Comparative Energy Consumption
All told, the people of the world buy, trade, and sell a little less than 85 trillion (8.5 x 1013) kilowatt-hours of energy per year. But thats just the commercial market.
Because there is no way to keep track of it, it is not certain how much non-commercial energy people consume: how much wood and manure people gather and burn, for example; or how much water individuals, small groups, or businesses use to provide mechanical or electrical energy. Some think that such non-commercial energy may constitute as much as a fifth of all energy consumed. But even if this were the case, the total energy consumed by the people of the world would still be only about one (2.5 x 1013) kilowatt-hours per year. This translates to more than 260 kilowatt-hours per person per day. This is the equivalent of each of us running more than one hundred 100 watt bulbs all day, every day.
Per person, the US consumes
33 times that consumed on average by a person in India
13 times that consumed on average by a person in China
21/2 times that consumed on average by a person in Japan
2 times that consumed on average by a person in Sweden.
Yet, compared to the amount of solar energy falling on the land mass of the United States, the energy consumed as a nation could appear a mere trifle. Consider: setting aside less than 1% of U.S. land (an area about the size of two or three large counties in Nevada) and installing solar systems (such as solar cells or solar thermal troughs) that were only 10% efficient. Then, the sunshine falling on these systems could supply the U.S.A. with all the energy it needed.
In a certain sense, this is impractical. Besides being extremely expensive, you just cant take two or three counties and cover them with solar systems. The damage to ecosystems might be dramatic. But the principle remains. You can cover the same total area in a dispersed manner on buildings, on houses, along roadsides, on dedicated plots of land, etc.
In another sense, it is practical. We already dedicate more than 1% of our land to the mining, drilling, converting, generating, and transporting of energy. And the great majority of this energy is not renewable on a human scale and is far more harmful to the environment than solar systems would prove to be.
It would seem at first approximation straightforward to address the greenhouse problem by measures leading to a reduction in energy consumption.
Similar progress is evident on the supply side. For example, life extension of conventional plants, retrofitting of combustion turbines to combined-cycle operation, packaged combined-cycle plants, and steam-injected gas turbines have virtually fully supplemented central steam plants as utilities marginal supply investments of choice. With good design and favorable local conditions, hydro-plants, hydro-upgrading, wind-power, and certain forms of geothermal and solar-thermal-electric power can be highly competitive. Other options, such us fuel cell and photovoltaic, are rapidly coming over the horizon of competitiveness.
Extracting coal from underground used to be a risky and polluting business even in the 15th century, but the burning of such coal then represented only a minor nuisance to the environment. Today, the burning of immense quantities of coal, oil, gas and fuel wood represents a serious environmental threat. Quite apart from the greenhouse gas emitted, the sulfur and nitrogen dioxide which result from the burning of fossil fuels, are the main causes of smog, acid rain, and the variety of other disturbances to our environment. CO2, which can not be filtered or easily captured, is responsible for 49% of the greenhouse effect.
Renewable energy technologies are capable of contributing significantly in each of these areas. Depending on their locations, users who insist on high efficiency can demand buildings that extensively incorporate solar energy and natural ventilation to reduce energy demand by 40 to 80% compared with conventional buildings. A more efficient electricity generation and transmission network will increasingly rely on renewable sources of power that match demand requirements closely and can be added in small increments.
Because renewable energy technologies can make liquid fuels and produce heat or electricity, substitution for fossil fuel consumption can occur in every economic sector for nearly every application. Commercial experience with already deployed renewable energy technologies confirms the ability of these systems to compete with fossil energy systems in certain applications. Indeed, in some applications, renewable energy technology has become the preferred system.
Finally, renewable energy technologies can figure in carbon fixation and sequestering strategies. For example, technology has been developed that will harvest and combust whole trees from energy plantations. Using genetically selected strains of fast-growing trees, such a system eliminates the need for chipping or chunking wood, and the net effect of this energy from biomass cycle is CO2 absorption, plus elimination of sulfur dioxide emissions that cause acid rain.