Solar material system components. There is no disposal needed

Solar energy is becoming more and more vital these days due to the growing demand in green renewable energy. All over the world, equipment and systems used are very similar. Therefore, this project report majorly discusses the basic equipment used, with attention to collectors.

Classification of solar energy systems are based on the heat transfer medium used in the collector. Generally, the medium used are air and water.

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1. Air heating systems

2. Liquid heating systems

Air heating systems

Text After:

Air-heating systems flow air from collector to space through ducts. Air systems are very cost-efficient because there is no requirement of heat exchanger and the temperature of the from collector inlet is low throughout the day. Moreover, air system is free from the problems like freezing and overheating which results in corrosion and wear of the material system components. There is no disposal needed for the air and also air cost nothing.

However, space requirement for air heating systems are higher because of ducts which accommodate more space as compared to pipes and pumps. Also, storage of thermal energy of air is also very difficult process. In domestic use, most of the air heating systems are also used to preheat water by using air to liquid heat exchanger. Following is the general air space heating and domestic water heating system in which basic components of the system is shown.

 

Liquid-Heating System

As name suggested this system uses liquid as energy transferring medium. Important concern in liquid heating systems is to protect Liquid in collector i solar collector which can damage the system. Thus, it is highly crucial to set the freeze tolerance for the fluid running in collector before designing the equipment’s for the whole system. Although, freezing conditions are rare but ample amount of money is invested on this expensive solar equipment hence its necessary to study every possible failure in the system. Following is schematic diagram for liquid heating system without using any non-freezing equipment.

 

Figure 2 Simplified Schematic of Indirect Nonfreezing System

 

 

Following Freeze protection can be used to ensure proper working of solar collector

1.       Recirculating warm storage water through the collectors.

2.       Continually flushing the collectors with cold water.

3.       Isolating collectors from the water and draining them.

4.       Using the non-freezing liquid to transmit heat from the solar collector to storage

 

From above techniques only 3 and 4 are used I practical and rest of the them are not approved by sanctioning bodies or recommended by manufacturers.

 

 

 

Drain back Freeze Protection

 In this method water-heating system (Figure 3) uses ordinary water as the heat transport medium between the collectors and thermal energy storage. Reverse-draining (or back-siphoning) the water into a drain back tank located in a nonfreezing environment protects the system from freezing whenever the controls turn off the circulator pump or a power outage occurs.

 

Figure 3 Simplified Schematic of Indirect Drainback

 

SOLAR THERMAL ENERGY COLLECTORS

A solar thermal collector is a device which captures the solar radiation and collects the heat. These collectors are generally mounted on the roof and are designed in such way to withstand different weather conditions. Solar collectors are highly used for heating the domestic water. However, using number of solar collectors in arrays are used to generate the electricity.

Types of Solar Collectors

Solar collectors depend on air heating, liquid heating, or liquid vapor phase change to transfer heat.

Liquid-Heating Collectors-

a) Flat-plate collector is used in liquid heating. It consists of  absorber plate on which black coating is done.Upper section is the transparent cover on which solar radiation fa;;s .This cover is transparent to coming radiation such that most of the light eneters the collector however it is impenetrable for the solar radiation which is trapped inside.  Following is the cross-section of flat plate liquid collector.The collector box is given with insulation to eliminate any heat loss to the surrounding.Effciency of the collector remains high until  160F and it drops significantly after this temperature.However it can supply water upto 200 F.

 

 

Figure 4 Flat-plate collector

Advantages

·         Simple Construction

·         Low relative Cost

·         No moving parts

·         Relative ease of repair

·         Durability

 

b) Evacuated Tube-Components are basically same in this type of collector as that of the flat plate collector. But the design and arrangement of the components is the prime reason of high efficiency of this collector type. Absorber in this type is closed in a glass vacuum tube. Material used for absorber is a simple copper fin tube on a copper sheet, a large copper cylinder in ICS applications. If we use large copper cylinder than phase-change fluid is used to transfer the heat to a common manifold where the working fluid circulates. The vacuum created by the glass tube reduces convection and conduction losses, so the tubes can operate at higher temperatures than flat-plate collectors. Like flat-plate collectors, they collect both direct and diffuse radiation.

 

 

 

Figure 5 Evacuated Solar Collector

 

 

 

Advantages

·         High-temperature capability,

·         The evacuated-tube collector is favored for energizing heat-driven air-conditioning equipment.

·         Ideal for high temperature applications such as boiling water and steam production

·         Work exceptionally well on cloudy/overcast days

·         Tubes permit high heat retention and so much of the heat collected during the day can be retained during overcast days and through the night

 

Flat-plate and evacuated-tube collectors are usually mounted in a fixed position. Concentrating collectors are available that must be arranged to track the movement of the sun. These are mainly used for high-temperature industrial applications above 240°F.

2. Air-Heating Collectors. Air-heating collectors have same configuration as flat plate liquid collector. The prime distinction between the two is the design of the absorber plate and flow passages. Working fluid in this type is air which has very poor heat transfer properties therefore in this case to achieve higher efficiency and make use of maximum solar energy, air is allowed to flow over the entire absorbing plate surface and mostly both on front and backside of the plate. Although this system uses large surface area, but still value of overall coefficient is less as compared to the liquid solar collector. As no heat exchangers are required in these types of collectors therefore they are usually operated in the low temperature of range for space heating applications.

Air collectors can be attached to the roof or side of a building to create a plenum for the preheated air. The collector is simply the siding material with many small holes through which the air is drawn, thus warming the air for space-heating or drying applications.

Figure 6 Solar thermal air collector

 

3. Liquid-Vapor Collectors. A third class of collectors uses liquid-vapor phase change to transfer heat at high efficiency. These collectors feature a heat pipe (a highly efficient thermal conductor) placed inside a vacuum sealed tube (Figure 5B). The heat pipe contains a small amount of fluid (e.g., methanol) that undergoes an evaporating/condensing cycle. In this cycle, solar heat evaporates the liquid, and the vapor travels to a heat sink region, where it condenses and releases its latent heat. This process is repeated by a return feed of the condensed fluid back to the solar absorber. Most phase-change fluids have low freezing temperatures, so the heat pipe offers inherent protection to the tubes from freezing and overheating, but not to the fluid being heated. This self-limiting temperature control is a unique feature of the evacuated heat pipe collector.

 Solar energy is becoming more and more vital these days due to the growing demand in green renewable energy. All over the world, equipment and systems used are very similar. Therefore, this project report majorly discusses the basic equipment used, with attention to collectors.

Classification of solar energy systems are based on the heat transfer medium used in the collector. Generally, the medium used are air and water.

1. Air heating systems

2. Liquid heating systems

Air heating systems

Text After:

Air-heating systems flow air from collector to space through ducts. Air systems are very cost-efficient because there is no requirement of heat exchanger and the temperature of the from collector inlet is low throughout the day. Moreover, air system is free from the problems like freezing and overheating which results in corrosion and wear of the material system components. There is no disposal needed for the air and also air cost nothing.

However, space requirement for air heating systems are higher because of ducts which accommodate more space as compared to pipes and pumps. Also, storage of thermal energy of air is also very difficult process. In domestic use, most of the air heating systems are also used to preheat water by using air to liquid heat exchanger. Following is the general air space heating and domestic water heating system in which basic components of the system is shown.

 

Liquid-Heating System

As name suggested this system uses liquid as energy transferring medium. Important concern in liquid heating systems is to protect Liquid in collector i solar collector which can damage the system. Thus, it is highly crucial to set the freeze tolerance for the fluid running in collector before designing the equipment’s for the whole system. Although, freezing conditions are rare but ample amount of money is invested on this expensive solar equipment hence its necessary to study every possible failure in the system. Following is schematic diagram for liquid heating system without using any non-freezing equipment.

 

Figure 2 Simplified Schematic of Indirect Nonfreezing System

 

 

Following Freeze protection can be used to ensure proper working of solar collector

1.       Recirculating warm storage water through the collectors.

2.       Continually flushing the collectors with cold water.

3.       Isolating collectors from the water and draining them.

4.       Using the non-freezing liquid to transmit heat from the solar collector to storage

 

From above techniques only 3 and 4 are used I practical and rest of the them are not approved by sanctioning bodies or recommended by manufacturers.

 

 

 

Drain back Freeze Protection

 In this method water-heating system (Figure 3) uses ordinary water as the heat transport medium between the collectors and thermal energy storage. Reverse-draining (or back-siphoning) the water into a drain back tank located in a nonfreezing environment protects the system from freezing whenever the controls turn off the circulator pump or a power outage occurs.

 

Figure 3 Simplified Schematic of Indirect Drainback

 

SOLAR THERMAL ENERGY COLLECTORS

A solar thermal collector is a device which captures the solar radiation and collects the heat. These collectors are generally mounted on the roof and are designed in such way to withstand different weather conditions. Solar collectors are highly used for heating the domestic water. However, using number of solar collectors in arrays are used to generate the electricity.

Types of Solar Collectors

Solar collectors depend on air heating, liquid heating, or liquid vapor phase change to transfer heat.

Liquid-Heating Collectors-

a) Flat-plate collector is used in liquid heating. It consists of  absorber plate on which black coating is done.Upper section is the transparent cover on which solar radiation fa;;s .This cover is transparent to coming radiation such that most of the light eneters the collector however it is impenetrable for the solar radiation which is trapped inside.  Following is the cross-section of flat plate liquid collector.The collector box is given with insulation to eliminate any heat loss to the surrounding.Effciency of the collector remains high until  160F and it drops significantly after this temperature.However it can supply water upto 200 F.

 

 

Figure 4 Flat-plate collector

Advantages

·         Simple Construction

·         Low relative Cost

·         No moving parts

·         Relative ease of repair

·         Durability

 

b) Evacuated Tube-Components are basically same in this type of collector as that of the flat plate collector. But the design and arrangement of the components is the prime reason of high efficiency of this collector type. Absorber in this type is closed in a glass vacuum tube. Material used for absorber is a simple copper fin tube on a copper sheet, a large copper cylinder in ICS applications. If we use large copper cylinder than phase-change fluid is used to transfer the heat to a common manifold where the working fluid circulates. The vacuum created by the glass tube reduces convection and conduction losses, so the tubes can operate at higher temperatures than flat-plate collectors. Like flat-plate collectors, they collect both direct and diffuse radiation.

 

 

 

Figure 5 Evacuated Solar Collector

 

 

 

Advantages

·         High-temperature capability,

·         The evacuated-tube collector is favored for energizing heat-driven air-conditioning equipment.

·         Ideal for high temperature applications such as boiling water and steam production

·         Work exceptionally well on cloudy/overcast days

·         Tubes permit high heat retention and so much of the heat collected during the day can be retained during overcast days and through the night

 

Flat-plate and evacuated-tube collectors are usually mounted in a fixed position. Concentrating collectors are available that must be arranged to track the movement of the sun. These are mainly used for high-temperature industrial applications above 240°F.

2. Air-Heating Collectors. Air-heating collectors have same configuration as flat plate liquid collector. The prime distinction between the two is the design of the absorber plate and flow passages. Working fluid in this type is air which has very poor heat transfer properties therefore in this case to achieve higher efficiency and make use of maximum solar energy, air is allowed to flow over the entire absorbing plate surface and mostly both on front and backside of the plate. Although this system uses large surface area, but still value of overall coefficient is less as compared to the liquid solar collector. As no heat exchangers are required in these types of collectors therefore they are usually operated in the low temperature of range for space heating applications.

Air collectors can be attached to the roof or side of a building to create a plenum for the preheated air. The collector is simply the siding material with many small holes through which the air is drawn, thus warming the air for space-heating or drying applications.

Figure 6 Solar thermal air collector

 

3. Liquid-Vapor Collectors. A third class of collectors uses liquid-vapor phase change to transfer heat at high efficiency. These collectors feature a heat pipe (a highly efficient thermal conductor) placed inside a vacuum sealed tube (Figure 5B). The heat pipe contains a small amount of fluid (e.g., methanol) that undergoes an evaporating/condensing cycle. In this cycle, solar heat evaporates the liquid, and the vapor travels to a heat sink region, where it condenses and releases its latent heat. This process is repeated by a return feed of the condensed fluid back to the solar absorber. Most phase-change fluids have low freezing temperatures, so the heat pipe offers inherent protection to the tubes from freezing and overheating, but not to the fluid being heated. This self-limiting temperature control is a unique feature of the evacuated heat pipe collector.