Renewable Energy Engineering I Past Paper PDF

# Scoring Indicators **COURSE NAME**: Renewable Energy Engineering I Course Code: 3293 QID:2109240089 ## PART A | Q No. | Scoring Indicators | Split Score | Sub Total | Total Score 1x9=9 | | :---: | :-------------------------------------------------------------------------------------------------...

# Scoring Indicators **COURSE NAME**: Renewable Energy Engineering I Course Code: 3293 QID:2109240089 ## PART A | Q No. | Scoring Indicators | Split Score | Sub Total | Total Score 1x9=9 | | :---: | :--------------------------------------------------------------------------------------------------------------------------------------------------------------- | :----------: | :-------: | :------------------: | | 1.1 | Any two disadvantages | 0.5x2 | 1 | 1 | | | * The production is low during winters and on cloudy days. | | | | | | * Installation and the initial cost of the materials are expensive. | | | | | | * Space consumption is more for obtaining high power out. | | | | | 1.2 | Solar collector is a device which collects solar energy and transforms the solar energy to the form which can be utilized according to the system. | 1 | 1 | 1 | | 1.3 | Mirror reflects the light which emerges from the cooker. | 1 | 1 | 1 | | 1.4 | Get fresh distilled water from impure water. The impure saline water is converted into the distilled water by eliminating dissolved salts as well as other | 1 | 1 | 1 | | | dissolved impurities and suspended solids. | | | | | 1.5 | The module is the arrangement of solar cells in parallel or series for power generation. | 1 | 1 | 1 | | 1.6 | Any two components | 0.5x2 | 1 | 1 | | | * Solar panels | | | | | | * Inverter | | | | | | * Charge controllers | | | | | | * Metering systems | | | | | | * Battery | | | | | 1.7 | The inverters convert the generated direct current(DC) to alternating current(AC). | 1 | 1 | 1 | | 1.8 | A DC-DC converter is used to regulate constant output voltage under various operating conditions. | 1 | 1 | 1 | | 1.9 | Any two applications | 0.5x2 | 1 | 1 | | | * WaterPumping | | | | | | * StreetLighting | | | | | | * Traffic lights | | | | | | * Telecommunication and signaling field | | | | ## PART B | | | | | | | :-- | :--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | :-: | :-: | :-------: | | I.1 | Greenhouse Effect | 3 | 3 | 3x8=24 | | | The phenomenon whereby the earth's atmosphere traps solar radiation, due to the presence of gases such as carbon dioxide, water vapor, and methane in the atmosphere that allow incoming sunlight to pass through but absorb heat radiated back from the earth's surface. The major causes of the greenhouse effect includes deforestation, | | | | | | burning of fossil fuels, usage of nitrogen oxide fertilizers, industrial effluents and landfills | | | | | I.2 | Evacuated tube type collector | 3 | 3 | 3 | | | Evacuated tubes are the absorbers of solar water heaters. They use solar energy for water heating made up of glass tubes which are evacuated with air and have heat transfer fluid for the water transport. They are arranged in parallel rows. The outer layer, made up of glass, traps the heat from the sun and the absorbance | | | | | | layer ensures the heat is trapped in the heat pipe. The trapped heat is then transferred to the copper heat exchanger in the manifold. The pump then circulates water to the heat exchanger. This water is solar heated then it is transferred back to the storage tank. The entire process keeps on repeating until the water becomes completely hot | | | | | I.3 | Principle of Sensible heat storage | 3 | 3 | 3 | | | In Sensible heat storage thermal energy is stored by virtue of storage capacity and the change in temperature of the material during the process of charging and discharging (Raising the temperature of a liquid or solid to store heat and releasing it with the decrease of temperature when it is required). Materials used in sensible heat storage must have high | | | | | | heat capacity, high boiling and melting point. On the basis of heat storage media,it can be classified as liquid | | | | | I.4 | Natural Circulation | 1. 5+1. 5 | | 3 | | | Figure, explanation 1.5 marks each | | | | | | Natural Power solar water heaters consist of an evacuated tube solar collector and storage water tanks that are connected together; water tank on the top and evacuated tube collector on the bottom. As water in the vacuum tubes is heated, it rises naturally into the tank, while cool water in the tank flows down to the bottom | | | | | | of the vacuum tubes, causing circulation in the system. Solar water heaters can move water or a heat-transfer fluid through the system without pumps. | | | | | | The image is a diagram of a solar water heater system, showing the hot water distribution, auxiliary hot water tank, insulation, cold water main, and solar collector. | | | | | 1. 5 | Active and Passive heating systems | 1+1+1 | 3 | 3 | | | Any three points on each | | | | | | | | | | | | Active solar heating systems | Passive solar heating systems | | | | | | In active solar space heating, pumps, collectors, storage tanks, and other mechanisms are used to circulate heat in homes. | In passive solar heating systems, the collectors are used to gather energy and heat is trapped and circulated naturally, without involving mechanical devices. | | | | | | Active systems are more complicated | Passive heating systems are less complicated | | | | | | Active space heating systems are more expensive | Passive systems are less expensive | | | | | | Active heating systems can be retrofitted in existing homes with traditional heating systems, in many different ways. | Passive heating systems can only be implemented in new homes, so it's only relevant for those who are about to build a new house. | | | | | I.6 | Hybrid P V systems Block diagram | | 3 | 3 | | | The image is a block diagram of a hybrid PV system. it consists of PV array connected to a Charge Controller and a rectifier. It can then route power into a Battery or DC load. The battery runs to an Inverter and then sends Ac Load. It can also utilize Engine generators, wind turbines, gride backup to power Ac Load. | | | | | I.7 | Steps and Equation - 2 marks | | 3 | 3 | | | Final Answer with unit - 1 mark | | | | | | Battery Capacity = 100Ah Discharge Duration = 10 hours Current drawn by the battery = Battery capacity/ Discharge duration = $\frac{100}{10}$ = 10 A | | | | | I.8 | Step and no of battery identification -2 marks | | 3 | 3 | | | Final Answer = 1 marks | | | | | | The capacity of each battery = 150 Ah Voltage of each battery = 12 V Output capacity required = 450 Ah Capacity (C) = 1 ampere × 1 hour (Ah) By connecting batteries in parallel, high current or high capacity is obtained. | | | | | | Also, the capacity of each battery in parallel is additive. Number of batteries needed = total capacity required / capacity of each battery = $\frac{450 Ah}{150 Ah}$ =3 | | | | | | For batteries connected in parallel, voltage remains the same which is equal to the voltage of a single battery. | | | | | I.9 | Diagram - 1 mark Explanation - 2 marks | | 3 | 3 | | | A buck converter is a DC to DC Converter. The average DC output voltage is less than the input and regulated DC voltage. There are two modes of operation, mode one operation gives the reverse biased diode and the switch will be turned on. In mode 2 the diode is forward biased and the switch is off stage. | | | | | | The filter capacitor is large and results in constant de output voltage. It is a voltage step down and current step up converter. | | | | | | The image contains a circuit diagram of a buck converter with the label: Buck Converter | | | | | I.10 | Block diagram - 1 marks, explanation -2 marks | | 3 | 3 | | | In this type of charge controller, a switch S1 is connected in shunt with the PV panel, which is turned | | | | | | on when the battery voltage reaches its overvoltage limit (VR). The PV array is short-circuited and it no more feeds the battery. The blocking diode prevents short-circuiting of the battery. The blocking diode also prevents the battery from discharging through the PV | | | | | | array during nights and low insolation periods. The switch S2 allows the battery to discharge through the load. When the battery voltage reaches the threshold value (LVD), the switch S2 is turned off to prevent deep discharging of the battery. | | | | | | The image contains a block diagram of a PV Panel -> VRH Control and LVDH Control -> Voltage Level Detactor -> VRH Control and LVDH Control can deliver to a Load or Battery. | | | | ## PART C | | | | | | | :---- | :----------------------------------------------------------------------------------------------------------------------------- | :-: | :-: | :-------; | | III. | Diagram - 2 marks Any four points - 5 marks | | 7 | 7x6=42 | | | The image contains diagrams of: FLAT-PLATE TYPE and CONCENTRATING TYPE | | | | | | | | | | | IV | | | | | |Non concentrating |Concentrating| | |Collectors|Collectors| | |Absorber area is large | Absorber area is small| | |Concentration ratio is 1.| Concentration ratio is high| | |It uses both beam and diffuse radiation.| It mainly uses the beam radiation| | |Application limited to low temperature, suitable for all places as it can work on clear and cloudy days| High temperature applications such as power generation are suitable where there are more clear days in a year.| | |Simple in maintenance.| Difficult in maintenance| | |Comparatively low cost |They are costly| | |Design is easy |Complex design | | | IV | Diagram - 4 marks Explanation - 3 marks | 3+4 | 7 | 7 | | | Linear fresnel reflector concentrators are made from multiple trips of straight reflecting materials which are mounted on specially designed frames. The mirror will reflect the incident light on to a metallic collected by that runs actually above the array of reflector. These reflector strips are more such a way that they always reflected the incidents and light to the receiver tube. | | | | |V|Diagram - 3 marks Explanation - 4 marks |3+4| 7 |7 |The image contains diagrams of: Parallel light rays-> Fresnel lens -> Solar cell and a diagram of glass with sunlight that contains elements of Sunlight, Glass, Cold air in Hot air out Food to be dried, insulated casing, Black absorbtion surface |Fresnel lens - parallel sunlight and solar cell |Solar dryers are used to eliminate the moisture content from crops, vegetables, and fruits. |The solar dryer consists of a box made up of easily available and cheap material like cement, galvanized iron, brick, and plywood. The top surface of the dryer is covered by transparent single and double-layered sheets. |The inside surface is colored black to absorb the incoming solar radiation. |Since the box is insulated, the inside temperature of the box is raised. |The air is ventilated through the small holes at the top of the box. |As the inside air gets warm, it rises by the natural circulation process and removes the moisture from the fruits, vegetables, and the crops placed in trays inside the box. |To fill the vacuum, fresh air comes in by a forced draught process and the process continues.| | VI | Diagram - 4 marks Explanation - 3 marks | 4+3 | 7 | 7 | | | Line focusing concentrating solar collector field consists of many parallel rows of collectors to achieve required temperature and energy gain. Solar radiation which is directly normal to the Solar collector service can be focused and useful in heating the absorber tubes | | | | | | along with the heat transfer fluid. Rankine cycle is the thermodynamics cycle employed in these type of power plant the Solar collector depend on the concentration ratio and the working fluid is normally any type of organic fluids | | | | |The image contains the name Heated Water. |The image contains the name Reflecting Surfaces and water piping | VII | Diagram - 3 marks Explanation 4 marks | 3+4 | 7 | 7 | | | Space cooling system that converts heat from the sun into cooling that can be used for refrigeration and air conditioning. | | These systems collect the solar power and use its driven cooling process which is used to decrease and control the temperature.| | | The absorption typer holding process relays on them evaporation of refrigerant. | | Absorption cycle completes pressurization by dissolving a refrigerant in an absorbent instead of mechanical | | | | |VIII|Explanation- marks | 4+3 |7|7 | Classification =3 marks | Solar greenhouses are enclosures where crops, vegetables or flowers are provided a proper environment under adverse climatic conditions for plant growth and production | All greenhouses receive necessary sunlight from the sun required for photosynthesis and also supply heat during cold months from sun In tropical countries the solar insolation and ambient temperature are quite high and therefore summer greenhouses can be designed |compressor it processes for components they are | The absorber Hold and absorbent-refrigerant mixture that is delivered to the generator through a liquid pump using external solar energy |The generator takes the mixture and heats it up up using the external solar energy collected by using the solar panel The solution starts to boil in reaction to the heat water also boils and vapour flows to the condenser. The condenser liquefies the water vapour and thenew liquid condensate is then directed towards the evaporator through an expansion valve Finally the evaporation of the refrigerant causes the evaporator to observe the heat from the |cooled space creating a cooling effect cycle repeats. The image contains a lot of diagrams and labels such as absorber, generater, evaporation etc. X IX | Steps - 6 marks Final answer with unit-I marks| 6+1 | 7 | Required Load in Watts Ptotal = (4 x 40 W)+ 100W = 260 Watts | This is the daily load per hour in watts we need to power up solar panels| Consumption time= |4 hours daily | Sunshine hours = 4 hours |Daiiy power = 260W x 4Hrs = 1040Wh per day. Hourly power charge = 1040W/H Hrs = 260W/h Rating of solar panel ==260W | X| VI characteristics-2 marks|2+5| 7| 7 | Defining the terms short circuit current, open circuit maximum power-5 |The image is a graph open circuit The maximum current canbe deliverd by a constructon| | It is measured | |The cell depends on the density of light.| Open circuit voltage measuring the Voltage| It depends in the of the call Whenload is connected to the| |Manufacturing the ranges between |cell maximum that delivers 06 v. | XI |block diagram _ 3 marks explanation 4 marks| 3+4 PWM stands for "Pulse Width Modulation" the PWM charge| Controller purpose of ensure ethel charties| charging aud discharing help regulate the XII | Voltage required {Vsystem) =24 V Capacity required Csystem =900 Ah| 1+2+1=+ | 7 1 + 2| now hist the standard value of | | Voltage values | The battery in sames XIII | Components BOS| 7 Solar battery For off system is a solar the energy prodused by the | Solar inverter-Auverter convert that regular needs | the The high XIV. |Block diagram 3 marks Explanation +3| 7 | | the Panels during day time Charge |spreaa out The