Fossil-based fuels (oil, coal, and natural gas) currently provide about 85% of all the energy use both in US and worldwide. These resources are being constantly depleted and can't be replaced within any practical time span. People often wonder how long exactly would they last? The remaining amount of a particular resource is often characterized by so-called Reserves-to-Production ratio (R/P). In plain language, R/P basically gives us the length of time the reserves would last if their usage continue at the current rate. Here are estimated world total R/P ratios for the main conventional fuels: oil - 46 years, natural gas - 58 years, coal - 118 years2. Of course, the usage is constantly changing and once in a while new deposits are found. That's why the above numbers are corrected every year.
Aside from being finite, energy production from fossil fuels results in by-products of combustion, or emissions. These emissions affect our environment and may be causing the climate change. In contrast, renewable energy (RE) resources, as the name implies, are constantly replenished naturally and will never be exhausted. Their use generally has a much lower environmental impact than that of conventional fuels. That is why the technologies that utilize them are often called "green". In addition, RE can boost US energy security by reducing our dependence on the imports. All these factors, coupled with the government incentives and mandates, result in growing interest in using alternative sources of energy. While some green technologies are large-scale, many of them are also suited to private homes, especially in rural areas. This website provides quick renewable energy comparison information with emphasis on its home use and cost.
THE RENEWABLE ENERGY SOURCES LIST
RE is derived from various natural processes, such as the Sun's electromagnetic radiation, tides or heat generation within the Earth. Here is a list of the main types of practically utilized alternative energy sources:
the solar photon flux can be converted to heat, electricity or chemical energy;
Wind: the motion of air molecules can be harvested in wind turbines that spin the shaft of electric generators or in windmills;
Biomass: organic materials can be used for cooking and heating, as well as to produce electricity and liquid transportation fuels;
Water: potential and kinetic energy of flowing water can be tapped to produce electricity or mechanical tasks.
Note that there is some controversy about classification of nuclear power. Usually it is excluded from the list of renewables. However, it is known that rivers eroding the Earth crust replenish Uranium dissolved in seawater. Also, nuclear fission in so-called breeder reactors creates more fissile isotopes than it consumes. So, although technically raw nuclear fuels are finite, because of their enormously large amount and because of the above replenishing processes, they might be considered RE as well. After all, biofuels are finite too, but they are treated as RE.
ADVANTAGES AND DISADVANTAGES.
Not surprisingly, each method of power generation has its pros and cons. RE of course is inexhaustible and environmentally friendly. It has another important advantage. Small individual power generators that are integrated into the grid reduce the impact of blackouts caused by a failure of centralized equipment or distribution lines. The distributed power technologies in general improve the overall system security.
Notwithstanding their clear benefits, all forms of RE have their disadvantages too. Renewable resources are not always available where and when they are needed. For example, hydropower resources are limited by geography and are often located in remote areas. They require installation of expensive electric lines to the cities. Solar and wind power are intermittent by nature. Which brings us to another major technical issue with RE: the storage. One of the problems of electricity is that it cannot be efficiently stored in large quantities for later use. It is unpractical for example to have a battery backup in a gigawatt-scale power plant. Also, while RE systems generally do not
produce as much air pollution as fossil fuels, they too have a certain negative impact on the environment. Finally, RE is still more expensive that traditional one. All the above factors are limiting the growth of RE. Currently, the share of renewable energy sources in net energy production is only about 10% worldwide and 8% in the United States.
While raw forms of energy are both free and practically infinite, the equipment and materials needed to collect, process, and transport the energy to the users are neither one. Currently, the RE costs are generally higher than that of fossil-based and nuclear energy. In addition to this, unlike well-established conventional designs, the advancement in different RE technologies still requires substantial investments. The economists often use so-called levelized energy costs (LEC) when comparing different technologies.
The LEC represents the total cost to build and operate a new power plant over its life divided to equal annual payments and amortized over expected annual electricity generation. It reflects all the costs including initial capital, return on investment, continuous operation, fuel, and maintenance, as well as the time required to build a plant and its expected lifetime. This table compares the US average levelized electricity cost in dollars per kilowatt-hour for both non-renewable and alternative fuels in new power plants, based on US EIA statistics and analysis from Annual Energy Outlook 2011. Note, that the numbers for each source are given for a different capacity factor, which
complicates direct comparison. Notwithstanding, I believe these figures are useful in comparing different power generation methods. Also note that the values shown in the table do not include any government or state incentives. In other words, they represent the actual cost to the society. We can see that so far coal and natural gas are the most economic fuels. However, in future the price of coal-based electricity can nearly double due to government imposed cost on CO2 emissions. Photovoltaic systems can be three times more expensive than fossil-based ones. The values in the chart represent just the cost of electricity production- the retail prices of course are always higher.
In conclusion, it is our responsibility to advance alternative power. However, we should remember that low-cost electricity generation is crucial to the economy. It increases income and employment in all sectors, the purchasing power of the consumer, and makes U.S. exports more competitive. RE certainly can supplement conventional power, and its use will likely continue to steadily grow. Nevertheless, realistically speaking, it can't entirely replace non-renewable fuels anytime soon.