Is there a quicker way of exporting the data from Windographer to Homer?
I would say you have two options.
Option 1: Use long-term monthly averages
Since you have a ten-year data set, you have quite an accurate picture of the long-term wind resource at that site. So you could calculate the long-term average wind speed for each month of the year, enter those monthly averages in HOMER's Wind Resource Inputs window along with the long-term Weibull k and diurnal pattern parameters, and have HOMER synthesize hourly data.
It sounds like you did this, but it would have been a much faster process if you had let Windographer calculate the average wind speed for each month of the year, rather than doing that yourself in Excel. Just go to the Reports tab, choose the Monthly Statistics report, and choose to combine years together. That means Windographer will use all the January data to calculate the overall January average, rather than calculating the January 1997 average, the January 1998 average, and so on. You can cut and paste the averages from Windographer to HOMER.
I would also go to the Stats tab to get the Weibull k, diurnal pattern strength, and hour of peak wind speed, all of which you can also enter into HOMER. You can't do the same with the one-hour autocorrelation coefficient since Windographer can't calculate that from a three-hour data set. Just accept HOMER's default autocorrelation coefficient.
Option 2: Use one year of the data set
You could instead choose the one calendar year that most closely matches the ten-year average wind speed, and export that year of wind speed data from Windographer for use in HOMER. (You can't import the whole data set because HOMER can only accept one year of data.) The process is not as convenient as it should be, and I intend to improve it in the next version of Windographer, but it is not too bad.
Use File / Export to export just the wind speed column to a text file, then edit the text file in a spreadsheet to contain only the one year of data -- exactly one year starting January 1st. Also remove the date/time column and the header rows. HOMER requires the file to contain only one column of numbers, with one time step per line, starting January 1st. HOMER also can't handle gaps in the data, so you might need to fill gaps in Windographer before exporting the data.
Once you have created the text file and stripped it down as I have described, you can import it directly into HOMER's Wind Resource Inputs window. As long as you are using HOMER version 2.4 or later, it will be happy with three-hour data and it should recognize it as such. You can set the simulation time step on the System Control window. If you leave it at 60 minutes then HOMER will just break each three-hour wind speed into three identical one-hour wind speeds. So it is not clever enough to add variability, although we may add that capability in the future
I think either way, you will have quite a high quality wind resource data set in HOMER. If you are more concerned with getting an accurate picture of the seasonal variability in the wind, use the first option. If you are more concerned with getting an accurate picture of the hour-to-hour and day-to-day variability, use the second option.