Analysis of errors in degree days for building energy analysis using Meteorolgical Office weather stations data

Heating degree days are widely used in building energy management for weather normalization of energy use. Degree days are normally calculated at Meteorological Office weather stations sited some distance from the building of interest and this can introduce errors between the degree days used in the calculations and the actual degree days at the building. This paper analyses the major sources of errors in the degree days derived from a newly available data set of Met. Office stations supplied by the British Atmospheric Data Survey (BADC) and compares these errors against those from other available data sets. The BADC data set consists of hourly temperatures for 242 weather stations in the UK from January 2001 until November 2007 and has been converted to monthly degree days for the analysis. The errors have been analysed in terms of measurement and recording errors, errors due to altitude and errors due to spatial separation between weather station and building. The largest error is due to spatial separation between building and weather station. It is therefore important to use data sets with high numbers of weather stations. The data set used in this analysis has been made available on the internet at http:// www.eci.ox.ac.uk/research/energy/degreedays.php and consists of daily, weekly and monthly degree days for over 200 UK weather stations at a range of building base temperatures for the years 19872006. Also included is the 20-year mean for the 55 stations with unbroken records for benchmarking purposes.

Practical application: The paper discusses how errors arise in degree day data when using Met. Office weather stations sited some distance from the building of interest. The paper discusses both the method and the extent of reductions in errors that are possible by using spatially rich weather station degree day data sets. The paper makes the data set used the best for UK degree day monitoring of buildings available through a website, daily, weekly and monthly, over a range of building base temperatures, back to 1986.