The received solar radiation include both direct and diffuse radiations. The direct radiation can generate greater electricity or heat than diffuse radiation. Peak density of direct radiation in Thailand is approximately 1,350- 1,400 kWh/m2 yr, covering 3% of the count area in Central region and trys southern part of Northeaster region (See figure 2) while 19.5% of the country's area has approximately 1,200 1300 kWh/m2-yr (See figure 3). Density of direct radiation in Thailand usually escalates from danuary and reaches the peak in April before descending to the bottom in December.
According to the aforementioned data, some areas in Thailand have solar power potential that can be used to generate heat and electricity. The Department of Alternative Energy Development and Efficiency has conducted a number of pilot projects during 1983-2007 including 1,040 solar cell for power generation projects with a combined capacity of 2,900.816 kilowatt, solar cell standard development and testing project, solar hot water pipe lipment testing project, the study of potential production of sol cooling system project promotion of mixed system solar hot water project etc.