Table 2.1 Inherent Characteristics of Primary Energy Sources ENERGY SOURCE PHYSICAL PROPERTIES STORABILITY FUTURE AVAILABILITY Fossil Fuels: Oil • liquid form with different grades • refining required to separate grades • heat of combustion = 4.3 x 107 J/kg • easily stored, • infrastructure (tanks) needed • monitoring required • finite resources; 100-200 (1012 Watt-Yrs) • recovery from shale oil and tars increasingly expensive Gas • low density gas • energy content similar to oil • easily stored • large volume tanks with safety monitoring (esp. for leaks) • finite reserves; 70-170 (1012 Watt-Yrs) Coal • solid with variable composition (esp. sulfur content) • heat of combustion = 3.0 x 107 J/kg • easily stored with little infrastructure (it can be stored in piles outdoors) • large reserves of varying quality; 670- 1000 (1012 Watt-Yrs) Nuclear: Fission • Heat production from Uranium238 = 8.1 x 1013 J/kg • special handling and storage procedures • significant quantities in small number of places; 3000 (1012 Watt-Yrs) Fusion • very high energy content • prepared fuel easily stored in tanks • technology currently unavailable • possibly long duration source Renewable: Solar • approx. 1.0 kW/m2 at sea level during clear days • clouds seriously reduce availability • not storable, external devices (e.g. batteries) needed, usually with significant reduction in efficiency • the sun will continue to burn for 5-10 billion years • solar radiation falling continuously on Earth's land area; 28,000 (1012 Watts) Biomass • variable composition and energy content (oil, alcohol, plant material) • low energy density • infrastructure required • oil and alcohol stored in tanks, dry plant matter in bins or silos with monitoring • indefinite as long as land, water, and sun are available; world max. supply; 13 (1012 Watts)
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