Towards solar urban planning: A new step for better energy performance

Towards solar urban planning: A new step for better energy performance

Miguel Amado a*, Francesca Poggi b

a Engineering Department, FCT UNL, Campus da Caparica, 2829-516, Portugal

b GEOTPU, FCT UNL, Campus da Caparica, 2829-516,Portugal

Energy Procedia 30 ( 2012 ) 1261 – 1273

Keywords: Solar analysis and parametric urban design; photovoltaic systems; sustainable urban planning; ZEB

Purpose

The aim of this paper is to explore the concept of Solar Urban Planning with the goal of developing an operative methodology to achieve the best conditions towards Zero Energy Building (ZEB).

A “new step” that determines the solar potential of an urban area, implements a model connected to the needs of buildings and their capacity to produce energy from solar resource integrating solar analysis with parametric urban design, represents a useful tool to be added into the conception phase of urban planning.

Definition of term 

• Solar urban design is a “new phase” of sustainable urban planning, a phase that has wide horizons of development and could provide new solutions to the worlds energy problem by reducing its consumption and improves the performance of future buildings. 

• Solar urban planning is a current topic stemmed from the inadequacy of the traditional urban planning process regarding the use of solar potential: a determining factor to reach smart energy cities formed by zero energy buildings.

Methodology

•A case study in Portugal

 Plan the correct orientation and form of new buildings to guarantee the optimal efficiency of  photovoltaic roof and façade systems and

 Calculate their solar energy production

•This data is integrated utilizing GIS, which can integrate both qualitative and quantitative data.

•It is a method that guarantees the effectiveness and prosecution of the sustainability principles and accurately predicts the solar energy production in urban areas subjected of renewal or regeneration processes.

This methodology is based on determining the solar potential in existing urban area and comparing it to the possible gains if the area is transformed using actions from the sustainable urban planning process.

This new approach results from relating economic, social, and environmental and governance factors with solar energy use.

Case study

Step 1 : Intervention program and energy model definition

• The selected urban area of approximately 1.88. In 2006, the precinct had been affected by a municipal renewal. 

•The intervention program: addressing the local authority policies and sustainable factors such as economic development, environmental protection and social needs directly related to the given urban area.

• According to the local energy available resources the solar potential has been considered and the methodology develops a new approach to focus on this factor in each its operative steps.

Step 2 : Site analysis and solar potential estimation

Step 2.1: Site analysis

In order to apply a sustainable planning approach, data on the economic, environmental, social and urban factors that characterize the given area have to be rigorously collected.

By means of Arcgis®, a complete data framework of the site has been collected; the most relevant information on the built environment is resumed in Tab.1.

Results:

• Not guarantee suitable parcel size to satisfy activities and population needs.• Inadequate relationships between:　　The height and distance - daylight, ventilation and solar access need　　The quality of the public space and activities  - sufficient for the predicted demographic trend and future population demands


Step 2.2: Solar potential estimation of the existing roof areas

2.2.1. Energy analysis

The energy analysis has to be conducted to evaluate what is the better photovoltaic system that could

be utilized in the presents and future buildings according to the statistic date about price electricity and its annual consumption by each sector (tab.2)

2.2.2. Solar radiation

To gather solar radiation data it has been used ArcGis® combining local geographic information and topographical features.

The obtained maps (fig.3, tab.3) describe the annual solar radiation features on the ground and are a useful tool to provide the best location for buildings and open spaces within the case study area.

2.2.3. Existing roof types classification identifying

By mean of satellite images and ArcGIS® has been conducted a roof types classification identifying 34 with flat solution and 59 pitched (fig.4). The graph in fig.4 shows that on a total of 93 existing rooftops corresponding to a gross area of 7137m2, the more frequent size surface is between 50m2 to 100m2.

Results: the final minimum size value of 42m² has been considered as reduction factor during the analysis of the existing buildings.

2.2.4. Shaded analysis

The percentage shaded analysis has been simulated by mean of Ecotect® and an incidence of shadows by other building greater than of 30% reducing the total sunlight hours from 9 to a number inferior of 5 has been considered as another reduction factor (fig.5).

2.2.5. Calculate the predicted annual energy yield for PV systems

it has been adopted the following equation:

After all the described considerations the effective net area on the existing rooftops and the related values of solar radiation incident have been estimated and resumed in the table 4.

Step 3: Plan design and solar design

a. Plan design: new urban layout has been deal with population needs, related functional activities, public spaces and smart linkage for a more ecologically responsive mobility system obtaining a more functional and balanced global urban model.

b. Solar design: all new buildings have been designed:

flat roofs with size areas greater than 42m2

New urban forms to guarantee solar access and minimize the shading

c. Estimation of solar energy production on the new roof and façade areas

This estimation process applies the same approach used to evaluate the given urban area adding some　further criteria characterizing the building facades and that are indispensable to obtain the solar energy estimation.

Results

Tables 6 and 7 show that the new buildings roof and façade areas constitute a great potentiality to gather solar radiation and produce the electricity which can contribute for satisfying their own cooling and heating needs.

Conclusions

• The ZEB target is achieved if the urban design implements efficient solar orientation to future buildings and public areas in the way to increase a better solar access on building facades.

• The obtained results confirm that by applying the proposed methodology to urban interventions is possible achieve better energy performance in urban context and better conditions to ZEB goal.

• The methodology Solar Urban Planning is possible to improve urban areas, accommodate more people and areas and at the same time guarantee a better energy performance leading to the effective Zero Energy Precinct.