The Israeli Planning Administration has approved a new set of regulations for energy storage. Set out as a national outline plan, the new regulation deals with the capacities of different energy storage facilities, where they can be built and under what conditions.

“The plan will allow the deployment of storage units next to PV plants, gas stations and houses. That will help regulate energy consumption under high demand,” the Ministry of Energy and Infrastructure said in a statement. “On the backdrop of the war in Gaza, energy storage can maintain energy for few hours under emergency conditions.”

According to the plan's original papers from January 2023, storage of up to 600 kWh can be built on any land, under some caveats. Bigger storage facilities of up to 5 MWh are allowed on any land, with the exceptions of agricultural land, scenic land, protected land or in the vicinity of a river.

Larger storage facilities, of up to 16 MWh, will only be allowed on land with specific uses. Among permitted lands are those for industrial use, parking lots and public buildings. More extensive storage of more than 16 MWh is not regulated in this program.

In addition, the new regulation sets environmental terms, safety terms, and water safety terms.

“Storage infrastructure improves the potential of renewable energy use,” the ministry added. “This regulation plan was made to support it, as based on it, permits for construction of such facilities can be issued.”

Researchers from Spain have simulated the effect building integrated photovoltaics (BIPV) will have on the energy consumption and the economics of high-rise office buildings in the Mediterranean area.

They presented three different BIPV integration scenarios for the GESA building, an office building built in the 1960s in Palma de Mallorca, in Spain's southern archipelago of the Balearic Islands.

“Despite of its iconic and protected status, the GESA building has been abandoned for several years, hence it requires a refurbishment that will also update its skin to the current energy efficiency standards,” the scientists explained. “The inefficient envelope, location (isolated and in a sunny climate), and representability of a typology of office building make it a good reference for studying the impact of refurbishing with BIPV.”

Via the TRNSYS simulation software, which is commonly used to simulate the behavior of transient renewable systems, the group simulated the impact of BIPV taking as reference a representative floor. As in the physical building, among the parameters inserted are the GESA building’s curtain wall structure, which is 77% composed of semi-transparent windows and 23% of non-window opaque areas. As the building, although abandoned, is protected by a local heritage commission, the façade design has to keep its original characteristics.

The reference scenario was based on the existing double-glazing Parsol Bronze window. It was compared to four other scenarios, one with only solar control windows; the second with solar control windows and BIPV modules in the opaque area; the third with only transparent BIPV windows; and the fourth with BIPV windows and opaque BIPV in non-transparent areas.

“The data for the transparent PV used in this study is based on a prototype currently in development, hence there is room to improve the thermal, optical, and electrical properties to better fit the building needs, as well as to increase the PV conversion efficiency,” the research group emphasized.

According to the results, the final energy consumption in the existing reference case was simulated at 51.3 kWh/m2. In the case of only solar control windows, this value reached 45.8 kWh/m2, with very similar results with the addition of opaque BIPV. However, in this case, the building will be able to use 5.8 kWh/m2 and export 2.6 kWh/m2 to the grid.

In the case of only transparent BIPV windows, the energy consumption will be higher, as that module will block more of the solar radiation and, therefore, result in higher heating and lighting demands. Overall, that system will require 49.8 kWh/m2 while consuming 5.1 kWh/m2 and exporting 2.2 kWh/m2. In the case of using window BIPV and opaque BIPV, the demand will reach 47.6 kWh/m2, while self-consumption will take 10.9 kWh/m2 and 5 kWh/m2 will be exported to the grid.

“The results show the potential of the BIPV solutions for improving the energy balance of the building. The transparent PV reduced the energy demand by 6.9% and the total energy balance by 21%,” the scientists added. “The opaque PV further improved the results of the two glazing system solutions, the energy balance improving to 28.1% and 38.3% with the solar control and transparent PV solutions, respectively.”

The researchers also conducted an economical analysis, which they claim showcases the “relevance of the electricity pricing schemes into the promotion of BIPV.” The components and installation cost of the components were mostly obtained from a construction materials database, while the cost of the prototype window BIPV was assumed at €200 ($210.65)/m2.

They looked into two tariff levels. The first is based on current Spanish tariffs and demand, while the second assumes a high penetration of PV into the national grid. In this case, the net load of high-penetration photovoltaics presents a very low price. Another variable was the compensation for the electricity sold to the grid by the building, which they estimated at either 0%, 30%, or 100% of the electricity price.

Currently, 30% of the electricity price is the typical export value in Spain. Under this assumption, with the current price profile, the discounted payback time for solar control will be 24 years, for solar control and opaque BIPV it will be 14 years, for window BIPV only it will be over 50 years, and the combination of both BIPV technologies will result in a payback time of 24 years. In the assumption of high PV penetration and 30% electricity price, however, the payback time in all systems may exceed over 50 years.

“The lower average electricity price and, more importantly, the timing of the generation in the ‘high PV’ scenario explain the significantly worse payback periods,” they concluded.

Their findings are available in the paper “Impact of building integrated photovoltaics on high rise office building in the Mediterranean,” published in Energy Reports, which also included an economic evaluation. The research group comprised academics from The Technical University of Catalonia and the Catalonia Institute for Energy Research.

German PV manufacturer Technaxx has introduced a new solar table for residential use.

The table embeds on its surface monocrystalline solar panels with 410 W of output and a power conversion efficiency of 20.97%. Its pre-assembled micro-inverter allows for 400 W of output.

“We use PERC technology for our solar modules, which feature high-efficiency cells and are equipped with three bypass diodes,” a company spokesperson told pv magazine.

The product can be purchased for €699-951.00 ($736.52-1,000), according to the company's website.

When not used as a tabletop, the table panel can be tilted to 20, 30 or 35 degrees for energy generation. Its activity can then be tracked via an app, remotely, as the table transmits the data via Wi-Fi. The table measures 173 cm x 114 cm x 84 cm and is suitable for up to eight people.

“Our solar modules are TÜV certified for mechanical stress, including 2400Pa wind load and 5400Pa snow load,” the company said. “However, single-point stress can damage the module and hail.”

Researchers led by the German University of Technology in Oman have looked into the effect of dust accumulation on PV systems and claim to have identified an optimal cleaning cycle in economic terms.

The scientists have conducted the research on an experimental setup located in an area next to their campus. “The research might be valid to countries with dry weather, humidity during summer, and high temperature,” the research's corresponding author, Ali Al Humairi, told pv magazine. 

“Photovoltaic energy is considered the most viable renewable energy source in the Middle East and North Africa region due to the high solar irradiation level and the number of clear sky days during the year,” the group said. “However, environmental factors such as dust limit the optimum utilization of the source.”

The experimental setup included two identical strings of nine PV modules connected in series, with one string being dry-cleaned daily and the other not. The 5.85 kW ground-mounted system was south-oriented and had a tilt of 17 degrees. The modules were based on polycrystalline cells, and each had a peak power of 325 W. The system included an inverter with 98.5% efficiency.

The observation of electrical and weather parameters began in November 2020 and ended in April 2021. “The experiment was conducted in the winter and spring seasons, which generally have less soiling rate and air contamination,” the researchers explained.

Comparing the cleaned string to the non-cleaned string, the academics found that dust led to up to a 28% reduction in the PV current performance and up to a 24.2% reduction in the PV power. Overall, the average difference in the current performance was 14%, and in PV output it was calculated at 11%.

“The difference between the uncleaned and the cleaned modules’ output current has increased exponentially during this period,” they said regarding the current. “In November, the difference in current is about 2%, which increased with time; in December and January, it is about 5% and 10%, respectively. The momentum intensity slightly dropped in February and recorded a difference of 18%. This was followed by a less momentum increment in March and April, resulting in a difference of 22% and 28%, respectively.”

As for the PV power output, they found no substantial effect in the first three months, with the difference being 0.1% in November, 1.9% in December, and 7.7% in January. However, it was much more noticeable in the next three months – with a 14.7% difference in February, 19.3% in March, and 24.2% in April.

For its economic analysis, the team used a fixed rate tariff of $0.11 per kWh. The cleaning rate was set at $1.30 per hour per worker, and according to the paper, one person could clean the whole system in one hour. Using this data, they have found the recommended cleaning interval to be once every one or 1.5 months, resulting in 8 to 12 cleaning cycles per year.

The group presented its findings in the paper “Experimental Investigation Of The Soiling Effect On The PV Systems Performance And The Cleaning Intervals In Oman,” published in Solar Energy Advances. It also included scientists from the Sultan Qaboos University, Muscat University, and Germany’s Duisburg Essen University.

“The effect of the accumulated dust was evident in the third month of the experimental period, indicating the necessity of conducting a cleaning cycle for fewer than three months to avoid losses,” the researchers concluded. “However, the results could vary depending on the location, season, geographical and meteorological conditions.”

The team has partnered with international logistics company Gebrüder Weiss for the mission.

“Due to its limited payload capacity, this solar-powered vehicle cannot yet replace a conventional truck, but it shows a completely new direction in which we will be able to move with alternative drives in the future,” said Frank Haas, head of corporate brand strategy at Gebrüder Weiss.

The project has been under development for four years, with the Swiss group modifying an Aebi Schmidt multi-purpose truck.

“Our vehicle makes it possible to perform even the most demanding transport tasks, whether in mining or when erecting high-altitude solar power plants, in an environmentally compatible and economically efficient manner,” said Patrik Koller, head of finance and co-developer of the Peak Evolution Team.

MIT researchers have developed a new CSP system to produce green hydrogen. The system, which is currently in the conceptual stage, aims to use up to 40% of solar heat for green fuel generation – a significant improvement from previous systems, which only achieved a 7% utilization rate.

“The increase in efficiency could drive down the system’s overall cost, making solar thermochemical hydrogen (STCH) a potentially scalable, affordable option to help decarbonize the transportation industry,” the scientists said. “It is a big step toward realizing solar-made fuels.”

Similar to other STCH designs, the conceptual system can be built around an existing CSP plant, absorbing the receiver’s heat and directing it to split water and produce hydrogen. However, there is a novel two-step thermochemical reaction at the heart of the new system.

“In the first step, water in the form of steam is exposed to a metal. This causes the metal to grab oxygen from steam, leaving hydrogen behind,” the scientists said. “Once hydrogen is separated, the oxidized (or rusted) metal is reheated in a vacuum, which acts to reverse the rusting process and regenerate the metal. With the oxygen removed, the metal can be cooled and exposed to steam again to produce more hydrogen. This process can be repeated hundreds of times.”

The efficiency of this process is related to its train-like design, with box-shaped reactors running on a circular track. Each reactor in the train would house the metal repeatedly going through different thermochemical stations.

“Each reactor would first pass through a hot station, where it would be exposed to the sun’s heat at temperatures of up to 1,500 C. This extreme heat would effectively pull oxygen out of a reactor’s metal,” the group said. “That metal would then be in a ‘reduced' state – ready to grab oxygen from steam. For this to happen, the reactor would move to a cooler station at temperatures around 1,000 C, where it would be exposed to steam to produce hydrogen.”

Another improvement in the system is its ability to recover most of the heat used in the process. It does so by allowing reactors on opposite sides of the circular train-like track to exchange heat through thermal radiation. In addition, a second set of reactors circle around the first train, moving in the opposite direction and operating in cooler temperatures. This allows the evacuation of oxygen from the hotter inner train, without the need for energy-consuming mechanical pumps.

“When fully implemented, this system would be housed in a little building in the middle of a solar field,” said researcher Aniket Patankar. “Inside the building, there could be one or more trains each having about 50 reactors. And we think this could be a modular system, where you can add reactors to a conveyor belt, to scale up hydrogen production.”

The research team said it will build a prototype of the system in the coming year.

“We’re thinking of hydrogen as the fuel of the future, and there’s a need to generate it cheaply and at scale,” said the study’s lead author, Ahmed Ghoniem.

Atess Power Technology has developed a new battery inverter with 1,000 kW of capacity. The PCS1000 bidirectional model is designed for the commercial and industrial segments.

“This 1,000 kW large capacity inverter can satisfy your huge energy demand, while its easily scalable design showcases its high expandable potential for customized requirements,” the company said in a statement. “With a built-in energy management function, this inverter ensures more uninterrupted and long-lasting power in a cost-effective way.”

Researchers from China have assessed the accuracy of the WRF-Solar model in simulating global and diffuse radiation, pointing to its sensitivity to aerosol optical depth (AOD), cloud optical thickness (COT), and solar zenith angle (SZA).

The Weather Research and Forecasting (WRF) model was developed in 2016 within the Sun4Cast project funded by the US Department of Energy. The model is in the public domain and can be downloaded from the official WRF Github repository.

“Since the release of WRF-Solar, its performance in the simulation of diffuse radiation in localized regions in China and sensitivity to atmospheric parameters have not been fully explored,” the research group said. “This study aimed to test the simulation accuracy of WRF-Solar for global and diffuse radiation using satellite-based aerosol optical properties, which were obtained from a moderate resolution imaging spectroradiometer.”

The WRF model is widely used for weather forecasting. It uses the Rapid Radiative Transfer Model for Global Climate Models (RRTMG) scheme as shortwave radiation input, and the WRF-Dudhia as a radiation scheme. Additionally, the WRF-Solar model uses AOD input for its predictions, while WRF-Dudhia does not.

In their mission to emphasize the sensitivities of the WRF-Solar model, the academics have compared its predictions with real-life observations measured at Wuhan University. As for the AOD sensitivity, the researchers found that simulation error gradually decreased with the increase in the AOD. The parameter measures the scattering and absorption of light by tiny particles, or aerosols, in the atmosphere.

“The standard deviations of simulation errors corresponding to three different AOD ranges, of less than 0.4, between 0.4 and 0.8 and greater or equal to 0.8, were 162.12, 158.15 and 135.45 W m-2 of diffuse radiation, respectively,” they said. “However, when the AOD is greater or equal to 0.8, the model overestimated the diffuse radiation, with an average bias of 58.57 W m-2.”

As for COT, which measures how effectively a cloud layer scatters and absorbs sunlight, the researchers found the error to decrease with a COT increase. The standard deviations of the bias corresponding to COT range lower than 20, between 20 and 40, between 40 and 60, and more significant than 60, reaching 173.40, 149.45, 133.84, and 99.11 W m-2, respectively.

The scientists also looked at the dependence of WRF-Solar error on the SZA. “The simulation error increased as the SZA decreased,” they said. “When SZA <30 degrees, very discrete biases of simulated diffuse and global radiation were observed, with standard deviations of the bias of 245.40 and 286.65 W m-2 and mean differences of 79.20 and -3.62Wm-2, respectively. However, when SZA is between 50 and 70 degrees, the biases of simulated diffuse and global radiation were small, with standard deviations of 136.90 and 121.77 W m-2, respectively.”

However, comparing WRF-Solar to WRF-Dudhia, the researchers found the former to be superior. “In general, the improved WRF-Solar provides highly accurate forecasts in clear conditions. Under all-sky and cloudy conditions, poor comparison results of WRF-Solar and the traditional WRF model were obtained, and the simulated global solar radiation was largely overestimated.”

Their findings are available in the study “Assessment of the high-resolution estimations of global and diffuse solar radiation using WRF-Solar,” published in Advances in Climate Change Research. Concluding the article, the research group has emphasized the “need for improved representation of clouds and circulation in the model through physical parameterization and enhancements of satellite cloud and aerosol data assimilation techniques.”

The team included academics from China University of Geosciences and Hubei Luojia Laboratory.

Scientists from India have researched the impact of different laser fabrication energy levels on the photovoltaic properties of bilayer thin films made of bismuth ferrite (BFO) and tungsten trioxide (WO3)

They have investigated the BFO/WO3 combination to assess the aggregate benefits of the two compounds, in terms of multiferroic and insulating properties.

“The high leakage current of BFO thin films is a major concern while handling it for device applications,” the group said. “Fabrication of bi/multilayer thin film of BFO with other materials to provide an insulating intermediate layer, has been put forward to resolve this problem.”

“The enhanced photovoltaic response at 200 mJ may be the consequence of enhanced crystallite sizes, lower band gap, reduced leakage current, and larger values of remnant and saturation polarization,” the researchers concluded.

A group of researchers in Switzerland has investigated the visual stability and electrical performance of black interconnect coatings used in PV modules. These coatings are utilized to improve the aesthetic appeal of building-integrated photovoltaic (BIPV) modules, as they minimize their appearance on black back sheets.

“Interconnect hiding is often achieved through expensive and inefficient manufacturing steps, such as applying colored strips or bands with manual positioning,” the researchers explained. “A possible solution to modify the appearance of the metallic ribbons is to coat them with ink. Inkjet is one of the best technologies able to cope with the requirements of accuracy, resolution, and flexibility to coat the bright metallic ribbons.”

In a conversation with pv magazine, corresponding author Dr. Alejandro Borja Block added that “the cost of the manual process could be around 3 CHF ($3.32)/module, while an automated process could be 0.15 CHF/module approximately. It’s important to consider that many suppositions are made when doing these estimations, such as the automation degree of the equipment, lifetime of the equipment, consumables cost, cost of energy used, speed of the process, etc.”

In the paper “Stability of black interconnect coatings for solar photovoltaic module applications,” published in Solar Energy Materials and Solar Cells, the research team compared three types of metallic ribbons – one was a commercially available black ribbon with no information about the coating used, while the other two were coated in the laboratory with UV-curable inkjet commercial inks.

The scientists tested the three ribbons in a sequence based on industry-standard IEC 62788-7-2. All coated ribbons were cut into 3 cm long strips and were then laminated in conventional glass-back sheet (G/BS) modules.

They then encapsulated the panels using three different encapsulants, with and without UV blockers. The three samples were left in the chamber for a total of 2,000 hours, equivalent to roughly 120 kWh/m2 doses of UVA and UVB irradiance (UVA+UVB), which corresponds to approximately two years of outdoor exposure in central Europe.

“The single most striking observation to emerge from the data comparison was that the color change only appeared on the UV curable inkjet inks, not on the commercial black ribbons,” the academics said. “Ink 1 produced the largest color change, a yellow halo in the surroundings of the coated metallic interconnects appeared. This could indicate diffusion of ink components into the encapsulant and degradation. Ink 2 produced a milder but still noticeable color change.”

After this test, the researchers dug deeper into ink 1, as it showed the most significant color change. They did it in two ways: first, by isolating the ink and the pure molecule 2-PEA to investigate whether it played an important role in the degradation observed; second, by creating a mini solar module and then coating its ribbons with the relevant ink.

The pure component samples were aged for 24 hours and 10 days, or UVA + UVB dose of 1.5 and 15 kWh/m2, respectively. “The pure component of the ink and flush, 2-PEA, polymerized after 1.5 kWh/m2, and it turned yellow after 15 kWh/m2,” the group emphasized. “This is due to the creation of carbonyl bonds in the substance, which are related to the oxidation of the molecule under UV light. The carbonyl index rose by 22% following the UV exposure of 15 kWh/m2.”

As for the sample coated module, it was aged for 6,000 hours or UVA + UVB dose of 360 kWh/m2. “The use of the investigated unstable ink would represent an aesthetical modification of color in the long-term demonstrating a potential long-term instability, but the electrical performance would be similar to a module without coated ribbons (less than 3% power loss),” noted the team.

Concluding their research, the scientists said they “discourage the use of 2-PEA monomer for PV aesthetic applications and suggest the use of UV curable inks with aliphatic monomers, which have better non-yellowing properties, in combination with UV blocker encapsulants.” They also added that “UV blocker encapsulants help mitigate the photodegradation of 2-PEA on G/BS laminates, whereas they do not fully mitigate the degradation for the ink itself.”

The team comprises academics from the Swiss Federal Institute of Technology Lausanne, Switzerland’s CSEM, Sustainable Energy Center, Austria’s Polymer Competence Center Leoben and the Academy of Sciences of the Czech Republic.

Scientists from Spain’s research center Tecnalia have encapsulated solar panels with a composite material that they claim has enhanced chemical recyclability.

The novel encapsulant material is based on glass fiber-reinforced composite material with an epoxy matrix containing cleavable ether groups. “The aim was to provide the encapsulating material and PV modules with enhanced chemical recyclability while retaining photovoltaic performance and durability,” the research group explained. “Further work will consider improving the moisture barrier properties of the composite, and adjusting the recycling conditions to allow component recovery valid for new modules.”

The researchers fabricated twelve solar module samples using monocrystalline silicon cells and encapsulated them with the new material using a linear vacuum resin infusion process. “As reinforcement, a glass fiber fabric with a 300 g/m2 (0/90◦) areal weight was used. The reinforcement layout consisted of 3 layers placed at the front and back of the cell. As a composite matrix, an epoxy resin system with amine base hardener and cleavable chemical groups in its composition was used,” they noted.

The group tested the performance of the panels and compared it to reference modules encapsulated with a standard resin system based on a clear bisphenol-A epoxy and an amine-based crosslinker. In the set of tests, the recyclable encapsulants were tested against the reference encapsulant, as well as bare solar cells without any kind of encapsulation.

“The data of the monomodules with the composite encapsulant based on the recyclable epoxy resin showed an electrical loss in short-circuit current of 6.3% when comparing the electrical performance before and after encapsulation,” the researchers said. “This value was slightly lower than the one obtained for the monomodules with standard epoxy composite, which presented a decrease of 7.2%.”

The group observed a similar trend when analyzing the power at maximum point (Pmp) losses and the external quantum efficiency (EQE) spectra, a metric for the efficiency and spectral response of photovoltaic devices.

The researchers also conducted a damp-heat test for 500 hours of exposure on the panel encapsulated with the new material, and found it showed an electrical loss in short-circuit current of 3.4%, which compared to only 1.5% for the benchmark panel.

“After 1000 h exposure, the observed short-circuit current decrease was even more pronounced, being significantly higher for the cleavable epoxy matrix,” the academics noted. “A final loss of 4.9% was measured for recyclable resin, whereas the standard epoxy showed a lower value of 2.8%. Regarding Pmp values, the loss reached 4.7% and 3.4% for the recyclable and standard composite respectively.”

In addition, the researchers carried out stability and aging tests for UV exposure and thermal cycling. As for the latter, it presented a loss of around 1% in short-circuit current and Pmp, which is not considered significant, as it is below the measurement accuracy of the technique. As for the UV exposure, electrical losses were also close to 1%.

The novel material was described in the paper “Composite material with enhanced recyclability as encapsulant for photovoltaic modules,” published in Heliyon.

Looking ahead, the researchers noted future work needed in both analysis and improvement of surface homogeneity, as well as studying the aging performance of the modules made with the recovered fibers, and possibly using a different resin-fiber interface.  Additionally, the researchers see opportunity to improve the proposed technology. “Future work will also be focused on improving the damp-heat stability of the composite, in a trade-off with a successful recyclability,” they stated.

A research group in the United States has created a solar forecasting methodology that utilizes a combination of infrared (IR) images and global solar irradiance measurements.

The scientists claim that the novel approach is able to improve solar nowcasting and intra-hour forecasting, while being applicable to PV real-time markets and the optimization of energy dispatch into microgrids.

“Sky imager is more expensive than regular visible light all-sky imagers, but it can also approximate the height of clouds, so it is a low-cost alternative to a ceilometer,” the research's corresponding author, Guillermo Terrén-Serrano, told pv magazine, noting that the method is suitable for PV systems of any size. “Ceilometers cost around $20,000, and our method costs less than $2,000. Our system includes a radiometric infrared camera, data logger, high-resolution solar tracker, pyranometer, outdoor computer, weatherproof case, visible light fisheye, weather sensors and camera lenses.”

Visible light cameras are often used for ground-based sky images, helping PV models to react to cloud conditions. However, the sun saturates the pixels in those cameras, destroying information that could increase the performance of a solar forecast. Therefore, IR cameras are alternatively used, as they reduce the sun’s saturation.

IR-based forecasting, however, has issues of its own, such as a lower signal-to-noise ratio, among others. That is partly due to solar irradiance, which might distort images under some conditions. “This investigation introduces efficient data processing methods to remove the deterministic component of the global solar irradiance in pyranometer measurements and infrared images,” the paper explains.

In order to remove the effect of the irradiance, the novel method first uses machine learning to identify biases that might affect the clear sky index (CSI). As the CSI quantifies the effects of clouds on global solar irradiance (GSI), more accurate findings in the first measurement result in more precise findings in the second.

Then, another algorithm is used to classify the sky conditions of the IR images into four – clear sky, cumulus clouds, stratus clouds, and nimbus clouds. Using this classification, the algorithm further interacts with the GSI data and calculates the effect of the irradiance on the image, effectively clearing it for forecasting.

In addition, the algorithm removes the effect of dirt on the camera. “This investigation assumes that a sky imager will not be cleaned daily during operation,” the research group explained. “For this situation, a method based on image processing is proposed to remove the radiation emitted by debris on the outdoor germanium camera window from IR images.”

The algorithms were trained and tested with data from Albuquerque, New Mexico, in the United States, which has an arid semi-continental climate, with minimal rain. “Future research is required to develop a global model valid for any location,” they emphasize.

The researchers concluded that the proposed method is efficient and said that low-cost radiometric IR cameras can potentially be a substitute for expensive ceilometers in the future.

“Adequate data processing reduces learning algorithm complexity when implemented in the application of solar forecasting,” they said. “Complexity reduction increases the accuracy of the prediction and reduces the required computing time for making a prediction. This is of particular importance in real-time applications such as nowcasting and intra-hour forecasting of solar energy.”

Their findings are introduced in the study “Processing of global solar irradiance and ground-based infrared sky images for solar nowcasting and intra-hour forecasting applications,” which was recently published in Solar Energy. The researchers are from the University of California Santa Barbara and the University of New Mexico.

PVcase, a Lithuanian PV software-as-a-service company, has launched a new plugin for design and engineering tool AutoCAD, enabling users to model commercial and industrial rooftop solar systems.

The “PVcase Roof Mount” plugin offers 3D building preparation, layout generation, shading calculation, electrical design, and exporting to PVsyst for analysis. The company said that 3D building preparation allows users to quickly prepare a building with its obstacles and offset zones on the roof for module placement-

“Layout generation provides the required settings information and automatically places modules on a flat or sloped roof,” it said. “Shading calculation helps to determine which modules are overshaded and should be removed and which ones should be left in the layout.”

The company said the plugin provides electrical design capabilities with automated string placement algorithms for precision, but it also offers guidance for manual stringing to match inverter sizing and layout efficiency. It also includes a cabling feature for semi-automated cable path routing and length calculations. PVcase, which raised $100 million in an investment round last July led by Highland Europe, Energize, and Elephant, and recently acquired Anderson Optimization, is now offering its design software for solar projects in Europe.

The company offers the possibility of requesting a demo by clicking here.

China’s JinkoSolar has developed a new all-in-one energy storage system, including 215 kWh lithium-ion batteries with liquid cooling.

The product, which comes as an outdoor cabinet, integrates battery packs, a battery management system (BMS), a power conversion system (PCS), and fire-fighting equipment. It also has a maximum input voltage of 1,000 V.

The SunGiga JKS-215KLAA-100PLAA system’s battery has rated AC power of up to 100 KW.

It holds a non-uniform flow channel design to control cell temperature differences of up to 2 C. In addition, it offers several liquid control options to reduce power consumption.

“Due to the liquid cooling technology, the system comes with a lower battery temperature difference, extending the lifetime of batteries and significantly improving the charging and discharging efficiency,” JinkoSolar said. “The automatic state of charge calibration and the automated coolant refilling considerably reduce operation and maintenance (O&M) costs.”

The system offers cabinet expandability and modular design. It also has temperature, smoke and combustible gas sensors for the suppression of thermal runaway. According to its product sheet, the JKS-215KLAA-100PLAA also contains a cloud-based monitoring and operating platform.

“This solution simplifies the transportation, installation, and O&M processes associated with energy storage solutions through a combination of several components,” the company added. “It streamlines the transportation, installation, and O&M.”

SunGiga JKS-215KLAA-100PLAA

Scientists from India and South Africa have assessed the technical and economic opportunity of operating hybrid PV-biogas microgrids to charge electric vehicles (EVs).

“The study carried out could be useful for the authorities working in EV charging stations infrastructure development, policymakers and researchers,” the research group said. “The challenges associated with this work are mass adoption of EVs and consumer’s readiness to purchase the technology.”

They introduced the system in “Assessment of microgrid integrated biogas–photovoltaic powered Electric Vehicle Charging Station (EVCS) for sustainable future,” which was recently published in Energy Reports. The study was conducted by scientists from India’s REVA University, SDM College of Engineering and Technology, RYM Engineering College and the National Institute of Technology, along with a scientist from South Africa’s University of Johannesburg. The results were first shown at the 8th International Conference on Sustainable and Renewable Energy Engineering.

A German-Swiss research team introduced a novel optimization method for the integration of heat pumps in non-continuous industrial processes.

The novel technique utilizes Pinch Analysis, which identifies the optimal temperature levels for heat exchange within a system, and provides the coordinates for the optimal design and sizing of the heat pumps.

“In Pinch Analysis, most approaches to design the heat recovery system as well as the utility system are based on a single operating point or a couple of operating points. In the past, this was due to the lack of temporally detailed process data,” the researchers explained. “However, the available process data is expected to increase drastically by the use of transient process simulation models.”

The researchers used software simulation to obtain detailed process data and utilized 8,759 time slices over one year, calculating an optimal set of heat pump parameters by mathematical optimization. For their case study, they chose an automotive paint shop, where variations in heating and cooling demands primarily arise from weather conditions.

The novel methodology considers different economic optimization objectives and is intended to minimize Opex over the whole year and maximize the net present value (NPV) of the heat pump investment. It also aims to maximize the internal rate of return (IRR) of the heat pump investment.

The scientists compared the performance of a system designed with the novel approach with that of a system conceived with the time average (TAM) model, as well as with that of a system based on an optimization method that considers the entire annual process data as well as NPV and IRR.

.“The TAM averages the heat loads over the batch period and allows for basic targeting,” the academics explained, noting that this configuration achieved a coefficient of performance (COP) of 2.56. “The integration of the TAM heat pump can already provide Opex savings of 1.75% but has very high Capex due to its large heating capacity. With an IRR of 18.4% and an NPV of €167,183 ($175,433), it is already a very worthwhile investment.”

The system designed with the novel technique, by contrast, achieved Opex savings of 3.94%, an IRR of 56.3% and an NPV of €610,15. Its COP was 2.41. When optimized to NPV, the novel method showed Opex savings of 3.93%, an IRR of 60%, an NPV of €615,989 and a COP of 2.48. Finally, when optimized for IRR, the OPEX savings were 2.93%, the IRR was 70.5%, the NPV was €476,556 and the COP was 3.17.

The scientists claim that, by utilizing the new methodology, a 33% smaller heat pump could be integrated. “The smaller size and greater savings show particularly in the evaluation of the profitability of the investments,” they concluded.

They presented their findings in the study “Heat pump integration in non-continuous industrial processes by Dynamic Pinch Analysis Targeting,” published in Applied Energy. The research group was formed by scientists from the German Aerospace Center and the Lucerne University of Applied Sciences and Arts.

Residents of Ireland can now use a new solar calculator to estimate how beneficial it would be to install PV systems (up to 6 kW) in their homes or businesses. The calculator is a joint project between the Irish Solar Energy Association and AirPV, an online solar platform.

“This calculator was years in the making,” Scott McKechnie, an AirPV spokesperson, told pv magazine. “It is the result of extensive work that focused on providing a tool that is simple to use, informative and realistic. Crucially, it can act as a transparent industry reference.”

Homeowners and businesses can now use a new calculator that – based on their postal code and adjustable settings such as PV system size, rooftop characteristics, and electricity usage details – provides estimates of their solar PV potential, including payback times, annual savings, and emission reductions.

“The accuracy of the calculator ultimately depends on the key models and assumptions, along with the user making appropriate choices that best match the situation at their home,” McKechnie said. “We chose the most accurate models. They provide a tradeoff between simulation complexity and accessibility for the user.”

Researchers from US-based space technology company Maxar Technologies have created a new dataset for residential PV system detection by using high-resolution satellite imagery.

“This dataset may be used independently or in conjunction with larger, non-satellite imagery datasets to produce robust detection models capable of generalizing across image types,” the scientists explained. “It may better support the use of satellite imagery in rapidly detecting and monitoring residential-scale solar panel installations, allowing researchers and policy-makers to address the needs of various applications.”

The dataset contains 2,542 PV systems located in southern Germany. The researchers explained that they chose this region due to the high concentration of both residential and commercial PV systems. After acquiring imagery of the area, they randomly chose three areas within the selected region and used software to identify the PV arrays.

They annotated individual solar panel objects manually and, in order to verify their identification, they compared the findings to images from Google Earth, which offers higher resolution images. Objects with potentially only one or two solar modules, either adjoined or separated, were considered as non-panel objects such as skylights, ventilation caps, and chimneys.

“In total, 2,487 solar panel objects, or 97.8%, were identified with high confidence,” the academics stated. “Less than 3.0% of the solar panel objects were identified with moderate or low confidence.”

The scientists said the novel dataset can be either used to develop detection models uniquely applicable to satellite imagery or in conjunction with existing solar panel aerial imagery datasets to support generalized detection models.

The dataset was introduced in the study “A solar panel dataset of very high-resolution satellite imagery to support the Sustainable Development Goals,” published in scientific data.

Maxar Technologies made both the image chips and the object labels available online.

Scientists from South Korea’s Inha University have developed a novel solar irradiance model that can purportedly predict data for a whole year with only two weeks of learning period.

The model is based on a reinforcement learning algorithm and is claimed to be particularly suitable with limited accumulated data.

“Reinforcement learning is an algorithm that independently maximizes rewards through trial-and-error within a given environment,” the academics explained. “This is the first attempt to use a reinforcement learning for solar irradiance prediction model.”

In the study “Solar irradiance prediction using reinforcement learning pre-trained with limited historical data,” published in Energy Reports, the researchers explained that the learning data was set for the first two weeks of the year, while the prediction period was set for the remaining part of the year.

As inputs for those two weeks, the scientists used real data from Cape Town, South Africa, based on four metrics – sky cover, temperature, humidity, and out-of-atmosphere solar irradiance. They then compared the analysis made by the model with that of two reference models based on long short-term memory (LSTM), which is a kind of recurrent neural network capable of learning order dependence in sequence prediction problems.

“The LSTM model is a type of recurrent neural network (RNN) deep learning,” the research group added. “It introduces a memory cell state to the RNN. The memory cell state demonstrates superior performance in managing long sequence inputs.”

On a monthly average, the researchers found that the proposed model had a prediction error 0f 31.5 W/m2, which represented a 7% variation from the actual data. In comparison, the two LSTM models used in the experiment showed an average error of 57.4 W/m2 or 12.8% and of 40.5 W/m2 or 9.2%, respectively.

Furthermore, the researchers ascertained that, with the proposed model, approximately 82.8% of the points were distributed within 10% of the upper and lower errors of the actual results. With the two LSTM models, these values decreased to 71.9% and 78.8%, respectively.

“The proposed model displayed more optimized performance with only two weeks of learning data when compared to previous studies which typically required several years’ worth of weather data for learning,” the researchers concluded. “In particular, the long-term performance of the model was improved by learning the out-of-atmosphere solar irradiance as an input.”

European researchers claim to have successfully demonstrated the embedment of organic PV (OPV) modules into structural plastic parts via large-scale industrial injection molding (IM).

IM is a manufacturing technique for producing parts by injecting molten material into a mold and has the ability, according to the research group, to enable the development of in-mold plastic solar cells with improved performance and stability.

“Due to their very thin layout, flexible solar cells can be sensitive to mechanical abrasiveness and, therefore, might require additional protection and integration strategies,” the research group explained. “Embedding a printed solar module into a plastic part simplifies integration challenges, while providing additional mechanical protection, shape adaptability, and streamlined contacts for connections.”

The researchers first created modules in roll-to-roll printing, using a photoactive blend known as P3HT:O-IDTBR. This blend was chosen due to its morphological and thermal stability, which are relevant to the later injection molding process.

“OPV product development demands photovoltaic materials with high morphological stability under thermal stress, such as the P3HT:O-IDTBR blend,” the academics emphasize. “In that respect, higher performing materials with such stability are urgently needed.”

The scientists inserted the modules horizontally into an injection mold of polyether copolymer-based thermoplastic polyurethane. This material was chosen due to its low process temperature, broad substrate compatibility, and flexibility. The injection was done using a 120 mm × 120 mm × 2 mm cavity insert, at a 90 mm −1s speed.

“From the selection of 64 roll-to-roll printed modules, 32 of them were injected, and the other 32 modules were kept as references,” the researchers explained. “On average, the IM-OPV modules retained 98.1 of the original performance. Only 2 samples failed, and 28 samples preserved over 90% of the original performance, which sets the yield of the IM process close to 90%.”

As for mechanical and operational stability, the scientists found an average of more than 35% increase in the maximum stress point in the IM-OPV samples. The first fracture on the control devices occurred at 10–30% of strain, whereas this value jumped up to 70–150% on the IM-OPV modules. In addition, a power conversion efficiency retention of more than 90% was found after 50,000 cycles in the molded modules.

“This work represents the first demonstration of in-mold plastic solar cells and opens new possibilities for organic photovoltaics to enable specific applications that require simultaneous high optoelectronic and structural performances,” the researchers said. “We believe that future focus on injection plastic materials could further extend the benefits of in-mold photovoltaics in regards to structural and device stability, or even providing additional optical functionalities.”

Their findings were introduced in the paper “Injection Molding Plastic Solar Cells,” published in Advanced Science. The researchers come from the Eurecat Technology Centre of Catalonia, the University of Pardubice and the Centre for Organic Chemistry in the Czech Republic, as well as from French nano-metal producer GenesInk and Spanish injection molding provider Aitiip.

Scientists from the University of Zaragoza and renewable energy developer Atalaya Generación have introduced a novel optimization method for the management of pumped hydro storage integrated with grid-connected PV and wind power plants.

They said they tested the model with real data, satisfying electricity demand and maximum profit.

“The goal of this study is to develop an hourly mathematical model that allows for the optimal management of grid-connected renewable generation facilities and pumped hydro-energy storage with reversible pump turbine,” the scientists emphasized. “The model can take advantage of opportunities in the electricity market through the purchase and sale of excess energy generated to the grid.”

In the paper “Optimal scheduling and management of pumped hydro storage integrated with grid-connected renewable power plants,” published in the Journal of Energy Storage, the research group explained that the model is based on a mixed-integer optimization problem, which is a type of mathematical problem often used in energy scheduling.

“The model incorporates the purchase of energy through a contract indexed to electricity prices in the wholesale market,” the academics explained. “This assumption allows us to obtain an optimal economic dispatch for every hour. In addition, the model includes the possibility of selling surplus production at a price set in the electricity market every hour.”

The model assumes that evaporation losses do not affect the performance of the system, and that wind and solar power prioritize meeting the electricity demand required by the system each hour.

The researchers have used 2019 generation data from existing plants in Spain’s Ebro Valley. These plants are represented by 860 MW of PV facilities, 456 MW of wind farms and a pumped hydro storage facility with a storage capacity of 5,750 MWh.  The wind farms are estimated to generate 1,352 GWh per year and the photovoltaic plants 2,065 GWh.

In order to analyze the techno-economic performance of the system, the scientists took as a benchmark the hourly prices of the Spanish wholesale electricity market set by the market operator OMIE in 2019. They compared the performance of the pumped hydro-wind-solar complex to that of a reference system without pumped hydro storage and found that the former reduces the cost of purchasing energy in the electricity market by up to 27 %.

“Compared to the case without storage, the integration of pumped hydro-energy storage reduces the amount of energy to be purchased from the electricity market to satisfy the demand by 20%, which implies an economic saving in the operation of the system of up to 27%,” they explained.

In addition, the scientists found that the system including the pumped hydro storage facility may help avoid energy curtailment.

“The application of the proposed model for the optimal operation of electrical systems based on renewable generation combined with large-scale pumped hydro storage helps improve the competitiveness and viability of power systems,” the researchers concluded. “The best decision is made every hour to reduce high energy costs and obtain efficient and resilient management of water use.”

“In other words, a decrease of the energy losses with the wind speed decrease,” the group said. “This apparent counter-intuitive argument follows the fluid mechanics theory, as the wind interaction with the PV generator induces air flux variations that modify the heat transfer from the modules to the air. The thermal behavior that leads to these losses is intrinsically linked with the airflow properties.”

The researchers also found that monthly mismatch losses follow the same patterns as daily losses.

“As the typical lifespan of a PV power plant may last some decades, this must represent an important uncertainty source to ensure the reliability of the PV plants,” they explained. “This suggests that the hitherto depreciated local wind patterns for energy estimations must be taken into account for a proper energy estimation during their lifespan.”

The station will features 25 Ioniq 5, a V2G technology developed by South Korean automaker Hyundai Motor. V2G technology is used to feed the energy stored in EV batteries back into national grids, which can help to stabilize power supplies during high-demand periods. However, in order for this technology to have a sufficient impact on grid operations, large-scale deployment is necessary.

Scientists from the Indian Institute of Technology Kharagpur have created a novel energy estimation model for bifacial PV systems which they claim can accurately predict irradiances for both sides of a prototype bifacial PV module.

The model is based on solar geometry, which measures the angle of the sun and the earth to calculate how much solar energy reaches a particular object.

“Our results suggest that the proposed model can be relied upon as a tool for accurately predicting the irradiance of bifacial PV modules,” the scientists said. “This validation is a significant step towards developing more precise energy estimation models for bifacial PV systems, which can contribute to optimizing their design and maximizing their energy output.”

While models calculating the energy reaching the front side of the PV are well established in scientific literature, this research contributes by calculating the energy reaching the rear side. It is based on two components – the reflected irradiance from the ground, and the rear side irradiance of the PV system.

“The amount of reflected irradiance depends on several factors, including the ground’s albedo, the module’s tilt, height, and solar zenith angle,” the paper explained. “Rear-side irradiance includes both the reflected and transmitted light that passes through the front side of the module.”

To validate this model, the academics compared their predictions with measurements from two pyranometers placed on each side of a PV system. That PV system is deployed with a fixed tilt angle of 22 degrees and is located on a building of the Indian Institute of Technology Kharagpur itself. The system consists of 18 bifacial PV modules with a total capacity of 6.8 kW.

“There was a high level of agreement between measured values and the model predictions, as indicated by the correlation coefficients of 1.04 and 1.40 for the front and rear sides, respectively,” they emphasized. “The correlation coefficient is a measure of similarity between the modeled and measured data, with higher values indicating a better match.”

In addition, the scientists have compared their model against actual results from an array elevated to one meter, with an albedo of 30%, under different tilt angles ranging from 0 to 90 degrees. “The proposed model exhibits a favorable agreement with the measured output, with an error rate of around 2–5%,” they said.

Furthermore, the researchers have also looked into the energy output at various elevations in optimum tilt angle. “Raising the array to a height of at least 1 m can significantly increase energy output, particularly at higher tilt angles. Moreover, using an elevated structure can further enhance the yield of a bifacial PV system by capturing more reflected irradiance from the ground,” they concluded.

The model is presented in the paper “Performance assessment of a bifacial PV system using a new energy estimation model,” which was published in Solar Energy.

“The research emphasizes achieving significant energy savings and improving indoor comfort through the integration of photovoltaic systems and bio-based materials,” researcher Sara El Hassani told pv magazine. “We used a combination of passive and active strategies – passive approaches include the use of local eco-materials for insulation, while active approaches involve the introduction of renewable energy techniques.”

Overall, the bio-based walls reduced simulated peak heating loads by around 24.3%, and decreased cooling loads by about 26.7%.

“All of these findings support the use of plant fibers as a sustainable practice in developing local and efficient adobes for improving passive heating and cooling in rural arid and semi-arid regions,” the scientists said.

Their study, “Towards rural net-zero energy buildings through integration of photovoltaic systems within bio-based earth houses: Case study in Eastern Morocco,” was recently published at Solar Energy. The research group includes scientists from Mohammed 1st University and the Green Energy Park. They said they will try to develop a standalone PV system within a bio-based building prototype in the future.