Tomas Cebecauer

Geographic Aspects of Photovoltaics in Europe: Contribution of the PVGIS Website

The photovoltaic geographic information system (PVGIS) is a web-based knowledge distribution system that provides climate data and tools needed for the performance assessment of photovoltaic (PV) technology in Europe. Geodatabases and simulation models are interlinked with the web interface, thus providing easy-to-use access to users. Interactive maps play an important role in understanding the geographic dependency of the performance of the PV technology. While our previous papers dealt with technical aspects of development and data analysis, here we review lessons learned from the feedback of users. A description of the underlying data and web tools is followed by the analysis of two points that are often discussed when comparing PVGIS with alternative systems: 1) the uncertainty of solar radiation estimates and 2) PV yield predictions. For systems based on the ground observations, such as PVGIS, higher uncertainty of estimates can be expected in mountains, close to the coastline, and in regions with lower density of the meteorological stations. A comparison of PVGIS with other simulation software may show regional differences, which typically reflect: 1) the use of underlying databases that are based on diverse input data (ground-measured or satellite with various observation periods) and that vary in spatial and time resolutions, and 2) the use of different simulation concepts. A cross comparison of the existing systems is needed to identify advantages and limits of their use in solar energy projects.

Inventory of major landscape changes in the Czech Republic, Hungary, Romania and Slovak Republic 1970s – 1990s

Abstract One of the most important achievements in 1998–1999 of Phare Topic Link on Land Cover has been the development and practical application of a methodological approach to landscape change identification and analysis in the territories of four Phare countries (the Czech Republic, Hungary, Romania, and the Slovak Republic). The changes were identified on a national level from Landsat TM and MSS satellite images by application of the CORINE Land Cover databases for two time horizons (the late 1970s and early 1990s) at the second hierarchic level. Based on identified causality, the landscape changes were grouped into 7 types: intensification of agriculture, extensification of agriculture, urbanisation-industrialisation, enlargement (exhaustion) of natural resources, afforestation, deforestation and other anthropogenic causes. The results of the groupings are presented in the form of contingency tables and maps showing the spatial distribution of the changes. From the point of view of total extent, forest landscape changed the most in the Czech Republic. This change represents a reduction of forest by 167,702 ha and an enlargement of transitional woodland-scrub by about 26,339 ha. In Hungary the most pronounced changes were decrease of forests by 66,622 ha and decrease of arable land, orchards and vineyards by 21,529 ha. The most remarkable changes identified in Romania were decrease of arable land, forests and wetlands by 366,817 ha, 285,887 ha, and 59,967 ha, respectively, as well as enlargement of areas of complex cultivation pattern by almost 347,220 ha. The most pronounced changes in Slovakia were represented by diminution of forest by 94,935 ha and that of heterogeneous agricultural areas by 18,451 ha; enlargement of transitional woodland-scrub areas and urbanised area were about 13,107 ha and 14,990 ha, respectively.

Chapter 2 – Semi-Empirical Satellite Models

This chapter discusses the basic principles of solar-irradiance modeling based on the use of input data from geostationary satellites and atmospheric models. Two operational approaches (SUNY/SolarAnywhere and SolarGIS), which are based on the use of semi-empirical models, are presented in the context of recent developments.

Optimisation of Interpolation Parameters Using Cross-validation

Quality of data used in the GIS-support tools is a critical issue, as the decisions that affect locations or areas are to be made effectively, in time and with adequate accuracy. At present, a number of European Union and national policy strategies rely on the use of quality digital elevation model (DEM) data. The accuracy, smoothness and representativeness are properties of DEM determining outputs of the support systems that are designed for assessment of renewable energy resources, flood forecasting, disaster and security management. Similarly, suitability analysis, calculating of environmental indicators and water quality monitoring within the catchments are based on the use of DEM and the decisions taken have financial and legal implications. Thus, a prerequisite for full exploitation of the potential of DEMs is to make them available for the community at sufficient accuracy and detail for a variety of applications.

Site-adaptation of satellite-based DNI and GHI time series: Overview and SolarGIS approach

Site adaptation is an approach of reducing uncertainty in the satellite-based longterm estimates of solar radiation by combining them with short-term high-accuracy measurements at a project site. We inventory the existing approaches and introduce the SolarGIS method that is optimized for providing bankable data for energy simulation in Concentrating Solar Power. We also indicate the achievable uncertainty of SolarGIS model outputs based on site-adaptation of projects executed in various geographical conditions.

Challenges to Realise 1% Electricity from Photovoltaic Solar Systems in the European Union by 2020

Accumulated installations of photovoltaic solar systems in the European Union have reached almost 2 GW at the end of 2005. The generated electricity was in the range of 2 to 2.5 TWh or merely 0.8% of the 3000 TWh consumed in 2005. Standard models predict an average yearly growth of electricity consumption in Europe of 1.3% until 2020. The European Photovoltaic Industry Association Roadmap aims for a total installed capacity of 41 GW photovoltaic solar systems or an electricity generation in the range of 49 TWh or 1.1%. To reach the 41 GW in 2020 a continuous annual growth of 30% for 15 years is necessary. If we assume, that 50% of this 41 GW will be installed in two Solar I regions in Europe (Southern Italy and Southern Spain), this can correspond to 50% or more in those geographic areas at certain times of the day and distribution problems of this electricity are not addressed yet

Worldwide multi-model intercomparison of clear-sky solar irradiance predictions

Accurate modeling of solar radiation in the absence of clouds is highly important because solar power production peaks during cloud-free situations. The conventional validation approach of clear-sky solar radiation models relies on the comparison between model predictions and ground observations. Therefore, this approach is limited to locations with availability of high-quality ground observations, which are scarce worldwide. As a consequence, many areas of in-terest for, e.g., solar energy development, still remain sub-validated. Here, a worldwide inter-comparison of the global horizontal irradiance (GHI) and direct normal irradiance (DNI) calculated by a number of appropriate clear-sky solar ra-diation models is proposed, without direct intervention of any weather or solar radiation ground-based observations. The model inputs are all gathered from atmospheric reanalyses covering the globe. The model predictions are compared to each other and only their relative disagreements are quantified. The largest differences between model predictions are found over central and northern Africa, the Middle East, and all over Asia. This coincides with areas of high aerosol optical depth and highly varying aerosol distribution size. Overall, the differences in modeled DNI are found about twice larger than for GHI. It is argued that the prevailing weather regimes (most importantly, aerosol conditions) over regions exhibiting substantial divergences are not adequately parameterized by all models. Further validation and scrutiny using conventional methods based on ground observations should be pursued in priority over those specific regions to correctly evaluate the performance of clear-sky models, and select those that can be recommended for solar concentrating applications in particular.Accurate modeling of solar radiation in the absence of clouds is highly important because solar power production peaks during cloud-free situations. The conventional validation approach of clear-sky solar radiation models relies on the comparison between model predictions and ground observations. Therefore, this approach is limited to locations with availability of high-quality ground observations, which are scarce worldwide. As a consequence, many areas of in-terest for, e.g., solar energy development, still remain sub-validated. Here, a worldwide inter-comparison of the global horizontal irradiance (GHI) and direct normal irradiance (DNI) calculated by a number of appropriate clear-sky solar ra-diation models is proposed, without direct intervention of any weather or solar radiation ground-based observations. The model inputs are all gathered from atmospheric reanalyses covering the globe. The model predictions are compared to each other and only their relative disagreements are quantified. The largest ...