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Renewable energy-based generators are constantly being deployed to future grids. It is expected that their share in overall generation will increase in the future. These novel devices have unknown characteristics and cause novel issues in power system operation. Traditional distribution networks have been operated as passive networks. These devices, such as smart inverters, change this paradigm completely. Due to these considerations, grid operators insist on enforcing strict grid-integration requirements. These rules are developed to ensure the impact of the connected devices is minimized and their behavior can be accounted for, at least to some extent. Testing different devices for different grid codes is a daunting task. Since such tests are undertaken in lab environment with manual control and data collection, they are prone to errors, time-consuming and inefficient. A solution is required to standardize and automate such tests. This will provide consistent testing ability and minimize testing times and errors due to human-intervention. This article presents the design and implementation of an integrated testing platform. Steps of lab equipment integration and associated challenges are presented along with their solutions. Several smart inverter behavior tests are executed, and results are presented. The test durations are compared with traditional test durations and the benefits are reported. It is discovered that use of such platform can increase the system testing efficiency by 85 % while minimizing human-errors, inconsistencies and man-hours required to run the tests.

The power hardware-in-the-loop (PHIL) simulation has become a popular testing approach due to the flexibility it provides and the high-fidelity of its results. It is expected to be utilized as an advanced laboratory testing scheme to validate the grid support functions of distributed energy resources (DERs) because it can evaluate the interaction between the power system and DERs. Despite the strong demand to utilize the PHIL simulation for such testing, the literature that elaborates on the practical design of PHIL simulation based testing (hereafter called “PHIL testing”) environment including laboratory device setup, power system models, and test procedures is very limited. The simulation models, interfacing with the tested equipment, and data collection approaches are all different parameters that need to be fine-tuned for the successful execution of PHIL testing. It is vital for such successful test experiences to be shared to build universal knowledge around PHIL testing. In order to fill this knowledge gap, this paper presents such practical and essential techniques for the PHIL testing to share the knowledge for promotion of the PHIL simulation utilization. The development of PHIL testing environment to validate the smart inverter functions, i.e., volt-var function and frequency-watt function, is focused on in terms of laboratory setup, power system modeling, interfacing, and test procedure. The volt-var and frequency-watt functions of a 500 kW smart inverter of photovoltaic are validated on the basis of the presented techniques. Detailed test configurations, test procedures, and simulation models are presented along with obtained test results.

The high penetration of the distributed energy resources (DERs) encourages themselves to implement grid-supporting functions, such as volt-var control. The quasi-static time-series (QSTS) simulation is an essential technique to evaluate the impact of active DERs on the grid. Meanwhile, the increase of complexity on the circuit model causes a heavy computational burden of QSTS simulation. Although circuit reduction methods have been proposed, there have been few methods that can appropriately handle the distribution system (DS) with multiple voltage control devices, such as DERs implementing volt-var control. To address the remaining issues, this paper proposes an offline bus aggregation method for DS with volt-var control. The method determines the volt-var curve for the aggregated bus on the basis of historical data to reduce error in the aggregated model, and its offline process solves the computational convergence issue concerned in the online one. The effectiveness of the proposed method is validated in the simulation using a Japanese low-voltage DS model. The simulation results show that the proposed method can reduce the voltage error and computational time. Furthermore, the versatility of the proposed method is verified to show the performance does not heavily depend on how to select historical data for model-building.

Penetration of renewable energy based distributed generators into power networks is limited. This is due to several reasons such as intermittency of the generation, low-inertia during disturbances and high variation of local voltage and frequency. Traditionally, distribution networks are designed for a finite voltage drop with distance from feeder connection. When PV panels are deployed at households, their impact on the local voltage profile becomes very substantial. Especially, when there is high solar radiation, generated power increases and the local voltage exceeds the permittable limits. Smart inverters are introduced to tackle this problem. Unlike other inverters, they can follow the local network measurements and provide auxiliary voltage and frequency support. With these features, smart inverters have the ability to push the renewable energy penetration level further. To investigate this phenomenon, custom smart inverter models are developed. Power flow calculation steps are modified to include smart inverter's active inputs. Then, feeder hosting capacity studies were run with conventional and smart inverters to investigate the improvement. Developed models, modified power flow algorithm and results of simulations are reported. Findings show renewable energy share can be increased in networks with smart inverter deployments only, without making substantial changes to rest of the network.

Grid codes around the world are requiring grid-support functions (GSFs) and standardized interoperability interfaces for distributed energy resources (DERs) to address the rapid increase of renewable energy. However, these new GSFs need to be assessed to ensure the desired power and communication capabilities exist in the field. The IEEE 1547.1 standard outlines the conformance test procedures for DER devices and is currently undergoing a major revision to align it with IEEE 1547–2018. Once it is published (anticipated in mid-2020), GSFs in commercial PV inverters in USA and Canada will be certified to the IEEE 1547.1 conformance test procedures. Several international research laboratories are collaborating to develop a versatile open-source DER testing platform that performs automated testing of DER devices. This community of laboratories is developing open-source IEEE Std. 1547.1 test scripts to lower barriers to DER vendor internal equipment evaluations, ease product compliance testing at certification laboratories, and provide research institutions a tool to study DER behaviors. In this work, test scripts were used for test verification of GSFs, including limit active power, constant reactive power, active power-reactive power (watt-var), and prioritization of GSF response for several DER devices. Sample test results for these DER GSFs and test protocol recommendations are presented in this paper.

High penetration of renewable energy based distributed generators is a common goal for many electricity companies. While providing clean and cheap energy on the one hand, these active components create unprecedented problems in the grid. Arguably the most prominent one is causing unacceptable voltage rises due to power injection. Traditional solution is to cap the renewable energy generation. This turns into a double loss as the available energy is not captured and the installed equipment is not fully utilized. Introduction of smart inverters is aimed at solving these intertwined concepts. Impact of smart inverters on the distribution network operation has been recently reported in the literature. However, multiple smart inverter operation where several devices try to influence the power flow has not been thoroughly investigated. This paper focuses on analyzing the operation of several smart inverters that are running in Volt-Var mode and are connected to the same distribution feeder. Furthermore, considering the number of roof-top PVs in neighborhoods and the difficulty in simulating the individually, a simplification method is developed. In this fashion, multiple smart inverters operating in the same feeder are modeled in an aggregated way for easier calculation. Finally, simulation results are presented for analysis and validation.

As the number of distributed energy resources (DERs) increase, power systems become harder to control. To harmonize the traditional system and such novel technologies, the holistic comprehension of the integrated system is necessary. Microgrid, which can be used to electrify isolated communities in sub-Saharan Africa or small islands in the Pacific Ocean, is one of the application destinations of the novel technologies. The renewable-energy based DERs are suitable for the microgrid operation because they can be set up with a small capital and utilized at a small scale. However, renewable energy is intermittent and time-dependent. To achieve reliable and continuous supply of energy, a generation portfolio including different generators needs to be created so that they can balance each other. This requires the use of a sophisticated control system in the microgrid. Operation of these control need to be validated before actual deployment. In this paper, a commercial microgrid controller is tested in an integrated test environment. Test environment in the lab is utilized to set up a microgrid and hardware-in-the-loop (HIL) test is added to simulate additional conditions. Testing with real hardware equipment increases the fidelity of the test results while real-time simulation adds to the diversity. Such validation is crucial to the project’s success before on-site deployment.

Deep penetration of distributed generators have created several stability and operation issues for power systems. In order to address these, inverters with advanced capabilities such as frequency and reactive power support the grid. Known also as Smart Inverters (SIs), these devices are highly dynamic and contribute to the power flow in the system. Notwithstanding their benefits, such dynamic devices are new to distribution networks. Power system operators are very reluctant toward such changes as they may cause unknown issues. In order to alleviate these concerns and facilitate SIs integration to the grid, behavior studies are required. To that end, this paper presents a power hardware-in-the-loop test set up and tests that are performed to study fault behavior of SIs connected to distribution networks. The details of the software model, SI integration with the real-time simulator, test results, and their analyses are presented. This experience shows that it is not trivial to connect such novel devices with simulation environments. Adjustments are required on both software and hardware fronts on a case-by-case basis. The encountered integration issues and their solutions are presented herein. The fault behavior of the SI with respect to the fault location is documented. It is observed that for faults that are close to SIs, momentary cessation of generation is observed. This needs to be tackled by device manufacturers as this phenomenon is very detrimental to health of a power system under fault conditions. Extensive PHIL test results show that several factors affect the fault behavior of an SI: fault location and its duration, SI mode of operation as well as extra devices housed in the casing. These results and their in-depth analyses are presented for a thorough understanding of SI behavior under fault conditions.

In order to make effective use of PV-PCSs and battery storage PCSs, it is important to develop and evaluate behaviors in power system, grid interconnection, their control and protection equipment, etc. A HILS (Hardware in the Loop Simulation) test facility was developed for these purposes which was consisted in combination with real-time simulator and actual hardware of their PCSs. RTDS of RTDS Technologies Inc. for real-time simulator, MX 30 of AMETEK Inc. as a signal amplifier of RTDS analysis results and the SMA 20 kW PCS for actual hardware were used for the HILS test facility. In the simulation, power system included PV-PCS is simulated by the RSCAD which is an exclusive software of RTDS. A dynamic PQ source model provided in the RSCAD library was used instead of the actual PCS model. AC voltages Vac and AC currents Iac are detected from the actual PCS and feedback to the RTDS. In the simulation program, we calculate instantanious real power P and reactive power Q in real time using Vac and Iac in order to set as a command of the dynamic PQ source model. For the HILS test, we analyzed behaviors of the PV-PCS during grid faults. And the results were compared with off-line simulation using a PV model provided in the RSCAD library.

Although it is very popular among environmentalists, the replacement of fossil-fuel based generation with new age renewable energy (RE) creates problems in grid operation and stability. The intermittent nature of these resources as well as their inverter-based connection structure hinder the traditional operation of electrical networks. Consequently, the RE penetration level has been kept low to limit their impact on the infrastructure. In order to maximize RE potential, novel solutions are required and smart inverters with advanced inverter capabilities can be just that. Coupled with battery energy storage systems (BESS), they can manage RE intermittent behavior and provide auxiliary services such as frequency and voltage support. However, large scale deployment of these power conditioning systems (PCS) at distribution level can create enormous problems. To cope with this challenge, their behavior should be closely scrutinized and interoperable operation must be guaranteed with a series of tests before actual deployment. Smart Grid International Research Facility Network (SIRFN) has the services of 15 distinct labs to develop standard testing protocols and knowledge on best practices. A consortium of labs around the globe ran tests in their facilities and developed standard testing procedures for BESS. Building on that experience, IEEE P2004 project aims at developing standard hardware-in-the-loop (HIL) testing procedures for PCS. This will improve the testing capabilities since different systems can be easily modeled and verified in HIL. This paper documents these standardized testing efforts and the role of Fukushima Renewable Energy Institute, a part of SIRFN and IEEE P2004, in achieving these goals.

The purpose of this study is to investigate concentrator photovoltaic (CPV) system performance. The performance of the CPV system depends on the climate and the environment condition more than the conventional flat-plate photovoltaic (PV) system. Moreover, the characteristic due to the angle of incidence (AOI) solar irradiance is extremely important. Therefore, the grid-connected PV and CPV systems installed in Japan are investigated to clarify these performance issues in this paper. The performance analysis results including performance ratio and alignment and tracking error data from one year of operation are presented and discussed.

Nowadays, investors, customers, and even suppliers focus on the bankability of photovoltaic (PV) technologies. However, few studies have investigated the annual net effect of solar spectrum. In this study, we estimate the net effect of the solar spectrum on the annual energy yield of c-Si and a-Si modules by two parameters. One parameter is a direct calculation from spectral factor (SF). The other parameter uses average photon energy (APE) and a regression line or curve. The estimations by the two parameters are quite consistent, whereas there is 1.2% difference between the estimations at most. Therefore, APE would be a useful index to quantify the effect of the solar spectrum.

The performance of photovoltaic (PV) modules is generally rated under standard test conditions (STC). However, the performance of thin-film photovoltaic modules is not unique even under STC, because of the “metastability”. The effects of the light soaking and thermal annealing shall be incorporated into an appropriate energy rating standard. In this study, the change in I–V characteristics of thin-film PV modules caused by the metastability was examined by repeated indoor measurements in addition to round-robin outdoor measurements. The investigated thin-film modules were copper indium gallium (di)selenide (CIGS), a-Si : H, and a-Si : H/µc-Si : H (tandem) modules. The increase in the performance of the CIGS module between the initial and final indoor measurements was approximately 8%. Because of light-induced degradation, the indoor performance of the a-Si : H and a-Si : H/µc-Si : H modules decreased by approximately 35% and 20%, respectively. The performance was improved by about 4–6% under high temperature conditions after the initial degradation. The results suggest that the performance of thin-film silicon modules can seasonally vary by approximately 4–6% only due to thermal annealing and light soaking effects. The effect of solar spectrum enhanced the outdoor performance of the a-Si : H module by about 10% under low air mass conditions, although that of the a-Si : H/µc-Si : H modules showed a little increase. The currents of these a-Si : H/µc-Si : H modules may be limited by the bottom cells. Therefore, it is required to optimize the effect of solar spectrum in addition to the effects of light soaking and thermal annealing, in order to achieve the best performance for thin-film silicon tandem modules. Copyright © 2013 John Wiley & Sons, Ltd.

In recent years, several large-scale solar power plants, called mega solar power plants, have been built at various locations. Inspection of a faulty solar panel is important for the maintenance of solar panels. However, previous methods of determining a fault in a solar panel required removal of panels from the solar power plant. In this paper, a cooperative robot system using wire-parallel mechanism is proposed for the realization of on-site inspection. Based on Vector-Closure and manipulability, the design of the system is described.

Photovoltaic (PV) systems have become popular globally as an important candidate in the establishment of low-carbon electrical and civil systems. Since the early 1990s, globally, many PV systems have been installed, and their performance parameters such as annual yield, performance ratio, and system losses have been monitored in order to understand their basic characteristics; these data also help in the development of these systems and in analyzing their reliability. In Japan, the performance of residential PV systems was evaluated and reported. However, these evaluations were carried out using older systems, and the current status and the performance trend for each installation year have not been sufficiently evaluated and discussed. Therefore, this report aims to provide a macroscopic evaluation of the performance trends of PV systems by using the monitoring data of systems that were installed between the year 2000 and the year 2007. As a result of the evaluation, we have concluded that the performance ratio of these systems improved to an average of 0.72 until fiscal year 2000 and to 0.78 after fiscal year 2001. For investigating the factors behind this increase in performance ratio, we have focused on characteristics of the actual system capacity (capacity of each PV module measured at the point of shipment) and inverter efficiency. Copyright © 2010 John Wiley & Sons, Ltd.

The performance of six photovoltaic (PV) modules composed of polycrystalline silicon (pc-Si), amorphous silicon (a-Si), and hydrogenated amorphous silicon/crystalline silicon (a-Si:H/c-Si) modules was investigated at eight locations in Japan from August 2007 to December 2008. In addition, solar irradiance, solar spectrum, and module temperature were simultaneously measured in these round-robin measurements. In this study, we evaluate quantitatively the effects of module temperature and solar spectrum on the performance of the PV modules as thermal factor (TF) and spectral factor (SF), respectively. Furthermore, we investigate the variation in module performance, which is converted into module performance under standard test conditions (STC) using the TF and SF. In the case of the pc-Si modules, the variations in performance ratio under STC (PRSTC) for these modules range from 0.056 to 0.074 through the round-robin measurements. The TF indicates that the contribution of module temperature to the variation in performance is large, between about 15 and 20%. However, the SF suggests that the contribution of solar spectrum is quite small, less than 3%. In the case of the a-Si modules, the contribution of module temperature is about 8%. The performance is largely influenced by solar spectrum, more than 12% at its maximum. Consequently, the variations in the corrected PRSTC of the a-Si modules are between 0.117 and 0.141. These large variations may result from the effects of thermal annealing and light soaking. The variation in PRSTC of the a-Si:H/c-Si module is similar to that of the pc-Si modules. Copyright © 2010 John Wiley & Sons, Ltd.

In order to disseminate Photovoltaic (PV) technologies into the energy network, the cost down is not only important, but also improving the performance of the PV system is significant issues. Long-term reliability is one of the most important issues in terms of PV system performance. Previous researches were mainly focused on the reliability of PV modules, but the PV system is composed of a power conditioner, wiring, junction box, and so on. To improve the reliability of PV systems, it is important to accumulate trouble cases focused on all components of PV system. In this paper, we aim at evaluation of the reliability for the PV system on the early stages of PV system's lifetime by using large number of Japanese PV systems' data from the field Test in Japan. New Energy and Industrial Technology Development Organization has been running the “Field test project in Japan” from 1992. In this project, PV system users have cooperated with the collection of monitoring data and reported on the information of maintenance and certain failures of PV systems for 4 years after installation of PV system. Using those reports each year of installation, we evaluated reliability of PV systems by means of parameters such as Mean Time Between Failure, Mean Time To Repair, and the suspension time of PV system. As a result, the main trouble of PV systems was related power conditioner, and a few trouble of PV module was caused by typhoon. Moreover, the trend of the failure rate before FY 2000 of installation was demonstrated as the trend of initial failure in “bathtub curve;” however, the trend of its after FY 2001 of installation was indicated as the accidental failure in “bathtub curve.” Further, the operator simply forgot to restart the power conditioner after maintenance or suspensions of PV system in many trouble cases, and the user did not notice that it had been suspended for a while. These trouble cases can be avoidable easily through the effective alarm such as error message of power conditioner systems with monitoring systems. Thereby, monitoring with the evaluation method of PV systems is one of the important technologies due to the long-term reliability and stable operation. Copyright © 2010 John Wiley & Sons, Ltd.

The largest output fluctuation is an index used to quantify the disturbance of a power grid caused by wind power plants and photovoltaic power generation systems connected to it. In order to develop its estimation method, we investigate the relationship between the largest output fluctuation and the standard deviation of a newly proposed random variable generated by differencing the output variation of photovoltaic power generation systems. Output fluctuation coefficients are defined and estimated using measured data of photovoltaic power generation systems located at 52 places. An approximation equation is presented to predict geographical correlations between the proposed random variables for photovoltaic power systems by using the distances between their locations. Finally, it is shown that the largest output fluctuation of many photovoltaic power generation systems dispersed in a wide area is predictable by using the output fluctuation coefficients and the equation approximating the geographical correlations of output fluctuations. ©2008 Wiley Periodicals, Inc. Electr Eng Jpn, 166(4): 9–19, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20723

The largest output fluctuation is an index used to quantify disturbance against a power grid caused by wind power plants and photovoltaic power generation systems connected to it. To develop its estimation method, we investigate the relationship between the largest output fluctuation and the standard deviation of a newly proposed stochastic variable derived from the output variation of photovoltaic power generation systems. Output fluctuation coefficients are defined and estimated using the measured data of photovoltaic power generation systems located at 52 places. An approximation formula is presented to predict correlation factors between the stochastic variables corresponding to photovoltaic power generation systems using distances between their locations. Finally it is shown that the largest output fluctuation of many photovoltaic power generation systems dispersed in a wide area is predictable by using the output fluctuation coefficients and the formula to approximate the correlation factors.

Short-time fluctuations in solar irradiance will become an important issue with regard to future embedded photovoltaic (PV) systems. However, when PV systems are intensively installed, fluctuation of total output in clustered PV systems is not remarkable because there is the smoothing effect of irradiance in certain areas. In this paper, a new estimation method of irradiance fluctuation, which is based on the combination of the Fourier transform and the wavelet transform methods, is described.

Here, we present the results of evaluation of solar energy potential and photovoltaic (PV) module performance from actual data measured over a period of more than 2 years in the Gobi Desert of Mongolia. To allow estimation of solar energy potentials and durability of PV systems in the Gobi Desert area, a data acquisition system, including crystalline silicon (c-Si), polycrystalline silicon (p-Si) modules, and two sets of precision pyranometers, thermometers, and anemometer, was installed at Sainshand City in October 2002. This system measures 23 parameters, including solar irradiation and meteorological parameters, every 10 min. High output gain was observed due to operation at extremely low ambient temperatures and the module performance ratios (PRs) were high (>1·0) in winter. In summary, the present study showed that a PV module with a high temperature coefficient, such as crystalline silicon, is advantageous for use in the Gobi Desert area. Copyright © 2006 John Wiley & Sons, Ltd.

To develop a new formula for calculating irradiation onto an arbitrary orientation–inclination plane, detailed examinations have been made by using data obtained at every 1 min interval with four types of pyranometer, such as horizontal, diffuse, direct normal, and tilt global. Instantaneous irradiance values sampled with 1 min interval have been verified by clearness index, which is a parameter independent of the lapse of time. Scattered tendencies observed on direct and diffused component ratios have been studied in detail by classifying data into different classes of clearness indices. In our model, moving averages of time-series irradiance data provide the information of weather condition in order to select model parameters prepared for assumed three types of clouds conditions. Only global irradiance data monitored at 1 min intervals are used for the input of the model. The result of this work demonstrates that an algorithm associated with the Perez model can estimate the in-plane irradiation with a RMSE of about 50 W/m 2 .

This paper describes the methods for forecasting solar irradiance by using geostationary meteorological satellite (GMS) images. As the first attempt the authors forecasted the cloud albedo for a basic study of irradiance estimation by estimating the driving drift vector of clouds using GMS images. A new procedure is also proposed for removing the effect of ground albedo, which disturbs cloud movement analysis. This time, annual forecastable probability was estimated as 81.3% for 1 h ahead, 71.0% for 2 h ahead and 59.3% for 3 h ahead.

This paper describes the method for forecasting the cloud albedo as a basis study to estimate the irradiation by using geostationary meteorological satellite (GMS) images. A new procedure is also proposed to remove the effect of ground albedo, which disturbs the cloud movement analysis. The validity of the method for forecasting the cloud albedo was examined. The forecast probability was estimated as yearly 66.8% for one hour ahead, 58.5% for two hours ahead and 52.7% for three hours ahead at 20 sites in Japan. Results over 80% for one hour ahead at Sapporo were obtained. It seems reasonable to suppose that this method can be used only for a specific site and season.

Performance of III-V multi-junction solar cells depends on spectral conditions according to which junction limits the photocurrent. Specifically, the response of concentrating multi-junction solar cells depends on the illumination at the cell surface. Because the illumination condition depends on alignment, it is important to characterize the CPV performance not only for a mono-module but also for a system or an array. In this paper the spectral effect on the CPV system and the mono-module consisting of III-V multi-junction solar cells from three different manufactures will be discussed.

PV customers wish to have confidence in PV modules they purchase. Today, no test can quantify a module’s lifetime with confidence, but stress tests are routinely used to differentiate PV product designs. We suggest that the industry would be strengthened by using the wisdom of the community to develop a single set of tests that will help customers quantify confidence in PV products. This paper evaluates the need for quality assurance (QA) standards and suggests a path for creating these. Two types of standards are needed: 1) QA of the module design and 2) QA of the manufacturing process., JRC.F.7-Renewable Energy

This paper presents the evaluation results of a long-term performance of 2 type PV module from actual data measured over a period of more than 6 years in the Gobi Desert of Mongolia. For the purpose of estimating solar energy potentials and durability of PV systems in the Gobi desert area, a data acquisition system, which includes crystalline silicon (c-Si), polycrystalline silicon (p-Si) modules and precision pyranometer, thermometer and anemometer, have been installed at the Sainshand city in October, 2002. This system has been measuring 23 parameters including solar irradiation and meteorological parameters in every 10 minutes. It has been observed that the high output gain due to the operating condition in an extreme low ambient temperature and the PV module degradation rate indicated over −1.5[%/yr] after 6 years exposure test.

This paper presents the results of a long-term performance analysis of PV-hybrid system based on 5 years operational data from the field site of Noyon soum, Umnugobi province, Mongolia, project supported by New Energy and Industrial Technology Development Organization of Japan (NEDO). The NEDO has performed demonstrative research on the independent dispersed PV-hybrid systems: PV, 200kW, DEG (Diesel Engine Generator): 100kVA*3set) from 2002 to 2004 in Mongolia. The main purpose of this project was to improve system reliability and cost performance on the natural conditions and distinctive social systems, which are rarely seen in Japan. It has been observed that the high PV penetration (during project period: 80.4% during 09/2003–12/2007) 71% of total supplied energy, and the low system failure ratio. On the other hand, average PR (performance ratio) indicated 0.20 (during project period), 0.14 (estimated values between 09/2003–12/2007) due to the limited demand and distributed/grid-connected PV units (100kW) with the auxiliary power mode.

The AIST 1 MW PV facilities consist of a total of 211 inverters of the 4-kW type designed principally for residential uses, and tens of inverters of the 10-kW unit designed principally for industrial uses. These inverters are connected to low-voltage (200 V) distribution line in AIST. There are 13 kinds of PV modules from 5 different technologies and tens kind of PV inverter from several manufactures. Benchmarking these PV components reveals the differences of the performance and reliability among other PV components under actual conditions. During the first two years, there were several failures in the system components, mainly caused by improper installation works. But the PV facilities showed proper performance ratio (around 70%) and perfect availability in total. The mean time of failure was 7.9 times. More than 64% of individual PV systems had no failures. The mean time to repair was only 3.3 days

Solar energy maps that indicate the wide-ranging spatial distribution of solar irradiation are required by the researchers of the solar power systems. However, the irradiation measurement networks at ground level are not enough to obtain reliable information of the solar energy distribution in the world. On the other hand, geostationary meteorological satellites (GMS) have provided the images of cloud fields over the whole surface of the Earth. The main cause of an irregular change in the irradiation at the ground level is effect of the clouds; therefore, methods for estimating the irradiation by using the GMS images may be very useful. The solar irradiation for 14 sites in Japan was estimated by a semi-physical model developed by the authors. The RMS errors, averaged over 14 stations, were 0.0804 kWh/m/sup 2/ for hourly estimates, 0.534 kWh/m/sup 2/ for daily estimates and 7.14 kWh/m/sup 2/ for monthly estimates. There were little regional differences of estimate accuracy. An example of solar energy maps for Eastern Asia in 1992 is presented.

Various photovoltaic (PV) technologies are commercially available today. The effect of solar spectrum on the performance of PV modules should be evaluated quantitatively in order to estimate the module performance with high accuracy and precision. Average photon energy (APE) has been frequently applied to evaluate the effect of solar spectrum. The purpose of this study is to enhance the precision and accuracy by introducing other indexes. In this study, we select solar spectra, the integrated spectral irradiance (ISI) and APE of which are equivalent to those of the standard AM1.5G spectrum. There is a slight difference in shape, although the shapes are approximately similar. We introduce one more index, which defines the spectral irradiance at the atmospheric window or the depth of the water absorption band. The introduction would further improve the accuracy and precision of the evaluation of the effect of solar spectrum.