John Page

The European Solar Radiation Atlas: a valuable digital tool

The new CD-ROM based European Solar Radiation Atlas (ESRA) is now available. It is published by Les Presses de l’Ecole des Mines de Paris on behalf of the European Commission. This atlas, in 2 volumes, is an instrument dedicated to providing knowledge and aiding exploitation of the solar resources across a wide sweep of Europe, from the Urals to the Azores and from Northern Africa to Polar Circle. It is a powerful tool for architects, engineers, meteorologists, agronomists, local authorities, and tourism professionals, as well as for researchers and students. The input data are based on the period 1981-1990. The first volume provides a broad overview with supporting maps. It starts by describing the course of the Sun across the sky as it varies across the year with geographical location. Then the interactions of the solar radiation with the atmosphere and its components (haze, turbidity, clouds, etc.) and the separation of the solar radiation into the direct and diffuse parts are discussed. The outline structures of the database and the ESRA software package are next described. Sixteen coloured maps provide data on the monthly mean global, beam, diffuse irradiation on horizontal surface and the clearness index for March, June, September and December. The mapped values are averages over the 10-year period 1981-1990. Additionally there are the corresponding four annual maps, also a country-based relief map and a map of ground observing stations used. There are two special maps giving zones of similar irradiation and zones of similar biomass productivity. The second more technical volume comprises a book of 296 pages and a CD-ROM. The book describes the detailed content of the CD-ROM, explaining how it was constructed and how to use the software. The CD-ROM contains a database, which offers spatial (every 10 km approximately) and temporal climatic information for different time scales (from climatological means - more than 700 stations - to hourly values - 7 stations). It includes the solar resources: irradiation (global and its components), sunshine duration, as well as air temperatures, precipitation, water vapour pressure, air pressure for a number of stations. The CD-ROM also contains the software to exploit the database. The software uses either a “map” or a “station” mode at user choice. In the first case, any geographical site can be designated. In the second mode, only the available measuring stations can be selected. The software includes algorithms covering the following fields: solar geometry, optical properties of the atmosphere, estimation of hourly irradiation on slope under cloudless skies, estimation of solar irradiation values (going from daily to hourly values, conversion from horizontal to tilted surfaces), spectral irradiance, illuminance, daily

Units and symbols in solar energy

The application of S.I. units to some common solar energy quantities is discussed and some conversions to S.I. units are given. Then, a list of preferred names, symbols and units is recommended. (SPH)

The geometry of the shading of buildings by various tree shapes

Abstract This paper describes a design tool to be used in assessing the shading effects of trees in relation to buildings. More specifically, an interactive computer program has been written which determines the area and position of the shadows cast by a tree or a group of trees on a surface of any orientation and inclination. The program outputs numerical and graphical hourly results at any time of the day between the sunrise and the sunset, for any day of the year, at any location on the earth for any relative positioning between the tree and the building. The program allows four different shapes of tree (spherical, cylindrical, upright cone or reversed cone) or any combination of these fundamental shapes to be used.

A Web-based Tool for UV Irradiance Data: Predictions for European and Southeast Asian Sites

Abstract There are a range of UV models available, but one needs significant pre-existing knowledge and experience in order to be able to use them. In this article a comparatively simple Web-based model developed for the SoDa (Integration and Exploitation of Networked Solar Radiation Databases for Environment Monitoring) project is presented. This is a clear-sky model with modifications for cloud effects. To determine if the model produces realistic UV data the output is compared with 1 year sets of hourly measurements at sites in the United Kingdom and Thailand. The accuracy of the output depends on the input, but reasonable results were obtained with the use of the default database inputs and improved when pyranometer instead of modeled data provided the global radiation input needed to estimate the UV. The average modeled values of UV for the UK site were found to be within 10% of measurements. For the tropical sites in Thailand the average modeled values were within 1120% of measurements for the four sites with the use of the default SoDa database values. These results improved when pyranometer data and TOMS ozone data from 2002 replaced the standard SoDa database values, reducing the error range for all four sites to less than 15%.

Chapter II-1-A – The Role of Solar-Radiation Climatology in the Design of Photovoltaic Systems

Detailed climatological algorithmic procedures for maximizing solar radiance anywhere in the world on hourly, daily, and monthly basis are discussed in this chapter. Some are accessible as preprogrammed computational chains in user-friendly forms in European (ESRA) and international (SoDa–IS) resources. The chapter also considers PV built-in applications modules.

Chapter IIA-1 – The Role of Solar-Radiation Climatology in the Design of Photovoltaic Systems

Publisher Summary Ideally, one needs long-term time series of solar-radiation data and temperature data for each specific site at the hourly level. Such data are relatively rare, so in recent years statistical approaches have been developed to help fill the gap. Long series of daily data are needed for sizing and modeling of stand-alone systems. Effective statistical approaches have to recognize the links between solar-radiation data and temperature data. Solar-radiation data are often presented in a dimensionless form called the clearness index. The experience gained in the production of European Solar Radiation Atlas 2000 has indicated the great importance of having daily time series of global radiation for making sensibly reliable design decisions. Otherwise, the day-to-day variability patterns in solar radiation due to weather change will be lost. The daily global radiation can be profiled to match the clear-day profile to estimate hourly irradiation values with an acceptable loss in accuracy. The monthly mean values cannot be used with accuracy to simulate daily profiles.