There are many types of renewable energy. Most of them depend on sunlight. Wind and hydroelectric power are the direct results of differential heating of the Earth’s surface which leads to air moving about (wind) and precipitation forming as the air is lifted. Solar energy is the direct conversion of sunlight using panels or collectors. Biomass energy is stored sunlight contained in plants. Other renewable energies that do not depend on sunlight are geothermal energy, which is a result of radioactive decay in the crust combined with the original heat of accreting the Earth, and tidal energy, which is a conversion of gravitational energy.
The main types of renewable energy:
Solar. This type of energy relies on the nuclear fusion power from the core of the Sun. This energy can be collected and converted in a few different ways. The range is from solar water heating with solar collectors or attic cooling with solar attic fans for domestic use to the complex technologies of direct conversion of sunlight to electrical energy using mirrors and boilers or photovoltaic cells.
Wind Power. The movement of the atmosphere is driven by differences in temperature at the Earth’s surface due to varying temperatures of the Earth’s surface when lit by sunlight. Wind energy can be used to pump water or generate electricity but requires extensive areal coverage to produce significant amounts of energy.
Hydroelectric energy. This type uses the gravitational potential of elevated water that was lifted from the oceans by sunlight. Most of the available locations for hydroelectric dams are already used in the developed world.
Biomass (energy from plants). Energy in this type is commonly used throughout the world. Unfortunately, the most popular are the burning of trees for cooking and warmth. This process releases copious amounts of carbon dioxide gasses into the atmosphere and is a major contributor to unhealthy air in many areas. Some of the more modern forms of biomass energy are methane generation and production of alcohol for automobile fuel and fuelling electric power plants.
Hydrogen and fuel cells. Hydrogen can be burned as a fuel, typically in a vehicle, with only water as the combustion product. This clean burning fuel can mean a significant reduction of pollution in cities. Or the hydrogen can be used in fuel cells, which are like batteries, to power an electric motor. In either case, significant production of hydrogen requires abundant power. Due to the need for energy to produce the initial hydrogen gas, the result is the relocation of pollution from the cities to the power plants. There are several promising methods to produce hydrogen, such as solar power, that may alter this picture drastically.
Geothermal power. Energy left over from the original accretion of the planet and augmented by heat from radioactive decay seeps out slowly everywhere, every day. In certain areas, the geothermal gradient (increase in temperature with depth) is high enough to exploit to generate electricity. This possibility is limited to a few locations on Earth and many technical problems exist that limit its utility. Another form of geothermal energy is Earth energy, a result of the heat storage in the Earth’s surface. Soil everywhere tends to stay at a relatively constant temperature, the yearly average; and can be used with heat pumps to heat a building in winter and cool a building in summer. This type of energy can lessen the need for other power to maintain comfortable temperatures in buildings, but cannot be used to produce electricity.
Other forms of energy. Energy from tides, the oceans, and hot hydrogen fusion are other forms that can be used to generate electricity. Each of these is discussed in some detail with the result being that each suffers from one or another significant drawback and cannot be relied upon now to solve the upcoming energy crunch.
The geographical size of the ‘Renewable Energy’
Renewable energy resources and significant opportunities for energy efficiency exist over wide geographical areas, in contrast to other energy sources, which are concentrated in a limited number of countries. Rapid deployment of renewable energy and energy efficiency, and technological diversification of energy sources, would result in significant energy security and economic benefits. It would also reduce environmental pollution such as air pollution caused by burning of fossil fuels and improve public health, reduce premature mortalities due to pollution and save associated health costs that amount to several hundred billion dollars annually only in the United States. Renewable energy sources, that derive their energy from the sun, such as hydro and wind, are expected to be capable of supplying humanity energy for almost another 1 billion years, at which point the predicted increase in heat from the sun is expected to make the surface of the earth too hot for liquid water to exist.
Climate change and global warming concerns, coupled with high oil prices, peak oil, and increasing government support, are driving increasing renewable energy legislation, incentives, and commercialization.
Small solar PV systems provide electricity to a few million households, and micro-hydro configured into mini-grids serves much more. About 44 million households use biogas made in household-scale digesters for lighting and/or cooking, and more than 166 million households rely on a new generation of more-efficient biomass cookstoves. United Nations; Secretary-General Ban Ki-moon has said that renewable energy can lift the poorest nations to new levels of prosperity. At least 30 nations around the world already have renewable energy contributing more than 20% of energy supply. National renewable energy markets are projected to continue to grow strongly in the coming decade and beyond, and some 120 countries have various policy targets for longer-term shares of renewable energy, including a 20% target of all electricity generated for the European Union by 2020. Some countries have much higher long-term policy targets of up to 100% renewables.
The importance of Renewable Energy in the world
Renewable energy is important because of the advantages it provides. The key advantages are:
Renewable energy technologies are clean sources of energy that have a much lower environmental impact than conventional energy technologies.
Energy for our children’s children
Renewable energy will not run out. Ever. Other sources of energy are finite and will someday be depleted.
Jobs and the Economy
Most renewable energy investments are spent on materials and workmanship to build and maintain the facilities, rather than on costly energy imports. Renewable energy investments are usually spent within the country, frequently in the same state, and often in the same town. This means your energy money stay home to create jobs and fuel local economies, rather than going overseas.
For instance, after the oil supply disruptions of the early 1970s, United States had increased its dependence on foreign oil supplies instead of decreasing it. This increased dependence impacts more than just the national energy policy.
What are CO2 emissions and the importance of reducing them?
Carbon dioxide (CO2): Carbon dioxide enters the atmosphere through burning fossil fuels (coal, natural gas, and oil), solid waste, trees and wood products, and because of certain chemical reactions (manufacture of cement). Carbon dioxide is removed from the atmosphere when it is absorbed by plants as part of the biological carbon cycle.
There are both natural and human sources of carbon dioxide emissions. Natural sources include decomposition, ocean release, and respiration. Human sources come from activities like cement production, deforestation as well as the burning of fossil fuels like coal, oil, and natural gas.
Due to human activities, the atmospheric concentration of carbon dioxide has been rising extensively since the Industrial Revolution and has now reached dangerous levels not seen in the last 3 million years. Human sources of carbon dioxide emissions are much smaller than natural emissions but they have upset the natural balance that existed for many thousands of years before the influence of humans.
This is because natural sinks remove around the same quantity of carbon dioxide from the atmosphere than that produced by natural sources. This had kept carbon dioxide levels balanced and in a safe range. But human sources of emissions have upset the natural balance by adding extra carbon dioxide to the atmosphere without removing any.