from the initial phase of the project. Therefore, it is proposed to study the interaction between architecture design process and energy (energy efficiency and renewable energy) to accomplish a Zero Energy Building where passive energy systems are combined with active systems and technology. The case study is a University Technical Institute in Colonia, Uruguay. A dynamic building performance simulation software (TRNSYS) will be used to analyse the energy performance and to assist in the decisions stages from the early phases of the design process.
2. Objectives and conceptual frame 2.1 Objectives The general objective is to analyse the integration between energy and architecture from early stages of a design process. In detail, the design of a Nearly Zero Energy Building with low energy consumption is developed: the energy is self-produced with renewable sources, assisted with a dynamic building performance simulation software (TRNSYS) in order to study the energy performance of the building. 2.2 Bioclimatic Design: Analysing the climate of the site as an input for the design process Nowadays the worldwide-publicised concept of sustainability is successful when a building efficiently uses the local climate conditions and has the capacity to guarantee optimal comfort conditions for the occupants.
Within the architectural design phases, diverse objectives must be taken into consideration and balanced. Just to mention some of them: aesthetic, economy, ambient quality, energy efficiency, and low environmental impact. Many architects think that the energy aspects have to be taken into consideration with an engineer or technician when the project is at the last stages, but in those cases, high costs are associated and the result consist of buildings without positive relations with the site and the climate where they are located. The achievement of sustainability in a building is accomplished when understanding the climate conditions of the site, taking advantage of the benefits of natural resources with the aim to promote interior conditions to ensure hygrothermal comfort for the occupants, and minimizing the energy use for heating and cooling. For this, it is necessary to know the climate where we are working, to identify the characteristics to draw strength from, and the ones to reduce the negative impact on the building; this means that we have to read the ambient conditions of the environment and to embody them to accomplish the occupant’s comfort. 2.3 Zero Energy Buildings A Zero Energy Building (ZEB) produces enough renewable energy to meet its own annual energy consumption requirements; thereby it reduces the use of fossil energy in the building sector. Furthermore, ZEBs take measures to reduce the energy consumption. There are a number of long-term advantages on moving towards a ZEB, including lower environmental impacts, lower operation and maintenance costs, better resiliency to power outages, and improved energy security. Nowadays, definitions differ from region to region and from organization to organization, leading to confusion and uncertainty around what constitutes a ZEB. Two definitions are presented; one from U.S Department of Energy and the other from the Directive 2010/31/EU of the European Parliament. 1. Definition from U.S Department of Energy (2015). An energy-efficient building where, on a source energy basis, the actual annual delivered energy is less than or equal to the on-site renewable exported energy. 2. Definition from Directive 2010/31/EU of the European Parliament (2010). Nearly zero-energy building’ means a building that has a very high-energy performance, as determined in accordance with Annex I. The nearly zero or very low
ENVIRONMENTAL PERFORMANCES & REACTIVE MATTERS
amount of energy required should be covered to a very significant extent by energy from renewable sources, including energy from renewable sources produced on-site or nearby. Good examples of constructed NZEB, shows that their design process is based on multidisciplinary teams that effectively integrates, early on, all aspects of building design, energy efficiency and environmental impact while improving the comfort of the buildings occupants. There is a general agreement that NZEB design can most easily be achieved through an integrated design process (Trebilcock, 2011).
3. Methods The Methodology is presented in the frame of an architectural design process. This is a very complex process, which involves the synergy of two itineraries: an intuitive process based on the subjectivity of the architect and an analytic process in which contextual data is analysed (Trebilcock 2011). However, we need to have a holistic approach when considering all the simultaneous
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Image 1 | Methodology
dynamic processes, their relationships and implications. In this study, the analytic process is based firstly on a bioclimatic diagnosis taking into consideration the climatic conditions and the bioclimatic strategies suggested on the Givoni psychometric chart (1969). Afterwards, but still in the first phase of the design process, it is used TRNSYS (Transient System simulation Tool) as a BPS software to simulate the energy performance and assist the decision stages. Methodology components: A. Input - Fixed parameters: there are fixed parameters that cannot be modified such as the site, the climate, the social and economical context, and the program. We can call them datascape since this is a scape of information that has to be considered in the project. - Variables: in the design process the architect has some variables, or decisions which can be chosen or modified as the project moves on. - Architectural concept: last but not least, the architectural concept, the driving force that will be present during the whole process.
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Image 1 | Givoni Psychometric Chart (1969) for Colonia, Uruguay Image source: Picción et al. 2008
B. Analysis In the first stage of the analysis, it is used the Givoni Psychometric Chart (1969) to establish a bioclimatic diagnosis and to determine generic design strategies to accomplish internal comfort. Afterwards, a model in TRNSYS has been carried out. TRNSYS is a simulation software used in the fields of renewable energy engineering and building simulation for passive, as well as active solar design. This software simulates the energy performance of the building to obtain quantitative information and assist the decision stages from the primary design phase and continue during the whole process with verifications and optimization of the variables to improve the energy performance. C. Output During the design itinerary between quantitative data and qualitative decisions, and from the interpretation of results at the output, a new set of input is hypothesised and the quantitative definitions of the variables are redefined to improve the energetic performance. This cyclic process is done several times aiming to get to an Efficient Energy performance.
4. Bioclimatic diagnosis In the primary phase of the analysis, it is used Givoni Psychometric Chart (1969) to determine generic design strategies to accomplish hygrothermal comfort conditions. The Givoni Psychometric Chart for Colonia, Uruguay (Image 2) represents the climate conditions per hour of the reference typical year. Every point of the chart defines particular external atmospheric conditions given by ambient temperature and humidity conditions. Therefore, it is obtained the percentage of hours that each of these strategies apply to the main periods of the year (summer and winter), and it is detected the highest incidence strategies. This is a method that allows the designer to quickly evaluate which will be the principals design decisions that should be adopted to reach interior comfort conditions in a particular climatic situation. The quantitative description of the Psychometric chart for Colonia (Table 1) shows the percentage of the year in each zone. The results show that 29.2% of the year, the occupants feel comfort; while the remaining 70.8% of the time, the occupants are under discomfort. From these data, it is conclude that the most
From the analysis of the psychometric chart and the energy performance simulation, the bioclimatic strategies chosen to achieve a Near Zero Energy Buildings are:
The bioclimatic strategies are complemented with active strategies through the incorporation of renewable energy: - Photovoltaic panels - Wind Turbines Bioclimatic Strategies: - Form, Orientation and Passive Solar Heating The building proposal consists of a long narrow floor plan shaped by parallel wood gantries, with their larger facades towards north and south orientation. This linear and narrow characteristics help maximize cross ventilation. Classrooms and laboratories are arranged facing south to receive diffuse sunlight, meanwhile hallways facing north, are conceived as galleries with large glazed surface to take advantage of passive solar heating. In winter, this gallery takes advantage of the solar gains, while in summer its glazed area can be 100% opened to avoid overheating and prevent greenhouse effect. This gallery is based on the selective transparency of the glass, transforming itself into a sun trap, because it allows almost the complete entrance of the incident radiation in short wave, but does not allow the way out of the long wave radiation emitted by walls, floor, and other surfaces in the interior. Complementing the strategy of passive solar heating, convective heat transfer is used. This strategy is based on the physical principle of actual
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5. Architectural proposal The aim of the architectural design proposal for this project is to develop a low-impact building that blends seamlessly into the landscape, maximizing the users well being with low consumed energy, through the interaction between design and technology. The project spirit is to establish a strong relationship between sustainable practices and environmental awareness; concepts that are not limited to zero energy measures. The location in the border of the city imposed a natural connection between the land and the building. This results in a topographic architecture, an architecture that navigates the site and respects the natural levels, linking spaces, while the parallel wood gantries define the geometry and allows transversal links as well as future growth.
- Form - Orientation - Passive Solar Heating - Thermal transmittance - Ventilation - Glazing: Area, type and conformation - Solar Sun Shading
ENVIRONMENTAL PERFORMANCES & REACTIVE MATTERS
important strategies for arriving to the comfort zone are: high thermal mass and passive solar heating. The first one has an influence of 30.4% and the second one 19.5%. Furthermore, it is needed to use sun shading to avoid overheating. Therefore, in this location the use of insulated thermal mass is an effective strategy to help achieving required levels of comfort. In the hot period, this strategy must be associated with two main ones: shading and natural ventilation. In the cold period, the isolated thermal mass must be complemented by strategies of passive solar heating and artificial warming. Shading is also required.
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Image 3 | Architectural proposal and bioclimatic strategies
Image 4 | Ground Floor and Facades tegies
- Thermal Transmittance (U):
Natural ventilation is a passive strategy for cooling and for providing thermal comfort for the occupants. Besides it is very important since it allows air renovation and assures air quality.
- Glazing area, type and conformation: The glazing area is responsible for the greater solar gains, but it is also responsible for the most important thermal losses. Therefore, the envelope was appropriately designed in order to reach the balance point between natural lighting requirements, solar gains, and thermal losses, among other decisions, for example aesthetics. For North Facades, it is designed the biggest glazing area of the building, close to 90%, to gain as much solar radiation as possible. This façade is conceived as a close gallery in winter and as an open space in summer where students can meet. Classrooms and laboratories are disposed facing South to receive natural diffuse solar lighting. For this façade, it was decided a balanced point for the glazing area close to 40% of the façade area, in order to maximize natural lighting. In this line of thinking, a doubleglazing with air chamber and low emissivity has been chosen. - Solar Sun shading: The Gallery area in the North’s side works as a sunscreen for direct radiation into the classrooms and Laboratories. Mobile Sunshades are arranged for the Laboratories towards Southwest for the afternoon hours. Renewable Energies: - Photovoltaic Panels In reference to the incorporation of photovoltaic panels to the building, the roof North’s slope is 35° as this is the most efficient slope for solar energy accumulation since data obtained during the energy production simulation with TRNSYS. It was simulated the energy production of photovoltaic panels with different slopes facing north, aiming to conclude which one was the most efficient slope. The results showed that the most efficient slope when the University Institute is open (from March to December) is 35°. The production of 165 Photovoltaic panels in the period March to December is 40.192 kWh; meanwhile the annual production is 49.823 kWh. After an evaluation between different Photovoltaic panels, it was
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The U-Value is an important factor in building design. It represents the performance of the envelope. This refers to how well an element conducts heat from one side to the other. The envelope is one of the main elements in the regulation and behaviour of thermal energy in the interior. Therefore, a low thermal transmittance of the enclosure provides a high thermal insulation. After an evaluation between different materials for thermal insulation, it was selected composite wood wool (Celenit), since it is a natural material, environmentally friendly and has certifications and numerous benefits due to its low thermal transmittance. The results of the U-value for the envelopes are 0.25 W/m2K for the exterior wall; 0.24 W/m2K for interior walls and 0.23 W/m2K for the horizontal enclosure. These results present a superior U-value for enclosures in Uruguay, as the compulsory minimum required is 0.85 W/m2K. - Ventilation:
Regarding natural ventilation, it is proposed cross ventilation and chimney effect. In addition the roof is ventilated to prevent overheating, as the main gains are over the horizontal surfaces.
ENVIRONMENTAL PERFORMANCES & REACTIVE MATTERS
displacement of hot and cold parts of a body due to the different density of proximal portions of a given fluid. Therefore the gallery facing north gains heat, which goes up and is transferred through wall openings to the classrooms zone.
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decided to use Polycrystalline Photovoltaic Panel Panasonic HIT VBHN245SJ25.
amount corresponds to the 38% of the estimated consumed electric energy of the building.
Wind Turbines
- Heat Pump
For the wind energy production, it was decided to use Leaf Turbines1 due to their high aerodynamic efficiency, its innovative design, and because they are presented as an economical solution. These wind turbines are the result of a project created by a group of engineers from University of Padua. They are disposed facing the most frequent winds, with an adequate mutual distance as well as from the building in order to avoid acoustic disturbance.
A Heat Pump was chosen in order to reach thermal comfort conditions. From the results obtained in TRNSYS it was decided to use an air to water Heat Pump of 200 kW that covers the year requirements. The electricity to feed this heat pump is one-third from the primary energy obtained from the air temperature. This electric energy is going to be produced by the photovoltaic panels and wind turbines mentioned above. The quantity is enough to feed the building for the whole year. This air to water heat pump transfers the heat from the outside air to the ambient using water as the exchange fluid. The reversible units also provide cooling by absorbing the heat from the inside and releasing it to the outside, therefore a single unit answers all the requirements of the building
It was simulated the energy production of wind turbines, and the results thrown that the annual production of 7 wind turbines is 39.370 kWh, meanwhile the production from March to December (during the academic year) is 30.477kWh. This
6. Results Energy performance As a result of the energy performance simulation with TRSNSYS software, the annual energy consumption of the building (2500m2) in a year is 80.023 kWh. Meanwhile the annual energy production with renewable sources is 70670 kWh, which means that it is, produced the 88.3% of the annual consumed energy. Image 5 | LEAF Turbine
ENVIRONMENTAL PERFORMANCES & REACTIVE MATTERS
Image 6 | TRNSYS graphic: Temperatures, Power and Energy
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Considering more detailed results (Table 4), the annual consumption taking into account equipment, lighting, heating and cooling is 80.000 kWh. Meanwhile, the consumed energy per square meter per year is 36.2 kWh/m2year. With reference to the production of renewable energy (Table 5), as the aim was a to approach a near zero energy building, in other words, to produce enough renewable energy to nearly meet its own annual energy production requirements, the results throw that the photovoltaic energy produced, during the academic year, is 40.192,59 kWh, which represents the 50.2% of the building
annual consumption. In addition, the result on Wind Turbines production from March to December is 30.476,6 kWh, which represents a 38.1% of the building annual consumption. Consequently the renewable energy production embodies the 88.3% of the annual energy consumption affirming that this building consumes almost zero energy.
Conclusions This paper has analysed a growing interest to accomplish the integration of energy aspects in the design process to achieve good standards of sustainability. Transforming our traditional design
Note Bibliografia
practices searching for the optimization of energy efficiency and the reduction of energy demand is a responsibility for architects and engineers. Nowadays there is an installed awareness to introduce BPS tools during the design process. Moreover using them from the initial phases greatly optimizes the project and this is clearly enriched when a collaboratively and interdisciplinary team is involved. It is concluded that the methodology chosen was satisfactory to assist decisions in order to reach a Nearly Zero Energy Building. The use of the psychometric chart, and BPS tools from the initial phases significantly optimize the project. The BPS tools not only assisted the verifications and more detailed decisions during the advanced phases of the project, but also assisted macro decisions in the initial phase, as orientation and geometrical configurations with fast models and graphics to quickly understand and evaluate the best solution to each question.
1
LEAF turbine. Project created by a group of Engineers from University of Padua: Gabriele Bedon, Stefano De Betta, Andrea Dal Monte and Enrico Antonini. Email: gabriele.bedon@gmail.com; stefano. debetta@gmail.com
Ábalos I. (2008), La belleza termodinámica, Available on mansilla-tuñon webpage, http://www.mansilla-tunon. com/circo/epoca7/pdf/2009_157.pdf (Accessed 15 Agost 2016) ASHRAE Standard 55 (2004), Thermal Environmental Conditions for Human Occupancy, American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc, Atlanta Attia S., De Herde A. (2011), “Design Decision Tool for Zero Energy Buildings” in PLEA 2011: Architecture & Sustainable Development: Conference Proceedings, vol.2, pp. 77-81 Givoni B. (1976), Man, Climate and Architecture, Applied Science Pub, London
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Gonzalo G. (2003), Manual de Arquitectura Bioclimática, Nobuko, Buenos Aires Kwinter S. (2001) Architectures of time. Towards a theory of the event in modernist culture, The MIT Press, London Olgyay V. (1973), Design with climate – bioclimatic approach to architectural regionalism, Princeton University Press, New Jersey Pezzi C. (2014), Un Vitruvio Ecológico. Principios y prácticas del Proyecto arquitectónico Sostenible, Gustavo Gili, Barcelona Picción A., Milicua S. (2005), Tratamiento de datos climáticos de localidades de Uruguay para evaluación térmica y energética de proyectos y edificios, UDELAR, Montevideo Szokolay S. (2004), Introduction to Architectural Science: The basis of sustainable design, Architectectural Press, Burlignton The European Parliament and of the Council (2010), Directive 2010/31/EU on the Energy Performance of Buildings, Available on www.eur-lex.europa. eu/ website, http://eur-lex.europa.eu/LexUriServ/ LexUriServ.do?uri=OJ:L:2010:153:0013:0035:EN:PDF (Accessed 15 Agost 2016)
Acknowledgments
Trebilcock M. (2009), “Proceso de Diseño Integrado: nuevos paradigmas en arquitectura sustentable” in arquiteturarevista, no. 2 vol. 5, pp. 65-75
This research was done at University of Padua in the frame of a Coimbra Group Scholarship (http:// www.coimbra-group.eu/) with the tutoring of the Professor Michele De Carli.
U. S. Department of Energy (2015), A common definition from zero energy buildings, Available on U. S Department of Energy website, http://energy.gov/ eere/buildings/downloads/common-definition-zeroenergy-buildings, (Accessed 15 Agost 2016)