Explore topic-wise InterviewSolutions in .

• Hydroelectric plants are advantageous in some respect while in some aspects it does create problems.
• Hydroelectric power generation does not need burning of fuels. Therefore, there is no problem regarding combustion of fuels and release of toxic pollutants.
• Electricity can be obtained as and when required if there is enough water in the reservoir.
• Water is replenished every time when there is sufficient rainfall.
• All the above facts give an impression that hydroelectric power generation is eco-friendly but it is not.
• Many villages and settlements are submerged when a dam and reservoir is constructed. The displaced people are given re-settlement, but it causes lot of emotional trauma to people.
• Biodiversity is affected as forest lands is submerged. The river flow is obstructed by the dam which affects the aquatic organisms residing in such water.
• Due to excessive pressure of water on land, it is said that the region gets prone to earthquakes.

• Hydroelectric energy, solar energy and wind energy is obtained respectively from flowing water, solar radiations and flowing wind.
• These sources, i.e. water reservoirs, sun and the wind are inexhaustible and sustainable. They will not be finished.
• On the contrary, the conventional energy sources such as coal and fossil fuels have limited reserves.
• They cannot be renewed and may get exhausted in future. Hydroelectric energy, solar energy and wind energy can be replenished and hence they are called renewable.

1. Solar panels can be constructed by connecting solar photovoltaic cells in either series or in parallels.

2. The combinations are done in such a way that it can give the desired potential difference and the current.

3. Solar strings are then made by joining solar panels in a series.

4. When solar strings are joined in parallel; they form solar array.

5. Therefore, by proper combinations, it becomes possible to produce energy from MW to MW using solar photovoltaic cells.

• Nuclear fission reaction is a type of chain reaction.
• In nuclear power plants these reactions are closely controlled.
• If these reactions are not managed properly, there can be more production of neutrons in an uncontrolled way.
• Each released neutron further causes fission of 3 Uranium (U-235) atoms, such uncontrolled reactions can cause hazardous accidents, hence ft is absolutely necessary to control the fission reaction in nuclear power plants.

i. False. 

(In thermal power plant, the turbines work on steam. The turbines working on solar energy are not used.)

ii. True. 

(Nuclear waste disposal is the greatest problem. It produces highly toxic effects in any ecosystem. Therefore, disposing such radioactive substances becomes a major challenge.)

iii. False. 

(The efficiency of power generation using natural gas plant is higher than that of power generation plant based on coal.)

iv. False. 

(Energy obtained from nuclear fission is not eco-friendly, because if accidents happen it leads to hazardous accidents.)

v. False. 

(In hydroelectric power plant, the potential energy in water stored in dam is converted into kinetic energy of water. The forceful downpour of flowing water causes this kinetic energy.)

• Generators work on the principles of electromagnetic induction.
• For this the generator must be rotated.
• For this purpose, there is a turbine for each generator.
• This rotation needs energy. The turbines are different according to the type of energy source that is used for its rotation.
• Therefore, the construction of turbine is different for each power plant.

• In nuclear power plants neutrons are bombarded on atom of Uranium – 235.
• This causes conversion of Uranium – 235 into its isotope U – 236.
• U-236 is very unstable and thus forms atoms of Barium and Krypton by nuclear fission. This forms 3 neutrons and 200 MeV energy.
• In a similar way three more Uranium – 235 atoms are subjected to nuclear fission which then releases energy.
• The neutrons released are again used for further nuclear fission reactions. In this way nuclear fission reactions are carried out in controlled manner in nuclear power plants.

• The photovoltaic solar cells can be connected in a series or in parallel to make a solar panel.
• When solar cells are connected in a series, the potential difference of individual cells are added in the combination, however the currents from individual cells are not added.
• When solar cells are connected in parallel, the currents of the individual cells are added in the combination, but the potential differences from individual cells are not added.
• Through such connections the required potential difference and current can be obtained.
• Many such solar panels are connected in series and in parallel to generate required current and potential difference.
• When many solar panels connected in series they form a solar string. Many solar strings connected in parallel make a solar array. In such manner we can get the required amount of energy by connecting solar panels.

i. Anjanvel. 

(All others are places having nuclear power plants.)

ii. Kudankulam. 

(All others are places having power plants based on natural gas.)

iii. Tarapur. 

(All others are places having hydroelectric projects.)

iv. Edible oil. 

(All others are fossil fuels.)

v. Nuclear energy. 

(All others are eco-friendly green energy types.)

Wind, solar, geothermal, biomass and hydroelectric power are some examples of renewable energy.

(1) Green energy means eco-friendly form of energy which does not cause environmental problems and are non-exhaustible, perpetual and sustainable.

(2) These sources of energy do not produce toxic gases or other pollutants, therefore they are safe. 

(3) Examples of green energy: 

(i) Hydroelectric energy 

(ii) Wind energy 

(iii) Solar energy 

(iv) Energy obtained biofuels.

Renewable energy is energy that is produced from sources which will not get exhausted within a human’s life time.

Fossil fuels like petrol, diesel or natural gas when burnt, emit toxic gases and soot particles. Thus, fossil fuels cause air pollution. Burning of fossil fuels cause increased levels of carbon dioxide, carbon monoxide and nitrogen dioxide. The increased carbon dioxide emission results in global warming. Nitrogen oxide results later in acid-rain. Soot particles generated through burning of fuels cause respiratory problems Like asthma.

Moreover, the fossil fuels are non-renewable and exhaustible fuels. They have to be explored from the deeper layers of the earth causing lots of environmental problems. Green energy is sustainable, renewable and abundant. It never creates any environmental problems and is nonpolluting. Thus, energy obtained from fossil fuels is not at all a green energy.

Fossil fuels are exhaustible in their amount. We have been using these extensively in the past 100 years and hence it may get over soon. It is a nonrenewable resource.

Geothermal energy, tidal energy and hydroelectric power are renewable energy resources which are not dependent on sun. Geothermal energy utilizes the Earth’s internal heat, tidal energy relies on the gravitational pull of the moon, and hydropower relies on the flow of water.

The most used energy resource is coal, i.e. fossil fuel based energy followed by hydroelectric energy.

I. Advantages:

• While generating the power through solar radiations, no fuel is burnt.
• Solar energy generation thus does not create any type of pollution. The technology can be completely utilized in regions with abundant sunlight.
• Solar energy is eco-friendly, green energy.

II. Limitations:

• Sunlight is available only during day time. Thus solar cells can generate power only during day.
• In rainy season and in cloudy conditions, solar power generation suffers.
• The power present in the solar cells is DC while most of the domestic equipments work on AC.

i. The solar cells shown in the diagram (a) are connected in series. This gives maximum potential difference.

ii. Advantage of Solar energy: Solar energy is ecofriendly which does not create pollution. It is boundless source.

Disadvantage of solar energy: Solar energy is available only when sun is in the sky. Therefore, it has to be stored in batteries.

iii. Steam turbine is the device shown in the above diagram.

iv. Turbine is a device with the blades. When the flow of liquid or gases is directed on the blades of the turbine, they rotate. The rotation produces kinetic energy. This turbine is then used to rotate the magnet in the electric generator. For this purpose, turbines are connected with the generators. The magnets rotate and produce electric energy by electromagnetic induction. The turbines working on steam are used in large commercial power generation plants.