Sun Energy Converted To Electricity Energy Source Engineering Essay

The sun's energy can be converted to electricity to give us a constant source of energy that can be tapped into without fear of power cuts, excessively high electricity bills and to ensure a clean and pollution free environment. This can be done with the help of photovoltaic cells in solar power plants set up especially for this purpose. The solar power plants have solar panels that are made up of numerous solar cells. A solar cell is a small disk made of a semiconductor type of material like silicon chips. They are attached to a circuit by electrical wires. As the sunlight hits the semiconductor, sun's energy in the form of light gets converted into electricity that forms a circuit and flows through the wires. The solar cells can only produce power in the presence of strong sunlight. When there is no light the solar cells stop producing electricity.

Solar batteries are fast becoming popular as a mode of conventional car fuel to help in the conservation of our environment and reduce carbon footprint. It minimizes the chances of being caught on the way with a dead battery and high bills for gasoline and other fuel. Green solar cars are being made popular by famous business house like Toyota, Panasonic, Venturi and others to promote awareness and create a favorable brand image. Federal and state governments also encourage the use of solar hybrid, eco friendly cars by initiating tax benefits.

The theory of solar energy conversion is a modern science that came into existence in 1970s. In order to cater to our ever growing energy needs, various studies have been undertaken in recent times to explore means of developing efficient solar energy conversing techniques. The amount of energy that comes on earth from the Sun is of astonishing quantum-in one second the Sun provides around 1017 joules of energy to Earth also it is equally surprising to know that the Sun provides as much energy to the Earth in one hour that humans need annually. The rate at which the Earth receives solar energy from Sun is 1.2 × 105 terawatts whereas the production rate of energy on earth by man-made techniques is merely 13TW. The quantum of solar energy though received by Earth is unprecedented but the same is not effectively used to cater the energy needs of the civilization. The non-renewable sources of energy like fossil fuels are still used as a major source to satisfy the energy requirements worldwide. Through the process of combustion fossil fuels are turned into useful energy but they tend to produce various greenhouse gases and other pollutants causing certain hazards to the environment. Various facts about solar energy cited below makes it more appealing than any other energy source:

wide availability

versatility

benign effect on the environment and climate

The untapped potential of the solar energy could be harnessed by conversion of solar energy into electricity. Today various studies on energy conversion based on nanomaterials focus on such conversion.

Listed below are the three methods used for the conversion of solar energy into electricity:

1. Solar Energy Cell

2. Solar Energy Collectors

3. Solar Energy Concentrators

The Solar Cells generally known as photovoltaic cells are used to convert sunlight into electricity directly, and the phenomenon is known as the photovoltaic effect. Photovoltaic batteries are made up of thin layers of semi-conducting material placed one above the other. Silicon is the most commonly used semi-conducting material used in photovoltaic cells. Now days, Solar panels have proved their utility in both the residential solar power generation as well as for utility scale power plants. When the surface of the cells faces the sun, the electrons absorb the solar energy in two different semiconductors which in turn creates the electric current.

Modules is a term used to refer to an array of photovoltaic cells that are grouped together for the purpose of creating an energy flow and they are capable of holding around 40 cells. In the process of generating electricity for a building at least 10 such modules need to be mounted together, the number of modules needs to be increased for generating electricity for big constructions like power plant. The 80 MW Sarnia Photovoltaic Power Plant in Canada, is the world’s largest photovoltaic plant.

This process is used to heat the buildings in winters. First of all solar panels are installed on the roof of the building. These panels along with heating up the building also heats up the water pipes being carried in it throughout thereby keeping the water heated up inside the building. The solar energy is therefore directly used to warm the water.

The two main components of a solar water heating system are: solar collector and a storage tank. Storage collector is a flat plated thin rectangular box facing the sun installed on the roof of the building. The solar energy heats up the absorber plate and in turn that heats up the water flowing through tubes inside the collector.

Solar power can also be converted into electricity indirectly through concentrated solar power (CPS).Under this method, mirror configurations are used to convert the solar energy into electricity. Various concentrating techniques are available which include the following:

Parabolic trough

Concentrating linear Fresnel reflector

Dish Stirling

Solar power tower

The parabolic trough technique is the most commonly used technique to collect the solar energy and use it to heat water. By using this technique the sunlight is focused onto a receiver pipe by using parabolic curved mirrors. The receiver pipe runs through the focal point of the curved surface. The working fluid in the pipes gets heated up and a conventional generator is used to produce electricity. The significance of this system lies in the fact that large area of sunlight is focused into a small beam by using lenses and mirrors. The troughs in the collector are aligned on a north-south axis to match the movement of the sun from east to west throughout the day.

The 354 MW SEGS Concentrated solar power plant is in California and is the largest power plant to harness solar energy in the world. Other CSP’s include the Solnova Solar Power Station (150 MW) and the Andasol Solar Power Station (100 MW); both these power stations are in Spain.

After the conversion of the solar energy into electricity it becomes imperative to have proper means to store it to have continuous supply of electricity even when the sunlight is not available. Broadly speaking the solar electricity could be stored either through integration with the grid of the utility company or providing solar batteries to bank the electricity.

This system of storage is used when electricity is being stored on a very large scale. The extra electricity generated in the peak hours get stored in the grid which can be withdrawn whenever required.

The need for storing the additional energy produced by the solar panels for later use necessitates the use of solar batteries. The solar battery stores the excess charge and helps to power a solar driven motor on days when direct sunlight may not be available or even during the night time. Commonly used types of batteries are the Lithium polymer, Lithium ion, Nickel-Cadmium, Nickel-Metal Hydride and the lead-acid batteries. The most efficient of these, however, are the Lithium polymer batteries. They store their electrolyte in an organic solvent state and are non-inflammable and safe to use.

When long power outages from the grid are predicted then battery bank is used to store the electricity produced from the solar energy. This mode of storage is as easy as hooking up the batteries to the transmission grid and the excess solar power can then be stored in the batteries. This is one of the most efficient ways to store power, because rechargeable batteries can store the excess electricity for a longer duration of time. When the solar-electricity is produced, it is sent to the batteries where it gets converted into chemical energy and is stored in a liquid form . At the time of retrieving the electricity from the battery, an electric charge is produced to trigger a chemical process to convert energy back in the form of electrons. Various types of batteries are available to store solar-electric energy and are used in different application areas:

Under Vanadium Redox Flow battery electrical energy is stored in two tanks of electrolytes or fluids that conduct electricity. Such batteries could be used as storage backup for a time span of 12 hours. These batteries could also be used in integrating solar power in a residential neighborhood or at several large industrial sites. At the time of energy requirement the liquid is pumped from one tank to another through a steady process after which the chemical energy from the electrolyte is transformed to electrical energy. During peak periods when there is maximum sunlight this process gets reversed and the excess energy gets stored in the battery. The size of the tank and its capacity to hold the electrolyte influences the quantum of energy that could be stored in the battery.

Under the sodium-beta alumina membrane battery sulfur and sodium are particularly used which serves the purpose of charging and discharging the electricity in/from the battery. The battery’s core is made up of aluminum oxide consisting of sodium ions. The battery is built in tubular design and has the capacity to store lots of energy in a small space. This battery is best suited for powering electric vehicles because of its high energy density, rapid rate of charge and discharge and short, potent bursts of energy.

However, as the battery operates at high temperatures it has been suggested to modify the shape of the battery in order to fix the safety issues and also to improve the efficiency.

Generally Lithium ion, or Li-ion batteries are used in household gadgets and electric vehicles. These batteries are made up of different elements like lithium, manganese and cobalt. These are best suited for transportation applications because of their high energy and power capacity potential .The battery works when positively charged lithium ions migrate through a liquid electrolyte, while electrons flow through an external circuit, both moving back and forth from one side to the other. This movement creates and stores energy.

The Lead-carbon batteries are usually used as back-up generators and in automobiles. Various studies have shown that the lifespan of the traditional lead-acid batteries can be improved by adding carbon in it. Also, such lead-carbon batteries have high concentrated power which makes them suitable for source for solar power. In a normal lead-acid battery, sulfuric acid reacts with the lead anode and cathode to create lead sulfate in the process of discharge. The process reverses during charge. With time the battery’s core gets filled up with lead sulfate due to crystallization. This process of crystallization can be prevented by adding carbon to the battery thereby enhancing the life of the battery.

The choice of using a particular battery from the above explained few depends upon the nature of application and the budget of the project.

A collection of connected 2-, 6-, or 12-volt batteries that supply power to the plant in case of outages or low production of electricity is known as a battery bank. In order to produce the current these batteries are wired together and a series is formed thereby producing 12-, 24-,or 48-volt strings. These strings are then connected together in parallel to make up the entire battery bank. The battery bank supplies DC power to an inverter, which produces AC power that can be used to run appliances. Factors like inverter’s input, type of battery selected amount of energy storage required determines the size of the battery bank.

At the time of installation of new battery, it is suggested to check its life cycle and the number of deep discharges it will be able to provide in future. Also the thickness of lead plates need to be checked upon as the life of battery depends upon the thickness of the plates.

The normal life of batteries is around 10-15 years irrespective of the amount of their usage as the acid in the battery wears down the internal components of the battery. In order to keep the battery working over its entire life following practices must be undertaken:

1. Deep discharging of batteries in repeated intervals must be avoided. The life of a battery is negatively correlated with the number of times it is discharged i.e. the more a battery is discharged, the shorter its lifetime. The other way out to fix this problem is by increasing the size of the battery bank .In order to support deep discharge of batteries every day , the size of battery bank must be increased.

2. Batteries must be stored at controlled temperatures. Rating for battery life is done only for temperatures between 70º-75º. If batteries are kept in temperatures warmer than this it reduces their life significantly. An effective way to heat a battery storage unit is by using passive solar power, but the battery storage unit must also be well insulated. Maintaining the temperature of the battery storage unit below 70º-75º will not extend their lives to any significant degree but will tend to reduce their capacity. Discharged batteries may freeze and burst, so maintain an adequate charge on the batteries in cold weather.

3. Maintain the same charge in all the batteries. Although the entire series of batteries may have an overall charge of 24 volts, some cells may have more or less voltage than neighboring batteries.

4. Inspection of batteries at regular intervals is also required to keep a track of leakage (buildup on the outside of the battery), appropriate fluid levels (for flooded batteries), and equal voltage.

The solar battery should have a constant voltage of approximately a hundred volts to be able to power the solar car engine. The battery pack comprises of several modules wired together. The higher voltage corresponds to better efficiency even though it requires a more complex array. The electronics controlling the power to the car include peak power trackers, the motor controller and data transmission system.

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Suitable For Harnessing Solar Energy Engineering Essay

 

There are several projects like photovoltaic cell in solar panels, solar power concentrator and parabolic dishes devised to harness solar energy in India. These plans prove very fruitful in south eastern parts of India in Tamil Nadu, Karnataka, northern plains in Uttar Pradesh, Bihar, western part of India in Rajasthan and parts of Gujarat. In short, those places which have annual average temperature of more than 25°C are suitable for utilizing this energy into usable power.

In this project we have tried to put up a new way of converting electrical energy directly into mechanical energy without any use of solar cell or mirrors. The idea is supposed to be simple as there is no involvement of dedicated machinery or setup and practically no running cost.

The basic idea lies in the structure and way of using solar energy. In this project, the aim is to convert solar energy into kinetic energy of wind and then use this wind for purposes like rotation of turbine or for any other mechanical work. The basic principle involved is that the heated air is lighter than the cold air. If air gets heated near the surface of earth, then it tries to move up into atmosphere and replace the position of cold air from surrounding. The heated air which moves up, acquires a kinetic energy while moving and can be used to rotate the blades of turbines, if stroked with pressure.

The structure consists of a metallic dish made up of aluminium in which the distance between two diametrically opposite points is 20 meters which has a hole in its centre and is placed on supports such that its outer boundary lies at a distance of 3 meters from ground level. Eight rods made of iron are used as a support, which are inserted in the ground. A frustum shaped pipe with a nozzle at the upper end and lower diameter of 1 meter is used to impart the hot air up to the blades of turbine and a iron pipe of lower diameter 1 meter and length of about 10-15 meters is used to hold this nozzle and turbine. The dish must be designed in such a way that its centre lies 1 meters high from its outer boundary, that is, it forms the shape of a big umbrella roof as shown in figure.

WORKING:

This structure helps us to direct all heated wind toward the centre of the dish and no air is escaped from the outer boundary of dish. The heated air when passed through the centre of dish, tries to move through the thin pipe which further has a nozzle at the end. So the escaping wind moves like a high speed stream in that pipe just like steam as it passes in the thermal power plant, strikes the blade of the turbine which is just in front of nozzle and transfers its momentum and ultimately the blade moves and the next blade comes in place of previous one. Due to the continuous flow of hot air, the turbine starts rotating and hence the connected shaft also starts delivering mechanical output. The cold air moves inside from the bottom of dish and take the place of hot air, gets heated and moves up and thus the cycle continues, and we get mechanical power in the form of rotating shaft of turbine which can be used either to generate electricity, which is our main requirement or in other forms as well, where we need mechanical power, like in pumps or other mechanical machines.

The main difference in this solar power set up and other plants utilizing the same energy is that here we get mechanical energy as the outcome and we can use it in numerous ways but in other projects, like in solar panels and rotating dish we get electrical energy only, this is quite an advantageous part of this project. The other advantage of this project is that we can use the hot air produced through this installation for various other plants and industrial applications like, in drying operation in chemical industries, heat exchangers and preheating of water in thermal power plants and at domestic level it can be used for room heating, driers and water heating which will greatly reduce the domestic power consumption as power consumption in water heating accounts for about 30% of electricity bill and thus this heated gas helps to minimize the electric consumption.

The problem lies in the efficiency of the turbine used, that is, nowadays the turbines manufactured are good for higher speed stream wind but in our model we need a better and lighter turbine which rotates with greater r.p.m with the given speed of wind. As the power output and mechanical work, both depend upon the r.p.m of the rotating shaft so it should be high and for increasing the r.p.m there must be an improvement in our present technology, in the sector of turbine design and material science for improving the quality of materials used for turbine design. The existing industry products require a minimum wind speed of 25 km/hr for production of 10 MW of power, thus we have to improve our technology to reduce this speed.

The other possible disadvantage of this project which is common for most of the solar plants is that, it will not work at night or in rainy seasons. As there will be lesser chances of availability of sun in those periods, hence less heated air production and consequently reduction in movement of air, so power production would get a pause for this period. The idea of storage of energy in rechargeable batteries might prove useful for those periods. There must be regular supervision and checking of the dish to prevent the development of holes and cracks in it, as it would greatly reduce the efficiency of the system by leaking the air. The overall performance would also be greatly affected.

COST, INVESTMENT AND RETURN:

Surface Area of Dish can be calculated as:

(X + 1)2 = 102 + X2

(X2 + 1 +2.X) = 100 + X2

2X = 99

X = 49.5 m

Hence, Radius = 50.5 m

Sin? = (10/50.5)

? = Sin-1(10/50.5)

? = 11.42o

Hence, the ends of the dish make an angle of (2 x 11.42) = 22.84o

Therefore, the Surface area of dish = (?/360) x 4p x (Radius)2

= (22.84/360) x 4 x (22/7) x (50.5)2

= 2034 m2

Since, Thickness of dish =3mm

Therefore, Volume of dish =2034 X.003=6.102 m3

Surface area of circular pipe = p X Diameter of pipe X Height of pipe

=3.14 X 1 X 10m

=31.4 m2

Thickness of Pipe = .005 m

Volume of material used in pipe= 31.4 X .005=0.157 m3

The cost analysis is done by discrete method, that is, by quantizing various costs as follows:

a) Cost of dish= (area of dish) X (thickness of plate) X (Density of metal) X cost of metal per kilogram = 2034m2 X .003 m X 2700kg/m3 X Rs130/kg = Rs 2142000

b) Cost of eight supports= 8 X 3 m X cost per meter of support= 24 X 3 m X Rs 150/m =Rs 10800

c) Cost of pipe= (curved surface area of pipe) X cost of sheet = 31.4 m2 X Rs 200/m2 = Rs 6280

d) Cost of nozzle and frustum = Rs 10000

e) Cost of turbine, blades and shaft= Rs 0.5 million

f) Labour charge= Rs 3 million

g) Maintenance cost and land rent= Rs 1 million

h) Miscellaneous charge= Rs 2-2.5 million rupees

TOTAL expected cost = Rs8.6 million

RETURN ANALYSIS:

In Indian scenario we have almost 300 clear sunny days and on an average 10 hours of bright sunlight available so we can calculate the power output in kilowatt hour as

300 X 10 X 60 X 60 X 10 MW/3.6 X 106

=3 x107 KWh of power

Expected sales rate = Rs 2 per unit

Total expected annual return = Rs 60 million

Expected annual profit: Rs 51 million

After analysing the cost and return, it is found that this project remains profitable over the year and gives a profitable return in the summer season.

EFFECT OF GOVERNMENT INCENTIVES:

The Government of India has a very positive and supportive approach towards the solar power. It provides manufacturers and users of commercial and near commercial technologies, with ‘soft’ loans on favourable terms through the IREDA (Indian Renewable Energy Development Agency). The RBI (Reserve Bank of India) terms the renewable energy industry as “Priority Sector”, and has permitted Indian Companies to accept investment under the ‘automatic route’ without obtaining prior approval from RBI.

The Govt of India also provides exemptions/concessions in the excise tax duty on the manufacture of the solar energy systems and devices such as flat plate solar collectors, solar water heater and systems and any specially designed devices which operate those systems. Their incentives include concession on custom duty, 10 year tax holidays and sales and electricity tax exemption and preferential tariffs. It also includes capital subsidies.

The financial assistance of the Central Government is one of the factors which are highly helpful in the solar power market. It provides up to Rs 50 lakhs per city for a period of 5 years, Rs 20 lakhs for awareness generation, capacity building and other promotional activities, Rs 10 lakhs for preparation of a master plan, setting up institutional arrangements, oversight of implementation during the period of 5 years respectively.

The State Electricity Regulatory Commission has been mandated to source up to 10% of their power from renewable energy sources.

The Government based incentives also provide INR 0.5/ KWh of power sold, for independent power producers with capacity >5MW, for the projects that don’t claim accelerated depreciation benefits.

The State Government has set a remunerative price under power purchase policy for the power generated through solar energy system, fed to the grid by private sector. It also has provisions and policy packages including banking, third party sale and buy-back of solar energy power. The State Government also encourages NGO’s and small entrepreneurs for their participation in solar power market.

In a nutshell, the Indian government provides its support to a larger extent for the development of a sustainable solar power market.

SOLAR POWER MARKET:

India has seen only modest pace of growth , relative to demand , in solar power generation. This has resulted in persistent supply shortages for both urban and rural customers. The main customers of solar power generation market include homeowners, businesses and utility companies.

The demand for electricity in developing countries is growing at a fast pace. The potential worldwide market for solar power over the next 20 years is estimated at 600 GW or 6000 plants of 100 MW solar capacities, most of this in developing countries like India.

Over the next 20 years, It is predicted that there will be actual installations of 45 GW or over twenty 100 MW solar capacity plants per year, assuming niche markets could allow for a 7.5% penetration rate. The actual penetration rate will depend on progress in reducing the cost/performance ratio, support from governments (and the GEF), and energy prices.

The above graph represents the daily utility load profiles for four developing countries: India, Jordan, Egypt and Mexico. The values for India are the average of three regions. After analyzing the above graph, one can forecast that the solar power has a great future in developing countries; hence this plan can be promising for India as it has its maximum consumption in day time so we can rely on this type of setups for our energy needs.

In 2008, the cumulative Solar power capacity was 15 GW. Growth in recent years has been 15% per year. There are estimated 40 million households (2.5% of the total) which were using solar power worldwide in 2004.

China is the leader; 10% of Chinese households use solar power; the target for 2020 being 30%.

In 2008, 65.6% of existing global solar power capacity was in China; followed by European Union (12.3%), Turkey (5.8%), Japan (4.1%) and Israel (2.8%). The Indian share was 1.2%.

The estimated break up of solar power installations in India (till 2009) is as follows:

Residential (80%)

2.108

Hotels (6%)

0.158

Hospitals (3%)

0.079

Industry (6%)

0.158

Other (Railway + Defence + Hostel + Religious places,

other) (5%)

0.132

2.635

The main factors contributing the demand rise in recent years are

• Growth in new urban housing; rising disposable income; increased propensity for consumer durables

• Arrival of ETC & improvements in supply chain

• Energy price hike

• Policy initiatives

According to a survey, five states will lead demand-expansion, as is evident from the following table:

Karnataka

3.72

0.16

3.88

Maharashtra

3.5

0.31

3.80

Tamil Nadu

1.53

0.14

1.67

Andhra Pradesh

1.08

0.09

1.17

Gujarat

0.9

0.06

0.96

%age of 5 states

67.1%

Analysis of demand at the district level shows that a large part of the demand would come from selected urbanized districts. Some of the key districts (out of the 29 surveyed districts) which have large potential for solar power generation market are Bangalore, Pune, NCR, Thane, Hydrabad, Nagpur, Kolkata, Chennai, Coimbatore, Ahmadabad and Jaipur. Among them, Bangalore has highest solar power potential of about 1.94 million m2, in 2022.

Solar power market development plan:

The solar power market development plan is divided into 3 phases:

1. Niche Market Awareness:

The main objectives are to rekindle interest in Solar power generation in India, allow the industry to start-up production processes, determine the current cost and performance of Solar power generation ,and evaluate new Solar power generation concepts to see if they have promise for long term commercialization.

The main activity is to increase market awareness by funding one or two Solar plants in

India. These plants will likely be smaller than the optimum of over 200 MW because of the need to minimize investor risk and to start-up production processes.

It is recommended that the initial market focus should be in those markets where the conditions for solar power generation are currently most promising. Previous experience shows that these conditions are High Solar Resource, High fossil fuel prices, Daytime Peaking Utility, Inefficient Conventional Power Plants, Access to Water and the Grid.

Depending on the cost of power displaced, the financial support to achieve cost parity will range from $400 to $750 million or $550 to $1000 per kW.

2. Market Expansion:

The purpose of the market expansion phase is to develop larger systems to benefit from economies of scale, continue with product development to improve performance and lower costs, create a market large enough that manufacturers can justify construction of production lines, and standardize system designs. A standard design will help to improve the system cost performance by reducing design costs, streamlining equipment procurement and minimizing construction and start-up problems.

In this phase, 3000 MW of additional solar capacity is installed, or fifteen 200 MW plants. The cost of solar power is expected to fall from over 10 cents/kWh to between 7 and 8 cents per kWh.

Depending on the cost of power displaced, the financial support to achieve cost parity will range from $0.5 to $1.8 billion or $350 to $600 per kW.

3. Market acceptance:

The final part in the development plan is the market acceptance phase. The goal for this phase is to set up the necessary market structure so that solar power generating plants can compete with conventional power plants without financial support from the GEF or others.

The investment requirement in this phase is the most difficult to estimate and subject to the

widest variation. The cost of solar generated electricity is expected to fall close to conventional power values. A small difference in solar costs can have a huge impact on the market penetration.

Solar power generation market has the ability to dramatically transform lives. In a country, where 450 million people live without access to electricity and have to depend on kerosene and other alternatives for whatever little lighting they can get at night, solar power as an application in small home lightening system lightens up their lives.

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