Photovolcaic systems energy potential analysis ENERBUILD

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This energy potential analysis was conducted within the ENERBUILD project. An article about the biomass energy potential analysis has been published in the publication Producing energy on buildings in the Alpine Space - synthesis.

Solar technology is one of the natural choices for on-site generation as the energy coming from the sun is captured by solar panels and transformed into heating or, by means of photovoltaic (PV) systems, into electricity. The identification of suitable surfaces in urban areas plays an important role for the private investor as well as the public local community. One of the most influencing factors is a correct estimation of the incoming solar radiation. This study aimed at an optimal exploitation of the advantages of solar panel systems.

Definition of photovoltaic systems

Photovoltaics (PV) is a method of generating electrical power by converting solar radiation into direct current electricity using semiconductors that exhibit the photovoltaic effect. Photovoltaic power generation employs solar panels composed of a number of solar cells containing a photovoltaic material. Materials presently used for photovoltaics include monocrystalline silicon, polycrystalline silicon, amorphous silicon, cadmium telluride, and copper indium gallium selenide/sulfide. Due to the increase demand for renewable energy sources, the manufacturing of solar cells and photovoltaic arrays has advanced considerably in recent years. Solar photovoltaics have long been argued to be a sustainable energy source.[1] By the end of 2011, a total of 67.4 GW had been installed, sufficient to generate 85 TWh/year.[2]And by end of 2012, the 100GW installed capacity milestone was achieved. [3]Solar photovoltaics is now, after hydro and wind power, the third most important renewable energy source in terms of globally installed capacity. More than 100 countries use solar PV. Installations may be ground-mounted (and sometimes integrated with farming and grazing) or built into the roof or walls of a building (either building-integrated photovoltaics or simply rooftop).[1]

Description of methodology for PV

It is crucial to consider shadowing effects due to topography (presence of hills/mountains) or shadows cast by nearby buildings, vegetation or other objects found in urban areas. Due to the complexity of this task, quality of solar radiation predictive models, as well as quality and quantity of their input data are pivotal to optimally exploit the advantages of solar panel systems.

The used methodology tries to combine and unify in general PVGIS1,2, and LiDAR3 approaches and to establish a so-called „solar cadastre” for the PV potential of the roofs in a given urban area. Four steps are identified.

Modelling of the buildings’ roofs - to compute and quantify the incoming solar radiation, a 3D model of the town is required which represents the geometric properties of each building and its position inside the city and – if possible – in the surrounding environment.

Computation of the solar potential is based on the Astronomic Calculations, which consider the incoming radiation according to the sun position with respect to latitude, longitude and altitude.

Radiation distribution for the buildings is based on the calculations of clear sky irradiance through Geographic Information System (GIS) instruments by considering topographical and geometrical effects. A radiation transfer model (RTM) to compute the spectral components is used. The RTM receives inputs from both ground based instruments and from satellite data.

The calculation of the roof PV potential is the last step. The most common approach is to calculate the annual solar potential for the total roof area, and then PV potential is obtained as a pro-duct of this value and the efficiency of the corresponding PV module technology.

Illustration with results

Modelling of the building's roofs

Starting from LiDAR data and using GPS (Global Positioning System) and INS (Inertial Navigation System) instrumentation for georeferencing purposes, a DTM (Digital Terrain Model) is obtained, up to one meter resolution. By means of further filtering operations, only the building roof’s geometry can be obtained. The case of Bressanone, Italy, is shown in figure 1a-c.

In addition, combination and integration of the data from the LiDAR-based DTM with cadastral data as well as models obtained from automatic and manual image matching could be made. This has been tested in Mattarello (Trento), Italy. In this case, a sufficiently large DTM at 1 m resolution is used to model the surrounding cast-shadowing mountains, while for the roofs de-tailed models from photogrammetry are created and integrated, with a resolution up to 25 cm. Figure 2 shows an example of the different models obtained from different modelling strategies for a group of buildings in Mattarello.

Computation of the solar potential

In the case of mountain area an important parameter is also the far shading produced by the surrounding mountains (horizon line). The other parameter taken into consideration is the near shading produced by close objects typical for an urban area (trees, buildings, etc.). In order to account the effect of cloudiness a monthly correction to the cumulative radiation obtained through on-site measurements (pyranometers, average on long term period, decades) is done. Average value for example for all roofs in Bressanone (various inclinations) is ~1.100kWh/m2.

Radiation distribution for the buildings

Radiation distribution for the buildings

The obtained result can be subdivided into main annual radiation levels. An example for Bressanone is presented in the table 1 below. According to these levels, the description of the roof can be classified as very suitable (red), suitable (orange), medium suitable (yellow) and non-suitable without colour.

Calculation of the roof PV potential

The calculation is made for four different PV module technologies. One is for the c-Si high efficient technology; the others are for the standard crystalline Si and the following thin films CdTe, CIGS and a-Si PV modules. Results presented on the figure 3 show the calculated PV roof potential for the city Bressanone, Italy.


Application to other regions, capitalization

The above described methodology is a general approach. It is applicable for different locations and regions. The main important databases here are the cadastre map for a given municipality, LiDAR, radiation and PV data.

Contacts, publications, disseminations, references

In order to disseminate the results a workshop „Solar Plants on Buildings: Energy Potential Assessment and Monitoring” has been organized in Bolzano, Italy the 17th October 2011

Acknowledgment – The result presented for the solar cadastre map for the city Bressanone has been founded by the European Regional Development Found (ERDF) under the project PV-Initiative N 2-1a-97.


EURAC research center

Viale Druso 1

I-39100 Bolzano

Miglena Nikolaeva-Dimitrova

Coordinator of research group Photovoltaics

Institute for Renewable Energy

+39 0471 055 055


Riccardo De Filippi

Mpba (Predictive Models for Biomedicine & Environment)


  1. Wikipedia Article

2. Synthesis on producing energy on buildings in the Alpine Space (2012)