United States is rich in renewable energy. Renewable energy is a big topic to talk about, including how to well use these energy to save the world. Today I will focus on How much electricity can renewable energy contribute to the power system. In the recent year, Renewable energy installations are growing rapidly, especially wind power and photovoltaic power generation. But how the power system consume a higher proportion of the intermittent power? And if there a synergy between different types of renewable energy? If we Integrating the renewable energy in a larger area, how well it can help the power consumption? By the lead of the Massachusetts institute of technology( M.I.T.)and U.S. renewable energy laboratory, the U.S. department of energy laboratories, industry, university and government departments participated and complete the “Renewable electricity future study”. In the study, they analyzed with two models, which are “ Regional Energy Deployment System Model” and “ GridView Model”. This paper focuses on the influence of different generation ratio of renewable energy sources on power structure and transmission facilities, and also analyze the sequence when renewable energy take up 80% of the overall power generation. This study has great use of reference for the development of renewable energy in the United States and other countries. The development of renewable energy in the United States is constrained by many factors, including policy and institutional constraints, technological development level, market drivers and so on. It is difficult to accurately estimate the development of renewable energy in the future. So in the “Renewable electricity future study”, a dozen scenarios are analyzed. Considering there is a big chance that the proportion of renewable energy power generation take up to 80 percent of the power generation in the future, the paper does analysis under different scenario includes technology develop level, resource supply level and so on. Here is some detail of the assumption: First of all, Energy efficiency improves, and power demand growth is slowing down; second, improvements in renewable energy sources and performance, and it relates to current federal and state policies; third, the policy formulation of renewable energy is mainly restricted by existing laws; forth, the carbon emission reduction policies are not implemented, and air pollution regulations are the same as the current situation. In this scenario, conventional power sources develop rapidly and renewable energy is slow to develop. The demand for electricity relates to two factors: population growth and economic development. In the low-demand hypothesis, new technologies, positive social attitudes and related policies are the reason why energy efficiency have promoted. In this scenario, electricity demand will grow more slowly in the coming decades, and the demand of electricity is about 3.92 trillion kilowatt-hours in 2050. But in high demand assumptions with the energy efficiency at current levels, leading to a demand for electricity of 5.1 trillion kilowatthours in 2050. After all, the portion of renewable energy that can contribute in the power generation direct affect the future of it, and different scenario of collaboration of politics and technology can lead to a different outcome. The factor can affect the future of renewable energy is not only technology, but also policy. To have a better understand of the future of clean energy, let’s take a peek of the current clean energy policy. The current green energy policy is “ American Clean Energy and Security Act”, as known as ACESA. On June 26, 2009, the house of representatives passed the law by a narrow margin of 219 to 212. The bill contains more than have more than 1,400 pages of text, including five parts, which are clean energy, energy efficiency, reducing greenhouse gas emissions, transition to clean energy economy and agriculture and forestry. In the part of clean energy, this law required the generation enterprise which quantity sold more than 4 billion kW · h power need for developing in renewable energy generation and energy efficiency to meet the requirements of part of the electric power growth. In other word, by the end of 2020, renewable energy source (without water electricity) power generation will take up to 20 percent of total capacity, which is 14 percent more than the number in 2012. However, “Renewable electricity future study” conducted a different conclusion from the ACESA. It uses multiple scenario analysis to show us the policy doesn’t support enough for the development of the clean energy. Even under a low-demand core situation, the growth of Renewable energy power generation increase will only from 12% to 19.5% , from 2010 to 2050. In technology wise, knowing the power source structure is important. When the proportion of renewable energy increases in power generation, the energy source portion relatively change as well, as showing in Graph 1. A few outstanding changing components are: when renewable energy take up from 30 percent to 90 percent of the total energy generation, the onshore wind power has the largest expanded, which increases from 130 million kilowatt to 400 million kilowatt, of course the offshore wind power has expended as well, which is up to 110 million kilowatt; concentrating solar power has the ability of saving heat, it has big influence on the flexibility of power grind, up to 2050, concentrating solar power capacity grows from couple thousand kilowatt to 120 million kilowatt; with the coal-fired unit retires in 2050, biomass change from mixed-fuel burning to direct fuel burning; nuclear capability doesn’t have a big change, but power generating drop from about 11 percent to 5 percent. And the more detail changes have shown on the graph 1 below. *Graph 1 In 2050, the chance of renewable energy takes up 80% of the power generation is pretty big. However, it must be facing a lot of uncertainties in the developing phase. So simulate the result by assuming different uncertainties scenarios become very important for strategic analyzing, for example technology developed level, constraint on power transmission, constraint on flexibility of power grid or constraint on resources supply. In the “Renewable electricity future study”, under the low-demand core 80 percent RE scenario, the analysis for different constraint conditions was conducted. The detail will be shown on graph 2. In 80 percent RE-NTI(Renewable Electricity—No Technology Improvement), 80 percent RE-ITI (Renewable Electricity—Incremental Technology Improvement) and 80 percent RE-ETI(Renewable Electricity—Evolutionary Technology Improvement) these three scenario favored more on the technology that currently it is on an early stage, which most likely is solar power, especially CSP. In the 80 percent RE-ETI scenario, the growth of CSP was found to be particularly sensitive to scenario design, which yield the highest level of capability deployment, up to 130GW. Comparing to other scenarios, the technology that is mature today seems to be less deploying in the future, especially hydropower and wind power, they only hit the number respectively 81GW and 390GW. In the 80 percent RE-NTI scenario it relies on the current advanced technology, so on the opposite of RE-ETI, the wind and hydropower deployment has the largest scale, respectively up to 560GW and 170GW. Of course, the low level of deployment were witness for CSP capability and utility-scale PV capability, respectively only about 1GW and 5GW. In the scenario of transmission constrained, because of the constraint on the newbuilt facilities, the renewable energies that not rely on transmission were assumed to have a great development, which including rooftop PV, offshore wind and biomass. The level of deployment for rooftop PV is 180GW, for offshore wind is 170GW and for biomass is 98GW. In scale of contribution, it’s 15 percent, 16 percent and 10 percent. On the contrary, the generating technologies that reply more on transmission were imposed constriction on developing. The low level of deployment is observed in CSP and onshore wind power, their contribution is only 33GW, 28GW, respectively. In the scenario of flexibility constrained, the larger deployment of storage technologies are observed, such as CSP with thermal storage is deployed at high levels with 89GW in order to adapt the flexibility constraint condition. On the contrary, the utility-scale PV and wind power are in the relatively modest deployment levels, which is 64GW and 420GW, respectively In the scenario of resources constrained, because of the restriction of the location selection and the permission procedures, the low development of biomass, geothermal and hydropower are observed. However, the resources that spread all over the place have a rapid expansion, such as CSP and onshore wind power. In 2050, the deployment of CSP and onshore wind power reach 120GW and 40GW, respectively. On the contrary, the deployment of biomass, geothermal and hydropower are only 5.2GW, 1.2GW and 10.4GW, respectively. Graph 2 Of course, when The change in energy efficiency and power consumption policy is not obviously improving, it may lead to a substantial increase in the power demand in the future. For this reason, “Renewable electricity future study” carried out the scenario analysis of high-demand core 80 percent renewable energy as well. Comparing to the low-demand core 80 percent RE scenario (including 80 percent RE-NTI, 80 percent RE-ITI, 80 percent RE-ETI, resource constraints, transmission constraints and flexible constraint scenario), the total installation increased from 127GW ~ 147 GW to 193GW. Among all the scenarios, photovoltaic and offshore wind rise significantly, installed capability reach 420GW and 460GW, respectively. On the contrary, due to resource constraints, the proportion of water energy, biomass energy and geothermal energy are reduced. In conclusion, the abuse of the fossil fuel is getting more and more obvious, such as issues of the safety fossil energy, price of resources, storage of the resource, the effect on climate change, pollution and social issue. These all account for the constraint of fossil fuel. Accelerating the development of renewable energy has become an important choice for the energy strategies of all countries. In recent years, countries have launched a boom in renewable energy. However, it is difficult to accurately assess the impact of the future renewable energy development on the premise that the policy system, technological development level and market drivers are uncertain. So in the “Renewable electricity future study”, a series of situational analysis is conducted on various factors, which has an important impact on the development of renewable energy in the United States and the world. In order to raise the proportion of renewable energy power generation, the cooperate of the power source structure, transmission facilities, relevant policy government, financial support, etc. Every loop plays an unreplaceable role in this chain to the future. At the meantime, in the process of renewable energy development, it is important to balance the relationship between development scale and technology progress, social impact, environmental protection and market regulation and other aspects.
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