Tidal Energy

Tidal energy is produced by the surge of ocean waters during the rise and fall of tides. Tidal energy is a renewable source of energy. During the 20th century, engineers developed ways to use tidal movement to generate electricity in areas where there is a significant tidal range the difference in area between high tide and low tide. All methods use special generators to convert tidal energy into electricity.

Tidal energy production is still in its infancy. The amount of power produced so far has been small. There are very few commercial-sized tidal power plants operating in the world. The first was located in La Rance, France. The largest facility is the Sihwa Lake Tidal Power Station in South Korea. The United States has no tidal plants and only a few sites where tidal energy could be produced at a reasonable price. China, France, England, Canada, and Russia have much more potential to use this type of energy.

In the United States, there are legal concerns about underwater land ownership and environmental  impact. Investors are not enthusiastic about tidal energy because there is not a strong guarantee that it will make money or benefit consumers. Engineers are working to improve the technology of tidal energy generators to increase the amount of energy they produce, to decrease their impact on the environment, and to find a way to earn a profit for energy companies.

Figure No 01 : Various design types for Tidal energy extraction 

Tidal Energy Generating Methods

There are currently three different ways to get tidal energy. They are tidal streams, barrages, and tidal lagoons. Brief introduction about above three methods can be mentioned as following manner

Tidal stream

For most tidal energy generators, turbines are placed in tidal streams. A tidal stream is a fast-flowing body of water created by tides. A turbine is a machine that takes energy from a flow of fluid. That fluid can be air (wind) or liquid (water). Because water is much more dense than air, tidal energy is more powerful than wind energy. Unlike wind, tides are predictable and stable. Where tidal generators are used, they produce a steady, reliable stream of electricity.

Placing turbines in tidal streams is complex, because the machines are large and disrupt the tide they are trying to harness. The environmental impact could be severe, depending on the size of the turbine and the site of the tidal stream. Turbines are most effective in shallow water. This produces more energy and allows ships to navigate around the turbines. A tidal generator's turbine blades also turn slowly, which helps marine life avoid getting caught in the system.

The world's first tidal power station was constructed in 2007 at Strangford Lough in Northern Ireland. The turbines are placed in a narrow strait between the Strangford Lough inletand the Irish Sea. The tide can move at 4 meters (13 feet) per second across the strait.

Figure No 02 : Tidal stream concept 

Barrage

Another type of tidal energy generator uses a large dam called a barrage. With a barrage, water can spill over the top or through turbines in the dam because the dam is low. Barrages can be constructed across tidal rivers, bays, and estuaries.

Turbines inside the barrage harness the power of tides the same way a river dam harnesses the power of a river. The barrage gates are open as the tide rises. At high tide, the barrage gates close, creating a pool, or tidal lagoon. The water is then released through the barrage's turbines, creating energy at a rate that can be controlled by engineers.

The environmental impact of a barrage system can be quite significant. The land in the tidal range is completely disrupted. The change in water level in the tidal lagoon might harm plant and animal life. The salinity inside the tidal lagoon lowers, which changes the organisms that are able to live there. As with dams across rivers, fish are blocked into or out of the tidal lagoon. Turbines move quickly in barrages, and marine animals can be caught in the blades. With their food source limited, birds might find different places to migrate.

A barrage is a much more expensive tidal energy generator than a single turbine. Although there are no fuel costs, barrages involve more construction and more machines. Unlike single turbines, barrages also require constant supervision to adjust power output.

The tidal power plant at the Rance River estuary in Brittany, France, uses a barrage. It was built in 1966 and is still functioning. The plant uses two sources of energy, tidal energy from the English Channel and river current energy from the Rance River. The barrage has led to an increased level of silt in the habitat. Native aquatic plants suffocate in silt, and a flatfish called plaice is now extinct in the area. Other organisms, such as cuttlefish, a relative of squids, now thrive in the Rance estuary. Cuttlefish prefer cloudy, silt ecosystems. 

Figure No 03 : Barrage 

Tidal Lagoon

The final type of tidal energy generator involves the construction of tidal lagoons. A tidal lagoon is a body of ocean water that is partly enclosed by a natural or manmade barrier. Tidal lagoons might also be estuaries and have freshwater emptying into them.  A tidal energy generator using tidal lagoons would function much like a barrage. Unlike barrages, however, tidal lagoons can be constructed along the natural coastline. A tidal lagoon power plant could also generate continuous power. The turbines work as the lagoon is filling and emptying.

The environmental impact of tidal lagoons is minimal. The lagoons can be constructed with natural materials like rock. They would appear as a low breakwater (sea wall) at low tide, and be submerged at high tide. Animals could swim around the structure, and smaller organisms could swim inside it. Large predators like sharks would not be able to penetrate the lagoon, so smaller fish would probably thrive. Birds would likely flock to the area.

But the energy output from generators using tidal lagoons is likely to be low. There are no functioning examples yet. China is constructing a tidal lagoon power plant at the Yalu River, near its border with North Korea. A private company is also planning a small tidal lagoon power plant in Swansea Bay, Wales.

Figure No 04 : Tidal lagoon 

Tidal energy potential Potential

Worldwide potential for wave and tidal power is enormous. So this will be a next energy supplying resource for the world.

Figure No 05 : Tidal energy potential in the World 

Environmental Impacts

Unlike fossil-fueled power plants, wave and tidal energy facilities generate electricity without producing any pollutant emissions or greenhouse gases. Since the sea wave and tidal energy facilities are currently being deployed, the full environmental impacts of wave and tidal power remain uncertain but are projected to be small. Concerns include impacts on marine ecosystems and fisheries. Environmental impact studies are currently underway and several pilot and commercial projects are undergoing environmental monitoring. The East River tidal turbine pilot project includes a $1.5 million sonar system to monitor impacts on fish populations. Careful siting should minimize impacts on marine ecosystems, fishing and other coastal economic activities. Wave and tidal facilities also have little or no visual impact, as they are either submerged or do not rise very far above the waterline.

Advantages of Tidal Energy

• It is an inexhaustible source of energy.
• Tidal energy is environment friendly energy and doesn't produce greenhouse gases.
• As 71% of Earth’s surface is covered by water, there is scope to generate this energy on large scale.
• We can predict the rise and fall of tides as they follow cyclic fashion.
• Efficiency of tidal power is far greater as compared to coal, solar or wind energy. Its efficiency is around 80%.
• Although cost of construction of tidal power is high but maintenance costs are relatively low.
• Tidal Energy doesn’t require any kind of fuel to run.
• The life of tidal energy power plant is very long.
• The energy density of tidal energy is relatively higher than other renewable energy sources.
• Tides are totally predictable, enabling us to calculate when we can generate more, and at times when the generation is low, shift the load to some other source of electricity generation.
• Offshore turbines and vertical-axis turbines are not extremely expensive to build and do not have a large environmental impact. 

Disadvantages of Tidal Energy

• Cost of construction of tidal power plant is high.
• There are very few ideal locations for construction of plant and they too are localized to coastal regions only.
• Intensity of sea waves is unpredictable and there can be damage to power generation units.
• Influences aquatic life adversely and can disrupt migration of fish.
• The actual generation is for a short period of time. The tides only happen twice a day so electricity can be produced only for that time.
• Frozen sea, low or weak tides, straight shorelines, low tidal rise or fall are some of the obstructions.
• This technology is still not cost effective and more technological advancements are required to make it commercially viable.
• Usually the places where tidal energy is produced are far away from the places where it is consumed. This transmission is expensive and difficult. 
• Many birds rely on the tide uncovering the mud flats so that they can feed. Fish can’t migrate, unless “fish ladders” are installed
• There are only a few suitable sites for tidal barrages 

Tidal Energy is thus a clean source of energy and does no t require much land or other resources as in harnessing energy from other sources. However, the energy generated is not much as high and low tides occur only twice a day and continuous energy production is not possible.

Programmable Logic Controller (PLC)

A Programmable Logic Controller (PLC) is a device that is used to program for performing control functions. Automotive industry was innovated the first PLC in the late 1960s to replace relay logic controls .It has been become most important introduction for automation industry. Because of that reason, lot of industrial processes have been made using automation technology.

Relay logic controls was used in past time but it had lot of difficulties when taking desired performances .Because of that reason PLC was introduce to minimize the difficulties .There are lot of advantages when using PLC ,those advantages can be listed as following 

• Easy programming and installation,
• High control speed
• Hardware and software security
• Network compatibility
• Troubleshooting and testing convenience
• High reliability
• Can be used in a harsh environment conditions
• There are not any moving parts
• Easy wiring system 

Industrial and commercial environments are being widely used PLC in present time. PLC can be found in almost any manufacturing facility. There are several manufacturers of PLCs. Each brands have unique programing method, but basically all PLC‘s hardware structures and programming concepts are very similar .There are lot of different PLC brands, famous brands can be mentioned as following.

• Allen Bradley PLC
• GE Fanuc PLC
• Horner electric PLC
• Siemens PLC
• Array PLC
• Xinje PLC

Figure No 01 : PLC brands 

When considering PLC, every PLC consist of following component

• Central processing unit (CPU)
• Memory
• Inputs Output modules
• Power supply
• Programming Terminal

Connection between above mentioned components can be demonstrated using following figure

       Figure No 02 : Connection among PLC components

Central processing unit

PLC has a central processing unit like other computerized devices. It is the brain of the PLC It is controlled by operating system software The operating system program is a supervisory programs that are loaded and stored permanently in the PLC’s memory by PLC programmer .CPU does following operations

• Updating inputs outputs ,using inputs status it energizes or de-energizes it’s output
• Performing logic and arithmetic operations
• Communicating with memory ,Programmed data are stored in memory  .So CPU can read or change the content of memory locations
• Scanning application program
• Communicating with a programming terminal

Figure No 03 : Central processing unit 

Memory

Memory is the most important component that stores information, programs, and data in a PLC. There are two process that are being done using memory .The process of putting new information into a memory location is called writing. The process of retrieving information from a memory location is called reading.

There two common types of memory used in PLC, they are Read Only Memory (ROM) and Random Access Memory (RAM). A ROM location can be read, but it cannot be written. ROM is used to store programs and data that should not be altered. Because of that reason the PLC’s operating programs are stored in ROM.

A RAM location can be read or written. Therefore the information stored in a RAM location can changed. Ladder logic programs are stored in RAM, programing langue may be different with the PLC brands. When a new ladder logic program is loaded into a PLC’s memory, the old program that was stored in the same locations is over-written and essentially erased. The memory capacities of PLCs can vary. Memory capacities are often expressed in terms of kilo-bytes (K). One byte is a group of 8 bits. One bit is a memory location that may store one binary number that has the value of either 1 or 0. (Binary numbers are addressed in Module 2). 1K memory means that there are 1024 bytes of RAM. 16K memory means there are 16384 bytes of RAM.  

Input modules and output modules

A PLC is a control device. It takes information from inputs and makes decisions to energize or de-energize outputs. The decisions are made based on the statuses of inputs and outputs and the ladder logic program that is being executed. The input signal can be given to the PLC by using push buttons, limit switches, relay contacts, photo sensors, proximity switches, temperature sensors, and the like. These input devices can be AC (alternating current) or DC (direct current). The input voltages can be high or low. The input signals can be digital or analog. Differing inputs require different input modules. An input module provides an interface between input devices and a PLC’s CPU, which uses only a low DC voltage. The input module’s function is to convert the input signals to DC voltages that are acceptable to the CPU. Standard discrete input modules include 24 V AC, 48 V AC, 120 V AC, 220 V AC, 24 V DC, 48 V DC, 120 V DC, 220 V DC, and transistor-transistor logic (TTL) level.

The devices controlled by a PLC include relays, alarms, solenoids, fans, lights, and motor starters. These devices may require different levels of AC or DC voltages. Since the signals processed in a PLC are low DC voltages, it is the function of the output module to convert PLC control signals to the voltages required by the controlled circuits or devices. Standard discrete output modules include 24 V AC, 48 V AC, 120 V AC, 220 V AC, 24 V DC, 48 V DC, 120 V DC, 220 V DC, and TTL level.    

         Figure No 04 : Input modules and output modules

 Power supply

Standard commercial AC power lines are being used to power the PLC. But many PLC components are utilizing 5V or another low voltage of DC power. Those components are CPU and memory. The PLC power supply converts AC power into DC power to support those components of the PLC.

Programming Terminal

A PLC requires a programming terminal and programming software for operation. The programming terminal is used for programming the PLC and monitoring the PLC’s operation. It may also download a ladder logic program (the sending of a program from the programming terminal to the PLC) or upload a ladder logic program (the sending of a program from the PLC to the programming terminal). 

Programming device

Generally personal computers are used to program the PLC. Working software allows users to modify, store, troubleshoot the program. Personal computers communicate with PLC using processor via a serial or parallel data communications link

Hand-held unit are often used for modifying, troubleshooting or transferring programs to multiple machines on the factory floor.

Conveyors

A conveyor is very important piece of mechanical system that moves material between locations. Conveyors are especially useful in applications involving the transportation of heavy or bulky materials. Conveyor systems allow quick and efficient transportation for a wide variety of materials, which make them very popular in the material handling and packaging industries. So it is very important thing to understand about conveyors designing and operating process. Conveyors are generally powered by electric motors, hydraulic motors, or by gravity. When selecting a conveyor the following factors must be carefully defined 

• Type of material transported. Is it bulk material, or unit goods.
• Physical characteristic of transported goods.
• Flow rate, tons per hour or number of units per hour.
• Load carrying capacity of structure.
• Distance traveled (Conveyor length).
• Direction of travel.(head to tail or tail to head)
• Conveyor height from floor.
• Level change. (Horizontal, Upward or downward path ).
• Support type (Floor stand, ceiling suspended, wall mounted, etc).
• Environment and operating conditions (Food grade, moisture, water splash etc.).

Detailed description about widely used conveyor types can be mentioned as following

Gravity roller conveyor

A gravity conveyor moves the load without utilizing motor power sources, usually down an incline or through a person pushing the load along a flat conveyor. Gravity conveyors transport products or work in process from one work area to another. Low cost, low maintenance are the advantages of this type of conveyors.

Power roller conveyor

Power roller conveyor is same as gravity roller conveyor, main difference is there is a motor or other equipment to power the system. Without a powered conveyor, materials handling can be difficult, time consuming and costly. Power roller conveyors can have significant advantages, depending on the type of materials that need to be transported.

Roller Bed Conveyor

Roller Bed Belt Conveyors are utilized for the transportation of hard to convey items such as small parts or items with inconsistent shapes or sizes Roller bed conveyors have a much higher load weight capacity than slider bed conveyors by reducing the friction caused by the belt against the bed surface.

Bucket Conveyor

This type of conveyors are very important , because they are designed to gently transport a wide variety of products, both horizontally and vertically, without transfer points. Capable of handling most dry, granular, free flowing products, these machines also work well with many non-free flowing products.

Screw conveyor

A screw conveyor or auger conveyor is a mechanism that uses a rotating helical screw blade, called a "flighting", usually within a tube, to move liquid or granular materials. They are used in many bulk handling industries. Screw conveyors in modern industry are often used horizontally or at a slight incline as an efficient way to move semi-solid materials, including food waste, wood chips, aggregates, cereal grains, animal feed, boiler ash, meat and bone meal, municipal solid waste, and many others. The first type of screw conveyor was the Archimedes' screw, used since ancient times to pump irrigation water.

Pneumatic Conveyor

pneumatic conveying systems move bulk materials that are suspended in an air stream that is introduced by a positive pressure blower upstream of material intake points, or by a vacuum pump that removes air from the system downstream of material discharge points. Material is separated from the conveying air at the use point, then discharged on a batch basis via butterfly or slide gate valves, or continuously via rotary airlock valves.

Flexible conveyor

The flexible conveyor is based on a conveyor beam in aluminum or stainless steel, with low friction slide rails guiding a plastic multi-flexing chain. Products to be conveyed travel directly on the conveyor, or on pallets/carriers. These conveyors can be worked around obstacles and keep production lines flowing. They are made at varying levels and can work in multiple environments. They are used in food packaging, case packing, and pharmaceutical industries but also in retail stores such as Wal-Mart and Kmart.

Vibrating conveyor

A Vibrating Conveyor is a machine with a solid conveying surface which is turned up on the side to form a trough. They are used extensively in food grade applications where sanitation, wash-down, and low maintenance are essential. Vibrating conveyors are also suitable for harsh, very hot, dirty, or corrosive environments. They can be used to convey newly cast metal parts which may reach upwards of 1,500 °F (820 °C). Due to the fixed nature of the conveying pans vibrating conveyors can also perform tasks such as sorting, screening, classifying and orienting parts. Vibrating conveyors have been built to convey material at angles exceeding 45° from horizontal using special pan shapes. Flat pans will convey most materials at a 5° Incline from horizontal line.

Figure No 01 : Conveyor types 

Conveyor systems are being used widespread across a range of industries due to the numerous benefits they provide. Some of the benefits can be mentioned as following

• Conveyors are able to safely transport materials from one level to another, which when done by human labor would be strenuous and expensive.
• They can be installed almost anywhere, and are much safer than using a forklift or other machine to move materials.
• They can move loads of all shapes, sizes and weights. Also, many have advanced safety features that help prevent accidents.
• There are a variety of options available for running conveying systems, including the hydraulic, mechanical and fully automated systems, which are equipped to fit individual needs.

Conveyor systems are commonly used in many industries, including the automotive, agricultural, computer, electronic, food processing ,aerospace, pharmaceutical, chemical, bottling and canning, print finishing and packaging. Although a wide variety of materials can be conveyed, some of the most common include food items such as beans and nuts, bottles and cans, automotive components, scrap metal, pills and powders, wood and furniture and grain and animal feed. Many factors are important in the accurate selection of a conveyor system. It is important to know how the conveyor system will be used beforehand. Some individual areas that are helpful to consider are the required conveyor operations, such as transportation, accumulation and sorting, the material sizes, weights and shapes and where the loading and pickup points need to be.

When considering above mentioned all the facts, it can be mentioned that conveyors are very important piece of mechanical equipment which makes lot of benefits for production floor.

Diesel Engine Exhaust Gas Properties

Engine exhaust gas properties are very important matter to be considered. Because it becomes one of the main reason for environmental pollution, green house effect, air pollution etc. Both petrol and diesel engine have two methods to measure their exhaust gas properties. Opacity of the exhaust gas is checked in diesel engines

Opacity is the measure of impenetrability to electromagnetic or other kinds of radiation, especially visible light. In radioactive transfer, it describes the absorption and scattering of radiation in a medium, such as a plasma, dielectric, shielding material, glass, etc. An opaque object is neither transparent (allowing all light to pass through) nor translucent (allowing some light to pass through). When light strikes an interface between two substances, in general some may be reflected, some absorbed, some scattered, and the rest transmitted (also see refraction). Reflection can be diffuse, for example light reflecting off a white wall, or specular, for example light reflecting off a mirror. An opaque substance transmits no light, and therefore reflects, scatters, or absorbs all of it. Both mirrors and carbon black are opaque. Opacity depends on the frequency of the light being considered. For instance, some kinds of glass, while transparent in the visual range, are largely opaque to ultraviolet light. More extreme frequency-dependence is visible in the absorption lines of cold gases. Smoke and smoke opacity meters are instruments measuring the optical properties of diesel exhaust. These instruments have been designed to quantify the visible black smoke.

Emission utilizing such physical phenomena as the extinction of a light beam by scattering and absorption. In general, smoke and opacity meters are much simpler (some of them very simple) and less costly in comparison to most other instruments used for PM measurement. They are often used to evaluate smoke emissions in locations outside the laboratory, such as in maintenance shops or in the field. In fact, the smoke opacity measurement is the only relatively low-cost and widely available method to measure a PM-related emission parameter in the field. For this reason, opacity limits are used in most inspection and maintenance (I&M) or periodic technical inspection (PTI) programs for diesel engines. Smoke opacity limits may be also included as auxiliary limits in new engine emission standards.

Diesel soot is by nature oily thus quickly clogging the filters and sample piping of a "normal" petrol exhaust gas analyzer. Those maintenance items are fairly expensive to be changed after every single test. That's why the smoke metering method for diesel engines has been implemented by all governments. A modern Smoke meter is a almost no-maintenance device.

Absorption factor (K factor ) is a more important factor to be considered when considering the opacity of an engine. This factor is also known as “Light Extinction Coefficient” and “Light Absorption Coefficient. K factor  is expressed on a per meter basis . The smoke density is a function of the number of smoke particles per unit gas volume, the size distribution of the smoke particles, and the light absorption and scattering properties of the particles. In the absence of blue or white smoke, the size distribution and the light absorption, scattering properties are similar for all diesel exhaust gas samples and the smoke density is primarily a function of the smoke particle density. Large K factor values indicate that air pollution is high, so there are standards for each type of vehicle  to minimize the environmental effect.

                                           

    Figure no 01 : How to use the instruments 

Figure no 02 : How to calculate the Opacity of the engine