POWER AND ENERGY PRODUCTION OF PV MODULES

The real electrical parameters rarely correspond to the nominal electrical parameters supplied by the manufacturers. Moreover initial degradation occurs in almost all types of modules during the first period of exposure. Project planners and installers are increasingly asked to provide production and behaviour estimates for the systems they install. Therefore a direct performance comparison of PV modules is needed. The ISAAC-TISO centre carried out systematic outdoor testing, under real operating conditions, and indoor tests on the most important modules currently on the market. In March 2006 a new 15 month test cycle (no.10) started. Fourteen different module types were chosen, trying to include the greater part of available technologies: 8 mc-Si, 2 sc-Si, 1 HIT, 2 a-Si and 1 CdTe. All the modules were purchased anonymously. I-V measurements @STC are periodically performed. In test cycle 10 the power at the purchase of a c-Si module is on average 1.5% lower with respect to Pn but ranging from 0.2% and-3.8%. Stabilized power after 15 months is on average 3.6% lower with respect to Pn and ranging from-0.7% and-8.2%. All types of modules are in the warranty limits. Differences (average of 2 modules) in annual energy production [kWh/kWp], of 14 different module types compared to the best module, with nominal power Pn as reference, reach 10%. The thin-film modules have a slightly higher energy yield with respect to c-Si modules but evaluation of these technologies is complicated by the fact that their STC power changes in time (degradation and recovery effects).

Solar Energy, 2014

This paper presents an evaluation of the performance degradation of Photovoltaic modules after few operation years in a tropical environment. To this end, the International Center for Research and Training in solar energy at Dakar University and the Lasquo-ISTIA laboratory of Angers University have put in place a research project in order to investigate the impact of the tropical climatic conditions on the PV modules characteristics. Accordingly, two monocrystalline-silicon (mc-Si) PV modules and two polycrystalline-silicon (pc-Si) PV modules are installed at Dakar in Senegal and monitored during a few operation years: Module A (16 months), Module B (41 months), Module C (48 months) and Module D (48 months). After few operation years under tropical environment, the global degradation and the degradation rate of electrical characteristics such as I-V and P-V curves, open-circuit voltage (V oc), short-circuit current (I sc), maximum ouput current (I max), maximum output voltage (V max), maximum power output (P max) and fill factor (FF) are evaluate at standard test conditions (STC). This study reports on data collected from 4 distinct mono-and poly-crystalline modules deployed at Dakar University in Senegal. The study has shown that P max , I max , I sc and FF are the most degraded performance characteristics for all PV modules. The maximum power output (P max) presents the highest loss that can be from 0.22%/year to 2.96%/year. However, the open-circuit voltage (V oc) is not degraded after these few exposition years for all studied PV modules.

This work has been undertaken to examine the warranties offered by the PV module manufacturers for degradation after long term field operation under Thailand weather conditions. Samples from the four lots of PV modules comprising on mono crystalline, poly crystalline and amorphous silicon, with different duration of field operation ranging from 9 to 14 years were tested for I-V curve characteristics under field conditions and measured values were corrected to Standard Test Conditions (STC) values by using correction procedure inscribed in IEC 60891 standard. The corrected values of output power and other parameters were compared with nameplate data for calculation of degradation during the period of operation. The actual degradation in output power for two lots of mono and one lot of poly crystalline silicon was found remarkably high (3.9, 3.0 & 2%/year) when compared with the warrantees (0.8-1%/year generally). However, interestingly the lot comprising on thin film amorphous-Si modules showed higher values of output power than nameplate. There were no visible defects in the modules except yellowing and discoloring. The enhanced degradation rates can be attributed to the quality of modules along with the effects of harsh field weather conditions.

Photovoltaic modules based on the relatively high efficiency crystalline technology are gaining importance in the photovoltaic market. Improving module performance is driven by a focus on lifetime yields and requirements of spaceconstraints sites. The materials used not only in thin film technologies but also crystalline pose problems in terms of measuring how much power is generated under STC. The fact that the modules power rates vary depends both on the amount of time they have been exposed to the sun and on their history of sunlight exposure in order to know the current state of the module. It is necessary to determine an easily accomplishable testing method that ensures the repeatability of the measurements of the power generated. This is essential because in order to have a reliable sample of the PV module population of a large PV plant, a huge no of modules must be measured. This paper shows different tests performed on different commercial crystalline PV modules both multi and mono, in order to find the best way to obtain measurements. A correlation was tested between sun exposure and power measured. A method for obtaining indoor measurements that takes periods of sunlight exposure into account is proposed. Also, temperature and irradiance coefficients were also determined for different technologies in order to obtain accurate measurements. Tests are operated in outdoor exposure and natural sunlight located in Gurgaon Region of Haryana (India) as specific composite climate environment, characterized by high irradiation and temperature levels.

Progress in Photovoltaics, 2009

This paper presents the results of electrical performance measurements of 204 crystalline silicon-wafer based photovoltaic modules following long-term continuous outdoor exposure. The modules comprise a set of 53 module types originating from 20 different producers, all of which were originally characterized at the European Solar Test Installation (ESTI), over the period 1982-1986. The modules represent diverse generations of PV technologies, different encapsulation and substrate materials. The modules electrical performance was determined according to the standards IEC 60891 and the IEC 60904 series, electrical insulation tests were performed according to the recent IEC 61215 edition 2. Many manufacturers currently give a double power warranty for their products, typically 90% of the initial maximum power after 10 years and 80% of the original maximum power after 25 years. Applying the same criteria (taking into account modules electrical performance only and assuming 2Á5% measurement uncertainty of a testing lab) only 17Á6% of modules failed (35 modules out of 204 tested). Remarkably even if we consider the initial warranty period i.e. 10% of P max after 10 years, more than 65Á7% of modules exposed for 20 years exceed this criteria. The definition of life time is a difficult task as there does not yet appear to be a fixed catastrophic failure point in module ageing but more of a gradual degradation. Therefore, if a system continues to produce energy which satisfies the user need it has not yet reached its end of life. If we consider this level arbitrarily to be the 80% of initial power then all indications from the measurements and observations made in this paper are that the useful lifetime of solar modules is not limited to the commonly assumed 20 year.