Smart Power Windows:
Conventional glass windows used in buildings trap the heat, increases air conditioning loads and causes “Urban Heat Islanding Effect (UHI)” resulting in significant climate warming. UHI problem is further exacerbated due to the alarming rise of high-rise buildings and skyscrapers in cities. To reduce the solar heat load in a building, several passive and active solutions exist such as double pane windows, triple glazed windows, motorized blinds etc. However, none of these solutions effectively harnesses the heat energy falling on a window and they operate in such a way that there is a tradeoff between heat load and natural lighting. The smart power window is capable of harvest energy from the heat causing radiation, thus reducing the heat load of buildings and provide energy conservation.
Solar PVT co-generation System:
The current project on solar PVT comprises of solar PV module integrated with an optimized heat recovery system to produce electrical and thermal energy simultaneously. Recently, a 300 We and 600 Wth PVT system was designed and installed at CSIR shown in Figure 1. Testing of the PVT systems has shown promising results with peak outlet water temperature of (<600C) and peak electricity generation of 250We. In addition to this, an emerging area of Low Concentrating PVT system as shown in Figure 2 has also been explored where completely optimized concentrators integrated with a flux distributor have been attached to a PVT module for improving the grade of thermal energy (<800C). Further, for data collection, a dedicated data acquisition system with back-end for data collection and storing and front end for instantaneous data display as shown in Figure 3 has been developed indigenously and installed for real-time monitoring. In the future, it is proposed that a PVT system will be integrated into a desiccant based air-conditioning unit to bring down the power consumption of the air conditioner by 30-40 %.
IoT enabled Solar Tree:
Solar tree consisting of multiple solar panels have shown the feasibility to tune the solar power generation curve as per the requirement of location/application. Studies of optimization of orientations of single solar panel employing data-driven approach emphasize the need to consider surface azimuth angle. Also, latitude angle based determination of optimal orientation may not always be true. Multiple solar trees have been designed with an optimized positioning of solar panels to reduce ground footprint and shading losses. Designed solar tree have shown an increase in power generation up to 7.38% and minimizes shading losses of less than 2%. The methodology adopted can be easily extended to the design of optimized solar tree for any location and capacity. Solar tree integrated with IoT based smart sensors platform can enable smart agriculture through the implementation of precision farming, zero-emission driving through solar tree based EV charging stations, improved road security through smart pollution monitoring and remote surveillance etc. IoT enabled solar tree providing higher power generation per unit ground footprint will find application in smart cities.
The quest for the development of portable thermophotovoltaic systems has been a growing interest due to the ability to achieve high power and energy densities using hydrocarbon-based fuels. Recent studies based on intermediate filters and photonic crystals have shown significant improvement in system efficiencies for combustion and solar-based TPV systems. The key goal is to engineer directionally and spectrally selective thermal emitters ideally matched to the solar cell. We work on high contrast grating based thermal emitter using silicon as a grating material on a quartz substrate. The intrinsic properties of quartz substrate filter the below bandgap (greater than 4.5 µm) radiation in the infrared region. The silicon gratings are optimized (period = 2.4 µm, duty cycle = 40% and thickness = 0.55 µm), to provide transmission only for photons with wavelengths lower than 1.8 µm and inhibit the below bandgap radiation of the GaSb cell. The spectrally tuned emitter structure shows transmission of more than 75% of convertible photons (above the bandgap) and reflection of 80% of unconvertible photons (below bandgap) back to the combustor thus reducing the heat losses in the photovoltaic conversion, increasing the combustion system temperature thereby contributing to an overall increase in TPV system efficiency.
Solar Powered Hydrogen Generation:
Photoelectrochemical (PEC) water splitting works by combining the functions of light harvesting and electrolysis together, to directly convert solar energy into hydrogen fuel. This research focuses on development of α-ferrite (Hematite) based photoelectrode (commonly referred as rust) owing to its earth abundance, low cost, non-toxic, near-ideal bandgap (2.0 eV) for visible light harvesting, with a theoretical maximum STH efficiency of about 15 % . The research aims in performance enhancement of ferrite-based photoelectrodes by embedding plasmonic nanoparticles (NPs) on a semiconductor surface, which significantly enhances water spitting efficiency by extending the light absorption spectral range through localized surface plasmon resonance (LSPR) . This work specifically emphases in tuning the size and shape dependent plasmonic activity towards the betterment of unbiased water splitting.
Green Solar Cells:
The present work is towards the development of co-sensitized configurations of multiple natural pigments absorbing different wavelengths and the incorporation of plasmonic metal nanoparticles for the development of enhanced efficiency green solar cells. The complementary pigments and nanoparticles were chosen to efficiently harvest and absorb incident light. Density Functional Theory studies of the dye and Finite Domain Time Domain (FDTD) studies of the nanoparticles were performed to verify that properties of the chosen materials are suitable for their application. The various mechanisms of in the solar cell were studied and fabrication processes optimized for the best performance.
- The natural dyes,betanin, chlorophyll, indigo and lawsone, were explored for efficiency enhancement by co-sensitization.
- Silver nanoparticles were used for the plasmonic enhancement of the best performing dyes.
- An overall efficiency of ~1% was achieved for the Betanin-Lawsone co-sensitized solar cell incorporated with a tailored bimodal distribution of silver nanoparticles.
Design and Characterization of Organic Molecules with unique THz resonances:
Novel organic molecules with resonances at low THz frequency (< 3 THz) have been designed by employing the concept of spring-mass methodology – molecules with higher reduced mass (µ) and lower bond strength (k) using Density Functional Theory (DFT) based simulations. Tuning of the THz resonances has been achieved by electronegative atom substitution and by designing molecular complexes with multiple strong hydrogen bonds. The engineered molecules can be used as ‘THz tags’ which can be incorporated in currency notes and pharmaceutical tablets for anti-counterfeiting applications.
Terahertz Spectroscopy of Cement Hydration Dynamics :
Achieving a strong and durable concrete at a faster rate of hydration is one of the key areas of research. The dynamics of hydration due to the addition of optimum level of nanomaterials to the major constituents of cement are Tricalcium Silicate (Ca3SiO5, commonly termed as C3S), Dicalcium Silicate (Ca2SiO4, C2S) is being investigated using THz spectroscopy. DFT simulations are being employed to understand the hydration dynamics at a microscopic scale.
Understanding water dynamics in Fuel Cell Membranes using terahertz spectroscopy:
The research focuses on analyzing the water dynamics in the fuel cell membrane using THz spectroscopy. The polymer membrane in fuel cell must provide high proton conductivity and must be chemically and mechanically stable in the fuel cell environment. The hydration of the membrane plays a very important role in the performance of the fuel cells. Excess water will flood the membrane and too little will dry the membrane and in both cases, the power output will drop. Thus it is important to study the dynamics of the water distribution in PEMFC. The figure below shows the tracking of water content using THz-TDS system.
One of the main features of Terahertz waves is that they can be used to “see through” a range of dry and non-metallic items which are transparent to THz waves. THz radiation has been employed to detect objects hidden in packages and for detection of defects/cracks in concrete.
THz Imaging FRP composites:
The research majorly focuses on the non-invasive characterization and evaluation of defects in glass fiber reinforced polymer (GFRP), carbon fiber reinforced polymer (CFRP) composites and sandwich composites. These composites typically have a high strength to weight ratio making them very popular in the field of aerospace, renewable energy, naval industries, automobile industries and defense applications. The main defects in these composites are surface damages, voids, foreign body intrusion, debonding and delamination. One such defect in CFRP and GFRP-Balsawood composite imaged using the CW THz system is shown below.