Combined selective emitter and filter for high performance incandescent lighting

The efficiency of incandescent light bulbs (ILBs) is inherently low due to the dominant emission at infrared wavelengths, diminishing its popularity today. ILBs with cold-side filters that transmit visible light but reflect infrared radiation back to the filament can surpass the efficiency of state-of-the-art light-emitting diodes (LEDs). However, practical challenges such as imperfect geometrical alignment (view factor) between the filament and cold-side filters can limit the maximum achievable efficiency and make the use of cold-side filters ineffective. In this work, we show that by combining a cold-side optical filter with a selective emitter, the effect of the imperfect view factor between the filament and filter on the system efficiency can be minimized. We experimentally and theoretically demonstrate energy savings of up to 67% compared to a bare tungsten emitter at 2000 K, representing a 34% improvement over a bare tungsten filament with a filter. Our work suggests that this approach can be competitive with LEDs in both luminous efficiency and color rendering index (CRI) when using selective emitters and filters already demonstrated in the literature, thus paving the way for next-generation high-efficiency ILBs

Combined selective emitter and filter for high performance incandescent lighting

The efficiency of incandescent light bulbs (ILBs) is inherently low due to the dominant emission at infrared wavelengths, diminishing its popularity today. ILBs with cold-side filters that transmit visible light but reflect infrared radiation back to the filament can surpass the efficiency of state-of-the-art light-emitting diodes (LEDs). However, practical challenges such as imperfect geometrical alignment (view factor) between the filament and cold-side filters can limit the maximum achievable efficiency and make the use of cold-side filters ineffective. In this work, we show that by combining a cold-side optical filter with a selective emitter, the effect of the imperfect view factor between the filament and filter on the system efficiency can be minimized. We experimentally and theoretically demonstrate energy savings of up to 67% compared to a bare tungsten emitter at 2000 K, representing a 34% improvement over a bare tungsten filament with a filter. Our work suggests that this approach can be competitive with LEDs in both luminous efficiency and color rendering index (CRI) when using selective emitters and filters already demonstrated in the literature, thus paving the way for next-generation high-efficiency ILBs

High performance incandescent light bulb using a selective emitter and nanophotonic filters

Previous approaches for improving the efficiency of incandescent light bulbs (ILBs) have relied on tailoring the emitted spectrum using cold-side interference filters that reflect the infrared energy back to the emitter while transmitting the visible light. While this approach has, in theory, potential to surpass light-emitting diodes (LEDs) in terms of luminous efficiency while conserving the excellent color rendering index (CRI) inherent to ILBs, challenges such as low view factor between the emitter and filter, high emitter (>2800 K) and filter temperatures and emitter evaporation have significantly limited the maximum efficiency. In this work, we first analyze the effect of non-idealities in the cold-side filter, the emitter and the view factor on the luminous efficiency. Second, we theoretically and experimentally demonstrate that the loss in efficiency associated with low view factors can be minimized by using a selective emitter (e.g., high emissivity in the visible and low emissivity in the infrared) with a filter. Finally, we discuss the challenges in achieving a high performance and long-lasting incandescent light source including the emitter and filter thermal stability as well as emitter evaporation

Anticancer potential of Himalayan plants

Plants used in traditional medicine have stood up to the test of time and contributed many novel compounds for preventive and curative medicine to modern science. India is sitting on a gold mine of well recorded and traditionally well practiced knowledge of herbal medicine. Specially, plants growing at high altitude in Himalayan pastures are time-honored sources of health and general well being of local inhabitants. As of today, Himalayan plants are a major contributor to the herbal pharmaceutical industry both of India and other countries. Plants growing at higher altitudes are subjected to an assault of diverse testing situations including higher doses of mutagenic UV-radiation, physiological drought, desiccation and strong winds. Plants interact with stressful environments by physiological adaptation and altering the biochemical profile of plant tissues and producing a spectrum of secondary metabolites. Secondary metabolites are of special interest to scientists because of their unique pharmacophores and medicinal properties. Secondary metabolites like polyphenols, terpenes and alkaloids have been reported to possess antimutagenic and anticancer properties in many studies. The fundamental aspiration of the current review is to divulge the antimutagenic/ anticancer potential of five alpine plants used as food or medicine by the populations living at high altitudes

Modeling silica aerogel optical performance by determining its radiative properties

Silica aerogel has been known as a promising candidate for high performance transparent insulation material (TIM). Optical transparency is a crucial metric for silica aerogels in many solar related applications. Both scattering and absorption can reduce the amount of light transmitted through an aerogel slab. Due to multiple scattering, the transmittance deviates from the Beer-Lambert law (exponential attenuation). To better understand its optical performance, we decoupled and quantified the extinction contributions of absorption and scattering separately by identifying two sets of radiative properties. The radiative properties are deduced from the measured total transmittance and reflectance spectra (from 250 nm to 2500 nm) of synthesized aerogel samples by solving the inverse problem of the 1-D Radiative Transfer Equation (RTE). The obtained radiative properties are found to be independent of the sample geometry and can be considered intrinsic material properties, which originate from the aerogel’s microstructure. This finding allows for these properties to be directly compared between different samples. We also demonstrate that by using the obtained radiative properties, we can model the photon transport in aerogels of arbitrary shapes, where an analytical solution is difficult to obtain

Effect of Al2O3 ALD coating on thermal stability of silica aerogel

Abstract An optically transparent and thermally insulating (OTTI) silica aerogel demonstrates promising results for various solar thermal applications, particularly concentrated solar power systems. Higher system efficiency can be achieved by integrating OTTI materials by reducing heat loss at higher receiver temperature. However, the thermal stability of OTTI aerogels has been one of the limiting factors. Here, we report that Al2O3 atomic layer deposition (ALD) enhances the thermal stability of silica aerogel. The more layers of Al2O3 ALD coating on silica aerogels, the higher the thermal stability. However, more layers of Al2O3 ALD coating compromises transmittance of silica aerogel due to increasing the size of scattering centers. Therefore, optimization of Al2O3 ALD coating needs to be performed to enhance performance for a solar thermal system. The demonstrated ALD-coated aerogel provides a potential pathway to further improve the efficiency and reduce the cost of state-of-the-art concentrating solar power (CSP) systems