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Longitude

Longitude of the station: W = West, E = East Degrees Minutes

38

056-059

Elevation

Elevation of station in meters above sea level

162

had observations, measurements, or estimates made at daily, instead of hourly, intervals. Consequently, the data values for broadband aerosol optical depth, snow depth, and days since last snowfall represent the values available for the day indicated.

With the exception of extraterrestrial horizontal and extraterrestrial direct radiation, the two field positions immediately following the data value provide source and uncertainty flags both to indicate whether the data were measured, modeled, or missing and to provide an estimate of the uncertainty of the data. Source and uncertainty flags for extraterrestrial horizontal and extraterrestrial direct radiation are not provided, because these elements were calculated using equations considered to give exact values. Explanation of the uncertainty flags for the other quantities is given in Marion and Urban (1995).

A sample of the Nicosia TMY-2 file, showing the data for the first days of January, including the header elements, can be seen in Figure 2.32 (Kalogirou, 2003). It should be noted that the format of the TMY-2 for the Energy Plus program is a little different than the one shown in Figure 2.32 since it includes after the header design conditions, extreme periods and holidays, and daylight saving data.

Field position

Element

Value

Definition

002-009

Local standard time

002-003

Year

2-digit

Year

004-005

Month

1-12

Month

006-007

Day

1-31

Day of month

008-009

Hour

1-24

Hour of day in local standard time

010-013

Extraterrestrial horizontal

0-1415

Amount of solar radiation in Wh/m2 received on a horizontal surface at the

radiation

top of the atmosphere

014-017

Extraterrestrial direct normal

0-1415

Amount of solar radiation in Wh/m2 received on a surface normal to the

radiation

sun at the top of the atmosphere

018-023

Global horizontal radiation

Total amount of direct and diffuse solar radiation in Wh/m2 received on a

horizontal surface

018-021

Data value

0-1200

022

Flag for data source

A-H, ?

023

Flag for data uncertainty

0-9

024-029

Direct normal radiation

Amount of solar radiation in Wh/m2 received within a 5.7° field of view

centered on the sun

024-027

Data value

0-1100

028

Flag for data source

A-H, ?

029

Flag for data uncertainty

0-9

(Continued)

Field position

Element

Value

Definition

030-035

Diffuse horizontal radiation

Amount of solar radiation in Wh/m2 received from the sky (excluding the

solar disk) on a horizontal surface

030-033

Data value

0-700

034

Flag for data source

A-H, ?

035

Flag for data uncertainty

0-9

036-041

Global horiz. illuminance

Average total amount of direct and diffuse illuminance in hundreds of lux

received on a horizontal surface

036-039

Data value

0-1300

0 to 1300 = 0 to 130,000 lux

040

Flag for data source

I, ?

041

Flag for data uncertainty

0-9

042-047

Direct normal illuminance

Average amount of direct normal illuminance in hundreds of lux received

within a 5.7° field of view centered on the sun

042-045

Data value

0-1100

0 to 1100 = 0 to 110,000 lux

046

Flag for data source

I, ?

047

Flag for data uncertainty

0-9

048-053

Diffuse horiz. illuminance

Average amount of illuminance in hundreds of lux received from the sky

(excluding the solar disk) on a horizontal surface

048-051

Data value

0-800

0 to 800 = 0 to 80,000 lux

052

Flag for data source

I, ?

053

Flag for data uncertainty

0-9

054-059

Zenith luminance

Average amount of luminance at the sky's zenith in tens of Cd/m2

054-057

Data value

0-7000

0 to 7000 = 0 to 70,000 Cd/m2

058

Flag for data source

I, ?

059

Flag for data uncertainty

0-9

060-063

Total sky cover

Amount of sky dome in tenths covered by clouds or obscuring phenomena at the hour indicated

060-061

Data value

0-10

062

Flag for data source

A-F

063

Flag for data uncertainty

0-9

064-067

Opaque sky cover

Amount of sky dome in tenths covered by clouds or obscuring phenomena that prevent observing the sky or higher cloud layers at the hour indicated

064-065

Data value

0-10

066

Flag for data source

A-F

067

Flag for data uncertainty

0-9

068-073

Dry bulb temperature

Dry bulb temperature in tenths of a degree Centigrade at the hour indicated.

068-071

Data value

-500 to 500

-500 to 500 = -50.0 to 50.0°C

072

Flag for data source

A-F

073

Flag for data uncertainty

0-9

(Continued) 0

Field position

Element

Value

Definition

074-079

Dew point temperature

Dew point temperature in tenths of a degree Centigrade at the hour

indicated.

074-077

Data value

-600 to 300

-600 to 300 = -60.0 to 30.0°C

078

Flag for data source

A-F

079

Flag for data uncertainty

0-9

080-084

Relative humidity

Relative humidity in percent at the hour indicated

080-082

Data value

0-100

083

Flag for data source

A-F

084

Flag for data uncertainty

0-9

085-090

Atmospheric pressure

Atmospheric pressure at station in mbar at the hour indicated

085-088

Data value

700-1100

089

Flag for data source

A-F

090

Flag for data uncertainty

0-9

091-095

Wind direction

Wind direction in degrees at the hour indicated. (N = 0 or 360,

E = 90, S = 180, W = 270). For calm winds, wind direction equals

zero.

091-093

Data value

0-360

094

Flag for data source

A-F

095

Flag for data uncertainty

0-9

096-

-100

Wind speed

Wind speed in tenths of meters per second at the hour indicated.

096-

-98

Data value

0-400

0 to 400 = 0 to 40.0 m/s

99

Flag for data source

A-F

100

Flag for data uncertainty

0-9

101-

-106

Visibility

Horizontal visibility in tenths of kilometers at the hour indicated.

101-

-104

Data value

0-1609

7777 = unlimited visibility

105

Flag for data source

A-F, ?

0 to 1609 = 0.0 to 160.9 km

106

Flag for data uncertainty

0-9

9999 = missing data

107-

-113

Ceiling height

Ceiling height in meters at the hour indicated.

107-

111

Data value

0-30450

77777 = unlimited ceiling height

112

Flag for data source

A-F, ?

88888 = cirroform

113

Flag for data uncertainty

0-9

99999 = missing data

114-

-123

Present weather

Present weather conditions denoted by a 10-digit number.

124-

128

Precipitable water

Precipitation water in millimeters at the hour indicated

124-

-126

Data value

0-100

127

Flag for data source

A-F

128

Flag for data uncertainty

0-9

Field position

Element

Value

Definition

129-133

Aerosol optical depth

Broadband aerosol optical depth (broadband turbidity) in thousandths on

the day indicated.

129-131

Data value

0-240

0 to 240 = 0.0 to 0.240

132

Flag for data source

A-F

133

Flag for data uncertainty

0-9

134-138

Snow depth

Snow depth in centimeters on the day indicated.

134-136

Data value

0-150

999 = missing data

137

Flag for data source

A-F, ?

138

Flag for data uncertainty

0-9

139-142

Days since last snowfall

Number of days since last snowfall.

139-140

Data value

0-88

88 = 88 or greater days

141

Flag for data source

A-F, ?

99 = missing data

142

Flag for data uncertainty

0-9

17609 NICOSIA 2 N 34 53 E 33 38 162

86 1 1 1 01415 0?9 0?9 0?9 0?9 0?9 0?9 0?9 5B8 2B8 75C9

86 1 1 2 01415 0?9 0?9 0?9 0?9 0?9 0?9 0?9 4B8 2B8 75C9

86 1 1 3 01415 0?9 0?9 0?9 0?9 0?9 0?9 0?9 4A7 1A7 70C9

86 1 1 4 01415 0?9 0?9 0?9 0?9 0?9 0?9 0?9 4B8 1B8 70C9

86 1 1 5 01415 0?9 0?9 0?9 0?9 0?9 0?9 0?9 3B8 1B8 75C9

86 1 1 6 01415 1?9 0?9 0?9 0?9 0?9 0?9 0?9 3B8 1A7 75C9

86 1 1 7 01415 19H9 0H9 0H9 0I9 0I9 0I9 0I9 3B8 2B8 90B8

86 1 1 8 1401415 70H9 0H9 70H9 52I9 53I9 47I9 68I9 3B8 2B8 90B8

FIGURE 2.32 Format of TMY-2 file.

EXERCISES

2.1 As an assignment using a spreadsheet program and the relations presented in this chapter, try to create a program that estimates all solar angles according to the latitude, day of year, hour, and slope of surface.

2.2 As an assignment using a spreadsheet program and the relations presented in this chapter, try to create a program that estimates all solar angles according to the latitude, day of year, and slope of surface for all hours of a day.

2.3 Calculate the solar declination for the spring and fall equinoxes and the summer and winter solstices.

2.4 Calculate the sunrise and sunset times and day length for the spring and fall equinoxes and the summer and winter solstices at 45°N latitude and 35°E longitude.

2.5 Determine the solar altitude and azimuth angles at 10:00 am local time for Rome, Italy, on June 10.

2.6 Calculate the solar zenith and azimuth angles, the sunrise and sunset times, and the day length for Cairo, Egypt, at 10:30 am solar time on April 10.

2.7 Calculate the sunrise and sunset times and altitude and azimuth angles for London, England, on March 15 and September 15 at 10:00 am and 3:30 pm solar times.

2.8 What is the solar time in Denver, Colorado, on June 10 at 10:00 am Mountain Standard Time?

2.9 A flat-plate collector in Nicosia, Cyprus, is tilted at 40° from horizontal and pointed 10° east of south. Calculate the solar incidence angle on the collector at 10:30 am and 2:30 pm solar times on March 10 and September 10.

2.10 A vertical surface in Athens, Greece, faces 15° west of due south. Calculate the solar incidence angle at 10:00 am and 3:00 pm solar times on January 15 and November 10.

2.11 By using the sun path diagram, find the solar altitude and azimuth angles for Athens, Greece, on January 20 at 10:00 am.

2.12 Two rows of 6 m wide by 2 m high flat-plate collector arrays tilted at 40° are facing due south. If these collectors are located in 35°N latitude, using the sun path diagram find the months of the year and the hours of day at which the front row will cast a shadow on the second row when the distance between the rows is 3 m. What should be the distance so there will be no shading?

65C9 94C91021C9120*0 10B8 233B877777"09999999999 0"0 70E8 0"088"0

65C9 94C91021C9120*0 10B8 217B877777"09999999999 0"0 70E8 0"088"0

59C9 93C91021C9120*0 20B8 333B822000"09999999999 0"0 70E8 0"088"0

60C9 92C91021C9120*0 10B8 4 67B822000"09999999999 0"0 70E8 0"088"0

65C8 89E81021B8120*0 10B8 600B822000"09999999999 0"0 70E8 0"088"0

69C8 87E81021B8120*0 10B8 600B822000*09999999999 0*0 70E8 0*088*0

84C8 79E81021B8 80*0 20B8 533B822000*09999999999 0*0 70E8 0*088*0

2.13 Find the blackbody spectral emissive power at X = 8 |m for a source at 400 K, 1000 K, and 6000 K.

2.14 Assuming that the sun is a blackbody at 5777 K, at what wavelength does the maximum monochromatic emissive power occur? What fraction of energy from this source is in the visible part of the spectrum in the range 0.38-0.78 |im?

2.15 What percentage of blackbody radiation for a source at 323 K is in the wavelength region 6-15 |im?

2.16 A 2 mm thick glass sheet has a refraction index of 1.526 and an extinction coefficient of 0.2 cm-1. Calculate the reflectivity, transmissivity, and absorptivity of the glass sheet at 0°, 20°, 40°, and 60° incidence angles.

2.17 A flat-plate collector has an outer glass cover of 4 mm thick K = 23 m-1 and refractive index of 1.526, and a tedlar inner cover with refractive index of 1.45. Calculate the reflectivity, transmissivity, and absorptivity of the glass sheet at a 40° incidence angle by considering tedlar to be of a very small thickness; i.e., absorption within the material can be neglected.

2.18 The glass plate of a solar greenhouse has a transmissivity of 0.90 for wavelengths between 0.32 and 2.8 |im and is completely opaque at shorter and longer wavelengths. If the sun is a blackbody radiating energy to the earth's surface at an effective temperature of 5770 K and the interior of the greenhouse is at 300 K, calculate the percent of incident solar radiation transmitted through the glass and the percent of thermal radiation emitted by the interior objects that is transmitted out.

2.19 A 30 m2 flat plate solar collector is absorbing radiation at a rate of 900 W/m2. The environment temperature is 25°C and the collector emissivity is 0.85. Neglecting conduction and convection losses, calculate the equilibrium temperature of the collector and the net radiation exchange with the surroundings.

2.20 Two large parallel plates are maintained at 500 K and 350 K, respectively. The hotter plate has an emissivity of 0.6 and the colder one 0.3. Calculate the net radiation heat transfer between the plates.

2.21 Find the direct normal and horizontal extraterrestrial radiation at 2:00 pm solar time on February 21 for 40°N latitude and the total solar radiation on an extraterrestrial horizontal surface for the day.

2.22 Estimate the average hourly diffuse and total solar radiation incident on a horizontal surface for Rome, Italy, on March 10 at 10:00 am and 1:00 pm solar times if the monthly average daily total radiation is 18.1 MJ/m2.

2.23 Calculate the beam and total radiation tilt factors and the beam and total radiation incident on a surface tilted at 45° toward the equator one hour after local solar noon on April 15. The surface is located at 40°N latitude and the ground reflectance is 0.25. For that day, the beam radiation at normal incidence is GB = 710 W/m2 and diffuse radiation on the horizontal is GD = 250 W/m2.

2.24 For a south-facing surface located at 45°N latitude and tilted at 30° from the horizontal, calculate the hourly values of the beam radiation tilt factor on September 10.

2.25 A collector located in Berlin, Germany is tilted at 50° and receives a monthly average daily total radiation H equal to 17 MJ/m2-day. Determine the monthly mean beam and total radiation tilt factors for October for an area where the ground reflectance is 0.2. Also, estimate the monthly average daily total solar radiation on the surface.

REFERENCES

ASHRAE, 1975. Procedure for Determining Heating and Cooling Loads for Computerizing Energy Calculations. ASHRAE, Atlanta.

ASHRAE, 2007. Handbook of HVAC Applications. ASHRAE, Atlanta.

Collares-Pereira, M., Rabl, A., 1979. The average distribution of solar radiation—

Correlations between diffuse and hemispherical and between daily and hourly insolation values. Solar Energy 22 (2), 155-164.

Duffie, J.A., Beckman, W.A., 1991. Solar Engineering of Thermal Processes. John Willey & Sons, New York.

Dunkle, R.V., 1954. Thermal radiation tables and application. ASME Trans. 76, 549.

Erbs, D.G., Klein, S.A., Duffie, J.A., 1982. Estimation of the diffuse radiation fraction four hourly, daily and monthly-average global radiation. Solar Energy 28 (4), 293-302.

Filkenstein, J.M., Schafer, R.E., 1971. Improved goodness of fit tests. Biometrica 58, 641-645.

Garg, H.P., 1982. Treatise on Solar Energy, Vol. 1, Fundamentals of Solar Energy Research. John Wiley & Sons, New York.

Hall, I.J., Prairie, R.R., Anderson, H.E., Boes, E.C., 1978. Generation of typical meteorological years for 26 SOLMET stations. In: Sandia Laboratories Report, SAND 78-1601. Albuquerque, NM.

Hay, J.E., Davies, J.A., 1980. Calculations of the solar radiation incident on an inclined surface. In: Proceedings of the First Canadian Solar Radiation Data Workshop, 59. Ministry of Supply and Services, Canada.

Hottel, H.C., Woertz, B.B., 1942. Evaluation of flat plate solar heat collector. ASME Trans. 64, 91.

Hsieh, J.S., 1986. Solar Energy Engineering. Prentice-Hall, Englewood Cliffs, NJ.

Kalogirou, S., 2003. Generation of typical meteorological year (TMY-2) for Nicosia, Cyprus. Renewable Energy 28 (15), 2317-2334.

Klein, S.A., Beckman, W.A., Duffie, J.A., 1976. A design procedure for solar heating systems. Solar Energy 18, 113-127.

Klucher, T.M., 1979. Evaluation of models to predict insolation on tilted surfaces. Solar Energy 23 (2), 111-114.

Kreith, F., Kreider, J.F., 1978. Principles of Solar Engineering. McGraw-Hill, New York.

Lof, G.O.G., Tybout, R.A., 1972. Model for optimizing solar heating design. ASME paper, 72-WA/SOL-8.

Liu, B.Y.H., Jordan, R.C., 1960. The interrelationship and characteristic distribution of direct, diffuse and total solar radiation. Solar Energy 4 (3), 1-19.

Liu, B.Y.H., Jordan, R.C., 1977. Availability of solar energy for flat plate solar heat collectors. In: Liu, B.Y.H., Jordan, R.C. (Eds.) Application of Solar Energy for Heating and Cooling of Buildings. ASHRAE, Atlanta.

Marion, W., Urban, K., 1995. User's Manual for TMY2s Typical Meteorological Years. National Renewable Energy Laboratory, Colorado.

Meinel, A.B., Meinel, M.P., 1976. Applied Solar Energy—An Introduction. Addison-Wesley, Reading, MA.

Meteonorm, 2009. Maps. Available from: www.meteonorm.com.

Reindl, D.T., Beckman, W.A., Duffie, J.A., 1990a. Diffuse fraction correlations. Solar Energy 45 (1), 1-7.

Reindl, D.T., Beckman, W.A., Duffie, J.A., 1990b. Evaluation of hourly tilted surface radiation models. Solar Energy 45 (1), 9-17.

Solar Spectra, 2007. Air Mass Zero. Available from: http://rredc.nrel. gov/solar/spectra/am0.

Spencer, J.W., 1971. Fourier series representation of the position of the sun. Search 2 (5), 172.

kWh/m2

>1850

1750-1850

1650-1750

1550-1650

1450-1550

1350-1450

1250-1350

1150-1250

1050-1150

950-1050

850-950

<850

Global radiation, annual mean 1981-2000

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Responses

  • rita
    What is the solar time in Denver, Colorado, on June 10 at 10:00 am Mountain Standard Time?
    4 years ago

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