INTRODUCTION TO SOLAR ENERGY
The sun creates its energy through a thermonuclear process, which creates heat and electromagnetic radiation. Only small fraction of the total radiation produced reaches the Earth. Insolation is a measure of solar radiation energy received on a given surface area in a given time, and is expressed as average irradiance in watts per square meter or kilowatt-hours per square meter per day. Solar energy is then refers primarily to the use of this solar radiation for practical ends. Solar insolation of the world is well expressed in the map as figured below:
Figure: The amount of solar energy in hours, received each day on an optimally tilted surface during the worst month of the year based on accumulated worldwide solar insolation data
SOLAR RADIATION IN SARAWAK
Malaysia lies entirely in the equatorial region. The tropical environment has been characterized by heavy rainfall, constantly high temperature and relative humidity and has abundant sunshine and solar radiation. It is however extremely rare to have a clear day even in periods of severe drought. The annual average daily solar irradiations for Malaysia were from 4.21 kWh/m2 to 5.56 kWh/m2. The highest solar radiation was estimated at 6.8 kWh/m2 in August and November while the lowest was 0.61 kWh/m2 in December. The Northern region and a few places in East Malaysia have the highest potential for solar energy application due to its high solar radiation throughout the year. However, it is extremely rare to have a full day with completely clear sky even in periods of severe drought. The cloud cover cuts off a substantial amount of sunshine and thus solar radiation. Seasonal and spatial variations in the amount of sunshine received cannot be ruled out. Areas such as Kuching in Sarawak receive about 4 hours of sunshine per day on an average.
Figure: Estimates of annual averaged daily global solar irradiance for Sarawak
(Source: Daniel Ruoss, 2008)
The solar radiation mapping is based on data from Universiti Kebangsaan Malaysia, Meteonorm V6.1 software and satellite data from Meteotest. It is based on very few ground based data stations - available in Meteonorm V6.1 (www.meteonorm.com), overlapped the semi-completed irradiance map with satellite data from Meteotest in Europe. Satellite images have been identified as an alternative and accurate method for predicting average annual daily solar irradiation of a specific location. These images can be use to predict the performance and sizing of various solar energy systems The satellite data can be averaged over 1 year and provides indication of the irradiance situation in the spots which have no station. Using the statistical data from numerous ground based data gathering stations over 10 years and correlate with satellite data filling in the blanks where no data station is available.
The following Table shows the monthly averaged daily global solar radiation (peak sun hour) and sunshine hour for four observation stations in Sarawak.
Table: Average daily sunshine hour by month for selected cities in Sarawak
(Source: Sarawak Methological Department and KeTTHAIrradiation Data for Malaysia )
Irradiation - The total quantity of radiant solar energy radiation per unit area received over a given period of time, i.e. the energy of the solar radiation per unit area over that time period. Units in common usage include MJ/m2, kWh/m2 and peak sun hours (PSH). NOTE: 1 kWh/m2 = 1 PSH = 3.6 MJ/m2.
SOLAR IRRADIATION MEASUREMENT
Pyranometers are radiometers designed for measurement of the solar irradiance on a plane surface Pyranometersometimes called a solarimeter, which is used to measure broadband solar irradiance on a planar surface and is a sensor that is designed to measure the solar radiation flux density in W/m2 (watts per metre square) from a field of view of 180 degrees. Not all of the solar energy reaching Earth’s outer atmosphere reaches the surface of the Earth. Some of this energy is reflected back out into space and some of it is absorbed in the atmosphere itself. Pyranometer instrument can be used for measuring solar radiation received from a whole hemisphere. It is suitable for measuring global sun plus sky radiation.
Figure: Pyranometer installed on site for solar irradiance measurement
SOLAR ENERGY APPLICATION
To gather and convert the available solar energy to electricity, Photovoltaic (PV) or solar panels are used. Despite the abundant resource, solar PV applications in Malaysia are limited to mainly stand-alone PV systems, especially for rural electrification where the technology costs are highly subsidized. Hybrid systems based on PV and diesel generators have been used for the electrification of remote islands where grid connection is a costly option. Rural electrification projects particularly in Sabah and Sarawak have also incorporated PV systems in places where supply from the grid may not be possible for years to come. Other minor applications being promoted include telecommunication, street and garden lighting and recently, for powering the parking ticket dispensing machines.
Figure: On-site application of PV systems for electricity
(Source: Research and Development Division, Sarawak Energy Berhad)