Commercial Photovoltaic Systems Research Articles

Electrical characterization of photovoltaic modules using farmland fertility optimizer

Photovoltaic (PV) model parameters are essential in recognizing its effectiveness at changed sun irradiances, temperatures and under various loading conditions. Estimating PV model parameters can be considered as a high non-linear optimization problem. The objective function is adapted with the aim of the minimization in regards to the root of the mean squared errors among the corresponding calculated and real current points subjects to set of parameters constraints. In this research, a novel application of newly developed farmland fertility optimization (FFO) algorithm to identify the PV model unknown parameters is addressed. This research work aims at producing an efficient PV models to characterize their performances under changed environmental conditions. Two electrical models such as one- and double-diode equivalent circuits are analyzed carefully. The applicability of the FFO approach is assessed by comparing its simulated results with the empirical results of three typical commercial PV systems. Subsequently, comparisons between the FFO cropped results and other competing recent methods-based results are made to validate the FFO results. It can be declared here that the FFO executes well and owns a good strength to recognize unknown PV model parameters with lesser errors.

Is it a good time to develop commercial photovoltaic systems on farmland? An American-style option with crop price risk

Photovoltaic systems require large swaths of land that are currently being used for other purposes, such as farming. One option for developing large photovoltaic systems is converting farms that are currently economically unviable into commercial photovoltaic systems. However, this may not always be an economically rational decision as crop prices have the potential to increase over time. Fluctuations in farm income due to changes in crop prices can alter the optimal choice of whether to continue farming or to convert farmland into commercial photovoltaic systems. This study attempts to resolve this issue by proposing a real options framework to value farm production when crop prices are uncertain. By integrating uncertainty into the decision-making process, the value of keeping unprofitable farms operating prior to developing the area into a commercial photovoltaic system is assessed. This helps decision makers understand the extent to which potential income from developing a photovoltaic system should be greater than potential income from farming when deciding on investing in a photovoltaic system. A case study is conducted to examine this framework and to calculate the net present value of a farm in South Korea. The results indicate that although the money lost from continuing to farm is substantial, farmers should defer conversion to a commercial photovoltaic system until a sufficient drop in crop prices occurs. When applying this strategy, the farmer can gain an additional 100% of expected revenue simply by deferring the development decision until having better information on the market prices of crops.

Guiding the environmental design of a novel solar absorber through life cycle assessment by identifying anticipated hot spots

Life cycle assessment (LCA) can be a powerful tool in minimizing aggregate life cycle impacts if used during early stage research before materials, processes, and system designs are set. This study examines the life cycle effects of substituting two promising arsenic-containing polymorphs of Cu3AsS4 as the absorber layers in single junction thin-film photovoltaic (PV) cells. These thin films and the auxiliary components they require to create functioning PV systems are compared with existing commercial PV systems, including crystalline silicon, cadmium telluride (CdTe), and copper indium gallium diselenide (Cu(In,Ga)Se2). The resulting impacts for Cu3AsS4 are expressed as a range of equally possible values to reflect the design choice uncertainties in this early-stage LCA. Hot spots are identified to determine the most relevant contributors to PV system impacts and uncertainty ranges. Scenario analyses are performed to quantify the change in life cycle impacts due to mounting configuration and product performance. Calculated impacts and identified hot spots suggest Cu3AsS4 PV systems are consistent with commercial PV technologies. Notable design considerations include minimizing waste associated with deposition techniques that have modifiable utilization efficiencies (especially for molybdenum), designing reusable BOS components, investigating roll-to-roll compatible substrates, and prioritizing module efficiency improvements. Within the system boundaries examined here, the contribution of arsenic to the overall life cycle impacts is calculated to be less than 1% in all impact categories through both economic and mass allocations, but direct exposure through specific manufacturing and decommissioning steps were not modeled. By determining potential Cu3AsS4 life cycle impacts, identifying life cycle hot spots, and offering design options, this work serves to establish a basis on which the environmental implications of this potential thin film technology are understood.

Reducing Interanalyst Variability in Photovoltaic Degradation Rate Assessments

The economic return on investment of a commercial photovoltaic system depends greatly on its performance over the long term and, hence, its degradation rate. Many methods have been proposed for assessing system degradation rates from outdoor performance data. However, comparing reported values from one analyst and research group to another requires a common baseline of performance; consistency between methods and analysts can be a challenge. An interlaboratory study was conducted involving different volunteer analysts reporting on the same photovoltaic performance data using different methodologies. Initial variability of the reported degradation rates was so high that analysts could not come to a consensus whether a system degraded or not. More consistent values are received when written guidance is provided to each analyst. Further improvements in analyst variance was accomplished by using the free open-source software RdTools, allowing a reduction in variance between analysts by more than two orders of magnitude over the first round, where multiple analysis methods are allowed. This article highlights many pitfalls in conducting “routine” degradation analysis, and it addresses some of the factors that must be considered when comparing degradation results reported by different analysts or methods.

사업용(100kW) 태양광 발전설비 원가구조 분석 : 한국, 독일, 중국 사례를 중심으로

사업용(100kW) 태양광 발전설비 원가구조 분석 : 한국, 독일, 중국 사례를 중심으로

An Empiric-Stochastic Approach, Based on Normalization Parameters, to Simulate Solar Irradiance

This paper presents a methodology to estimate solar irradiance using an empiric-stochastic approach, which is based on the computation of normalization parameters from the solar irradiance data. For this study, the solar irradiance data were collected in a weather station during a year. Posttreatment included a trimmed moving average to smooth the data, the performance of a fitting procedure using a simple model to recover normalization parameters, and the estimation of a probability density, which evolves along the daytime, by means of a kernel density estimation method. The normalization parameters correspond to characteristic physical variables that allow us to decouple the short- and long-term behaviors of solar irradiance and to describe their average trends with simple equations. The normalization parameters and the probability densities allowed us to build an empiric-stochastic methodology that generates an estimate of the solar irradiance. Finally, in order to validate our method, we had run simulations of solar irradiance and afterward computed the theoretical generation of solar power, which in turn had been compared with the experimental data retrieved from a commercial photovoltaic system. Since the simulation results show a good agreement with the experimental data, this simple methodology can generate the synthetic data of solar power production and may help to design and test a photovoltaic system before installation.

A combined model for PV system lifetime energy prediction and annual energy assessment

This paper presents a generic model for the prediction of the lifetime energy production of photovoltaic (PV) systems and the assessment of their annual energy yield in different time periods of operation. As case studies, it considers domestic PV system generation potentials in the UK and India to demonstrate the model results across a range of contrasting climatic and operating conditions. The model combines long-term averages of solar data, a commercial PV system simulation package and a probability density function to express the range of the annual energy prediction in different time periods of system operation. Moreover, a sensitivity analysis based on degradation rates and energy output uncertainties is embedded in the lifetime energy calculations. The importance of the reliability and maintenance of the PV systems and the energy prediction risks, especially regarding economic viability, are demonstrated through the PV lifetime energy potentials in these two countries. It is shown that, even for countries that are significantly different in respect to their solar resource, PV systems may produce similar amounts of energy during their lifetime for reasonable assumptions of degradation rates and uncertainty levels.

Economic benefits of combining self-consumption enhancement with frequency restoration reserves provision by photovoltaic-battery systems

Residential and commercial photovoltaic (PV) battery systems are increasingly being deployed for local storage of excess produced PV energy. However, battery systems aimed at increasing self-consumption are not constantly put to use. Additional battery storage capacity is available for a second application to improve the profitability of an energy storage system. One of these options is the provision of frequency restoration reserves (FRR) to the electricity balancing market. This provision can be either negative to compensate for excess power supply, or positive to compensate for excess demand on the power market. This study assesses the benefits for residential and commercial PV-battery systems by combining PV energy storage for higher self-consumption with provision of FRR. Six battery storage dispatch strategies were developed and assessed on the technical and economic performance of 48 residential and 42 commercial PV-battery systems. These systems were modelled over their economic lifetime with a time resolution of 5 min and with historical energy consumption measurements and market prices. FRR provision results in a small drop in the self-consumption rate of 0.5%. However annual revenues are significantly increased. Using battery storage systems only for self-consumption is not profitable with the assumptions used in this study. Provision of negative FRR substantially reduces the electricity bought with the consumption tariff and increases investment attractiveness substantially. Prioritizing the provision of FRR over self-consumption enhancement results in even higher revenues, but significantly reduces self-consumption. We recommend FRR provision to economically investment in residential battery storage systems. Commercial systems need prioritization of both positive and negative FRR provision over self-consumption for a cost-effective investment. In conclusion, combining enhancement of PV self-consumption with the provision of frequency restoration reserves leads to profitable investments.

Module temperature models assessment of photovoltaic seasonal energy yield

Commercial photovoltaic systems focused on the low power sector, such as residential, commonly base their energy production estimations on simple mathematical models that use average solar irradiance values, which do not necessarily apply to the installation site. Thus, there is an overestimation/underestimation in the energy production, and the investment payback does not match to the expected one. This paper presents a module temperature models’ impact assessment, which considers parameters associated with the photovoltaic-cell material, the solar irradiation site, the temperature and the wind at the installation. Four different module temperature models with different complexity degrees were used for the study case. Results of energy yield, with and without wind, are presented, and are analyzed according to the seasons of the year. The Muzathik model estimates up to 5.19%, 4.69%, and 4.8% more energy versus the Sandia, Faiman, and Skoplaki models, respectively. Up to 9.19% more available energy was observed in such circumstances where a speed difference of 8 m/s is present.

Cost Competitive Luminescent Solar Concentrators

Luminescent solar concentrators (LSCs) absorb and re-emit solar radiation into a waveguide coupled to efficient small-area photovoltaic cells. The cost efficiency of LSCs scales with collection area and increases with broader solar spectrum harvesting. Recently in Nature Photonics, Wu, Li, and Klimov demonstrate a tandem stack of two complementary LSCs of area > 230 cm2 based on wavelength-separated colloidal quantum dots. A technoeconomic analysis demonstrates the promise of this approach for reducing the per watt cost of commercial photovoltaic systems.

Influence of demand patterns on the optimal orientation of photovoltaic systems

Photovoltaic (PV) systems are usually orientated to maximize annual energy yield. This may not optimize other system indicators, specifically: direct consumption of self-generated PV power, reduced feed-in power and annual revenue. Also, these indicators are influenced by the energy demand of a building in relation to the PV system size. Therefore, we evaluate how demand patterns influence the optimal PV orientation for self-consumption, feed-in power and revenue. Historical Dutch demand patterns of 48 residential and 42 commercial buildings were used. We combined Dutch and German electricity prices from day-ahead markets with different ratios of electricity sales to purchase prices. Differences between demand patterns caused large variations in optimal PV orientations. On average, PV self-consumption is maximized for residential systems with an azimuth of 212° and a tilt of 26°. Commercial PV systems have an average of 188° azimuth and 17° tilt. Self-consumption can be increased 5.4% for residential systems and 2.7% for commercial systems, by optimizing orientation for self-consumption rather than for energy production. Curtailment losses are significant reduced by decreasing the module tilt angles. Optimizing for revenue can increase annual revenue of PV systems with 5.4% for certain demand patterns and pricing scenarios. The ratio of sales to purchase electricity price has a larger influence on the economically optimal orientation for residential systems than for commercial systems. Differences between Dutch and German market prices have minor effects on PV orientation. Analysed demand patterns significantly affect optimal PV orientation. Therefore, we recommend that optimal PV orientation should not only be based on maximizing energy production, but also on expected demand patterns and market prices.

Economic feasibility of residential and commercial PV technology: The Chilean case

This study presents an economic analysis of residential and commercial Photovoltaic (PV) systems in Chile. Continental Chile presents good solar resource and is also an interesting country for developing PV projects of all sizes (large-scale, commercial and residential). The analysis was performed on the two largest electric power systems, specifically on the 314 districts of 13 regions of Chile, taking into account the actual Chilean regulatory framework. Economic performance results of the residential and commercial PV systems were obtained and presented in geo referenced information systems (GIS) maps. The results show that almost all the country exhibits a great potential, obtaining in several locations an IRR higher than the reference value (5%/yr.) for both schemes (residential and commercial), highlighting that the central-north region reaches the highest IRR values. It was found that districts can be characterized by the electricity tariffs in clusters that increase the IRR linearly with the specific yield [kWh/kWp]. This study is of primordial importance for the development of renewable energies in the region, giving further understanding on the economic feasibility of the photovoltaic technology throughout the country.

Determining the size of PHEV charging stations powered by commercial grid-integrated PV systems considering reactive power support

Due to low electricity rates at nighttime, home charging for electric vehicles (EVs) is conventionally favored. However, the recent tendency in support of daytime workplace charging that absorbs energy produced by solar photovoltaic (PV) panels appears to be the most promising solution to facilitating higher PV and EV penetration in the power grid. This paper studies optimal sizing of workplace charging stations considering probabilistic reactive power support for plug-in hybrid electric vehicles (PHEVs), which are powered by PV units in medium voltage (MV) commercial networks. In this study, analytical expressions are first presented to estimate the size of charging stations integrated with PV units with an objective of minimizing energy losses. These stations are capable of providing reactive power support to the main grid in addition to charging PHEVs while considering the probability of PV generation. The study is further extended to investigate the impact of time-varying voltage-dependent charging load models on PV penetration. The simulation results obtained on an 18-bus test distribution system show that various charging load models can produce dissimilar levels of PHEV and PV penetration. Particularly, the maximum energy loss and peak load reductions are achieved at 70.17% and 42.95% respectively for the mixed charging load model, where the system accommodates respective PHEV and PV penetration levels of 9.51% and 50%. The results of probabilistic voltage distributions are also thoroughly reported in the paper.

Recovery of inter-row shading losses using differential power-processing submodule DC–DC converters

Large commercial photovoltaic (PV) systems can experience regular and predictable energy loss due to both inter-row shading and reduced diffuse irradiance in tightly spaced arrays. This paper investigates the advantages of replacing bypass diodes with submodule-integrated DC–DC converters (subMICs) to mitigate these losses. Yearly simulations of commercial-scale PV systems were conducted considering a range of row-to-row pitches. In the limit case of array spacing (unity ground coverage), subMICs can confer a 7% increase in annual energy output and peak energy density (kWh/m2). Simulation results are based on efficiency assumptions experimentally confirmed by prototype submodule differential power-processing converters.

Risk mitigation of performance ratio guarantees in commercial photovoltaic systems

Risk mitigation of performance ratio guarantees in commercial photovoltaic systems

(Invited) Photoelectrochemical Reduction of CO2: Electrocatalytic Formation of Solar Fuels

The 6-electrons, 6-protons transformation of CO2 to methanol requires a thermodynamic energy input of 690kJ/mole under standard conditions, about 5.5 times more energy than the free energy required to split water. But, for this “price” one obtains a liquid fuel that has an enthalpic combustion content, which is about 2.8 times larger than hydrogen. This combined with methanol’s density (compared to hydrogen) provides a volumetric energy density that makes this compound a potential liquid fuel. However, the energy landscape for this type of reactivity is complicated by the large activation barrier associated with the one-electron reduction of CO2. At most metallic electrodes a ~1V overpotential is needed to achieve a pragmatically viable rate of conversion to products.1 This constraint holds true even if the product formation is shifted to formic acid, although this species only involves a two-electron reduction. A volt of “overpotential” is an extreme energetic burden. In certain cases, this issue can be overcome either by the choice of electrode materials employed2,3 or by introducing a protonated aromatic amine as an electrocatalyst.4 For example, addition of pyridinium to a palladium electrode based electrochemical cell reduces the overpotential for methanol to ~200mV.5 Similar advantage can be obtained with aromatic amine catalysts for other C1 species. This electrocatalytic approach can provide commercially useful products, while removing CO2 from the environment, as long as a nonfossil based fuel is utilized as the energy source. To this end, we have developed two types of light driven electrochemical reactors. In the first case, heavy post-transition metal electrodes such as indium, tin, bismuth or lead that are intrinsically catalytic for CO2 to formate are powered by a commercial photovoltaic system.6 This has the advantage that the PV system and the electrochemical reactor can be separately optimized, but the approach increases the necessary system engineering. Our second solar fuels approach is the use of a photoelectrochemical cell. In this system, one or both of the electrodes in the electrochemical reactor is composed of a semiconductor that absorbs visible light, generating a voltage in-situ, and a simplified balance of plant. In these systems the introduction of a dissolved aromatic amine catalyst is of utility. To date, we have found p-type semiconductor such as GaP 7 and certain metal oxides semiconductors having a delafossite structure such as CuFeO2,8 to be active for the chemistry of interest.

Commercial photovoltaic system design for Cardiff City Hall

The rooftops of Cardiff City Hall were surveyed to establish potential areas for commercial-scale photovoltaic (PV) system design. The orientation and tilt angles of suitable unshaded roof areas were measured for accurate PV system simulation. The performance of two PV technologies, polycrystalline silicon (p-Si) and heterojunction with intrinsic thin layers (HIT) was investigated. From the analysis of simulation, experimental, environmental and economic data, HIT was found to be the best-performing PV technology for system installation. Superior performance of HIT under diffuse sunlight conditions, typical of the UK climate, was demonstrated. Additionally, the maximum power temperature coefficient, verified during experimental work, was lower than the p-Si alternative (−0·28 against −0·50%/°C). Electricity demand data for City Hall were analysed and 8·1% of the annual electricity demand (solar fraction) could be supplied by an 88 kWp HIT PV system. The HIT PV system modelled would significantly improve the energy performance of Cardiff City Hall, avoiding >40 000 kg carbon dioxide emissions annually. The levelised cost of energy from one array (B, £0·11/kWh) was less than the current day tariff rate for grid import (£0·1173). The economic and environmental benefits of well-designed high-efficiency PV systems in the UK at commercial scale are also demonstrated.

Diseño e Implementación de un Sistema de Control estable basado en Lógica Borrosa para optimizar el rendimiento de un sistema de Generación Fotovoltaico

This paper presents a new control scheme for a standalone photovoltaic (PV) system based on a fuzzy-logic (FLC). The proposed control system provides good tracking for the optimal reference voltage, at which the maximum power generation is obtained. The photovoltaic system is connected to a load through a DC/DC boost converter. The FLC controller provides the appropriate duty cycle (D) to the DC/DC converter in order to get the maximum power from the PV system. A method for the stability analysis of the closed-loop system is also proposed. The stability analysis is based on the Lyapunov methods and is a semi-qualitative analysis because there is no closed loop system model available for the analytical analysis. Both simulation results and experimental tests on a real PV system show that the FLC provides good tracking for the maximum power point (MPP).Finally, the performance of the FLC on a real PV system consisting of a commercial solar panels Atersa model A55 is analyzed. To perform the experimental tests the proposed control strategy has been implemented on the dSPACE digital signal processor model DS1104. The experimental results demonstrate the good performance of the proposed FLC control scheme over a commercial photovoltaic system

Tracking US photovoltaic system prices 1998-2012: a rapidly changing market

The number of US photovoltaic (PV) systems has grown rapidly in recent years, driven by a wide array of government incentives and other supportive policies aimed, in part, at reducing PV system prices. This article draws from a sample of more than 200,000 US residential, commercial, and utility-scale PV projects to summarize price trends for PV systems installed from 1998 through 2012. These data show that the average installed price of US residential and commercial PV systems declined 6–7% annually during 1998–2012, although the pace and source of price reductions varied. In 2012, the median reported installed price of residential and commercial PV systems was $5.3/W for systems of 10 kW or smaller, $4.9/W for systems of 10–100 kW, and $4.6/W for systems larger than 100 kW. The capacity-weighted average installed price of crystalline, fixed-tilt, utility-scale PV systems (ground-mounted systems at least 2 MW in size) declined from $6.2/W during 2007–2009 to $3.3/W in 2012. Recent price reductions are associated primarily with a precipitous drop in PV module prices, while non-module costs have remained relatively stagnant since 2005. Further system price reductions will be needed to expand US PV deployment as incentive programs reduce their financial support. Because further module price reductions are limited, additional deep reductions in installed prices will require significant reductions in non-module costs, particularly non-hardware (“soft”) costs. Lower installed prices in international markets suggest that deep near-term soft cost reductions in the USA are possible with the help of targeted policies. Copyright © 2014 John Wiley & Sons, Ltd.

Temperature and wind speed impact on the efficiency of PV installations. Experience obtained from outdoor measurements in Greece

Although efficiency of photovoltaic (PV) modules is usually specified under standard test conditions (STC), their operation under real field conditions is of great importance for obtaining accurate prediction of their efficiency and power output. The PV conversion process, on top of the instantaneous solar radiation, depends also on the modules' temperature. Module temperature is in turn influenced by climate conditions as well as by the technical characteristics of the PV panels. Taking into consideration the extended theoretical background in the field so far, the current study is focused on the investigation of the temperature variation effect on the operation of commercial PV applications based on in-situ measurements at varying weather conditions. Particularly, one year outdoor data for two existing commercial (m-Si) PV systems operated in South Greece, i.e. an unventilated building-integrated (81 kWp) one and an open rack mounted (150 kWp) one, were collected and evaluated. The examined PV systems were equipped with back surface temperature sensors in order to determine module and ambient temperatures, while real wind speed measurements were also obtained for assessing the dominant effect of local wind speed on the PVs' thermal loss mechanisms. According to the results obtained, the efficiency (or power) temperature coefficient has been found negative, taking absolute values between 0.30%/°C and 0.45%/°C, with the lower values corresponding to the ventilated free-standing frames.