What is a Backup system?

The energy from fossil fuels like petroleum, coal, and natural gas is one of the primary energy resources that powers the whole world, be it power generation or automobiles. But unfortunately, these resources are on the verge of extinction due to their overexploitation and the level of pollution they cause to the environment. Carbon emission is one of the worst by-product from burning fossil fuels. Gas such as carbon dioxide is the primary culprit of the greenhouse effect and global warming. Also, these energy resources fall under the category of non-renewable energy sources as they will lead to extinction in the near future. Due to these reasons, humans are continuously in search of such resources, which may serve as backup sources to fuel their daily needs once these non-renewable energy resources get exhausted. These resources are non-polluting as well as add to long-term sustainability. All renewable energy sources, hybrid energy sources, clean energy sources, etc. fall under the category of backup energy systems.

Renewable energy resources are those resources that are present in ample amounts and cannot be exhausted in the near future. Some systems, like hybrid energy systems, are even developed that uses a combination of two modes of energy, which can provide excellent energy and fuel savings. A new mode of fuel known as 'blue fuel' from hydrogen, is the future of fuel and power, it accounts for zero percent carbon emission, and is known as a clean fuel.

Here, in this article, some of the sustainable energy sources developed recently are discussed. These sources have tremendous potential to serve as a backup for mankind to cover up their energy demands.

Hybrid Energy systems

In recent years, energy systems are mostly used in the automobile domain. These systems are preferably known as automotive hybrid systems. The term hybrid signifies combined power and energy steerage system. The hybrid system mostly uses twin energy sources such as solar and wind, electric and fossil fuel-powered, etc. The electric and fossil fuel-powered systems are mostly employed in automobiles.

In the fossil fuel and electric hybrid systems, fuels used are mostly petrol and diesel, along with electric energy from storage cells. A hybrid automobile system has internal combustion (IC) engine along with an electric motor. The automobile makes use of multiple power storage cells (preferable lithium-ion cells) that powers the electric motor. These systems can serve a number of purposes. When the vehicle is making an uphill climb a huge amount of energy is needed, instead of consuming the energy solely from the IC engine, the energy is divided based on the needs. The controller of the hybrid system after calculating power and torque needed switches on the electric motor that provides additional torque in support of the torque produced by the IC engine. Thus the efficiency of the vehicle is maintained keeping minimum fuel consumption. Also, during cruising for economy mode, the IC engine is kept off, while driving energy from the motor is an excellent way of fuel consumption.

The batteries are charged by means of an alternator driven by the IC engine crankshaft. Other means of recharging like regenerative braking and solar energy recharging are also used.

These systems can also serve as a power generation system. For instance, solar-wind energy hybrid systems are used for power supply in remote areas. These systems are comprised of tall windmills with an added system for solar energy consumption with solar photovoltaic cells, or PV cells. During cloudy weather or rainy seasons, when solar energy is not ample, wind energy is used for power generation and transmission, as the flow velocity of wind is more during these seasons. The blades of a windmill coupled to a generator serve the purpose of electricity generation. During the summer season with ample solar energy, the PV cells are charged due to chemical reactions and act as a means of power source.

Hydrogen fuel cells

Fuel cells are small energy conversion units, that convert the chemical energy of fuel along with an oxidizing agent into electricity. The fuel cells perform this task due to redox reactions. The fuels, unlike conventional batteries that store the energy, need a continuous supply of fuel and oxidizing agents to keep the chemical reaction sustained.

In a hydrogen fuel cell, the fuel used is primarily hydrogen and the oxidizing agent used is oxygen gas. But hydrogen is not easily available in the atmosphere hence it needs to be extracted before it can be used as fuel. There are several ways developed recently to extract hydrogen like- natural gas reforming, electrolysis of water, renewable liquid reforming, fermentation, high-temperature water splitting, photo-biological water splitting, and photoelectrochemically water splitting.

These fuel cells do not get exhausted on energy or need recharging, they can continuously supply electricity as long as the input sources are supplied. A hydrogen fuel cell has two electrodes, a cathode, and an anode. A suitable electrolyte is maintained in between these two electrodes. Hydrogen gas is fed into an anode and air/oxygen is fed into the cathode. A suitable catalyst at the anode breaks down the hydrogen into its constituent protons and electrons. The electrons move through the anode and run through the circuit causing a current flow, while the protons migrate through the electrolyte and reach the cathode, and react with oxygen to form water and heat.

Fuel cells have great potential to power the future, both for power plants and automobiles. A fuel cell has higher efficiency than any conventional power source. The energy conversion efficiency of a fuel cell is more than 60%. Also, the by-product of a hydrogen fuel cell is only heat and water which has zero influence on the environment regarding pollution.

Carbon Capture and Utilization (CCU) system

It is a recent technology advancement to store the released carbon dioxide gas before it reaches the atmosphere. These stored carbon dioxide gas is processed further and reused as a clean energy source. Exhausts from power plants, automobiles, and other sources are the primary producers of carbon dioxide and account for more than 90% of greenhouse gas production.

The stored carbon dioxide gas can be converted into a useable fuel source known as carbon-neutral fuels. The primary by-products lie in the alcohol family-like methanol that acts as a biofuel for energy generation purposes. It can also be converted to ethanol that can be upgraded into gasoline and jet fuels. The aqueous catalytic process is usually used to convert the stored carbon dioxide gas into carbon-neutral fuels.

Context and Applications

The topic is widely taught in many undergraduate and postgraduate degree courses like:

• Bachelors in Technology (Mechanical Energy)
• Masters in Technology (Mechanical Energy)
• Masters in Technology (Hybrid Systems)
• Masters in Technology (Energy Systems)

Practice Problems

1. What is the abbreviation for CCU?

1. Carbon capture and use
2. Carbon dioxide capture and utilization
3. Carbon capture and utilization
4. Carbon capture and usability

Answer: Option c

Explanation: The abbreviation for CCU is carbon capture and utilization.

2. What is the gas used in the cathode of a hydrogen fuel cell?

1. Oxygen
2. Methane
3. Natural gas
4. None of these

Answer: Option a

Explanation: The gas used in the cathode of a hydrogen fuel cell is oxygen.

3. What is the energy efficiency that is achieved by using fuel cells over conventional power systems?

1. 70%
2. 80%
3. 60%
4. 40%

Answer: Option c

Explanation: 60% energy conversion efficiency can be achieved by using a fuel cell.

4. What are hybrid systems?

1. Any system that uses a fuel cell
2. Any system that uses two modes of energy generation
3. Any system that uses a renewable energy source
4. Both b and c

Answer: Option b

Explanation: A hybrid system is a single unit system that uses two modes of energy generation.

5. What is/are the by-product(s) of a hydrogen fuel cell?

1. Water
2. Heat
3. Carbon
4. Both a and b

Answer: Option d

Explanation: The by-products of a hydrogen fuel cell are water and heat.