We are contacting you because you downloaded one or more of the building energy weather datasets from the CSIRO Data Shop:
There are now updated versions of some of these datasets available in the CSIRO Data Shop:
Projected weather files for building energy modelling
ProjectedWeatherFilesEpw_20240531.zip
Typical Meteorological Year weather files for building energy modelling
TMYWeatherFilesEpw_20240528.zip
The changes made are:
1. Change in way time mapped from NatHERS to .epw format
2. Change in how radiation data obtained
3. User Guide updated to reflect these changes
Change in way time mapped from NatHERS to .epw format
The NatHERS format uses hours 0, 1, 2, 3, …, 23, whereas the EnergyPlus (.epw) format uses hours 1, 2, 3, 4, …, 24
In the previous versions of the datasets in .epw format, when NatHERS data was converted to .epw format, NatHERS hour values were mapped to .epw hour values as follows: 0->1, 1->2, 2->3, …, 23->24.
In the current version of the dataset, when NatHERS data is converted to .epw format, NatHERS hour values are mapped to .epw hour values as follows: 0 not used, 1->1, 2->2, …, 23->23.
For the last hour of each month (.epw hour 24), instead of using a value from the NatHERS RMY dataset (e.g. from hour 0 of the following month), critical variable values have been taken from the third party (non-CSIRO) 2016 TMY dataset. This avoids any potential problems in cases where consecutive months in the RMY/TMY datasets contain data which have been selected from the BOM weather data from different years.
These changes result in a better alignment of variable values with the .epw time period.
Change in how radiation data obtained
In the previous versions of the datasets in .epw format, values for the three radiation variables Global Horizontal Radiation, Direct Normal Radiation, and Diffuse Horizontal Radiation were based on values from the NatHERS RMY files. The current version of this dataset takes these values from the third party (non-CSIRO) 2016 TMY dataset.
The reason for this change is that for the NatHERS RMY files, the radiation values are calculated centred around the hour. For example, radiation at hour 9 relates to radiation for the period 8:30AM to 9:30AM. Whereas the .epw format defines radiation values as relating to the hour preceding the stated hour. For example, radiation at hour 9 relates to radiation for the period 8:00AM to 9:00AM.
The radiation values in the third party (non-CSIRO) 2016 TMY dataset are consistent with the .epw understanding of radiation values.
Regards,
Melissa James
Melissa James
Senior Experimental Scientist
Energy | CSIRO
melissa.james@csiro.au T 03 9545 2247
Private Bag 10, Clayton South VIC 3169
Work days Monday-Thursday
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