Solar energy for electricity generation is becoming increasingly popular in many countries. These power plants are implemented in several different schemes. Megascale large project are implemented to get their economy of scale and other related benefits especially in decerts or arid Areas where land used for other purposes are Limited. Typically for setting up of a 1000KW power plant about 4 acres land is required. For Areas where the Solar insolation is high the land required may become smaller and power plant will be more economical. At the surface of the sun, the intensity of the solar radiation is about 6.33×107 W/m2.
However after travelling a long distance to reach earth,The Solar intensity at the edge of the atmosphere is 1400 W/m2 .and after transmitting through the atmosphere Global mean solar power at Earth's surface is only 170 W/m2.
There are many challenges in harnessing the solar power generated from a large Solar Power Plant connected to a small isolated power system. As obviously known,at any given time their total power generation connected to the power system must be equal to the total demand of the Lords and the losses in the transmission line and distribution systems. For the normal load variations created by the switching on and off of electrical equipment, system operator uses a power generator to increase and decrease its power output so that the balance is met. This can be easily controlled by sensing the frequency of the power systems with increases when there is excess power generation than consumption and frequency decreases if the generation is less than the consumption. When there are a large internittent power plants such as large solar power plants of several 100 MW scale, the generation variation created due to the cloud cover over the solar power plants is very high and system operator may be incapable of adjusting his generators to balance the system.This is particularly a Vulnerable question as the the solar panels are concentrated at one location in a large solar power plant and shading by a large cloud is a highly probable.
The advantage of solar rooftop systems is that the roofs are distributed over a large area and all roofs being covered by cloud at the same time is very unlikely. Another major advantage is that there is no additional land requirement as power plants are mounted on already existing roofs. Therefore rooftop solar PV systems ideally suite countries having land restrictions or highland costs.
Rooftop systems being smaller in size and due to the requirement of individual inverters etc.make their specific cost a little larger than large-scale solar power plants but the Solar Panel suppliers get some of these disadvantages offset by doing bulk purchase of solar panels and inverters and other accessories.
Source-Development of Grid Connected RoofTop Solar PV Systems by Anura Wijayapala
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