Renewable Energy
Introduction
Renewable energy refers to energy sources that are naturally replenished and can be harnessed on an ongoing basis, unlike fossil fuels which are finite resources. The most common types of renewable energy include solar, wind, geothermal, hydroelectric, and biomass.
As concerns grow over the environmental impacts of fossil fuels as well as their limited supply, there has been increasing interest and investment in renewable energy in recent decades. This essay will provide an overview of the major renewable energy sources, their benefits, current use worldwide, as well as the challenges and future prospects for renewable energy.
Major Types of Renewable Energy
Solar Energy
Solar energy refers to the radiant energy from the sun that reaches the Earth. It can be harnessed in various ways. Photovoltaic (PV) panels made from semiconducting materials can convert sunlight directly into electricity through the photovoltaic effect. Concentrated solar power (CSP) systems use lenses or mirrors to focus solar radiation to drive traditional steam turbines or engines. Solar thermal collectors absorb solar radiation to heat water or air.
Passive solar building design takes advantage of sunlight to provide lighting and heating. Solar energy has become one of the fastest growing renewable sources, with global capacity exceeding 500 gigawatts by the end of 2018.
Wind Energy
Wind energy utilizes the natural kinetic energy of wind, typically using large wind turbines to generate electricity. Wind flows over the blades of the turbine, causing them to rotate and spin a generator to produce electricity. Wind power capacity has expanded substantially in recent decades, with over 600 gigawatts installed worldwide as of 2018. Major markets include China, the United States, Germany, India and Spain.
Offshore wind farms and larger turbine sizes provide opportunities for continued growth in wind energy.
Hydropower
Hydropower harnesses the energy of flowing water to produce electricity using turbines. Most hydropower comes from dammed rivers, but small run-of-river projects allow generating electricity from the natural flow of rivers without a large reservoir.
Hydropower supplies around 16% of the world's electricity, predominantly from large facilities. However, untapped potential remains, especially micro hydropower projects under 10 megawatts.
Geothermal
Geothermal energy taps into the natural heat within the earth to provide renewable power. High temperature geothermal resources are used to generate electricity while low to moderate temperature geothermal can be used directly for heating. There are three main types of geothermal power plants: dry steam, flash steam, and binary cycle.
Dry steam plants use steam from geothermal reservoirs directly to turn turbines. Flash plants take high pressure hot water, convert it to steam, then use the steam. Binary cycle plants transfer heat from geothermal fluids to another liquid which vaporizes when heated, driving a turbine.
Biomass
Biomass energy utilizes organic matter such as wood, crops, municipal and agricultural waste as a fuel source through direct combustion or converted into biofuels. It can be used to produce electricity, useful heat, transportation fuels like ethanol and biodiesel. Wood and wood waste account for about half of biomass energy today.
Biomass can provide a low-carbon renewable energy source when coupled with sustainable practices and management.
Benefits of Renewable Energy: -
Environmental Benefits
The most significant advantage of renewables is their dramatically lower environmental impact compared to fossil fuels. Burning of fossil fuels releases pollutants like particulates, nitrogen oxides and sulfur dioxide that contribute to smog and acid rain. More importantly, fossil fuel combustion produces carbon dioxide emissions that accumulate in the atmosphere and lead to global warming and climate change. In contrast, renewable energy sources produce little to no global warming emissions. Switching to renewables can help reduce air pollution, mitigate climate change, protect public health, and reduce environmental damage from mining, drilling, transportation of fuels.
Energy Security
Increasing renewable energy improves energy security by diversifying the energy mix and reducing dependence on imported fossil fuels. Geopolitical conflicts can disrupt the supply of fossil fuels like oil and natural gas. Renewable energy drawn from domestic resources provides a stable, secure supply without being subject to global price volatility and political instability in oil-producing countries. Local renewable generation also strengthens energy security by decentralizing energy production.
Economic Development
Expanding renewable energy can bring substantial investment and create many skilled jobs in manufacturing, construction, installation and maintenance. Building out solar, wind, and geothermal generation requires major investments that spur economic growth. Renewables are labor intensive to manufacture and install. Supply chains for materials, components and services to support renewable technologies can be developed locally. Rural areas can benefit from income and tax revenues from siting large wind and solar farms.
Access to Energy
Renewable mini-grids and off-grid systems can provide electricity access to rural and remote areas where expanding the main power grid is too costly. Small-scale solar, wind, micro-hydro and biomass projects can be deployed to provide power in developing regions and replace diesel generators. Renewables can enable developing regions to grow sustainably without relying heavily on fossil fuel imports. Decentralized renewables avoid the massive upfront infrastructure costs of centralized fossil fuel power plants and transmission lines.
Current Status of Renewable Energy
Renewable energy has achieved strong growth rates over the past decade, driven by supportive policies, cost reductions, and technological advances. By 2018, renewables accounted for 12.9% of global total final energy consumption. 85% of global renewable generation comes from hydro, wind and solar.
Hydroelectricity makes up the largest share of renewable power, meeting 16% of global electricity demand. Major markets include China, Brazil, Canada, the United States and Russia. However, growth has slowed compared to wind and solar. Wind power capacity expanded nearly 10-fold over the last decade and provided 5% of global electricity in 2018. Solar PV capacity soared from under 10 gigawatts in 2008 to over 500 gigawatts by the end of 2018. Renewables have captured most new generation capacity installations worldwide since 2015.
The International Renewable Energy Agency projects that under current policies, renewables will supply 27% of global electricity production by 2030. With decarbonization efforts in line with the Paris Agreement goals, renewables could reach 86% of global power generation by 2050. Realizing this potential will require stronger policies and accelerated adoption in the power sector as well as expanding renewable energy use for heating, industry and transportation.
Challenges for Renewable Energy
Intermittency
The output of some renewables like solar and wind varies based on environmental conditions. Solar generation drops at night and during cloudy weather. Wind speeds fluctuate, affecting turbine output. This intermittency makes it challenging to integrate large shares of these variable renewables into the electric grid. Energy storage systems like batteries and pumped hydro storage can store renewable energy when it exceeds demand and dispatch it when production drops. Geographic distribution and forecasting also help smooth out variable generation.
High Upfront Costs
While renewable energy has very low operating costs, initial capital costs can be higher than conventional power plants. Upfront investment to build solar, wind and geothermal plants is recovered over decades of operation. Renewables become even more cost-competitive when externality costs like environmental and health damages from fossil fuels are accounted for. But financing large projects with high upfront costs can be an obstacle. Policy support like tax credits, feed-in tariffs and renewable portfolio standards help boost deployment by improving project economics.
Transmission Constraints
The best resources for wind and solar are often located far from population centers. Expensive transmission infrastructure is needed to deliver the electricity to where it is needed. Grid congestion can further constrain renewable generation during peak output times. Building out more transmission capacity and grid interconnections can enable wider geographic distribution of renewables and smoother power flows.
Competing Land Use
Large-scale solar and wind projects require significant land area. In densely populated regions, competition over land use with other needs like housing, agriculture and conservation can make project siting and permitting difficult. Careful land use planning, site selection and community engagement can overcome these conflicts. There are also many opportunities to develop solar on existing rooftops, parking lots and landfills.
Future Outlook for Renewable Energy
Looking ahead, the prospects for continued strong growth in renewable energy look promising, driven by the need to combat climate change along with improving economics compared to fossil fuels. However, realizing a full-scale transition to renewable energy requires scaling up technologies, adoption rates, investment and policy support.
Growth in distributed solar and wind power worldwide will depend on reducing soft costs like permitting, financing and installation. Emerging technologies like floating offshore wind farms, solar desalination and renewable-powered electric vehicles can unlock new potential applications. Energy storage innovations will help overcome intermittency challenges while smart grids aid integration. Biomass and geothermal energy can provide renewable baseload power to complement variable solar and wind generation.
Stronger climate policies like carbon pricing and clean energy standards will be essential to incentivize the energy transition and improve competitiveness for renewables versus fossil fuels. All sectors from electricity to heating and transport must accelerate adoption of renewable technologies. Investment in renewable energy needs to scale up further to realize decarbonization goals.
The renewable energy landscape 10 to 20 years from now can look radically different, with solar, wind, geothermal, hydroelectric and biomass generating the majority of our power sustainably - if we mobilize the needed political will and investment. The technological potential and public interest are there. Concerted effort bringing advancements across all fronts – technology, infrastructure, policy, finance – can make this renewable future a reality.
Conclusion
In summary, renewables such as solar, wind, hydroelectric, geothermal and biomass offer substantial benefits ranging from climate change mitigation to energy security and economic development. Renewable energy has seen rapid growth in recent years, now accounting for over 12% of final energy consumption globally. However, realizing the potential for much higher shares of renewables requires continuing to improve technologies, encourage adoption, and implement supportive policies and investment frameworks. The renewable energy transition presents both challenges and opportunities. With determined effort across multiple fronts, renewable energy can move from the margins and into the mainstream worldwide, providing clean, sustainable energy for current and future generations.
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