Collector thermal efficiency
In reality the heat loss coefficient UL in Eqs (2) and (42) is not constant but is a function of collector inlet and ambient temperatures. Therefore: TOC o "1-5" h …
Global climate change
The term greenhouse effect has generally been used for the role of the whole atmosphere (mainly water vapour and clouds) in keeping the surface of the earth warm. Recently however, …
Limitations of simulations
Simulations are powerful tools for process design offering a number of advantages as outlined in the previous sections. However, there are limits to their use. For example, it is easy …
Parabolic trough collectors
In order to deliver high temperatures with good efficiency a high performance solar collector is required. Systems with light structures and low cost technology for process heat applications up to …
Water systems
There are many variations of systems used for both solar space heating and service hot water production. The basic configuration is similar to the solar water heating systems outlined in …
Concentrating collectors
Similarly, for concentrating collectors the performance equations (70) and (73) described previously are reasonably well defined as long as the direct beam of solar irradiation is normal to the collector …
Renewable energy technologies
Renewable energy technologies produce marketable energy by converting natural phenomena into useful forms of energy These technologies use the sun’s energy and its direct and indirect effects on the earth …
Economic analysis
The economic analysis of solar energy systems is carried out in order to determine the least cost of meeting the energy needs, considering both solar and non-solar alternatives. The method …
Linear Fresnel reflector
LFR technology relies on an array of linear mirror strips which concentrate light on to a fixed receiver mounted on a linear tower. The LFR field can be imagined as …
Heat pump systems
Heat pumps use mechanical energy to transfer thermal energy from a source at a lower temperature to a sink at a higher temperature. Electrically driven heat pump heating systems have …
Concentrating collector acceptance angle
Another test required for the concentrating collectors is the determination of the collector acceptance angle, which characterises the effect of errors in the tracking mechanism angular orientation. This can be …
History of solar energy
The idea of using solar energy collectors to harness the sun’s power is recorded from the prehistoric times when at 212 BC the Greek scientist/physician Archimedes devised a method to …
Time value of money
It must be noted that a sum of money at hand today worth less than the same sum in the future, because the money at hand can be invested at …
Parabolic dish reflector (PDR)
A parabolic dish reflector, shown schematically in Fig. 11, is a point-focus collector that tracks the sun in two axes, concentrating solar energy onto a receiver located at the focal …
Solar refrigeration
Solar cooling can be considered for two related processes: to provide refrigeration for food and medicine preservation and to provide comfort cooling. Solar refrigeration systems usually operate at intermitted cycles …
Collector time constant
Fig. 2i. Parabolic trough collector incidence angle modifier test results. A last aspect of collector testing is the determination of the heat capacity of a collector in terms of a …
Solar collectors
Solar energy collectors are special kind of heat exchangers that transform solar radiation energy to internal energy of the transport medium. The major component of any solar system is the …
Solar collector applications
Solar collectors have been used in a variety of applications. These are described in this section. In Table 10 the most important technologies in use are listed together with the …
Heliostat field collector
For extremely high inputs of radiant energy, a multiplicity of flat mirrors, or heliostats, using altazimuth mounts, can be used to reflect their incident direct solar radiation onto a common …
Adsorption units
Porous solids, called adsorbents, can physically and reversibly adsorb large volumes of a vapour, called the adsorbate. Though this phenomenon, called solar adsorption, was recognised in the 19th century its …
Collector test results and preliminary collector selection
Collector testing is required in order to evaluate the performance of solar collectors and compare different collectors to select the most appropriate one for a specific application. As can be …
Stationary collectors
Solar energy collectors are basically distinguished by their motion, i. e. stationary, single axis tracking and two - axes tracking, and the operating temperature. Initially, Table 1 Solar energy collectors …
Thermosyphon systems (passive)
Thermosyphon systems, shown schematically in Fig. 24, heat potable water or heat transfer fluid and use natural convection to transport it from the collector to storage. The water in the …
Thermal analysis of collectors
In this section the thermal analysis of the collectors is presented. The two major types of collectors, i. e. flat-plate and concentrating are examined separately. The basic parameter to consider …
Absorption units
Absorption is the process of attracting and holding moisture by substances called desiccants. Desiccants are sorbents, i. e. materials that have an ability to attract and hold other gases or …
Modelling of solar systems
The proper sizing of the components of a solar system is a complex problem which includes both predictable (collector and other components performance characteristics) and unpredictable (weather data) components. In …
Flat-plate collectors
A typical flat-plate solar collector is shown in Fig. 1. When solar radiation passes through a transparent cover and impinges on the blackened absorber surface of high absorptivity, a large …
Integrated collector storage systems (passive)
ICS systems use hot water storage as part of the collector, i. e. the surface of the storage tank is used also as an absorber. As in all other systems, …
Concentrating collectors performance
For concentrating collector both optical and thermal analyses are required. 3.2.1. Optical analysis The concentration ratio (C) is defined as the ratio of the aperture area to the receiver/absorber area, …
Industrial process heat
Beyond the low temperature applications there are several potential fields of application for solar thermal energy at a medium and medium-high temperature level (80-240 °C). The most important of them …
TRNSYS simulation program
TRNSYS is an acronym for a ‘transient simulation’ which is a quasi-steady simulation model. This program [111] was developed by the University of Wisconsin by the members of the Solar …
Glazing materials
2.1.1.1. Glass has been widely used to glaze solar collectors because it can transmit as much as 90% of the incoming shortwave solar irradiation while transmitting virtually none of the …
Direct circulation systems (active)
In direct circulation systems, shown schematically in Fig. 29, a pump is used to circulate potable water from storage to the collectors when there is enough available solar energy to …
3.2.2. Thermal analysis
The generalised thermal analysis of a concentrating solar collector is similar to that of a FPC. It is necessary to derive appropriate expressions for the collector efficiency factor F, the …
Solar industrial air and water systems
There are two types of applications employing solar air collectors the open circuit, and the recirculating applications. In open circuit, heated ambient air is used in industrial applications where because …
