Our petro-industrial civilization produces and consumes a seemingly diverse suite of energies: oil, coal, ethanol, hydroelectricity, gasoline, geothermal heat, hydrogen, solar power, propane, uranium, wind, wood, dung. At the most foundational level, however, there are just two sources of energy. Two sources provide more than 99 percent of the power for our civilization: solar and nuclear. Every other significant energy source is a form of one of these two. Most are forms of solar.
When we burn wood we release previously captured solar energy. The firelight we see and the heat we feel are energies from sunlight that arrived decades ago. That sunlight was transformed into chemical energy in the leaves of trees and used to form wood. And when we burn that wood, we turn that chemical-bond energy back into light and heat. Energy from wood is a form of contemporary solar energy because it embodies solar energy mostly captured years or decades ago, as distinct from fossil energy sources such as coal and oil that embody solar energy captured many millions of years ago.
Straw and other biomass are a similar story: contemporary solar energy stored as chemical-bond energy then released through oxidation in fire. Ethanol, biodiesel, and other biofuels are also forms of contemporary solar energy (though subsidized by the fossil fuels used to create fertilizers, fuels, etc.).
Coal, natural gas, and oil products such as gasoline and diesel fuel are also, fundamentally, forms of solar energy, but not contemporary solar energy: fossil. The energy in fossil fuels is the sun’s energy that fell on leaves and algae in ancient forests and seas. When we burn gasoline in our cars, we are propelled to the corner store by ancient sunlight.
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When and if it gets built the Valhalla project will consist of a 600 MW solar farm and a 300 MW pumped hydro plant which, it is claimed, will in combination deliver continuous baseload power to Northern Chile. If the project works as planned it will indeed deliver continuous baseload power, but only enough to fill about 5% of Northern Chile’s baseload demand. However, it would be the first to demonstrate that baseload power can be generated from a utility-scale PV plant. Development is presently on hold while Valhalla seeks $1.2 billion in financing. (Inset: Valhalla’s solar farm.)
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Tesla is now marketing its Powerwall2 storage battery for domestic applications, claiming among other things that it can make your home self-powered and blackout-proof. Here I review Tesla’s claims using an existing rooftop PV array in the Arizona desert as a real-life example. Will a few Powerwalls allow the homeowner to go off-grid? Not a chance. Will they make the home blackout-proof? Maybe, maybe not. Will they save the homeowner money on his electricity bills? Not that I can see.
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With seasonal variations in output of only around 30% Puerto Rico is at an ideal latitude for solar power, and despite generally low capacity factors (caused by cloudiness) it can be argued that if solar doesn’t work there it won’t work anywhere. And as the results of this post show 100% solar generation can in fact be made to work in Puerto Rico – but only by installing enormously costly amounts of battery storage. The island could be repowered with gas for a small fraction of the cost. (Inset: Average Puerto Rico annual solar radiation.)
