Solar window generates electricity, thermal energy

Image: Hong Kong University of Science and Technology, Advanced Science, Creative Commons License CC BY 4.0

A research team in Hong Kong has built a solar window that can generate power on the external side via a luminescent solar concentrator and thermal energy on the internal side via transparent solar absorbers.

From pv magazine

Scientists from the Hong Kong University of Science and Technology have developed a dual-band selective solar harvesting (SSH) window based on transparent photovoltaics (TPVs) and transparent solar absorbers (TSAs). The TSAs are used to convert ultraviolet (UV) or near-infrared (NIR) light by converting it into thermal energy.

“The harvested thermal energy is extracted by ventilated air to provide indoor space heating in cold seasons or abate indoor cooling loading in hot seasons,” they explained. “We demonstrated that the SSH window has a visible transmittance of 42%, achieves a solar-electricity conversion efficiency of 0.75%, and a solar-thermal conversion efficiency of 24% with a ventilated air temperature rise of 10 C.”

The research group used a luminescent solar concentrator (TPV) based on copper indium sulfide and zinc sulfide (CuInS2/ZnS) quantum dots (QDs) as the exterior window. It is able to collect UV light and convey it to opaque PV devices that are located at the edge of the transparent substrate for electricity generation. The TSAs were instead used to fabricate the interior side of the window where heat is produced and collected.

“The thermal energy is mostly extracted by the ventilated air within the gap for various purposes such as indoor space heating in cold seasons,” the group said.

The academics fabricated a prototype measuring 30 cm x 30 cm x 2.4 cm by assembling the TPV elements with the TSAs on the interior side. They claim the device showed a substantial visible transmittance and that it was able to generate 6 W per square meter of power and the thermal power of around 150 W per square meter.

“Thermal power is 25 times of the generated electrical power, suggesting that the harvesting thermal power is of primary importance for building-integrated solar energy harvesting windows,” they said. “With thermal energy harvesting by air ventilation, the total effective efficiency was estimated over 30% at a typical operating condition for building space heating applications.”

They presented their findings in “Selective Solar Harvesting Windows for Full-Spectrum Utilization,” which was recently published in Advanced Science.

“The SSH window can save the annual heating, ventilation, and air conditioning (HVAC) energy consumption by up to 61.5% compared with the normal glass, in addition to the generated electricity that accounts for up to 19.1% of the annual energy saving amount,” they said.

Author: Emiliano Bellini

JinkoSolar showcases 13.08%-efficient transparent TOPCon solar module for BIPV, agrivoltaics

The solar panel measures 1,1759 mm × 1158 mm × 11.5 mm, has a weight of 54 kg. Image: JinkoSolar

The new solar module can be purchased with different levels of transparency, depending on the project, with light transmittance ranging between 30% and 40%. It has a power output of 245 W to 300 W and a temperature coefficient of -0.30% per C.

From pv magazine

Chinese module manufacturer JinkoSolar launched a new transparent solar module for applications in building-integrated photovoltaics (BIPV) and agrivoltaics at the recent Smarter E event held in Munich, Germany.

“The Jinko Transparent Curtain Wall Series is based on our n-type TOPCon HOT2 cell technology,” a company spokesperson told pv magazine. “It can be purchased with different levels of transparency, depending on the project. Light transmittance ranges between 30% and 40%.”

The panel has a power output ranging from 245 W to 300 W with the power conversion efficiency spanning from 12.09% to 13.08%. The open-circuit voltage is between 25.6 V and 28.5 V and the short-circuit current is of 12.09 A to 12.93 A.

It measures 1,1759 mm × 1158 mm × 11.5 mm, has a weight of 54 kg and its temperature coefficient is -0.30% per C.

The operating ambient temperature ranges from -40 C to 85 C, said the manufacturer, and the maximum system voltage is 1,500 V. The panel has 6 mm of toughened glass on both sides and its junction box has an IP 67 rating.

Jinko offers a five-year product warranty and a 25-year power output guarantee. The panels are said to be able to operate at 90% of their original performance after 10 years and at 80% in the remaining 15 years.

“The product is also available in different colors and can be adapted to modern architectural concepts,” the spokesperson said. “The dual glass configuration ensures lower crack diffusivity and corrosion resistance.”

Author: Emiliano Bellini

Novel way to turn semi-finished thin-film solar modules into colored BIPV panels

From left to right: Maximilian Götz-Köhler, Nils Neugebohrn, and Norbert Osterthun. Image: DLR Institute of Networked Energy Systems

German scientists have developed a way to cut semi-fabricates into desired shapes and then apply a conductive oxide-metal-oxide electrode with the preferred color. They can structure the elements into modules via the backend interconnection process.

From pv magazine

A group of scientists in Germany has come up with a new way to refine conventional thin-film panels into building-integrated (BIPV) products. They claim that their approach can reduce production costs, while ensuring supply chain flexibility.

“This approach can not only reduce costs, but also opens up the possibility of separating the production process into the manufacture of semi-finished PV products and their refinement into colored BIPV modules,” they said. “For example, semi-finished PV panels could be produced in Asia and the refinement can be done locally in Europe.”

The proposed technique consists of cutting the semi-fabricates into desired shapes and then applying a conductive oxide-metal-oxide (OMO) electrode with the requested color. The elements are then structured into modules via the backend interconnection process.

“All materials and methods, including sputtered aluminum oxide and silver layers, are widely available in the industry and are part of other products which are mass-produced, like climate glass for windows,” researcher Nils Neugebohrn told pv magazine.

The group developed a prototype to cut or separate thin-film PV semi-fabricates into custom shapes and sizes. They used OMO electrodes measuring 30 cm × 30 cm, based on aluminum-doped zinc oxide (AZO), and applied them onto semi-finished 30 cm × 30 cm copper, indium, gallium and selenide (CIGS) circuits. The pre-lamination modules have an efficiency of up to 19%.

“The modules were structured with P1 and P2 lines and had a reduced AZO front contact thickness of only 200 nm,” the group explained. “The front contact was not removed completely in order to keep the optimized and stable absorber/buffer/front contact interfaces and to avoid degradation of the samples during transport.”

The proposed manufacturing process, after the deposition of the OMO electrode, also requires P3 structuring, edge deletion, and a lamination technique developed by German CIGS specialist Avancis. For the backend interconnection process, the scientists used amorphous silicon thin-film solar cells and transparent conductive oxide (TCO) coated glass, supplied by Japanese manufacturer Asahi Glass.

“An amorphous p-i-n silicon layer stack (a-Si:H) with a total thickness of about 300 nm was deposited by Plasma Enhanced Chemical Vapour Deposition (PECVD) on top of the front contact TCO,” the group said.

The researchers said they were able to produce colored modules in red, green and blue with 1% absolute less efficiency than a reference module.

“Further optimization of these processes to increase the efficiency of the prepared modules may be necessary for commercial adaption, however, technical feasibility has been demonstrated,” they said. “The largest loss is found for the open-circuit voltage. Here the cell stripes show on average a loss of 21 mV compared with the reference cells. The origin of this loss is not clear yet.”

They explained their project in “Flexible design of building integrated thin-film photovoltaics,” which was recently published in Progress in Photovoltaics.

Author: Emiliano Bellini

Perovskite microcells for solar windows

Photograph of a mosaic-patterned colored solar window with four different colors. Image: Seoul National University, nature communications, Creative Commons License CC BY 4.0

Developed by Korean scientists through a novel lift-off-based patterning approach based on swelling-induced crack propagation, the perovskite PV device achieved an open-circuit voltage of 1.16 V, a short-circuit current density of 22.5 mA/cm2, and a fill factor of 77%. With the microcells, the researchers also built a first prototype of a solar window which they claim has vivid colors and high color purity.

From pv magazine

Researchers in South Korea have developed perovskite microcells with a power conversion efficiency of 20.1% that can be used in colored solar windows.

The devices were built with a novel lift-off-based patterning approach based on swelling-induced crack propagation.

“The swelling-induced lift-off method allows the fabrication of a flat, uniform, crystalline, and patterned perovskite film without defects such as fracture or partial delamination,” the scientists explained. “In addition, the simultaneous lift-off patterning of the perovskite layer and electron transport layer (ETL) minimizes interfacial defects.”

In the process, the perovskite film was deposited by spin-coating on layers made of poly(methyl methacrylate) (PMMA) and polyimide (PI) that were prepatterned via oxygen plasma etching. A top silicon oxide (SiO2) layer is utilized as an etch stop layer for the dry etching of PMMA/PI layers and is finally wet-etched using a buffered oxide etchant (BOE).

After cracks propagate along the edge, the PI/perovskite layers are detached from the substrate without any fractures or partial delamination of the patterned films on the substrate.

“During the prepatterning of the PMMA/PI layers, the substrate becomes hydrophilic owing to oxygen plasma. Thus, the perovskite precursor can be spread over the entire substrate,” the scientists said, noting that this step allows the deposition of a perovskite film with a uniform thickness, a flat surface, and conformal coverage.

Schematic exploded view of the colored solar window with the metal–insulator–metal (MIM) resonant structure. Image: Seoul National University, nature communications, Creative Commons License CC BY 4.0

The micro cell was built with an insulation layer deposited on the ETL to prevent a direct contact between the ETL and the hole transport layer (HTL (violet). The insulation layer was then patterned and etched to expose the ETL inside the microcell area. The perovskite layer was deposited and patterned after the deposition of the HTL and top electrode.

The scientists tested 458 perovskite microcells with a diameter of 100 μm and an electrode area of 9 mm2 and found that the champion device, under standard illumination conditions, the cell achieved an efficiency of 20.1%, an open-circuit voltage of 1.16 V, a short-circuit current density of 22.5 mA/cm2, and a fill factor of 77%. The microcells also showed a light utilization efficiency of 4.67 and a color rendering index of 97.5 %.

With this PV device, the researchers also built a first prototype of a solar window which they claim has vivid colors and high color purity. The window was fabricated with metal–insulator–metal structures and moth-eye-inspired nanostructures.

The microcell design is introduced in the paper Perovskite microcells fabricated using swelling-induced crack propagation for colored solar windows, which was recently published in nature communications. The research team includes academics from the Seoul National University, the Institute for Basic Science (IBS), and the Gwangju Institute of Science and Technology.

Author: Emiliano Bellini

Solar greenhouse trials perform better than expected, proving commerciality company says

Murdoch’s world-first solar glasshouse uses ClearVue’s glass. Image: Daniel Carson |

The results from solar glass company ClearVue’s greenhouse trials at Murdoch University have found the company’s product performed better than predicted overall, demonstrating both strong power generation and thermal value.

From pv magazine Australia

Western Australian solar window company ClearVue said the results from its Murdoch University greenhouse trials, running for a year now, are strong and demonstrate the readiness of the company’s product for commercial applications.

With higher than expected power generation and thermal value – effectively insulation quality – the trials which were set up to prove the viability of solar windows have done just that.

Well timed, the company is actually already installing its solar window glaze technology at a commercial greenhouse in Japan via its licensed distributor, Tomita Technologies.

Tge Aqua Ignis Hot Springs tourism resort greenhouse is currently under construction in Sendai City, Japan. Image: ClearVue

The greenhouse at the Aqua Ignis Hot Springs tourism resort in Sendai City, Japan will be used to supply produce for the resort. Completion of the solar glazing there is expected over the coming weeks, ClearVue said, with overall completion of the greenhouse and its opening anticipated within the next months.

Murdoch greenhouse trials

Back to the Murdoch trials in Western Australia, the company has said Stage 1 is now complete with Stage 2 already getting underway. To that end, ClearVue said it has made “significant upgrades” to the greenhouse systems as part of the second phase and the aim now is to find the “optimum balance” between power generation, thermal efficiency, water savings and maximizing plant growth across a wide range of species through the adjustment to photosynthetically active radiation light.

The Murdoch greenhouse comprises of three ClearVue glazed rooms and one control room which acts as a baseline from which to measure the performance of the ClearVue product. Of the three ClearVue rooms, one uses the current commercially available ClearVue glazing product while the third and fourth rooms are variants of that product using different amounts of nano- and microparticles to look at optimization of power generation and impact on plant growth dynamics.

According to the findings, the ClearVue product generated 5.3 MWh of solar energy over the year from April 19, 2021 to now

The solar windows also displayed strong insulative or thermal value, proving to be around 2˚C warmer overnight and slower to heat up in the morning. This has a double benefit by minimizing electricity usage in the greenhouse, making it more efficient – a feature ClearVue has previously pointed out will be advantageous in the high rise building market it is targeting.

“The results from the ClearVue Greenhouse at Murdoch have demonstrated the power performance of the ClearVue’s PV glazing both as a power source for the project but also as a significant contributor to energy reduction within the operation of commercial greenhousing where growers are willing to invest into a long-term capital asset that can pay itself back – both financially and from a carbon perspective – something no other greenhouse covering product on the market can offer today,” ClearVue’s Executive Chairman Victor Rosenberg said.

“The recent upgrades made to the greenhouse will offer an even greater insight into the role the ClearVue glazing can play in commercial greenhousing,” he added.

“Whilst the results show that we still have a little work to do in finding the optimum balance between power generation, minimal water use, and optimized light conditions for maximum plant growth – we are confident that we are close to finding this equilibrium point and are looking forward to working with the Murdoch team on the Stage 2 plant science trials but also with Tomita on the commercial greenhouse at Sendai in Japan to round out this work.”

ClearVue’s Executive Chairman, Victor Rosenberg at the opening of the Murdoch University’s world-first solar greenhouse in April 2021. Image: Daniel Carson |

“The Tomita Technologies greenhouse installation is itself progressing very well and will in addition to offering a commercial greenhouse as a reference point it will also serve as a good demonstration of larger sized ClearVue PV glazing performing in a cold-climate real-world setting. We very much look forward to the finalization of this exemplar project and its opening in the coming months.”

Author: Bella Peacock

The best BIPV envelope design alternatives

Source: RMIT University

From pv magazine

Scientists in Australia have developed an optimization framework for building-integrated photovoltaics that allows the selection of design variables according to user preferences. Their model considers PV-related features such as tilt angle, window-to-wall ratio (WWR), PV placement, and PV product type, as well as objective functions and constraints such as the net present value and the payback period.

Researchers at the RMIT University in Australia have developed a multi-objective optimization (MOO) framework to maximize the life cycle energy (LCE) and life cycle cost (LCC) of different building-integrated photovoltaic (BIPV) products and applications that is claimed to offer the best BIPV envelope design alternatives at the conceptual stage.

“In recent years, the building sector across the world has shown increasing interest in placing PV on building façades and roofs by either closely integrating PV panels with conventional building materials or replacing them,” researcher Rebecca Yang told pv magazine. “The interests are driven by electrification and decarbonization of the built environment, growing demand for self-consumption, and the need for architecturally ‘good’ integration of PV, as well as technological innovations in PV materials and systems leading to better design options and feasibilities in the adoption.”

According to her, the enthusiasm of the downstream value chain stimulates upstream advances and opens dialogues between the solar industry and building professionals. Leading PV manufacturers have started to collaborate with major building entities aiming for mass production and customization for massive application potentials on building facades, roofs and shading devices of new developments as well as renovations. “In Australia, I observed that many large property developers, leading design and engineering firms and local councils are very interested to apply BIPV, but the market is still not open yet due to some issues which are common in other similar countries,” she also explained.

In the paper A multi-objective optimization framework for building-integrated PV envelope design balancing energy and cost, recently published in the Journal of Cleaner Production, Yang and her colleagues explained that the design variables for a BIPV envelope optimization model are related to either the building envelope or the operational setting of the building. “A set of envelope design features, as well as PV-related features such as tilt angle, window-to-wall ratio (WWR), PV placement and PV product type, are included as design variables in the framework,” they pointed out, noting that the proposed module includes objective functions and constraints such as the net present value and the payback period. “The selected design variable set for each optimization scenario may vary according to the selected BIPV application type or inputted user preferences.”

After applying the model to several business cases, the scientists concluded that there is no best alternative design or, better, that the ideal design can only be found when all user preferences are considered. “The study provides BIPV designers and building professionals with a method to produce and compare different BIPV designs based on their preferred application types, design preferences and criteria,” they stated.

Author: Emiliano Bellini