Environmental Science Lecture Notes PDF November 2020

11/17/2020 Environmental Science (NE466) Dr. Mohamed A. Elsayad, PhD., Construction & Building Department, Faculty of Engineering, AAST University Lecture 5-------------------------------------------------------------------------...

11/17/2020 Environmental Science (NE466) Dr. Mohamed A. Elsayad, PhD., Construction & Building Department, Faculty of Engineering, AAST University Lecture 5-------------------------------------------------------------------------------------------------------------------------------------------------------- Ecological Stability Stability has often been defined as a lack of variation in some parameter of an ecological system. The term stability has also frequently been used in reference to the response of an ecosystem to a disturbance. A system is considered to be locally stable if it is able to return to an equilibrium point following small disturbances and globally stable if the system returns following any degree of disturbance (Lewontin, 1969). Ecologists have separated two aspects of the response of ecosystems to disturbance;  The ability of a system to resist displacement from its initial state when subject to perturbation  The ability to recover to the initial state after disturbance. A variety of terms have been applied to these two components. The first component has been called inertia by Cairns and Dickson (1977), Orians (1975), Sheehan (1984) and Westman (1978) and resistance by Boesch (1974), Harrison (1979), Pimm (1984), Smith (1980), Sutherland (1981), Vitousek et al. (1981) and Webster et al. (1975). 1  11/17/2020 Lecture 5-------------------------------------------------------------------------------------------------------------------------------------------------------- Terminology used in the analysis of ecosystem stability (adapted from Orians, 1975 ; Westman, 1978). A) B) Lecture 5--------------------------------------------------------------------------------------------------------------------------------------------------------c Ecosystem stability or response to disturbance depends on:  Resistance: Ability of system to absorb small disturbances and prevent amplification.  Resilience: Ability of system to return to its original state.  Robustness: amount of disturbance system can absorb without flipping to alternative state.  Response: Magnitude of change.  Recovery: Extent of return to original state. 2  11/17/2020 Lecture 5--------------------------------------------------------------------------------------------------------------------------------------------------------c The measurement of disturbance and stability 1) Disturbance. 2) Temporal and spatial scales 3) Identifying parameters to measure 4) Resistance 5) Resilience Lecture 5--------------------------------------------------------------------------------------------------------------------------------------------------------c The measurement of disturbance and stability 1.Disturbance Traditionally disturbances have been considered as infrequent events that disrupt the equilibrium state of an ecosystem by producing abrupt changes in structural or functional characteristics. These definition of disturbance is based on the occurrence of a change in ecosystem properties. However, the concept of resistance implies that systems may not change when exposed to some disturbances. Disturbance has been classifies into three categories: 1. Type 1 disturbances do not produce a change in the system (the ecosystem has resistance stability). 2. Type II are those that alter system characteristics but the system returns to its initial state thus exhibiting resilience. 3. Type III are those that produce a permanent alteration in the system. (Sutherland (1981)). 3  11/17/2020 Lecture 5--------------------------------------------------------------------------------------------------------------------------------------------------------c The measurement of disturbance and stability 2 Temporal and spatial scales Recent reviews of stability emphasize that proper scales of time and space are critical to an evaluation of ecosystem responses to disturbance (Connell and Sousa,1983). It is necessary to decide how long and over what space the system should be examined in order to judge resistance, resilience and persistence. It has already been noted that the areal extent and frequency of disturbance exert an important effect on ecosystem response. Resilience cannot be measured if disturbances are so frequent that ecosystem recovery is impossible. Lecture 5--------------------------------------------------------------------------------------------------------------------------------------------------------c The measurement of disturbance and stability 3 Identifying parameters to measure  There is no general agreement about the properties of ecosystems which should be measured in an evaluation of stability components. A number of properties have been considered as indicators of system response to disturbance (Butler, 1984). Some of these properties include indices of diversity, trends in population size of various species particularly those that are regarded as sensitive species, and ecosystem metabolism involving energy and mineral element.  The evaluation of resistance and resilience must ultimately depend on the properties measured and the perspective adopted. The recovery of an ecosystem could be defined in three Ways: 1) Restoration of a disturbed site little bit; 2) Restoration of the initial functional and structural properties of the ecosystem although the species composition may be different; 3) Restoration of the initial condition of the system with respect to species composition as well as all system-level properties. 4  11/17/2020 Lecture 5--------------------------------------------------------------------------------------------------------------------------------------------------------c The measurement of disturbance and stability 4 Resistance Resistance can be measured in terms of the intensity of the disturbance required to alter the system by a given amount. The time required for an initial displacement to occur after the disturbance (the response time) can also be included in the analysis (Hurd and Wolf, 1974). Lecture 5--------------------------------------------------------------------------------------------------------------------------------------------------------c The measurement of disturbance and stability 5 Resilience The elasticity component of resilience involving the time required for ecosystem recovery to an initial state presents a number of measurement problems. The problem through the ecological system can be avoided by measuring elasticity in terms of the time required to attain a percentage similarity of perhaps 50 or 85 per cent between particular properties of the restored system and the initial predisturbance system (Westman, 1978; 1985). 5  11/17/2020 Lecture 5--------------------------------------------------------------------------------------------------------------------------------------------------------c Ecosystem Feedbacks Negative: Stabilizes ecsosytems Positive: Destabilizes ecosystems Ehrenfeld et al. (2005) Lecture 5--------------------------------------------------------------------------------------------------------------------------------------------------------c Three types of Ecosystem change 6  11/17/2020 Lecture 5--------------------------------------------------------------------------------------------------------------------------------------------------------c Lecture 5--------------------------------------------------------------------------------------------------------------------------------------------------------c Succession Succession is the series of predictable changes that occur in a community over time. After a fire, volcano, or other disaster, succession enables an ecosystem to recover. There are two main types of succession: Primary succession is the series of changes that occur in an area where no ecosystem previously existed. For example: a new island formed by the eruption of an undersea volcano, or an area of rock uncovered by a melting sheet of ice. Secondary succession is the series of changes that occur after a disturbance in an existing ecosystem. Both natural and human activities can cause secondary succession. Examples: Natural disturbances: fires and tornadoes 7  11/17/2020 Lecture 5--------------------------------------------------------------------------------------------------------------------------------------------------------c Some theories of succession Facilitation- Each species creates opportunities for the next species. The system cycles through species until a species no longer provides this opportunity and become dominant. Inhibition- Species hold onto the site via competition (and other negative interactions) and only give way to other species due to disturbance or death. Tolerance- Species that make up the final composition of the community are those best able to tolerate environmental conditions. They are neither hindered (inhibition) or helped (facilitation) by other species Lecture 5--------------------------------------------------------------------------------------------------------------------------------------------------------c STEPS OF SUCCESSION Nudation (Topographic, climatic) Invasion (Pioneer organisms) Competition and co-action (aggregation of a large no. of the species at the limited place) Reaction (includes mechanism of the modification of the environment) Stabilization (The final stage of succession is called the climax community) 8  11/17/2020 THANKS Dr. Mohamed A. Elsayad, PhD., Construction & Building Department, Faculty of Engineering, AAST University 9  2/21/2020 Environmental Science (NE466) Dr. Mohamed A. Elsayad, PhD., Construction & Building Department, Faculty of Engineering, AAST University Lecture 1 -------------------------------------------------------------------------------------------------------------------------------------------------------- Course Content Biosphere and the ecosystem components. Environmental resources. Ecological system and equilibrium. The evolution of the mankind’s relationship with the environment. Population & the development and the environment effects. Sustainable development. Consumer lifestyle. Human health and environment degradation. Environmental improvement. Environmental management. 1  2/21/2020 Lecture 1 -------------------------------------------------------------------------------------------------------------------------------------------------------- Course objectives The course objective is introducing the student to: The meaning of the term environment. The importance of natural resources The scientific methods and how science operates. Global changes and common future. Environmental degradation. Natural resources. Sustainability and sustainable development. Reference book: Principles of Environmental Engineering & Science: Third Edition By Mackenzie Davis, Susan Masten. Lecture 1 -------------------------------------------------------------------------------------------------------------------------------------------------------- Environmental Science: is the field of science that integrates physical and biological components of the environment ( including ecology, biology, physics, chemistry,, etc.) and also study the relationships and effects of these components with the organisms in the environment. The historical focus of study for the environment scientists has been the nature environment (atmosphere, lands, water, and their inhabitants as differentiated from the built environment). Modern environmental science has also found applications from the built environment more correctly to the effusions from the built environment. Environmental science is a broad interdisciplinary applied science. 2  2/21/2020 Lecture 1 -------------------------------------------------------------------------------------------------------------------------------------------------------- Environmental Science: In its broadest sense encompasses all the fields of natural science: Biology Is the natural science that involves the study of life and living organisms. Ecology The branch of biology that deals with the relations of organisms to one another and to their physical surroundings. Chemistry Is the study of the structure, properties, composition, mechanisms, and reactions of organic compounds. Physics Natural science that involves the study of matter and its motion and behavior through space and time, along with related concepts such as energy. Geology The science which deals with the physical structure and substance of the earth. Geography The study of the diverse environments, places, and spaces of Earth's surface and their interactions. Lecture 1 -------------------------------------------------------------------------------------------------------------------------------------------------------- Environmental Science: Anthropology Is the study of various aspects of humans within past and present societies. Demography The study of statistics such as births, deaths, income, or the incidence of disease, which illustrate the changing structure of human populations. Economic Pertaining to the production, distribution, and use of income, wealth, and commodities. Political Relating to the government or public affairs of a country. Philosophy is the study of general and fundamental problems concerning matters such as existence, knowledge, values, and reason. Ethics is the part of environmental philosophy which considers extending the traditional boundaries of ethics from solely including humans to including the non-human world. 3  2/21/2020 Lecture 1 -------------------------------------------------------------------------------------------------------------------------------------------------------- Environmental Science Main Goals: The field of environmental science can be divided into three main goals:  Learn how the natural world works.  Understand how humans interact with the environment.  Determining how humans affect the environment also includes finding ways to deal with these effects on the environment. Natural Science: Systematized knowledge derived from and tested by recognitions and formulation of problems, collection of data through observation, and experimentations. Natural Science Includes diverse disciplines as biology, chemistry, geology, and physics. Social Science: The study of people and how they live together as families, communities, and nations. The social science fields that are incorporated into environmental science include geography, economics, and political science. Lecture 2 ------------------------------------------------------------------------------------------------------------------------------------------------------- The scientific methods: Observation Questions Hypothesis Prediction Test Results 4  2/21/2020 Lecture 1 -------------------------------------------------------------------------------------------------------------------------------------------------------- Quantitative Environmental Science: The scientific method deals with data , that is, with recorded observations. The data are sample of universe of possibilities that may be representative or they may be skewed. The representative data usually contain some random variations. The gathering methods and independent verification are considered the fundamental of science. If we can use certain assumptions to tie together a set of generalizations, we formulate a theory and the theories that have gained acceptance over a long time are known as laws like the laws of motions which describe the behavior of moving bodies. Logic is, a part of all theories, divided into two types which are qualitative and quantitative. For example we can qualitatively state that when the amount of wastewater entering a river is too high, the fish die. When the data are quantitative, we need mathematic relationships to prove the theory. Lecture 1 -------------------------------------------------------------------------------------------------------------------------------------------------------- Quantitative Environmental Science: Quantitative Environmental Science is an organized collection of mathematical theories that may be used to describe and explore the environmental relationships. For example ‘ when the mass of organic matter entering a river equals x kilograms per day, the amount of oxygen in the stream is y. Therefore the quantitative logic enables us to explore ‘what if?’. For example if we reduce the amount of organic matters entering the stream, how much will the amount of oxygen in the stream increase?. Mathematical theories often enable us to bridge the gap between the observation data from the experiment and the field. For example if we control the amount of oxygen in the fish tank in the laboratory, we can determine the minimum amount required for the fish to be healthy. We can then use this number to determine the acceptable mass of organic matter placed in the stream. 5  2/21/2020 THANKS Dr. Mohamed A. Elsayad, PhD., Construction & Building Department, Faculty of Engineering, AAST University 6  2/15/2019 Environmental Science (NE466) Dr. Mohamed A. Elsayad, PhD., Construction & Building Department, Faculty of Engineering, AAST University Lecture 2 -------------------------------------------------------------------------------------------------------------------------------------------------------- Engineering: Is a profession that applies science and mathematics to make the properties of matter and sources of energy useful in structures, machines, products, systems, and processes. Environmental engineering: Environmental Engineering is manifest by the sound engineering thought and practice in the solution of the problems of the environmental sanitations, in the provision of safe, palatable, and ample public water supplies; the proper disposal of or recycle of wastewater and solid wastes; the adequate drainage of urban and rural areas for proper sanitation; and the control of water, soil, and atmospheric pollution, and the social and environmental impact of these solutions. Furthermore it is concerned with engineering problems in the field of public health, such as control of diseases, the elimination of industrial health hazards, and the provision of adequate sanitation in urban. Rural, and recreational areas, and the effect of technological advances on the environment (ASCE, 1977). Environmental science and, in particular, quantitative Environmental science provides the fundamental theories used by Environmental engineers to design solutions for the Environmental problems. 1  2/15/2019 Lecture 2 ------------------------------------------------------------------------------------------------------------------------------------------------------- Environmental engineering The basic components of a conventional hydropower plant: The shaft that connects the turbine and generator Lecture 2 -------------------------------------------------------------------------------------------------------------------------------------------------------- Environmental engineering Example) A dam presents an obvious obstacle to migrating fish. Dams block the downstream movement of fish to the waters where they will spend their adult lives. 2  2/15/2019 Lecture 2 ------------------------------------------------------------------------------------------------------------------------------------------------------- Environmental Engineers and Environmental scientists provided the knowledge of the of the depth of water and the height of the steps the fish could negotiate. Lecture 2 ------------------------------------------------------------------------------------------------------------------------------------------------------- Ecology is the scientific analysis and study of interactions among organisms and their physical environment. The ecologist deal with the ecological complexity using the ecological models to represent or describe the components of the ecological system. Ecosystems One ecosystem is any area that happens to have an specific set of features (living species and physical-chemical conditions) that make it significantly different from its surroundings. Thus, a forest is an ecosystem, but a lagoon or a puddle of water in that forest, are themselves ecosystems too. The limits of many ecosystems are difficult to define. For instance, a lagoon in a forest can be fed with water from an aquifer that extends throughout an area much bigger than the forest itself, and that also feeds with water the farm-land that surrounds the forest. This way, the lagoon, the forest and the farm-land are connected. Ecosystems are not isolated in Nature: there are connections and transitional areas between them. 3  2/15/2019 Lecture 2 ------------------------------------------------------------------------------------------------------------------------------------------------------- Ecosystems When an ecologist tries to describe an ecosystem, they have to describe the following sorts of facts:  The set of living species in it.  The set of physical and chemical conditions,  The relationships between the living species.  The relationships between the physical-chemical conditions.  The relationships between the physical-chemical conditions and the living species. Lecture 2 ------------------------------------------------------------------------------------------------------------------------------------------------------- Ecosystems An ecosystem is a group or community composed of living and non-living things and their interactions with each other. They can be natural as well as artificial. Every ecosystem has two components, namely, biotic (living) components and abiotic (nonliving) components. All organisms are dependent on the environment to carry out their natural life processes (birth to death) and to meet their physical requirements (food, energy, water, oxygen, shelter etc.). 4  2/15/2019 Lecture 2 -------------------------------------------------------------------------------------------------------------------------------------------------------- Interaction Biotic components and abiotic components of an ecosystem interact with and affect one another. If the temperature of an area decreases, the life existing there must adapt to it. Example: Global warming Lecture 2 -------------------------------------------------------------------------------------------------------------------------------------------------------- Types of systems: 5  2/15/2019 Lecture 2 -------------------------------------------------------------------------------------------------------------------------------------------------------- The Earth system: The Earth is a closed system where materials cycle between the lithosphere, atmosphere, hydrosphere, and biosphere. Any change in one reservoir creates change in others. Although the processes or changes which have occurred throughout the past 2.5 billion years of Earth history have remained the same, the rates at which the processes, occur are highly variable: some are instantaneous and others are extremely slow. Lecture 2 -------------------------------------------------------------------------------------------------------------------------------------------------------- Lithosphere: Lithosphere is the rigid, outermost layer of Earth. It consists of crust and uppermost mantle and lies above asthenosphere. Earth is made up of several layers. The outermost layer is called Earth's crust. The thickness of the crust is about (5–30 km). Beneath the crust is a layer of rock material that is also solid, rigid, and relatively cool, but is assumed to be made up of denser material. This layer is called the upper part of the mantle, and varies in depth from about (100 km) below Earth's surface. 6  2/15/2019 Lecture 2 -------------------------------------------------------------------------------------------------------------------------------------------------------- Earth’s layers Lecture 2 -------------------------------------------------------------------------------------------------------------------------------------------------------- Hydrosphere: is the combined mass of water found on, under, and above the surface of a planet. 70% of Earth is water while about 30% is land (US Geological Society). 7  2/15/2019 Lecture 2 -------------------------------------------------------------------------------------------------------------------------------------------------------- Atmosphere: The gaseous envelope surrounding the earth. The density of the atmosphere decreases outward, because the gravitational attraction of the planet, which pulls the gases and aerosols (microscopic suspended particles of dust, smoke, or chemicals) inward, is greatest close to the surface. The current molecular composition of Earth’s atmosphere is nitrogen (N2), 78.08 percent; oxygen (O2), 20.95 percent; argon (A), 0.93 percent; water (H2O), about 0 to 4 percent; and carbon dioxide (CO2), 0.04 percent. Inert gases such as neon (Ne), helium (He), and other constituents such as nitrogen oxides, compounds of sulfur, and compounds of ozone are found in lesser amounts. Lecture 2 -------------------------------------------------------------------------------------------------------------------------------------------------------- Biosphere: The biosphere may be defined as the sphere of the Earth where life exists. The main layers of the Earth that support life are the upper part of the crust with its thin layer of the soil, the hydrosphere, and the lower atmosphere (Robert Krebs, 1922). Factors effect on biosphere -Distance between the earth and the sun. -Seasons and seasonal climate changes are direct results of the tilt of the Earth towards or away from the Sun. Summer months allow half of the planet to warm while the other half cools. Six months later, the temperatures shift in the opposite direction. -Chemical erosion is a great example of a landscape changing one molecule at a time. -Oxidation and reduction reactions change the composition of rocks and organic materials. There is also biological erosion. Tiny organisms, such as bacteria, are constantly working to break down organic and inorganic materials. 8  2/15/2019 Lecture 2 -------------------------------------------------------------------------------------------------------------------------------------------------------- Ecosphere: Some ecologists preferred to limit the biosphere to all living things, as Teilhard de Chardin had done. By insisting on this restriction, ecologists found themselves lacking a word to describe the total ecosystem – the totality of living organisms and the inorganic environment that sustains them. Cole (1958) coined the term ecosphere to play that role. Interdependence: The survival of species is dependent on the other living organisms and nonliving components. Lecture 2 -------------------------------------------------------------------------------------------------------------------------------------------------------- Levels of Ecological organization 9  2/15/2019 Lecture 2 -------------------------------------------------------------------------------------------------------------------------------------------------------- Levels of Ecological organization Lecture 2 -------------------------------------------------------------------------------------------------------------------------------------------------------- Natural Environment is the entire environment, without human presence or interference. There are certain components in our environment which are entirely natural like land, water, and Rocks. They therefore form 'Natural Environment' Built Environment: is formed by the buildings and other structures that humans construct in the natural environment. There are many other components in the environment which are created by human beings such as equipment, drainage systems, transport systems, and power systems. 10  2/15/2019 Lecture 2 -------------------------------------------------------------------------------------------------------------------------------------------------------- Natural & Built Environment Humans beings use their skill and technology to create things from the natural environment so that their needs can be satisfied. which means, the irrelevant natural resources, we use our skill and technology to create a lot of things which are part of built environment to satisfy our needs. Iron Ore Skills & Technology Steel product Lime, Silica, Alumina, Iron compounds Skills & Technology Concrete product Lecture 2 -------------------------------------------------------------------------------------------------------------------------------------------------------- Environmental Connections 11  2/15/2019 Lecture 2 -------------------------------------------------------------------------------------------------------------------------------------------------------- Natural & Built Environment Some of the interactions between the built and natural environments have effects that cause concern: consumption of non-replenishable resources such as fossil fuel. consumption of resources without replacement, such as hardwood forests. harmful changes to local habitat, such as deforestation. harmful changes to global habitat, such as climate changes. THANKS Dr. Mohamed A. Elsayad, PhD., Construction & Building Department, Faculty of Engineering, AAST University 12  2/24/2019 Environmental Science (NE466) Dr. Mohamed A. Elsayad, PhD., Construction & Building Department, Faculty of Engineering, AAST University Lecture 3-------------------------------------------------------------------------------------------------------------------------------------------------------- Natural resources  Natural resources are the resources that we get directly from nature. For example sunlight, water, and petroleum.  A natural resource is often characterized by amounts of biodiversity and geodiversity existent in various ecosystems.  Some natural resources such as sunlight and air can be found everywhere, and are known as ubiquitous resources.  The values of the natural resources are : - Economic value --Legal value -- Aesthetic value -- Ethical value. 1  2/24/2019 Lecture 3 ------------------------------------------------------------------------------------------------------------------------------------------------------- Use and Over Exploitation of the Natural Resources: Natural resources, such as A forest, is a biotic community predominantly of trees, shrubs and other woody vegetation. This invaluable renewable natural resource is beneficial to humans in many ways. (a) Conservation of Soil: Forests prevent soil erosion by binding the soil with the network of roots of the different plants and reduce the velocity of wind and rain - which are considered the main reason of erosion. (b) Reduction of Atmospheric Pollution: By using up carbon dioxide and giving off oxygen during the process of photosynthesis, forests reduce pollution and purify the environment. (C) Control of Water flow: In the forests, the thick layer of humus infiltrates rain water preventing run- off, thereby preventing flash-floods. Lecture 3-------------------------------------------------------------------------------------------------------------------------------------------------------- Various methods of categorizing natural resources These include source of origin, stage of development, and by their renewability. On the basis of origin, resources may be divided into: – Biotic resources. – Abiotic resources. Considering their stage of development, natural resources may be referred to in the following ways: – Potential resources.  petroleum remains a potential resource – Actual resources.  quantity and quality determined – A reserve resource.  profitably in the future – Stock resources.  lack of technology 2  2/24/2019 Lecture 3-------------------------------------------------------------------------------------------------------------------------------------------------------- Various methods of categorizing natural resources Many natural resources can be categorized as either renewable or non- renewable: Lecture 3 ------------------------------------------------------------------------------------------------------------------------------------------------------- Energy Energy may be defined as the capability of an object or system to do work. The technical idea of work is connected with doing things and making changes to things. For example, energy can exist as heat, light, and sound; it produces motion and electricity. The earth constantly receives energy from the sun and this energy is used for example to warm the oceans and to drive the weather systems of the world that produce effects such as wind and rain. Fossil fuels such as coal, crude oil and natural gas were formed by the decomposition of prehistoric organisms, such as plants, during long-term geological changes in the Earth. Primary Energy is the total energy contained in natural reserves or in flows of primary fuels such as coal, oil or gas. The primary energy of a fuel is measured in the ‘raw’ state, before any energy is used in conversion or distribution. Energy transformation is an activity that coverts primary energy into another form. Examples of transformation occur when fuels are converted into electricity, or crude oil converted into petroleum. 3  2/24/2019 Lecture 3 ------------------------------------------------------------------------------------------------------------------------------------------------------- Energy Secondary Energy is the energy contained in a fuel which results from a transformation process. examples of secondary energy sources include most e1ectricity, manufactured gas, and surplus hot water. The secondary energy of electricity is only 30 to 40 per cent of the primary energy contained in the original fuels; the rest is lost in the conversion and distribution processes. Delivered Energy is energy content as it is received by the consumer. Delivered energy is the delivered energy or ‘site energy’ for which the consumer generally pays money, although some of this energy will be lost by conversion processes within the building. Useful Energy is the energy required to perform a given task. It is needed to balance the heat losses and heat gains in a typical calculation. Embedded Energy is the total energy needed for making and using a product. Some methods of calculation take account of raw material extraction, transport, manufacture, installation, and eventual deconstruction. Lecture 3 ------------------------------------------------------------------------------------------------------------------------------------------------------- Energy Power is the rate at which energy is used or produced. The energy is divided by the time taken to get the rate or speed at which it is used. Higher powered performance means that work is done faster and that energy is used more quickly. The unit of power is the watt (W), where 1 watt = 1 joule/second. The watt is another relatively small unit when we need to describe high-power situations such as energy for buildings, so you will more commonly encounter kilowatts(kW) and megawatts (MW). The power rating of a device, such as an electric lamp labelled 20 W, tells us thelamp’s potential for using energy, if we switch it on. But to know how much energy the lamp uses we must know the length of time it is switched on. The formula for power is Power energy/time, and changing the expression around gives a formula for energy: Energy = power X time 4  2/24/2019 Lecture 3 ------------------------------------------------------------------------------------------------------------------------------------------------------- Solar Energy The Sun is the source of almost all energy in common use on Earth, even if the solar energy has been stored for many years in other forms such as oil deposits. Plants and trees use solar energy to grow material which can be burned directly, or decomposed into gases, or preserved underground as coal and oil. The energy in waves, wind and ocean heat is also provided by the Sun. Photovoltaic (PV) cells Solar panels consist of photovoltaic cells, which convert sunlight to electricity (volt). An array of photovoltaic cells make up a solar panel. These cells consist of silicon atoms that lose an electron when sunlight strikes their surface. Lecture 3 ------------------------------------------------------------------------------------------------------------------------------------------------------- Solar Energy Sunlight consists of extremely small particles called ‘photons’ that are capable of knocking electrons off of the silicon atoms present on photovoltaic cells. These electrons make up direct current (DC), but as most of our household appliances function on alternating current (AC), it becomes important to convert electric current from DC to AC. This is done by another component called an ‘inverter’, which is yet another important element of the system.. 5  2/24/2019 Lecture 3 ------------------------------------------------------------------------------------------------------------------------------------------------------- Solar Energy Thermal technology The other method of harnessing the energy from sunlight is through the use of solar thermal technology. This consists of ‘solar collectors’ – devices that capture solar radiation. ‘Flat plate’ and ‘evacuated tube’ are two types of collectors. The flat plate variant, as its name indicates, consists of a dark flat plate absorber, containing a heat-transport liquid. Evacuated tube collectors, on the other hand, contain multiple evacuated glass tubes containing an absorber plate, along with a transfer fluid (e.g., water). Lecture 3 ------------------------------------------------------------------------------------------------------------------------------------------------------- Solar Energy In the presence of sunlight, solar collectors heat up and transfer the heat to the heat-transport liquid (typically water, or a mixture of glycol and water in cold regions to prevent the mixture from freezing). This liquid is then transported to a heat-exchanger liquid housed inside the water tank. After transferring its heat to the water in the tank, the heat-transport liquid flows back to the collectors to be heated again. This process is repeated until the desired temperature is achieved. 6  2/24/2019 Lecture 3 ------------------------------------------------------------------------------------------------------------------------------------------------------- Hydropower Energy Lecture 3 ------------------------------------------------------------------------------------------------------------------------------------------------------- Hydropower Energy Hydropower Calculations P = power in kilowatts (kW). g = gravitational acceleration (9.81 m/s2 ). η = turbo-generator efficiency (0