Energy potential PSI

Insolation:

Insolation (not insulation, which is something else entirely) various by region, climate, cloud cover, latitude, and other factors. This website is a very useful starting point. However, it does not integrate the insolation values by region to come up with the total insolation received by a complete hemisphere (nor can it, as the Earth is not a homogeneous surface with constant atmospheric conditions). However, the website does give you the sort of information you would need to tailor your 'collector' (for lack of a better term) to a particular region/climate.

Solar Panels:

Your solar panels need not 'condense' light in some fashion in order to be more efficient, as the light collected by the 'condensers' (lenses or reflectors, presumably?) will have to collect this light from the same area as a panel having that same area. Focusing the light or concentrating it will not change amount of energy collected. Consequently this same area can be presented to the sunlight directly by the panels themselves. What is more important is that the collectors absorb light efficiently at the wavelengths of interest and convert that light energy into the desired form, usually heat or electricity.

Some solar generators do direct sunlight collected by a large array of heliostats onto a collector in order to raise the collector temperature high enough to produce steam.

Solar furnaces collect sunlight in a similar manner to produce temperatures high enough to melt just about any material. But these are usually built for research purposes.

Where silicon or GaAs panels are used to generate electricity, the panel converts light into electricity at some wavelengths more efficiently than others. There has been recent progress on the development of fluorescent compounds which convert the less-usable wavelengths into wavelengths at which the collector materials convert more efficiently thus improving the overall efficiency of the collector.

Does this help?

Outside the atmosphere, the impinging energy on a unit surface, having sun inclined of θ with respect to its normal, is expressed as:

S(W/m2) = σ * Tsun⁴ * (Rsun/Dsun)² * cosθ

Where σ is the Stefan-Boltzmann constant (5.6686 W/m²K⁴), Tsun is the apparent absolute (blackbody) temperature of the Sun, (coarsely 5800 K), Rsun is the apparent radius of the Sun (about 6.957*10⁸ m) and Dsun is the distance of the surface from Sun.

As for Earth, being Dsun = 1.49675*10¹¹ m, the energy on a unit surface orthogonal to solar flux (θ = 0) results about

S = 1400 W/m²

This value is defined as Solar Constant. Actually, due to the eccentricity of the earth orbit, the Solar Constant may be varying between 1370 and 1430 W/m². This is the maximum energy that can be received on a unit surface, parallel to planet surface, when Sun is at its zenith (i.e., the surface is located at sub-solar point).

Of course, this figure is much lower at earth level, due to the following items:

- Actual latitude and longitude of the surface location on earth, determining the value of the θ angle

- Absorption, and scattering of the earth atmosphere: these effects are depending on latitude and longitude also, but on many others uncertain aspects (clouds, dust, gaseous composition of air, etc.). Note that the scattering has a double effect on radiation: part is transmitted diffusely to soil (this has a "smoothing" effect on the distribution of the radiated energy), and part is reflected back to space.

The determination of the reduction factor to be applied to the Solar Constant in not easy. As a thumb rule, it can be assumed that in best conditions (sunny weather, no clouds) the gas absorption is 23% of the total radiation, corresponding to a maximum heat flux of about 1100 W/m². This is a very optimistic assumption. As a reference condition, by considering the data reported in the suggested site, 50% of solar radiation can be assumed reaching earth soil, corresponding to a maximum figure of 700 W/m². But better assessment should be required, relying upon accurate monitoring of the earth surface.

Arrivederci Cipo - minor comment - you left out factor 10^-8 in the Stefan-Boltzmann constant. Just as well it's not 5.6686 W/m²K⁴ or things would be rather warm on Earth!

Cheers....Codey

REALLY????

Probably that's the reason why here it is t-r-e-m-e-n-d-o-u-s-l-y hot today!!!

Ciao

WOW! - Thanks you guys - give me some time to digest this.