Category Archives: Renewable Energy

Renewable Energy

Biomass Energy – Definition, Advantages and Future

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Biomass Energy is hailed as a renewable source of energy and a method for sustainable waste disposal. In this blog, I will show you the definition of biomass energy, its feedstock, its advantages, disadvantages, and the various methods available for its thermal conversion.

Let’s begin by understanding the definition of biomass energy.

Biomass Energy Definition

Biomass energy is energy generated or produced by living or once-living organisms. Plants receive the sun’s energy through photosynthesis and transform carbon dioxide and water into nutrients. They store this energy in biomass (carbohydrates).

We can convert this stored energy into useable energy in both direct and indirect ways. We can burn biomass directly to provide heat, turn it directly to electricity, or process it into biofuel (indirect).

Biomass Energy Source Examples

Today, wood and wood wastes are the most common biomass energy source. We can burn wood directly or convert it into pellet fuel or other fuel forms to generate energy. Other plants that can serve as fuel include corn, switchgrass, miscanthus, and bamboo. Wood waste, agricultural waste, municipal solid waste, manufacturing waste, sewage sludge, and landfill gas are the most common waste energy feedstocks.

Biomass energy
Biomass energy

Conversion of Biomass to Thermal Energy

Thermal conversion involves the application of heat to convert biomass to energy. The biomass feedstock is heated to burn, dehydrate, or stabilize by thermal conversion. Raw materials such as municipal solid waste (MSW) and scraps from paper or timber mills are the most common biomass feedstocks for thermal conversion.

The following processes produce different types of energy from biomass:

  • Direct firing
  • Co-firing
  • Pyrolysis
  • Gasification
  • Anaerobic decomposition

We must dry the biomass first before burning it. This process is called torrefaction. We heat biomass to around 200° to 320° Celsius (390° to 610° Fahrenheit) during torrefaction. The biomass dries out to the point that it can no longer absorb moisture and rot. It loses around 20% of its original bulk but keeps 90% of its original energy.

Torrefaction turns biomass into a dry, blackened substance from which we make briquettes. Briquettes made from biomass are hydrophobic, which means they reject water. This allows their storage in damp environments. The briquettes have a high energy density and are simple to burn when used in direct or co-firing applications.

Also read: Solar Energy- Definition, Advantages and Future

Direct Firing and Co-Firing

The majority of briquettes from torrefaction undergo direct burning. The steam generated during the firing process drives a turbine, which in turn drives a generator, which generates energy. This electricity can power machines or heat structures.

Biomass can also undergo co-firing, which means burning the briquettes along with fossil fuel. Biomass undergoes frequent co-firing with coal in power facilities. Co-firing reduces the requirement for additional biomass processing facilities and the demand for coal as well. Also, it reduces the amount of carbon dioxide and other greenhouse gases released by burning fossil fuels.

Pyrolysis

We heat biomass to 200° to 300° C (390° to 570° F) in the absence of oxygen during pyrolysis. This prevents it from combusting and changes the chemical composition of the biomass. Pyrolysis creates pyrolysis oil, a synthetic gas known as syngas, and a solid residue known as biochar.

Bio-oil

Pyrolysis oil or bio-oil is a form of tar. It finds application as a component in various fuels and plastics and gives energy upon burning. Scientists and engineers are researching pyrolysis oil as a possible substitute for petroleum.

Syngas

Syngas finds application as a fuel such as synthetic natural gas. It can also be converted to methane and used as a natural gas substitute. Clean syngas can be used for heat or energy or processed into biofuels, chemicals, and fertilizers for transportation.

Also read: Tidal Energy – Definition, Advantages, and Future

Biochar

The solid residue we obtain after the pyrolysis of biomass feedstock is biochar. Biochar has a number of merits over ordinary biomass feedstock. Let’s have a look at them.

  • When biomass burns or decomposes naturally or as a result of human action it releases large amounts of methane and carbon dioxide into the atmosphere. Biochar, on the other hand, sequesters or stores its carbon content. That is it is a great carbon sink. Carbon sinks are places that can store carbon-containing compounds, such as greenhouse gases.
  • When we reintroduce biochar to the soil, it can continue to absorb carbon and develop huge subsurface carbon sinks, resulting in negative carbon emissions and healthier soil.
  • Biochar carbon remains in the ground for centuries, slowing the growth in atmospheric greenhouse gas levels. Simultaneously, its presence in the earth can improve water quality, increase soil fertility, raise agricultural productivity, and reduce pressure on old-growth forests
  • Biochar also aids with soil enrichment. It is permeable and prevents pesticides and other nutrients from seeping into the runoff.

Gasification

Gasification directly converts biomass to energy. During gasification, we heat the biomass feedstock (typically Municipal Solid Waste) to over 700° C (1,300° F) with a controlled amount of oxygen. As the molecules break down, it produces the following two products:

  • Syngas
  • Slag

Anaerobic Decomposition

In landfills, anaerobic decomposition occurs when biomass is crushed and squeezed, resulting in an anaerobic (or oxygen-poor) environment. It is the breakdown of material by microbes, mainly bacteria, in the absence of oxygen.

Biomass decomposes in an anaerobic environment, producing methane, a useful energy source. This methane has the potential to replace fossil fuels.

Anaerobic decomposition
Anaerobic Decomposition

Anaerobic decomposition can be used on ranches and livestock farms in addition to landfills. Manure and other animal waste can be processed through anaerobic decomposition to meet the farm’s energy demands sustainably.

Also read: Wind Energy: Definition, Advantages, and Future

Advantages of Biomass Energy

Here are the major advantages of biomass energy that has made it a global player in the renewable energy sector:

  • Biomass is a sustainable energy source that is both clean and efficient.
  • The sun provides the initial energy, and plants or algae biomass can regenerate in a relatively short period. Hence it is a renewable source of energy.
  • Trees, crops, and municipal solid waste, which are the feedstock for biomass energy production, are all accessible regularly.
  • When we sustainably grow trees and crops, they can help to offset carbon emissions by absorbing CO2 through respiration. The quantity of carbon reabsorbed in some bioenergy processes even exceeds the amount of carbon produced during fuel processing or use.
  • We can collect many biomass feedstocks, such as switchgrass, on marginal lands or pastures without interfering with food crops.

Disadvantages of Biomass Energy

While biomass has various advantages, it is not an ideal energy source. We must examine its drawbacks as well which are as follows:

  • Water makes up to 50% of the biomass, which escapes throughout the energy conversion process. Hence the “energy density” of biomass is lower than that of fossil fuels.
  • According to scientists and engineers, transporting biomass more than 160 kilometers (100 miles) from its processing point is not cost-effective. However, turning biomass into pellets (rather than wood chips or larger briquettes) can boost the energy density of the fuel and make it easier to transport.
  • To grow the materials used in biomass energy, we require a vast area of space. This space will not always be available, especially in densely populated places such as cities.

Biomass Energy Future

Energy crops must be grown in vast quantities, requiring large swaths of land, if biomass is to make a significant dent in the usage of fossil fuels. Furthermore, biomass energy must be cost-competitive with conventional energy sources and biological carbon sequestration. If we can cultivate biomass in huge amounts at cheap cost along with research, development, and early deployment of “clean coal” technologies we could lower the cost of converting biomass to electricity and liquid fuels.

Conclusion

Biomass energy has emerged as a frontrunner as a viable alternative to fossil fuels as the search for alternatives to fossil fuels continues. It is a carbon-neutral fuel source with lower costs than fossil fuels and a wide range of applications.

However, several challenges are preventing it from becoming more widely adopted. More needs to be done, in particular, to address the issue of fuel efficiency, as well as challenges such as space and cost. The utilization of biomass energy, in particular, on a home and local level, can result in lower energy bills.

Do you have any thoughts on biomass energy and its prospects? Please share your thoughts in the comments section below.

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Fuel Cells- Definition, Advantages and Future

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Fuel Cells is a hot topic among scientists these days thanks to their wide range of applications. Their uses are so diverse that fuel cells have found a place even in the space program. In this blog, let me explain in detail the design, working, types and future scope of fuel cells.

Shall we begin?

What are Fuel Cells?

Fuel cells are electrochemical cells that use a pair of redox reactions to transform the chemical energy of a fuel (typically hydrogen) and an oxidizing agent (usually oxygen) into electricity. It finds various applications, including transportation, industrial/commercial/residential structures, and long-term grid energy storage in reversible systems.

Fuel cells are unique in that they may use a wide range of fuels and feedstocks and can power systems as large as a utility power plant and as small as laptop computers. Now, we are moving on to the design of fuel cells.

Also read: Solar Energy- Definition, Advantages, and Future

Fuel Cells Design

A fuel cell comprises 3 adjacent segments namely the anode, the electrolyte, and the cathode. At the intersections of these segments, redox reactions take place. Fuel is burned, water or carbon dioxide is produced, and an electric current is produced, which can be utilized to power electrical devices, commonly referred to as the load.

A fuel cell’s design elements include:

  • An electrolyte – It acts as a medium of transport between the electrodes. Most common electrolytes include potassium hydroxide, salt carbonates, and phosphoric acid, and it usually defines the type of fuel cell.
  • A fuel – The fuel undergoes oxidation reaction and supplies the ions. Hydrogen is the most common fuel.
  • Anode Catalyst – It breaks down the fuel into electrons and ions. We usually use fine platinum powder as the anode catalyst.
  • Cathode catalyst – It reacts with the ions that reach the cathode and transforms them into harmless compounds, the most common of which is water.
  • Gas diffusion layers that are resistant to oxidation.

Let me show you how fuel cells produce electricity from the fuel we supply.

Fuel Cells Working

In 1839, Sir William Robert Grove, a physicist invented the first fuel cell. The goal of a fuel cell is to generate an electric current that can do some work outside of the cell, such as powering an electric motor or lighting a city.

A catalyst at the anode promotes oxidation reactions in the fuel. As a result, hydrogen atoms are stripped of their electrons at the anode of a fuel cell. The hydrogen atoms have now become positively charged H+ ions.

At full rated load, a typical fuel cell produces a voltage of 0.6 to 0.7 V. If we require alternating current (AC), we must channel the DC output of the fuel cell via a conversion device called an inverter.

Reactions inside Fuel Cell

When the ions and electrons reach the cathode, they rejoin, and the two react with a third molecule, usually oxygen, to produce water or carbon dioxide. The following are the basic reactions that take place inside a fuel cell:

Anode side:  2H2 => 4H+ + 4e–  

Cathode side: O2+ 4H++ 4e–=> 2H2O

Net reaction: 2H2 + O2 => 2H2O

Fuel cell reaction

Different types of fuel cells

Depending on the electrolyte in use, there are different types of fuel cells. Here are some of them:

Alkali Fuel Cells

  • Alkali fuel cells use compressed hydrogen and oxygen to function.
  • Their electrolyte is usually a solution of potassium hydroxide (chemically, KOH) in water.
  • The efficiency is around 70%, and the operating temperature is between 150 and 200 degrees Celsius (about 300 to 400 degrees F).
  • The output of the cells ranges from 300 watts (W) to 5 kilowatts (kW).
  • However, they require pure hydrogen fuel, and their platinum electrode catalysts are costly. They can also leak, just like any other liquid-filled container.
  • In the Apollo spacecraft, alkali cells were employed to produce both electricity and drinking water.

Molten Carbonate Fuel Cells

  • The electrolyte of molten carbonate fuel cells (MCFC) consists of high-temperature salt carbonates (chemically, CO3).
  • The efficiency ranges from 60% to 80%, and the working temperature is around 650°C (1,200 degrees F).
  • The high temperature prevents the poisoning of cell by carbon monoxide, and waste heat can be recycled to generate more energy. However, the high temperature limits the materials and applications of MCFCs–they are likely too hot for domestic use.
  • In addition, the processes consume carbonate ions from the electrolyte, necessitating the injection of carbon dioxide to compensate.

Also read: Tidal Energy – Definition, Advantages, and Future

Phosphoric Acid Fuel Cell

  • The electrolyte of PAFCs is phosphoric acid, which is a non-conductive liquid acid that causes electrons to go from anode to cathode via an external electrical circuit.
  • Since the anode’s hydrogen ion generation rate is low, we use platinum as a catalyst to boost the ionisation rate.
  • The use of an acidic electrolyte is a major disadvantage of these cells. This accelerates the corrosion or oxidation of phosphoric acid-exposed components.
  • The operating temperature is between 150 and 200 degrees Celsius, and the efficiency ranges from 40 to 80% (about 300 to 400 degrees F). Phosphoric acid cells now available have outputs of up to 200 kW.

Solid Oxide Fuel Cells

  • Solid oxide fuel cells (SOFC) use a hard, ceramic composition of metal oxides such as calcium or zirconium as an electrolyte.
  • The efficiency is around 60%, and the output of the cells can reach 100 kW.
  • The working temperature is around 1,000 degrees Celsius (about 1,800 degrees F).
  • Further energy generation through waste heat recovery is possible. The high temperature, on the other hand, limits the applications of SOFC units, which are typically quite big.

Let’s have a look at the different applications of fuel cells.

Fuel Cells Applications

Fuel cell technology has a variety of applications. Currently, scientists are carrying out extensive research to develop a cost-effective fuel cell-powered automobile. The following are a few examples of the uses of this technology:

  • Fuel cell electric vehicles, or FCEVs, use clean fuels and are thus more environmentally benign than vehicles powered by internal combustion engines.
  • Many space voyages, like the Appolo space program, have relied on them for power.
  • In many rural regions, fuel cells are a major backup source of electricity.

Also read: Wind Energy: Definition, Advantages, and Future

Fuel Cells Advantages

Fuel cells outperform traditional combustion-based technologies, which are now in operation in many power plants and automobiles. They emit fewer greenhouse gases and zero atmospheric pollutants that contribute to smog and health issues. When pure hydrogen is the fuel, the only byproducts are heat and water. Traditional combustion systems use significantly more energy than hydrogen-powered fuel cells.

Fuel Cells Future

Hydrogen is the most abundant element in the universe, and a hydrogen ecosystem focusing on fuel cell technology has enormous promise. Unlike batteries, we can scale up fuel cell technology for passenger vehicles, buses, ships, and trains. Hydrogen will also power urban air mobility in the future.

Fuel cells could power our cars in the future, with hydrogen replacing the petroleum fuel currently used in most vehicles. Many automakers are investigating and developing transportation fuel cell technologies. Hyundai is pioneering hydrogen fuel cell technology in addition to increasing its array of battery, hybrid, and plug-in electric vehicles.

Shall we wrap up?

Conclusion

Due to its non-polluting nature and a vast range of applications, the future looks bright for fuel cells. Once we are able to cut down the cost of fuel cells and devise methods for the safe and long term storage of hydrogen, fuel cells would revolutionize the energy sector.

In case of any queries, please feel free to ask in the comments section. Happy Learning!