UNITTTTTTTTTTTTTTTTTTTTTTTTTTTTTTT_1.pptx

RER

1. Renewable E nergy R esources Unit 1

2. UNIT- 1: INTRODUCTION & SOLAR CELLS Introduction Various non- conventional energy resources Solar Cell Theory of solar cells Solar cell materials Solar cell array Solar cell power plant, limitations

3. What is Renewable Energy? Renewable energy uses energy sources that are continually replenished by nature— the sun, the wind, water, the Earth’s heat , and plants. Renewable energy technologies turn these fuels into usable forms of energy— most often electricity, but also heat, chemicals, or mechanical power. Why Use Renewable Energy? Today we primarily use fossil fuels to heat and power our homes and fuel our cars. It’s convenient to use coal, oil, and natural gas for meeting our energy needs, but we have a limited supply of these fuels on the Earth. We’re using them much more rapidly than they are being created. Eventually, they will run out. The nation’s energy needs are expected to grow by 33 percent during the next 20 years. Renewable energy can help fill the gap. Even if we had an unlimited supply of fossil fuels, using renewable energy is better for the environment. We often call renewable energy technologies “clean” or “green” because they produce few if any pollutants. Burning fossil fuels, however, sends greenhouse gases into the atmosphere, trapping the sun’s heat and contributing to global warming. Climate scientists generally agree that the Earth’s average temperature has risen in the past century. If this trend continues, sea levels will rise, and scientists predict that floods, heat waves, droughts, and other extreme weather conditions could occur more often.

4. Renewable Resources Non- renewable Resources Depletion Renewable resources cannot be depleted over time. Non-renewable resources deplete over time. Sources Renewable resources include sunlight, water, wind and also geothermal sources such as hot springs and fumaroles. Non-renewable resources includes fossil fuels such as coal and petroleum. Environmental Impact Most renewable resources have low carbon emissions and low carbon footprint. Non-renewable energy has a comparatively higher carbon footprint and carbon emissions. Cost The upfront cost of renewable energy is high. For instance, generating electricity using technologies running on renewable energy is costlier than generating it with fossil fuels. Non-renewable energy has a comparatively lower upfront cost. Infrastructure Requirements Infrastructure for harvesting renewable energy is prohibitively expensive and not easily accessible in most countries. Cost-effective and accessible infrastructure is available for non-renewable energy across most countries. Area Requirements Requires a large land/ offshore area, especially for wind farms and solar farms. Comparatively lower area requirements.

5. Conventional Sources of Energy Non- conventional sources of energy These sources of energy are also known as a non-renewable source of energy These sources of energy are also known as a renewable source of energy They find both commercial and industrial purposes They are mainly used for household purposes These can be considered to be one of the reasons for the cause of pollution These are not responsible for the cause of pollution Coal, fossil fuels are two examples Wind, solar energy and Biomass are examples Difference between conventional and non-conventional energy sources

6. Basis Commercial Energy Non- Commercial Energy Meaning The sources of energy which command a price and their users have to pay a price for them, are known as Commercial Energy. The sources of energy which in general do not command a price, are known as Non- commercial Energy. Utilisation The sources of energy that individuals utilize for commercial purposes. The sources of energy that individuals utilise for domestic usage. Indicator of The utilisation of commercial energy sources can be an excellent indicator of how well the economy of a country is doing. The country’s living standards can be determined by the usage of non- commercial energy sources. Market Commercial energy is traded in the market(domestic and international); i.e., a price is demanded for these goods. Villagers often use non- commercial energy as free goods. At best, these goods have a local market. However, currently some of the non- commercial sources such as dried dung and firewood are charged a price in urban areas and are priced to some extent in rural areas as well. Nature It is generally an exhaustible source of energy (except hydropower). It is generally a renewable source of energy. Example The main sources of commercial energy are coal, oil, natural gas, and hydroelectricity. The main non- commercial energy sources include firewood, charcoal, cow dung, and agricultural waste. Difference between commercial and non- commercial energy sources

7. Present Status of Non-Conventional Energy Sources: Solar Energy: A potential for 30MW/km2 in India. Solar Photovoltaic (SPV) contributes 2.5% of power generation from renewable energy. It aggregates capacity of 47 MW have deployed for various applications. Maximum efficiency possible below 30%. But Carbon Nano Tube (CNT) based PV cell hold promise of higher efficiency up to 35%. Generation cost is still 4 times higher than a thermal power plant. Gujarat has been a leader in solar power generation and contributes 2/3rd of the 900 MW of photo-voltaic in the country. Wind energy scenario: India ranks fifth amongst the wind-energy-producing countries of the world after USA, China, Germany and Spain and produces 12009 MW as on 30 June 2011. Gross wind energy potential: 65,000 MW and technical potential: 45,000 MW. States with high potential: Tamil Nadu, Gujarat, Andhra Pradesh, Karnataka, Kerala, Maharashtra. Capital cost of wind power projects ranges from Rs. 5-6 corer/MW and the cost of generation is estimated to be Rs. 2.5 - 3/kwh. These fuels are in preliminary stages of development, and will take several years to develop. But no surplus oil seeds available for bio-fuels. In this case, Jatropha seems to available alternative. India has 60 million acres waste-land, and 30 million of that is suitable for Jatropha plantation. Geothermal Energy: Geothermal energy supplies more than 10,715 MW to 24 countries worldwide which is expected to generate 67,246 GWH of electricity in 2010. It is reliable source of energy which is available continuously throughout the year and independent of weather condition. India has reasonably good potential for geothermal; the potential geothermal provinces can produce 10,600 MW of power. At present there are no operational geothermal plants in India. There is also no installed geothermal electricity generating capacity as of now and only direct uses (e.g. Drying) have been detailed. India’s Gujarat state is drafting a policy to promote geothermal energy. III. Bio- fuels:

8. Solar cell A solar cell (also known as a photovoltaic cell or PV cell) is defined as an electrical device that converts light energy into electrical energy through the photovoltaic effect. A solar cell is basically a p- n junction diode. Solar cells are a form of photoelectric cell, defined as a device whose electrical characteristics – such as current, voltage, or resistance – vary when exposed to light. Individual solar cells can be combined to form modules commonly known as solar panels. The common single junction silicon solar cell can produce a maximum open- circuit voltage of approximately 0.5 to 0.6 volts. By itself this isn’t much – but remember these solar cells are tiny. When combined into a large solar panel, considerable amounts of renewable energy can be generated.

9. Construction of Solar Cell A solar cell is basically a junction diode, although its construction it is little bit different from conventional p- n junction diodes. Silicon solar cell consists of a thin slice of crystal p- type semiconductor into which a very thin layer of n-type material is diffused.

10. Working Principle of Solar Cell When light reaches the p- n junction, the light photons can easily enter in the junction, through very thin p- type layer. The light energy, in the form of photons, supplies sufficient energy to the junction to create a number of electron-hole pairs. The incident light breaks the thermal equilibrium condition of the junction. The free electrons in the depletion region can quickly come to the n- type side of the junction. Similarly, the holes in the depletion can quickly come to the p- type side of the junction. Once, the newly created free electrons come to the n- type side, cannot further cross the junction because of barrier potential of the junction. Similarly, the newly created holes once come to the p- type side cannot further cross the junction became of same barrier potential of the junction. As the concentration of electrons becomes higher in one side, i.e. n- type side of the junction and concentration of holes becomes more in another side, i.e. the p- type side of the junction, the p- n junction will behave like a small battery cell. A voltage is set up which is known as photo voltage. If we connect a small load across the junction, there will be a tiny current flowing through it.

11. V- I characteristics of Solar cell: Isc is the short circuit current and it is measured by short circuiting the terminals. Voc is the open circuit voltage and it is measured when no load is connected. Pm is maximum power, Im is maximum current, Vm is maximum voltage and it occurs at the bend of the characteristic curve.

12. V- I characteristics

13. Solar cells fundamentals

14. Solar cells fundamentals

15. Materials Used in Solar Cell The materials which are used for this purpose must have band gap close to 1.5ev. Commonly used materials are- Silicon. GaAs. CdTe. CuInSe 2 Criteria for Materials to be Used in Solar Cell Must have band gap from 1ev to 1.8ev. It must have high optical absorption. It must have high electrical conductivity. The raw material must be available in abundance and the cost of the material must be low.

16. Advantages, disadvantages and applications Advantages of Solar cell: It uses renewable energy No pollution so it is environment friendly It lasts for many years No maintenance cost Disadvantages of Solar cell: Energy is not produced during rainy, cloudy days and during night times. Cost of installation is high. Applications of Solar cell: It is used in calculators and in wrist watches Used in storage batteries Street lights Portable power supplies Satellites

17. Types of solar cells

18. Types of solar cells A monocrystalline solar cell is fabricated using single crystals of silicon by a procedure named as Czochralski progress. Its efficiency of the monocrystalline lies between 15% and 20%. It is cylindrical in shape made up of silicon ingots. PolyCrystalline or MultiCrystalline solar panels are solar panels that consist of several crystals of silicon in a single PV cell. Several fragments of silicon are melted together to form the wafers of polycrystalline solar panels. Amorphous silicon solar cells are the most well- developed thin- film solar cell. The structure usually has the p-i- n (or n-i- p) type of duality, where p- layer and n- layer are mainly used for establishing an internal electric field (i- layer) comprising amorphous silicon.

19. S olar M odule

20. Solar C ell A rray

21. Photovoltaic Power Generation: The maximum possible output of a solar array is about 300 W/m2. Figure shown in next page shows the basic structure of a solar cell power plant. This scheme is suitable for feeding a local load as also for feeding a grid. The photo voltaic array produces dc power and this must be converted into ac power for local use and feeding into the grid. Some form of energy storage is invariably used so that at time of excess generation, the energy may be stored so that it can be used at the time of low generation Solar Cell Power Plant: Depending on the method of utilization there can be two configurations: Stand alone system Grid connected system Stand Alone System: This system having following characteristics: Operates autonomously and independently. Commonly used for backup power where connecting to grids are very costly. Can be used to power DC loads and by the use of an inverter it may used for AC loads also. Hybrid stand alone systems may include other power producing devices also for backup. Standalone systems may be of any one of the categories: Direct Coupled Stand alone system. Stand alone system with Battery storage. Stand alone system with battery and charge control. Stand alone system with AC and DC loads. Hybrid Stand alone systems.

22. Direct Coupled Stand Alone System: In this the solar array is directly connected to the DC load. There is no energy storage. It can be used only in sunshine hours. Basically uses for water supply pumps for agricultural purpose. Stand Alone System with Battery Storage: In this the PV array charges the battery and the battery supplies DC power to the loads. There is no charge control and is susceptible to overcharge and over discharge. Stand Alone System with Batteries and Charge Control: This has got charge control for controlling the charge / discharge. Stand Alone Systems with AC and DC Loads: This system can be used to power AC as well as DC loads It needs inverter in the circuit. In addition, the main AC supply also may be used for charging only in the case of emergency. Downloaded by AKASH KATHAIT ([email protected])

23. Hybrid Standalone Systems: In such systems one or more sources in addition to the PV panels are used. Sources like stand by engines, turbines, fuel cells etc. may be used in conjunction with PV arrays which reduces the dependency on any single source. This also reduces battery storage capacity and size of PV arrays. Grid Connected Systems: In this system the power generated by the PV array is fed to the grid or to the AC load directly. At the time of excess power generation, the requirement of the loads is supplied to a commercial grid. The output from the inverter has to satisfy the norms of the quality of the electrical standard so that it can match the grid system.