Light-scattering structures to boost solar performance

Scientists at Penn State have found that a light-scattering structure could improve perovskite performance. Image: Penn State

An international team of scientists developed a nanoparticle structure which, when added to a solar cell, was shown to scatter light and potentially reflect it many times within the cell, contributing to a noticeable jump in current.

From pv magazine

A range of different additives and extra layers could change the way a solar cell surface interacts with light, and thus improve its performance. Among these is light scattering, where sunlight hits tiny particles embedded into the cell, and is reflected around the device rather than straight back out of it.

A group of US scientists led by Penn State University have demonstrated a 1% efficiency increase in perovskite solar cells by adding a nanoscale light trapping structure to the front of the cell. The achievement is also notable they started out investigation a completely different route to solar cell optimization, and ultimately discovered most of the gains thought to come from this are actually attributable to an accompanying light scattering effect.

“Some researchers in the literature have hypothesized and showed results that up-conversion nanoparticles provide a boost in performance,” said Shashank Priya, professor of materials science and engineering at Penn State. “But this research shows that it doesn’t matter if you put in up-conversion nanoparticles or any other nanoparticles – they will show the boosted efficiency because of the enhance light scattering.”

Up-conversion is a process where a material added to a cell converts infrared radiation into visible light, which can be absorbed by the solar cell. This has long been pursued as a possible to way to reach efficiencies beyond what is thought to be theoretically possible in a single junction device. In this case, scientists at Macquarie University in Australia provided another crystalline material that does not exhibit the up-conversion effect, allowing the Penn State researchers to compare results.

They described their work in “Homogenization of Optical Field in Nanocrystal-Embedded Perovskite Composites,” which was published in ACS Energy Letters. The results showed that the materials were equally effective in improving the perovskite solar cell’s conversion efficiency. And with further calculations, the researchers were able to prove that the efficiency boost primarily came from light scattering, with up-conversion only having a negligible effect.

“We started to basically play around with nanoparticle distribution in the model, and we started to see that as you distribute the particles far away from each other, you start to see some enhanced scattering,” said Thomas Brown, associate professor at the University of Rome. “Then we had this breakthrough.”

The group says it will now investigate the optimization of the size, shape and distribution of particles in nanostructures to optimize performance even further.


Solar-plus-storage for LED lighting in commercial buildings

An LED array in a floodlight. Image: Gaurav_Dhwaj_Khadka, Wikimedia Commons

Indian researchers claim that commercial buildings with LED lighting could gain energy independence by installing standalone solar-plus-storage systems. They said a 914.4 kW PV system linked to lithium-ion batteries could be enough to power an entire building with an estimated annual demand of 190,830.7 kWh.

From pv magazine

Scientists from India’s Techno India Salt Lake (TISL) research institute have looked at how standalone photovoltaics linked to lithium-ion battery storage could be used for LED lighting in commercial buildings. They aim to develop a way to use solar power for LED illumination systems in order to reduce electricity costs.

“The scope of the work is to design an effective solar photovoltaic system which would meet the complete energy demand of a proposed business complex without consuming conventional energy supply,” they said.

In “Design of LED lighting system using solar powered PV cells for a proposed business complex,” which was recently published in Scientific Report, the researchers said that commercial PV projects for LED lighting should follow nine steps. They include the identification of a location, the determination of a grid connection point, and the pre-construction documentation and negotiations. The scientists also noted the importance of building infrastructure such as roads and fences, purchasing equipment and logistics, installing mounting structures, building transformer substations, setting up grid connections, and installing monitoring systems.

The academics assumed that the PV system would be built with 6,097 solar modules, with power outputs of 150 W and a total capacity of 914.4 kW. They also assumed the array’s tilt angle to be 49.3 degrees. The PV array design would have 41 stings and 24 modules in series.

In addition, they included an adjustable lithium-ion battery with 512 cells, with 16 connected in series and 32 connected in parallel. For the commercial building complex, the scientists assumed annual electricity demand of 190,830.7 kWh.

“The battery is to be operated at standard room temperature at 24 C in a fixed air-conditioned room,” they said.

The scientists concluded that the standalone energy system would provide complete energy independence for the building. The solar array’s transposition factor could reach a value of 0.98 in the proposed system configuration, they noted.

The modeling also showed that the system’s solar fraction and performance ratio achieved values of 0.740 and 0.569, respectively. The latter measures the quality of a solar plant, independent of location, and the former defines the percentage of the total thermal load satisfied by solar energy. 

“The cost estimation shows that the acquisition and installation cost of PV systems is economically feasible for a typical business complex,” the research team said. ” It is very much possible to use them in individual buildings to attain complete energy independence in the future.”


Tigo releases design quality tool for large commercial solar

Image: Tigo Energy

The US module level power electronics provider also introduced an installer certification course.

From pv magazine

US-based DC power optimizer specialist Tigo Energy unveiled a new design quality tool called the Solar PLC Signal Integrity Tool alongside expanded training material for solar engineering, procurement, and construction firms in the commercial and industrial segments.

The validation tool and accompanying training course help installers preempt powerline communications (PLC) signal integrity issues in large-scale commercial and industrial projects. PLC signals can experience “crosstalk”, disturbances in signals that can lead to reduced effectiveness of communications in large-scale PV systems. The updated TS4 Design and Installation Course now includes best practices for mitigation of PLC crosstalk issues at the design stage, preventing issues before they happen.

Tigo also released the Solar PLC Signal Integrity Tool, which can be used to identify crosstalk issues in active solar arrays. The tool is designed to be vendor-neutral and is usable for either Tigo systems or competitor MLPE products. After the PLC assessment is run, Tigo provides a performance score.

The TS4 design and installation course, integrated into the company’s education plaftorm, features a section on PLC rapid shutdown system design as well as a technical deep dive into the Tigo TS4 Flex MLPE product line. It provides best practices and practical guidance for system optimization, and installer education on how to design, install and commission a Tigo system with any compatible solar inverter. The two-hour comprehensive course earns 1.5 NABCEP continuing education credits.

“An important part of our mission at Tigo is to keep installers at the center of everything we do, and investing in tools and training is no small part of that,” said JD Dillon, chief marketing officer at Tigo Energy. “As our partners in the field raise their stakes with ever larger installations, we are supporting them with things like this new PLC Tool, Pure Signal technology, and impactful continuing education to help them design and support the highest quality PV installations.”

Last month, Tigo introduced a solar rapid shutdown device with “Pure Signal” technology, aimed at improving PLC signal quality. Tigo RSS Transmitters with Pure Signal technology are UL PVRSS certified with hundreds of inverter models from leading manufacturers. The new transmitters with Pure Signal technology are compatible with the company’s TS4-A-F and TS4-A-2F rapid shutdown product family and can be easily integrated into new projects or retrofitted into existing installations.

“Our mission is to provide high-quality, reliable, and flexible MLPE solutions to meet customers’ needs for different system configurations. Pure Signal technology delivers on that mission,” said Jing Tian, chief growth officer at Tigo Energy.


World could install 250 GW of solar this year, claims Bloomberg analyst

Image: Recurrent Energy

Rob Barnett, a senior clean energy analyst for Bloomberg, forecasts a 30% increase in global PV deployment this year, and double-digit growth through 2025.

From pv magazine

Demand is pushing solar growth across the world to new heights, as Bloomberg senior analyst Rob Barnett forecasts deployment to increase by 30% this year. Total global solar deployment is closing in on 1 TW installed – an impressive milestone for the energy transition.

“The global solar picture is just staggering at this point,” Barnett told Yahoo Finance. “We are on track to install something like 250 GW of solar capacity this year.”

China is contributing the largest share to capacity growth this year, with about 108 GW of new operational PV. This is a near-doubling of the roughly 55 GW installed by China last year. The country has the world’s largest exposure to renewable energy, with 323 GW of solar and 338 GW of wind energy. President Xi Jinping aims for 1,200 GW combined by 2030, and the nation is currently ahead of schedule on that goal, said Bloomberg.

Renewable energy is hitting all-time highs in the United States, too. Renewable generation from solar and wind installations reached 28% in April – a new record for the category. And Barnett said the solar boom has just begun.

“There really is this big, top-line growth scenario that we see unfolding for all of the companies that are participating in the solar supply chain,” said Barnett.

Climate goals are one driver of the red-hot demand for solar, but Barnett said there is another force that is accelerating demand in the near-term.

“I would actually argue that the bigger driver for clean energy demand, particularly here in Europe, is elevated energy costs,” he said.

Costs continue to fall for PV, making it increasingly cost-competitive with oil, which has spiked in price since the Russian invasion of Ukraine. Shipments of solar modules have fallen precipitously over 20 years, from $4.88/W in 2000 to $0.34/W in 2021, based on a recent report by the Energy Information Administration.

Barnett said he expects solar demand to retain its momentum, even if oil and natural gas prices cool off.

“It’s certainly possible that if you had some easing in the traditional fuel markets, that it might take the accelerator off, but I don’t really see that as being a material risk on the demand side of the equation for clean energy,” he said.

This demand-side momentum is likely to continue as prices improve and the global economy targets decarbonization.

“I do think that the economics are already quite good. And so you’d have to see such a sea change in terms of gas prices or coal prices, if you’re thinking about the power grid, to really reverse some of the trends. And I just don’t think there’s any appetite for it either,” said Barnett.


Straight to storage via solar integrated batteries

A solar redox flow cell (SRFC). Image: University of Porto

Scientists in China evaluated the prospects for various approaches to integrating both solar generation and energy storage in a single device. Their work outlines several ways this could increase the efficiency of solar energy storage, and recommends that future research on this area should focus on integration of materials with the highest specific capacity for energy storage, alongside the dual function of solar energy harvesting.

From pv magazine

Maximizing the efficiency of energy storage, to make good use of every electron generated from intermittent renewables, will be an ongoing challenge for scientists over the coming decades, and one that will likely see a whole host of new technologies and materials introduced to increasingly specialized markets.

Among the less explored approaches here is single-device integrated solar generation and energy storage, or solar-powered redox batteries (SPRBs). These promise to eliminate much of the additional power electronics and other equipment needed to shuttle energy from a PV system to a battery, meaning both cheaper and more efficient energy storage. So far, a few different approaches to fabricating such a device have emerged, and while progress has been made, none has yet achieved the type of performance that would bring interest from commercial developers.

Scientists led by China’s Nanjing University of Information Science and Technology conducted an extensive review of recent progress with SPRBs, focusing on the development of high-performance dye sensitizer materials, the photoelectrochemical performance of different electrode materials, and the mechanism and structure of such devices. Their review and recommendations can be found in the paper Integrated Photovoltaic Charging and Energy Storage Systems: Mechanism, Optimization, and Future, published in Small.

The paper notes that dye sensitizer materials and semiconductor photocatalysts have shown the most promising results so far, and recommend a range of strategies focused on enhanced light absorption, charge separation, energy matching and overall device optimization. It also states that working with materials that exhibit a high specific capacity for energy storage will be key in developing commercially relevant types. If this potential can be realized, the review finds multiple applications including capacitors, solid-state batteries, microdevices, and smart wearables that could all benefit from such integrated technology.


Forecast methodology for photovoltaic power yield during solar eclipses

Image: Doinkster, pixabay

In October there will be a partial solar eclipse in Central Europe. The Fraunhofer IEE has developed a solution that reportedly enables the most accurate forecast possible of the photovoltaic feed-in power during the extreme event.

From pv magazine

The more photovoltaic systems are installed, the more relevant are precise forecasts of how their feed-in will develop in the event of weather events such as solar eclipses. Extreme meteorological events in particular pose major challenges to secure network operation.

Researchers at the Fraunhofer Institute for Energy Economics and Energy System Technology (IEE) in Germany have addressed this issue by developing a new forecast methodology that will soon be tested under real conditions. On October 25, in fact, there will be a partial solar eclipse in Central Europe, which will significantly reduce the photovoltaic feed-in. So far, such rare extreme events have not been routinely included in weather forecasts.

The scientists claim their solution is able to combine the degree of coverage specifically for location and time with all important weather forecasts. This would allow regional and local PV feed-in forecasts to be optimally adjusted in the future, with minimal errors.

Although the effect of the solar eclipse is slower and smaller than the influence of changing clouds, it still plays a significant role in the result. Volatile self-consumption also has a massive effect on the feed-in profile of photovoltaic systems, which can be forecast separately, according to the researchers.

Fraunhofer IEE validated its results with the data from the eclipse that occurred in Central Europe on June 10, 2021, in two steps: through ground-based measurement of global radiation based on data from German weather service DWD and feed-in measurements from thousands of photovoltaic power plants that are used for extrapolation and forecasting processes. The simulation also included weather forecasts and performance data from Fraunhofer IEE. The solution is also available as an algorithm or software for direct integration with the user.

The researchers are considering the proposed methodology as a tool to further strengthen the grid integration of renewable energy sources in Germany. For new locations or regions that have not yet been measured, an extrapolation process is possible by using current measurements from comparable areas and systems.

The October solar eclipse, with a 25% degree of coverage, will be about twice as strong as the result in June 2021, according to the researchers. Weather forecasts a few days beforehand are expected to provide information about cloud density and the effects the solar eclipse may ultimately have.

“In addition to the already good forecast models for the feed-in of individual photovoltaic parks or entire portfolios — including self-consumption — an important contribution can be made to avoiding or reducing errors,” said Rafael Fritz of Fraunhofer IEE.


Solar tree-based photovoltaic plants for mountainous areas

Solar tree installed around the space used as farmland. Image: Korea Maritime Institute, scientific reports, Creative Commons License CC BY 4.0

Scientists in land-scarce Korea are proposing to use solar trees to build PV installations in forest areas. Although more expensive than conventional ground-mounted facilities, solar plants made of solar trees may capture carbon from forest land and produce energy at the same time.

From pv magazine

Researchers from the Korea Maritime Institute have proposed the use of solar trees to build photovoltaic plants in mountainous forest areas in land-scarce South Korea.

They defined the new concept as forest-photovoltaic and explained that it would both maintain carbon absorption activities under the solar trees and produce solar power on the upper part of forest land.

“Compared to a general flat fixed panel, the solar tree has a higher structure and a stronger support base, increasing construction costs,” they explained. “As the demand for solar trees increases due to the development of new technology, more companies enter the market. Therefore, it is expected that solar trees can be installed at a cost that can compete with the current flat fixed panel in the not-too-distant future.”

Using Google Earth satellite imagery, the Korean group assessed the concept’s operational potential by simulating solar tree installations in a mountainous area at 400 meters above sea level, where there is an operating agrivoltaic plant relying on solar trackers. “The solar power plant was constructed by cutting a mountainous ridge available in the highly elevated plateau into flat land,” they explained. “The solar panels installed on the 3-meter-high structure made a space for farming in the ground. One kind of ginseng, mountain garlic, is being grown in the space at the bottom of solar power facilities.”

The academics used Google Earth 3D to reflect solar tree size and the distance between the trees. As a reference, they considered a 4.8 m × 4.1 m panel with a rated power of 1.2 kW developed by Korea-based module manufacturer Hanwha Q Cells. “The slope distance was measured using the built-in elevation path measurement function in Google Earth Pro to arrange the solar tree at 100 m intervals in the three-dimensional image,” they specified. “The forest area, solar panel, and open space were calculated using the polygon measurement function provided by Google Earth Pro to quantitatively evaluate changes in mountain landscape before and after solar tree installation.”

The researchers performed their analysis with criteria developed by Germany’s Fraunhofer Institute for Solar Energy Systems (ISE) for agrivoltaic projects. One of the important factors they considered is the distance between the solar trees, which is crucial for determining their impact on the surrounding natural environment. They ascertained that, if the trees are installed according to the scale of the 3D image, a considerable number of solar trees could be deployed throughout the 1,100,872-square-meter study area. If too many solar trees are placed in a limited space, however, the solar trees displayed as too small in size, causing significant limitations in terms of visual effect, they noted.

Despite their higher costs compared to conventional PV installations, solar trees may have a strategic advantage as they occupy a much lower amount of land. “The land purchase cost is the most important parameter in calculating LCOE on the solar power plant in South Korea,” the research team said. “Compared to other countries, South Korea ranks third in the world in terms of land price. So, purchasing the land is much higher than the money required to build a solar power plant.” On the other hand, in the South Korean Energy Agency’s most recent renewables auction, the final average price was KRW 143.120 per kWh ($0.11), which shows prices quite above the average prices seen in the world’s largest and most mature solar markets.

“The solar tree has not been popularized yet, so the forest-photovoltaic field has many problems to be solved and is only in its infancy,” the scientists admitted, noting that most major module manufacturers haven’t entered the business yet. “The procedure for the solar tree to be commercialized has to deal with different international standardization and regulation schemes.”

They introduced their concept in the study “Exploring the operational potential of the forest-photovoltaic utilizing the simulated solar tree,” published in scientific reports. “A follow-up study is needed to initiate legally binding international standards for solar trees’ wind and snow load operation,” they concluded.


The PV cooler lifespan effectiveness factor

A flowchart for the proposed method. Image: Universiti Sains Malaysia, Case Studies in Thermal Engineering, Creative Commons License CC BY 4.0

Researchers in Malaysia have defined a new parameter to evaluate solar module cooling techniques based on their lifespan effectiveness. They warned that the proposed methodology should be utilized only with standard test conditions, a temperature of 25 C, and a reference PV system without the cooling system.

From pv magazine

Scientists at the Universiti Sains Malaysia have developed a novel methodology to evaluate the effectiveness of solar module cooling technologies based on their lifespan. “The relation between the lifespan of PV and its cooler is not discussed in previous studies which are analyzing only the separate systems either the lifespan of the PV or the cooler,” they specified, noting that a performance comparison between the different types of cooling technology is not an easy task to accomplish.

The researchers defined a new parameter – the PV cooler lifespan effectiveness factor – which they claim makes it easier to carry out the above-mentioned performance comparison. It defines the ratio of the lifespan of the cooling system to the lifespan of the PV array.

They warned that the proposed methodology should be utilized only with standard test conditions, a temperature of 25 C, and a reference PV system without the cooling system. “The lifespan of the material depends on weather conditions which are different from one region to another,” they explained. “Hence, the value of the PV cooler lifespan effectiveness factor will be different. This could be a limitation of the proposed method.”

Their analysis showed that there is a proportional relationship between the lifespan of the cooling system and the new factor, as well as an inverse proportional correlation between the PV lifespan and the new factor. “The PV cooler is considered to be a lifespan effective, if the lifespan effectiveness factor is greater than zero and lesser than or equals to unity,” the academics stated, referring to the scale they created to measure the effectiveness factor.

They described their findings in the paper “A new method for assessing photovoltaic module cooler based on lifespan effectiveness factor,” which was recently published in Cases Studies in Thermal Engineering. “This factor may have an implication of the classification and the decision on the PV cooler types,” they concluded.


Vehicle-integrated photovoltaics for low-speed electric vehicles

Image: Capsolar

Canadian startup Capsolar claims its flexible solar modules can be adapted to any type of low-speed electric vehicle with no extra modification and custom work. The panels have an efficiency of 21.3% and rely on 24%-efficient solar cells provided by US manufacturer SunPower.

From pv magazine

Quebec-based startup Capsolar has developed a solar panel for vehicle-integrated applications.

“The CAPSolar’s SM–550 solar module is capable of maximizing the capture of solar energy in a dynamic setting by reducing the impact of shading on its performance while being as robust and lightweight as possible when fitted on our structure which can fit any type of low-speed electric vehicle,” the company’s CEO, Samy Benhamza, told pv magazine.

The module has a size of 2,100 mm x 1,320 mm x 25 mm and weighs in at 30 kg. It has a power conversion efficiency of 21.3%, an open-circuit voltage of 108.0 V, a short-circuit current of 6.4 A, and a fill factor of 76%. It can be operated with a maximum temperature of 45 C while driving and 55 C when the vehicle is parked.

The panel relies on 24%-efficient solar cells provided by US manufacturer SunPower. It also features an IP67 enclosure and an MPPT buck controller. “The solar panel itself is fully flexible but when mounted on our structure, it conforms to the desired shape and becomes rigid. In its layout, strategically oriented solar cell series help in better managing different incidence angles and combined with multiple bypass diodes, we have an optimal shading management,” Benhamza said.

According to the manufacturer, the panel offers a 70% higher daily energy output at the same power rating as competitor products. The company tested the module in Montreal, Quebec, on a client’s vehicle and claims it achieved a 17% average range extension per day, with a peak of 26% on sunnier days.

“In collaboration with our European strategic partners in Belgium, we have developed a patent-pending, fully modular system that allows us to adapt our panels, just like LEGO, for each type of low-speed electric vehicle with no extra modification and custom work,” Benhamza explained.

Capsolar is currently collecting data to better determine the parameters that have the most impact on the performance of a vehicle–integrated solar module. “We will then be able to feed this data to the charge controller we are designing and use artificial intelligence to optimize the operating parameters of the MPP–tracking algorithm,” Benhamza concluded.


Solar thermal panel for large scale applications

The MT-Power panels. Image: TVP Solar

The panel has an absorption area of 1.96 m2 and a weight of 27 kg per square meter. According to the manufacturer – Swiss startup TVP Solar – it may be a real booster for thermal output, by combining it with photovoltaics and heat pumps to provide enhanced output per square meter, in particular for low-temperature applications such as district heating.

From pv magazine

Swiss startup TVP Solar has developed a solar thermal panel that can produce hot water or steam at between 80 C and 180 C for industrial process heat, district heating, and air conditioning. “Typical applications are large scale solar plants dedicated to solar heat for industrial processes (SHIP), providing pressurized hot water or steam up to 180 C to industries such as food & beverage, chemical, textile, paper, oil and gas, mining, and automotive,” TVP Solar’s Vice President Business Development, Guglielmo Cioni, told pv magazine. “All of these industries have a major share of fuel consumption to produce heat below 180 C of temperature.”

The company said its MT-Power panel exhibits minimal thermal losses and no degradation over time, with an average thermal efficiency of up to 64.5% and a peak thermal efficiency of 68.6%. “The efficiency can also be higher, depending on temperature,” Cioni stated. “It may be a real booster for thermal output, by combining solar thermal to photovoltaics and heat pumps to provide enhanced output per square meter, in particular for low-temperature applications such as district heating.”

The panel has a flat design and was developed with a high vacuum flat panel (HVFP) technology developed by the European Organization for Nuclear Research (CERN). “No other non-concentrated solar technology can claim such performance,” Cioni stated “TVP Solar’s super-performing flat collectors produce heat throughout the year in most climatic conditions and geographies cheaper than liquid fossil fuels.”

The panels are built with heat absorbers with heat transfer fluid pipes welded to coated absorber sheet, a glass cover with an embedded peripheral frame, and a lightweight metal backplate. The modules are initially encapsulated with glass-to-metal sealing, which ensures durability of over 25 years, according to the manufacturer. They then go through automated vacuum-type welding of the peripheral frame and a differential exhaust process via a tunnel oven.

The panel has an absorption area of 1.96 m2 and a weight of 27 kg per square meter. It is reportedly able to generate up to 1200 kWh of thermal energy per square meter per year depending on solar irradiance and operating temperature.

TVP Solar is currently operating a 5,000 m2 manufacturing facility in Avellino, southern Italy. The factory has a fully automated line with a capacity of 110,000 m2 per year. Several systems built with its modules are currently operating across several demonstration sites.

“The size of our projects did not exceed 1 MW until 2021, but now we are only targeting projects over 1 MW, and we believe that, especially in combination with thermal storage and advanced control and management systems, our module technology may be used in projects of up to 100 MW,” Cioni explained. “Further standardization of the Balance of System (BoS) is being designed for such projects, including the expansion of the existing supply chain for the BoS.”

The existing plants were installed in Italy, France, Switzerland, UAE, Kuwait, Saudi Arabia, USA, Brazil, Spain, Germany, the Netherlands. “Our target is to continue to operate in these markets and to expand globally within five years,” Cioni concluded.