Calculating Solar Energy Generation from GHI, DNI, and DHI Data

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Discussion Overview

The discussion revolves around calculating the daily energy generation of a 20 kW solar power system using hourly meteorological data, specifically Global Horizontal Irradiation (GHI), Direct Normal Irradiation (DNI), and Diffuse Horizontal Irradiation (DHI). Participants seek to understand how to apply this data to estimate energy output, with some inquiries about the context of the question and the methodology involved.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Homework-related

Main Points Raised

  • Some participants inquire about the context of the question, asking if it pertains to schoolwork and requesting additional details.
  • Participants provide location details (latitude and longitude) and the size of the solar project, emphasizing the use of hourly meteorological data for energy generation calculations.
  • A proposed formula for calculating total energy generation is mentioned: Total generation of units (kWh) = Insolation factor x Yield Factor x Total installed capacity.
  • Questions are raised regarding the orientation of solar panels and how GHI, DNI, and DHI data are used to determine insolation values.
  • One participant mentions a yield factor of 0.89 and expresses confusion about using GHI, DNI, and DHI in calculations, indicating reliance on GHI for their calculations.
  • Another participant suggests using external resources to find average insolation based on latitude and longitude, discussing the potential for more accurate calculations using specific site data.
  • There is a calculation example provided, illustrating how to estimate energy output based on insolation hours and yield factor, along with a monetary value associated with the energy generated.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the methodology for calculating energy generation, as there are multiple inquiries and suggestions regarding the use of meteorological data and the calculation process. The discussion remains unresolved with various viewpoints presented.

Contextual Notes

There are limitations regarding the assumptions made about the use of GHI, DNI, and DHI data, as well as the dependence on specific definitions of insolation and yield factors. The discussion does not clarify how these factors are integrated into the calculations.

athar.walile
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Can we calculate the daily energy generation of 20KW power pack if have the following information:


Date Time GHI DNI DHI
01-01-2008 08:00 0 0 0
01-01-2008 09:00 149 398 75
01-01-2008 10:00 348 686 98
01-01-2008 11:00 512 792 112
01-01-2008 12:00 626 845 119
01-01-2008 13:00 674 859 123
01-01-2008 14:00 659 860 119
01-01-2008 15:00 574 827 112
01-01-2008 16:00 431 753 100
01-01-2008 17:00 245 497 106
01-01-2008 18:00 36 63 30
01-01-2008 19:00 0 0 0

Thank you.
 
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athar.walile said:
Can we calculate the daily energy generation of 20KW power pack if have the following information:


Date Time GHI DNI DHI
01-01-2008 08:00 0 0 0
01-01-2008 09:00 149 398 75
01-01-2008 10:00 348 686 98
01-01-2008 11:00 512 792 112
01-01-2008 12:00 626 845 119
01-01-2008 13:00 674 859 123
01-01-2008 14:00 659 860 119
01-01-2008 15:00 574 827 112
01-01-2008 16:00 431 753 100
01-01-2008 17:00 245 497 106
01-01-2008 18:00 36 63 30
01-01-2008 19:00 0 0 0

Thank you.

What is the context of the question? Can you please provide more details? Is this question for schoolwork?
 
berkeman said:
What is the context of the question? Can you please provide more details? Is this question for schoolwork?

Based on in information i have,

Location of Project : Latitude- 26.9° N, Longitude- 72.0° E
Size of Project : 20 KW
Hourly Meteorological Data : Global Horizontal Irradiation, Direct Normal Irradiation, Diffuse Horizontal Irradiation

I want to find out the possible generation of energy for that plant in KW. I have provided the hourly based meteo data.
 
athar.walile said:
Based on in information i have,

Location of Project : Latitude- 26.9° N, Longitude- 72.0° E
Size of Project : 20 KW
Hourly Meteorological Data : Global Horizontal Irradiation, Direct Normal Irradiation, Diffuse Horizontal Irradiation

I want to find out the possible generation of energy for that plant in KW. I have provided the hourly based meteo data.

Here is the solution

Total generation of units (kWh) = Insolation factor x Yield Factor x Total installed capacity
 
Are your panels fixed? What is their orientation?

How are you using the GHI, DNI and DHI to arrive at a value of Insolation, and is this data your own?

Can you expand upon what Yield Factor incorporates?
 
Zryn said:
Are your panels fixed? What is their orientation?

How are you using the GHI, DNI and DHI to arrive at a value of Insolation, and is this data your own?

Can you expand upon what Yield Factor incorporates?

Yield factor is 0.89

Little confused about using GHI, DNI and DHI values in my insulation calc. but i m using GHI in my calculation. I am not aware of how to use meteorological data here.

I got this data from NREL website: http://rredc.nrel.gov/solar/new_data/India/nearestcell.cgi?
 
Find out your Latitude & Longitude:

http://www.whatsmygps.com/"

Find your Insolation:

http://eosweb.larc.nasa.gov/cgi-bin/sse/grid.cgi?email"

  1. Sign up (its free)
  2. Enter your Latitude & Longitude
  3. Select the data you want ('Average Insolation' only will suffice)

You now have your average monthly Insolation.

Alternatively you can calculate the contribution from GHI, DNI and DHI to your Hourly Insolation relative to the orientation of your solar panel(s) and get much more accurate specific site data, but if you don't need it, the NASA information is a good enough approximation.

So if you have a 2kW system, and have 5 Hours Insolation, you can expect to get (2kW * 5H =) 10kWH from your system that day.

I assume the Yield Factor is an expression of efficiency, so at 89% you would end up with (10kWH * 0.89 =) 8.9kWH instead.

At $0.20 per kWH you would have made/saved (8.9kWH * $0.20 =) $1.78 that day!
 
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