A Complete Guide to Renewable Energy Sources

Our energy dependence is increasing day-by-day, with the ever-expanding population as well as the introduction of more and more appliances and gadgets in the market promising to make our life easier and better. Do we ever seriously think about where the energy to run these devices, small or big, is coming from? Most of them require electricity, which in turn is typically generated from one of the fossil fuels – coal or oil.

One of the troubles with using fossil fuels as an energy source is that it is finite. Eventually, we will run out of these energy sources. Already, we are digging deeper and deeper to access enough to satisfy our needs. One day, it will become too expensive to extract them, in addition to the damages they inflict on the environment.

The need of the hour is to consider alternatives before we reach that stage.

The answer to this conundrum is renewable energy sources. As the name suggests, these sources of energy get replenished as we use them up. Of course, we also need to learn to limit our demand for energy to a reasonable level.

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    What is renewable energy?

    Often referred to as alternative energy or clean energy, renewable energy is energy generated from natural sources or processes that are virtually inexhaustible, but flow-limited. For example, sunlight is available as long as the sun is shining, however, its availability depends on the weather, geographical location, and time of the day.

    Renewable energy is often regarded as a new technology, as an alternative to fossil fuels. But humans have been harnessing natural energy sources for a long time for heating, lighting, food processing, transportation, etc. Sun’s energy has provided warmth and light during day and night while helping dry grains and meat as a method of preservation. The power of wind has helped sail the boats and pound grains in windmills.

    With the advent of the industrial revolution 250 years back, the demand for more reliable and less expensive sources of energy went up. This prompted humans to turn to easy and cheaper, but dirty sources of energy such as coal and oil.

    Now, with the threat of fossil fuels running out looming large and its damage to the environment becoming evident, more research and development on natural energy sources have yielded better technologies and innovations to overcome their earlier limitations. Innovations in the field have led to simpler and less expensive methods of capturing and retaining renewable energy.

    Among the types of renewable energy, the most popular by development and usage are solar, wind, hydro (water), geothermal, and biomass.

    Let us take a detailed look at these five popular renewable energy types and why renewable energy is good for the future of our environment and global economy.


    Solar Energy

    The Sun’s energy has been the ultimate source of energy for humans for billions of years. Sunlight is one of the most abundant sources of renewable energy. The amount of sunlight received by the earth’s surface in an hour is calculated to be enough to meet the energy demand of the entire world for a year!

    The first attempt by humans to harness solar energy was inventing fire. In recent years, as the demand for energy increased manifold and the need for clean energy intensified, solar energy received a big boost. Newer technologies were developed to collect and store the sun’s energy for later use for heating and lighting.

    Solar thermal energy

    One of the earliest attempts in capturing solar energy is a solar oven. Invented by British astronomer John Herschel in the early 19th century, a solar oven uses the sun’s energy to cook food.

    Now, we have more sophisticated technologies for harnessing and converting solar energy into heat energy for various purposes. Solar thermal energy devices are used to heat

    • Interiors of homes, offices, and greenhouses
    • Water in homes and swimming pools
    • Thermodynamic fluids to high temperatures in solar thermal power plants

    Solar electrical energy

    Photovoltaic (PV) devices or solar cells capture the energy of the sun, convert it into electrical energy, and at times, store it for future use. While small photovoltaic cells are used to power handheld calculators, watches, and similar electronic devices, an arrangement of PV panels can meet the energy needs of an entire home.

    PV power station, also known as a solar farm or solar park, uses a vast photovoltaic system covering many acres to produce electricity for hundreds of homes or an entire region.

    Related: Examples of Solar Energy in Everyday Life

    How is solar energy generated?

    Solar cells and panels make use of the photovoltaic effect to generate solar energy. When photons from the sunlight reach the solar panel, they impart their energy to the electrons in the semiconductor such as silicon used in the panel. This prompts electrons to move to a higher energy state, leading to a flow of electrons or electric current.

    The electricity thus generated is Direct Current (DC), which is then converted to Alternating Current (AC), a format that is required to power most devices, using an inverter. As more sunlight falls on the solar panel, more electricity is generated.

    The electricity generated is used up immediately in the case of small-scale solar panels. In solar farms, the generated electricity is supplied to the electrical grid.


    Solar-powered products

    Some of the most commonly used products with in-built solar cells or panels are

    • Solar water heater
    • Wireless solar security cameras
    • Solar air-conditioning
    • Solar charger
    • Solar lamp
    • Solar traffic light
    • Solar street light
    • Solar-powered vehicles such as cars, buses, boats, and golf carts
    • Solar-powered home appliances such as cooker, refrigerator, chimney, and radio/television


    If you would like more information about home solar panels, check out our article about where to buy solar panels for home.

    How popular is solar energy for electricity generation?

    With more and more emphasis on clean energy, the share of solar energy in global electricity production is increasing steadily every year. Development of newer technologies bringing down the cost of installation, solar power has become the most popular worldwide for new electricity generation.

    While solar power constituted just 1.06% of global electricity production in 2015, it increased to 1.32% in 2016, 1.74% in 2017, 2.19% in 2018, and 2.68% in 2019. The year-on-year growth of new solar power production is the greatest among all sources, including other sustainable energy sources.

    As the share of fossil fuels in electricity generation falls steadily and solar power registers double-digit growth worldwide due to the big boost it finds in Asia, the future looks good for clean energy.

    Which countries are the leading producers of solar energy?

    China is leading the world in new solar power installations as well as cumulative solar capacity. The US is a distant second, while India is gaining ground in recent years with the installation of the largest solar power plant in the world in Jodhpur, Rajasthan – Bhadla Solar Park with a capacity of 2245 MW.

    Top 5 countries by new solar power installations

    • China: 30,100 MW (26.2%)
    • United States: 13,300 MW (11.6%)
    • India: 9,900 MW (8.6%)
    • Japan: 7,000 MW (6.1%)
    • Vietnam: 4,800 MW (4.2%)

    Top 5 countries by cumulative solar power installations

    • China: 204,700 MW (32.6%)
    • United States: 75,900 MW (12.1%)
    • Japan: 63,000 MW (10.0%)
    • Germany: 49,200 MW (7.8%)
    • India: 42,800 MW (6.8%)

    What is the environmental impact of solar power generation?

    The Sun is providing an inexhaustible renewable energy source to produce clean and sustainable energy with no effects of pollution or greenhouse gas emissions. Despite all these plus points, solar power generation still impacts the environment in many ways.

    The topmost environmental challenges for solar energy are land use and habitat loss, water use, and the use of toxic materials in the manufacturing of solar panels leading to environmental degradation.

    1. Land Use: Large-scale solar energy generation requires large tracts of land exclusively for solar installations. This can cause disruptions in local flora and fauna, in addition to interfering with existing land uses. However, this can be minimized by locating them at low-quality locations such as brownfields, abandoned mining sites, or along transportation and transmission corridors. Utilizing rooftops of homes and commercial buildings can also reduce the land use impact. You may want to read our guide on Solar Farms: Pros and Cons and Solar Farm Land Requirements.
    2. Water Use: Though water is not used directly in solar power generation, the use of water is vital during the manufacturing process and as a coolant for Concentrating solar thermal plants (CSP). Water use depends on the location, size, and the type of cooling system used in the plant. As some of the best locations for solar farms are in places with dry climates and low water availability, this is a serious concern. In addition to this, chemical spills from the plants can contaminate groundwater sources.
    3. Hazardous materials: The manufacturing process of solar cells includes highly toxic materials that are used to clean the surface of the semiconductor. These include hydrochloric acid, sulfuric acid, nitric acid, and hydrogen fluoride among others. The newer thin-film PV cells are manufactured using highly toxic heavy metals such as gallium arsenide and cadmium telluride, while the traditional silicon PV cells are comparatively less harmful. If not handled and disposed of properly, this could pose serious public health and environmental threats. However, the silver lining is the financial incentive for the manufacturer to recycle the panels for its rare and valuable materials.
    4. Though solar energy is one of the cleanest renewable sources of energy with no pollution or emission, greenhouse gases are emitted at other phases of solar energy production. These include the extraction of resources, manufacturing, transportation, installation, maintenance, and dismantling of solar panels.

    What are the benefits and limitations of solar panels?

    Harnessing the free and abundant energy of the sun to replace the polluting and greenhouse gas-emitting fossil fuels can be nothing but advantageous. However, there exists nothing that is purely positive; there will always be a downside, even if small and inconsequential when compared to the benefits it offers.



    Wind Power

    Wind Power Renewable Energy

    The wind is caused by the uneven heating of the earth’s surface. It is possible to capture the power of the wind using turbines and generate electricity. Wind power is more commonly used for large-scale energy generation with wind farms to supply electricity to the national grids. However, off-grid or domestic generation systems can be used to power homes, it is a viable option only in windy locations. 

    The invention of wind turbines happened in the late 19th century as a means to find an input for the electric generator. The modern wind turbine with a horizontal axis was first installed in Denmark at the turn of the 20th century.

    A renewable energy source like solar power, wind energy is not dependent on the time of the day or weather conditions. With the big push for renewable energies worldwide, the share of wind energy in global energy production is going up steadily.

    How is wind power generated?

    A wind turbine converts the wind energy into electrical energy using the aerodynamic force from the rotor blades. As the blades catch the wind, it creates a difference in air pressure on either side of the blades leading to both lift and drag. When the force of lift is stronger than the drag, the rotor rotates. This spin is transmitted to the generator through the shaft and a series of gears that speeds up the rotation. The generator converts the aerodynamic force into electricity.

    Wind turbines can be classified as horizontal-axis turbines or vertical-axis turbines based on the wind direction. While the former is the conventional and more popular model, the latter comes with the advantage of omnidirectional blades.

    Wind turbines are also categorized as land-based, off-shore, or distributed wind turbines. While the first two are used in commercial energy generation, the distributed wind turbines are typically small single turbines used for residential, agricultural, or other small-scale energy needs.

    Related:  Onshore vs Offshore Wind Turbines

    How popular is wind power worldwide?

    The big campaign for renewable sources of energy has resulted in the wind power sector growing exponentially. As the cost falls and turbine capacity increases, the share of wind energy in global power generation has risen in the past two decades.

    A wind turbine in 1985 came with a rotor diameter of 15 meters and a rated capacity of 0.05 megawatts (MW). Today’s best commercially-used turbines have rotor blades measuring more than 150 meters and a capacity of 8 MW. Even the average capacity of today’s turbines is 2-3 MW. As the power output of a turbine is directly proportional to the dimensions of the rotor blades, wind power generation has benefited immensely from technological advancements in the field.

    Global wind power generation has witnessed a big leap from a mere 7.5 GW in 1997 to 651 GW in 2019 from both onshore and offshore installations. The share of wind power in global power generation has increased from just 0.03% in 1997 to 2.18% in 2019, most of the increase coming in the last 10 years.

    Which countries are the leading producers of wind energy?

    China is leading in wind power generation, accounting for more than a third of the global output. The onshore wind farm in Gansu Province with a capacity of 7,965MW is five times larger than its nearest rival.

    Top 5 countries by new wind power installations

    • China: 26,155 MW (43.3%)
    • United States: 9,143 MW (15.1%)
    • United Kingdom: 2,393 MW (4.0%)
    • India: 2,377 MW (3.9%)
    • Germany: 2,189 MW (3.6%)

    Top 5 countries by cumulative wind power installations

    • China: 236,402 MW (36.3%)
    • United States: 105,466 MW (16.2%)
    • Germany: 61,406 MW (9.4%)
    • India: 37,506 MW (5.8%)
    • Spain: 25,224 MW (3.9%)

    For more on wind power, see our article on the examples of wind energy in everyday life.

    What are the environmental impacts of wind energy?

    Even as wind energy is a clean and renewable energy source, the manufacture, installation, and operation of wind turbines pose negative environmental ramifications.

    1. Land space: Though individual turbines do not need much physical land space, the size of the rotor blades makes it inevitable that there is sufficient space between turbines. Onshore wind farms occupy large tracts of land, while offshore ones occupy even larger space as their rotor blades tend to be larger.
    2. Wildlife: In addition to disturbing the habitat of several animal species with the setting up of wind farms, birds and bats often get caught in the rotor blades. Offshore turbines have a similar impact on marine life.

    What are the benefits and limitations of wind power?

    Wind energy offers a wide range of advantages, making it one of the fastest-growing sources of renewable energy in the world. Not unlike solar power, wind energy comes with some constraints, which the researchers worldwide are trying to overcome with technological advancements.



    You may also want to take a look at our guide on Wind Energy Advantages And Disadvantages.


    Hydroelectricity Renewable Energy

    Hydropower is the electrical energy generated by harnessing the power of water. It is usually done by building dams across rivers creating reservoirs. As water is released, it flows down with tremendous energy to turn the turbine downstream. The turbines are connected to generators that produce electricity.

    The earliest evidence of the use of hydropower was by the Greeks 2000 years back. They used water wheels for grinding wheat into flour. The modern hydropower plant was developed in France in the mid-18th century. With the invention of Alternating Current (AC) which allowed power to be transmitted long distances, hydroelectricity got a big boost. The late 19th century and 20th century witnessed great advancements in hydroelectric power generation, making it a major constituent of sustainable energy sources.

    How is hydropower generated?

    A hydroelectric power plant uses the kinetic energy of the water flowing downstream to turn the turbines. This is achieved by blocking the river by building a dam across it upstream. The sluice gates of the dam are opened as and when required, allowing water to gush downstream with great force. The turbines stationed at the powerhouse down the stream are turned by the force of the water. The shaft of the turbine is connected to the generator, which produces electricity.

    Related: How Is Hydroelectricity Produced Step by Step

    How popular is hydroelectricity worldwide?

    Hydropower generation has risen at a steady rate of 3% annually over the past four decades. With the addition of 15.6 GW in 2019, the total global hydropower installed capacity reached 1,308 GW. However, the additional installation in 2019 is less than that of 2018, which was 21.8 GW.

    As power generation from other sources has increased at a much faster pace, the share of hydroelectricity in global power generation is continuously decreasing in the same period.

    Which countries are the leading producers of hydroelectricity?

    The growth in hydropower capacity continues to be flat with only Brazil and China adding a significant amount of new capacity. Brazil (4.92 GW), China (4.17 GW), and Laos (1.89 GW) dominated the hydropower sector in 2019 by building additional capacity. East Asia, the Pacific, South America, and South and Central Asia are the regions where the new capacity for hydropower generation came up.

    The top 10 countries by installed hydropower capacity are

    • China (356.4GW)
    • Brazil (109.06GW)
    • United States (102.75GW)
    • Canada (81.39GW)
    • India (50.07GW)
    • Japan (49.91MW)
    • Russia (49.86GW)
    • Norway (32.67GW)
    • Turkey (28.5GW)
    • Italy (22.59GW)

    The top 10 countries by hydropower generation are

    • China (1302 terawatt hours)
    • Canada (398 terawatt hours)
    • Brazil (386.95 terawatt hours)
    • United States (274 terawatt hours)
    • Russia (190.29 terawatt hours)
    • India (162.1 terawatt hours)
    • Norway (125.77 terawatt hours)
    • Turkey (87.09 terawatt hours)
    • Japan (86.67 terawatt hours)
    • Venezuela (72 terawatt hours)

    What are the environmental impacts of hydroelectricity?

    Technically speaking, hydroelectricity is clean energy that is friendly to the environment. However, the construction of large dams has environmental ramifications

    1. Land Use: Constructing large hydropower projects can lead to an alteration of the upstream landscape due to the increased water level in the reservoir area. Entire villages are submerged, along with prime farming land. Loss of property and livelihood is a direct impact of large dams on humans. On the other hand, the reduction in the downstream flow leads to the degradation of land.
    2. Damage to wildlife habitat: Submergence of land in the reservoir area and decreased flow downstream can lead to loss of wildlife habitat. Construction of large hydropower projects involves blocking, diverting, and changing the natural course of rivers. This can impact the migration of fish for breeding. The fish also gets caught in the turbines if adequate measures are not taken to avoid this.
    3. Greenhouse gas: Though the working of the turbines and power generation doesn’t have any adverse effects on the environment directly, there is significant greenhouse gas emission from the reservoir. The dead plants and other organic material trapped in the reservoir releases greenhouse gases such as carbon dioxide and methane on decomposition.

    What are the benefits and limitations of hydroelectricity?

    Hydroelectricity is a clean and renewable energy source. Despite its many advantages, hydropower comes saddled with a horde of adverse consequences.

    You may also want to take a look at our guide on the advantages and disadvantages of Hydroelectricity.



    Geothermal Energy

    geothermal energy

    There is heat trapped beneath the surface of the earth. This is found in the rocks and fluids under the earth’s crust as far down as the hot molten magma. This heat energy is carried to the earth’s surface by water and steam. To make use of this energy source, mile-long wells are dug on the earth’s surface to access the hot water and steam. The heat energy harnessed is used to work turbines connected to electricity generators.

    Geothermal energy from hot springs had been used for bathing and cooking from ancient times. Evidence suggests that Native Americans used it for cooking 10,000 years ago. Bathing in hot water springs was popular among the Greeks and Romans. In all these instances, the hot water and steam available on the earth’s surface alone were used.

    The first modern geothermal plant was set up in 1904 by Italian scientist Piero Ginori Conti. In this steam was used to generate power. The first large-scale plant began operation in the 1960s in San Francisco, USA, producing 11MW.

    How is geothermal energy generated?

    Earth’s temperature rises at the rate of 25° C every kilometer (1° F every 77 feet) with depth from the surface to the core. When rock formations in the lower crust and mantle get heated up to 700-1,300° C (1,300-2,400° F), they can partially melt and turn to magma. The molten magma mixed with hot gas heats the rocks and underground aquifers above it. Hot water and steam are released through hot springs, geysers, steam vents, mud pots, and underwater hydrothermal vents.

    All these are sources of geothermal energy. The heat from the hot water and steam is either used directly for heating purposes or used to turn turbines, which in turn generate electricity.

    As most of the heat from the molten magma remains in the lower crust and mantle and is not released to the earth’s surface. This geothermal heat is accessed through drilling wells and injecting water to produce hot steam.

    Geothermal power plants are of three types – dry steam, flash, and binary. Dry steam, the oldest of geothermal technologies, uses steam from underground to drive turbines. Flash plants use high-pressure hot water taken from underground to run turbines by turning them to steam. In binary plants, the heat from hot water is transferred to another liquid with a low boiling point. As it turns to its gaseous state, it is used to turn turbines.

    Related: How Does Geothermal Energy Work (Step-by-Step guide)

    How popular is geothermal energy worldwide?

    Global geothermal installed power generation capacity now stands at 15,406 MW. In 2019, with an addition of 759 MW in capacity, the geothermal sector witnessed the largest annual growth in the past more than 20 years.

    The United States is the leading producer of geothermal energy in the world with an installed capacity of 3676 MW and 16.7 billion kilowatt-hours of electricity generation. The world’s largest geothermal complex comprising 22 geothermal plants known as the Geysers is based in California.

    Indonesia is home to four of the world’s top 10 geothermal power projects. This includes the two biggest plants by active capacity – Gunung Salak facility, the world’s largest active capacity with 375MW, and Sarulla 1 project, with an output of 330MW.

    Which countries are the leading producers of geothermal energy?

    The top 10 countries by installed geothermal capacity are

    • United States – 3,676 MW
    • Indonesia – 2,133 MW
    • Philippines – 1,918 MW
    • Turkey – 1,526 MW
    • New Zealand – 1,005 MW
    • Mexico – 962.7 MW
    • Italy – 944 MW
    • Kenya – 861 MW
    • Iceland – 755 MW
    • Japan – 601 MW

    What are the environmental impacts of geothermal energy?

    The fluids extracted from the earth for drawing geothermal energy contain a mixture of gases such as carbon dioxide, hydrogen sulfide, methane, ammonia, and radon. If released into the earth’s atmosphere, these gases can contribute to global warming, acid rain, radiation, and toxic smell.

    In addition to the gases, the hot water from the underground contains toxic chemicals like mercury, arsenic, boron, antimony, and salt. These harmful chemicals separate from water when it cools down. If not handled properly, these can lead to environmental degradation.

    However, the latest practice of injecting the fluids and cool water back into the earth has reduced this risk.

    The construction of deep wells for extracting geothermal energy can affect the stability of the land. Subsidence, uplift, and earthquake are the major aftereffects of drilling and water injection.

    The natural cycle of geysers is also found to be impacted by the construction of geothermal power plants.

    What are the benefits and limitations of geothermal energy?



    You may also want to take a look at our guide on Geothermal Energy Advantages and Disadvantages.

    Biomass Energy

    Biomass Energy

    Biomass is the renewable organic material that comes from plants and animals – both living and dead. Plants produce biomass through photosynthesis. It contains the stored chemical energy from the sun. Biomass may be burned directly to produce heat or converted into liquid or gaseous forms by various processes.

    Humans have used biomass energy right from the days of cavemen who burned wood for cooking and warmth. In the 13th century, the Italian explorer Marco Polo had described how the Chinese produced biogas using covered sewage tanks. In the late 19th century, Rudolf Diesel built a biofuel engine that runs on vegetable oil.

    Biomass continued to be used in many countries worldwide for cooking and heating. Biomass fuels are being used for transportation and electricity generation in some countries as a means to cut down on the dependency on fossil fuels and to reduce pollution and greenhouse gas emissions.

    How is biomass energy generated?

    Biomass energy sources include

    • Wood and wood waste such as firewood, wood pellets, and wood chips, lumber and furniture mill sawdust and waste, and black liquor from pulp and paper mills
    • Crops and waste materials such as corn, soybeans, sugar cane, switchgrass, woody plants, and algae, and crop and food processing residues
    • Biogenic materials in municipal solid waste such as paper, cotton and wool products, food, and wood wastes
    • Animal manure and human sewage

    Biomass is converted to energy through processes including

    • Direct combustion (or burning) to produce heat
    • Thermochemical conversion to produce solid, gaseous, and liquid fuels
    • Chemical conversion to produce liquid fuels
    • Biological conversion to produce liquid and gaseous fuels

    Direct combustion is the most commonly used method to convert biomass into energy. Biomass is burned directly to produce heat, which is either used for heating purposes or to turn turbines and produce electricity.

    Thermochemical conversion involves thermal decomposition of biomass in closed, pressurized vessels called gasifiers at high temperatures. Based on the temperature used in the process and the oxygen present, different processes used in thermochemical conversion are pyrolysis, hydrotreating, and gasification.

    The chemical conversion known as transesterification is used to convert vegetable oils, animal fats, and greases into fatty acid methyl esters (FAME). FAME is used to produce biodiesel.

    The biological conversion includes two processes – fermentation to convert biomass into ethanol and anaerobic digestion to produce renewable natural gas. Sewage treatment plants, dairy and livestock farms, and solid waste landfills are the ideal locations for anaerobic digesters. Ethanol is used as a vehicle fuel. Treated renewable natural gas may be used as a substitute for the fossil fuel natural gas.

    How popular is biomass energy worldwide?

    Biomass energy contributes around 10% of the global energy supply. A bulk or almost two-thirds of this comes from its use in cooking and heating in developing countries. The rest one-third is used for heat and power generation (13%), the industrial sector (15%), and transport (4%).

    In 2019, biomass power generation increased by approximately 5%, falling below average yearly growth of 6% since 2011. The contribution of biomass energy in global power generation is about 1.4%.

    Biomass energy has significant potential in raising energy supply in developing and populous nations with high energy demand such as China, Brazil, and India. Its diverse applications and methods of generation make biomass energy a convenient, flexible, and appealing substitute for fossil fuels.

    Which countries are the leading producers of biomass energy?

    The addition of new capacity in the bioenergy sector was a modest 6GW in 2019. China’s contribution was more than half of this at 3.3 GW. Other countries with significant expansions were Italy, Germany, Turkey, and Japan.

    The top 10 countries by installed bioenergy capacity are

    • Brazil – 14.78 GW
    • China – 13.24 GW
    • United States – 12.71 GW
    • India – 10.14 GW
    • Germany 9.65 GW
    • United Kingdom – 6.96 GW
    • Sweden – 5.02 GW
    • Thailand – 4.20 GW
    • Italy – 3.49 GW
    • Canada – 3.37 GW

    What are the environmental impacts of biomass energy?

    When biomass is burned for heat and electricity, carbon dioxide is released. Though biomass emits greenhouse gases and pollutants into the atmosphere, it is considered carbon-neutral and different from other nonrenewable and renewable resources.

    The sources of biomass, such as wood from trees and crops absorb carbon dioxide during photosynthesis. If biomass sources absorb as much carbon dioxide as is emitted during the combustion process, the carbon cycle may be considered as in balance. This is the reasoning for terming biomass energy as carbon-neutral.

    However, in reality, it doesn’t work as simple as that. The carbon footprint of biomass energy depends on the harvesting of biomass, efforts in regrowing biomass, the kind of biomass used, the technology used for combustion, the timeframe for regrowing, and the energy resource it is replacing. When trees are burned and used up at a pace faster than it takes to regrow, the carbon neutrality of biomass is compromised.

    Most large-scale biomass energy plants grow trees and crops for the sole purpose. This can make things worse. Growing crops require landscape and water. When they are cut down, it disrupts the habitats of flora and fauna in the area. As the crop waste or trees are removed for biomass energy production, it deprives the land of its natural fertilizer.

    Biogas produced from animal waste in anaerobic digesters leaves a net negative greenhouse gas emission because of the presence of methane. Biogas, which is predominantly methane, if not burned as fuel can add to the greenhouse gas emissions.

    Related: Bioenergy: Advantages and Disadvantages

    What are the benefits and limitations of biomass energy?



    A comparison of renewable energy sources

    Now that we have gone through the five examples of renewable energy sources in detail and deliberated on the pros and cons of each, it is imperative to see which is the most efficient of them all.

    The efficiency of an energy source depends mostly on the cost of the fuel produced, the cost involved in the production process, and the cost of repairing the damage to the environment. These are the most visible factors of efficiency. The hidden factors include how efficiently each renewable energy can be converted to electricity.

    To compare various renewable sources of energy for their efficiencies, it is essential to find the cost factor of each taking into account the various visible and hidden costs. Levelized Cost of Electricity (LCOE) is a helpful tool in comparing renewable energy sources. In addition to the various costs incurred, it also takes into account the policy-related factors and uncertainties. LCOE also weighs in the efficiency of the energy source replaced and how it affects the economy of the region. 

    And the winner is…

    Wind power tops the list with an offering of 1164% of its original energy value, while the rest of the sources of renewable energy lag far behind. Geothermal provides 514% of its original energy value, hydroelectricity 317%, solar energy 207%, and biomass energy coming last with a low-efficiency level of 52% of its original energy value.

    However, sustainable energy sources score a lot better than nonrenewable resources such as coal or natural gas. When accounting for the environmental damage, difficulty in extraction, and its limited availability, coal scores the lowest of all energy sources. The efficiency of coal is a mere 29% of its original energy value.

    As the technologies for generating electricity from renewable energy sources grow and develop, the efficiencies of these resources are expected to improve in the future.

    Final thoughts

    When we started realizing the adverse impact of burning fossil fuels and the limitations in its availability, our search for alternative energy resources began. We went back in time and explored the resources discarded earlier. The wisdom of our ancestors who lived in sync with nature tried, tested, improvised, and improved.

    Change is always hard to come by, especially when the magnitude is so large and the impacts are so huge. However, when we realized that the survival of the whole world is at stake, we stepped up to it and made it happen.

    Over the last few decades, slowly yet surely, the change is visible. The use of fossil fuels is coming down for sure and is being replaced by renewable energy sources. Let us hope that one day we will be totally free of fossil fuels and our world will achieve energy sustainability.

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