[GRASS-dev] Re: r.sun units

[Marcel Suri]

Hello,

I looked at the discussion related to the units used in r.sun and can 
just summarize what were other have already said:

The mode 1 gives values of instantaneous solar power (irradiance) 
impinging on a surface in "Watts per square meter" (W/m2) or in other 
words in "joules per second per square meter" (J/m2/s)

The mode 2 integrates solar energy (irradiation) according to 
user-defined steps that is received  by square meter during the whole 
day (actually from sunrise to sunset). The result is given in Watt-hours 
per square meter (Wh/m2) -> if multiplied by 3600, the daily total 
energy received by the surface would be expressed in joules per square 
meter (J/m2).

We are aware of using Watt-hours (as non-SI unit), but this is because 
we work in the field of photovoltaic applications (solar electricity), 
where this unit is still preferred.

Best regards,

Marcel

-- 
Marcel Suri
European Commission - DG Joint Research Centre
Institute for Environment and Sustainability
Renewable Energies Unit
via E. Fermi 1, TP 450
I-21020 Ispra (VA), Italy
phone: +39 0332 786661, fax: +39 0332 789992
http://re.jrc.ec.europa.eu/pvgis/pv/

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Jaro Hofierka wrote:
> Hamish wrote:
> 
>> Hi Jaro, Marcel, Tomas,
>>
>> I was wondering if you could contribute some insight WRT this thread on
>> the GRASS users' list:
>>
>>   http://thread.gmane.org/gmane.comp.gis.grass.devel/17118
>>
>>
>> I fear my advice so far is rather bad.
>>
>> thanks,
>> Hamish