Comparison of typical meteorological year and on-site measurements for solar PV site selection

The standard approach when simulating photovoltaic output is to employ Typical Meteorological Year (TMY) data sets. This paper uses statistical analyses to investigate several TMYs. The objectives are: (1) to ascertain which TMY generation method most accurately reproduces solar conditions in the UK; (2) to discover the minimum time resolution at which TMYs delver reliable results; and (3) to determine if there are any circumstances in which TMYs can replace long-term time series

Transient preconditioning in CIGS solar cells and modules

Transient preconditioning refers to a light induced performance change in CIGS which occurs and relaxes on a millisecond to seconds timescale. This effect appears to be distinct from the better known and more persistent preconditioning which typically takes several hours or days to relax. In this paper some properties of this phenomenon are explored including the variation of if the effect with voltage and temperature. The consequences for repeatable and accurate device measurement are explored. In particular the transient rise in photocurrent during measurements using a pulsed simulator can be successfully eradicated using voltage preconditioning when there is no gap between the preconditioning voltage being applied and the start of the illumination pulse

Optimising I-V measurements of high capacitance modules using dark impedance measurements

A method is demonstrated to optimise pulsed IV measurements of high capacitance PV modules, using dark IV and impedance measurements. The impact of capacitance during I-V measurements is minimised by changing the shape of the voltage ramp. The optimisation can be performed simply and automatically for each individual module during the charging period for the simulator. As an additional benefit of this method the extracted C-V profile can be used to estimate the minority carrier lifetime for the module. The system is demonstrated by using a high capacitance n type module, which is successfully measured in a single 10ms illumination pulse

Effects of lamination condition on durability of PV module packaging and performance

Ten mini-modules of glass /encapsulant /backsheet structure were laminated under the condition of the same curing time and pressure, but different curing temperatures and aged in damp-heat accelerated ageing test in order to investigate the effect of temperature on the durability of PV module packaging and performance. Results show that the mini-modules using EVA as encapsulant were affected more by the laminating temperature compared to the mini-modules using modified ionomer. For EVA modules, samples with relatively low curing temperatures at 135-140ºC appeared to have higher adhesion between EVA and glass, lower moisture permeability into module and better dielectric of cells than those with high curing temperatures

Evaluation of proposed photovoltaic energy rating standard: validation against outdoor measurements

Effective energy production is the ultimate purpose of photovoltaic devices and thus should be considered in describing device performance. This paper investigates the impact and relevance of the proposed IEC energy rating standard reference days on the energy prediction of various device technologies in the UK climate and found MIMT and MIHT are most relevant. Three different module technologies have been tested over a wide range of module temperature (Tmod) and irradiance (G) level in outdoor measurement conditions. Performance of each technology is calculated in terms of distribution of energy generation with the main influencing parameters. The paper also compares the power distributions (with irradiance and temperature) of crystalline silicon modules in indoor and outdoor measurement conditions. Sensitivity analysis of energy yield estimation and its modelling accuracy are analysed for three devices with the different combinations of Gmod and Tmod and its found that c-Si and a-Si device technologies underestimated by 7.6% and 6.8% but CIGS module overestimated by 0.05% in the UK climate

Uncertainty in calibration and characterisation of pyranometers

This work quantifies the uncertainties of thermoelectric pyranometer measurements made with different calibration methods. Measurement campaigns supported both the evaluation of pyranometer calibrations and newly proposed approaches to characterise the pyranometers in indoor and outdoor conditions. Estimated uncertainties were then applied to a year-long irradiance dataset to evaluate the impact on the assessment of the annual solar irradiation. This study highlights the differences seen when calibrating pyranometers under different conditions and procedures. Such deeper insight of pyranometers response aims ultimately to assist the integration of short-term (pyranometers) and long-term (satellite-based) data to a more accurate evaluation of PV energy yield

Towards a fully LED-based solar simulator - spectral mismatch considerations

LED solar simulators have a high potential for high quality characterisation of solar cells. One of the main challenges is to achieve a close spectral match to the AM1.5 solar spectrum from 350nm to 1300nm. The main sources of measurement uncertainty are the spectral mismatch, the non-uniformity of light and the reference cell. The spectral mismatch can increase the measurement uncertainty significantly. In order to minimize a major uncertainty factor a close spectral match needs to be acquired. It will be shown that the usage of LEDs, which are narrow wavelength emitting light sources, can improve the measurement accuracy of the solar simulator by accurately matching the solar spectrum. The process of choosing the best combination of wavelengths and the LED population per wavelength is a complex, dual optimization problem. This paper evaluates the optimisation algorithms chosen and examines the influence of different fitness functions in acquiring a Class A+ spectral match

Potential for LED solar simulators

LED solar simulators have been discussed recently as a potential next generation solar simulator. This contribution evaluates the possibilities of generating a light field of appropriate spectrum with good uniformity. LEDs have very different optical characteristics compared to standard lights and this needs to be considered in the optical design. The aim in this paper is to achieve a close spectral match to the AM1.5 solar spectrum from 350nm to 1300nm. A total irradiance of 1000 W/m2 needs to be acquired. Additionally, the non-uniformity of light needs to be equal to or less than 1%. The key to mix spectra and achieve the desired intensity and uniformity is the optics. This paper evaluates different optical layouts to assess the potential for fully LED based solar simulators. The TIRs perform better collecting more light than other optics tested

Assessment of potential for photovoltaic roof installations by extraction of roof slope from lidar data and aggregation to census geography

Leading topics in PV research include field performance and grid impact. A national understanding of roof features (slope, orientation, area) is essential for modelling the timing of PV installation scenarios with their associated irradiance data. However, such information is not currently available. This paper demonstrates the extraction of building characteristics from LIDAR (Light Detection and Ranging) data. These characteristics are then aggregated and scaled-up to produce a UK-wide map of PV potential, based on suitable roof tilts and azimuths

The future scope of large-scale solar in the UK: site suitability and target analysis

This paper uses site suitability analysis to identify locations for solar farms in the UK to help meet climate change targets. A set of maps, each representing a given suitability criterion, is created with geographical information systems (GIS) software. These are combined to give a Boolean map of areas which are appropriate for large-scale solar farm installation. Several scenarios are investigated by varying the criteria, which include geographical (land use) factors, solar energy resource and electrical distribution network constraints. Some are dictated by the physical and technical requirements of large-scale solar construction, and some by government or distribution network operator (DNO) policy. It is found that any suitability map which does not heed planning permission and grid constraints will overstate potential solar farm area by up to 97%. This research finds sufficient suitable land to meet Future Energy Scenarios (UK National Grid outlines for the coming energy landscape)