Urban-Scale Energy Modeling to Promote Smart Solutions for Sustainable and Resilient Cities

L'abstract è presente nell'allegato / the abstract is in the attachmen

Building energy modeling at neighborhood scale

The urban climate and outdoor air quality of cities that have a positive thermal balance depending on the thermal consumptions of buildings cause an increase of the urban heat island and global warming effects. The aim of this work has been to develop an energy balance using the energy consumption data of the district heating network. The here presented engineering energy model is at a neighborhood scale, and the energy-use results have been obtained from a heat balance of residential buildings, by means of a quasi-steady state method, on a monthly basis. The modeling approach also considers the characteristics of the urban context that may have a significant effect on its energy performance. The model includes a number of urban variables, such as solar exposition and thermal radiation lost to the sky of the built environment. This methodology was applied to thirty-three 1 km × 1 km meshes in the city of Turin, using the monthly energy consumption data of three consecutive heating seasons. The results showed that the model is accurate for old built areas; the average error is 10% for buildings constructed before 1970, while the error reaches 20% for newer buildings. The importance and originality of this study are related to the fact that the energy balance is applied at neighborhood scale and urban parameters are introduced with the support of a GIS tool. The resulting engineering models can be applied as a decision support tool for citizens, public administrations, and policy makers to evaluate the distribution of energy consumptions and the relative GHG emissions to promote a more sustainable urban environment. Future researches will be carried out with the aim of introducing other urban variables into the model, such as the canyon effect and the presence of vegetation

An Urban Energy Atlas and Engineering Model for Resilient Cities

Increasing energy efficiency in buildings is a crucial topic, especially in those EU countries where almost 50% of the final energy consumption is used for space heating and cooling, of which 80% is used for buildings. This study presents a model and a tool that can be used to evaluate energy consumption and to identify retrofitting strategies and renewable energy sources with the aim of reaching energy and climate targets in order to improve energy security, competitiveness and sustainability in a territory. In a previous research, a ‘top-down engineering’ model was applied for a number of 1 km2 districts in the city of Turin (IT) to evaluate the residual potential of buildings that could be connected to the district heating network. In this work, the energy-use model has been improved by considering applications to urban areas of different dimensions, and an urban energy atlas for the Turin building stock has been defined with the support of a Geographical Information System. The model has been validated by comparing the results of an energy balance calculation with energy consumption data of three consecutive heating seasons over an area of about 40 km2 in which 500,000 inhabitants live

Optimization of Costs and Self-Sufficiency for Roof Integrated Photovoltaic Technologies on Residential Buildings

It is common practice, in the production of photovoltaic energy to only use the south-exposed roof surface of a building, in order to achieve the maximum production of solar energy while lowering the costs of the energy and the solar technologies. However, using the south-exposed surface of a roof only allows a small quota of the energy demand to be covered. Roof surfaces oriented in other directions could also be used to better cover the energy load profile. The aim of this work is to investigate the benefits, in terms of costs, self-sufficiency and self-consumption, of roof integrated photovoltaic technologies on residential buildings with different orientations. A cost-optimal analysis has been carried out taking into account the economic incentives for a collective self-consumer configuration. It has emerged, from this analysis, that the better the orientation is, the higher the energy security and the lower the energy costs and those for the installation of photovoltaic technologies. In general, the use of south-facing and north-facing roof surfaces for solar energy production has both economic and energy benefits. The self-sufficiency index can on average be increased by 8.5% through the use of photovoltaic installations in two directions on gable roofs, and the maximum level that can be achieved was on average 41.8, 41.5 and 35.7% for small, medium and large condominiums, respectively. Therefore, it could be convenient to exploit all the potential orientations of photovoltaic panels in cities to improve energy security and to provide significant economic benefits for the residential users

Low-Carbon Strategies for Resilient Cities: A Place-Based Evaluation of Solar Technologies and Green Roofs Potential in Urban Contexts

The use of smart green technologies such as solar panels or green roofs on the top of buildings are identified as low-carbon infrastructure strategies. This work examines the roofs’ potential in a densely built-up context, analyzing the effects of smart green technologies on energy savings and thermal comfort conditions at district scale. The methodology presented can be used to accurately estimate solar energy potential and green roof potential on existing building stock at national, municipal, district and building level, with direct application in energy efficiency policy design. With the support of a place-based approach, the methodology was applied to a district in the city of Turin (Italy). A 3D model was created, some scenarios have been investigated, and priorities of interventions have been established mapping the spatial distribution of different parameters. From the results, it is emerged that there is a significant potential in Turin, and the use of green technologies especially in critical areas with solar technologies can promote a more sustainable development of the city. Solar modules and green roofs have been used alternatively to maximize the benefits. The applicability of these technologies can be integrated in the Municipal Energy-Environmental annex of the Building Regulations of the city of Turin

Space heating models at urban scale for buildings in the city of Turin (Italy)

Today 54 % of the world's population resides in urban areas and in 2050 the projections are for 66 %. Therefore, the issue of city sustainability becomes increasingly important. This paper analyzes city energy sustainability with consideration to the complex built environment, high population densities, anthropogenic activities, energy demands, environmental impacts, as well as limits on both space availability and renewable energy sources. The evaluation considers models of thermal energy consumption for both residential and non-residential buildings based on a GIS tool. The thermal energy-use models consider established statistical methods as well as the introduction of energy-dependent urban-scale variables

Roof-Integrated Green Technologies, Energy Saving and Outdoor Thermal Comfort: Insights from a Case Study in Urban Environment

Green urban infrastructures have a significant impact on urban climate mitigation, on indoor and outdoor thermal comfort and on energy performance of buildings. In this paper, outdoor thermal comfort conditions and energy saving for space heating and cooling were investigated before and after the use of roof-integrated green technologies. Existing urban energy and climate models and tools were applied to an urban area located in a Turin (Italy). CitySim, ENVI-met and SOLWEIG tools and a GIS-based model were used to evaluate the mean radiant temperature and the thermal comfort of outdoor spaces before and after the use of vegetated roofs and green surfaces such as the predicted mean vote (PMV), the physiological equivalent temperature (PET) and the universal thermal climate index (UTCI). A GIS-based engineering model and CitySim tool were used to evaluate the energy saving and energy independence index for space heating and cooling after the use of green roofs and solar technologies. According to the shape and the suitability of rooftop elaborated with GIS tools, some roofs were identified as potential green roofs other as potential solar roofs for installing solar thermal collectors and photovoltaic panels. According to the results it is possible to confirm that the use of green roofs and urban greenery can decrease the mean radiant temperature until about 10℃ during summer season, improving outdoor thermal comfort conditions and energy savings with a reduction of 12% for space cooling energy consumption

GIS-based urban energy modelling and energy efficiency scenarios using the energy performance certificate database

The EU building stock is 97% not energy efficient and the promotion of energy retrofitting strategies is a key way of reducing energy consumptions and greenhouse gas emission. In order to improve the energy performance of buildings, the European Union released the Energy Performance of Buildings and the Energy Efficiency Directives. The certification of the energy performance of a building is a central element of these Directives to monitor and promote energy performance improvements in buildings, with the aim of increasing their energy efficiency level, thereby reducing greenhouse gas emissions. This work evaluates the energy performance of existing residential buildings using the energy performance certificate database and identifies the more effective retrofitting interventions by applying an urban-scale energy model. The novelty of this study is that a new retrofitting database is created to improve the results of a building energy model at urban scale taking into account the real characteristics of the built environment. The here presented GIS-based monthly engineering model is flexible and easily applicable to different contexts, and was used to investigate energy efficiency scenarios by evaluating their effects of city scale. An urban energy atlas was designed for an Italian city, Turin, as a decision-making platform for policy makers and citizens. This energy platform can give information on energy consumption, production and productivity potential, but also on energy retrofitting scenarios. The results of this work show that it is possible to obtain energy savings for space heating of 79,064 MWh/year for the residential buildings connected to the district heating network in the city of Turin; these interventions refer mainly to thermal insulation of buildings envelope with windows replacement and allow a reduction in greenhouse gas emissions of 12,097 tonCO2eq/year

Evaluation of ventilation loads in buildings energy modelling at urban scale

Generally, the models for evaluating the energy performance of buildings have a ventilation thermal load that depends on the type of building and its occupancy rate. The models apply a constant rate of air changes and therefore the ventilation load depends on this value and on the temperature gradient between internal and external environments. In this work, a single zone air flow model is presented to modify monthly the air changes according to the climatic data, the air permeability, shape and orientation of the building and the urban morphology. The results of this work, show how the air change rates vary with the building floor and with the wind direction and velocity. For both case studies, the air changes per hours vary monthly with minimum values in wintertime and with monthly differences of 41%. Of course, if the building is not well exposed and there is no wind, the air infiltrations are not sufficient to ensure good air quality conditions and it will be necessary to open the windows. In these first two case-studies, a very simple single zone evaluation of air flow rate by natural ventilation improved the existing energy performance placebased model. The results of this work encourage the application of this model at district-urban scale, taking into account the characteristics of each single building and its surroundings

How to Improve the Liveability in Cities: The Effect of Urban Morphology and Greening on Outdoor Thermal Comfort

Extensive and intensive green roofs and vegetated walls should be used to improve the livability in cities, especially in densely built-up context, in order to optimize their contribution on energy savings and greenhouse gas emissions, improving thermal comfort conditions and ensuring a greater storm-water runoff. The aim of this study is to evaluate the effect of urban morphology and to quantify the impact of green surfaces and plants on outdoor thermal comfort conditions. The analysis was applied to six neighborhoods in the city of Turin, identified as typical districts with different building geometries, urban contexts and green presence. The outdoor thermal comfort conditions were assessed calculating a set of indicators, such as the predicted mean vote and the physiological equivalent temperature, with the support of ENVI-met tool. Retrofit scenarios were hypothesized, and outdoor thermal comfort conditions were investigated before and after the installation of green roofs and vegetated areas. The result allowed to understand how thermal comfort vary, considering the building geometry, urban morphology, and green areas in different zones of the city of Turin. By analyzing neighborhoods, it is possible to identify the optimal built environment that ensure better thermal comfort conditions. These models and tools could support urban planners in defining the best measures to improve the liveability and quality in the built environment considering local constraints and the real characteristics of the territory or in designing new neighborhoods