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G.P. Yeh, Fermilab
Sustainable energy can reduce challenges concerning energy, economy, environment, water, food, health, education, security and peace. The world energy consumption is equivalent to 15,000 Giga Watts (GW), by the world’s 7 billion people. The global carbon emission is 10 billion tons per year, or 1 million tons per hour . More than 1 billion people in the world have no electricity. Solar, Wind, and other renewable energies and energy efficiencies will continue their tremendous recent progress. Countries including Saudi Arabia and United Arab Emirates are significantly investing in renewable energies. The 400 nuclear reactors in the world, with an average age of 30 years, provide 2.3% of the world’s energy. To significantly provide sustainable energy and help reduce carbon emissions, nuclear power needs fundamental changes. US laboratories, universities, and companies can lead the world towards sustainable nuclear energy. Sustainable Energy is the greatest human challenge, responsibility, opportunity, andendeavor.
The world needs to reduce carbon emissions as soon as possible. As presented in the Africa Progress Report 2015, renewable energy is the key for African Development and Africa’s greathistoric momentin the next 10-20 years. The world needs to provide electricity and sustainable energy to all people.
In 2016, the world installed 55 GW of Wind Power and 75 GW of Solar, for a cumulative total of 487 GW Wind Power capacity and 303 GW Solar Power capacity .Worldwide investment in renewable energies in 2016 totaled US$242 billion (not including investment for hydro power). The United Nations, the World Bank, and partners worldwide are working on Sustainable Energy for All by 2030 . Japan is investing US$300 billion over 10 years towards renewable energy development . Chinais investing US $277 billion over 5 years to reduce air pollution .
1.1 WIND POWER
Wind Power has made tremendous progress in the last decade, adding about 45 GW per year since 2008, for a world total of 487 GW capacity by 2016 [3,7]. In 2016, China added 23 GW resulting in a total of 169 GW, US added 8.2 GW for a total of 82 GW capacity. Germany, India, and Spain had 50, 29, and 23 GW  wind power capacity, respectively. Japan, Korea, Taiwan had 3.2,1.0, 0.7 GW. Wind power provides nearly 40% of the annual electricity in Denmark and in the State of Iowa in US. Wind power has become the lowest price electricity in many countries . Each country could benefit greatly by installing more wind power. Offshore wind power has significantly reduced its cost, and is beginning in many countries. Wind power can supply 800 GW by 2021 , and thousands of Giga Watts (multi Tera Watts, TW) for world energy by 2050.
1.2 SOLAR ENERGY
Solar Energy is abundant, everlasting, and available to all worldwide, connected to an electricity power-grid or off-grid. The cost of Photo-Voltaic (PV) cells and Solar panels have decreased substantially, especially in last several years. In 2016, China, USA, Japan, India, and UK added 34.5, 14.7, 8.6, 4, and 2 GW installed solar power capacity, respectively. China, Japan, Germany, USA, and Italy had 78.1, 42.8, 41.2, 40.3, and 19.3 GW cumulative installed solar power capacity [3,8]. China is adding 50 GW in 2017, and already has 120 GW solar power. India plans 100 GW solar power capacity by 2022. The world is adding 100 GW solar power capacity in 2017.
The cumulative solar water heating capacity was 456 GW-thermal in 2016 [3,8]. Concentrating Solar Power (CSP) can also provide utility-scale electricity. Solar energy will providemulti Tera Watts for world energy by 2050.
1.3 HYDRO POWER
Well planned water system, including hydro power, can provide drinking water, flood control, irrigation, and electricity for the society. Hydro power capacity reached 1096 GW in 2016  and supplied 16.6% of world electricity generation. Small Hydro can benefit local communities. Hydro power can provide 2000 GW for world energy by 2050. Ocean Tidal, Wave, and Ocean Current Power are being developed, and will provide additional sustainable energy for the world.
1.4 BIO ENERGY
Bio energy can be close to carbon neutral. Bioenergy, including Biomass heating, Bio power, Ethanol and Biodiesel provide 14.1% ofthe world’s energy . Global Bio power generation was 112 GW in 2016 . To reduce food consumption for biofuels production, Cellulosic Ethanol has been in production in the last few years. Biodiesel development includes using algae. Bio jet fuel has been well tested by Boeing, Airbus, airlines, and military jets. Bio jet fuel is already being used, and will become increasingly important in the future.
1.5 OTHER RENEWABLE ENERGIES
Geothermal heat pumps can be used to heat and/or cool buildings. Geothermal heat can also be used as a heat source for various applications. Geothermal electricity power generation can be utilized in many countries worldwide.
Hydrogen produced from water electrolysis with wind power or solar power would be a clean fuel with zero Green House Gas emissions. Hydrogen fuel could be used for energy storage for wind power or solar power and/or replace fossil fuels. Germany and Japan have strong support for developing hydrogen vehicles.
Renewable energies, including Wind Power and Solar Power, now have competitive prices compared to the price of fossil fuels or nuclear power. Many companies, government branches, cities, states, institutions, universities have been purchasing renewable energies for up to 100% of their electricity consumption, including Microsoft, Intel, Kohl’s, Apple, Cisco,IKEA, Dallas, Houston, Starbucks, and Washington DC . Microsoft is purchasing 4.5 billion kilo-Watt-hours of Wind and Solar Power and Intel is purchasing 4.1 billion kilo-Watt-hours of Biomass, Small-hydro, Geothermal, Solar, Wind, Green Power for 100% of their annual electricity needs. Wind Power or Solar Power can also be used for seawater desalination to provide fresh water.
The Headquarters of the International Renewable Agency is in Abu Dhabi. Saudi Arabia is changing its economy to become less dependent on oil. France, UK, and Volvo expect to stop producing gasoline combustion engine cars by 2040s. Electric Vehicles (EV) have been making progress , with networks of large numbers of solar power or wind power charging stations in many countries. Most car manufacturing companies now also make electric and/or hybrid cars. Tesla is investing US$5 billion building a battery Giga-factory. Batteries for EVs will also be used for electricity storage for homes, businesses, utilities, and electric grids.
Improving energy efficiencies is the most cost effective component of energy solutions. LEDs, with 40-50% efficiencies which are 10 times the efficiencies of incandescent light bulbs in converting electricity to light, can save most of the energy used for lighting. Energy efficient appliances, buildings, power plants, factories, vehicles, public transportation, recycling,Smart Cities could reduce energy consumption by multi Tera Watts.
1.6 WORLD RENEWABLE ENERGY PROSPECTS
Wind Power in 2016 provided 4% of the world’s electricity or 1% of the world’s energy. Solar Power provided 1.5% of the world’s electricity. The annual increase of electricity from wind, solar, hydro, and other renewable sources is equivalent to electricity from adding ~50 nuclear reactors per year. Research and development continue to advance efficiencies, reduce costs, and further utilization of renewable energies. Solar, Wind, Hydro, Biofuels, each will provide multi Tera Watts by 2050. Geothermal, Ocean, Hydrogen, each will also provide additional energy.
The 403 nuclear reactors in the world together in 2016 provided 351 GW, which was 10.5% of the world’s electricity  or 2.3% of the world’s energy . Nuclear power has not had significant effect on the reduction of global carbon emissions. About 100 existing nuclear reactors will be decommissioned in the next 10 years because of their age . Especially because of the Fukushima nuclear crisis, Germany, Sweden, Switzerland, Italy, Belgium, Japan, Korea, Taiwan, Kazakhstan, Lithuania have reduced or minimized reliance on nuclear power. The world energy demand and consumption will increase in the next decades. To make significant contributions to world energy, nuclear power needs fundamental changes. The nuclear power inertia since 1950sis changing from conventional nuclear power to developing new generations of reactors including Molten Salt Reactors, Thorium Energy, and Accelerator Driven Systems.
2.1 NUCLEAR POWER CHALLENGES
Nuclear Power has 5 fundamental challenges: Safety, Proliferation, Waste, Cost, and Sustainability. The public is concerned about nuclear safety, especially after the Fukushima incident. Nuclear weapons should not be exploited again. Including the 2017 Prize, 9 Nobel Peace Prizes have been awarded to stop nuclear weapons. The world needs a permanent solution to eliminate nuclear waste. The cost of constructing new nuclear power plants is too high, except for a few countries, mainly China. The existing nuclear power plants and nuclear power technologies are not sustainable. To become one of the significant sources of energy for the world, nuclear power needs fundamental changes.
2.2 MOLTEN SALT REACTORS
Aircraft Reactor Experiment at Idaho developed the first Molten Salt Reactor in 1954-1955. Molten Salt Reactor Experiment  at Oak Ridge National Laboratory successfully operated in 1964-1969, including using U233 as fuel which can be obtained from Thorium. Molten salt coolant instead of water enables operation at lower pressure for better safety and at higher temperature for higher thermal efficiency, in comparison with conventional Pressurized Water Reactors. Molten salt fuel instead of solid fuel would provide additional safety. Liquid expansion due to unexpected higher temperature would reduce reactivity, and the liquid would be automatically and safely drained to an external container. There are laboratories, institutes, universities, and companies in US, China, Canada, and other countries developing and commercializing Molten Salt Reactors, including at Oak Ridge National Laboratory  in the US and at Shanghai Institute of Applied Physics in China.
2.3 THORIUM ENERGY
Thorium Energy could also provide multi TW of energy for the world for thousands of years. Thorium 232, chemical element 90, has a half-life of 14 billion years. Some of the advantages of Thorium Energy [15,16] over Uranium nuclear reactors are:
Molten Salt Reactor Experiment  successfully operated from 1964 to 1969, including using U233 fuel produced from Thorium. US, China, India, Russia, Netherlands, Denmark, Belgium, Germany, Turkey, other countries and some companies are developing Thorium Energy and Molten Salt Reactors . Russian President Putin in July 2016 ordered Russian nuclear institutes to develop Thorium technologies. Thorium Molten Salt Reactors may be demonstrated soon.
2.4 ACCELERATOR DRIVEN SYSTEMS
Particle accelerators have many applications . Low energy linear electron accelerators provide X-rays and MeV photons for radiation therapy. Higher energy electron accelerators can be synchrotron light sources or can provide X-ray free electron lasers for studying bio or nano materials. Proton, Antiproton, Heavy Ion, Electron and Positron accelerators have enabled Particle Therapies, Neutron Sources to study materials, nuclear physics studies, and high energy physics studies of quarks, leptons and other elementary particles and the fundamental forces of Nature.
2.4.1 Proton, Heavy Ion, NeutronParticle Therapy for treating patients with tumor
Protons and "Heavy Ion" nuclei ionize atoms along their path, with energy deposition described by the Bragg peak. Thus, Protons and Heavy Ion nuclei can deliver with higher precision more dosage to the tumor and less damage to normal cells in comparison with conventional (X-ray/photon) radiation therapy. This electromagnetic effect is proportional to the square of the charge of the particle. Heavy Ions are more effective than Protons. Nuclear effects are stronger and more effective than the electromagnetic interactions. Protons and Heavy Ion also have small amount of nuclear interaction with the nuclei along their path. This also adds effectiveness to the charged particle therapy, in comparison with conventional radiation therapy. The world has 70 large Proton Therapy and Heavy Ion Therapy Centers. The US has 20 large Proton Therapy Centers each with multiple treatment rooms and a few hospitals each with one room for Proton Therapy treatments. By 2016, Heavy Ion Carbon Therapy had treated 21,800 patients, and Proton Therapy had treated 149,000 patients .
Neutrons interact only with the nuclei along their path. "Fast" energetic (> MeV) neutronscan split the nuclei along their path. Neutron therapy has 3 x Relative Biological Effectiveness in comparison with conventional radiation therapy. Neutron therapy for each patient consists of a few to twelve 2 minute treatment sessions. Neutron Therapy has treated more than 10,000 patients.
Particle Therapy can also treat some of the inoperable and/or radiation resistant tumors.
2.4.2 Accelerator Neutron Transmutation of Nuclear Waste
High energy neutrons interacting with nuclei can split the nuclei, while lower energy thermal neutrons or epithermal neutrons can be captured by the nuclei. Larger quantities of neutrons with slightly higher energies (than neutrons for Neutron Therapy) can transmute nuclear waste by splitting the nuclei to become safer materials, with the same physics and similar technologies as Neutron Therapy for treating patients with tumor. To be more efficient in reducing high radiation level nuclear waste, partitioning should be applied to separate high level waste from lower radiation level nuclear waste before transmutation. Laboratories, institutes, universities, and companies in US, EU, Japan, and other countries have research and technologies for partitioning.
Accelerator Transmutations of Nuclear Waste was proposed in 1990 by a team at Los Alamos National Laboratory . Low Energy Demonstration Accelerator with 100 mA, 6.7 MeV protons was built and operated successfully . A team at Brookhaven National Laboratory also proposed Partitioning and Accelerator Transmutation of Nuclear Wastes . US Department of Energy reported to the Congress in 1999: A Roadmap for Developing Accelerator Transmutation of Nuclear Waste Technology . Partitioning and transmutation of nuclear wastes have been studied also at Argonne National Laboratory . Neutron cross sections for materials including Thorium, Uranium, Neptunium, Plutonium, Americium, Curium actinides for advanced reactor systems have been measured at the Nuclear Data Center at Brookhaven National Laboratory .
The Spallation Neutron Source (SNS)  at Oak Ridge National Laboratory is upgrading from 1.4 MW to 2.8 MW beam power, with 38 mA average beam current, 1.3 GeV protons. The European Spallation Source (ESS)  with 62.5 mA average pulse current, 2 GeV protons and 5 MW beam power is expected to deliver first beam in 2019 and full design beam energy and intensity by 2023. Numerous other high intensity proton accelerators and neutron sources worldwide enable studies and advances in sciences and technologies.
The Multi-purpose hYbrid Research Reactor for High-tech Applications, MYRRHA Project , in Belgium is expecting soon the final approval from the European Union. One of the top priorities for MYRRHA is the demonstration and studies of transmutation of nuclear waste. The EU Guinevere VENUS-F  Projects have been testing in preparation for MYRRHA. Kyoto University Critical Assembly also has been doing ADS experiments and studies . The Japan Proton Accelerator Research Complex, j-PARC, has Accelerator Driven Transmutation Experiment Facility and Transmutation Experiment Facility under construction. China has a program for Accelerator Driven System including transmutation of nuclear waste, and has selected a site. India and other countries also have research and programs for Accelerator Driven Systems.
2.4.3 Accelerator Driven Thorium Energy System
In Accelerator Driven Subcritical System (ADS), the accelerator can provide neutrons to use Thorium as fuel in a reactor for “cleaner and inexhaustible nuclear energy production” [27, 28]. The ADS eliminates the need for reprocessing in the Thorium fuel cycle. ADS for transmutation of the conventional nuclear waste, and even generate electricity from nuclear waste, can also use Thorium fuel. ADS systems can operate in the sub-critical mode for additional safety. Advances in accelerator technologies have enabled new accelerators to provide sufficient beam intensity and stability for ADS. Each 10 mA proton beam at 1 - 1.5 GeV can provide 10 – 15 MW power to supply sufficient neutrons to continuously run a reactor generating hundreds of Mega Watts of electricity. Belgium/EU, China, India, Japan, US, Korea are developing ADS . The ADS demonstration systems are expected by 2030.
The 21st Century is the Century of Sustainable Energy. Science, organizations, leaders, governments, policies, investments, corporations, foundations, institutions, communities, and public support have enabled tremendous advances toward sustainable energies. The world energy consumption is 15 TW, and is expected to increase. Solar, wind, hydro, bio energies each will provide multi Tera Watts of energy. The energy solutions also include geothermal, other renewable energies, improving energystorage, energy efficiencies, and energy conservation.
Nuclear sciences, technologies, and nuclear energy can greatly benefit society. To contribute significantly to world energy, nuclear power needs fundamental changes. Molten Salt Reactors, Thorium energy, and Accelerator Driven Systemscan also provide multi Tera Watts of sustainable energy for thousands of years. ADS can also transmute nuclear waste.
Tremendous advances in sustainable energies for all people will be achieved in the next decade. The world is moving forward in the energy transformation from using fossil fuels to using sustainable energy and providing sustainable energy to all people worldwide.
1. Global Carbon Project
3. Renewable Energy Policy Network for the 21st Century, www.ren21.net/gsrwww.ren21.net/wp-content/uploads/2017/06/17-8399_GSR_2017_Full_Report_0621_Opt.pdf
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8. International Renewable Energy Agency, www.irena.orgwww.iea-pvps.org/fileadmin/dam/public/report/statistics/IEA-PVPS_-_A_Snapshot_of_Global_PV_-_1992-2016__1_.pdf
10. US EPA List of Top Green Power Purchasers
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13. Molten Salt Reactor Experiment
14. Oak Ridge National Laboratory Molten Salt Reactor https://www.ornl.gov/msr
16. Robert Hargraves and Ralph Moir article
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18. Particle Therapy, Proton Therapy, Heavy Ion Carbon Therapy, Neutron Therapy
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19. Los Alamos Concept for Accelerator Transmutation of Waste and Energy Production
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Van Tuyle, G. J. et al., “Accelerator - Driven Sub-Critical Target. Concept For Transmutation Of Nuclear Wastes”, Brookhaven National Laboratory, BNL-46365www.iaea.org/inis/collection/NCLCollectionStore/_Public/23/008/23008978.pdf
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23. Neutron Sources
Champion M., et al., “Progress on the Proton Power Upgrade of the Spallation Neutron Source”, accelconf.web.cern.ch/AccelConf/ipac2017/papers/tupva147.pdf
European Spallation Source, https://europeanspallationsource.se/
24. Accelerator Driven Subcritical Systems,
MYRRHA Accelerator Driven System, myrrha.sckcen.be
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27. F. Carminati, R. Klapisch, J.P. Revol, Ch. Roche, J. A. Rubio, C. Rubbia, “An Energy Amplifier for Cleaner and Inexhaustible Nuclear Energy Production Driven by a Particle Beam Accelerator”, European Organization for Nuclear Research,
CERN/AT/93-47 (ET) https://cds.cern.ch/record/256520/files/at-93-047https://www.oecd-nea.org/trw/docs/rubbia/concept.pdf
28. Status of Accelerator Driven Systems Research and Technology Development
Technologies and Components of Accelerator Driven Systems, Organization for Economic Cooperation and Development, OECD, https://www.oecd-nea.org/science/wpfc/tcads/2016/
Accelerator Driven Subcritical Systems & Thorium Utilization, adsthu.org/https://www.loc.gov/today/cyberlc/feature_wdesc.php?rec=7358
G. P Yeh, email@example.com
These contributions have not been peer-refereed. They represent solely the view(s) of the author(s) and not necessarily the view of APS.