Article by Assist. Prof. Yod Sukamongkol (Ph.D.)
Director of Energy Conservation Office, Faculty of Engineering, Ramkhamhaeng University
The solar rooftop system is actually a photovoltaic power station, which has established solar panels mounted on the rooftop of a residential or commercial building or factory. DC electricity generated from PV panels will become AC electricity by passing through an inverter, then, it is delivered to the AC electric appliances such as television, refrigerator, computer, etc. At present, the photovoltaic (PV) solar power generation cost has decreased drastically comparing with the last few decades, which is about 3-4 bath per unit. This leads to a more widespread adoption of PV solar rooftop in private sector. Moreover, the government is already planning to liberalize the new solar rooftop program soon.
According to the Federation of Thai Industries (FTI) information, the solar rooftop system can reduce an electricity expenses of a factory by one-third as it can generate power by itself during the “On Peak” period, when power charges are normally high. In fact, this system decreases the factory’s peak demands as well as the total electrical energy consumptions which also results in the reduction of the total of float Time fee (FT) and Value Added Tax (VAT). For this reason, the private sector has been working on plans to utilize solar rooftop power generation for households and factories.
Five Factors Before Desired to Install the PV Solar Rooftop System
1. Location
Although the solar map of Thailand developed by the Department of Alternative Energy Development and Efficiency (DEDE) shows that Thailand has the high potential to generate the electrical energy by using the PV generation system with the average solar energy of 18.2 MJ/m2-day, there are some regions that has the low average solar radiation due to the monsoon or mountain valley such as the south-west (Andaman Cost) and the north-west of Thailand. On another hand, some provinces around the north-east such as Nakornratsrima, Burirum or Ubonratthani and some parts in the middle of Thailand such as Chainat, Autthaya or Lopburi have the high potential to utilize the PV system due to the high solar energy through the year. For further information, the solar map data is available at “http://www.dede.go.th/more_news.php?cid=126”
2. Direction and Slope of the Roof
To generate the maximum electrical energy, theoretically, PV panels must always be faced directly to the sun. As the Thailand’s Latitude is 5-20 oN, the PV panel should be installed facing to the south with the tilted angle of 5-20o to collect the incident radiation with the right angle leaded to the high average solar radiation all day long, then, the PV panel operates with the high performance. For example, the factory place in Samutprakarn province whose latitude is 13.55oN, therefore, its roof for installing PV solar rooftop should be faced to the south and its slope should be 13-14o, otherwise, the PV system will not generate efficiently and, then, the payback period will expand.
3. Surrounding Environment
Dust, moisture and smoke are factors that influences the efficiency of PV module by decreasing the solar radiation incident on the module’s surface due to the transmittance of solar radiation varied from about 2% up to 40% depending on the duration of dust accumulation, size and density of dust, and air pollution level. Thus, if the surrounding environment around the PV station has tons of dust and moisture, such as mine industry, furnace and stream generation plant, the PV modules should be cleaned from time to time to keep the high power generation with high PV conversion efficiency. This will make the higher maintenance cost and, again, the payback period will expand.
4. Characteristic of Energy Used
The energy used characteristics of each factory are different depending on processes, products and types of industry. To observe the behavior, the power analyzer is needed to be installed at the main distributed board (MDB) to continuously record the energy used characteristic of the factory. After a month, the observed data can be used to analyze and compare with the PV generation characteristic curve to design the PV solar rooftop size that is suitable for the desired deduction of electrical peak demand.
5. Among of Energy Consumption
One of the main parameters, that is the key needed in the feasibility study of the project, is the among of energy consumption or energy expense per month. It is not worth to invest the solar rooftop for a small size due to the per unit cost is high. Moreover, the smaller size of PV rooftop system makes the more payback period. However, for the feasibility study, all of factors must be considered along with tax measures or CSR benefit to make the project more interesting.
On the positive note, although the solar rooftop generation does not cover all of the factory’s energy consumption, It is an alternative way to reduce the energy expense. However, if the plant has the energy management with the excellent energy conservation, the generated energy from PV rooftop will supply over the demand. In the nearly future, when the government liberalize the solar rooftop program again, then, those generated electrical energy can be sell and the PV rooftop will be more interesting and more widespread adoption in industry and household.
