Science of Anaerobic Digestion

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Questions and Answers

What is the primary function of the digester in a bio-gas plant?

To release methane into the atmosphere

To mix cow-dung with water

To store bio-gas

To decompose the cow-dung slurry (correct)

Which of the following gases is NOT a product of the decomposition process in a bio-gas plant?

Hydrogen sulphide

Oxygen (correct)

Carbon dioxide

Methane

What makes bio-gas an excellent fuel compared to traditional fuels?

It contains up to 75% methane (correct)

It burns with smoke and leaves residue

It requires oxygen for combustion

It generates more carbon emissions

What is the main purpose of the slurry left behind after the bio-gas production process?

To serve as high-quality manure Signup and view all the answers

How does wind energy generate electricity in a windmill?

By converting the kinetic energy of wind into mechanical energy Signup and view all the answers

What is a wind energy farm?

A collection of several windmills working together Signup and view all the answers

What was one of the historical uses of wind energy before modern applications?

To pump water using windmills Signup and view all the answers

Why is Denmark referred to as the country of 'winds'?

It experiences a lot of windy weather Signup and view all the answers

Which day would a solar water heater be least effective in providing hot water?

a cloudy day Signup and view all the answers

Which of the following is not considered a bio-mass energy source?

nuclear energy Signup and view all the answers

Which energy source is not ultimately derived from the Sun's energy?

nuclear energy Signup and view all the answers

On what basis can energy sources be classified as non-renewable?

they take millions of years to form Signup and view all the answers

What is likely a limitation of extracting energy from the wind?

It is unpredictable and varies by location Signup and view all the answers

What is one principal advantage of solar cells?

They have no moving parts and require little maintenance. Signup and view all the answers

Why are solar cells advantageous in remote areas?

Power transmission lines are expensive and impractical. Signup and view all the answers

What material is primarily used to manufacture solar cells?

Silicon Signup and view all the answers

What challenge increases the cost of solar cell panels?

Silver is used for interconnection of cells. Signup and view all the answers

In which application are solar cells commonly used?

Artificial satellites and space probes. Signup and view all the answers

What natural phenomenon is the basis for tidal energy?

Gravitational pull of celestial bodies. Signup and view all the answers

How is tidal energy converted into electricity?

With turbines fixed at openings of dams across tidal areas. Signup and view all the answers

What limits the domestic use of solar cells?

Their high cost and low efficiency. Signup and view all the answers

What distinguishes nuclear fusion from nuclear fission in energy generation?

Fission breaks apart heavier nuclei to release energy. Signup and view all the answers

Which statement is true regarding the conditions required for nuclear fusion?

It requires extreme temperatures and pressures. Signup and view all the answers

How does a hydrogen bomb utilize nuclear fusion?

It uses the heat from fusion to sustain fission. Signup and view all the answers

What is the primary source of energy for the Sun?

Nuclear fusion reactions. Signup and view all the answers

What happens to the mass during a nuclear fusion reaction?

Mass is lost as energy according to Einstein's equation. Signup and view all the answers

What role does deuterium play in a hydrogen bomb?

It is one of the light nuclei that undergo fusion. Signup and view all the answers

What physical principle is common to both nuclear fission and fusion?

Both release energy from nuclear reactions. Signup and view all the answers

Which of the following statements about nuclear power generation is incorrect?

Fission involves the joining of lighter nuclei. Signup and view all the answers

What is necessary for wave energy systems to be viable?

High amplitude waves Signup and view all the answers

How does ocean thermal energy conversion generate energy?

By boiling ammonia using warm surface water Signup and view all the answers

What is a hot spring?

An outlet for steam and hot water from the earth's crust Signup and view all the answers

What is the primary process used to generate nuclear energy?

Nuclear fission Signup and view all the answers

What condition is necessary for ocean-thermal-energy conversion plants to operate efficiently?

A temperature difference of 20 K or more Signup and view all the answers

What type of energy is generated from the splitting of heavy atomic nuclei?

Nuclear energy Signup and view all the answers

What is a significant challenge of commercial energy exploitation from the sea?

Limited geographic locations for plants Signup and view all the answers

Which statement about geothermal energy production is true?

It requires specific geological conditions. Signup and view all the answers

Study Notes

Bio-Gas Plant

Bio-gas plants utilize a dome-like structure made of bricks to produce energy.
A slurry of cow dung mixed with water is fed into a sealed digester devoid of oxygen.
Anaerobic microorganisms decompose the slurry, generating gases such as methane, carbon dioxide, hydrogen, and hydrogen sulfide.
Bio-gas contains up to 75% methane, burns cleanly without smoke, and provides high heating capacity.
The remaining slurry is rich in nitrogen and phosphorus, serving as excellent manure.
Bio-waste and sewage efficient disposal contribute to energy and manure supply.

Wind Energy

Wind energy arises from unequal heating of land and water, generating air movement.
Historically harnessed by windmills for mechanical tasks like water pumping.
Modern windmills convert wind kinetic energy into electricity, primarily through turbines.
Wind energy farms consist of multiple windmills to generate electricity on a commercial scale.
Denmark is recognized as the "country of winds" due to its favorable wind conditions.

Solar Energy

Solar cells have no moving parts, minimal maintenance, and can operate without focusing devices.
Silicon is abundant, but special grade silicon for solar cells is limited in availability.
High production costs and silver used for connections make solar cells expensive.
Though costly, solar cells power scientific instruments and remote technology applications.
Solar panels are positioned on inclined rooftops for optimal sunlight exposure.

Tidal Energy

Gravitational pull by the moon causes sea level variations, producing tidal energy.
Tidal energy is harvested by constructing dams at narrow sea openings with turbines for electricity generation.
Suitable sites for tidal dams are geographically limited.

Wave Energy

Generated by strong winds across the sea, wave energy can be converted into electricity.
Effective wave energy harvesting depends on the strength of the waves.

Ocean Thermal Energy

The sun heats surface ocean water, creating a temperature differential with deeper water.
Ocean-thermal-energy conversion plants exploit this difference, requiring a minimum of 20 K.
Warm water boils a volatile liquid like ammonia, generating vapor to drive turbines.

Geothermal Energy

Formed by heated molten rocks in "hot spots," producing steam when subterranean water contacts hot rock.
Operational sites are scarce, limiting commercial viability, with current plants in New Zealand and the USA.

Nuclear Energy

Nuclear fission splits heavy atom nuclei like uranium, releasing substantial energy.
Fusion combines lighter nuclei into heavier ones, releasing energy in processes like those in the sun.
Fusion requires extreme conditions of temperature and pressure, notably used in hydrogen bombs.
Both fission and fusion have potential for generating large amounts of energy, but fission is currently commercially used.

Energy Sources Comparison and Environmental Considerations

Most energy sources are derived from solar energy, except geothermal and nuclear energy.
Limitations in harnessing energy exist for wind, waves, and tides due to consistency and geographical constraints.
Renewable energy sources are sustainable, while non-renewable sources are finite.
Ideal energy sources are efficient, environmentally friendly, and economically viable.
Solar cookers’ utility may be limited on cloudy or rainy days, influencing their broader application.
Increasing energy demand has environmental repercussions, necessitating measures for consumption reduction.

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Description

Explore the fascinating process of anaerobic digestion, focusing on the breakdown of cow-dung slurry by micro-organisms in a sealed chamber. Understand the significance of this method in waste management and biogas production. This quiz will test your knowledge about the principles and applications of this scientific process.