While evaluating the performance of a solar power plant, it is important to review problems arising both from unavoidable as well as avoidable reasons.

The efficiency of solar power plants can be indicated with the help of the Performance Ratio it has achieved for each year, similarly the CUF achieved and one can also make use of the actual generation data available for the power plant to understand the effectiveness of the power plant.

But you must also know about the losses incurred by the power plant, before making your investment decisions. Like any other system, power plants are also subject to unavoidable losses and an evaluation of the power plant performance should be done keeping these in mind. But a generation loss owing to situations that were avoidable should be a red alert for the investor.

You, as an investor, must check out with the current EPC installer as to what are the kind of problems and generation losses the plant has seen over the years. You must also try and understand the methods and effectiveness with which these problems have been mitigated.

We have listed below the probable causes for generation failures in a power plant and the extent of losses that are usually caused by it. This can serve you as a guideline against which you can evaluate the loss pattern in your power plant.

Major losses, their causes and suggestions to reduce them for an existing power plant

• Losses owing to temperature de-rating:

Power plant components like the panels and inverters perform negatively at high temperatures. And this loss can be higher than the simulated results at the design stage. This is owing to the fact that temperatures at the actual site can vary from that recorded based on meteorological data. It has been found that in hot and humid regions, the losses due to high temperatures can be anywhere is the range of 6-8%.The only way to minimize these losses is by going for inverters that a have high ambient(outside) temperature tolerance and also panels with a low temperature dependence. You might want to check on these parameters for the inverters and panels. A high-quality power plant will already have considered these in the design stage and would have limited the temperature related losses to around 5%

• Losses owing to shading:

Panel shading can occur even after careful layout. This shading can be usually caused by cloud covers, in which case it is an uncontrollable factor. This shading can be more prominent during winters and rainy seasons. Additional shading losses can occur due to the growth of vegetation near and around the modules. This shows negligence on the part of solar installers and you might want to look more into the cleaning practices followed by him/her

• Losses owing to inverter breakdowns:

Make sure to track the inverter breakdowns faced in a year. If the inverter was chosen wisely, the breakdown rates associated with the plant should be a maximum of once a year and the downtime for it should have been a maximum of two days.

• Soiling losses:

Soiling of solar panels can occur as a result of dust and dirt accumulation. In most cases, the material is washed off the panel surface by rainfall; however dirt like bird droppings may stay even after heavy rains. The most critical part of a module is the lower edge. In a well-maintained plant, with a cleaning frequency of about once in two weeks and rigorous cleaning pattern, the losses owing to soiling can be held at less than 2%. Solar Mango has seen cases where the solar power plants, left uncleaned for months together, have seen a generation loss up to 15%

• Cabling losses:

Most installers claim this as the major contributor to generation loss. But however a carefully designed plant, with optimal cable size selection, optimal design layout to ensure minimalistic use of cable length, optimal cable choice, etc. can help reduce cabling losses in a power plant. A high-quality solar power plant should limit the cabling losses to less than 3%. There have been cases where the cable losses have reached up to 6% merely due to improper choice of the thickness of cable insulation along with increased length between the panels and inverter rooms

• Monitoring Deficiency:

Do check out the level of monitoring implemented in the power plant. The   basic inverter tied monitoring systems do not come with a string level monitoring solution. As the monitoring of data is not on string level, it becomes difficult to identify the location of under- rated string, this monitoring deficiency will affect the plant output as the fault clearing time is increased which ultimately affect the generation from the  plant. Installers are known to struggle with this problem due to lack of foresight shown in the plant implementation.

• Under-Performance of Trackers:

A wrong decision in the choice of trackers can lead to additional losses. Today’s technologies ensure that the trackers deployed are robust and cause little issues to the solar power plant. However, trackers are the only solar power plant components that have moving parts, and a poor tracker could be affected due to a defect in one of its motors. But these ideally should not cause any damage to the power plant, it should only be contributing to the loss of the additional generation that would otherwise have been obtained from using it.

• Theft and Vandalism:

Some EPCs are known to cite these reasons for unanticipated generation losses associated with the power plants. The only way to mitigate these issues is through provisions for security systems. Had they been deployed, generation loss due to theft and other activities by miscreants, could have been limited, if not completely resolved.

You might want to check these questions on Solar Power Plant Evaluation- Plant Performance

• What is the average CUF (Capacity Utilisation Factor) of the power plant?-Here
• What are the performance guarantees provided by the installer?-Here
• What is the generation data from the power plant? Is it according to the industry standards?-Here
• What have been the cleaning practices for the panels over the years?-Here
• What are the O&M practices followed?-Here
• How do you check the quality of the  O&M company and personnel? – Here
• What are the innovations employed in the power plant? How can they impact your  financial returns?-Here
• Is there scope for expansion of the power plant, in terms of scale?-Here

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