Alternative Energy Scenarios for the 21st Century: Options for Wind Energy

By Crissaris Sarnelli

Introduction

Each year, carbon dioxide emissions in the United States increase at a rate of about one-percent per year (1). This increase is partly due to the increase in burning of fossil fuels by human beings. The burning of fossil fuels emits the greenhouse gas carbon dioxide. Carbon dioxide, in turn, traps heat in the atmosphere. Unfortunately, this is affecting global climate and making the world warmer. The United States is a large contributor of fossil fuel burning and is responsible for approximately 25% of carbon dioxide emissions and therefore contributes to Earth's warming. Letting fossil fuels burn at a yearly growth rate of 1.5% (2) as the business-as-usual scenario assumes will result in a continuation of the Earth's warming at the current rate. The business as usual scenario assumes that energy demand and fossil fuel burning will continue to increase in the future. The Intergovernmental Panel on Climate Change (IPCC), as well as other organizations, uses this scenario when it looks at future energy planning Our research is concerned in proposing an alternative scenario to the business as usual.

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We researched existing energy sources hoping to find ways to making the warming of the Earth in future years more moderate. We looked at the possibility of conserving electric energy. We looked to making the major energy provider, fossil fuels, more efficient as well as to increasing the use of other renewable and alternative energy sources, such as hydroelectric and wind power, that do not emit carbon dioxide into the atmosphere. We found that electricity contributed 40% of the energy use in the United States (Chart 1). Coal burning is responsible for 80% of the carbon dioxide that comes from electricity (2) (Chart 2). We realized that coal used in electricity production was significant in the emission of carbon dioxide and therefore a good starting point when looking for the reduction of CO₂ emissions in electricity generation.

The combination of conservation, a more efficient fossil fuel use and the increased use of renewable and alternative energy sources would create the alternative scenario where carbon dioxide emissions would be reduced significantly and not increase in growth in the electricity sector. This would result in a zero percent growth rate of carbon dioxide in the United States in that particular sector and could open the doors to other energy use sectors. In order to achieve the zero percent increase or less in CO₂ emissions within the next few decades while fulfilling the energy demand of the future, quantified data needs to be collected and transformed into an efficient plan including costs of new technology. Certain things needed to be known in order to create the new scenario. These were: the amount of energy conserved by the renewable and more efficient energy sources, the amount of people it can support and the possible CO₂ that would not be emitted into the atmosphere. This is what this research focuses on. It focuses on researching energy conservation methods and increased efficiency of existing fossil fuels because increased efficiency decreases carbon dioxide emissions.

Different renewable and alternative resources that do not emit CO₂ were also researched to see how much their use needed to be increased in order to meet future energy demands. It could be possible to decrease carbon dioxide emissions if there is more conservation and fossil fuels become more efficient. With the increase of renewable and alternative energy sources, the reduction of carbon dioxide emissions could be faster. Each renewable and alternative source produces electricity in a different way but in the process emit little or no carbon dioxide. The renewable and alternative energy sources we researched we geothermal, wind, solar, hydroelectric, biomass, and nuclear energy.

Geothermal energy can produce electricity in three different ways: with dry steam power plants, flash steam power plants, and binary-cycle power plants. All three have similar mechanisms but the one that is most promising for the future is the binary-cycle plant because it uses moderate temperature water, which is by far the most abundant source, and because it emits virtually no gases due to its closed loop system. Although it only currently provides energy for a small population of people in the United States, it has the potential to support many more according to a study that found 271 more sites where geothermal energy could be produced.

Wind energy is produced differently. It produces energy with turbines that emit no carbon dioxide. In one case, 150 wind turbines were able to meet the energy needs of 53,000 homes. According to the American Wind Energy Association, if .6% of the United States was used for wind turbines, the turbines could provide 20% of the energy needed in the United States.

Solar energy is produced by the direct contact of the Sun's rays with photovoltaic cells. During the manufacturing and installation of this energy some emissions are produced. After this there are no more gas emissions. According to a solar energy organization, if .5% of the United States was utilized for solar energy, solar energy could provide all of the energy for the United States. This could be very costly, however.

Hydroelectric energy produces energy from turbines in dams. Although hydroelectric power does not emit CO₂ it does have a negative environmental effect when it comes to the fish living in those waters. Hydroelectric produces about 95,000 megawatts of power and is the second largest renewable energy source.

Biomass energy is made of organic wastes such as municipal solid waste, wood grasses, ethanol gas and such. Biomass is the largest renewable source and produces only small amounts of carbon dioxide.

Nuclear energy has the largest energy production potential (20% of electricity) but currently only produces 8% of the United States energy. This is a promising source but public opposition to this energy source as well as the issue of where to dispose the waste is a factor in the possible slow increase of this energy source.

With these non-fossil fuel energy sources, along with energy conservation and increase energy efficiency, the United States could slow the growth of carbon dioxide to a 0% rate or lower. The different strategies to achieve this goal each have its pros and cons. Quantitative information is needed in order to understand each strategy and figure the best possible way to achieve the goal.

Will we have enough energy to supply the increasing population's energy demand while keeping the Earth from warming at extreme levels with these alternatives and solutions? Will we have sufficient information to make effective and informed actions when trying to reduce carbon dioxide emissions?

Methods

Instead of having fossil fuel emissions continuing to increase at today’s rates along with the increasing energy demand, the scenarios we developed would increase conservation and energy efficiency efforts. There would also be a decrease in fossil fuel emissions (specifically coal in electricity generation) by increasing the use of renewable energy sources in electric energy production.

In order to make these scenarios possible and plausible, we needed to obtain quantitative, reliable data on conservation efforts, energy efficiency levels, renewable and alternative energy sources, energy production, and carbon dioxide emissions dating back a few decades. The data needed to go this far back in order for us to see past trends to be able to deduce possible future trends. Most of our data came from the Department of Energy (DOE) statistics from the year 1989-1999. From them we obtained data sets on carbon dioxide emissions, energy production for electricity, and total United States energy production.

For energy conservation information we looked at work done by Edward S. Rubin from the Department of Engineering Policy and Department of Mechanical Engineering (3). According to Rubin, with certain measures taken (mitigation options) it would be possible to decrease greenhouse gases, immediately, 10-40% at a zero net cost or at a cost saving. For each energy source, we obtained data on how each technology worked and the state of the technological development from various smaller Internet sites. We also looked at how much it cost to produce and maintain the technology, how much carbon dioxide it produced, how much carbon dioxide it stopped from getting into the atmosphere, how efficient it was and its potential to grow. How many people each energy source supported was also considered. The negatives, as well as the positive effects of each source were also noted. When looking at carbon dioxide emissions we took into consideration how much each source produced as well as total carbon dioxide emissions. All this information was needed in order to get the most accurate scenario.

Although we tried to get accurate data, each source had its limitations. The limitations in our data were that assumptions for future trends are not certain and the business as usual scenario assumes that all past trends would continue into the future. Another limitation was that the amount of carbon dioxide emission per unit of energy was not exact since it was based on calculations and not actual numbers and may change form one source to another. Another important limitation is that the DOE bases its data on survey replies and may not reflect total and exact energy information. A limitation in our part regarding the alternative scenarios is the accuracy of the calculations and estimates needed to compose a viable and precise scenario.

With the data obtained, we were able to calculate information and produce trends in order to facilitate our understanding of each energy source and its potential to help minimize the amount of carbon dioxide in the atmosphere. Since most of the renewable energy sources could only provide energy to power electricity, we decided to concentrate on reducing emissions that were used to produce electricity.

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The business as usual scenario was used as the base case. Data from 1970-1999 shows a growth rate of 1.9% per year in electricity production. This rate was assumed for the next 20 years in DOE future predictions. In the 1970s there was a reduced rate of energy production due to the oil crisis and from 1989-1999 the growth rate was actually 2.2% per year due to its unusually high-energy production. Based on this historical data we assumed the business as usual scenario to have a 2% per year growth rate from 1999-2020. All projections are from 1999-2020. Once the BAU scenario was established, we began to create the alternative scenarios. The purpose of these scenarios was to reduce carbon dioxide emissions in electricity production to a 0% growth rate or less while still meeting the energy demands of the BAU scenario. We developed 3 scenarios labeled conservative, moderate and optimistic. The levels of extremity were based on the level of carbon dioxide mitigation options (energy conservation) and efficiency improvements in coal production (Table 1). After this was done, we evaluated the potential reduction of carbon dioxide emissions by increasing the role of renewable and nuclear energy production. These non-fossil fuels were treated as one group so they could have a greater effect. From 1989-1999 the electricity net generation by these sources was collectively 2.8% per year growth. However, due to negative opinions on nuclear and hydroelectric power, we assume the lower rate of 2.5 % per year growth rate.

Results

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Each of the three scenarios produced different results due to their varying levels of action. In the conservative scenario (Table 1, Fig.1), mitigation options or energy conservation decreased carbon dioxide emissions by 10% over 20 years. This means that, every year, carbon dioxide emissions were reduced at a .5% reduction of carbon dioxide (Table 1). This scenario assumed a 5% improvement on coal efficiency and would reduce carbon dioxide emissions an additional 12% over 20 years. This would be a .6% reduction each year for 20 years. The nuclear and renewable energy contribution combined (which remained constant for all three scenarios) increased at a 2.5% per year growth rate. With this, carbon dioxide emissions could be decreased by an additional 6% over 20 years at a rate of .3% per year. With this conservative scenario carbon dioxide emissions can be reduced by 25.1% over 20 years from the BAU (Fig. 1). This reduction brings the carbon dioxide growth rate to a zero percent growth rate in the electricity sector and reduces total carbon dioxide emissions by 11.2% (Fig. 4)

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In the moderate scenario (Table 1, Fig. 2) there was a reduction of 20% of carbon dioxide over 20 years by mitigation options. This becomes 1% per year reduction of carbon dioxide (Table 1). The improvement in coal efficiency remained the same as in the conservative scenario (12% in 20 years). The non-fossil fuels also stayed the same. By the year 2015, the carbon dioxide emissions reach a 0% growth rate and then begin to decrease there after. This scenario reduces carbon dioxide emissions in electricity production by 33% (Fig. 2) and reduces total carbon dioxide emissions by 14.7% over the 20 years (Fig. 4).

The optimistic scenario (Table 1, Fig. 3) assumes the same reduction from mitigation options but an increased rate of improved efficiency from coal. The improved efficiency in this scenario is 10%. This becomes a 25% reduction in carbon dioxide over 20 years (Table 1). This is a 1.25% per year reduction. This scenario produces a 0% growth rate in carbon dioxide emissions by the second year. If this scenario is used it would provide immediate reduction in carbon dioxide emissions from electricity production 42.1% in 20 years (Fig. 3). It would reduce total carbon dioxide emissions by 18.7% (Fig. 4). At the end of this section is a chart listing the growth of carbon dioxide emissions at the end of 20 years in both electricity production and total carbon dioxide emissions (Table 2).

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Conclusion/Discussion

From the results we can observe that solely reducing carbon dioxide emissions from coal in the electricity sector is not enough to drop total carbon dioxide emissions in the United States to a 0% growth rate or less. Other sectors need to be looked into like agriculture and transportation in order to make a greater impact. However reducing carbon dioxide emissions in electricity production by reducing coal emissions and conserving energy we can significantly reduce carbon dioxide emissions in that sector and substantially reduce some of total carbon dioxide emissions in the future.

To effectively reduce carbon dioxide emissions in the atmosphere, more than one measure must be taken. A combination of different actions from different places would reduce emissions at a faster rate and, in the long run, turn out to be more effective. The combination we looked at when developing our scenarios was energy conservation (mitigation options), improved efficiency of coal combustion and the increased role of renewable and alternative energy sources.

We first looked at energy conservation because it can be done immediately and it is cost effective. For example, by switching 1978 refrigerators for 1999 refrigerators there would be a reduction of carbon dioxide emissions of one ton per year. Another example is if an annual electricity conservation of 1/3 from a family went from 9000 kilowatts to 6000 kilowatts, the approximate reduced carbon dioxide emissions would be 3.5 tons per year. This would have an approximate cost saving of $450 per year (NYC Consolidated Edison from July 2001). As can be seen, energy conservation has significant potential. There is immediate energy conservation potential in home and commercial buildings. Changes for more energy conservation could be applied to lighting, appliances, heating and cooling systems, and insulation.

Improved efficiency of fuel combustion, specifically improved efficiency of coal combustion would help reduce carbon dioxide emissions. This in combination with conservation could significantly reduce carbon dioxide emissions. Looking at improvement in coal efficiency is very important as there is a 200-year supply of coal in the United States and is a very cost-effective fuel. Since coal a very large supply and can last for a long time, improving its combustion efficiency could be vital. Currently, the average United States coal power plant works at approximately 35% efficiency. With the improved efficiency from 35-40% in our scenarios, carbon dioxide emissions could be reduced 12% and 25% over 20 years if efficiency improves from 35-45%.

The increased use of renewable and alternative resources is also a key part in the combination to reduce carbon dioxide emissions. To increase the use of these non-fossil fuels and reduce the use of fossil fuels, the cost of the sources need to be decreased and the renewable sources need to become more available. The combination of increased energy conservation, efficiency and usage of non-fossil fuels is needed to effectively decrease carbon dioxide emissions in the atmosphere. One thing alone cannot do the job.

Although we developed these alternative scenarios that assume a substantial reduction in carbon dioxide emissions from the electricity production, more research needs to be done to better reduce carbon dioxide emissions and to provide policymakers with the information they need to make informed decisions.

Although our alternative scenarios are one option to reduce carbon dioxide emissions, other research must be done in order to make the most effective choices. One major part that needs to be researched is the cost of achieving the alternative scenarios and the cost of each specific alternative and renewable energy source. Other energy use sectors like transportation and agriculture must also be researched to know their potential to decrease carbon dioxide emissions. They contribute to the total carbon dioxide emissions and must also be taken into consideration. The increased efficiency of non-coal energy sources must also be looked into. If it is possible, fuel switching could also be a choice. The continued research of all these options is crucial when looking at climate change. If something is not done to decrease carbon dioxide and other greenhouse gases in the atmosphere, the consequences of global warming could be extreme. With our proposed alternative scenarios for reducing carbon dioxide emissions, these consequences could be more moderate. However, it is very important that more quantitative data, like the one gathered in this research, continue to be gathered. Information like this is in demand by policymakers. They want to have as much information as possible before making decisions on energy policies, which can greatly affect the future of the Earth. This is why information like the type that we have obtained is important.

References

• (1) Hansen, James. An Open Letter on Global Warming. 25 Oct. 2000.
• (2) Department of Energy website: http://www.eia.doe.gov, July 2001.