Currently, the world is suffering energy crises and entering a period of energy transition. And many people have recognized that the industrialized world must rely on renewable energy rather than fossil fuels. Although fossil fuels are the dominant energy source in the modern global economy for the past few centuries, which had helped drive the industrial revolution and promoted the material prosperity. However, fossil fuels will not last forever. The World Energy Council (WEC, 2004) suggests that we may only have 30-40 years' world of oil at current production rates, 50-60 years for gas and about 2000 years for coal. Furthermore, fossil fuels may cause a long-term adverse affect in the environment such as driving the climate change and affecting the carbon cycle. Therefore, the energy transition from one main energy source to a variety of renewable sources reflects a universal aspiration and an urgent demand of secure, affordable and environmentally acceptable energy. Biomass, hydroelectric power and wind power are three possible energy sources which are renewable and may replace fossil fuels in the future. This essay will first identify these three renewable energy sources and then assess their potential to replace fossil fuels on the criterion of efficiency, environmental impact and cost.
Biomass has a large potential to be used as a renewable fuel in the future. At present, biomass constitutes nearly 80% of all main renewable energy used worldwide in diverse way. Biomass is produced from living organisms or from metabolic by-products such as living plant and animal matter. It can be used by people for heating, lighting and cooking. In terms of efficiency evaluation of biomass, it can be transformed to the problem that whether a gallon of ethanol contains more energy than it takes to produce. Due to the complex nature of biomass production and use, it is difficult to evaluate it. In order to give a more legible evaluation, ethanol can be chosen as a typical example because they have become the dominant fuel of biomass in the modern world especially for the transportation. Herwick (2005) stated that the ethanol only contains about 2/3 of the energy content of gasoline. In order to be an environmental friendly energy resource, more complex processes are taken to produce ethanol than gasoline. It seems the efficiency of biomass needs to be improved in the future. However, biomass tends to be the most economical type of fuel. For instance, the price of ethanol has ranged between $0.90 and $1.90 per gallon over the past decades. Even the ethanol produced by a dry mill plant only cost $1.65 per gallon which is recorded in the book written by Demirbas(2009). The price of biomass will be lower if the energy efficiency is improved by the technology. By contrast, the price of fossil fuels is between $3.50 and $4.00 per gallon which is three times expensive than biomass. In terms of environmental impact, it seems there is a strong debate on the environmental impact of the biomass as biomass energy has a mixed record. On the positive side, Middleton (2009) stated that no net emissions of carbon dioxide are produced during the use of biomass as the amount released into the atmosphere by burning will be taken up by growing plants. However, on the negative side, the combustion of biomass can also contribute to pollution especially the indoor air pollution. The world health organization has found that in the air of homes, which burn biomass such as wood, charcoal, animal dung or crop waste for cooking and heating, concentrations of particulate matter are 20 times above the U.S. EPA safe levels. The chemicals and soot released by burning biomass can increase risks of diseases such as pneumonia, bronchitis and asthma. Though biomass energy brings a mix of benefits and drawbacks, biomass seems to have a great potential to make a contribution to world energy need with appropriate investing in technology and supporting from government.
Hydroelectric power has a vast potential to replace fossil fuel as it has been second in importance only to fossil fuel-generated electricity at present. Hydroelectric power is the second largest source of renewable energy and has accounted for 17% of the world's electricity production. Many nations with plenty river resources have built dams and hydroelectric plants in order to obtain large amount energy of hydropower, such as United States, Brazil, Norway, Sweden and China. This is due to diverse reasons. Firstly, hydropower seems to be the most efficient method to produce electric. For instance, the efficiency of hydroelectricity with each kilowatt-hour is twice than efficiency of any competing energy resource. Secondly, hydroelectric power is cleaner than fossil fuels as it does not discharge pollutants into the atmosphere. Although there some carbon dioxide may be produced during manufacture and construction of the project, it is a tiny fraction of the operating emissions compared with equivalent fossil-fuel electricity generation. Additionally, according to the project funded by the European Commission (2005), hydroelectricity produces the least amount of greenhouses gases compared to other energy sources such as wind, nuclear energy and solar power. Nevertheless, hydroelectric power has negative environmental impacts. Owing to the construction of the hydroelectric plants, marine and lake fish are prevented from accessing spawning grounds or the ocean. For example, Middleton (2008) indicated that the dams affect the population of salmon in the River Garonne. In terms of cost, there are two main parts can be taken into consideration. Firstly, it is the cost for building the dam. It seems this part of cost is high due to the complex technology for constructing a dam. However, the cost of operating a hydroelectric plant is inexpensive as it eliminates the cost of fuel. Furthermore, compared to a fossil-fired generation, hydroelectric plants tend to have longer economic lives. Although there are many drawbacks of hydroelectric power, the potential for hydroelectric power is thought to be great since there are three main advantages of hydroelectric power: clean, renewable and environmental friendly.
An enormous potential exists for wind power to replace the fossil fuel. Over past 30 years, wind power is the fastest-growing energy which has expanded at an astounding annual rate of 52%. Seitz (2002) highlighted that in the US about 1 percent of the energy was provided by wind in 2002. Wind power appears substantially more energy-efficient than fossil fuels. The devices which are used to harness power from wind are called wind turbines. Turbines can convert the energy of wind into kinetic energy in order to create electricity. Study indicated that wind turbines produced 22 times than they consumed, while for coal the ratio was 11:1. Besides, the design of the turbines can also affect the efficiency of the wind power in some extent. Currently, more efficient wind collectors are produced by modern technology. However, there are also defects in the efficiency of wind power. The most serious one is that wind power is an intermittent resource which means people can not control when wind will occur. It seems that the effects of wind energy on the environment are considered to be positive. Wind power is more environment friendly than fossil fuel. Wind turbines provide electrical energy without emitting greenhouse gases. For instance, the U.S. EPA has calculated that the release of more than 1500 tons of carbon dioxide, 6.5 ton sulphur dioxide and 3.2 tons of nitrogen oxides can be prevented by running a 1-megawatt wind turbine for only one year. Otherwise, wind energy has some downsides in environmental impacts. Wind turbines pose a threat to flying birds. For instance, birds were been killed by the rotating blades at California's Altamont Pass wind farm. In terms of the cost of wind power, it can be divided into start up costs and running costs. It should be stressed that start up costs for wind power is higher than plants driven by fossil fuels, but after the plants set up and running, wind farms incur fewer expenses. Hence it has been defined by the renewable energy Sources in 2004 that the purchase price for wind energy installation was 8.8 eurocents per kWh for the first 5 years and about 3 eurocents lower per kWh for the following years. In addition to, the technology improvements is driving down the costs of wind farms currently. In consequence, it seems that with the advancing technology and ongoing research, wind power has greatly potential to replace fossil fuels.
Overall, biomass, hydroelectric power and wind power all bring a mix of benefits and drawbacks. Firstly, in terms of efficiency, it appears that both wind power and hydroelectric power are high effective energies. Secondly, from a cost point of view, it appears that the biomass is the most inexpensive renewable energy resources though it may cause a series of environmental problem. Finally, according to the environmental impact, hydroelectricity seems to be the cleanest one as there are no carbon compounds being burned in the production of hydropower. In conclusion, the hydroelectric power seems have a long-term advantage in the comparison of environmental friendly and the efficiency. Furthermore, with the technology improvements which can drive down the set up cost, the hydroelectric power can considered to be an advantageous choice which can replace fossil fuels in the further.
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