SOLAR INVERTER SYSTEMS
The global demand for electricity has increased significantly in recent years, demanding a shift to find renewable energy sources to compensate for this need. In addition to Wind, solar photovoltaic (PV) cell farms are becoming another common renewable energy source and must have their subsystems in peak performance to prevent costly downtime. Implementing a maintenance plan to include fluid condition monitoring is an important step in optimizing solar power generation.
Inverter systems are a crucial part of solar cell farms to convert the DC output of the solar PV cells and battery storage systems to AC output to the grid. There are various types of inverter systems commonly used in the power generation field to provide output to the grid.
A central inverter system utilizes all of the solar PV cells to feed into one main central inverter, which then converts the DC voltage to AC for distribution. Whereas in a string inverter setup, the PV cells are split into several groups/series and each series has its own inverter system feeding into the grid. Both inverter systems need a reliable cooling method to keep it from overheating and shutting down. One of the most common and tested cooling methods for solar PV cell farms is the glycol/water cooling system.
Keeping maximum uptime is crucial and the best way to do this is by monitoring the system’s fluid conditions. Solar Inverter fluid condition monitoring is the simplest way to ensure the health of the cooling system, like the electrical fail-safes, and monitoring systems to keep the inverter working at peak performance. The cooling system on inverter systems are instrumental to maintaining operating temperatures at the optimal level. For example, a 1 MW inverter with 98% efficiency will generate around 20kw of thermal energy that will need to be dissipated off. This places a significant thermal load on the cooling system, thus ensuring the condition of the fluids is imperative to optimize inverter performance.
With many of the coolant filled systems, there are a variety of tests that can be performed. These tests can help to determine the condition of the inverter and the serviceability of the coolant. There are many different formulations that can be used in these systems, but only a few fit the application. Depending on the elemental material used in the construction of the inverters, supplemental coolant additives will apply to each. Aluminum being the most common material used in inverter cooling systems. Thus the coolant must not be over reactive, which will cause corrosion, but it also must be reactive enough to protect the aluminum from corrosive reaction. As these systems are sensitive, it is important that the level of testing covers the majority of the potential reactions that may occur.
A simple pH test or percent glycol is not sufficient to determine the serviceability of the coolant, and therefore limits field testing to determine serviceability for the fluid. A field test is great solution for spotting a potential problem. In addition, a sampling should be done to confirm the abnormality and what maintenance course should be taken to correct any irregular conditions identified.
Inverter maintenance personnel should consider the type of analysis and a competent testing source. There are many sources for general coolant testing, as the inverter fluid and the materials used are different than a typical cooling system. At Bureau Veritas, we have developed a series of tests and parameters to monitor the inverters fluid serviceability. Our experts determine if the fluid in service is the best for the application. Then testing is preformed to determine if there are any abnormalities in the fluid such as degradation from the high operating temperatures these systems produce.
| TEST PACKAGE | APPLICATION |
Premium Coolant (TSTPELC) |
Corrosion Metals & Inhibitors Iron, Aluminum, Lead, Copper, Tin, Silicon, Boron, Sodium, Potassium, Molybdenum, Phosphorous, Zinc, Calcium, and Magnesium. |
Recommended for customers with high asset dollar equipment that are using ELC Coolant and Solar Inverter Fluids.
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Physical Tests Appearance, Color, Foam, Magnetic precipitate, Non-magnetic precipitate, Odor, pH, Glycol %, Freeze Point, Nitrites, Specific Conductance, Total Hardness, and Reserve Alkalintiy. |
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Contaminant and Inhibitor Anions by Ion Chromatography Fluoride, Chloride, Nitrite, Nitrate, Sulfate, Glycolate, Formate, Acetate, and Oxalate. |
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Organic Acid and Azole Inhibitors by HPLC Benzoate, 2-Ethylhexanoic acid, Sebacic acid, Octanoic acid, p-Toluic, Adipic, MBT, TTZ, BZT. |
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The goal of solar inverter coolant monitoring testing is to confirm that the correct fluid is in service, if the fluid is serviceable or requiring maintenance, and if any maintenance is required and to what extent. If corrosion has occurred, it will require a different corrective action than if the fluid is at the serviceability life extensity. For this occurrence, the most cost effective way to maintain the inverters is to flush and service the fluid. Our goal is to help users create a maintenance plan for preventing the corrosion process, in which in extreme cases, the oxide formation acts as an insulator and the inverter will not stay within its acceptable operating temperature and cause failure.
In summary, fluid analysis of the cooling system is a necessary part of a maintenance program to optimize solar inverter systems, ensuring peak performance. At Bureau Veritas, our fluid analysis provides insight into the fluid to determine the condition of the components being cooled and other abnormalities. Keeping the coolant in the correct balance is important and prevents corrosion, electrolysis, hotspots, and failures. All of which play a role in keeping the performance efficiency and maintaining maximum up time.
Written By:
David Scott
Data Analyst
Bureau Veritas - Oil Condition Monitoring