Paper Conference

Proceedings of BSA Conference 2013: 1st Conference of IBPSA-Italy


Derivation of meteorological reference year with hourly interval for Italy

Gianluca Antonacci, Ilaria Todeschini

Abstract: The present paper describes the work which has led to the creation of the meteorological reference year for the whole of Italy, according to the algorithm contained in the UNI EN ISO 15927-4 technical standard. The work was done on behalf of CTI (Comitato Termotecnico Italiano). The above standard specifies a method to derive the hourly values of weather data needed to assess the annual energy needs for building heating and cooling. The obtained time series is built up by 8760 hourly records extracted from longer time series (theoretically at least 10 years). In meteorological data processing particular attention was paid to the quality check of collected data. The reference year thus contains records for the following parameters: temperature, solar radiation, relative humidity, wind speed. The first three are the key values for calculation of the energy budget needed for heating and cooling. This approach enables the development of calculation methodologies towards the direction of a dynamic thermal design in which the external forcing is given with hourly interval, instead of through monthly averages as currently contemplated in the current version of UNI 10349 standard. The reconstruction procedure of the meteorological reference year is based on the extraction of hourly data from multi-year records and subsequent statistical analysis; the algorithm is discussed in detail in the paper. For each Italian administrative Province, weather stations operated by local agencies were taken into account where at least ten years of data were available. Besides the implementation of the algorithm, we discuss the practical problems encountered in managing these meteorological data, caused by strong heterogeneity resulting from different types of networks, sensors, data acquisition methods and standards. The uncertainty about the result caused by these issues is also qualitatively assessed and the advantages and disadvantages of the adoption of hourly varying time series with respect to averaged values for the thermal design of buildings is discussed.
Pages: 49 - 58