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TERRENUS ENERGY

Solar Panels

Module cleaning is just the beginning

Optimizing the performance of solar panels often comes down to ensuring their cleanliness. Levels and types of soiling, local weather conditions and the surroundings of your plant can lead to soiling problems and subsequent energy losses. Over the past year, ChemiTek has worked with O&M companies and PV asset managers to develop a range of products that will solve specific soiling challenges the solar industry is facing – and recent testing has yielded impressive results.

From pv magazine

Over the past six months, Portugal- based ChemiTek has tested a number of antistatic and hydrophobic coatings designed for solar modules. The coatings were tested at the “Green Energy Park” in Rabat, Morocco, and the results point to a bright future in their adoption.

However, the results also demonstrate that the coatings are most effective when tailored to environmental and climactic conditions. To meet this need, ChemiTek studies the different conditions of each solar park, down to the amount and type of dirt, the location of the panels and the weather, along with the cleaning method, all to ensure the solution meets the specific project’s needs.

Soiling losses 

Studies show that dirty panels can result in energy losses of up to 50%. ChemiTek has developed a range of agents to remove contaminants and harsh soiling, such as lichen, cement dust, gypsum, hard water, bird droppings, pollen, beeswax, and others.

For example, if a solar plant is affected by cement dust, stone dust, gypsum, and other alkaline contaminants, ChemiTek’s Cement Removal Agent (CRA) will react chemically with these contaminants, removing them in a highly effective way. 

Another problem that affects the production of energy from PV modules, and that can even damage the system, is the appearance of lichens, mosses, and other fungi on their surface, especially in very humid environments and in sites with large amounts of organic matter – near forests, agricultural plantations and so on. For this, ChemiTek has developed its Lichen Removal Agent (LRA). 

For the removal of organic dirt, such as pollen and bees’ wax, bird droppings, sand, dust, and resin, it is recommended to use the cleaning and protection solution Solar Wash Protect (SWP). SWP is not only highly effective in removing accumulated dirt, it also results in an antistatic coating that repels dust and prevents the adhesion of soiling. 

It is important to use the correct type of water in module cleaning, in order not to leave water stains on the module. Hard water – containing high levels of minerals and metal ions – can result in stains and deposits, which will block light transmission and can even lead to the creation of hotspots on the module. To solve this, ChemiTek has developed the Water Softening Agent (WSA), a biodegradable agent that captures minerals and metal ions, making the water completely safe to use for PV cleaning.

After cleaning care 

ChemiTek has several coatings that can be applied during or after cleaning and tested by TÜV Sud. Including antistatic coatings for dry and moderate climates and hydrophobic coatings for rainy environments.

SWP and Antistatic Solar Armor (ASA) are antistatic coatings. SWP and Antistatic Solar Armor (ASA) are antistatic coatings. SWP is a cleaning and protection product designed for manual cleaning and/or plants with heavy soiling. ASA, meanwhile, is an antistatic coating applied by professionals on solar plants in dryer climates, preferably used with semiautomatic equipment (for example, brush on a tractor and/or robot).

For locations with very humid and rainy weather, it is recommended the use of hydrophobic coatings, such as the D-Solar Defendor (DSD), which is for professional use and to be applied at high dilutions with brush on tractors or robots; and the Industrial Glass Protect (IGP) – an easy to apply, long-lasting (+5 years) coating that provides high hydrophobicity and is very resistant to adverse environmental conditions such as acid rain, high salinity, and extreme temperatures. The application of IGP can also lead to a reduction in the amount of cleaning required. 

Temperature-dependent model to calculate solar LCOE

Image: O’Connor College of Law/Flickr

Developed by researchers in Saudi Arabia, the novel approach considers both the temperature-dependent power yield and the solar module time to failure (TTF), among other factors. According to its creators, the model can be applied to all kinds of module and cell technologies.

From pv magazine

Researchers from Saudi Arabia’s King Abdullah University of Science and Technology (KAUST) have developed a temperature-dependent levelized cost of energy (LCOE) model for PV technologies that is claimed to be able to quantitatively translate the LCOE gain obtained by reducing solar module temperature. “Our model can be applied to all kinds of module and cell technologies,” the research’s corresponding author, Lujia Xu, told pv magazine. “It was validated through a series of tests conducted at an outdoor testing field located in Singapore.”

The model considers both the temperature-dependent power yield and the solar module time to failure (TTF), which calculates the time from when the panel is put into service until it fails. These two values were then unified in an equivalent ratio, designated with the Greek letter γ, which evaluates the influence of temperature on the performance of a PV system.

“This ratio expresses which absolute percentage in power conversion efficiency increase would be needed for achieving the same reduction in LCOE,” the scientists explained, noting that the model allows the prediction of a module’s temperature from the basic solar cell and module materials and device architecture properties. ” Whereas the temperature-dependent LCOE speaks to those working at system level, γ provides technologists working at the module and cell level with a more tangible metric.”

The model is said to enable the calculation of the total cell heating power by either adding the components contributing to the cell heating or by subtracting the electrical power output of the cell/module and the reflected/escaped power from the incident power. “We find that more than 60% of the incident solar power leads to cell heating,” the Saudi Group stated. “In addition, the encapsulation of the cells into modules further increases the heating power to over 65% of the incident power.”

In order to create a quantitative link between the module heating-power density and the module temperature, the scientists also developed an opto-electronically coupled thermal model to compare the thermal behavior of different cell technologies and investigate possible strategies for mitigating potential heating issues. “We found that the most effective and simple way to reduce the module temperature is to place the module in a windy environment with a proper mounting arrangement to enable effective heat transfer via convection,” the researchers concluded.

The proposed model was described in the paper Heat generation and mitigation in silicon solar cells and modules, which was recently published in Joule.

Author: Emiliano Bellini

MIT scientists develop waterless PV cleaning system

Image: Massachusetts Institute of Technology (MIT)

Scientists from the Massachusetts Institute of Technology have developed a system that can be operated at a voltage of around 12V, with a 95% recovery rate for lost power after cleaning. The waterless system can be operated automatically via an electric motor.

From pv magazine Global

Scientists from the Massachusetts Institute of Technology have developed a lab-scale solar module cleaning system prototype that uses electrostatic repulsion to cause dust particles to detach and virtually leap off the surface of panels.

They described the system in “Electrostatic dust removal using adsorbed moisture–assisted charge induction for sustainable operation of solar panels,” which was recently published in Science Advances. They said it is a device that is able to “actively charge” dust particles and impart strong Coulombic force for dust repulsion.

“Our approach overcomes the prior limitations that occur due to reliance on relatively weak, short-range dielectrophoretic/triboelectric force and eliminates the issue of electrical shorting,” the scientists explained.

The waterless system can be operated automatically via an electric motor and is activated by an electrode placed on top of the module surface. The electric charge it releases repels dust particles from the panels. The bottom electrode consists of a glass plate coated with a 5 nm transparent and conductive layer of aluminium-doped zinc oxide (AZO), using atomic layer deposition (ALD). It is mobile to avoid shading and moves along the panel during cleaning with a linear guide stepper motor mechanism.

The system can be operated at a voltage of around 12V. The researchers said that it can recover 95% of the lost power after cleaning for particle sizes greater than around 30 μm.

“We use Arizona test dust (intermediate and miscellaneous test dust fractions from Powder Technology Inc.), also known as crystalline silica dust, whose chemical composition emulates that of typical desert mineral dust particles in our experiments,” the researchers said.

One of the researchers, Sreedath Panati, said that the group performed experiments at a range of humidity levels, from 5% to 95%. “As long as the ambient humidity is greater than 30%, you can remove almost all of the particles from the surface, but as humidity decreases, it becomes harder,” said Panati.

The simulations showed that the electricity consumption of the device is negligible.

“There is no current flow between the top and bottom electrodes and therefore no electrical power consumption. The only mode of power consumption is that associated with the translation of the moving electrode,” they said, noting that more cost reductions could be achieved by further reducing the thickness of the electrode coating.

Author: Emiliano Bellini

Rollable CIGS solar modules from France

The modules weigh 1.5 kg/m². Source: Solar Cloth

From pv magazine

French start-up Solar Cloth has developed a copper, indium, gallium and selenium (CIGS) solar module for housing, greenhouses, aeronautics, mobility, sports and leisure applications.

The modules are manufactured with CIGS solar cells provided by US manufacturer Miasolé and have a power conversion efficiency of 17.6%.

“We are currently planning to set up a manufacturing facility in Mandelieu, near Cannes, together with our partner Soy PV, which is a new French CIGS platform for the manufacture of CIGS cells with electrolytic deposition,” Solar Cloth’s CEO, Alain Janet, told pv magazine. “The new production unit should be operational in April, with a capacity of 20 MW.”

The panels measure 1400 x 820mm and weigh 1.5 kg/m². The products are described by the manufacturers as rollable and extremely flexible modules, which do not contain breakable silicon or glass. “CIGS has a low carbon footprint of 12g to 20g CO2/kWh, and its recycling process has low impact and high value,” the manufacturer claims.

The module is also said to be adaptable to all kinds of textiles and was recently used for several tent lodges at the Paradise Springs California resort in the United States. The panels were deployed with a west-east orientation on both slopes of the tent lodges and connected to a battery with a capacity of 75Ah.

According to Solar Cloth, each of the tent lodges can now use on average 1,300 Wh per day and power a fridge, three portable lights, one lamp in the bathroom, one in the main room, a computer, three mobile phones, and other minor applications for a total output of 379 W.

“Solar Cloth participated last month in a European call for tenders, joining a consortium for the development of the perovskite/CIGS tandem solar cells,” Janet stated, referring to the latest steps the company has taken to further scale up its module technology.

Author: Emiliano Bellini

Source: https://www.pv-magazine.com/2022/02/22/rollable-cigs-solar-modules-from-france/

TOPCon vs PERC – a battle between fast learning curves

Panels at a 105 MWac project featuring Jolywood n-type TOPCon bifacial modules, in Oman. Source: Jolywood

From pv magazine

TOPCon solar modules will gain more market share if their average efficiency, already higher than that of PERC panels, continues to improve, according to Stefan Glunz, PV research chief at Germany’s Fraunhofer Institute for Solar Energy Systems ISE. In an upcoming pv magazine webinar on the potential of TOPCon tech, Glunz will show how to reduce costs and increase efficiency.

TOPCon photovoltaic technology is constantly gaining new market share across all segments and is the most serious candidate to challenge the primacy of PERC solar panels. However, success will depend on several variables that are still difficult to decipher.

“The TOPCon PV tech has a very high-efficiency potential achieving already 26% in research that explains its current uptake,” Stefan Gunz, the head of division photovoltaics – research at Germany’s Fraunhofer Institute for Solar Energy Systems ISE, told pv magazine. “However, the PERC panel technology has also a very fast learning curve and the balance between them will depend on which one will be able to increase its efficiency or reduce cost faster than the other one.”

He said TOPCon products will have more opportunities to gain ground in the race if their average efficiency, which is already comparatively higher than that of PERC products, is further raised.

“There are still margins for TOPCon manufacturers to reduce costs, especially regarding the deposition of intrinsic/doped polysilicon,” he said. “But the real step forward may be taken by further increasing their efficiency, which would ensure that the possibly slightly higher costs related to TOPCon production will be more than justified, as TOPCon panels have higher efficiency and energy yield.”

However, it remains unclear how much their efficiency should be increased.

“Manufacturers are not very transparent about their current achievements,” the German scientists said. “And this doesn’t make it easy to understand which new TOPCon panels may really resemble PERC products in terms of a good trade-off between costs and performance.”

Stefan Glunz. Source: Fraunhofer ISE

The future also remains difficult to forecast.

“As always, predicting the market share of TOPCon is a look in the crystal bowl, however since PERC, as the dominating cell technology, has a large technological overlap with the TOPCon route, the change can be quite smoothly similar to the transition from aluminuim back surface field (Al-BSF) solar cells to PERC devices,” said Glunz.

Glunz and other scientists from the Fraunhofer ISE and University of Freiburg in Germany described the trajectory of the TOPCon technology in “Silicon-based passivating contacts: The TOPCon route,” which was recently published in Progress in Photovoltaics.

The study dates back to the 1980s, when the first attempts to use polysilicon layers under the contacts to reduce recombination in silicon solar cells were published.

“No details of the fabrication process of these passivating contacts have been published. Given the respective expertise of SunPower demonstrated by their patent portfolio, it appears likely that poly-Si/SiOx contacts were used,” the paper reads.

The first TOPCon cell, for which the use of poly-Si-SiOx contacts was officially unveiled, is a 23%-efficient device, with a high open-circuit voltage of 698mV, built by Frank Feldmann from the Fraunhofer ISE in 2013. It was a both-sides contacted device that was very similar to the current industrial cell structures.

“The recombination properties of the first n-type TOPCon cells were mainly limited by the recombination at the front contacts,” the researchers explained, noting that the technology has experienced a renaissance in the past decade. “In fact, the introduction of a local p++ boron diffusion under the front contacts and other improvements led to a record efficiency of 25.8% (Voc = 724 mV) on n-type TOPCon cells.”

Glunz also noted that a recent TOPCon cell structure featuring a back junction on p-type silicon even resulted in an efficiency of 26%, with an open-circuit voltage of 732mV.

The research group identified four research topics that are currently being addressed to improve the technology: the need for re-parametrising intrinsic recombination in the silicon due to the excellent surface passivation of TOPCon structures; improving control of diffusion of dopants through the intermediate SiOx layer to optimise passivation and transport properties; the single-sided deposition of the poly-Si layer to reduce process complexity for industrial TOPCon cells; and the utilisation of silicon-based tunnel junctions in perovskite–silicon tandem cells based on a TOPCon design.

“Especially the singe-sided deposition of the poly Si layers, or the corresponding single-side etch in case of both-side deposition, together with a lean metallisation route for TOPCon cells are currently of high importance for the industrial introduction of TOPCon,” Glunz said.

He added that the TOPCon PV technology will possibly co-exist with PERC and heterojunction modules in the current decade.

“Since TOPCon and PERC cells share a lot process steps, we might see a quite big market share of this TOPCon in the future,” he said.

Author: Emiliano Bellini

Soruce: https://www.pv-magazine-australia.com/2022/02/16/topcon-vs-perc-a-battle-between-fast-learning-curves/