Characterization of a Nanofluid Volumetric Solar Absorber / Steam Generator

2011 ◽  
Author(s):  
Robert A. Taylor ◽  
Patrick Phelan ◽  
Ronald Adrian ◽  
Andrey Gunawan ◽  
Todd Otanicar
Keyword(s):  
Steam Generator ◽  
Thermal Energy ◽  
Bubble Dynamics ◽  
New Technologies ◽  
Pure Water ◽  
Solar Spectrum ◽  
Infrared Camera ◽  
Light Energy ◽  
Heat Transfer Analysis ◽  
Solar Thermal Energy

Solar thermal energy has shown remarkable growth in recent years — incorporating many new technologies into new applications [1]. Nanofluids — suspensions of nanoparticles in conventional fluids — have shown promise to make efficient volumetric-absorption solar collectors [2–4]. It has also been shown that concentrated light energy can efficiently cause localized phase change in a nanofluid [5]. These findings indicate that it may be advantageous to create a ‘direct, volumetric nanofluid steam generator’. That is, a solar collector design which could minimize the number of energy transfer steps, and thus minimize losses in converting sunlight (via thermal energy) to electricity. To study this, we use a testing apparatus where concentrated laser light at 532 nm — a wavelength very near the solar spectrum peak — is incident on a highly absorbing sample. The highly absorbing samples compared in this study are black dyes, black painted surfaces, and silver nanofluids — with de-ionized water as a base fluid. Each of these samples converts light energy to heat — to varying degrees — in a localized region. This region is monitored simultaneously with a digital camera and an infrared camera. The resulting observed temperature profile and bubble dynamics are compared for these fluids. For pure water with a black backing, some very high temperatures (>300 °C) are observed with a laser input of ∼75 W/cm2. Using a similar absorption potential, we observed higher temperatures in the nanofluids when compared to black dyes. A simplified boiling heat transfer analysis based on these results is also presented. We also noticed differences in bubble size and growth rates for the different samples. Overall, this study represents a proof-of-concept test for a novel volumetric, direct steam generator. These results of this test indicate that it may be possible to efficiently generate steam directly in a controlled, localized volume — i.e. without heating up passive system components.

scholarly journals Portable Solar Spectrum Reflectometer for planar and parabolic mirrors in solar thermal energy plants

Solar Energy ◽  
2016 ◽  
Vol 135 ◽  
pp. 446-454 ◽  
Author(s):  
Iñigo Salinas ◽  
Carlos Heras ◽  
Carlos Alcañiz ◽  
David Izquierdo ◽  
Noelia Martínez ◽  
...  
Keyword(s):  
Thermal Energy ◽  
Solar Spectrum ◽  
Solar Thermal ◽  
Solar Thermal Energy ◽  
Energy Plants

scholarly journals Design and development of a low-cost system to convert solar thermal energy into electricity for households in South Africa using solar concentrators

2021 ◽  
Vol 32 (4) ◽  
pp. 102-116
Author(s):  
Lukas W. Snyman ◽  
Glen Maeko
Keyword(s):  
South Africa ◽  
Energy Conversion ◽  
Thermal Energy ◽  
Low Cost ◽  
Solar Spectrum ◽  
Electrical Energy ◽  
Pulse Mode ◽  
Solar Irradiation ◽  
Solar Thermal Energy ◽  
Energy Conversion Systems

South Africa is, due its specific latitude location in the southern hemisphere, exposed to high solar irradiation levels. Black thermal absorbers have a high absorbance for solar incident radiation, while commercial photovoltaic technology only converts about 10% of energy available in the solar spectrum. In this article, low-cost Peltier conversion cells, that are normally used for cooling purposes, and that are freely available in supply stores in South Africa, were identified as suitable conversion cells for converting thermal energy into electricity. Two prototypes of thermal-to-electricity energy conversion systems were subsequently designed and developed. Particularly, advanced pulse mode DC- to- DC conversion technology, a special electronic control system, was developed, that could extract high amounts of electrical energy from the cells and could store the energy in standard storage batteries. A 3 W and a 30 W output continuous conversion capacity system were developed. A power conversion of up to 2 W capacity per individual cell was achieved. The systems used no movable parts, and the lifespan of the systems is projected to be at least twenty years. Cost and viability analyses of the systems were performed and the results were compared to existing solar photovoltaic energy conversion systems. Combining the 30 W capacity system with a black body and reflector plate absorber system revealed a cost structure of only ZAR 0.8 per kWh, as compared with a derived ZAR 3 per kWh for a combined photovoltaic and solar geyser combination, as calculated for a ten-year term. The technology as developed is suitable to be incorporated in South African households and rural Africa applications.

Heat and Mass Transfer Analysis of a Water and Solute Separation System: Using Solar Thermal Energy for Water Desalination

2015 ◽  
Author(s):  
Peiwen Li ◽  
Aditya Peri ◽  
Hongzhang Ma ◽  
Yingwen Chen
Keyword(s):  
Heat Transfer ◽  
Water Treatment ◽  
Thermal Energy ◽  
Pure Water ◽  
High Energy ◽  
Heat Transfer Process ◽  
Water Desalination ◽  
Treatment System ◽  
Solar Thermal Energy ◽  
Water Treatment System

A concept and the associated device of thermal-driven water treatment to fully separate water and solute have been proposed. The device is integrated to a conventional multi-effect-distillation water treatment system to achieve high energy efficiency and 100% water extraction using high temperature thermal energy. In the water treatment system, water for reclamation is sprayed into droplets which fall into hot, dry air and creates very effective convective heat transfer between water droplets and hot airflow. During the heat transfer process, water is vaporized for pure water collection while the crystallized solute from the reclamation water settles down to the bottom for collection. The current study investigates the energy consumption versus water treatment in the system, the correlation of the size of droplets and the temperature of hot air, and the mass heat distribution in subsystems or devices. Results from the study provide important guidance to the design of such a water treatment system.

Transient 2-D Heat Transfer Analysis of Encapsulated Phase Change Materials for Thermal Energy Storage

2012 ◽  
Author(s):  
Weihuan Zhao ◽  
Ali F. Elmozughi ◽  
Sudhakar Neti ◽  
Alparslan Oztekin
Keyword(s):  
Heat Transfer ◽  
Energy Storage ◽  
Phase Change ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Phase Change Materials ◽  
Heat Transfer Analysis ◽  
Solar Thermal Energy ◽  
Buoyancy Driven Convection ◽  
Change Material

Solar energy is receiving a lot of attention since it is a clean, renewable, and sustainable energy. A major limitation however is that it is available for only about 2,000 hours a year in many places and thus it is essential to find ways to store solar thermal energy for the off hours. The present work deals with heat transfer aspects of storing solar thermal energy in high temperature phase change materials with melting points above 300 °C. Two-dimension transient heat transfer analysis is conducted to investigate thermal energy storage using encapsulated phase change material (EPCM) for concentrated solar power (CSP) applications. Sodium nitrate, NaNO3, is considered as the phase change material (PCM) encapsulated by stainless steel in a cylindrical shaped capsule. Stream function-vorticity formulation is employed to study the effect of buoyancy-driven convection in the molten salt on the total charging and discharging times for various sizes of PCM capsulated. Simulations are also conducted for a horizontally placed rod inside a flow channel. Storage times are calculated for laminar and turbulent flows of heat transfer fluids transferring heat into EPCM. It is shown that the buoyancy-driven convection in the molten PCM enhances internal heat transfer inside the capsule and hence helps to slightly shorten the total heat transfer times during both charging and discharging processes. Flow characteristics of the heat transfer fluid have profound effect on the nature of phase change process inside the EPCM rod.

scholarly journals Ultra-Broadband Refractory All-Metal Metamaterial Selective Absorber for Solar Thermal Energy Conversion

Nanomaterials ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 1872
Author(s):  
Buxiong Qi ◽  
Wenqiong Chen ◽  
Tiaoming Niu ◽  
Zhonglei Mei
Keyword(s):  
Energy Conversion ◽  
Thermal Energy ◽  
Solar Spectrum ◽  
Solar Thermal ◽  
Solar Irradiation ◽  
Selective Absorption ◽  
Solar Thermal Energy ◽  
Photothermal Conversion ◽  
Broadband Absorption ◽  
Thermal Energy Conversion

A full-spectrum near-unity solar absorber has attracted substantial attention in recent years, and exhibited broad application prospects in solar thermal energy conversion. In this paper, an all-metal titanium (Ti) pyramid structured metamaterial absorber (MMA) is proposed to achieve broadband absorption from the near-infrared to ultraviolet, exhibiting efficient solar-selective absorption. The simulation results show that the average absorption rate in the wavelength range of 200–2620 nm reached more than 98.68%, and the solar irradiation absorption efficiency in the entire solar spectrum reached 98.27%. The photothermal conversion efficiency (PTCE) reached 95.88% in the entire solar spectrum at a temperature of 700 °C. In addition, the strong and broadband absorption of the MMA are due to the strong absorption of local surface plasmon polariton (LSPP), coupled results of multiple plasmons and the strong loss of the refractory titanium material itself. Additionally, the analysis of the results show that the MMA has wide-angle incidence and polarization insensitivity, and has a great processing accuracy tolerance. This broadband MMA paves the way for selective high-temperature photothermal conversion devices for solar energy harvesting and seawater desalination applications.

Pyrazolium Phase Change Materials for Solar-Thermal and Wind Energy Storage

2019 ◽  
Author(s):  
Karolina Matuszek ◽  
R. Vijayaraghavan ◽  
Craig Forsyth ◽  
Surianarayanan Mahadevan ◽  
Mega Kar ◽  
...  
Keyword(s):  
Energy Storage ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Phase Change Materials ◽  
High Efficiency ◽  
Scale Up ◽  
Solar Thermal ◽  
Energy Storage Materials ◽  
Solar Thermal Energy ◽  
Storage Materials

Renewable energy has the ultimate capacity to resolve the environmental and scarcity challenges of the world’s energy supplies. However, both the utility of these sources and the economics of their implementation are strongly limited by their intermittent nature; inexpensive means of energy storage therefore needs to be part of the design. Distributed thermal energy storage is surprisingly underdeveloped in this context, in part due to the lack of advanced storage materials. Here, we describe a novel family of thermal energy storage materials based on pyrazolium cation, that operate in the 100-220°C temperature range, offering safe, inexpensive capacity, opening new pathways for high efficiency collection and storage of both solar-thermal energy, as well as excess wind power. We probe the molecular origins of the high thermal energy storage capacity of these ionic materials and demonstrate extended cycling that provides a basis for further scale up and development.

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