• Energy Research

The effect of amorphous Silicon (a-Si) module degradation on inverter sizing is investigated in this paper to identify appropriate sizing ratios even if only undegraded data-sheet values are available. The seasonal degradation and annealing pattern of a-Si modules requires special attention to the sizing of inverters for these devices, as is demonstrated in this paper for three types of modules with different degradation rates. The efficiency of the inverters depends on the sizing ratio as well as the DC input voltage. Here data of an inverter with relatively dependence on operating voltage is used. As modules degrade, the optimum ratio of system rated power with respect to inverter nominal power increases by 10 to 15% for the specific inverter. Considering the module life-time, the inverter size chosen to be matched to the degraded power and voltage rating achieves high efficiency over the life-time of the modules, while the inverter chosen to match initial values, as given by some manufacturers on their datasheets, can add about ten percent losses to the operation.

The effect of amorphous Silicon (a-Si) module degradation on inverter sizing is investigated in this paper to identify appropriate sizing ratios even if only undegraded data-sheet values are available. The seasonal degradation and annealing pattern of a-Si modules requires special attention to the sizing of inverters for these devices, as is demonstrated in this paper for three types of modules with different degradation rates. The efficiency of the inverters depends on the sizing ratio as well as the DC input voltage. Here data of an inverter with relatively dependence on operating voltage is used. As modules degrade, the optimum ratio of system rated power with respect to inverter nominal power increases by 10 to 15% for the specific inverter. Considering the module life-time, the inverter size chosen to be matched to the degraded power and voltage rating achieves high efficiency over the life-time of the modules, while the inverter chosen to match initial values, as given by some manufacturers on their datasheets, can add about ten percent losses to the operation.

Outdoor measurement campaigns of PV module performance are normally affected by a relatively large number of outliers. The aim of this paper is to develop a statistically sound approach of obtaining a dataset that allows one to analyse continuously monitored devices for use of high volume data measurements. This paper uses ISC as a self-reference parameter to measure the incident irradiance on the module, which largely eliminates the error due to differences in spectral and angular response between test and reference detector. The outlier identification procedure is based on statistical distribution analysis of different performance descriptors and it assures 0.99 confidence level and the same skewness for the remaining data. This approach can be applied to whole datasets as well as for data in specific irradiance-temperature bins. The developed methodology will be used to analyze outdoor data from different devices at different locations with reduced uncertainty. It is shown that this approach is particularly useful for obtaining lower uncertainties in low irradiance measurements.

Outdoor measurement campaigns of PV module performance are normally affected by a relatively large number of outliers. The aim of this paper is to develop a statistically sound approach of obtaining a dataset that allows one to analyse continuously monitored devices for use of high volume data measurements. This paper uses ISC as a self-reference parameter to measure the incident irradiance on the module, which largely eliminates the error due to differences in spectral and angular response between test and reference detector. The outlier identification procedure is based on statistical distribution analysis of different performance descriptors and it assures 0.99 confidence level and the same skewness for the remaining data. This approach can be applied to whole datasets as well as for data in specific irradiance-temperature bins. The developed methodology will be used to analyze outdoor data from different devices at different locations with reduced uncertainty. It is shown that this approach is particularly useful for obtaining lower uncertainties in low irradiance measurements.

In this work, the mechanical properties of encapsulation materials for photovoltaic modules have been studied. A finite element model has been developed to simulate the degradation of solder bonds within modules subjected to different environmental conditions. Various polymeric encapsulants are characterized using constitutive techniques and included in the model. It is shown that the degradation rates of the solder bonds are dependent on the behavior of the encapsulant and that some encapsulants may cause higher or lower degradation than others depending on the use-environment.

In this work, the mechanical properties of encapsulation materials for photovoltaic modules have been studied. A finite element model has been developed to simulate the degradation of solder bonds within modules subjected to different environmental conditions. Various polymeric encapsulants are characterized using constitutive techniques and included in the model. It is shown that the degradation rates of the solder bonds are dependent on the behavior of the encapsulant and that some encapsulants may cause higher or lower degradation than others depending on the use-environment.

AbstractThe energy yield delivered by different types of photovoltaic device is a key consideration in the selection of appropriate technologies for cheap photovoltaic electricity. The different technologies currently on the market, each have certain strengths and weaknesses when it comes to operating in different environments. There is a plethora of comparative tests on-going with sometimes contradictory results. This paper investigates device behaviour of contrasting thin film technologies, specifically a-Si and CIGS derivatives, and places this analysis into context with results reported by others. Specific consideration is given to the accuracy of module inter-comparisons, as most outdoor monitoring at this scale is conducted to compare devices against one another. It is shown that there are five main contributors to differences in energy delivery and the magnitude of these depends on the environments in which the devices are operated. The paper shows that two effects, typically not considered in inter-comparisons, dominate the reported energy delivery. Environmental influences such as light intensity, spectrum and operating temperature introduce performance variations typically in the range of 2–7% in the course of a year. However, most comparative tests are carried out only for short periods of time, in the order of months. Here, the power rating is a key factor and adds uncertainty for new technologies such as thin films often in the range of 10–15%. This dominates inter-comparisons looking at as-new, first-year energy yields, yet considering the life-time energy yield it is found that ageing causes up to 25% variation between different devices. The durability of devices and performance-maintenance is thus the most significant factor affecting energy delivery, a major determinant of electricity cost. The discussion is based on long-term measurements carried out in Loughborough, UK by the Centre for Renewable Energy Systems Technology (CREST) at Loughborough University.

AbstractThe energy yield delivered by different types of photovoltaic device is a key consideration in the selection of appropriate technologies for cheap photovoltaic electricity. The different technologies currently on the market, each have certain strengths and weaknesses when it comes to operating in different environments. There is a plethora of comparative tests on-going with sometimes contradictory results. This paper investigates device behaviour of contrasting thin film technologies, specifically a-Si and CIGS derivatives, and places this analysis into context with results reported by others. Specific consideration is given to the accuracy of module inter-comparisons, as most outdoor monitoring at this scale is conducted to compare devices against one another. It is shown that there are five main contributors to differences in energy delivery and the magnitude of these depends on the environments in which the devices are operated. The paper shows that two effects, typically not considered in inter-comparisons, dominate the reported energy delivery. Environmental influences such as light intensity, spectrum and operating temperature introduce performance variations typically in the range of 2–7% in the course of a year. However, most comparative tests are carried out only for short periods of time, in the order of months. Here, the power rating is a key factor and adds uncertainty for new technologies such as thin films often in the range of 10–15%. This dominates inter-comparisons looking at as-new, first-year energy yields, yet considering the life-time energy yield it is found that ageing causes up to 25% variation between different devices. The durability of devices and performance-maintenance is thus the most significant factor affecting energy delivery, a major determinant of electricity cost. The discussion is based on long-term measurements carried out in Loughborough, UK by the Centre for Renewable Energy Systems Technology (CREST) at Loughborough University.