Task 7Bb Report Philippine Renewable Energy Project

8/10/2019 Task 7Bb Report Philippine Renewable Energy Project

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Dave Renn

Pamela Gray-HannRay George

Liz Brady

1. Introduction

Accurate solar resource data is important for the proper sizing and life cycle cost analysisof solar photovoltaic technologies. Knowledge of the spatial distribution of the solar

resource for various tilt angles will allow for more cost effective design and operation ofphotovoltaic systems for meeting small, distributed loads. The goal of this task is to

develop a solar assessment for the Philippines that incorporates and builds upon current

understanding of the spatial distribution of the resource. This assessment provides datathat developers and investors can use to help establish successful business activity in off-

grid solar technologies in the Philippines.

Although solar resource assessments have been conducted for the Philippines, these

generally make use of ground-based measurements of the daily total number of hours of

sunshine duration. The updated assessment provided here combines existing ground

measurement data collected in the Philippines with the output of NRELs ClimatologicalSolar Radiation (CSR) Model. This model converts information on satellite- and surface-

derived cloud cover data collected at a 40-km spatial resolution to estimates of the

monthly average daily total global horizontal solar resource. This spatial resolution isgenerally much higher than the spacing of ground stations, and therefore allows for a

more detailed analysis of the effects of microclimate variability on the solar resource, and

provides a more accurate interpolation of the solar resource between ground stations.


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Puerto Princesa (#618), 1984-1997 (missing: January 1985, April, May 1988).

Tuquegarao (#233), 1975-1997 (missing: Feb., May Dec. 1985, all months for 1986-

1987, Jan. Aug. 1988, Feb. 1991).Catarman (#546), 1970-1986, 1987-1995

Laoag (#223), 1970-1985, 1986-1995 (missing: March, April 1985; May August

1988).Victoria's Milling Corporation (#618c), 1971-1982, 1983-1995 (missing: Sept., Oct.

1987; Jan. 1988, April, May, 1991).

Global Horizontal data for the following cities and dates:

Victoria's Milling Corporation, 1984-1995

Quezon, 1972-1989, 1994-1996 (also known as Science Garden)

Each of the stations (except Catarman, Baguio, and Cagayan de Oro) with the sunshine

recorder data also have global horizontal measurements, either collected with a bimettalicstrip device (Laoag and Tacloban) or with a pyranometer (the four remaining stations).

However, these data were not included with the electronic data, and were not available

for this study.

The list of PAGASA solar radiation stations that provided by PAGASA shows many

additional stations with global horizontal measurements, using pyranometers. These

stations are:Basco

Echague, Isabela

La Trinidad, BenguetCasiguran, Quezon

Munoz, Nueva Ecija

Iba, Zabales


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2.2 Report: The Profile of Solar Insolation in the Philippines

The report The Profile of Solar Insolation in the Philippines provides tables and maps

of monthly average global horizontal solar resource data based on stations with actual

solar measurements as well as stations that have only sunshine recorders or cloud coverobservations. For the latter types of stations, empirical techniques such as a modification

of the Angstrom relation were used to develop solar resource estimates. The reportshows 17 stations with some form of solar measurement (Kahlisco pyranometer, Licor

Pyranometer, or other such as bimetallic strip recorder), where data collected in the early1980s are used. Seven of these stations also have sunshine recorders, which allows for

the development of the Angstrom coefficients. Data for 65 stations where sunshine

recorders or cloud cover observations are made are also provided.

2.3 UMASS/Lowell Data Report

In 1991 the University of Lowell Photovoltaic Program developed an international solarradiation data base, providing monthly average daily total solar radiation data for

numerous stations around the world. Most of the data were derived from sunshine

recorders. The report shows a total of fifteen stations for the Philippines.


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3. Description of the Climatological Solar Radiation Model

The modeling approach that was developed for the production of the U.S. National Solar

Radiation Data Base (NSRDB 1993) was modified to provide large area, high spatial

resolution of solar resources using a global satellite-derived cloud cover data base. Theoriginal model, METSTAT (Maxwell 1998a), calculates atmospheric extinction for clear-

sky and cloudy conditions using inputs of opaque and translucent cloud cover derived

from ground observations, precipitable water vapor, ozone, and aerosol optical depth.The output, then, is hourly values of surface direct normal, global horizontal, and diffuse

solar radiation. The METSTAT model was modified to generate monthly average dailytotal values of the three elements for each Real-Time Nephanalysis (RTNEPH) grid cell.

The modified model is known as the Climatological Solar Radiation (CSR) model(Maxwell, George, and Wilcox 1998b). The RTNEPH data use ground-based cloud

cover observations where available (generally, these are three-hourly observations

obtained from national weather services around the world), and Polar OrbitingEnvironmental Satellite imagery to interpolate between the stations. Although the world-

wide RTNEPH data are available on a three-hourly basis for a period beginning 1

August, 1983, the version of the data used in the CSR model is a histogram data basecovering the period from 1985 to 1992. The histograms of total cloud cover for hours

between sunrise and sunset were used to determine monthly average total cloud cover

during daytime hours. The histograms for low, middle, and high cloud layers were used

to estimate monthly average opaque cloud cover.

The CSR model has been run for a number of regions around the world, including the

entire east Asia region. The Philippines were included in the east Asia calculations, andthe results of these calculations form the basis of the modeled assessment provided here.

Preliminary evaluations of the monthly average daily total model output for several

locations around the world show agreement with ground stations between 5 - 15%, with


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It was noted in Figures 2 through 14 that two ground stations are available with which to

compare the CSR model data grid values. Here, inFigures 17-18,we see profiles of themonthly values comparing the ground station with the corresponding CSR model data

grid value. The figures show that, particularly at Science Garden, the CSR model tends

to produce slightly higher values than the ground observation. However, it is importantto note that the data grid represents the average resource over a 1600 km

2, while the

ground station is a point value, which could be valid throughout some portions of the

area.

6. Summary and Conclusions

The results of this analysis shows that the CSR model output provides results that arecomparable to values obtained from surface stations. However, the CSR model is

capable of providing higher resolution data than the ground network. Nevertheless, the

spatial variation of the solar resource across the Philippines in any given month is low(approximately 10% to 20%), while the variation between the wet and dry seasons is

quite high (30% to 50%).

7. References

Maxwell E. L., METSTATthe solar radiation model used in the production of the

National Solar Radiation Data Base (NSRDB). Solar Energy62, 4, 263-279, (1998a).

Maxwell, Eugene L., Raymond L. George, and Stephen M. Wilcox, A ClimatologicalSolar Radiation Model,Proceedings of the 1998 Annual Conference, American Solar

Energy Society, Albuquerque, pp. 505-510, June 14-17, (1998b).

University of Lowell Photovoltaic Program, 1991: International Solar Irradiation

Database Version 1 0 University of Lowell Research Foundation 450 Aitken Street


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Victorias, Negros, Occ., #618C

Comparison of CSR Model Values with Measured Data

(1985 to 1991)

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Science Garden, #430

Comparison of CSR Model Values with Measured Data

(1985 to 1991)

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CSR

Measured

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Task 7Bb Report Philippine Renewable Energy Project

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