Pradip Majumdar, Ph.D Professor Mechanical Engineering Northern Illinois University

1. UEET 601 Introduction to Emerging Technolog Fall 2008 Unit: Energy Engineering Pradip Majumdar, Ph.D Professor Mechanical Engineering Northern Illinois University

2. Introduction to Energy Engineering Pradip Majumdar Department of Mechanical Engineering

3. Solar Energy

4. ELEMENTS OF ENERGY MODULE Solar Energy Principles Solar Radiation Extraterrestrial Solar Radiation Solar Components Solar Radiation at Earth Surface Flat Plate Collector Photovoltaic Cell Optical Properties for Materials for Solar Radiation Focusing Collector Applications Energy Storage Geographical Location and Weather Conditions Solar Thermal Power Generation Solar Heating and Cooling Direct Electric Power Generation Direct, Diffuse, Reflected Radiation SOLAR

5. Pedagogical Content Lecture Module: Solar Radiation What is extraterrestrial radiation ? Major Characteristics of Earth: Major Characteristics of Sun: Spectral Distribution of Solar Radiation: Solar Radiation at Earth’s Surface The Solar Constant:

6. Solar Radiation Energy • The sun’s structure and characteristics determine the nature of the energy it radiates into space. • Energy is released due to continuous fusion reaction with interior at a temperature of the order of million degrees. • Radiation is based on sun’s outer surface temperature of 5777 K.

7. Thermal Radiation • Thermal radiation is the intermediate portion (0.1 ~ 100m) of the electromagnetic radiation emitted by a substance as a result of its temperature. • Thermal radiation heat transfer involves transmission and exchange of electromagnetic waves or photon particles as a result of temperature difference.

8. Planck’s Spectral Distribution of Black Body Emissive Power The thermal radiation emitted by a black substance covers a range of wavelength (), referred as spectral distribution and given as

9. Black Body Emissive Power The total black body emissive power is obtained by integrating the spectral emissive power over the entire range of wavelengths and derived as Where  = Stefan-Boltzman constant =

10. Real Body Emissive Power Spectral Emissive Power Total Emissive Power

11. Extraterrestrial Radiation Solar radiation that would be received in the absence of earth atmosphere. Extraterrestrial solar radiation exhibits a spectral distribution over a range of Wavelengths: - Exhibit a spectral distribution over a ranger of wavelength: 0.1- 2.5 - Includes ultraviolet, visible and infrared

12. Solar Constant Solar Radiation intensity at outer limit of atmosphere: Solar energy per unit time received on a unit area of surface perpendicular to the direction of propagation at mean earth-sun distance outside earth atmosphere.

13. Variation of Extraterrestrial Radiation Solar radiation varies with the day of the year as the sun-earth distance varies. An empirical fit of the measured radiation data n = day of the year

14. Solar Radiation Intensity at Earth Surface Solar radiation incident on a surface at earth has three different components: 1. Direct radiation: The solar radiation received from the sun without having been scattered by the atmosphere. 2. Diffuse radiation: Radiation received and remitted in all directions by earth atmosphere: 3. Reflected radiation: Radiation reflected by surrounding surfaces.

15. Total Incident Radiation

16. Solar Radiation – Material Interaction Where

17. Material Optical Properties The Khirchoff’s law In equilibrium: In general

18. Solar Radiation – Material Interaction Opaque Surface: Transparent Surface:

19. Use Solar Energy 1. Solar Thermal Energy: Converts solar radiation in thermal heat energy - Active Solar Heating - Passive Solar Heating - Solar Thermal Engine 2. Solar Photovoltaics Converts solar radiation directly into electricity

20. Solar Collector • Flat Plate Collector - Glazed and unglazed - Liquid-based - Air-based • Evacuated Tube • Concentrating - Parabolic trough

21. Flat Plate Solar Collector Used for moderate temperature up to 100 C Uses both direct and diffuse radiation Normally do not need tracking of sun Use: water heating, building heating and air-conditioning, industrial process heating. Advantage: Mechanically simple

22. Concentrating Solar Collector • Parabolic Trough - Line focus type Focuses the sun on to a pipe running down the center of trough. - Can produce temperature upto 150 – 200 C - Used to produce steam for producing electricity - Trough can be pivoted to track the sun

23. Concentrating Solar Collector • Parabolic Dish Concentrator - Point focus type Focuses the sun on to the heat engine located at the center of the dish. - Can produce very high temperature 700-1000C - Used to produce vapor for producing electricity - Dish can be pivoted to track the sun

24. Active Solar Heating Uses solar collector mounted on roof top to gather solar radiation Low temperature range: 100 C Applications involves domestic hot water or swimming pool heating

25. Description of a Project Oriented Learning Module A typical solar projects are discussed in the following section. The objective is to understand some of the basic steps to be followed.

26. SOLAR HEATED SWIMMING POOL Swimming pools of most motels in the United States are currently outdoors and heated by gas heaters. It is proposed to use solar energy to heat the pool during the winter time. It is also proposed to have flat plate collectors receive energy from the sun and use the energy to maintain the water at a comfortable temperature year round.

27. Solar Collector Pump Swimming Pool Solar Heated Swimming Pool Option-1: Without Auxiliary Heater and Thermal Storage

28. Auxiliary Heater Solar Collector Swimming Pool Pump Solar Heated Swimming Pool Option-2: With a Auxiliary Heater and without a Thermal Storage

29. Auxiliary Heater Thermal Storage Solar Collector Swimming Pool Pump Solar Heated Swimming Pool Option-3: With a Auxiliary Heater and a Thermal Storage

30. Known Data • 1. Geographical Location: • Santa Barbara, CA • 2. The Pool Dimension • 12m long x 8m wide with water • depth that varies in the lengthwise • direction from 0.8m to 3.0m

31. To be Designed , Selected or Determined • Design Conditions - A comfortable water temperature for the indoor pool and indoor air condition - Design outdoor conditions • A solar water heating system with or without thermal storage • A system with or without a auxiliary gas or electric heater

32. Determine size and type of solar collector • Decide placement of these collectors, their location, and orientation • Estimate the total cost of the system including initial, operating and maintenance • Compare these costs to those associated with the use of a natural gas water heating system

33. A Solar-driven Irrigation Pump A solar-energy driven irrigation pump operating on a solar driven heat engine is to be analyzed and designed.

34. Basic Theory The solar collector collects a fraction of incident radiation and transfer to the circulating working fluid, producing saturated vapor and heating the working fluid.

35. To be Designed , Selected or Determined Select: Location, time and month of the year Determine: Incident solar radiation based on the selected location, day and month of the year. For Example: Over 0< t < 10

36. Selection and Design of Solar Collector Type:Flat Plate Transmittance – Absorptance Product: Collector removal factor: = 0.024 Overall loss coefficient: Collector efficiency: Where = Fluid temperature at inlet to the collector = Ambient air temperature = Incident solar radiation

37. Perform the analysis for the base case of and assuming a pumping rate of 10 GPM at the mid noon. • Determine the collector area needed to meet this demand. • Plot the irrigation pump flow rate during the daylight hours. • Estimate the total water pumped in a day

38. If the pumping rate is kept constant at 10 GPM by using an auxiliary after-heater and maintaining the (saturated vapor) temperature constant at inlet to the turbine, determine the auxiliary energy needed at the after-heater. • Repeat steps 1-2 with varying range of and . Summarize your results for (a) solar collector area needed, (b) total pumping rate and (c) total auxiliary energy needed.