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Category: solar power – Page 55

Now, researchers at the Karlsruhe Institute of Technology (KIT) have developed a prototype for fully scalable all–perovskite tandem solar modules. They were able to scale up individual perovskite cells with a power conversion efficiency of up to 23.5% at an aperture area of 0.1 square centimeters to all-perovskite tandem solar modules with an efficiency of up to 19.1% with an aperture area of 12.25 square centimeters.

The aperture area is the usable part of the surface that is not covered by electrodes, frames, or fasteners. At approximately five percent, the loss of efficiency when upscaling is relatively low. “This is the first report of an all-perovskite tandem solar module worldwide,” says Dr. Bahram Abdollahi Nejand, lead author of the publication and team leader for all-perovskite tandem solar modules.

The KIT researchers claimed this remarkable result is the first of its kind reported worldwide. To obtain this, the team increased the efficiency by optimizing the light path and reducing reflections in the solar cell architecture. They implemented an efficient layout for tandem solar modules using high-throughput laser scribing that enables the production of functional tandem solar mini-modules with two-terminal interconnected cell strips. Lastly, they used coating processes (blade coating and vacuum deposition) that are already established in industrial practice.

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Last week New York City was host to the Indoor AgTech Innovation Summit, an event which drew 600 attendees, featured 90 speakers and included representatives from 42 countries. For a sector with some history of hyperbole about its role in feeding the world, the presentations and discussions during this event featured an overall balance of optimism and pragmatism. Many different kinds of “indoor” facilities were being considered at this meeting ranging from basic greenhouses all the way to multi-level “vertical farms” of the type pictured above. Industry players prefer to call their sector “controlled environment agriculture” or CEA. That is in contrast to mainstream agriculture which has the advantage of free solar energy and rainfall, but which must also deal with all the variables associated with weather and the limitations determined by geography.

The origins of CEA stretch at least as far the 17th and 18th century when “orangeries” in France were used in the winter to protect citrus trees grown in pots. For the last eight decades the Dutch have been technology leaders in the increasingly sophisticated and international greenhouse industry. In recent years CEA has been expanding world wide and trending towards a higher degree of control of the growing conditions including light, temperature, humidity, water, and carbon dioxide concentration. Fertilization in these systems is increasingly micromanaged in a soil-free setting such as “hydroponics” or “aeroponics.” Many tasks and process controls are automated.

This is an expanding industry with 7–8% annual growth projected for greenhouses and 15% per year for vertical farming. Greenhouses are commonly used to produce leafy greens, tomatoes, peppers, and cucumbers. The highest tech, vertical farming systems are currently focused on leafy greens and herbs. Even so, the packaged salad and leafy greens market is said to be in the range of $8.7 billion and projected to grow to between $13 billion and $25 billion within the next 5 years and CEA is likely to account for an increasing share.

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Scientists in Germany looked to eliminate the use of toxic solvents in the production of perovskite solar cells, replacing them with a more environmentally material called dimethyl sulfoxide (DMSO) which has so far proved difficult to integrate into processes suitable for large-scale production. The group demonstrated a scalable blade coating process using DMSO as the only solvent, and reached cell efficiencies close to those achieved using more toxic substances.

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Lightweight and flexible perovskites are highly promising materials for the fabrication of photovoltaics. So far, however, their highest reported efficiencies have been around 20%, which is considerably lower than those of rigid perovskites (25.7%).

Researchers at Nanjing University, Jilin University, Shanghai Tech University, and East China Normal University have recently introduced a new strategy to develop more based on flexible perovskites. This strategy, introduced in a paper published in Nature Energy, entails the use of two hole-selective molecules based on carbazole cores and phosphonic acid anchoring groups to bridge the perovskite with a low temperature-processed NiO nanocrystal film.

“We believe that lightweight flexible perovskite are promising for building integrated photovoltaics, wearable electronics, portable energy systems and aerospace applications,” Hairen Tan, one of the researchers who carried out the study, told TechXplore. “However, their highest certified efficiency of 19.9% lags behind their rigid counterparts (highest 25.7%), mainly due to defective interfaces at charge-selective contacts with perovskites atop.”

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