Re: [EnergyPlus_Support] Re: AMY-weather files for North Europe

Hi Joe,

I refer to the IWEC1 (from 2000) files. I wasn't actually aware of the IWEC2 files set. Interesting, these IWEC2 files seems to have a very good coverage rate for North Europe. I'll order one of those DVDs straight away. Can you direct me to some documentation & validation for these IWEC2 files?

Now, regarding the underestimation of the IWEC1 files (from 2000): I've made a very brief study on 13 selected IWEC files for Europe; this will be included in my degree paper that is just about to be published. I'll send you private mail of that study.

Let's take an example. The "Stockholm Arlanda 024600 (IWEC)" file has a yearly mean of 89 W/m^2 for the direct normal radiation parameter (the yearly mean value is obtained by taking the mean value of 15nth column in the IWEC file). The STRÅNG modeling system will give a mean of 130 W/m^2 for the period 1999-2011. From the validation figure http://strang.smhi.se/validation/y_hoi_rel_all.html we can see that the STRÅNG modeling system have a relative MBE of -1.6% for the validated period for the direct parameter. We can thereby assume that the 130 W/m^2 is very near the real long term yearly mean direct solar radiation of Stockholm. So the IWEC1 seems to be underestimating the direct parameter by about 32% for Stockholm, Sweden.

Example 2. The "Helsinki 029740 (IWEC)" file has a yearly mean of 81 W/m^2 for the direct normal radiation parameter. The STRÅNG modeling system will give a mean of 107 W/m^2 for the period 1999-2011. Let's also look at the "Vantaa_TRY2012" file for the same location, this is a high quality TMY-file done by the Finnish Meteorological Institute and is based on measured data (http://ilmatieteenlaitos.fi/c/document_library/get_file?uuid=0b30fa2d-86b5-4b0b-b10c-81356620ba5c&groupId=30106). This file has a yearly mean of 129 W/m^2 on the direct normal radiation parameter. So the IWEC1 seems to be underestimating the direct parameter by about 37% for Helsinki, Finland.

The same pattern can be seen in the 13 IWEC1 files I've looked at. I take it you have been involved in the making of the IWEC2 and maybe the IWEC1 files as well? I would be very pleased for comments from you regarding this matter.

Best regards,
Lukas Lundström

--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, Joe Huang <YJHuang@...> wrote:
>
> Lukas,
>
> In your post below, you had said,
>
> "Even though the solar data from STRÅNG varies in quality it's still better, for most
> sites, than that provided in the ASHREAE IWEC files (which underestimate direct solar
> radiation in the range of 20 to 40 % for the area in question)."
>
> Are you referring to ASHRAE's IWEC files (done in 2000) or the IWEC2 files (done in
> 2010)? I'm surprised at your assessment of 20-40% underestimation of direct solar
> radiation, since the solar on both the IWEC and IWEC2 files were calibrated against
> measured solar data, which was relatively more plentiful for locations in Northern
> Europe. Could you provide some documentation for your assessment ?
>
> Thanks.
>
> Joe
>
> Joe Huang
> White Box Technologies, Inc.
> 346 Rheem Blvd., Suite 108D
> Moraga CA 94556
> yjhuang@...
> www.whiteboxtechnologies.com
> (o) (925)388-0265
> (c) (510)928-2683
> "building energy simulations at your fingertips"
>
>
> On 11/7/2012 4:18 AM, rokkas80 wrote:
> >
> > Hi all,
> >
> > I've updated my tool for creating Actual Meteorological Year (AMY) files for North
> > Europe. The tool can be downloaded at
> > http://rtwc.blob.core.windows.net/clickonce/publish.htm.
> >
> > News for this version, Real-Time Weather Converter 2.0:
> > - All data from ISD is available, also data marked as "Additional". If you tried the
> > tool before but didn't get any data for your station, you should now be able to get
> > usable data for most locations.
> > - A new server that maps data from the SMHI server. Now retrieval time are just a few
> > seconds for one year of solar data. A AMY-files can now be made in under a minute.
> > - Missing data points are visualized graphically.
> >
> > The tool was made as part of my MSc degree project at Mälardalens University, Sweden. It
> > uses observed actual weather data from the Integrated Surface Database (ISD),
> > http://www.ncdc.noaa.gov/oa/climate/isd, and modeled solar radiation data from STRÅNG,
> > http://strang.smhi.se.
> >
> > Roughly, the tool covers most of Europe excluding south Europe. Long-term coverage is
> > from 1 of January 1999 to up to date for the northernmost area, the southern area is
> > covered from 1 of June 2006 (see website for map).
> >
> > The quality of the solar radiation data from STRÅNG varies in the geographical
> > dimension. Roughly the model gives good result for Sweden and Central Europe, but
> > underestimates for ocean coast near areas like UK, Norway etc. The model do
> > underestimate as well for the Baltics, northern Finland and some high altitude sites.
> > There's a validation figure (for Google Earth) at the tools homepage in the help
> > section. Even though the solar data from STRÅNG varies in quality it's still better, for
> > most sites, than that provided in the ASHREAE IWEC files (which underestimate direct
> > solar radiation in the range of 20 to 40 % for the area in question). For model
> > calibration these data are very useful.
> >
> > You are free to use the modeled solar radiation data from STRÅNG. Weather data from ISD
> > may however have restrictions regarding commercial usage, depending on country and what
> > data is being used. Some countries (UK, Norway, Netherlands, Slovenia and Sweden from
> > next year(?)) have free weather data, other countries some restrictions and some
> > countries have most of their weather data restricted. There is a method in the tool that
> > excludes data marked as "Additional" by WMO, this should make commercial use of
> > resulting weather files possible for most countries (my personal interpretation of WMO
> > resolution 40 Annex I). But it's up to the end user of the tool to read and interpret
> > the WMO resolution 40 and check with their National Weather Service for their data
> > policy. If intentions are non-commercial the data accessed and created by this tool can
> > be used freely for all countries in question.
> >
> > The ISD lack recent data for many of the German weather stations. Observed weather data
> > can still be acquired from other sources (i.e. EnergyPlus real-time weather service,
> > Wunderground) and by using copy/paste inserted into the tool. The tool has methods for
> > re-sampling, interpolating and filling data gaps.
> >
> > This tool was developed to make AMY-files to be used for model calibration. But it would
> > be possible to use a similar approach to create Typical Metrological Year (TMY) files as
> > well, at least for the geographic area where there soon exist 13 years of free solar
> > radiation data available free via STRÅNG. Let me know if you think there's a demand for
> > this kind of weather files or if you know of any available tools or algorithms that can
> > make this kind of files.
> >
> > Best regards,
> > Lukas Lundström
> > https://sites.google.com/site/weatherconverter
> >
> >
>