Various factors come into play when the performance of solar PV plants is evaluated
By Richa Chakravarty
Wednesday, April 09,2014: According to the latest data released by the Ministry of New and Renewable Energy (MNRE), the performance of the plants commissioned under Phase 1 of the Jawaharlal Nehru National Solar Mission (JNNSM) declined in October and November 2013.
As per the report, the utility scale plants under Phase 1 (Batches 1 and II) of the JNNSM reported capacity utilisation factors (CUFs) of 16-23 per cent in November 2013. This was a drop from the 18-24 per cent reported in October 2013, which was a further decline from September 2013.
One important measure of a solar power plant’s efficiency is the CUF, which refers to how much of the stated capacity a plant actually generates, compared to its total potential capacity in a laboratory with constant light. The higher the CUF, the more efficient the plant is at producing energy from the sun.
Of the 30 PV plants of 5 MW developed in the first batch of JNNSM, only 21 plants are producing energy. These have an average CUF of 19.48 per cent. The worst performing solar power plant is run by EMC Ltd in Uttar Pradesh, with a CUF of 14.97 per cent.
Factors affecting performance of solar PV plants
Efficiency of panels: Various factors come into play when the performance of solar plants is evaluated. Though solar panels carry a 25 year warranty and the developers, while procuring these panels, feel confident about the efficiency of these panels, the panels do not always perform as per their efficiency levels. “The interpretation of efficiency is very important. In reality, the generated power is much less than what is calculated. Since the modules carry a warranty, the developers generally ignore this aspect. But since each watt of sunlight is money, the developers need to look at all the details,” says Raghunandan, vice president, engineering, Kotak Urja Pvt Ltd.
Maintenance of panels: The developers usually overlook the aspect of maintaining the solar panels. Solar power plants are generally located in rural areas where there are minimal resources available for maintenance. For example, water is an important resource to keep the modules clean, and most of the villages suffer from water scarcity. “The developers should set up the infrastructure for maintenance. Right from water and electricity to manpower—every aspect should be kept in mind while setting up a solar plant,” says Raghunandan.
Proper monitoring: Another factor that the developers ignore completely is the monitoring of these solar panels. Says Raghunandan, “Similar to how railway tracks are monitored every day, solar plants also need to be monitored regularly. Stringent monitoring of solar panels is required to get the required efficiency. Hence, right energy management systems should be in place to monitor the power produced and consumed.”
Internal degradation: This is a natural process. In the case of solar energy, the module protects the cells and internal electrical connections against moisture ingress. Due to continuous exposure to sunlight, the encapsulation materials slowly break down due to exposure to ultraviolet (UV) rays. They become less elastic and more like plastic. Over time, this limits the panel’s ability to force out moisture. The trapped moisture eventually leads to corrosion at the cell’s electrical connections, resulting in higher resistance at the affected connections and, ultimately, decreased module operating voltage. However, this happens over years of exposure. A PV module’s operating life is largely determined by the stability and resistance to corrosion of the materials from which it is constructed. Hence, there are several failure modes and degradation mechanisms which reduce the power output.
Usage of the right technology: Finding the right location to set up a plant, based on accurate radiation data, and using the right solar modules for that particular area are other major factors to be looked at. The same technology may not be optimal in all parts of the country. “Many developers have only recently entered the market and lack experience. A solar power project demands good engineering,” says Raghunandan.
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