Not
all power is electrical
Hydroelectric power Electrical power from heat engines
Electrical power in the US |
In common parlance, people often
regard
power as meaning electrical power. In physics
and engineering, the term power refers simply to work per unit time
(and sometimes, heat per unit time).
In the United States, some of our electricity comes from 3347 hydroelectric dams. The gravitational potential energy of water into rotational energy of a turbine, thence into electricity, is about 85% efficient. Overall, 1.05 X 10^18 Joules (1.05 exajoules, EJ) of water energy was used in 1995 by hydro plants. Most of our electricity comes from heat engines --- mostly steam engines. The conversion of heat to work is notoriously inefficient (due to laws of physics, not because of engineering failure). The energy consumed by all non-hydro plants in the US in 1995 amounted to 9.72 10^18 joules (9.72 EJ). Overall, the around-the-clock average electrical power consumed in the US is 343 X 10^9 watts (343 billion watts, 343 gigawatts, 343 GW). |
