Practice Exam Questions for Objective 4. Solar Energy ... · PDF filePyrheliometer value - Pyranometer value b. ... Q2. The dashed line at A in the diagram above represents the a

Practice Exam Questions for Objective 4. Solar Energy Fundamentals (Text Ch 1 pp 19 -20, Ch 2 pp 26 -47, Ch 3 pp 68 - 77 and Ch 5 pp 139-140)

Suggested Percentage Time Allotment: 10% (Covered in ETC 288 10%)

Objective 4.1 Define basic terminology, including solar radiation, solar irradiance, solar irradiation, solar insolation, solar constant, air mass, ecliptic plane, equatorial plane, pyranometer, solar declination, solstice, equinox, solar time, solar altitude angle, solar azimuth angle, solar window, array tilt angle, array azimuth angle, and solar incidence angle. Critical Chapter 2:pp 26-47

Q1. The power of electro magnetic radiation striking a given area of surface is a Radiance. b. Radiation c. Irradiance. c. Solar constant

Q2. Which of three is not a component of the Global irradiance?

a. Direct Irradiance b. Solar Irradiation c. Diffuse Irradiance

Q3. A measure of solar radiation (irradiance) usually in average w/m2 received on a given surface area in a given time.

a. Insolation b. Insulation c. Radiance. d. Radiation

Q4. The amount of solar energy that falls on the surface over time This is the ENERGY density of solar radiation. It is measured in kilowatt-hours/square meter/day

a. Solar Irradiance b. Solar Irradiation c. Solar constant

Q5. Diffuse Irradiance can be calculated by a. Pyrheliometer value - Pyranometer value b. Reference cell value - Pyranometer value c. Pyranometer value - Pyrheliometer value

Q. 6. The amount of incoming solar radiation reaching the top of the atmosphere per unit area at a distance of one astronomical unit (AU)solar constant, given as 1366 W/m2 defines the

a. Solar constant b. Astronomical Unit c. Ecliptic plane d. Equatorial plane

.Q. 7. The plane of earth's orbit around the sun defines the


Q.8 The plane extending out of the Earths' equator to space - how we measure the tilt of axis with respect to ecliptic plane is the definition of the


Q9. The average distance form the earth to the sun approximately 93 million miles or 150 million kilometers is call ed the


Q10. The equinoxes - the first day of spring and autumn are approximately 3/21 and 9/21.

Q11. The solstices - first day of winter is approximately 12/21 and summer approximately 6/21.

Q12. The angle between the equatorial plane and the rays of the sun is the

a. Solar declination b. Solar Elevation Angle c. Angle of Incidence

Q.13. The relative thickness of the path of solar radiation as compared to a vertical path defines through the atmosphere the

a. solar path b. air mass c. astronomical unit

Q14. Given that a Pyrheliometer 100 W/m2 reading at noon time on a partly cloudy day and a Pyranometer is reading 143 W/m2 determine the value of the diffuse irradiance at this locations?

ans. Diffuse = Global - Direct = Pyranometer - Pyrheliometer = 143 W/m2 - 100 W/m2 = 43 W/m2.

Q15. Which of the days would be most likely to have most clouds given the following reading at noon?

a. Pyranometer = 100, Pyrheliometer = 62 b. Pyranometer = 100, Pyrheliometer = 12 - Ans clearly has the greatest % diffusec. Pyranometer = 100, Pyrheliometer = 92

Q16. Which of the days would be most likely to have most clouds given the following reading at noon?

a. Pyranometer = 150, Pyrheliometer = 62 (diffuse = 88 W/m2 - 58.7 % of GHI)b. Pyranometer = 113, Pyrheliometer = 92 (diffuse = 21 W/m2 - 18.6 % of GHI)c. Pyranometer = 125, Pyrheliometer = 12 (diffuse = 113 W/m2 - 90.4 % of GHI) Ans greatest %

Q17. The vertical ray of the sun is over 23.5 S on _____________ Dec 21

0 degrees on _________ Mar 21 and Sep 21

23.5 N on ___________ Dec 21Q18. The three types of irradiance are:

a. Strong, Moderate and Weak c. High, Medium and Low b. Global, Direct and Diffuse d. Universal, Scattered and Local

Q19. If the distance of a lioght source is increased by a factor of 4 its intensity will decrease by a factor of:

a. 4 b. 8 c. 16

Q20. The angle between sun and horizon is called

a. Angle of Incidence b Solar altitude angle c. Array azimuth angled. d. Solar zenith angle e. Array tilt angle

Q21. Angle at which the Sun's rays or insolation strike the Earth's surface is called


Q22. Angle between a point directly overhead and the sun at solar noon.


Q23. The vertical angle between the horizontal and the array surface is called


Q24. The horizontal angle between a reference direction and the direction an array surface faces is the


Q25. For time based upon the position of the sun in the sky.

a. Solar noon is when sun is due south and has the highest Solar Altitude angle for the day. b. Solar noon is when sun is due north and has the highest Solar Altitude angle for the day. c. Solar noon is when sun is due south of the 0 degree meridian.

Q26. The solar window is a. From sunrise to sunset each day b. From March to September in the Northern Hemisphere c. The area of sky between sun path at winter and summer solstice

Q27. The fractional amount of reflected radiation from a surface is called a. Radiation constant b. Albedo c. Reflectivity

Q28. The values of Albedo are from a. 0 for black and 1 for white. b. 1 for black and 0 for white a. 0 for black and 100 for white. b. 100 for black and 0 for white

Q29. Irradiance isa.. measured in sun hours per dayb. measured in wattsc. measured in watts per square meterd. irradiation multiplied by time

Q30. The cause of the seasons

a. is caused by the change in distance from the sun to the earth over the course of the year b. changes based upon your longitude, latitude and time of year c. is caused by the tilt of earth on axis and orbit cause of seasonsMatching Exercised 1. Radiance a. all of the irradiance both direct and diffusei 2. Radiation b. measures global (all) solar irradiance

k 3. Solar radiation c. a unit of solar radiation; equal to one calorie per square centimeter. m 4. Irradiance d. indicates how much power is emittedp 5. Insolation e. Plane of earth's orbit around the sunn 6. Solar irradiance f. amount of incoming solar radiation reaching the top of the

atmosphere per unit area at a distance of one astronomical unit (AU)solar constant, given as 1366 W/m2

a 7. Global Irradiance g. only measures direct irradiancel 8. Direct Irradiance h. irradiance that has been scattered by clouds, dust, haze, etc.,h 9. Diffuse Irradiance i. the energy and process in which energy is generated at a source as an

E/M wave and travels through a medium or through spaceb 10. Pyranometer j. the amount of solar energy that falls on the surface over time This is

the ENERGY density of solar radiation. It is measured in kilowatt-hours/square meter/day

g 11. Pyrheliometer k. general term for the electromagnetic radiation emitted by the sunj 12. Solar Irradiation l. irradiance directly from the sunc 13. Langley m. the rate of light energy striking a given area of surface in a given

amount of timef 14. Solar constant n. Same as insolation a measure of solar radiation energy usually in

w/m2 in received on a given surface area in a given time.q 15. Astronomical Unit o. the relative thickness of the path of solar radiation as compared to a

vertical path.e 16. Ecliptic plane p. a measure of solar radiation energy usually in w/m2 in received on a

given surface area in a given time.u 17 Equatorial plane q. average distance from the earth to the sun approximately 93 million

miles or 150 million kilometers.t 18. Equinox r. first day of winter approximately 12/21 and summer 6/21r. 19. Solstice s. angle between the equatorial plane and the rays of the sun. It is the

latitude where Sun is directly overhead (vertical) at solar noon. s. 20. Solar declination t. the first day of spring and autumn approximately 3/21 and summer

9/21o 21. air mass, u. the plane extending out of the Earth's equator to space - how we

measure the tilt of axis with respect to ecliptic plane.y 22. Solar altitude angle v. Time based upon the position of the sun in the sky. Solar noon is

when sun is due south and has the highest Solar Altitude angle for the day.

x 23. Solar incidence angle (angle of incidence)

w. The vertical angle between the horizontal and the array surface

z 24. Solar zenith angle x. Angle at which the Sun's rays or insolation strike the Earth's surface. Equal in value to the Solar zenith angle for a flat surface.

w 25. Array tilt angle y. angle between sun and horizon (also called the solar or sun elevation angle)

bb 26. Array azimuth angle z. Angle between a point directly overhead and the sun at solar noon.v 27. Solar time aa. Area of sky between sun path at winter and summer solsticeaa 28. Solar window bb. The horizontal angle between a reference direction and the direction

an array surface facescc 29. Albedo cc. The fractional amount of reflected radiation from a surface. It is

defined as the ratio of reflected radiation from the surface to incident radiation upon it. ) ranged from 0 for black and 1 for white. Can be expressed as a percent.

Objective 4.2 Diagram the sun’s apparent movement across the sky over any given day and over an entire year at any given latitude, and define the solar window. Important Chapter 2:pp 43-46

Q1. The dashed lines A, B and C in the diagram above represents the a. Equatorial plane b. Sun path c. Ecliptic plane

Q2. The dashed line at A in the diagram above represents the a. Sun path on the summer solstice b. Sun path on the first day of spring c. Sun path on the first day of fall

Q3. The difference between the dashed lines at A and B in the diagram above represents the a. Solar day b. Equinoxes c. Solar window

Q4. In the northern hemisphere above 23.5 N, when the sun sets on summer solstice, it is the farthest __________ that it will ever a. North OK b. South c. East d. West

Q5. Equinox a. Is the same day everywhere in the world at the same time b. Means the sun is directly overhead at the tropic of Capricorn c. Is always on the 21st

d. Happens once a year

Q6. In St. Paul MN, the sun is upa. the same amount of hours as there are sun hours per dayb. less than the amount of sun hours per day at the equinoxc. more than the number of sun hours per day part of the timed. none of the above

Q7. Angles A, B and C in the diagram above all represent

a. Zenith Angels

b. Declination Angles

c. Solar Altitude Angles

Q8. This is diagrams shows the vertical ray of the sun at what latitude?

a. 23.5 N b. Equator c. 30 N d. 30 S

Q9. The date of this above diagram must be about a. Dec 21 b. Mar 21 c. Jul 21 d. Sep 21

Q10. The declination angle on this date at 43.5 N, 30 N, 0, and 30 S are

at 30 N is 6.5

at 0 deg is 23.5

at 30 S is 53.5

at 43.5 N is 20

Objective 4.3 For given dates, times and locations, identify the sun’s position using sun path diagrams, and determine when direct solar radiation strikes the north, east, south and west walls and horizontal surfaces of a building. Important Chapter 2:pp 43-45 and 3: 71-77

Using the SolarPathfinder sun diagram above answer the following:

Q1. The curved lines that go from left to right as indicated by the arrow "A" represents the _sun path__

Q2. The small number indicated by the "B" arrow represents the % clear sky irradiance for 30 minutes

Q3. The direction a point C is south

Q4. The up down curved lines the arrow "D" points to represent the solar time

Q5. The magnetic declination of this locations is about a. +10 b. 0 c. -10 d. can not be determined

B

D

A

C

Using the sun diagram above answer the following:

Q6. The time at point "A" is ___1 PM__________ for the months ____Apr____ and _____Oct ______

Q7. The tree superimposed on the sun diagram will cause shading for this location during the morning/afternoon for the months of ___Aug to Sep___

Q8. The further north you are, the better it is toa. wash your arrayb. increase your tilt anglec. decrease your tilt angled. decrease your azimuth

Q9. The cause of the season is the 23.5 degree tilts of the earth axis of the earth and the orbit of the earth around the sun.

Q10. The Sun Altitude Angle a. has a significant effect on the irradiance reaching a solar array b. has more solar energy reaches array when it is low c. Is relatively constant both seasonally and diurnally (daily) changes

A

Q11. One Earth orbit around the Sun takes

a. 24 hours b. 30.5 days c. 365.25 days

Q12. One =Earth rotation takes

a. 24 hours b. 30.5 days c. 365.25 days

Q13. The Earth is closer to the Sun during

a. July b. Sep c. Jan d. Mar

Q14. Solar time is a. the same for each 15 degrees of latitude b. the same everywhere on earth c. based upon the position of the sun in the sky.

Q15. Solar noon is when sun is due south and has the highest Solar Altitude angle for the day.

Q16. The solar window is area of sky between sun path at winter and summer solstice

Q17. Angle A in the diagram above is called a. Zenith Angle b. Solar Altitude Angle c. Angle of Incidence

Q17. Angle B in the diagram above is called a. Zenith Angle b. Solar Altitude Angle c. Angle of Incidence

Q17. Angle C in the diagram above is called a. Zenith Angle b. Solar Altitude Angle c. Angle of Incidence

BA

C

Objective 4.4 Differentiate between solar irradiance (power), solar irradiation (energy), and understand the meaning of the terms peak sun, peak sun hours, and insolation. Critical Chapter 2:pp 28-34

Q1. The power of solar radiation striking a given area of surface is a Solar radiance. b. Solar radiation c. Solar irradiance. d. Solar constant

Q2. The amount of solar energy that falls on the surface over time

a. Solar irradiance b. Solar irradiation c. Solar constantQ3. Solar irradiance measures the power of solar radiation for a given surface area. Solar irradiation is the measure of the rate of solar energy over a period of timeQ4. A KW is a unit of power. A KW-Hour is a unit of energy.

Q5. Solar insolation is a. a measure of solar radiation energy received on a given surface area in a given time. b. It is commonly expressed as average irradiance in watts per square meter (W/m2) or kilowatt-hours per square meter per day (kW·h/(m2·day)) (or hours/day). c. In the case of photovoltaics it is commonly measured as kWh/(kWp·y) (kilowatt hours per year per kilowatt peak rating). d. a, b and c are all true.

Q6. Irradiance proportionally effects:a. Amperage b. Voltagec. Air massd. NOCT (Nominal Operating Cell Temperature)

Q7. An estimate of the maximum terrestrial solar irradiance around solar noon at sea level and has been a generally accepted value of 1000 w/m2 is called

a. the solar constant b. a peak sun hour c. solar maximum

Q8. The number of peak sun hour is the equivalent number of hours per day when solar irradiance averages

a. 1000 KW/ m2 b. 1000 W/m2

c. 1000 W-hours/m2

Q9. A day where 6.3 KW/m2 or irradiance hit the ground during a day has a. 6.3 peak sun hours b. 63 peak sun hours c. 630 peak sun hours d. 6300 peak sun hours

Objective 4.5 Identify factors that reduce or enhance the amount of solar energy collected by a PV array. Important Chapter 2:pp 30-36, 40-48 Chapter 3:pp 69-77

Q1. Pick the factors that can significantly reduce or enhance the amount of solar energy collected by a PV array

a. Solar Altitude Angle b. Solar Constant c. Astronomical Unit d. Array Angle

e. Ecliptic Plane f Solar Azimuth Angle g. Atmospheric conditions h. Phase of moon

i. Shading j. Temperature k. Surface color and Texture

Q2. The typically optimum array angle for the mid-latitudes is between

a. 20 - 25˚ b. 30 - 35˚ c. 40 - 45˚ d. 50 - 55˚

Q3. The Solar Azimuth Angle

a. is a measure of the orientation of the array from True Southb. is a measure of the orientation of the array from the vertical ray.c. is a measure of the orientation of the array from Magnetic South

Q4. Of the atmospheric conditions: Clouds, Haze, Dust, and Humidity (water vapor) which has the most impact on the irradiance that reaches the surface?

a. Clouds, b. Haze, c. Dust, d. Humidity (water vapor)

Q5. The warmer/colder the temperature the more electrical power an array can generate.

Q6. Shading will cause:

a. degradation of array proportion that is proportional to the fraction of the array shaded b. disproportionately greater degradation of array performance than the fraction of the array shaded c. some degradation of array performance, but typically les than 1/2 the fractional value of the array shaded.Q7. Surface color and texture of the array would have:

a. no impact on array performanceb. some effect on the array performance

c. is only important for solar thermal technologies

Q8. The theoretical Max Irradiance based upon clear sky is a function of latitude____b

Q9. The actual Max Irradiance is a function of everything but

a. Cloudiness b. Latitude c. Longitude d Shading e. Roof pitch f. orientation from south

Q 9. The further north you are, the better it is to

a. wash your arrayb. increase your tilt anglec. decrease your tilt angled. decrease your azimuth

Q10. The critical design month is the worst case scenario where the load and the ______are used to size the PV system

a. peak demandb. insolation datac. total power demandd. duty cycle

Q11. If you had modules facing directly north and oriented vertically (90 degrees tilt) wouldthere be a time of the year when the sun rays would hit the panels at 38 degrees latitude?If so, how many months of the year would the sun hit the north facing modules?

a. 0 monthsb. 3 monthsc. 6 monthsd. 9 months

Q12. If you combing solar and wind energy in an off-grid system, it isa. bimodalb. indirectc. sinusoidald. hybrid

Objective 4.6 Demonstrate the use of a standard compass and determine true geographic south from magnetic south at any location given a magnetic declination map. Important Chapter 3:pp 68-70

Q1. According to the map abovea. the sun rises in the east and sets in the westb. there are poles everywherec. in some places, magnetic and solar north are differentd. the longitudinal continuum transects the sun charts cloud correction pattern

Q2. In California, magnetic North is pointing?a. more south than true northb. true northc. more west than true northd. more east than true north

Objective 4.7 Quantify the effects of changing orientation (azimuth and tilt angle) on the amount of solar energy received on an array surface at any given location using solar energy databases and computer software tools. Important Chapter 2:pp 30-36, 40-48 Chapter 3:pp 68

Q1. Look at the “A” and the “X” in the chart above. What is:

a. the annual value of solar irradiance at A 900 KW-h/m2

b. the max annual radiance what is the % of max at A using 1050 KW-h/m2 as the max % max = (900/1050) x 100% = 86% c. the annual value of solar irradiance at X is 1025 KW-h/m2

b. the max annual radiance what is the % of max at A using 1050 KW-h/m2 as the max % max = (1025/1050) x 100% = 98% Q2. What is the approximate percent change on the amount of solar irradiance if orientation (azimuth and tilt angle) is moved from the “A” position to the “X” position?

a. 6 %b. 12%c. 18 %d. 24 %e. all of the above

Q3. In the above diagram what are angel A and B called?

Ans. A = Tilt angle. B = Azimuth angle

Q4. Array orientation is defined by the angles of

a. incidence angle and tilt angleb. tilt angle and azimuth anglec. azimuth and solar window angled. zenith angel and tilt angle

Objective 4.8 Understand the consequences of array shading and best practices for minimizing shading and preserving array output. Critical Ch 3:pp 69-67, Ch 5:pp 130-140

Q1. PV arrays are more or less sensitive to shading than thermal solar collectors ?

a. moreb. lessc. depends

Q2. In the worst cases, even a 10% shading on a PV array can cause

a. a small loss of outputb. the loss of no outputc. the loss of most output

Q3. In best practices, PV arrays should be installed in a location with an unobstructed solar window from

a. 8 AM to 3 PM solar time throughout the summer b. 9 AM to 3 PM solar time throughout the winter c. 9 AM to 3 PM solar time throughout the summer d. 7 AM to 4 PM solar time throughout the winter

Q4. During summer in the northern latitudes, the sun can sometimes be in the northern part of the sky, which can cause shading from obstructions immediately_________ of an array.

a. southb. eastc. westd. north

Objective 4.9 Demonstrate the use of equipment and software tools to evaluate solar window obstructions and shading at given locations, and quantify the reduction in solar energy received. Important Chapter 3:pp 69 - 77

Q1. According to the sun path diagram abovea. the sun sets at 4pm sometimesb. the sun rises on the horizon in the summer c. solar noon is the same as noon local timed. the solar pathfinder was not level

Q2. In the location above, on a clear day, the sun will shine in February fora. less than 3.5 hoursb. 4.5 hoursc. 5 hours and 45 min d. more than 6 hours

Q3. In the sun path diagram above, for a grid tied system, you would want to tilt yourmodules____________ for greatest annual net solar energy

a. to an angle equal to the latitude from the horizontalb. to an altitude angle greater than the latitude and due southc. to an azimuth that is east of south and an altitude angle less than latitude d. to an altitude angle that is less than the latitude to maximize sun on short winter days

Objective 4.10 Identify rules of thumb and spacing distances required to avoid inter-row shading from adjacent sawtooth rack mounted arrays at specified locations between 9 am and 3 pm solar time throughout the year. Important Chapter 3:pp 72 – 77

Q1. A simple rule for minimum spacing between "saw tooth" PV rows is to allow a space equal to ____________ the height of the top of the adjacent module.

a. two times b. two and one half timesc. three times d. three and one half timese. four times

Q2. In the diagram how far apart should the modules be using the simple rule for minimum spacing between "saw tooth" PV rows?

a. 3 b. 6. c. 9 d. 12

Q3. For the same diagram above what would be the minimum spacing for a between "saw tooth" PV rows if the module faces due south and α = 10 degrees using more exact equation below

costan

d h ψα

= ×

d = minimum row spacingh = row height in feetψ = azimuth angle between solar azimuth angle and azimuth angle (0 for array facing due south)α = solar altitude angle in degrees

cos cos 0 13 3 3 (5.67) 17tan tan10 .176

d h ft ft ft ftψα

= × = × = × = =o

o

Objective 4.11 Define the concepts of global, direct, diffuse and albedo solar radiation, and the effects on flat-plate and concentrating solar collectors. Important Chapter 1:pp 19 - 20, Chapter 2: pp 30 - 33

Q1. Total global solar radiation, which is all of the solar radiation reaching Earth's surface, is the sum of

a. direct and diffuse radiation b. all the radiation in the sunc. diffuse and albedo radiationd. both a and b

Q2. Concentrating solar collectors more effectively use ______________ than flat plate collectors?

a. Direct radiationb. Diffuse radiation c. Global radiation

Q3. Flat plate PV collectors more effectively use ______________ than concentrating thermal solar collectors?

a. Direct radiationb. Diffuse radiation c. Visible radiation

Q4. Albedo radiation is

a. greater for darker objectsb. a function of the array temperaturec. radiation that is reflected form a surface

Objective 4.12 Identity the instruments and procedures for measuring solar power and solar energy. Important Chapter 2: pp 36 - 38

Q1. What are the three primary instruments for measuring solar irradiance (power)?

ANS: Pyranometer, Pyrheliometer and Reference Cell

Q2. What are the three primary instruments used for?ANS:

Pyranometer: Measure Total IrradiancePyrheliometer: Measure Direct IrradianceReference Cell: Encapsulated PV cell that outputs a known amount of electrical per unit

of solar irradiance. Used for calibration of systemsQ3. How is diffuse irradiance calculated?

a. Pyrheliometer value - Pyranometer value b. Reference cell value - Pyranometer value c. Pyranometer value - Pyrheliometer value

Q4. What is the name of instrument A, B and C?

A = Pyranometer, B = Reference cell, C = Pyrheliometer

A.A.

B.B.C.C.

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Practice Exam Questions for Objective 4. Solar Energy ... · PDF filePyrheliometer value - Pyranometer value b. ... Q2. The dashed line at A in the diagram above represents the a