Jawaharlal Nehru Technological University Hyderabad
Jawaharlal Nehru Technological University Hyderabad B.Tech III Year NON-CONVENTIONAL POWER GENERATION Previous Question Paper (February - 2022 - R16)
Answer any five questions. All questions carry equal marks.
Main
What is Extraterrestrial solar radiation? Explain.
Answer
Extraterrestrial solar radiation is the solar energy incident on the outer boundary of the Earth's atmosphere. It represents the total power density of the sun's electromagnetic radiation before it undergoes attenuation, scattering, or absorption by atmospheric constituents such as clouds, aerosols, water vapor, and gases.
The intensity of this radiation is defined by the Solar Constant (Isc), which is the average solar irradiance at the mean Earth-Sun distance (1 astronomical unit). Its value is approximately 1367 W/m². Because the Earth's orbit is elliptical, the actual extraterrestrial radiation varies throughout the year by about ±3.3% due to the changing distance between the Earth and the Sun, governed by the equation:
where n is the day of the year. This radiation is primarily composed of ultraviolet, visible, and infrared light, and serves as the fundamental upper limit for all solar energy harvesting technologies.
At Suva (ϕ = -18°) at 9 a.m. on 20 May, the irradiance measured on a horizontal plane was Gh = 1.0 MJh⁻¹ m⁻². Determine the angle θz between the beam radiation and the vertical, and hence find the irradiance G* = (Gb + Gd)* measured in the beam direction. (Assume that Gd << Gb, as might be the case on a clear day).
Answer
Given: Latitude (φ) = -18°, Time = 9 a.m., Date = 20 May. First, calculate the declination angle (δ) for May 20 (n = 140):
Next, determine the hour angle (ω) for 9 a.m. (3 hours before solar noon):
The cosine of the zenith angle (θz) is given by:
Since the horizontal irradiance G_h is the projection of the beam irradiance G_b onto the horizontal plane, G_h = G_b * cos(θz). Given G_d << G_b, we assume G* ≈ G_b:
With the help of schematic diagram, explain technique of solar heating and cooling.
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Explain the working of solar heliostat systems by drawing a suitable diagram.
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Why Tracking is needed and what advantage does MPPT give in the real world? Explain.
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If the saturation current is 10⁻⁸ A m⁻², calculate and draw the I–V characteristic as a graph to 0.2 V.
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A small household-lighting system is powered from a nominally 8 V (i.e. four cells at 2 V) storage battery having a 30 Ah supply when charged. The lighting is used for 4.0 h each night at 3.0 A. Design a suitable photovoltaic power system that will charge the battery from an arrangement of Si solar cells.
How will you arrange the cells?
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How will the circuit be connected?
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How will you test the circuit and performance?
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What is Betz limit? Using Betz model of a wind turbine, derive the expression for power extracted from wind? What is the maximum theoretical power that can be extracted and under what condition?
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Write short notes on wind energy conversion systems along with their applications.
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A wind turbine maintains a tip-speed ratio of 8 at all wind speeds. At which wind speed will the blade tip exceed the speed of sound?
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Write the merits and limitations of floating drum plant and fixed dome type plant used in biogas production.
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The following data are given for a family biogas digester suitable for the output of ten cows: i) The retention time is 25 days ii) Temperature = 30° C. iii) Dry matter consumed per day = 3 kg. iv) Biogas yield = 0.34 m³ per kg. v) Burner efficiency = 60%. vi) Methane proportion = 0.8. vii) Heat of combustion of methane = 28 MJ/m³. Calculate the volume of biogas digester and power available for it.
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Describe the construction and working of Lead acid batteries and discuss their importance.
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Distinguish between the working of single and double basin systems.
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