Solar Energy Utilization Systems Research Articles

A review of thermohydraulic performance of artificially roughened solar air heaters

Abstract Solar air heaters form the major component of solar energy utilization system which absorbs the incoming solar radiation, converting it into thermal energy at the absorbing surface, and transferring the energy to a fluid flowing through the collector. The efficiency of flat plate solar air heater has been found to be low because of low convective heat transfer coefficient between absorber plate and the flowing air which increases the absorber plate temperature, leading to higher heat losses to the environment resulting in low thermal efficiency of such collectors. Artificial roughness in the form of repeated ribs is the most effective and economic way of improving the thermal performance of solar air heater. This paper presents an extensive review on the research carried out on artificial roughened solar air heater ducts. The objective of this paper is to review various studies, carried out on thermal as well as hydraulic performance of artificial roughened solar air heater ducts. The review presented in this paper will be useful for the researchers working in this area.

Performance evaluations and applications of photovoltaic–thermal collectors and systems

Abstract As a kind of renewable energy, solar energy is paid more and more attention all over the world. Solar energy utilization system can be classified into two categories: thermal systems which convert solar energy to thermal energy, and photovoltaic systems which convert solar energy to electrical energy. Normally, both types of the collectors are used separately. In solar thermal system, the solar thermal energy can be used for heating working fluid via a heat collector. The conventional electrical energy is used to circulate working liquid through the collector. The use of conventional electrical energy can be avoided if combination of both types of thermal collector and photovoltaic collector is hybrid in one unit named photovoltaic–thermal collector (PV/T). In order to fully develop the applications of the photovoltaic–thermal collectors and systems, more researches on performances and characteristics of the photovoltaic–thermal collectors and systems have been carried out. This paper presents the performance evaluations and applications of the photovoltaic–thermal collectors and systems. The performances of the photovoltaic–thermal air collectors and photovoltaic–thermal water collectors are analyzed and discussed. The applications of the photovoltaic–thermal systems, such as building integrated photovoltaic–thermal systems, concentrating photovoltaic–thermal systems and photovoltaic–thermal heat pump systems are presented. Several factors affecting the performances and characteristics of the photovoltaic–thermal systems are also summarized.

인공위성을 이용한 한반도 태양에너지자원 상세 정밀분석

Since the solar energy resource is the main input for sizing any solar energy utilization system, it is essential to utilize the solar radiation data as an application and development of solar energy system increase. It will be necessary to understand and evaluate the insolation data. The Korea Institute of Energy Research(KIER) has begun collecting horizontal global insolation data since May, 1982 at 16 different locations in Korea and for the more detailed analysis, images taken by geostationary satellite may be used to estimate solar irradiance fluxes at earth`s surface. It is based on the empirical correlation between a satellite derived cloud index and the irradiance at the ground. From the results, the measured data has been collected at 16 different stations and estimated using satellite at 44 different stations over the Korean peninsula from 1982 to 2010. The Result of analysis shows that the annual-average daily global radiation on the horizontal surface is 3.66 and estimated solar radiation fluxes show reliable results for estimating the global radiation with average deviation of -7.2 to +3.7 % from the measured values.

Models for Predicting Thermal Performance of Packed Bed Energy Storage System for Solar Air Heaters - A Review

Packed bed is generally recommended for attaching with solar air heater in order to store thermal energy of hot air. For designing such a system under the given system and operating parameters, it is required to predict performance of the system by using mathematical models. In the present paper an attempt has been made to discuss mathematical models reported in the literature for predicting thermal performance of packed bed energy storage system for solar air heaters. The designer may be benefited from the consolidated information reported in the present paper. The continuous use of fossil fuels resulted energy crisis and environmental threat. It is felt that renewable energy sources are quite capable of meeting energy demand of today's world. The use of renewable energy sources for meeting energy needs can conserve the conventional energy sources for more number of decades. Among renewable energy sources solar energy is considered to be one of the most dominating energy source. It has many advantages like large potential, free of cost, available everywhere, environment friendly etc. However time dependent nature is the major disadvantage of solar energy. In order to overcome this disadvantage it is required to attach an energy storage system with the solar energy utilization system. With such a provision the stored energy can be utilized in the absence of solar radiation or under peak load conditions. In case of solar air heaters it is required to store thermal energy of flowing hot air. Packed bed is generally recommended for such an application. Packed bed consists of a container in which solid material elements having good heat capacity remain packed. The hot air flows from top to bottom of the bed to transfer heat energy. The rise in temperature of solid material takes place and energy can be retained by having properly insulated packed bed. The stored energy can be retrieved by making flow of cold air from bottom to top of the bed. The schematic of packed bed energy storage system for solar air heaters is shown in Fig. (1). The working of such a system is described in detail by Duffie and Beckman (1).

2801 太陽エネルギーを熱源とするヒートポンプの提案(G09 環境工学,21世紀地球環境革命の機械工学:人・マイクロナノ・エネルギー・環境)

Recently, utilizing natural energy effectively has attracted attention from a view point of energy saving. To promote the use of natural energy into the air conditioning field, we have investigated the solar thermal energy utilization system with Solar Wall, which is a type of the solar energy collector. Solar Wall can heat up ambient air has application to many sorts of air conditioning system; for example, ambient air heating in winter, regeneration heat source for the desiccant air conditioning system in summer and so on. This paper discusses the characteristic of Solar Wall by experiment and the performance evaluation of heat pump system with Solar Wall as heat source by simulation. As a result, it is clarified that heat collection efficiency of Solar Wall can be enhanced and COP of heat pump system with Solar Wall increases according to the rise of air volume flow.

Design and cost evaluations of solar energy and waste heat utilization systems with latent thermal storage unit using form-stable high-density polyethylene.

Conceptual designs and cost evaluations were made for three solar thermal application systems and a waste heat recovery system with a latent thermal storage unit using form-stable high-density polyethylene. A detailed design of the storage unit shows that it is economically competitive with other thermal energy storage devices such as the steam accumulator. The solar air conditioning system and the waste heat recovery system with this storage unit are feasible. On the other hand, the solar thermal power generation systems with collectors of non-tracking and nonconcentrating type are not cost-effective, mainly due to low conversion efficiency arising from the low operating temperature. System simulations of the two promising systems were carried out.

Improvement of the Performance of Solar Energy or Waste Heat Utilization Systems by Using Phase-Change Slurry as an Enhanced Heat-Transfer Storage Fluid

This paper is concerned with the benefits of using phase-change slurries as enhanced heat-transfer/storage working fluids in solar energy and waste heat utilization systems. Literature is cited to show that a slurry containing a phase-change material as the dispersed phase promises to have much higher heat-transfer coefficients than conventional single-phase working fluids. Because of the latent heat, the phase-change slurry also requires lower pumping rates and smaller storage tanks than single-phase fluids for the same energy content. These benefits are documented by comparisons of temperature drops, pumping rates, pumping powers, and the sizes of storage tanks for a generic energy collection system operating with and without a slurry.

The utilization of nitrone spin traps in a study of the photochemistry of pigment dispersions

Examples of the use of nitrone spin traps for the elucidation of reaction mechanisms during the illumination of pigment dispersions are presented. Detection of superoxide and hydroxyl radicals with CdS, phthalocyanine, and ZnO is discussed. Singlet oxygen is also detectable with spin traps by following the O2 consumption in these dispersions as a function of illumination. These results are discussed in relation to the applications of pigment dispersions in both novel imaging systems and solar energy utilization systems.

Statistical study of solar radiation information in an equatorial region (Singapore)

Results of regression analysis relating total solar radiation with common meteorological factors, based on data from Singapore, are summarized. The regression coefficients are found to be unstable over different periods of time, producing poor radiation estimates. A set of useful statistical properties of measured radiation data is next presented, showing the expected number of days in a year and in a given month of the year in which daily total radiation falls within a given range of values, and also the frequencies of occurrence of periods of successive days in which radiation is below specified values. Probabilistic limits of figures are also given to enable designers and users of solar energy utilization systems to perform calculations based on ranges of possible values, rather than point estimates, of amounts of expected radiation.

Solar thermal energy storage using heat of dilution: Analysis of heat generation in multistage mixing column

Storage of solar energy is important for the future success of solar energy utilization systems such as solar thermal power plants. Various papers have described the storage methods for storing solar energy. Because of the results of assessing the storage methods proposed in these papers, the method based on heat of dilution was selected by reasons of the ease of heat transfer, the controllability of reaction and the recovery of heat stored. The effectiveness of heat recovered from heat of dilution in the case of storing solar energy in the form of heat of dilution was considered in this paper. Sulfuric acid and water solution used as the typical example of heat of dilution, since its thermodynamic properties were well known. Two liquids were mixed in two different systems of multistage mixing column, and an application of heat of dilution to multipurpose energy utilization was analyzed. The utility of heat of dilution was explained from the results of thermal characteristics of each system.

Application of optical fibers to the transmission of solar radiation

The application of optical fibers to the transmission of solar radiation is discussed. Attenuations of the extraterrestrial solar radiation spectrum in optical fiber materials, fused-silica and soda-lime-silicate glass, are calculated based on intrinsic attenuation mechanisms. It is shown that fused-silica-core optical fibers transmit solar radiation effectively over distances of about 40 m. Possible areas of application of optical fibers to the solar energy utilization systems are suggested.

A terrestrial solar energy power system

Development of an effective solar energy utilization technique is of prime importance in solving the energy crisis mankind is confronted with today. In recent years advancements have been made in high temperature measurements, high efficiency selective radiation materials, high temperature heat pipes, heat storage medium, semiconductor manufacturing techniques, space technology, etc. In this article the authors outline a solar energy utilization system (a terrestrial solar energy power system) and discuss the feasibility of a solar energy power system.