Optimization of Parabolic Heliostat Focal Lengths in a Mini-Tower Solar Concentrator System

2011 ◽  
Author(s):  
Karim Hamza ◽  
Umesh Gandhi ◽  
Kazuhiro Saitou
Keyword(s):  
High Temperature ◽  
Concentration Ratio ◽  
Focal Length ◽  
Low Cost ◽  
Small Scale ◽  
Angle Of Incidence ◽  
Solar Concentrator ◽  
Effective Focal Length ◽  
Unit Energy ◽  
Utility Scale

Solar tower with heliostat mirrors is one of the established setups for utility-scale solar energy harvesting. Advantages of the setup include the capability to reach high temperature, modularity and ease of maintenance for the heliostats, containment of the high temperature zone atop the tower, as well as overall low cost per unit energy. However, downscaling to medium or small scale applications often does not turn out economically feasible with flat mirror heliostats that are the norm in utility-scale systems. This is mainly due to the need to preserve the solar concentration ratio, which in turn means the number of flat mirrors cannot be reduced. Use of parabolic mirrors instead can significantly reduce the required number of mirrors for smaller scale systems, but comes with new challenges. Unlike flat mirrors that have infinite effective focal length, the effective focal length of parabolic mirrors changes with the angle of incidence, which in turn, changes throughout the day and season. The design challenge tackled in this paper is that of optimal selection of the focal lengths of the heliostats in order to maximize the yearly harvested energy while maintaining the concentration ratio within desirable limits. A parameterized system model is developed and a genetic algorithm is implemented for the optimization task. The model is then applied to a demonstration case study of a 10 kW solar concentrator. Results of the study demonstrate the proposed design approach as well as show the promise for effective downscaling of tower and heliostat systems.

Optimal Scheduling of Parabolic Heliostats Aim Targets in a Mini-Tower Solar Concentrator System

2011 ◽  
Author(s):  
Karim Hamza ◽  
Umesh Gandhi ◽  
Kazuhiro Saitou
Keyword(s):  
High Temperature ◽  
Concentration Ratio ◽  
Flux Distribution ◽  
Incidence Angle ◽  
Focal Length ◽  
Low Cost ◽  
Small Scale ◽  
Solar Concentrator ◽  
Design Variables ◽  
Utility Scale

Solar tower with heliostat mirrors is an established technology for utility-scale solar energy harvesting. The setup has several advantages such as the capability to reach high temperature, modularity and ease of maintenance of the heliostats, containment of the high temperature zone, as well as overall low cost per harvested energy. Downscaling to medium and small scale applications is a desirable goal in order to attract more users of the technology. However, the downscaling often does not turn out economically feasible while using flat mirror heliostats, which are the norm in utility-scale systems. This is mainly due to the need to preserve the number (typically several hundred) of mirrors in order to maintain the solar concentration ratio. Use of parabolic mirrors instead can significantly reduce the required number of mirrors for smaller scale systems, but comes with new challenges. Unlike flat mirrors, the effective focal length of parabolic mirrors changes with the incidence angle causing undesirable variations in the concentration ratio and/or flux distribution at the receiver. To overcome this issue, we propose adjustment of the aim targets of the heliostat mirrors. Instead of aiming at the center of the receiver, aim targets are set as design variables and optimized to reduce undesirable peaks in the flux distribution. A special implementation of genetic algorithm is developed and applied to a case study of a nominal 10kW solar concentrator. Results of the study show significant improvement in flux distribution.

scholarly journals Monte Carlo Ray-Tracing Simulation of a Cassegrain Solar Concentrator Module for CPV

2021 ◽  
Vol 9 ◽  
Author(s):  
Seung Jin Oh ◽  
Hyungchan Kim ◽  
Youngsun Hong
Keyword(s):  
Monte Carlo ◽  
Ray Tracing ◽  
Concentration Ratio ◽  
Collection Efficiency ◽  
Focal Length ◽  
Tracking Error ◽  
Target Area ◽  
Solar Concentrator ◽  
Acceptance Angle ◽  
Energy Applications

The concentration ratio is one of the most important characteristics in designing a Cassegrain solar concentrator since it directly affects the performance of high-density solar energy applications such as concentrated photovoltaics (CPVs). In this study, solar concentrator modules that have different configurations were proposed and their performances were compared by means of a Monte Carlo ray-tracing algorithm to identify the optimal configurations. The first solar concentrator design includes a primary parabolic concentrator, a parabolic secondary reflector, and a homogenizer. The second design, on the other hand, includes a parabolic primary concentrator, a secondary hyperbolic concentrator, and a homogenizer. Two different reflectance were applied to find the ideal concentration ratio and the actual concentration ratio. In addition, uniform rays and solar rays also were compared to estimate their efficiency. Results revealed that both modules show identical concentration ratios of 610 when the tracking error is not considered. However, the concentration ratio of the first design rapidly drops when the sun tracking error overshoots even 0.1°, whereas the concentration ratio of the second design remained constant within the range of the 0.8° tracking error. It was concluded that a paraboloidal reflector is not appropriate for the second mirror in a Cassegrain concentrator due to its low acceptance angle. The maximum collection efficiency was achieved when the f-number is smaller and the rim angle is bigger and when the secondary reflector is in a hyperboloid shape. The target area has to be rather bigger with a shorter focal length for the secondary reflector to obtain a wider acceptance angle.

Experimental Exploration of a Small Scale Pneumatically Pumped Thermal Storage System

2016 ◽  
Author(s):  
Inri Rodriguez ◽  
Jesus Cerda ◽  
Daniel S. Codd
Keyword(s):  
High Temperature ◽  
Storage Tank ◽  
Pulse Width Modulation ◽  
Low Cost ◽  
Storage System ◽  
Heat Engine ◽  
Thermal Storage ◽  
Heat Transfer Fluid ◽  
Small Scale ◽  
Constant Frequency

A prototype water-glycerol two tank storage system was designed to simulate the fluidic properties of a high temperature molten salt system while allowing for room temperature testing of a low cost, small scale pneumatically pumped thermal storage system for use in concentrated solar power (CSP) applications. Pressurized air is metered into a primary heat transfer fluid (HTF) storage tank; the airflow displaces the HTF through a 3D printed prototype thermoplate receiver and into a secondary storage tank to be dispatched in order to drive a heat engine during peak demand times. A microcontroller was programmed to use pulse-width modulation (PWM) to regulate air flow via an air solenoid. At a constant frequency of 10Hz, it was found that the lowest pressure drops and the slowest flowrates across the receiver occurred at low duty cycles of 15% and 20% and low inlet air pressures of 124 and 207 kPa. However, the data also suggested the possibility of slug flow. Replacement equipment and design modifications are suggested for further analysis and high temperature experiments. Nevertheless, testing demonstrated the feasibility of pneumatic pumping for small systems.

scholarly journals Pulse Reverse Alloy Plating for Increased Lifetimes for Biocombustors

2019 ◽  
Author(s):  
Jing Xu ◽  
Tim Hall ◽  
Santosh Vijapur ◽  
DAN WANG ◽  
Jennings E. Taylor ◽  
...  
Keyword(s):  
Corrosion Resistance ◽  
High Temperature ◽  
Thermal Energy ◽  
Low Cost ◽  
Base Material ◽  
High Temperature Corrosion ◽  
Biomass Energy ◽  
Biomass Combustion ◽  
Small Scale ◽  
Low Alloy Steels

Biomass embodies tremendous potential as a renewable energy resource. According to the biomass Thermal Energy Council (BTEC), biomass energy is renewable, carbon neutral, domestic and technologically mature. In addition, the low cost per BTU of wood chips and pellets relative to fossil fuels makes biomass an attractive thermal energy source. Furthermore, ~7% of global energy consumption comprises small-scale biomass combustion, representing a tremendous market for technologies that facilitate enhanced biomass utilization. However, a major challenge associated with utilization of biomass is its combustion behavior. The moisture content, chemical composition, and combustion efficiency varies depending on the source of biomass. Small scale biomass combustors (Figure 1) which for cost reasons are often constructed of mild or low-alloy steels, during operation are subjected to corrosive environments which include alkali halides (borne, e.g., by fly ash particulates), mineral/halogen acids and water; as well as various others such as sulfur and nitrogen oxides. There is a need to create more efficient, longer lasting, cleaner, and cost effective cookstoves for use in burning biomaterials. The materials used for cookstoves must improve burning efficiency, must be able to operate at higher temperatures, and should be low cost material systems to durably perform in the corrosive environments.Within this context, Faraday Technology Inc. is working on developing low cost and high value corrosion-resistant alloy coatings for existing bio-combustors or lower cost steels with the goal of increasing their functional lifetime, while reducing the component cost. The manufacturing process involves electrodeposition of binary/ternary/quaternary alloys consisting of [Ni/Co]-Cr-[Mo/Fe] onto a low cost substrate and subsequent accelerated high temperature corrosion evaluation. A wide array of electrolytes and processing parameters were evaluated in order to understand these effects on the deposit composition, structure, and high-temperature corrosion resistance properties towards the goal of developing an ideal alloy coating. Specifically, 100 wt% Cr, 7 wt% Co- 93 wt% Cr binary and 15 wt% Ni – 20 wt% Cr – 55 wt% Co (NiCoCr) ternary alloy coatings demonstrated enhanced corrosion resistance when exposed to an aggressive environment (~700°C, 1000 hr, coating surface salted with ~1 mg/cm2 every 100 hours). When compared to the SS base material the Cr/CoCr alloy coatings exhibited effective protection to the substrate and over 10 times lifetime improvement to its base material.

Electricity Production from Small-Scale Photovoltaics in Urban Areas

2015 ◽  
pp. 124-161
Author(s):  
Constantinos S. Psomopoulos ◽  
George Ch. Ioannidis ◽  
Stavros D. Kaminaris
Keyword(s):  
Urban Areas ◽  
Low Cost ◽  
Electricity Production ◽  
Small Scale ◽  
Production Data ◽  
Solar Photovoltaic ◽  
Pv System ◽  
The World ◽  
The Cost ◽  
Utility Scale

The interest in solar photovoltaic energy is growing worldwide. Today, more than 40GW of photovoltaics have been installed all over the world. Since the 1970s, the PV system price is continuously dropping. This price drop and the adaptation of feed-in tariffs at governmental or utility scale have encouraged worldwide application of small-scale photovoltaic systems. The objective of this chapter is to present the potential for electricity production focusing mainly on the benefits of small-scale installations in urban areas, along with the growth of the global photovoltaics market. The types of installation alternatives are described but the focus is on the rooftop installations due to their simplicity and relatively low cost for urban areas. Electricity production data are presented together with their technical characteristics. Furthermore, analysis of the cost reduction is attempted and the benefits gained from the implementation of small-scale systems are also presented, demonstrating the sustainability role they will play.

scholarly journals Design and Evaluation of Polygonal Trough Solar Concentrator

2021 ◽  
Vol 34 (4) ◽  
pp. 10-16
Author(s):  
Yasser Yassin Khudair ◽  
Alaa Badr Hasan
Keyword(s):  
Concentration Ratio ◽  
Angle Of Incidence ◽  
Solar Concentrator ◽  
Acceptance Angle ◽  
Optical Efficiency ◽  
Cylindrical Mirror ◽  
Design For All ◽  
Reflecting Surfaces ◽  
Reflecting Surface ◽  
To Receive

     In this paper, a solar concentrator is designed in the form of a concave half-cylindrical mirror consisting of polygonal reflective surface plates. The plates are arranged to give a hemispherical shape to the design. These surfaces work to receive solar radiation and focusing by reflecting it to the receiver that is placed in front of the reflecting surfaces. The results are compared with a system consisting of a concave reflecting surface of the same dimensions to obtain a good criterion for evaluating the design performance. The results showed a low acceptance angle for the design for all the samples used due to the geometrical design nature. The optical efficiency affected by the angle of incidence greatly by all the samples used, which differ in the concentration ratio, width and location of the receiver.

Electrodeposited Inconel and Stellite like Coatings for Improved Corrosion Resistance in Biocombustors

2018 ◽  
Author(s):  
Tim Hall ◽  
Santosh Vijapur ◽  
Jennings E. Taylor ◽  
Jing Xu ◽  
Maria Inman
Keyword(s):  
Corrosion Resistance ◽  
High Temperature ◽  
Thermal Energy ◽  
Low Cost ◽  
Base Material ◽  
High Temperature Corrosion ◽  
Biomass Combustion ◽  
Small Scale ◽  
Low Alloy Steels ◽  
Corrosive Environments

Biomass embodies tremendous potential as a renewable energy resource. According to the biomass thermal Energy Council (BTEC), biomass energy is renewable, carbon neutral, domestic and technologically mature. In addition, the low cost per BTU of wood chips and pellets relative to fossil fuels makes biomass an attractive thermal energy source. Furthermore, ~7% of global energy consumption comprises small-scale biomass combustion, representing a tremendous market for technologies that facilitate enhanced biomass utilization. However, a major challenge associated with utilization of biomass is its combustion behavior. The moisture content, chemical composition, and combustion efficiency varies depending on the source of biomass. Small scale biomass combustors, which for cost reasons are often constructed of mild or low-alloy steels, during operation are subjected to corrosive environments that include alkali halides (borne, e.g., by fly ash particulates), mineral/halogen acids and water; as well as various others such as sulfur and nitrogen oxides. There is a need to create more efficient, longer lasting, cleaner, and cost effective cookstoves for use in burning biomaterials. The materials used for cookstoves must improve burning efficiency, must be able operate at higher temperatures, and should be low cost material systems to durably perform in the corrosive environments. Within this context, Faraday Technology is working on developing low cost and high value corrosion-resistant alloy coatings for existing bio-combustors or lower cost steels with the goal of increasing their functional lifetime, while reducing the component cost. The manufacturing process involves electrodeposition of binary/ternary/quaternary alloys consisting of [Ni/Co]-Cr-[Mo/Fe] onto a low cost substrate and subsequent accelerated high temperature corrosion evaluation. A wide array of electrolytes and processing parameters were evaluated in order to understand these effects on the deposit composition, structure, and high-temperature corrosion resistance properties towards the goal of developing an ideal alloy coating. Specifically, 60 wt% Ni – 40 wt% Cr (NiCr) binary and 25 wt% Ni – 20 wt% Cr – 55 wt% Co (NiCoCr) ternary alloy coatings demonstrated enhanced corrosion resistance when exposed to an aggressive environment (~700°C, 1000 hr, coating surface salted with ~3 mg/cm2 every 100 hours). When compared to the SS base material the NiCr and NiCoCr alloy coatings exhibited a 70% lower weight loss and 3.4 times lifetime improvement over its base material.

Low-Cost Solar Mirror Substrates and Geometries for Solar Thermal and Photovoltaic Concentrator Applications

2001 ◽  
Author(s):  
David N. Wells
Keyword(s):  
Motion Tracking ◽  
Low Cost ◽  
Float Glass ◽  
Solar Thermal ◽  
Small Scale ◽  
Solar Concentrator ◽  
Hail Damage ◽  
Low Profile ◽  
Cylindrical Reflector ◽  
Cylindrical Mirror

Abstract Two principal approaches to lowering solar concentrator costs are through improved geometry (lower profile, simpler shape), and through simplified methods to make concentrator substrates. The paper discusses issues relating to fabrication of solar concentrator mirrors from inexpensive elastically bent float glass mirrors. Protection from hail damage by a novel shock absorbing back layer is presented. New low-profile concentrator geometry is presented which utilize the low-cost mirror substrates. One new geometry uses a stationary cylindrical reflector with novel arc-motion tracking absorber that appears suitable for mid-sized thermal applications. Another uses the cylindrical mirror with an azimuth-elevation tracking mechanism appears to be suitable for small-scale applications. To get even higher concentration, some low-cost secondary designs are briefly discussed which use refractive tubes or lenses as secondary concentrating elements.

Hydrogen: The Fuel That Drill Bits Cannot Reach

2006 ◽  
Author(s):  
Alistair I. Miller ◽  
Romney B. Duffey
Keyword(s):  
High Temperature ◽  
Natural Gas ◽  
Low Cost ◽  
Cost Effective ◽  
Small Scale ◽  
Clean Coal ◽  
Steam Methane ◽  
Low Co2 ◽  
Environmental Footprints ◽  
Drill Bits

As realization grows of the damaging cumulative effects of CO2 on our biosphere, the prospect of substituting hydrogen for oil-based fuels attracts growing attention. Japan provides a leading example of remedial action with the expectation of five million fuel-cell-powered vehicles in operation by 2020. But where will the fuel for these and the rest of a “Hydrogen Age” come from? The hydrogen market used to be straightforward: small-scale or high-purity markets were supplied relatively expensively by electrolysis; the other 95% was supplied much more cheaply by reforming hydrocarbons — mostly using steam-methane reforming (SMR) and low-cost natural gas. The recent rise in the price of hydrocarbons — natural gas as well as oil — plus the need to sequester CO2 has disrupted this scenario. It seems likely that this is a permanent shift driven by growing demand for limited low-cost sources of fluid hydrocarbons. So the traditional SMR route to hydrogen will be in competition with reforming of heavier hydrocarbons (particularly coal and residual oils) as well as with electrolysis based on electricity produced from low-CO2-emitting sources. By 2025, new high-temperature thermochemical or thermoelectrolytic sources based on high-temperature nuclear reactors could be in contention. This paper assesses the economics of all these potential sources of hydrogen and their price sensitivities. It also considers their environmental footprints. Is hydrogen from “clean coal” or other lower value hydrocarbons cost-effective if it is also CO2-free? Is intermittent low-temperature electrolysis based on nuclear- and wind-produced electricity (NuWind©) the best way or does the hydrogen future belong to thermochemistry or thermoelectrolytic sources? How can one produce hydrogen to upgrade Canada’s vast oilsands resources without the detraction of a large CO2 processing penalty? Fortunately for our planet, switching to hydrogen is no more than a technical challenge with a range of possible solutions but we need to make that point clearly to the political decision-takers and be able to provide assurance that the preferred solution will not be a source of new problems.

Electricity Production from Small-Scale Photovoltaics in Urban Areas

2017 ◽  
pp. 618-656 ◽  
Author(s):  
Constantinos S. Psomopoulos ◽  
George Ch. Ioannidis ◽  
Stavros D. Kaminaris
Keyword(s):  
Urban Areas ◽  
Low Cost ◽  
Electricity Production ◽  
Small Scale ◽  
Production Data ◽  
Solar Photovoltaic ◽  
Pv System ◽  
The World ◽  
The Cost ◽  
Utility Scale

The interest in solar photovoltaic energy is growing worldwide. Today, more than 40GW of photovoltaics have been installed all over the world. Since the 1970s, the PV system price is continuously dropping. This price drop and the adaptation of feed-in tariffs at governmental or utility scale have encouraged worldwide application of small-scale photovoltaic systems. The objective of this chapter is to present the potential for electricity production focusing mainly on the benefits of small-scale installations in urban areas, along with the growth of the global photovoltaics market. The types of installation alternatives are described but the focus is on the rooftop installations due to their simplicity and relatively low cost for urban areas. Electricity production data are presented together with their technical characteristics. Furthermore, analysis of the cost reduction is attempted and the benefits gained from the implementation of small-scale systems are also presented, demonstrating the sustainability role they will play.

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