The Natural Economy is Solar Powered

The natural economy is solar-powered. Photons from the sun rain down upon the entire daytime surface of the planet. Many photons do nothing more useful than heat up a rock or a sandy beach. A few find their way into an eye - yours, or mine, or the compound eye of a shrimp or the parabolic reflector eye of a scallop. Some may happen to fall on a solar panel - either a man-made one like those that, in a fit of green zeal, I have just installed on my roof to heat the bathwater, or a green leaf, which is nature's solar panel. Plants use solar energy to drive 'uphill' chemical syntheses, manufacturing organic fuels, primarily sugars. 'Uphill' means that the synthesis of sugar needs energy to drive it; by the same token, the sugar can later be 'burned' in a 'downhill' reaction that releases (a fraction of) the energy again to do useful work, for example muscular work, or the work of building a great tree trunk. The 'downhill' and 'uphill' analogy is with water flowing downhill from a high tank and driving water wheels to do useful work; or being energetically pumped uphill into the high tank, so that it can later be used to drive water wheels when it flows downhill again. At every stage of the energy economy, whether uphill or downhill, some energy is lost - no energy transaction is ever perfectly efficient. That is why patent offices don't need even to look at designs for perpetual motion machines: they are implacably and forever impossible. You can't use the downhill energy from a water wheel to pump the same amount of water uphill again so that it can drive the water wheel. There must always be some energy fed in from outside to compensate for the wastage - and that is where the sun comes in.

All life on Earth deals in exchanges of sunbeams.