Diffuse solar radiation is measured using a pyranometer positioned under the shadow of a ring. The function of the ring is to block direct solar radiation. However, the ring also blocks a portion of the diffuse solar radiation, and therefore, the diffuse radiation needs corrections. The most well-known assembly in the literature on the shading ring method is the Drumond assembly. This study aims to determine the effectiveness of three methods of correction of diffuse irradiance measured with shadow bands: the LeBaron method, the Battles method, and the Dal Pai method. The Laboratory of Solar Radiometry of Botucatu provided global, direct, and diffuse solar irradiances. The laboratory measures diffuse solar radiation using the Melo–Escobedo–Oliveira (MEO) shading ring method, a different setup compared to Drummond's setup. The period used for the study comprised the years 1996 to 2005. The results showed that LeBaron and Battles correction models with the original coefficients are not suitable for correction of diffuse irradiance in Botucatu. According to MBE (Mean Bias Error) and RMSE (Root Mean Square Error), the statistical indicators, LeBaron and Battles with adjusted coefficients, and Dal Pai correction models are indicated to correct the diffuse irradiance in Botucatu measured under an MEO shading ring. For monthly applications, the LeBaron model with adjusted coefficients is recommended. Although this model is more complex from the operational point of view, it better explains anisotropic effects, especially for the winter months.

1.
Battles
,
F. J.
,
Olmo
,
F. J.
, and
Alados-Arboledas
,
L.
, “
On shadowband correction methods for diffuse irradiance measurements
,”
Sol. Energy
54
(
2
),
105
114
(
1995
).
2.
Codato
,
G.
,
Oliveira
,
A. P.
,
Soares
,
J.
,
Escobedo
,
J. F.
,
Gomes
,
E. N.
, and
Dal Pai
,
A.
, “
Global and diffuse solar irradiances in urban and rural areas in southeast Brazil
,”
Theor. Appl. Climatol.
93
,
57
73
(
2008
).
3.
Dal Pai
,
A.
,
Escobedo
,
J. F.
,
Dal Pai
,
E.
, and
Santos
,
C. M.
, “
Estimation of hourly, daily and monthly mean diffuse radiation based on MEO shadowring correction
,”
Energy Procedia
57
,
1150
1159
(
2014
a).
4.
Dal Pai
,
A.
,
Escobedo
,
J. F.
,
Martins
,
D.
, and
Teramoto
,
E. T.
, “
Analysis of hourly global, direct and diffuse solar radiations attenuation as a function of optical air mass
,”
Energy Procedia
57
,
1060
1069
(
2014
b).
5.
Dal Pai
,
A.
,
Escobedo
,
J. F.
,
Dal Pai
,
E.
,
Oliveira
,
A. P.
,
Soares
,
J. R.
, and
Codato
,
G.
, “
MEO shadowring method for measuring diffuse solar irradiance: Correction based on sky cover
,”
Renewable Energy
99
,
754
763
(
2016
).
6.
Dal Pai
,
A.
,
Dal Pai
,
E.
, and
Escobedo
,
J. F.
, “
Comparison between Lebaron-Perez and Dal Pai-Escobedo correction methods for diffuse irradiance measured by the MEO shadowring method
,” in
Proceedings of ISES Solar World Congress, Abu Dhabi, United Arab Emirates
(
2017
), pp
1423
1433
.
7.
Drummond
,
A. J.
, “
On the measurements of sky radiation
,”
Arch. Meteorol., Geophys. Bioklimatol.
7
,
413
436
(
1956
).
8.
Iqbal
,
M.
,
An Introduction to Solar Radiation
(
Academic Press
,
New York
,
1983
), p.
390
.
9.
Kasten
,
F.
,
Dehne
,
K.
, and
Brettschneider
,
W.
, “
Improvement of measurement of diffuse solar radiation
,”
Solar Radiation Data
, Série F, n.2 (
D. Redel
,
Dordrecht
,
1983
), pp.
221
225
.
10.
Kudish
,
A. I.
and
Evseev
,
E. G.
, “
The assessment of four different correction models applied to the diffuse radiation measured with a shadow ring using global and normal beam radiation measurements for Beer Sheva, Israel
,”
Sol. Energy
82
,
144
156
(
2008
).
11.
LeBaron
,
B. A.
,
Michalsky
,
J. J.
, and
Perez
,
R.
, “
A simple procedure for correcting shadowband data for all sky conditions
,”
Sol. Energy
44
(
5
),
249
256
(
1990
).
12.
Oliveira
,
A. P.
,
Escobedo
,
J. F.
, and
Machado
,
A. J.
, “
A new shadow-ring device for measuring diffuse solar radiation at surface
,”
J. Atmos. Oceanic Technol.
19
,
698
708
(
2002
).
13.
Pollard
,
D. G. E.
and
Langevine
,
L. P.
, “
An anisotropic correction for diffuse irradiance measurements in Guyana
,” in
Proceeding of the 1988 Annual Meeting
, edited by
M. J.
Coleman
(
ASES
, Cambridge,
1988
), pp.
238
243
.
14.
Stanhill
,
G.
, “
Observations of shade-ring correction factors for diffuse sky radiation measurements at the Dead Sea
,”
Q. J. R. Meteorol. Soc.
111
,
1125
1130
(
1985
).
15.
Stone
,
R. J.
, “
Improved statistical procedure for the evaluation of solar radiation estimation models
,”
Sol. Energy
51
(
4
),
289
291
(
1993
).
16.
World Meteorological Organization
,
Guide to Meteorological Instruments and Methods of Observation
(
World Meteorological Organization
,
2008
), p.
716
.
You do not currently have access to this content.