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Rapporto RSE 17001775

Estimating heating and cooling degree-days for Italy



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P. Faggian (RSE SpA), G. Riva (RSE SpA) , R. Bonanno (RSE SpA)

SCENARI 2016 - Analysis and electrical scenarios, energy, environmental


Energy demand for heating/cooling depends closely on surface temperature variability (with maximum energy requirements correlated to temperature extreme values) and heating (HDD) and cooling (CDD) degree-days are used to estimate it.

The indexes HDD and CDD have been calculated for Italy by using daily temperature downloaded by two reference data-sets (E-OBS 1961÷2016, MESAN 1979÷2013) and 10 ENSEMBLES simulations (1961÷2050) and by applying two different methodologies (JRC/MARS and Giannakopoulus).

For both HDD and CDD indexes, the comparison between public JRC/MARS data and the results estimated through JRC/MARS methodology was satisfactory. Instead, the indexes estimated through Giannakopoulus algorithm resulted considerably lower, because of the effect of different basetemperature values.

As energy demand is correlated to building volumes, the location of residential buildings has been considered as another fundamental parameter. Therefore the spatial distribution of Italian populations has been used as proxy data to compute the degree-days indexes. The new HDD values resulted lower than before, consistently with the fact people live mainly in the plains, characterize by temperatures higher than temperatures of less populated mountain regions; the new CDD resulted a bit higher or, at least, similar to those calculated by considering grid-points uniformly.

Future projections show a noteworthy HDD reduction (~25% in 2050) and a significant CDD increase (~100%) according with the expected warming.

Such indexes have been discussed in a working group about the Decarbonisation Strategy established by Presidenza del Consiglio with the aim to provide the necessary input for modeling energetic scenarios, information required in writing the National Energy Action Plan.

In this framework some comparison have been made with the results provided by ISPRA, chair of the same working group.