Spatial distribution : Many kinetic energy flows are inherently diffuse. The total amount of solar energy which falls on Earth is far more than our society could use. However, at any given time that energy is spread over about 100 million square miles of surface. The energy we desire to use must be far more concentrated than that, so we need to come up with a way of collecting that diffuse energy, concentrating it, converting it to some sort of stored potential energy and transporting it to where the people are. This is easier said than done. Similarly, wind energy is fairly diffuse and, likewise, requires investment in complex mechanisms to concentrate it into usable form for our existing societies. Energy from water, on the other hand, is concentrated in places (for example waterfalls) which are themselves distributed spatially from each other and from where we might wish to have energy. Basically, kinetic energy from Earth’s hydrological cycle isn’t always where the people are. Intermittence : Some energy (e.g. wind power) is intermittent - you have access when the wind blows, but not when it is calm. Other energy, (e.g. tidal power) varies in its availability, but is entirely predictable. Solar power combines both: intermittent because of clouds, and variable because of day and night. Since our current civilization is bu ilt around “baseload” power, we expect the lights to go on when we flip a switch. This luxury is very energy -costly because it means that even while we sleep, the engines that convert potential to kinetic energy are spinning, awaiting the commands to spin faster based on our needs and whims. However, most ways of obtaining energy from natural flows do not provide “energy on whim;” they provide it based on the way the natural world provides it, which is intermittent, or variable or both. Your author, DJ White, has grid-tied solar panels on his house and can track the rough power accumulation by the hour, day, and month. The tracking reflects the high incidence of clouds in his home location of windward Oahu in sunny Hawaii. His solar energy capture is less than half of the no-clouds energy capture available elsewhere and is also extremely unpredictable. Having a small percentage of such systems in a distribution grid can work well, if it’s used in real time by other homes in the neighborhood, and the variability can be compensated for by the other grid energy inputs, by throttling them up or down. But if the system consisted of nothing BUT such energy-capturing devices, it would not function in the same way as a baseload system. You would have to use the power when the power was available and accept there will be no energy at night. (Well, there would be at
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