Definition of kw/m2

  • Vijaykrishna
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14 Jan 2013 16:21 #1167 by Vijaykrishna
Definition of kw/m2 was created by Vijaykrishna
Greetings,
I have a couple of questions and they are as follows:

* Does anyone know how kW/m2 is calculated and how is is related to kWh/m2 in SAM?.
* Definition of "Maximum Kw/m2" for a particular PV array for every hour under Hourly 8760 Table?.

Thank you.

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  • Paul Gilman
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14 Jan 2013 17:58 #1168 by Paul Gilman
Replied by Paul Gilman on topic Definition of kw/m2
Hello,

In general, variables with kW/m2 units in SAM are for solar radiation data in the weather file, or for incident radiation values calculated from the weather file data. For weather files that follow the TMY file format convention (For example, see Table 1-3 in the TMY3 Users Manual [ PDF 1.7 MB] ), the data represents a total amount of radiation in kWh (or Wh) received in one hour by one square meter of a surface with a given orientation. Because the data is hourly data, the units are kWh/m2 per h, which can be written as kW/m2. In SAM, as long as you are working with hourly data, kWh/m2 and kW/m2 are equivalent units.

Some of SAM's performance models report both a total kW/m2 value and a maximum kW/m2 value. That is because we are developing sub-hourly versions of some of the models. For solar radiation data with a subhourly time step (e.g., 1-minute, 10-minute, or 15-minute), for each hour, SAM records two values: The total radiation in the hour, and the radiation for the timestep within the hour with the maximum value.

For now (SAM 2012.11.30), only the physical trough model fully supports subhourly weather data.

Best regards,
Paul.

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  • vijaykumar
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15 Jan 2013 11:52 #1169 by vijaykumar
Replied by vijaykumar on topic Definition of kw/m2
Hello vijay Krishna,
According to my opinion SAM shows the Kwh/m2 value for the annual in that location to get for the monthly you should divide it by the 365days than you will get the data for the day and if you what for the hourly u can divide it by the number of hours you will get the hourly data. And for the satellite data it takes on the mean of that hour. This is according to my opinion if any suggestions let me know...

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  • Vijaykrishna
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15 Jan 2013 15:26 #1170 by Vijaykrishna
Replied by Vijaykrishna on topic Definition of kw/m2
The kw/m2 is actually kwh/m2 for hourly data!. Thank you Sir Paul. That was driving me nuts!

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  • Vijaykrishna
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15 Jan 2013 15:30 #1171 by Vijaykrishna
Replied by Vijaykrishna on topic Definition of kw/m2
Hello Vijay Kumar!
I agree with what your approach. But my question was specifically directed to SAM's methodology of obtaining kw/m2. I was confused between the representation of energy(kwh/m2) as Power(kw/m2), but Paul's comment cleared my confusion.

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  • vijaykumar
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16 Jan 2013 09:52 #1172 by vijaykumar
Replied by vijaykumar on topic Definition of kw/m2
Hello vijay krishna,
you have confused about the KWh/m2 and kw/m2 k i thought of how u get that value any thats good what ever the paul said was right both are same u go ahead... :)

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