The rapid growth of the world population leads to energy demand on a rise especially in developing countries. In addition, due to the limited ability to supply of non-renewable there are a number of huge challenges that are posed to the population of the world. This situation leads to the risk of depletion of cheap fossil energy and environmental pollution as well as climate change. According to Loir, there will probably be sufficient oil and gas for this century, and coal for 2 or more (Loir .N 2007, p.843). Or Edwin Cartlidge reports “the annual total consumption of energy sources by the world population is about 1.4×1017 kWh, of which the proportion of the fossil energy has accounted for 90% of the energy sources used” (Physics World 7/2007). Therefore, researchers around the world have been constantly trying to find solutions to diversify energy sources and reduce harmful emissions and greenhouse emissions into the environment and renewable energy sources have taken the spotlight. Thus, what is the renewable energy? The Oxford Dictionary () defines renewable energy as natural energy that can be used again and again and will never run out. There are four major types of renewable energy: solar, hydro, wind and geothermal energy.
This paper will discuss advantages and disadvantages that renewable energy resource (RES) brings, as well as analysis the importance of RES to the world’s future.
2. Discussion of findings
2.1 Advantages of renewable energy resources (RES)
The use of renewable energy has many potential benefits, including human beings and environment.
Firstly, one of the most important advantages of renewable energy is that it is renewable. Essence of RES is derivation from natural processes so the energy is sustainable and never run out. Truly, renewable energy is really important and necessary to human beings when fossil fuels are more and more exhausted. With the never-ending supply of renewables, we would feel secure when having abundant supply of energy to last our planet, our human race and our economies, for generations and ever. Khemani (2011) says: “As long as human life is there, there will be earth, sun, wind and water, and the energy from these sources will also be available as long as they are there”. With the abundance from many renewable resources and development of science and technology, he strongly believes that renewable energy can meet the world’s energy needs today and tomorrow.

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Secondly, another benefit of renewable energy technologies is that ability of providing a measure of assurance of continued electricity supply at times when it otherwise might be threatened. In some circumstances, renewable energy technologies can be more reliable than other forms of electricity. For example, solar electricity systems can be used after storms for response and recovery. Renewable energy technologies such as generators powered by photovoltaics (PV) can supply electricity if the grid fails. Often the sun comes out in the immediate aftermath of a devastating storm. It can take weeks to repair the electricity grid and restore power to all customers. If battery storage is added to the system, it can supply electricity even after the sun goes down or through several cloudy or stormy days.
Energy is needed to provide lighting, heating, air conditioning, cooking, transport and to power all the technologies in the family home or business premises (Parker 2010)
Moreover, renewable energy not only is regarded as an unlimited resource but also plays an important role to regional development. Renewable energy and energy efficiency can help revitalize rural communities. For example, Wind turbines and solar panel systems can provide energy and provide rural communities with new tax revenue. Farmers on windy lands can lease space to wind developers, earning thousands of dollars for each turbine every year.
One of the greatest alternative energy benefits is that it is so much better for environment than the use of fossil fuels that contribute heavily to issues such as acid rain, smog and global warming. On the contrary, renewable energy has little or no waste products such as carbon dioxide or other chemical pollutants. Renewable energy systems produce much lower carbon dioxide emissions as opposed to carbon-intensive fossil fuels such as oil, coal and natural gas while they are being used only a small amount of fuel during the manufacturing of equipment (Walser 2012). With renewable energies, energy is usually converted from one form to another without the creation of pollutants. Chandler (2006) takes solar energy as example, light energy from the sun can be converted directly to electricity using photovoltaic without the production of any pollutants like carbon dioxide or other greenhouse gasses. Similarly, wind power energy relies on moving air and converts it into electricity without polluting the environment. Therefore, it is obvious that the non-pollution or minimal impacts on environment are the positive advantages of renewable energy.
2.2 Disadvantages of renewable energy resources (RES)
Although it is obvious to recognize the human as well as environmental advantages of utilizing renewable forms of energy, we must also consider some limiting sides from the energy.
The biggest disadvantage of renewable energy is that the cost of the energy is relatively higher than non-renewable energy. The initial costs of renewable energy still make many people ignore it completely when comparing it with fossil fuel on two aspects: total cost and over the same time period. For example, installation of solar energy water heater costs many times in comparison with a heater, so they decided to buy heaters for hot water solution. According Global Wind Energy Council (GWEC) (2008) reported that turbine installation costs $ 47.5 billion; by contrast, we only have to spend a much smaller amount of money to build thermal power station about $ 2,25 billion (Shah 2011). He also pointed that other incidental costs such as maintenance costs and production costs cause price increasing. Generally, it is price that the reason has prevented approaching and using clean energy as compared to the fossil fuel sources of energy.
Another distinct disadvantage is relying too much on weather conditions and geographic locations to create energy (Sinclair 2011). Each types of renewable sources is just better suited to some places. This means that you cannot use each of these renewable sources in all locations. For instance, when using geo-thermal energy, you must be in a location that provides the environment for geo-thermal energy to be produced. Likewise, we cannot generate hydro-electric power without having a fast-flowing water source, such as a river or waterfall. In addition, the energy also brings some inconvenient problems. Take solar energy water heater as an example, it is inefficient because in summer ambient temperature are high and the use of hot water is not needed; however, in the winter we could not have hot water due to low light of the sun.
Shah (2011) claimed that “despite the fact that most renewable energy sources are more environmentally friendly they may still have a negative impact on the environment”. He stated that hydroelectricity projects can cause a dramatic change in the development of wildlife and ecosystem along the river and flood risks.
2.3 Can renewable energy supply the World’s energy needs?
With the significant benefits from renewable energy, we can’t deny that roles of it are more and more important. Nowadays, by advances and achievements of science and technology scientists are having every confidence in bright future of renewable energy. According to the report of The Intergovernmental Panel on Climate Change (IPCC) in 2011, renewable sources occupied about 13 percent of the world’s energy in 2008 and the proportion likely to have risen. The report also point out that within four decades renewable energy could account for almost 80% of the world’s energy supply. The statistics are completely appeared in the near future if we combine four main alternative resources and use hydroelectric to fill in gaps, which makes easier to match demand. “The most important thing is to combine renewable energy sources into a bundle” (cited in BERGERON 2011).
Particularly, in research (Edenhofer et al. 2011) shows that by 2050, geothermal energy could meet more than 3 percent of global electricity demand and about 5 percent of the global heat demand, hydropower will contribute about 30 percent of worldwide electricity supply, wind power will grow to more than 20 percent and solar energy becomes one of the major sources of energy supply with about 15 percent.