Light Management Technologies for Agrivoltaics

Scheme: Even solar-sharing AV solution, the solution enables ~8 times radiation spreading towards shadow cast region of photovoltaics as shown in the ray trace.

The concept of Agrivoltaics (AV) is now getting global appreciation given the fact that it can increase land-use efficiency, as it highlights the concept of dual-use for the same land area, i.e., for both agriculture activities and PV installation. Hence, by adopting AV on their farm, the farmers are benefitted from dual income by generating both food and energy, thereby meeting the Government of India (GoI) mission for Doubling Farmers' Income. Realising the importance of optics interventions required for solar light energy management in the Agrivoltaics sector, CSIR-NIIST has developed innovative even light-sharing AV solutions. The developed solution is currently at TRL 4 and can provide AV solutions even to shade-intolerant plants, a major subset of commercial crops. Further, the tunable ray spreading and spectral conversion makes our AV system compatible for variable crop height, PPFD requirements, and increased electricity generation by increasing the PV coverage area when compared with state-of-the-art agrivoltaics systems.

Traditional solar concentrators rely on mirrors and lenses, resulting in bulky systems that occupy significant space and require complex tracking mechanisms. These systems are not only costly to install due to their size and structural complexity but also necessitate a two-axis tracking system, further escalating costs. In contrast, low-concentration (less than 10X) planar light concentrators (PLCs) offer a more streamlined solution. Their non-bulky design coupled with non-imaging optics technology enables them to concentrate light without a focal point, which significantly simplifies the structure. Additionally, low-concentration optics avoid the need for complex thermal management systems required by their high-concentration counterparts, leading to further cost reductions. However, the PLCs currently on the market typically rely on multi-element micro-lenses or mirrors and require intricate tracking systems. To address this, CSIR-NIIST has pioneered a less complex, low-concentration (less than 10X) PLC. This novel, patented design integrates single-element optics with no focal length and requires only periodic adjustments for seasonal changes. This innovation has reached the prototype stage (TRL4) and promises ease of manufacturing through methods like injection molding for plastic optics modules. The compact design of these PLCs makes them extremely versatile, well-suited for integration into building-integrated photovoltaics (BIPV) or for scaling up to large utility farms.

Chromogenic glass and smart windows research

Due to the rapid increase of glass usage in various sectors, switchable chromogenic glasses are crucial for achieving multiple UN sustainable development goals like SDG- 11. Dynamic glazing using the electro-, photo- and thermochromic systems offer tunable optical properties for the building and automotive sectors to control their light and heat throughput. These optical changes could directly correlate to aesthetics, privacy control, or more importantly, reducing energy consumption in maintaining a comfortable indoor temperature. The global value of the electrochromic materials market is expected to reach almost 2 billion $ by 2025, from growing at a CAGR of 7% since 2020. Additionally, chromogenic glass-based displays are the most potent for papers-like electronic boards, offering better visibility in the ambient lighting condition without associated energy penalties. These displays can utilize both active and passive matrix addressing (AMAD, PMAD) that offers considerable engineering flexibility and compatibility with wearable devices.

Dynamic Power Window Technology

Integrating energy generation in transparency-switching windows presents a challenge due to the lack of stable materials with both switchable transparency and energy generation capabilities, which remains an R&D barrier. To address this issue, CSIR-NIIST developed and demonstrated the Dynamic Power Window (DPW) technology (TRL 4), a groundbreaking innovation that allows for switchable transparency modes and energy generation in all modes - a first-of-its-kind technology. DPW achieves these capabilities by altering the refractive index of the window layers, enabling the lateral redirection of both diffuse and direct sunlight, where a PV cell is optically coupled for energy generation. Consequently, the developed DPW offers significant cost reduction and energy generation potential compared to other dynamic window glasses, making it appealing to a broad audience

Thermoelectric materials and devices

The reversible conversion of heat energy into electrical energy can be exploited for power generation and solid-state refrigeration. There is a global demand for taping various low-grade heat sources to produce electricity for functional usage. However, conventional TE materials use heavy elements; therefore, the TE power generators (TEGs) are generally quite hefty for portability and point-of-care applications. The societal ecosystem is increasingly dependent on wearable devices, sensors, and the internet of things (IoT) devices for environmental and human health monitoring. These devices mostly rely on batteries that are unsuitable for continuous operations and have a high carbon footprint. The lightweight and robust TEGs are projected to circumvent these issues by enabling self-powered electronic devices, achieving energy autonomy for portable and flexible power generators. Our expertise lies in developing devices & modules from novel organic, organic-inorganic hybrid materials, materials characterization, and detailed study of their transport properties.

Supercapacitors

The design and development of nanostructured electrode materials are pivotal in enhancing the performance of Electric Double-Layer Capacitors (EDLC) and pseudocapacitors. Materials like graphene and carbon nanotubes are meticulously engineered to possess a high surface area, facilitating rapid ion adsorption and desorption crucial for EDLCs. These nanostructures are fabricated using techniques such as chemical vapor deposition and templating methods to ensure precise control over morphology and porosity. Pseudocapacitors, utilizing materials like transition metal oxides and conducting polymers, are also designed at the nanoscale to exhibit high redox activity through controlled chemical synthesis. Furthermore, in the realm of supercapacitors, both symmetric and asymmetric configurations are fabricated. Symmetric supercapacitors use identical electrodes, offering balanced performance in terms of energy and power densities. In contrast, asymmetric supercapacitors combine different electrode materials to optimize specific characteristics, such as increased voltage range or energy density. The fabrication of these supercapacitor configurations involves integrating nanostructured electrode materials with tailored properties, pushing the boundaries of energy storage technology towards more efficient and versatile solutions.

Cathode materials for Li-ion Batteries

Cathode materials are critical components of Li-ion batteries, with notable examples including Lithium Iron Phosphate (LFP), Nickel Manganese Cobalt Oxide (NMC), and Lithium Manganese Nickel Oxide (LMNO). LFP, renowned for its safety and stability, is synthesized using methods such as solid-state reactions or sol-gel processes, resulting in nanoparticles with enhanced lithium-ion diffusion properties. NMC, favored for its balance of energy density and longevity, undergoes controlled precipitation or co-precipitation to form nanostructures that optimize capacity and voltage stability. LMNO, with its high energy density, is synthesized through hydrothermal or solid-state reactions, producing nano-sized particles that improve specific capacity and rate performance. These cathode materials are crucial for the efficiency and performance of Li-ion batteries, powering a range of devices from smartphones to electric vehicles. Scientists at NIIST (National Institute for Interdisciplinary Science and Technology) are working diligently to enhance the synthesis methods and performance of NMC, and LMNO cathode materials for the next generation of Li-ion batteries.

Electrocatalytic Water Splitting

Electrocatalytic water splitting to generate hydrogen and oxygen has gained immense attention as it can meet the constantly increasing energy demands of humanity as well as it is an eco-friendly energy generation mechanism. Ideally, the electrolysis of water involving two half-cell reactions – hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) requires a theoretical input energy of ∆E ° = 1.23 V vs normal hydrogen electrode (NHE). But the sluggish kinetics of the two-electron HER mechanism and the four-electron OER mechanism together requires an additional amount of energy to initiate the water splitting process. Recently, research is progressing towards designing and synthesizing efficient electrocatalyst materials which can reduce the overpotential (difference between theoretical and required potential) required for water electrolysis. At CSIR-NIIST, a team is currently focussing on the development of 2D Transition Metal Dichalcogenides for Electrocatalytic Water Splitting.

Green Ammonia and Urea synthesis

Worldwide production of ammonia requires fossil fuels and is associated with significant greenhouse gas emissions. The replacement of fossil fuel based ammonia by green or carbon-free ammonia is a priority for academia, industry and governments. Ammonia is a key component of fertilizer, but it is also increasingly popular as a carbon-free fuel for the maritime sector and as a hydrogen vector. However, conventional ammonia production by Haber–Bosch process which operates under very harsh reaction conditions and high energy-intensive (consume 1-2% of total energy worldwide) with heavy CO2 emissions (releases ~420 Mt of CO2 annually). In this contest, electrochemical ammonia synthesis under ambient conditions gathered great attention because of its advantages such as eco-friendly in nature (Zero emission of CO2), less energy intake, ambient operation conditions and cost effective over conventional Haber–Bosch process. At CSIR-NIIST, we focus to develop suitable electro-catalysts for Green ammonia and Green urea synthesis.

Light Emitting Diodes

Organic and hybrid LEDs are the major contenders for display and lighting applications. Although these could make some forays into the consumer electronics sector, a sustained and deeper market penetration is hindered due the high cost. Commercially available phosphorescent OLEDs, in general, have a complicated multilayer structure incorporating expensive rare-earth based emitters. Thus, the process complexity and the cost of emitter molecules together contribute to the high cost of these products. At CSIR-NIIST, we work on novel device designs and light outcoupling techniques to reduce the device complexity and to improve the efficiency of organic and hybrid light emitting diodes. We are particularly focusing on exciplex-based OLEDs, copper halide-based LEDs and quantum dot LEDs. Another recent focus is NIR emitting devices which can be used for therapeutic applications.

Organic Field-effect Transistors

Organic FETs form a major part of printed electronics market and their projected applications in the healthcare sector make them very attractive candidates. Enhancing the charge carrier mobility used to be the prime focus in the initial years, but now a myriad of applications have been envisaged with these devices. At CSIR-NIIST, we study the structure property relationship of the semiconductor thin films, the various properties of the gate dielectrics and their impact on the device performance. On the application area, we are interested in nonvolatile memory, diagnostic devices and gas sensors using organic field-effect transistor.

Photodetectors

Photodetectors find many applications in optical communication, biomedical imaging, night vision, motion detection etc. In fact, there is an urgent need to develop UV and IR detectors while visible light detection is commonly available. We have developed device structures with high responsivity and detectivity for UV detection. Also, we have successfully demonstrated self-powered UV detectors. Both organic and inorganic devices are being studied.