RENEWABLE ENERGY
Lecture Notes
K.P.Sudheer
P.K. Suresh kumar
Sreekutty Suresh V
Greeshma K
Department of Agricultural
Engineering College of Horticulture
Kerala Agricultural University
Vellanikkara, Thrissur – 680 656
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Renewable Energy Lecture Notes, Summaries of Environmental Science
Lecture notes on renewable energy, covering sources of energy, their classification, and advantages and disadvantages of different types of energy. The document also covers commercial and non-commercial energy, and renewable energy sources that are available in unlimited amounts in nature. The lecture notes are prepared by Prof. K.P. Sudheer, Prof. P.K. Sureshkumar, Er. Sreekutty Suresh V, and Er. Greeshma K from the Department of Agricultural Engineering at Kerala Agricultural University.
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Lecture Notes
K.P.Sudheer
P.K. Suresh kumar
Sreekutty Suresh V
Greeshma K
Department of Agricultural
Engineering College of Horticulture
Kerala Agricultural University
Vellanikkara, Thrissur – 680 656
Renewable Energy Lecture notes
Course No.
Course Title
: ENGG. 3204
: RENEWABLE ENERGY
Credits : (1 +0)
Prepared by Prof. K.P. Sudheer Prof. P.K. Sureshkumar Er. Sreekutty Suresh V Er. Greeshma K
Kerala Agricultural University
Department of Agricultural Engineering
College of Horticulture Vellanikkara,
Thrissur – 680656
CONTENT
Sl. No Content Page No 1 Sources of energy, Classification, energy from Biomass 1 2 Properties of different types of renewable energy sources 8 3 Types of biogas plants, constructional details, biogas production and it 10 utilization-problems 4 Agricultural wastes, principles of combustion, pyrolysis and 23 gasification 5 Types of gasifiers, producer gas and its utilization 28 6 Briquettes, types of Briquetting, uses of briquettes, shredders 35 7 Solar energy, solar flat plate and focussing plate collectors 40 8 Solar air heaters, solar space heating and cooling 47 9 Solar energy applications/solar energy gadgets, solar cookers, solar 50 water heating systems 10 Solar grain dryers, solar refrigeration system, solar ponds 57 11 Solar photovoltaic systems, solar lantern, solar street lights, solar 65 fencing 12 Solar pumping systems 72 13 Wind energy, types of wind mills 74 14 Construction details and application of wind mills 82 15 Liquid bio fuels, types 85 16 Bio diesel and ethanol from agricultural produce 88 17 Production of bio diesel 90 18 Applied use of different types of renewable energy sources from the 95 practical stand point
Lecture No. Sources of energy, classification
Introduction
Energy plays a very important role in our lives, providing comfort, increasing productivity and allowing us to live the way we want to. Since the beginning of mankind, we have made use of wood, water, and fossil fuels as a means of heating and making machines work. Almost for all types of activities, we rely on one or another form of energy.
Amount of energy used by a society is an indicator of its economic growth and development. Without energy even our body would be unable to perform basic functions like respiratory, circulatory, or digestive functions to name a few. Plants would also be unable to complete the process of converting Carbon dioxide, water and minerals into food without the light from the Sun. Almost all the machines used for the production and manufacture of different types of items would be unable to operate without the use of a source of electrical energy. Almost everything we see around us, the clothes we wear, the food we eat, the houses we live in, the paper we write on, the vehicles we drive, all need energy to be created or transformed from some natural resource to the final product. Nowadays, the electrical energy has become so important that almost in all walks of life electricity is required. For example all electrical appliances in our homes and at our workplace require electricity. All the industries and factories run on electricity.
1.1.Sources of Energy In simple terms we can say that anything out of which usable energy can be extracted is a source of energy. There is a variety of sources that provide us energy for different purposes. You must be familiar with coal, petrol, diesel kerosene and natural gas. Similarly you must have also heard about hydroelectric power, wind mills, solar panels, biomass etc.
of smaller atoms releasing huge amount of energy in the process. During this process, a few neutrons are also released. These neutrons split other nuclei of the Uranium (235). The reaction continues rapidly and is known as the chain reaction. In this process a large amount of energy is released. This energy is used for boiling water till it becomes steam. Steam so generated is used to drive a turbine which helps in generating electrical energy. Advantages Disadvantages Very concentrated form of energy Produces radioactive waste Power plants do not produce smog^ Radioactive elements arenonrenewable
1.1.3 Sun - The Ultimate Source of Energy Solar energy is energy derived from sun in the form of solar radiation. It is hardness by either direct sources (like solar cooker, solar steam systems, solar dryer, solar cells, etc.), or indirect sources (biomass production, wind, tidal, etc.). The output of the sun is 2.8 x 10^23 Kwy- (^1). The energy reaching the earth is 1.5x 10 (^8) Kwy-1. It is used for drying, cooking, heating, generating power etc. Advantages Disadvantages
^ ^ Almost limitless source of energy Does not produce air pollution
Expensive to use for large scale energy production Only practical in sunny areas It is intermittent in nature
1.1.4 Wind Energy Wind power is another alternative energy source that could be used without producing by-products that are harmful to nature. Like solar power, harnessing the wind is highly dependent on weather and location. However, it is one of the oldest and cleanest forms of energy and the most developed of the renewable energy sources. There is the potential for a large amount of energy to be produced from windmill.
Advantages Disadvantages
^ ^ Renewable ^ ^ Relatively inexpensive to generate Does not produce air pollution
Only practical in windy areas Produces less energy Wind mill is big, bulky and inconvenient to use as compared to other forms of energy
1.1.5 Biomass Energy Organic material made from plants and animals (microorganisms). Biomass has an existing capacity of over 7,000 MW. Biomass as a fuel consists of organic matter such as industrial waste, agricultural waste, wood, and bark. Biomass can also be used indirectly, since it produces methane gas as it decays or through a modern process called gasification. Methane can produce power by burning in a boiler to create steam to drive steam turbines or through internal combustion in gas turbines and reciprocating engines. Advantages Disadvantages Renewable It is dispersed and land intensive source Cleaner burning than oil Produces smoke Abundant It has low energy density
1.1.6 Geothermal Energy Geothermal energy is energy derived by tapping the heat of the earth itself like volcano, geysers, hot springs (etc.). These volcanic features are called geothermal hotspots. Basically a hotspot is an area of reduced thickness in the mantlewhich expects excess internal heat from the interior of the earth to the outer crust.The heat from these geothermal hotspots is altered in the form of steam which is usedto run a steam turbine that can generate electricity.
tides, mountain lakes, the rivers (from which hydroelectric energy can be obtained) and the Earth heat that supplies geothermal energy.
^ ^ Secondary resources: -^ They are derived from the transformation of primary energy sources: for example petrol that derives from the treatment of crude oil and electric energy obtained from the conversion of mechanical energy (hydroelectric plants, Aeolian plants), chemical plants (thermoelectric), or nuclear (nuclear plants). Electric energy is produced by electric plants, i.e. suitable installations that can transform primary energy (non- transformed) into electric energy. 1.2.2 Based on transaction i. Commercial Energy:- The energy sources that are available in the market for a definite price are known as commercial energy. By far the most important forms of commercial energy are electricity, coal and refined petroleum products. ii. Non Commercial Energy:- The energy sources that are not available in the commercial market for a price are classified as non-commercial energy. Non-commercial energy sources include fuels such as firewood, cattle dung and agricultural wastes, which are traditionally gathered, and not bought at a price and used especially in rural households. These are also called traditional fuels. Non-commercial energy is often ignored in energy accounting. 1.2.3 Based on energy storage or cycling time involved i. Renewable energy (inexhaustible) are mostly biomass based and are available in unlimited amount in nature. Since these can be renewed over a relatively short period of time, energy sources that are replenished more rapidly are termed as renewable. These include firewood or fuel wood from forest, petro plants, plant biomass ie. agricultural waste like animal dung, solar energy, wing energy, water energy in the form of hydro- electricity and tidal energy and geothermal energy etc. ii. Non-renewable energy (exhaustible) are available in limited amount and develop over a longer period of time. As a result of unlimited use, they are likely to be exhausted one day. These include coal, mineral, natural gas and nuclear power. Coal, petroleum and natural gases are common sources of energy being organic (biotic) in this origin. They are also called fossil fuels.
1.3.4 Based on traditional use i. Conventional energy sources:- The sources of energy which have been in use for a long time, e.g., coal, petroleum, natural gas and water power.They are exhaust able except water and cause pollution when used, as they emit smoke and ash. ii. Non-conventional energy sources:- The resources which are yet in the process of development over the past few years. It includes solar, wind, tidal, biogas, and biomass, geothermal.They are inexhaustible, pollution free, easy to maintain and less expensive due to local use.
These sources of energy are renewable and there is no danger of depletion. These recur in nature and are in-exhaustible. (^) The power plants based on renewable sources of energy don‟t have any fuel cost and hence negligible running cost. Renewable are more site specific and are used for local processing and application. There is no need for transmission and distribution of power. Renewables have low energy density and more or less there is no pollution or ecological balance problem. Most of the devices and plants used with the renewables are simple in design and construction which are made from local materials, local skills and by local people. The use of renewable energy can help to save foreign exchange and generate local employment. The rural areas and remote villages can be better served with locally available renewable sources of energy. There will be huge savings from transporting fuels or transmitting electricity from long distances. 2.4 Disadvantages of renewable energy
Low energy density of renewable sources of energy need large sizes of plant resulting in increased cost of delivered energy. Intermittency and lack of dependability are the main disadvantages of renewable energy sources. Low energy density also results in lower operating temperatures and hence low efficiencies. Although renewables are essentially free, there is definite cost effectiveness associated with its conversion and utilization. Much of the construction materials used for renewable energy devices are themselves very energy intensive. The low efficiency of these plants can result in large heat rejections and hence thermal
pollution. The renewable energy plants use larger land masses.
Lecture No.
Types of biogas plants, constructional details, biogas production and
utilization-problems
3.1 Biogas Most organic materials undergo a natural anaerobic digestion in the presence of moisture and absence of oxygen and produce biogas.The biogas so obtained is a mixture of methane (CH 4 ):
55-65% and Carbon dioxide (CO 2 ) : 30-40%. The biogas contains traces of H 2 , H 2 S and N 2. The
calorific value of biogas ranges from 5000 to 5500 Kcal/Kg (18.8 to 26.4 MJ /m^3 ). Digestion is biological process that occurs in the absence of oxygen and in the presence of anaerobic organisms at temperatures (35-70ºC) and atmospheric pressure. The container in which, this process takes place is known as digester.
3.2 Types of biogas plants Biogas plants basically are two types 3.2.1 Floating dome type o The floating-drum plant with a cylindrical digester (KVIC model) 3.2.2 Fixed dome type o The fixed-dome plant with a brick reinforced, moulded dome (Janata model) o The fixed-dome plant with a hemisphere digester (Deenbandhu model) 3.2.1 Floating dome type Floating-drum plants consist of an underground digester and a moving gas-holder. The gas- holder floats either directly on the fermentation slurry or in a water jacket of its own. The gas is collected in the gas drum, which rises or moves down, according to the amount of gas stored. The gas drum is prevented from tilting by a guiding frame. If the drum floats in a water jacket, it cannot get stuck, even in substrate with high solid content.
small-chain simple acids. In the second stage, these acids are acted upon by another kind of bacteria, called methane formers and produce methane and carbon dioxide.
Fig 3.2 KVIC model biogas plant
Gas holder :- The gas holder is a drum constructed of mild steel sheets. This is cylindrical in shape with concave. The top is supported radically with angular iron. The holder fits into the digester like a stopper. It sinks into the slurry due to its own weight and rests upon the ring constructed for this purpose. When gas is generated the holder rises and floats freely on the surface of slurry. A central guide pipe is provided to prevent the holder from tilting. The holder also acts as a seal for the gas. The gas pressure varies between 7 and 9 cm of water column. Under shallow water table conditions, the adopted diameter of digester is more and depth is reduced. The cost of drum is about 40% of total cost of plant. It requires periodical maintenance.
The unit cost of KVIC model with a capacity of 2 m^3 /day costs approximately Rs.14, 000.
3.2.1.2 Advantages and Disadvantages of floating dome plants
Advantages Disadvantages
^ ^ Simple, easily understood operation
^ ^ Volume of stored gas is directly visible The gas pressure is constant, determined by the weight of the gas holder The construction is relatively easy, construction mistakes do not lead to
High material costs of the steel drum Susceptibility of steel parts to corrosion floating drum plants have a shorter life span than fixed-dome plants Regular maintenance costs for the painting of the drum
major problems in operation and gas yield.
3.2.2 Fixed-dome type plants A fixed-dome plant consists of a digester with a fixed, non-movable gas holder, which sits on top of the digester. When gas production starts, the slurry is displaced into the compensation tank. Gas pressure increases with the volume of gas stored and the height difference between the slurry level in the digester and the slurry level in the compensation tank.
Fig 3.3 Fixed-dome type plants
1 Mixing tank with inlet pipe and sand trap. 6 Entry hatch, with gastight seal 2 Digester 7 Accumulation of thick sludge. 3 Compensation and removal tank 8 Outlet pipe 4 Gasholder 9 Reference level 5 Gaspipe 10 Supernatant scum, broken up by varying level
c) Gas Holder - The top part of a fixed-dome plant (the gas space) must be gas-tight. Concrete, masonry and cement rendering are not gas-tight. The gas space must therefore be painted with a gas-tight layer (e.g. 'Water-proofer', Latex or synthetic paints). A possibility to reduce the risk of cracking of the gas-holder consists in the construction of a weak-ring in the masonry of the digester. This "ring" is a flexible joint between the lower (water-proof) and the upper (gas-proof) part of the hemispherical structure. It prevents cracks that develop due to the hydrostatic pressure in the lower parts to move into the upper parts of the gas-holder.
3.2.2.1 Advantages and Disadvantages of fixed dome plants
Advantages Disadvantages Low initial costs and long useful life-
span No moving or rusting parts involved Basic design is compact, saves space and is well insulated Construction creates local employment. The underground construction saves space and protects the digester from temperature changes
Masonry gas-holders require special sealants and high technical skills for gas-tight construction Gas leaks occur quite frequently; fluctuating gas pressure complicates gas utilization Amount of gas produced is not immediately visible, plant operation not readily understandable Fixed dome plants need exact planning of levels; excavation can be difficult and expensive in bedrock.
3.2.3 Types of Fixed Dome Plants 3.2.3.1 Janata model The design of this plant is of Chinese origin but it has been introduced under the name “Janata biogas plant” by Gobar Gas Research Station, Ajitmal in view of its reduced cost. This is a plant where no steel is used, there is no moving part in it and maintenance cost is low. The plant can be constructed by village mason taking some pre-explained precautions and using all the indigenously available building materials. Good quality of bricks and cement should be used to avoid the afterward structural problems like cracking of the dome and leakage of gas.
Substrates other than cattle dung such as municipal waste and plant residues can also be used in janata type plants. The plant consists of an underground well sort of digester made of bricks and cement having a dome shaped roof which remains below the ground level is shown in Fig 3.5.At almost middle of the digester, there are two rectangular openings facing each other and coming up to a little above the ground level, act as an inlet and outlet of the plant. Dome shaped roof is fitted with a pipe at its top which is the gas outlet of the plant. The principle of gas production is same as that of KVIC model. The biogas is collected in the restricted space of the fixed dome, hence the pressure of gas is much higher, which is around 90 cm of water column.
Fig 3.5Janta model biogas plant
3.2.3.2 Deenbandhu Model Deenbandhu model biogas plant was developed by AFPRO (Action for Food Production, New Delhi) in 1984. The world Deenbandhu is meant as the friend of the poor. This plant is designed on the principle that the surface area of biogas plants is reduced (minimized) to reduce their installation cost without sacrificing the efficiency of the plant. The design consists of segments of two spheres of different diameters, joined at their bases. The structure thus formed act as the digester as fermentation chamber as well as the gas storage chamber. The higher compressive strength of the brick masonry and concrete makes it preferable to go in for a