2.4 Frequently Used Metrics and Terminology for PV Modules and Systems Several technical metrics are used when discussing PV technologies and the economics of PV. The following metrics are used extensively throughout this report: Efficiency (specifically, conversion efficiency), Power, Installed cost per watt, Production cost per watt, Reliability, and Levelized cost of electricity (LCOE). For PV cells, efficiency is defined as the ratio of electric power generated by the solar cell to the amount of incident solar power. If a solar cell illuminated by 100 W of solar power generates 15 W of power, the cell’s solar energy conversion efficiency is 15%. In this report, the terms “efficiency” or “efficient” without a modifier always refer to the solar energy conversion efficiency. When referring to manufacturing or costs, this report specifically uses the term “operational efficiency.” Power is the rate at which energy is supplied by the PV cell or module. The amount of power contained in the solar spectrum hitting a given area is not uniform across the globe. Therefore, standard test conditions of 1 kW/m 2 at 25°C were established to allow researchers and companies to communicate performance measurements comparably. Thus, all power ratings for solar cells and modules are reported subject to conditions that have been artificially defined, not what they will experience in the field. The installed cost per watt of a PV energy system refers to the sum of all module, BOS, installation, and other costs divided by the power rating of the system. This study quantitatively evaluates only the PV module component of the system. The common metric for reviewing manufacturing costs for PV modules is the production cost per watt . Production cost per watt captures increases in conversion efficiency and
Chapter 2 — Background Information on Photovoltaics 2-7 increases in operational efficiency of production systems. As cell technology improves, so does the cell’s efficiency rating, which lowers the materials cost per watt and increases the power rating of a module. Improvements in manufacturing technology also place downward pressure on production cost per watt. PV systems are solid-state energy systems that have long lives. The minimum guaranteed lifetime for modules is 25 years, with the expectation that most modules will convert solar energy into electrical current for additional years. This concept is referred to as reliability . The total installed cost of a system is considered along with the system’s lifetime and power rating to yield the LCOE . The LCOE is usually presented as dollars per kilowatt-hour ($/kWh). The total energy produced is calculated by power multiplied by time and is reported by power producers as kilowatt-hours. The amount of energy in kilowatt-hours produced in a year by an electricity generator is the capacity in kilowatts multiplied by the number of hours in a year adjusted by a capacity factor to adjust for periods of nonoperation, or in the case of solar power, for when the sun is not shining at its peak. In the United
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- Spring '18
- Professor Obura Oluoch
- Photovoltaics, Solar cell