Part I of this three-part series set the stage for examining intermittent power sources, especially wind, as viable sources of electricity. Part 2 addresses one of the critical power considerations: power density.

In his  MasterResource series, Vaclav Smil compared the power densities of a range of fuels for electricity production, which demonstrates the inadequacies of renewables. David MacKay also makes a useful contribution to this topic.[i] Table 1 summarizes the results, which take into account entire fuel cycles, transportation and transmission requirements for a range of assumptions.

Note that all renewable energy sources are ten to over a thousand times less effective than those serving our needs today, with wind providing one of the poorest performances of the renewable sources shown, outside of wood. Areas required for renewables are large because of the dispersed, and often remote, nature of their energy supply.…

Editor’s note: This is the conclusion of the series that provides an essential basis for the understanding of energy transitions and use. The previous posts in this series can be seen at:

Part I – Definitions

Part II – Coal- and Wood-Fired Electricity Generation

Part III – Natural Gas-Fired Electricity Generation

Part IV – New Renewables Electricity Generation

America’s dominant mode of electricity generation is via combustion of bituminous and sub-bituminous coal in large thermal stations. All such plants have boilers and steam turbogenerators and electrostatic precipitators to capture fly ash, but they burn different qualities of coal that may come from surface as well as underground mines, have different arrangements for cooling (once-through using river water or various cooling towers) and many have flue gas desulfurization to reduce SO₂ emissions.…

Photovoltaic Electricity Generation

Satellite measurements put the solar constant – radiation that reaches area perpendicular to the incoming rays at the top of the atmosphere (and that is actually not constant but varies with season and has negligible daily fluctuations) – at 1,366 W/m². If there were no atmosphere and if the Earth absorbed all incoming radiation then the average flux at the planet’s surface would be 341.5 W/m² (a quarter of the solar constant’s value, a sphere having four times the area of a circle with the same radius: 4?r…

Editor’s note: This is Part III of a five part series that provides an essential basis for the understanding of energy transitions and use. The previous posts in this series can be seen at:

Part I – Definitions

Part II – Coal- and Wood-Fired Electricity Generation

Boilers of electricity-generating stations burning coal can be converted to burn liquid or gaseous hydrocarbons (fuel oil, even crude oil, and natural gas) and such conversions were fairly common during the 1960s and the early 1970s. Burning natural gas rather than coal has clear environmental advantages (it generates less, or no, sulfur dioxide and no fly ash) but the overall conversion efficiency of the boiler-steam turbogenerator unit changes little. In contrast, gas turbines, particularly when coupled with steam turbines, offer the most efficient way of electricity generation.…