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1 " A useful analogy is to see traditional societies as relying on instantaneous (or minimally delayed) and constantly replenished solar income, while modern civilization is withdrawing accumulated solar capital at rates that will exhaust it in a tiny fraction of the time that was needed to create it. "
― Vaclav Smil , Energy: A Beginner's Guide
2 " Unfortunately, motor vehicles are also responsible for 1.25 million accidental deaths every year (and more than ten times as many serious injuries), "
3 " A good many times I have been present at gatherings of people who, by the standards of the traditional culture, are thought highly educated and who have with considerable gusto been expressing their incredulity at the illiteracy of scientists. Once or twice I have been provoked and have asked the company how many of them could describe the Second Law of Thermodynamics. The response was cold: it was also negative. Yet I was asking something which is about the scientific equivalent of: “Have you read a work of Shakespeare’s?” Despite "
4 " Energy will do anything that can be done in the world. Johann Wolfgang von Goethe (1749–1832) "
5 " Despite these advances, internal combustion engines remain rather inefficient prime movers and the overall process of converting the chemical energy of gasoline to the kinetic energy of a moving passenger car is extraordinarily wasteful. "
6 " No forecasts then – only brief reviews of some key factors that will determine the world’s future quest for a reliable and affordable energy supply, and the major resource and technical options we can use during the next half-century. "
7 " We have three choices if we wish to keep on increasing global energy consumption while minimizing the risks of anthropogenic climate change due to rising combustion of fossil fuels and keeping atmospheric levels of greenhouse gases from rising to as much as three times their pre-industrial level: we can continue burning fossil fuels but deploy effective methods of sequestering the generated CO2, we can revive the nuclear option, or we can turn increasingly to renewable energy. None of these options is yet ready to take over from fossil fuels on requisite scales, none could be the sole near-term solution, and all have their share of economic, social, and environmental problems "
8 " Hydrolectricity is the largest modern non-fossil source of primary energy; the combination of relatively low cost, high suitability to cover peak demand, and the multi-purpose nature of most large reservoirs (they serve as sources of irrigation and drinking water, a protection against downstream flooding, recreation sites, and, increasingly, places for aquacultural production) should make it one of the most desirable choices in a world moving away from fossil fuels. "
9 " the International Commission on Large Dams put the global potential of economically feasible projects at just over 8 PWh, roughly twice the current rate of annual generation. "
10 " Efficiencies of PV cells have risen from less than five percent during the early 1960s, when the first modules were deployed on satellites, to twenty-five percent for high-purity silicon crystals in the laboratory, but the field efficiencies are around fifteen percent. PV films, made of amorphous silicon (or gallium arsenide, cadmium telluride, or copper indium diselenide), have reached as much as twenty-two percent in the laboratory, but deliver eleven to thirteen percent in field applications. Declining costs of PV cells have made them particularly competitive in sunny locations where their capacity factor can average twenty five percent (compared to just over ten percent in Germany). "
11 " More efficient photovoltaic cells would be most welcome because of their relatively high power densities: efficiencies close to twenty percent would translate to electricity generation rates between 20–40 W/m2, two orders of magnitude better than biomass conversion, and one better than most hydro and wind projects. "
12 " Finding out how much food actually is consumed is a challenging task, and neither dietary recalls nor household expenditure surveys yield accurate results. "
13 " Despite its supposed universality, the second law appears to be constantly violated by living organisms, whose conception and growth (as individuals) and whose evolution (as species and ecosystems) produces distinctly more ordered, more complex forms of life. But there is really no conflict: the second law applies only to closed systems under thermodynamic equilibrium. The Earth’s biosphere is an open system, which incessantly imports solar energy and uses its photosynthetic conversion to new plant mass as the foundation for greater order and organization (a reduction of entropy). "
14 " Clausius also crisply formulated the second law of thermodynamics: entropy of the universe tends to maximum. In practical terms this means that in a closed system (one without any external supply of energy) the availability of useful energy can only decline. "
15 " Heat thus occupies a unique position in the hierarchy of energies: all other forms of energy can be completely converted to it, but its conversion into other forms can never be complete, as only a portion of the initial input ends up in the new form. "
16 " The second law of thermodynamics, the universal tendency toward heat death and disorder, became perhaps the grandest of all cosmic generalizations – yet also one of which most non-scientists remain ignorant. "
17 " Finally, the third law of thermodynamics, initially formulated in 1906 as Walther Nernst’s (1864–1941) heat theorem, states that all processes come to a stop (and entropy shows no change) only when the temperature nears absolute zero (–273°C). "
18 " Energy is not a single, easily definable entity, but rather an abstract collective concept, adopted by nineteenth-century physicists to cover a variety of natural and anthropogenic (generated by humans) phenomena. Its most commonly encountered forms are heat (thermal energy), motion (kinetic or mechanical energy), light (electromagnetic energy) and the chemical energy of fuels and foodstuffs. "
19 " The efficiency of energy conversion is simply the ratio of desirable output to initial input. "
20 " The SI specifies seven fundamental measures: length, mass, time, electric current, temperature, amount of substance, and luminous intensity. "