An overview of the activities and progress made during the US DOE Solar Energy Grid Integration Systems (SEGIS) solicitation, while maintaining reliability and economics is provided. The SEGIS R&D opened pathways for interconnecting PV systems to intelligent utility grids and micro-grids of the future. In addition to new capabilities are "value added" features. The new hardware designs resulted in smaller, less material-intensive products that are being viewed by utilities as enabling dispatchable generation and not just unpredictable negative loads. The technical solutions enable "advanced integrated system" concepts and "smart grid" processes to move forward in a faster and focused manner. The advanced integrated inverters/controllers can now incorporate energy management functionality, intelligent electrical grid support features and a multiplicity of communication technologies. Portals for energy flow and two-way communications have been implemented. SEGIS hardware was developed for the utility grid of today, which was designed for one-way power flow, for intermediate grid scenarios, AND for the grid of tomorrow, which will seamlessly accommodate managed two-way power flows as required by large-scale deployment of solar and other distributed generation. The SEGIS hardware and control developed for today meets existing standards and codes AND provides for future connections to a "smart grid" mode that enables utility control and optimized performance.

Mirror augmented photovoltaic (MAPV) systems utilize low cost mirrors to couple more light into a photovoltaic (PV) absorber. By increasing the light absorbed, they are expected to produce less expensive electricity. As a substrate candidate for back surface reflector mirrors, two grades of PMMA have been exposed to UV stress from two sources at two intensities for two doses in an effort to see the response of materials under different states of stress and after exposure to different amounts of total stress. By developing a framework for correlating stresses, such as short wave ultraviolet radiation, with responses, such as induced absorbance and yellowing, mirror durability we have made progress in developing lifetime and degradation science using mirror durability as a case study. All of the samples showed similarities in their degradation characteristics. The UV stress acceleration factor was quantized as 10.2 in short wave ultraviolet irradiance, and 15.8 in total shortwave UV dose. The effects of UV absorbers in protecting the polymer from degradation are discussed. Further study into degradation mechanisms will elucidate the exact phenomena that contribute to these material responses to stress.

The CPV community is still undecided on one critical issue: what material to use best for Fresnel lens parquets. Reliability and longevity are the most important, but all other properties play roles as well. We have developed and manufactured Fresnel lenses with the two commonly used materials: PMMA (Polymethylmethacrylate) and silicone on glass (SOG). Both lenses are designed for the same optical train for best comparability. This allows for better understanding the pros and cons of the materials and making an informed choice for a specific CPV module. While PMMA lenses are embossed from pre-fab sheets in a hot-cold process, the silicone lenses are cast from a heat-curing silicone rubber at moderate temperatures, reducing the energy consumption. PMMA allows for the inclusion of custom low-profile 3D (2.5D) structures for module assembly and mechanical alignment, a feature not possible in silicone due to its low rigidity. Both lenses suffer from thermal expansion and refractive index change. While PMMA parquets expand isotropically, SOG prisms deform due to the difference of expansion coefficients between the glass and the silicone. SOG lenses are prone to delamination of the silicone film. The adhesive strength of the film to the glass can be measured using a modified blister test that we developed. The results show large difference with different materials and confirm the necessity of controlling this issue closely. While the small thermal expansion of the glass sheets allows for larger parquet sizes, the deformation of the prisms with temperature may cause a performance hit.

This paper poses the question how statistically varying data should be handled while the output of modeled real-world systems is sometimes interpreted by human preference? It asks the question whether modeled data or realworld data are of greater importance. This question is asked in the context of what is more important, having a model that correctly predicts real-world energy generation or cost of a PV array or the "typical" generation or cost for such array? Real-world performance can only be predicted within some uncertainty level. Are good average or individual values obtained when the real-world energy output or cost of a single system are predicted? Two or more input factors into a single output will also often lead to increased variation. The point is made that greater accuracy of modeled and experimental data may or may not result in deeper insight into the generation capability of a solar array. The answer to the question posed in the title of this contribution is: Be as accurate as possible, but always expect variation in both the calculated and experimental results and be cognizant of the difference between typical and actual values.

Soldering of solar cell strings is a critical step in the production of photovoltaic modules. During the soldering process significant mechanical stresses are induced in the stringed cell assembly. Since silicon has a much smaller coefficient of thermal expansion than copper it is compressed by the copper-ribbon during the cooling phase. The resulting stresses can cause micro-cracks in the silicon cell, which are a major reason for cell breakage within the production line. Furthermore those stresses may lead to a delayed failure of the solder interconnections or cell cracking in the field. Therefore ribbon manufacturers try to create very soft ribbon material, which tends to be rather plastically deformed than generating stresses such that the silicon is prevented from damage. Nevertheless, the general tendency of using thinner wafers in cell production and the projected step towards the usage of lead-free solders increase the mechanical requirements on the cell interconnectors and make systematic scientific investigations inescapable. The purpose of this work is to analyze the micro-structure of ribbon in detail and to correlate it with its mechanical material behavior. An electron backscatter diffraction method was used to evaluate grain sizes and orientations in various annealing steps of the ribbon. These results were compared to their mechanical properties, achieved by conventional mechanical testing. As a result of these investigations the annealing process of the ribbon was optimized on laboratory scale to achieve highly adjusted material properties. Finally the benefit was verified by numerical simulation of the soldering process.

Fraunhofer ISE is running a PV-module outdoor testing set-up on the Gran Canaria island, one of the Canary Island located west of Morroco in the Atlantic Ocean. The performance of the modules is assessed by IV-curve monitoring every 10 minutes. The electronic set-up of the monitoring system - consisting of individual electronic loads for each module which go into an MPP-tracking mode between the IV-measurements - will be described in detail. Soiling of the exposed modules happened because of building constructions nearby. We decided not to clean the modules, but the radiation sensors and recorded the decrease of the power output and the efficiency over time. The efficiency dropped to 20 % within 5 months before a heavy rain and subsequently the service personnel on site cleaned the modules. A smaller rain-fall in between washed the dust partly away and accumulated it at the lower part of the module, what could be concluded from the shape of the IV-curves, which were similar to partial shading by hot-spot-tests and by partial snow cover.

Photovoltaic (PV) modules are periodically cleaned, particularly in large grid-connect photovoltaic plants, in order to avoid losses caused by dust accumulation. However, this maintenance task is often expensive, especially in those areas with water shortage. A hydrophilic coating on the surface of PV modules is one of typical methods to reduce the dust accumulation. But it is not commonly used yet, because the electrical performance of PV modules with conventional hydrophilic coating was slightly degraded by the decrease of transmittance. We have already developed a new hydrophilic power enhancement coating and reported its fundamental characters and results of several ISO/IEC standard tests in SPIE Solar Energy + Technology in 2010. One of the important characters was an antistatic effect. It was showed that the surface resistances of the coated glass and the uncoated glass were 1.3 × 1010Ω and 5.3 × 1014Ω, respectively. It would be understood that lower surface resistance of the coated glass resulted in the antistatic characteristics, which reduce the dust attraction on the coated glass. With the surface resistance result, it could be elucidated that the 3% additional energy production resulted from the antistatic effect of the coating on PV modules in the exposure test after several months without rain in Spain. In this paper, it is shown the results of the antistatic effect performed under the several dust accumulation tests.

In recent investigations using various analysis methods it has been shown that mechanical or thermal loading of PV modules leads to mechanical stress in the module parts and especially in the encapsulated solar cells. Cracks in crystalline solar cells are a characteristic defect that is caused by mechanical stress. They can lead to efficiency losses and lifetime reduction of the modules. This paper presents two experiments for systematic investigation of crack initiation and crack growth under thermal and mechanical loading using electroluminescence. For this purpose PV modules and laminated test specimens on smaller scales were produced including different cell types and module layouts. They were exposed to thermal cycling and to mechanical loading derived from the international standard IEC 61215. Cracks were observed mainly at the beginning and the end of the busbars and along the busbars. The cracks were analyzed and evaluated statistically. The experimental results are compared to results from numerical simulations to understand the reasons for the crack initiation and the observed crack growth and to allow module design optimization to reduce the mechanical stress.

The initial qualification standards for photovoltaic modules were designed to help develop a product that is safe, and able to survive reasonably long time periods when deployed in the field. To accomplish this, TC-82 of the International Electro-Technical Commission (IEC), developed and published module qualification standards (IEC 61215 for crystalline Si, IEC 61646 for thin films and IEC 62108 for concentrating modules) and a module safety standard (IEC 61730 -1 and 2). As PV has developed and the technology has become better understood, the properties of materials used in the module package play an increasingly important part in achieving long-term durability and safety. Certain basic properties are required of the materials in order for the modules to be safe and to be able to survive in the field for 25 years or more. Therefore Working Group 2 (Modules) of TC-82 began work to develop new material-level standards for PV that will utilize existing standards, whenever available, but tailored for characterizing the properties that are important for PV modules and modified to take into account the environmental conditions specific to PV applications. The goal is to provide a uniform approach to characterizing candidate materials, providing the necessary information to designers selecting materials for use in their PV products as well as to certification bodies assessing the quality and safety of the products made from these materials. This paper will describe the details of the effort underway to determine what PV material standards are necessary and the progress on developing those standards.

The aim of these investigations was to develop, implement and evaluate an appropriate procedure in order to qualify new polymeric components for the use in PV modules and to predict the lifetime of materials and modules. A test program concerning five accelerated artificial aging tests (varying UV, temperature and humidity levels) was set up and the degradation behavior of six polymers was investigated. Visual transmittance and strain-at-break were identified as most significant degradation indicators. A suitable material specific material degradation model was obtained, where changes of the material properties are accurately related to the applied environmental stresses. For the modeling of service life time the micro-climate, to which the encapsulation materials are exposed in a PV-module, was considered and reasonable end-of-life criteria were defined. Accelerated aging tests showed that effects of heat and humidity are dominating in optical properties, whereas changes in mechanical properties are equally effected by UV and humidity. An exact description of the micro-climate was found to be most critical for the accuracy of the material degradation model. For first qualification of the principal applicability of new materials both, a standard damp heat test and a UV test have to be done in order to validate all degradation effects properly.

It is known that one of the main functions of an encapsulation foil is to protect the module against external aging factors. But, what about the impact of the lamination foil itself on module reliability? In this study we will focus on EVA based lamination foils and the impact caused by some chemicals contained in such foils on the module performance. Special attention will be devoted to the effect of standard components like HALS (hindered amine light stabilizer), peroxides, UV blockers, the acidity of the master batch and different bulk EVA on reliability of thin film silicon modules. Due to environmental factors, free radicals can be formed inducing degradation effects. The impact on reliability will be studied.

The overall energy balance of a solar PV-module across its life time needs a consideration incl. its energy consumption during manufacturing process versus its energy harvesting capabilities during life time. A glass-glass-module based on thin tempered glass on front and backside can dramatically influence this overall balance, since more than 50 % of encapsulation materials manufacturing energy can be saved, followed by a an further impact on frameless mounting of light-weighted modules, reducing mounting costs and enabling simpler BIPV.

Moisture permeation is widely recognized as one of the most important causes of degradation in time of the performances of photovoltaic modules, especially thin film ones. B-Dry®i is a newly developed edge sealant tape which is able to block moisture penetration into PV modules for thousands of hours in Damp Heat Test (DHT) conditions, thanks to the presence of a getter material. Visco-elastic behavior, even at relatively high temperatures, makes B-Dry® especially suitable to guarantee mechanical stability of PV modules operating in hot and humid climates.

The characteristic properties of newly developed ionomer-based encapsulants are highlighted along with an in-depth analysis of moisture ingress, electrical and mechanical properties. The mechanical properties of these encapsulants with their high stiffness and strength have been found to allow the use of thinner glass and a possible shift from tempered to annealed glass. Lower-cost mounting options may be explored through full-module stress/deflection measurement capability and competencies developed in world-class finite-element modeling of system parameters. The superior electrical and moisture properties may allow modules to be produced without the use of an additional edge seal. These new materials have improved melt flow properties when compared to other encapsulant families such as EVA or PVB. This allows for faster processing which reduces production cost by shortening the lamination cycle. During the lamination process the sheets show excellent dimensional stability and low shrinkage behavior; and there is no need for curing, thus energy costs are lower due to lower lamination temperature. As advancement of technology proceeds across the entire PV industry, next generation ionomer encapsulants have been developed to keep up with the pace.

Accelerated testing of the durability of materials exposed to natural weathering requires testing of the UV stability, especially for polymeric materials. The type approval testing of PV-modules according to the standards IEC 61215 and IEC 61646 includes a so-called UV-preconditioning test with a total UV dose of 15 kWh/m². Fraunhofer ISE performed an Inter-laboratory comparison of UV-light sources in accredited test labs and in test centres of major PV module manufacturers. One topic was the spectral measurement of the used UV sources. Another main issue was the comparison of the integral measurements by the sensors used for control of the tests. Errors up to 120% were found.

Many photovoltaic modules are installed all around the world. However, the reliability of this product is not enough really known. The electrical power decreases in time due mainly to corrosion, encapsulation discoloration and solder bond failure. The failure of a photovoltaic module is obtained when the electrical power degradation reaches a threshold value. Accelerated life tests are commonly used to estimate the reliability of the photovoltaic module. However, using accelerated life tests, few data on the failure of this product are obtained and the realization of this kind of tests is expensive. As a solution, an accelerated degradation test can be carried out using only one stress if parameters of the acceleration model are known. The Wiener process associated with the accelerated failure time model permits to carry out many simulations and to determine the failure time distribution when the threshold value is reached. So, the failure time distribution and the lifetime (mean and uncertainty) can be evaluated.

We proposed an UV accelerated test condition for an EVA encapsulant, based on analysis of long term field exposed PV modules. We found that strong UV irradiation into EVA encapsulant test sample led to the fast decomposition of UV absorber formulated in EVA encapsulant, which has never seen in the field exposed PV modules. Thus, the integrating UV intensity of 60 W/m² and black panel temperature of 110°C using a xenon weather-o-meter were suitable as an UV accelerated test condition. With this proposed test condition, which shows that 1 week exposure by xenon light corresponds to 1 year field exposure, we can predict discoloration rate of EVA encapsulant. In addition, we evaluated change in peel strength to glass for Mitsui's and the other commercially available EVA encapsulants during UV accelerated test with the proposed condition. There was no large change in peel strength for our EVA encapsulant during the UV accelerated test. On the other hand, we observed that the competitor's EVA encapsulant showed the large decrease of peel strength to glass at early stage, even no change in yellowness index (YI). This result indicates not only YI change but also peel strength change should be evaluated for design of reliable PV module and encapsulant.

In Japan, because both the government and PV industries have not been interested in operation and maintenance of PV system, almost all the PV users, number of which may be over 500,000, never knows troubles and/or risks which may happen to their PV systems during long-term operation. In 2006, author started "PVRessQ! (PV - Reliable, Safe and Sustainable Quality!)" activity in Japan. This activity has two action items: 1) field survey of existing residential PV systems to find troubles/failures and 2) statistical analysis by collecting trouble records from the PV users. In this paper, recent topics from this activity are introduced.

Traditional degradation or reliability analysis of photovoltaic (PV) modules has historically consisted of some combination of accelerated stress and field testing, including field deployment and monitoring of modules over long time periods, and analyzing commercial warranty returns. This has been effective in identifying failure mechanisms and developing stress tests that accelerate those failures. For example, BP Solar assessed the long term reliability of modules deployed outdoor and modules returned from the field in 2003; and presented the types of failures observed. Out of about 2 million modules, the total number of returns over nine year period was only 0.13%. An analysis on these returns resulted that 86% of the field failures were due to corrosion and cell or interconnect break. These failures were eliminated through extended thermal cycling and damp heat tests. Considering that these failures are observed even on modules that have successfully gone through conventional qualification tests, it is possible that known failure modes and mechanisms are not well understood. Moreover, when a defect is not easily identifiable, the existing accelerated tests might no longer be sufficient. Thus, a detailed study of all known failure modes existed in field test is essential. In this paper, we combine the physics of failure analysis with an empirical study of the field inspection data of PV modules deployed in Arizona to develop a FMECA model. This technique examines the failure rates of individual components of fielded modules, along with their severities and detectabilities, to determine the overall effect of a defect on the module's quality and reliability.

The levelized cost of energy (LCOE) from PV systems can be reduced by maximizing the energy production of existing/future PV plants through increased availability. This can be achieved by detailed study of root cause and failure analysis of component failures leading to a systematic progress towards improving the reliability of various sub-systems. SunEdison owns/operates ~500 sites across the world and systematically collects field failure data in addition to power output and weather data. Analysis of this information allows following-up on corrective actions to eliminate/minimize the re-occurrence of failures and leads to continuous improvements. This paper will analyze some of the key findings from the system failures as follows: - Inverter failures not only cause most of the system outages, but also result in substantial energy losses. Component failures in PCBs and inverter software/firmware bugs are the most common root cause of system outages - From a systemic root cause perspective, lack of robust quality systems at multiple levels of the supply chain is quite evident, which points toward the need for collectively inculcating the quality culture at every stage of the supply chain - This paper will try to establish the need for "Continuous Improvement Process" (CIP) where systemic issues are confronted and solutions are internalized in the operating procedures as the only path to improving component reliability - For a given level of reliability, cost associated with servicing the plant becomes critical. This paper highlights the importance of using "cost of ownership" metrics for making procurement decisions

The accelerated tests currently carried out on PV modules reduce the infant mortality as well as improve the production techniques during the manufacture of PV modules. However, the accelerated tests do not completely duplicate the real world operating conditions of PV modules. Hence it is essential to deploy PV modules in the field for extended periods in order to estimate the degradation, if any, as well as to elucidate the degradation mechanisms. Moreover, PV modules should be tested by specially designed tests in harsh climates. At Florida Solar Energy Center (FSEC) high-voltage bias testing of PV modules was carried out in hot and humid climate with the individual modules biased at +/- 600 V. It was observed that the leakage currents flowing from the PV circuit to the ground is directly proportional to the bias voltage. PV systems with maximum voltage of 1000 V are installed in Europe and elsewhere which means higher leakage currents will be produced in the PV modules. Based on this fact and the earlier observations, high voltage bias testing of c-Si PV modules specially designed for high voltage operation was carried out in hot and humid climate with the individual modules biased at +/-1500 V at FSEC and higher. This paper provides results of high voltage bias testing of PV modules. The results indicate that the test can be considered as reliable metric in determination of the long term performance of PV modules.

The crystalline silicon photovoltaic (PV) modules under open circuit conditions typically degrade at a rate of about 0.5% per year. However, it is suspected that the modules in an array level may degrade, depending on equipment/frame grounding and array grounding, at higher rates because of higher string voltage and increased module mismatch over the years of operation in the field. This paper compares and analyzes the degradation rates of grid-tied photovoltaic modules operating over 10-17 years in a desert climatic condition of Arizona. The nameplate open-circuit voltages of the arrays ranged between 400 and 450 V. Six different types/models of crystalline silicon modules with glass/glass and glass/polymer constructions were evaluated. About 1865 modules were inspected using an extended visual inspection checklist and infrared (IR) scanning. The visual inspection checklist included encapsulant discoloration, cell/interconnect cracks, delamination and corrosion. Based on the visual inspection and IR studies, a large fraction of these modules were identified as allegedly healthy and unhealthy modules and they were electrically isolated from the system for currentvoltage (I-V) measurements of individual modules. The annual degradation rate for each module type is determined based on the I-V measurements.

Photovoltaic modules are usually considered safe and reliable. But in case of grid-connected PV systems that are becoming very popular, the issue of fire safety of PV modules is becoming increasingly important due to the employed high voltages of 600 V to 1000 V. The two main factors i.e. open circuiting of the bypass diode and ground fault that are responsible for the fire in the PV systems have been discussed in detail along with numerous real life examples. Recommendations are provided for preventing the fire hazards such as having at least class C fire rated PV modules, proper bypass and blocking diodes and interestingly, having an ungrounded PV system.

Current accelerated qualification tests of photovoltaic (PV) modules mostly assist in avoiding infant mortality but can neither duplicate changes occurring in the field nor can predict useful lifetime. Therefore, outdoor monitoring of fielddeployed thin-film PV modules was undertaken at FSEC with goals of assessing their performance in hot and humid climate under high system voltage operation and to correlate the PV performance with the meteorological parameters. Significant and comparable degradation rate of -5.13% and -4.5% per year was found by PV USA type regression analysis for the positive and negative strings respectively of 40W glass-to-glass CIGS thin-film PV modules in the hot and humid climate of Florida. With the current-voltage measurements it was found that the performance degradation within the PV array was mainly due to a few (8-12%) modules having a substantially high degradation. The remaining modules within the array continued to show reasonable performance (>96% of the rated power after ~ 4years).

This work evaluated the capability of (electrochemical) impedance spectroscopy (IS, or ECIS as used here) to monitor damp heat (DH) stability of contact materials, CuInGaSe2 (CIGS) solar cell components, and devices. Cell characteristics and its variation of the CIGS devices were also examined by the ECIS. Bare and encapsulated sample sets were separately prepared and exposed in an environmental chamber at 85°C and 85% relative humidity (RH). The ECIS results from bare samples tested within 50-100 h of DH exposure allowed the determination of the use of a conducting Ag paste and a low-melting-point solder alloy for making a DH-stable external connection with Au wires. Bare Mo and AlNi grid degraded (corroded) rapidly while Ni was DH-stable. The moisture-dampened Al-doped ZnO (AZO) and bilayer ZnO (BZO) likely underwent hydrolytic "capacitor-forming" reaction by DH, resulting in "transient" behavior of very high resistance in ECIS that was not detected by four-point probe. Using an encapsulation test structure that allowed moisture ingress control, DH-induced degradation (resistance increase) rates of BZO on glass decreased from 0.21 ohm/h using a moisture-permeable Tedlar/Polyester/Tedlar (TPT) backsheet to 1.0 x 10^-3 ohm/h using a moisture barrier FG-200 film, while Mo on glass did not exhibit the same conducting degradation and corrosion as the bare samples after over 1270 h DH exposure. CIGS solar cells encapsulated with a TPT backsheet degraded irregularly over 774 h DH exposure. Key resistance and capacitance parameters extracted by curve fitting of impedance data clearly showed the variation and impact of DH exposure on cell characteristics. Profound "depression" or shorting of the "p-n junction capacitor" by DH was evident. ECIS results are shown to correlate reasonably well with the solar cells' currentvoltage (I-V) degrading trends. Furthermore, ECIS analysis was capable of differentiating cell degradation due to "junction capacitor" shorting, damage or breakdown from that due to electrical conduction failure on AlNi/BZO layers.

The significant features of a series of stabilization experiments conducted at the National Renewable Energy Laboratory (NREL) between May 2009 and the present are reported. These experiments evaluated a procedure to stabilize the measured performance of thin-film polycrystalline cadmium telluride (CdTe) and copper indium gallium diselenide (CIGS) thin-film photovoltaic (PV) modules. The current-voltage (I-V) characteristics of CdTe and CIGS thin-film PV devices and modules exhibit transitory changes in electrical performance after thermal exposure in the dark and/or bias and light exposures. We present the results of our case studies of module performance versus exposure: light-soaked at 65°C; exposed in the dark under forward bias at 65°C; and, finally, longer-term outdoor exposure. We find that stabilization can be achieved to varying degrees using either light-soaking or dark bias methods and that the existing IEC 61646 light-soaking interval may be appropriate for CdTe and CIGS modules with one caveat: it is likely that at least three exposure intervals are required for stabilization.

A new data mining algorithm was developed to identify the strongest correlations between capacitance data (measured between -1.5 V and +0.49 V) and first- and second-level performance metrics (efficiency [η%], open-circuit voltage [V_OC], short-circuit current density [J_SC], and fill-factor [FF]) during the stress testing of voltage-stabilized CdS/CdTe devices. When considering only correlations between first- and second-level metrics, 96.5% of the observed variation in η% was attributed to FF. The overall decrease in V_OC after 1,000 hours of open-circuit, light-soak stress at 60°C was about -1.5%. As determined by our algorithm, the most consistent correlation existing between FF and third-level metric capacitance data at all stages during stress testing was between FF and the apparent CdTe acceptor density (N_a) calculated at a voltage of +0.49 V during forward voltage scans. Since the contribution of back-contact capacitance to total capacitance increases with increasing positive voltage, this result suggests that FF degradation is associated with decreases in N_a near the CdTe/back contact interface. Also of interest, it appears that capacitance data at these higher voltages appears to more accurately fit the one-sided abrupt junction model.

As new methods to test degradation of c-Si single-cell PV modules, we carried out both reverse bias constant current (RBCC) test and IV duty cycle (IVDC) test under different loading levels, that is, input power to the cell. The common failure modes of field PV modules, such as finger electrodes discoloration, inflated back sheet, and burnt back sheet in the modules, were observed. It was found that cell's series resistance (Rs) increases approximately linearly with testing time, and the rate of change of Rs increased exponentially corresponding to the loading level. In the RBCC test, it was also found that cell's shunt resistance (Rsh) decayed exponentially with time, and then it approaches to constant value. Furthermore, threshold level for occurrence of breakdown breakage of the cells was found to be about 70 to 80 watt. The methods presented here demonstrated the possibility of applying the reverse bias test for degradation of c-Si single-cell PV modules.

Microbial fuel cell (MFC) technologies represent the newest approach for generating electricity - bioelectricity generation from biomass using bacteria. Desulfuromonas acetoxidans are aquatic obligatory anaerobic sulfur-reducing bacteria that possess an ability to produce electric current in the processes of organic matter oxidation and Fe³⁺- or Mn⁴⁺- reduction. These are pattern objects for MFC systems. They could be applied as a highly effective and self-sustaining model of wastewater treatment which contains energy in the form of biodegradable organic matter. But wastewaters contain high concentrations of xenobiotics, such as different heavy metals that have a detrimental effect towards all living organisms. The influence of different concentrations of MnCl₂×4H₂O, FeSO₄ CuSO₄, CdSO₄, ZnSO₄ and PbNO₃ on light scattering properties of aquatic D. acetoxidans bacteria on the base of their cells' size distribution and relative content has been investigated by the new method of measurement. The cell distribution curve was in the range of 0.4 - 1.4 μm. The most crucial changes of cell concentration dependences, compared with other investigated metal ions, have been observed under the influence of copper ions. The ability of D. acetoxidans bacteria to produce electric current upon the specific cultivation conditions and the influence of Fe²⁺ and Mn²⁺ has been verified.

The implementation of a photovoltaic and an electronic module that manages the energy improves the flight time and the autonomy performance in an UAV. The module consists in a device that tracking the maximum power point of PV module by a PWM current-voltage regulation to charge a Li-Po battery. Characterization and modeling of crystalline and amorphous solar cells has been made. Our simulation estimates speed of battery charge. As a result, we increase the autonomy of the battery charge which is reflected in a UAV that performs tasks in fewer flights and without human supervision.