365.25 is a number, not a product. This is 365 1/4 - the length of an year in days. This is more precise, than to use 365.

Hi dear mr shahnawaz

I'm making a program with matlab software to calculating solar radiation in selected location

this is calculating the solar energy in hour and day and month and year and trace the curve of the energy in deferent surface slope angle and gama angle in collector

please see solar energy engineering kalogirou ebook

Dear Kamran Thank you very much for your reply.

there are three forms of equation for Ho, which one is for houly calculation and which one for daily or monthly or yearly calculations?

Also two form of equations are available for "Gon", in one, denominator 365 is multiplied by 25; whereas in other two equations there is on 365 in the denominator; which one is used for hourly or daily or montly or yearly?

Refer the text book named as "Solar Energy - Principles of Thermal Collection and Storage" by S.P.Sukhatme for better understanding and to find the method of calculation.

Thank you Mr. Jagani for your valuable suggestion

365.25 is a number, not a product. This is 365 1/4 - the length of an year in days. This is more precise, than to use 365.

For these three equations it's important to know the units of measure of all participating variables. This could explain why sometime the intermediate results are estimated for seconds, or for minutes or for hour...

P.S. My favorite paper about this and other similar topics (very good for beginners) is this:

https://www.researchgate.net/publication/2539232_The_solar_radiation_model_for_Open_source_GIS_implementation_and_applications?ev=srch_pub&_sg=bmK5CvOWRb47TISbdjS5KR9sJg0YDodJI3vFp1zEr%2BLSrzx8OATPsGRcA8ms0n5S_1pL7rL%2FEeAXChu%2FWruvlw05ZeDwcT4nyct3Xs9%2FkcEwirCl55PzSqtE%2F6rJF%2BSld

Article The solar radiation model for Open source GIS: Implementatio...

Thank you very much Ms Stoyanka Ivanova, (and I am really sorry that I couldn't understand decimal in between 365 and 25 )

I appologize for bothering all the respected members of RG.

http://www.google.com/url?sa=t&rct=j&q=solar%20energy%20engineering-processes_and_systems_2009.pdf&source=web&cd=9&ved=0CGcQFjAI&url=http%3A%2F%2Fwww.1on1help.me%2Fengineering%2Fsolar%2520energy%2520engineering.pdf&ei=vR1aU5qlJ4vFtAai0IHABA&usg=AFQjCNHe0LuE0kqYfmmrzFn4uX9S7wYMWQ&sig2=lQHD44BSx4OMZLFEiNm7kg&bvm=bv.65397613,d.Yms&cad=rja

Dear Kamran Ramezani,

Thank you for your help.

best regards,

This is modified attachment

Please refer to the text book by "Duffie and Beckman" to understand the detail procedure.

Dear Mahmudul Hasan, I will refer the book... Thank you

Herlo,

I have built excel-base model, if you still have problem let me know.

I will be thankful if you could share it with me on my email address "[email protected]"

First equation for Ho, which starts with 24*3600/Pi, if you check the original paper, you will see there Ho has to be received in joules per sq.meter. The units of Gsc are Watts per sq.m. The equation looks this way because of the conversion from watts to joules: http://www.rapidtables.com/convert/electric/Watt_to_Joule.htm

Dear Ms Stoyanka Ivanova,

I have sent you paper through email. please have look on it no unit is written..

I am really very thankful for your help and guidance.

Best regards,

Okay, you will get it on Subday once I go to my office

Dear Mohamad Kharseh,

Thank you

kind regards,

Actually in the paper you sent me by email, there is a nomenclature section on page 2, where all variables are explained and you can see their units:

Ho - ..... [MJ/m^2]

but I suppose, this [MJ/m^2] is a mistake, because the result from eq.(21) should be in J/m^2, not in MJ/m^2 (guess why!). In such case better check the source of this formula - [25] in references list.

Please, check again the link, sent by Kamran Ramezani some posts ago. Here is it again:

http://www.1on1help.me/engineering/solar%20energy%20engineering.pdf

On page 90, eq. (2.79) - the units are joules per square meter.

It's very important to notice and think about the units of the participating variables. This is a very good way to understand the meaning of the equations

http://en.wikipedia.org/wiki/Units_of_measurement

or even to create new formulas:

http://en.wikipedia.org/wiki/Dimensional_analysis

...

One example of the importance of agreed units is the failure of the NASA Mars Climate Orbiter, which was accidentally destroyed on a mission to Mars in September 1999 instead of entering orbit due to miscommunications about the value of forces: different computer programs used different units of measurement (newton versus pound force). Considerable amounts of effort, time, and money were wasted.

On April 15, 1999 Korean Air cargo flight 6316 from Shanghai to Seoul was lost due to the crew confusing tower instructions (in metres) and altimeter readings (in feet). Three crew and five people on the ground were killed. Thirty seven were injured.

In 1983, a Boeing 767 (which came to be known as the Gimli Glider) ran out of fuel in mid-flight because of two mistakes in figuring the fuel supply of Air Canada's first aircraft to use metric measurements. This accident is apparently the result of confusion both due to the simultaneous use of metric & Imperial measures as well as mass & volume measures.

http://en.wikipedia.org/wiki/Units_of_measurement

Dear Ms Stoyanaka Ivanova,

You are right, proper unit conversion is really very important.

It means authors must specify the clear units of terms/formulae they used in their publications.

I am also referring the book.

Once again I am really very thankful for your efforts and for answering my queries in detail.

Best regards,

You can see text books on solar energy by S.P.Sukhatme, Tata McGraw Hill, or by Kreith Mc Graw Hill Publications.  The procedure is available in most of the books on solar energy.  There are various terms in the equation relating to sun and earth .  

can you send me the data that you have?

How do calculate the coefficients a and b in the equation Angstroms-Prescott? (please see the attached file)

do the regression  following the models available in the literature.

Assistant can explain the details of the work

I want information /latitude of sit

e mail [email protected]

https://www.saecanet.com/calculation_page/000436_000565_extraterrestrial_radiation.php