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.
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.
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.
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.
Some of the most commonly used products with in-built solar cells or panels are
- Solar water heater
- 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
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.
- 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%)
- 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.
- 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.
- 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.
- 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.
- 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.
- Inexhaustible source: One of the key benefits of solar power is its availability in plenty. It is truly renewable and there is no limit on the quantity of energy harnessed. Its availability in all parts of the world, every day of the year, makes it the most popular of all renewable energy sources.
- Reduces electricity bill: The commercial production of solar energy costs a fraction of that from fossil fuels. When installed at home, it can help in lowering the electricity bill. In case connected to the main grid, the excess power generated can add to the income.
- Energy independence: Areas with no access to grids can generate electricity to meet energy demand with solar panels. It helps in providing basic requirements of lighting, cooking, and clean water in remote locations.
- Low maintenance: Once installed, solar panels do not require much maintenance, other than cleaning once or twice a year. Averaging a lifetime of 20-25 years, solar panels are easy to maintain due to no wear and tear in the absence of moving parts. The inverter and cables may require some attention and maintenance.
- Newer technology: Constant advancements and improvement in technology have helped the sector bring down the cost, become more energy-efficient, and make installation more user-friendly. In addition to this, the incentives offered for solar installation and the possibility of earning money from surplus energy generated make solar power generation a very lucrative option.
- High initial investment: The cost of solar panels, inverter, batteries, wiring, and the installation is very high. Even after taking into account the various incentives offered, it still acts as a major deterrent for an average homeowner to install solar panels for heating or lighting. However, with improving technologies bringing down prices and governmental agencies offering attractive schemes, the future looks brighter for solar power.
- Intermittent source: As the sun is not present at night and on cloudy and rainy days, solar power cannot be relied upon as a continuous source of energy. To overcome this constraint, installing batteries is helpful. Batteries can store the energy generated for later use. Again, the cost of installing batteries can drive up the total cost. But, technological advancements in the field are reducing the prices steadily.
- Require space: To meet your entire energy needs, you may have to install a large number of solar panels and this necessitates space. Rooftops are the ideal location for solar panels for homes, but if it is not enough you may have to have some in the yard as well. Or, you can have solar power as a supplementary source of energy. However, in the case of large-scale solar power generation, large tracts of land have to be set aside solely for the installation of solar panels.
- Clean yet polluting: Though solar energy as such is a clean energy source, the manufacturing, transporting and installation of solar panels lead to pollution and greenhouse gas emissions. Toxic materials and hazardous processes associated with the manufacturing of solar panels can indirectly degrade the environment. Despite this, solar power is less polluting than other natural energy sources.
- Not easy to move: Uninstalling and reinstalling the solar system to new premises may be daunting and expensive.
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.
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.
- 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%)
- 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%)
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.
- 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.
- 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.
- Clean, sustainable, and abundant: Wind turbines don’t pollute or emit greenhouse gases. Available in plenty without any limitations, wind power is ready to be harnessed so long as the sun shines and the wind blows.
- Cost-effective: Once installed, with minimum maintenance costs involved, the price of energy generated remains more or less fixed during its lifespan of 20-25 years. When compared with the rising conventional energy rates, this is a definite advantage.
- Require only vertical space: Unlike solar panels that require large areas and cannot co-exist with anything else, wind turbines can be installed in existing land and farms as it needs mostly vertical space.
- Energy independence: As space required for installing wind turbines is less, wind energy is an excellent energy source in windy regions for domestic and small-scale consumers.
- Limited location: Wind being the necessary constituent, wind turbines can be used only in areas with good wind speed. Fluctuations in wind speed also affect the energy generated.
- High upfront investment: The initial expenditure of installing a wind energy system is still high, despite the advancements in technology cutting it down drastically in the last decade.
- Noise and Aesthetic pollution: The whirring of the rotor blades can be heard miles away. Most people consider them a blot on the landscape.
- Endangering wildlife: Birds and bats are often killed when they fly into the spinning blades. However, the proper positioning of wind plants has improved the situation in recent years.
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.
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.
- 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)
- 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
- 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.
- 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.
- 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.
- Sustainable resource: Hydropower projects trap the energy of running water without consuming it. As long as the river is flowing, it is possible to generate power.
- Long lifespan of dams: Once constructed and operational, hydropower projects last for 50 years or even more.
- Continuous power source: Unlike solar and wind energy, hydropower is available round the clock throughout the year.
- Adjustable: Hydropower plants can increase or decrease power generation based on demand by adjusting the flow of water. This is a unique attribute of hydropower that none of the sources of renewable energy have.
- Creates artificial lakes: The reservoirs can be used for recreational purposes, turning them into tourist attractions. Tourism can help in boosting the local economy.
- Infrastructure development: Construction activity in the area can lead to an improvement in the infrastructure of nearby cities and towns. To transport the heavy equipment for hydropower projects, new roads need to be built and the condition of existing ones upgraded.
- High investment: When compared to other nonrenewable and renewable resources, the initial cost is very high for hydropower plants. However, in the long run, hydel projects have proven to be value-for-money investments.
- Limitation in the location: It is not possible to build hydropower plants anywhere. Often, the suitable locations are remote and far from cities, necessitating long-distance transmission of electricity.
- Impact of drought: As a hydropower plant is entirely dependent on the running river water, drought can have an adverse impact on power generation. The performance of a hydropower project is drastically reduced when the water level in the reservoir goes down. With climate change having a significant impact on the rains and water flow in rivers, the reliability of hydropower plants is not assured.
- Flood risk: Again, climate change can play a significant role in the amount of rainfall in the catchment areas of the rivers. When it rains heavily, there have been instances of excessive water discharge from reservoirs or on rare instances dams giving away and flooding the downstream areas.
- Environmental concerns: Submergence of towns and fertile farmland, adverse impact on wildlife habitat, influencing fish migration, and greenhouse gas emissions from organic material in reservoirs are some of the negative consequences of hydroelectric projects.
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.
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?
- 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?
- Environment-friendly, renewable: The carbon footprint of geothermal power plants is very low, making them environment-friendly. As the hot reservoirs within the earth’s interior are constantly replenished, making geothermal energy both renewable and sustainable.
- Low emissions: The emission of greenhouse gases like carbon dioxide is very low when compared to other natural energy sources. The emission is virtually nil in binary plants.
- Reliable: Even when compared to other renewable energy sources, geothermal energy is available year-round and is not prone to fluctuations. It is possible to predict the energy output of a geothermal plant with high levels of accuracy.
- Comparatively inexpensive: When used directly for heating, geothermal energy can save up to 80% on fossil fuels. As geothermal systems have fewer moving parts that are sheltered inside buildings, their lifespan is relatively high and the cost of maintenance low.
- Efficient and compact: Geothermal systems require 25-50% less electricity than conventional systems for heating and cooling, making them high on energy efficiency. The flexible design of geothermal systems helps in adapting them to different situations, necessitating lesser space than conventional systems.
- Huge potential: With the world’s energy demand rising constantly and search is on for renewable sources of energy to replace the highly polluting and fast depleting fossil fuels, geothermal energy presents great growth potential.
- High initial investment: The cost of exploration and setting up geothermal plants is very high. For individual households, the cost of drilling and installing a complex system can act as a damper, though the return on investment is very promising.
- Location-specific: One of the most prominent disadvantages of geothermal power plants is that it is location-specific. It is available for extraction along the tectonic plates of the earth’s crust. Hence it is restricted to countries such as the US, Iceland, Indonesia, and Kenya.
- Environmental impacts: If not managed well, geothermal power plants can release high amounts of greenhouse gases and chemical pollutants. Reinjecting fluids can cause earthquakes.
- Eventual cool down: Though a sustainable and renewable energy source, geothermal sources may cool down eventually. This means no more geothermal energy can be extracted. The solution to this problem is tapping directly into the heat of the magma, which is a non-depletable heat source.
- Require proper management to maintain sustainability: Injection of fluids back into the earth is vital to maintain the sustainability of geothermal plants. If fluids are removed faster than they are replaced, geothermal reservoirs may get depleted after a few decades.
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.
- 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.
What are the benefits and limitations of biomass energy?
- Carbon-neutral: As the trees and other vegetation used for biomass energy production can offset the carbon dioxide released during burning, biomass energy is considered carbon-neutral.
- Reliable: Unlike other sources of renewable energy such as solar or wind power, biomass is available 24×7 year-round.
- Reduces waste: The enormous amounts of vegetation waste generated after harvesting crops like sugarcane, soybean, and corn can be put to useful and profitable use by generating biomass energy from them.
- Expensive and tedious: Gathering, transporting, and storing biomass sources is challenging as well as a costly task. This is an extra expenditure that other renewable energies need not account for. This expense is in addition to the high cost involved in building plants and installing the machinery. The overall cost depends on the type of biomass used and the technology used to extract electricity.
- Location limitations and space requirements: Storing biomass requires space. Often, plants are built close to the source of biomass to reduce the expenditure on transport. Additional land space is required for the regrowing of biomass to replace the used-up quantity, as many power companies are growing crops for the sole purpose of bioenergy extraction.
- Adverse environmental impact: The impact on the environment from bioenergy generation depends mostly on the type of biomass used and the technology used for power generation. At best, it can be carbon-neutral. However, when biomass energy is being generated on a large scale, maintaining carbon neutrality is not a viable prospect.
A comparison of renewable energy sources
Source: Energy Points – The Wall Street Journal
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.
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.