The Solar Resource

The Earth s elliptical orbit causes the distance between the Earth and the Sun (the Earth s radius vector) to vary by 3.39% from perihelion (closest) to aphelion (farthest). These variations in distance cause the intensity of solar radiation at the top of the atmosphere to vary as 1/R2, where R is the radius vector. Thus the solar input at the top of the atmosphere varies from 1414 Wm 2 (in December) to 1321 Wm 2 (in July). Additional variations in solar intensity, or brightness, result from the solar sunspot cycle, and even solar oscillations. These slight variations in the solar output are usually accounted for in the calculation of solar energy available at the top of the atmosphere, or the total extraterrestrial solar radiation, referred to as ETR. The ETR has only been monitored from space since the early 1970 s, or almost three solar sunspot cycles. Excellent histories of ETR measurements and analysis are provided in Frohlich3 and Gueymard.4 

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In the case of Algeria, the distribution of the solar resource can be subdivided into three zones coast al (humid climate), atlas (cold in winter and hot in summer), and Saharan (dry desert climate) with typical average values of annual daily horizontal irradiation 4 kWh/m2, 5 kWh/m2, and 6 kWh/m2, respectively. Unfortunately the solar potential is still not accurately known because of the lack of data recordings.1 Thus, to overcome such problem one needs to search for other data sources. Among the existing ones,2 3 4 5 we have chosen the NASA website which proposes a ten-year solar radiation database that covers globally the whole Algerian territory. 

Above, we described the solar resource at the top of the atmosphere. The atmosphere acts as a continuously variable filter for the ETR radiation. The atmosphere has stable components of 78% nitrogen, 21% oxygen, and 1% argon and other "noble" gases. There are also variable components in the atmosphere, such as water vapor (0% to 2% of the total composition), and gases dumped into the atmosphere by manmade and natural process, such as carbon dioxide, (0.035%), methane, and nitrous oxides.6... 

Sizing - The process of designing a solar system to meet a specified load given the solar resource and the nominal or rated energy output of the solar energy collection or conversion device. 

Renewable sources are attractive for sustainability - e.g., wind, hydro, tidal, solar etc., and geographic factors will determine where each is appropriate. However, the sheer size of overall demand points to solar - the solar resource far outstrips all others. With a global usable energy flux of 120 PW, it is some 8,000 times the current total energy use, and able to supply growing demand as far ahead as we can see [6]. 

National Renewable Energy Laboratory (NREL) Renewable Resource Data Center - the solar resource, http //www.nrel.gov/iredc/solar resource.html. Accessed 1 Nov 2010... 

Energy storage is fundamental to large-scale utilization of the solar resource. Nocera and coworkers have developed redox reactions of dimetal centers that exploit aurophilic interactions and metal-lophilicity more generally. 

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