18 Jun How to import climatic data into Excel
When you start a design on a new site, one of the first things you should check is the weather of that site. Is it hot and dry? Hot and humid? Mild weather?. By knowing the weather we could be aware of the most appropriate HVAC system we could use.
In this post, we learnt how to create a psychrometric chart in Excel, so, could we include climatic data in this chart, to have a graphical view?
Now, let’s see how to import climatic data into Excel.
Where can we get Weather Data?
We use weather data normally for building performance simulation (by means of software like Hourly Analysis Program by Carrier, https://www.carrier.com/commercial/en/us/software/hvac-system-design/hourly-analysis-program/). There are a few types of files. The most used are the following, with their respective extensions:
- DDY. ASHRAE Design Conditions or “file” design conditions in EnergyPlus format.
- EPW. EnergyPlus Weather Format.
- STAT. Expanded EnergyPlus weather statistics.
Please note that the values included in these files are typical, so they don’t include extreme weather conditions that perhaps shall be used for a critical HVAC system (see this post).
We will focus on the EPW files. Epw files collect a typical year hourly weather data (8760 points) from a range of years. We can download from different sites, by selecting the appropriate site location. A couple of sites we can do that are:
We are going to use the second link for this example, specifically data for Cork, by selecting Region 6 – Europe, Country Ireland. After this we arrive on this page:
And selected the file IRL_ST_Cork.AP.039550_TMYx.2004-2018.zip.
Once opened the zip file, the one with epw extension is our target, so we proceed to extract it:
Import file into Excel
Now we are going to import data to Excel, as the usual way, taking care of selecting “All files” when opening:
The import wizard opens and we select “Delimited” as our data are presented separated by commas. Following “Next”:
Select only ‘comma’ as delimiter, and press ‘Next’:
Finally leave as it is in column data format, ‘General’ and ‘Finish’
(At this point you may be interested in looking at how to plot the psychrometric chart, here: https://www.pharmaceuticalhvac.com/a-psychrometric-chart-in-excel/)
There is a lot of data: dry bulb temperature, dew point, relative humidity, data related to radiation, wind speed, etc. But for our interest, we will consider columns G (Dry bulb temperature), column I (relative humidity) and column J (barometric pressure). Rows 1 to 8 will not be used either.
So we will copy columns G, I and J into a sheet where our psychrometric chart is plotted:
With the imported data we only have to add a column with the humidity ratio for each point, by using the function Hum_rat2 from the psych add-in (note the units of pressure in kPa and relative humidity in 1 percentage)
And fill down to the 8760 points:
We add a new series in our graph, with the name ‘weather’:
And finally, this is the result with all the points plotted scattered:
As we can see, Cork climate is typically mild oceanic, without extreme temperatures.