The human race, in its never ending struggle to improve its standard of living, has invariably depended on colossal amounts of electric power to fuel our evolution. A present day estimate by National Geographic determined that we use 320 billion kilowatt-hours of energy every day. Today, most of this enormous requirement is addressed by burning fossil fuels. So far, fossil fuels have catered to our energy needs very efficiently, but they are also non-renewable and rapidly depleting. These fuel sources have also contributed greatly to greenhouse gas emissions and pollution. The time has come to find suitable and better replacements for fossil fuels. Scientists are constantly researching newer and greener sources of energy that have limited impact on the environment and reduce their contribution to global warming, which is believed to be caused by the release of carbon dioxide while burning fossil fuels.

Atomic energy, solar energy, and energy from wind and bio fuels are just a few of the promising alternatives for a cleaner and greener future. Other relatively new sources of energy such as fuel cells, geothermal energy, and ocean energy are also being explored. In the following sections, we’ll take a look at current sources of energy as well as discuss possible future energy sources.

Fossil Fuels – Coal

Fossil fuels are the remains of dead plants and animals on land and in the seabed. These are formed from the fossilized remains of dead animals and plants that are exposed to heat and pressure in the earth’s crust for hundreds of millions of years.                             

Fossil fuels primarily consist of hydrocarbons. They contain carbon and hydrogen in varying ratios, such as methane, that has a low carbon to hydrogen ratio, or anthracite coal, which is almost pure carbon. Hydrocarbons are formed when the fossilized remains of dead organisms are chemically altered over hundreds of millions of years by intense pressure and heat found in the earth’s crust. The chemical energy ‘stored’ in these fuels is released during combustion to produce electric power.

According to estimates provided by the Energy Information Administration, fossil fuels account for 86% of the total energy produced in the world. Of this, petroleum accounted for 36.8%, coal 26.6% and natural gas 22.9%.

However, fossil fuels are non-renewable sources of energy. They take hundreds of millions of years to form and are depleted much faster than new reserves can be created. It is estimated that 23.5 tons of fossilized organic material deposited on the ocean floor is required to produce 1 liter of gasoline. In 1997, the total amount of fossil fuel used was equivalent to plant matter that grew on the entire land and ocean surface of the earth over a period of 422 years.

Another disadvantage of our heavy dependence on fossil fuels is the amount of carbon dioxide produced during combustion, which is estimated at 21.3 billion tons per year. However, natural processes are capable of absorbing only about half of the total amount of carbon dioxide emissions released into the atmosphere, which means every year the amount of carbon dioxide in the atmosphere                            Photo credit - The Generator Judge
is increasing by 10.65 billion tons, which is theorized to be the leading contributor to global warming that could potentially have very adverse effects on the ecosystem.  

Fossil Fuels – Natural Gas

Natural gas is usually found along with fossil fuels, in coal-beds and trapped in other types of rock. It is created by methanogenic organisms present in landfills, marshes and wetlands. It naturally consists of methane and small amounts of other gases such as ethane, propane, butane, pentane, hydrocarbons of higher molecular weight, sulfur, helium and nitrogen. The constituents of natural gas other than methane need to be removed before natural gas can be used as a source of fuel.  Read Natural Gas Generators: An Alternative to Diesel, for one example showing existing technology using a natural resource, one that is better for the environment, as fuel.

Although natural gas is considered to be cleaner than other fossil fuels, it has still been found to contribute to pollution and global warming. While it can be used to supplement the world’s ever depleting reserves of traditional fossil fuels, it is not a 100% clean, non-polluting alternative. In 2004, carbon dioxide emissions resulting from the use of natural gas stood at 5,300 million tons while coal and oil contributed to carbon dioxide emissions of 10,600 million tons and 10,200 million tons, respectively. However, this trend is expected to reverse by 2030 when natural gas is likely to emit 11,000 million tons of carbon dioxide as opposed to 8,400 million tons from coal and 17,200 tons from oil at that time. Also, when released directly into the atmosphere, natural gas is a far more potent greenhouse gas than carbon dioxide but since this occurs in very small amounts, it is currently not a major cause of concern.

Solar Energy

Almost everything in this world ultimately derives its energy from the sun. Instead of obtaining the sun’s energy from indirect sources like fossil fuels, researchers and organizations worldwide are looking to directly tap this unlimited source of energy.

The earth receives about 174 billion megawatts of power at the upper atmosphere as a result of solar radiation. About 30% of the incident solar radiation is reflected back, while the remaining, which amounts to 3.85 x 1024 Joules every year, is absorbed by the atmosphere, oceans and landmasses. The amount of solar energy that is available to us during an hour is more than the total amount of energy consumed worldwide in an entire year. But this is a diffused, rather than concentrated, form of energy and the greatest challenge lies in harnessing it.

Heat and light radiation from the sun can be harnessed through the use of semiconductor solar panels. The energy solar radiation excites electrons on these panels and leads to the production of electrical energy.
 
One of the biggest hurdles in harnessing the energy from the sun is in building cost-effective solar panels. The cost of solar power is about US 8–15 cents per kilowatt-hour as compared to the cost of coal-based electric power at US 6 cents per kilowatt-hour. 

Proper storage of energy is another major obstacle. Solar energy is not available at night but modern energy systems usually assume continuous availability of energy. Thermal mass systems, thermal storage systems, phase change materials, off-grid photovoltaic systems, and pumped storage hydroelectricity systems are some of the ways in which solar energy can be stored for later use.

Even with all of the technological advancements, solar energy technology is still in its infancy. Until we perfect the technology and are able to harness and store solar energy in a viable and cost-effective manner, fossil fuels will continue to be the most commonly used source of energy.

Nuclear Energy

As the worldwide demand for power continues to surge, nuclear energy is gaining increasing importance as a clean source of power that is expected to address the global issue of climate change. Volatility in the prices of fossil fuels and the increasing concern of nations to secure energy supplies are other drivers of nuclear energy.

There are currently 439 nuclear power reactors operational in 30 countries worldwide. This accounts for 14% of the total power generation of the world. The International Atomic Energy Agency (IAEA) expects the global nuclear power generation capacity to increase from the current 372 gigawatts (GW) to 437–542 GW by 2020 and to 473–748 GW by 2030. However, for nuclear power to emerge as a reliable and clean source of energy, several challenges need to be addressed. Some of these include improvement in economic competitiveness, designing safe and reliable nuclear power plants, management of spent fuel and disposal of radioactive waste, developing adequate skilled workforce, ensuring public confidence in nuclear power, and ensuring nuclear non-proliferation and security.  

Nuclear energy is harnessed by either splitting (fission) or merging (fusion) the nuclei of two or more atoms. Nuclear fission usually uses uranium in the process of harnessing energy. At our current rates of consumption, the uranium found in the Earth’s crust can last us about a century. However researchers predict that the energy consumption will triple in the next century, which means that the available uranium resources will only last us for approximately 30 years. One option is the reprocessing of the spent fuel. This spent fuel is rich in plutonium and when combined with the leftover uranium, it can be reprocessed into a mixture known as MOX, which can be used as fuel. This may help to stretch the available uranium resources by a few more decades. The biggest drawback to this source of energy is the disposal of radioactive waste and the high cost of building nuclear power plants.

Nuclear fission, on the other hand, could be the answer to our energy problems. Fission utilizes hydrogen isotopes, lithium, and boron. The lithium reserves from the earth, combined with those from the sea, can last us for more than 60 million years. Deuterium, an isotope of hydrogen, can last another 250 million years. However, the process of harnessing energy from this isotope is fairly complicated and is still in its infancy. If we can successfully learn how to utilize nuclear fusion for the generation of energy in a viable manner, it could well be the new king of the energy world. Nuclear fusion is a clean process, with low carbon dioxide emissions, and the radioactive waste products also have a relatively short half-life.

Wind Energy

Wind farms are constructed to harness mechanical energy from the wind and convert it into electrical energy. These wind farms are then connected to electrical power transmission networks for the distribution of power. On average, only 20 to 40 percent of the total energy capacity of a wind farm can be utilized.

The limiting factor in harnessing energy from wind is that wind speed is variable and in most cases the energy from wind can only be effectively harnessed with very high wind speed and consistent heavy winds. These generally occur at higher altitudes. Wind energy also requires large, open expanses of land in order to construct wind farms.

In 2008, the worldwide wind power generation capacity stood at 121.2 GW. On an average, wind power currently accounts for only 1.5% of the global power generation capacity. However, this sector has grown two-fold within the three-year period of 2005–2008. Wind power accounts for 19% of the total power generation in Denmark, 10% in Portugal and Spain, and 7% in the Republic of Ireland and Germany.

Biofuels and Biomass

These include fuel from plant and animal sources. Oil, or ethanol, obtained from plants such as sugarcane, switchgrass, algae, poplar, and corn can be used directly or mixed with other fuels such as commercial diesel and gasoline to provide power. Even plant matter such as dead wood, leaves, wood chips, and branches can be burnt to produce energy. This is typically classified as biomass. Biomass also includes any biodegradable waste from plant and animal sources which can be burnt for fuel.
 
The limiting factor in using bio fuels is that a large number of crops need to be grown to harvest the energy trapped in plants. This requires vast areas of fertile land. Additionally, not all plant sources offer a high yield. Experiments are underway to hybridize and genetically alter these crops to make them more robust and increase their yield. Biofuels are very promising for small-scale use as they are low on greenhouse gas emission, are an effective waste management system, and produce little air pollutants.

With the advancement of new technology and the development of new insights into our surroundings, scientists have been able to come up with even more adventurous power options. These include fuel cells, geothermal energy, and tidal and wave energy, to name a few.

Fuel Cells

Fuel cells are similar to batteries but use reactants from an external source, as opposed to batteries which are self contained. If the fuel and oxidant levels in fuel cells are properly maintained, power can be generated almost continuously. The efficiency of fuel cells is proportional to the power being drawn from it. They are also lightweight and extremely reliable.

Geothermal Energy

The interior of the Earth contains a lot of heat. Shallow regions contain hot water, rock and steam. Deeper inside, the magma is intensely hot. This heat can be harnessed to produce electrical energy and drive various applications. Harnessing geothermal energy requires no fuel and minimal land. It is relatively cheap and a very sustainable source of energy since the amount of heat contained in the earth bed is so vast that even if we harness more energy than we require, it will still suffice for millions of years to come.

Oceanic Energy

The oceans are vast and contain huge amounts of energy in the water currents, and thermal and salinity gradients. The energy from tides and waves can be harnessed to produce electrical energy. The differences in temperature that occur with varying depths can be used to drive heat engines, which in turn produce electric power.

The osmotic pressure difference between salt water and fresh water can also be used to generate electricity. Although most of these methods are still in the experimental stages, if researched properly, they can be a breakthrough for mankind. The oceans may well be able to quench our thirst for energy and bag the crown as the king of fuels.
 Energy from Antimatter:

One of the most complicated theories of producing energy is the idea of using matter and anti-matter to generate electric power. Antimatter is the opposite of matter. If matter is comprised of particles, anti matter is comprised of anti-particles.

cientists propose that if matter and anti matter were to collide, they would annihilate one another and release vast amounts of energy. However, this is still a theoretical source of energy. Whether anti-matter exists in some part of the universe and can be harnessed in some way is still a mystery to humankind.

There are various ways of extracting energy from the earth that humankind has discovered and used to its advantage. As the human race evolves, we will continually search for newer, more efficient forms of energy that have the least amount of impact on the environment. At present day, the most economically efficient fuel has proved to be oil.

In the future, when the world’s oil reserves are depleted, we will use another source of energy; possibly one that is mentioned above. However, the fact of the matter is that we must be proactive in researching new forms of energy to continue the advancement of civilization and to ensure a high quality of living that we all have grown accustomed to.