The sun’s not going anywhere, right? At least, science tells us, it’s not going anywhere for another five or six billion years.

And as long as we have the sun, we have the chance to use it as an alternative energy source, to shore up or replace the world’s rapidly dwindling petroleum supplies.

The thought brings solace to many people who, concerned about the energy future of the human race, see solar power as our alternative energy savior, but a closer examination of the realities may not support their belief.

Yes, the sun is good for several billion more years. But the amount of sunlight reaching any particular place on earth, and available for conversion to alternative energy, at any particular moment is limited–by the season of year, the time of day, and the number of clouds in the sky.

At night, or for months at a time in the extreme northern and southern regions of the globe, there is no sunlight at all. And where there’s no sunlight, there’s no alternative energy being created.

Solar power as a viable alternative energy source, when produced through solar cells, has low conversion efficiency–meaning the percentage of the sunlight reaching a solar cell actually converted to electricity–of around 12 percent. And the silicon-based solar cells are still too expensive for wide-spread adoption as an alternative energy option.

Another negative of solar power is that, being collected during sunny weather, it may require storage if it is to be used to provide electricity for heat and lighting. The electricity from solar cells is stored in batteries, which a run of cloudy weather may exhaust. So, in spite of the extra expense, someone using solar cell system should have a back up gas generator in place.

And solar-electric panels require replacement after about twenty years, with the batteries needing replacement every eight to sixteen years.

Solar power as the answer to the fossil fuel dilemma? Not the whole answer, but one among many–and combined with other alternative energy, it may still have a sunny future.