Solar Energy and Solar Collectors

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Questions and Answers

What is the primary purpose of solar energy collectors?

To power remote telecommunication stations

To convert solar energy directly into electricity

To heat air and water for domestic and industrial needs

To collect and transfer solar radiation to a fluid (correct)

What is the typical range of solar energy available in most places in India?

5-7.5 kWh/m2 (correct)

2.5-5 kWh/m2

10-15 kWh/m2

7.5-10 kWh/m2

What is the primary use of solar energy in cold climate regions?

To pump water

To heat air and water for domestic and industrial needs (correct)

To generate electricity using solar photovoltaic cells

To power street lighting

What is the goal of the Indian Renewable Energy Development Agency and the Ministry of Non-Conventional Energy Sources?

To install solar energy in more than a million houses in the shortest time Signup and view all the answers

What is the primary method of using solar energy indirectly?

Converting solar energy using solar photovoltaic cells Signup and view all the answers

What is the primary function of the transparent cover in a flat plate collector?

To prevent convection and reradiation Signup and view all the answers

What is the main advantage of a flat plate collector compared to other collectors?

It does not require a sun tracking system and is mechanically stronger Signup and view all the answers

What is the purpose of the vacuum in evacuated collectors?

To minimize heat loss through conduction and convection Signup and view all the answers

What is the main characteristic of a parabolic trough collector?

It concentrates solar radiation along a line Signup and view all the answers

What is the primary challenge associated with solar energy storage?

The availability of solar energy does not always coincide with the demand Signup and view all the answers

What is the primary function of the water storage tank in a solar water heater?

To store hot water for domestic use Signup and view all the answers

What is the purpose of the refrigerant in a solar thermal pump?

To transfer heat to the turbine Signup and view all the answers

How do solar cookers typically concentrate sunlight onto the cooking area?

Using reflective surfaces such as mirrors or reflective panels Signup and view all the answers

What happens to the water in the basin of a solar still during the distillation process?

It evaporates due to solar heat Signup and view all the answers

What is the primary advantage of using solar pumps for irrigation?

They are more environmentally friendly and low-maintenance Signup and view all the answers

What is the primary function of a solar collector in a solar thermal system?

To convert solar radiation into heat energy Signup and view all the answers

What is the main difference between concentrating and non-concentrating solar collectors?

The area of the absorber relative to the interceptor Signup and view all the answers

What is the purpose of a tracking system in concentrating solar collectors?

To track the movement of the sun for optimal energy absorption Signup and view all the answers

What is the typical application of concentrating solar collectors?

Generating steam for industrial processes Signup and view all the answers

What is the definition of concentrating ratio (CR) in solar collectors?

Ratio of aperture area to receiver area Signup and view all the answers

What happens to the water vapor when it reaches the undersurface of the roof in a solar still?

It condenses Signup and view all the answers

What type of solar power plant uses a solar pond?

Low temperature Signup and view all the answers

What is the purpose of the condensate channel in a solar still?

To collect and drain condensed water Signup and view all the answers

What is the function of the heliostats in a central receiver system?

To reflect radiation Signup and view all the answers

What is the purpose of the boiler in a central receiver system?

To heat the working fluid Signup and view all the answers

What is the working fluid used for in a central receiver system?

To drive a turbine Signup and view all the answers

What is the purpose of the mirrors in a central receiver system?

To reflect radiation Signup and view all the answers

What is the result of the working fluid being heated in a central receiver system?

Mechanical energy is produced Signup and view all the answers

What is the final product of a central receiver system?

Electrical energy Signup and view all the answers

What is the advantage of using a central receiver system?

Higher efficiency Signup and view all the answers

What is the primary reason for storing energy output from solar devices during high insolation times?

To match the generation of energy with the load demand during peak demand times Signup and view all the answers

What is the most commonly used means of chemical energy storage?

Lead acid batteries Signup and view all the answers

What is the process by which solar energy is stored in plants?

Photosynthesis Signup and view all the answers

What is the primary characteristic of superconducting materials used in electromagnetic energy storage?

Zero resistance to electricity flow when cooled below a critical temperature Signup and view all the answers

What is the primary advantage of sensible heat storage?

Reversible charging and discharging for an unlimited number of times Signup and view all the answers

What is the primary advantage of using water as a storage medium in sensible heat storage systems?

It has a high specific heat, enabling it to store more heat per unit mass. Signup and view all the answers

What is the primary limitation of using water as a storage medium in sensible heat storage systems?

It has a limited temperature range of operation, making it unsuitable for certain applications. Signup and view all the answers

What is the primary advantage of latent heat storage systems compared to sensible heat storage systems?

They are more compact for a certain heat storage capacity. Signup and view all the answers

What is the primary function of the gradient non-convective zone in a solar pond?

It prevents the mixing of the hot and cold brine solutions. Signup and view all the answers

What is the primary purpose of the heat exchanger in a solar pond system?

To remove heat from the brine solution by evaporating a refrigerant. Signup and view all the answers

Study Notes

Solar Energy and Its Utilization

Solar energy is a clean, cheap, and abundantly available renewable energy source.
Solar energy can be used directly as thermal energy and indirectly using solar photovoltaic cells to convert it to electricity.

Solar Collectors

Solar collectors are devices that collect solar radiation and transfer the absorbed energy to a fluid.
The main types of solar collectors are:
- Non-concentrating (flat plate) collectors
- Concentrating collectors (parabolic dish, parabolic trough, power tower, and stationary concentrating collectors)
The important features of a solar collector include:
- Collector efficiency
- Concentrating ratio (CR)
- Temperature range

Types of Solar Collectors

Flat Plate Collectors

Absorbs both direct and diffuse solar radiation
Does not require a sun-tracking system
Simple construction and low maintenance

Evacuated Collectors

Uses a vacuum-sealed glass or metal tube to minimize heat loss
Inner tubes contain a heat-absorbing material that converts sunlight into heat

Parabolic Trough Collectors

Uses a parabolic reflector to focus sunlight onto a receiver
Can achieve high temperatures and efficiencies

Mirror Strip Collectors

Uses a series of curved mirrors to focus sunlight onto a receiver
Can be used for both heating and cooling applications

Solar Energy Storage

Solar energy storage systems are necessary to match energy generation with load demand
The main types of solar energy storage systems are:
- Thermal energy storage
- Chemical energy storage
- Electrical energy storage
- Hydrogen energy storage
- Electromagnetic energy storage
- Biological energy storage

Thermal Energy Storage

Can be achieved through sensible heat storage or latent heat storage
Sensible heat storage uses the heat capacity of a material to store energy
Latent heat storage uses the phase change of a material to store energy

Solar Pond

A solar pond is a large, shallow pond with a salt concentration gradient
The top layer has a low salt concentration and is at atmospheric temperature
The bottom layer has a high salt concentration and can reach temperatures of 70-85°C
The hot brine solution can be used to generate electricity

Solar Water Heater

A small capacity water heating system using natural circulation
Suitable for domestic hot water supply
Consists of a flat plate collector and a water storage tank

Solar Thermal Pump

Uses solar radiation to generate mechanical power for pumping water
Suitable for irrigation pumping and has low running and maintenance costs

Solar Cookers

A device that uses sunlight to cook or heat food
Can be used for both domestic and industrial applications### Solar Cookers
Harness energy from the sun and convert it into heat for cooking
Typically have reflective surfaces (mirrors or panels) that concentrate sunlight onto a cooking area
Reflective surfaces focus sunlight onto a specific point, increasing intensity
Cooking area designed to absorb and retain sunlight, using materials with high solar absorption properties (blackened surfaces, dark pots)
Dark colors absorb more sunlight and convert it into heat, raising the temperature of the cooking area
Heat is transferred to the cooking vessel or surface, cooking the food

Solar Distillation

Process of converting saline water into pure water using solar radiation
Solar device used is called a solar still
Solar still consists of a shallow blackened basin filled with saline or brackish water to be distilled
Basin is covered with a sloping transparent roof, allowing sun rays to pass through and be absorbed by the blackened surface
Water evaporates due to solar heat, rises to the roof, cools, and condenses
Condensed water is collected by the condensate channel and drained out from the solar still

Solar Thermal Power Plants

Can use different systems, including:
- Low temperature solar power plant using flat plate collectors
- Low temperature solar power plant using solar pond
- Medium temperature solar power plant using focusing collectors
- High temperature solar power plant using distributed collector systems (solar farms)

Central Receiver System or Tower Power Plant

Principle: focus incoming solar radiation to a central receiver or boiler using thousands of plane reflectors (heliostats)
Mirrors are installed on the ground and oriented to reflect direct beam radiation into the absorber or receiver (boiler)
Boiler is mounted on a tall tower, allowing it to be in the field of view of all mirrors at all hours of the day
Beam radiation is absorbed by black pipes, heating the working fluid, which drives a turbine and produces mechanical energy
Turbine is coupled to an alternator, producing electrical energy

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Description

Learn about solar energy, its benefits, and its utilization through solar collectors and photovoltaic cells. Explore its applications in heating and electricity generation.