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Solar Thermal Collectors
Published in D. Yogi Goswami, Principles of Solar Engineering, 2023
For a flat plate CR ≅ 1, and for concentrators, CR > 1. As a result, the loss term (second term) in Equation 3.68 is smaller for a concentrator and the efficiency is higher. This analysis is necessarily simplified and does not reflect the reduction in optical efficiency that frequently, but not always, occurs because of the use of imperfect mirrors or lenses in concentrators. The evaluation of Uc in Equation 3.68 in closed form is quite difficult for high-temperature concentrators, because radiation heat loss is usually quite important and introduces nonlinearities (∝T4). One disadvantage of concentrators is that they can collect only a small fraction of the diffuse energy incident at their aperture. This property is an important criterion in defining the geographic limits to the successful use of concentrators.
Other solar thermal applications
Published in John Twidell, Renewable Energy Resources, 2021
A concentrator comprises a collector that directs beam radiation onto a receiver, where the radiation is absorbed and converted to some other energy form. So in this text: Concentrator=collectorsubscriptc+receiversubscriptr
Substation Integration and Automation
Published in John D. McDonald, Electric Power Substations Engineering, 2017
The data concentrator aggregates information and provides a subset of that information to another device or devices. It is similar in function to the RTU and often can be the same device. The main difference in the terms is that a data concentrator does not necessarily have physical interfaces to monitor contact statuses and analog values. The data concentrator uses communication protocols to acquire data from other devices rather than through a direct connection.
Concentrating and black hole like structures by elastic metamaterials with acoustic cavities under active feedback control
Published in Waves in Random and Complex Media, 2022
Li Ning, Yi-Ze Wang, Yue-Sheng Wang
It is important to consider the effective frequency range of the concentrator. The metamaterials consisting of the periodic active cavities are expected to operate over a wide frequency range from 3000 to 4500 Hz. Figure 12(a,b) show the pressure fields at 3500 and 4500 Hz, which are almost undisturbed. On the other hand, the pressure field in Figure 12(c) appears obvious scattering at 5500 Hz. The efficiency of the cloak is restricted at the high frequencies. Beyond the effective frequency range, the number of the layers for the concentrator also has a significant influence on the performance of the cloak. The pressure fields of the concentrator with 20 and 40 layers are shown in Figure 13(a,b) at 5500 Hz, respectively. The result is obviously improved because the better parameter distribution can be obtained by the layer number increasing.
Thermal performance of the steam boiler based on Scheffler solar concentrator for domestic application: Experimental investigation
Published in Australian Journal of Mechanical Engineering, 2021
Vikrant Kamboj, Himanshu Agrawal, Anish Malan, Avadhesh Yadav
Solar energy is one of the substantial, reliable renewable power resources which can perform an essential role in matching the increasing energy demand and protect the depleting fossil fuel resources. Solar concentrators are mainly used to concentrate solar energy for high and medium temperature for thermal applications or power generation. Based on the type of focus, solar concentrators can be classified as line-focus concentrators like a parabolic trough, linear Fresnel lens or point-focus concentrators like the solar dish, Scheffler solar concentrator. A Scheffler solar concentrator is a lateral section of the paraboloid which includes reflecting surface, a receiver, manual tracking system, thermal energy utilisation system and the working fluid which transfer the heat. The entire radiations incident on the reflecting surface is reflected towards the focus. The working fluid in the receiver placed at the focus of the reflecting surface receives concentrated solar energy.
Development of a novel two-stage parabolic dish collector-receiver system for efficiency improvement
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2021
Santosh B. Bopche, Rohit Kumar, Inderjeet Singh
In addition to this, the dish concentrator system is advantageous on account of better geometric concentration ratio, higher operating temperature, and negligible cosine losses. It also involves slope error, tracking error, and facet alignment error. These errors cause deviation of the solar rays from the theoretical optics of a paraboloid. It causes the spreading of the optical image of the sun at the focus. The enlarged size of focus needs a bigger-sized receiver causing a huge amount of heat losses. The secondary staged concentrators are generally recommended in case if the optical aberrations of the primary concentrators are outsized enough (Reddy and Kumar 2009). Bader et al. (2009) corrected an optical deviation with the help of a secondary specular reflector, in tandem with primary pneumatic polymer mirrors supported by a pre-shaped concrete frame. Additionally, the receivers are subjected to an enormous amount of concentrated energy, which raises their operating temperatures. The losses shoot up proportionately with temperature. In the case of a conventional single-stage dish concentrator cum receiver system, losses could be higher due to intensive heat fluxes as compared to a multistage dish-receiver system. Wherein, the heat flux can be distributed in multiple stages with reduced operating temperatures that are disclosed in the present paper. The possibility of rising losses (optical as well as thermal) would be only due to an increase in the surface area of the receiver-concentrator system. In this regard, contributions examining the performances of multistage concentrators have been reviewed and discussed herewith.