Solar thermal collectors and applications
1. Introduction The sun is a sphere of intensely hot gaseous matter with a diameter of 1.39 X 109 m. The solar energy strikes our planet a mere 8 min …
WATSUN simulation program
WATSUN simulates active solar systems and is developed by the Watsun Simulation Laboratory of the University of Waterloo in Canada [119]. It is a ready-made program that the user can …
Collector absorbing plates
2.1.1.2. The collector plate absorbs as much of the irradiation as possible through the glazing, while loosing as little heat as possible upward to the atmosphere and downward through the …
Indirect water heating systems (active)
Indirect water heating systems, shown schematically in Fig. 31, circulate a heat transfer fluid through the closed collector loop to a heat exchanger, where its heat is transferred to the …
Second law analysis
Tr. The remaining fraction Qo represents the collector - ambient heat loss: Qo = Q* - Q (46) For imaging concentrating collectors Qo is proportional to the receiver-ambient temperature …
Solar steam generation systems
PTC are frequently employed for solar steam generation, because relatively high temperatures can be obtained without any serious degradation in the collector efficiency. Low temperature steam can be used in …
Energy related environmental problems
Energy is considered a prime agent in the generation of wealth and a significant factor in economic development. The importance of energy in economic development is recognised universally and historical …
Polysun simulation program
Polysun program provides dynamical annual simulations of solar thermal systems and helps to optimise them [120]. It operates with dynamic time steps from 1 s to 1 h, thus simulation …
Compound parabolic collectors
CPC are non-imaging concentrators. These have the capability of reflecting to the absorber all of the incident radiation within wide limits. Their potential as collectors of solar energy was pointed …
Air systems
Air systems are indirect water heating systems that circulate air via ductwork through the collectors to an air-to - liquid heat exchanger. In the heat exchanger, heat is transferred to …
Minimum entropy genчeration rate
The minimization of the entropy generation rate is the same as the maximization of the power output. The process of solar energy collection is accompanied by the generation of entropy …
Solar desalination systems
Fig. 41. The unfired-boiler steam generation concept. Water is one of the most abundant resources on earth, covering three-fourths of the planet’s surface. About 97% of the earth’s water is …
Acid rain
This is a form of pollution depletion in which SO2 and NOx produced by the combustion of fossil fuels are transported over great distances through the atmosphere and deposited via …
F-Chart method and program
The method was developed by Beckman et al. [122]. The method provides a means for estimating the fraction of a total heating and cooling that will be supplied by solar …
Table 3 Characteristics of a typical CPC system Parameter Value F : collector fin efficiency factor 0.9 UL : overall loss coefficient of 1.5 collector per unit aperture area (W/m2 0C) pR : reflectivity of walls of CPC 0.85 Uc : half-acceptance angle of CPC (degrees) 45 Ratio of truncated to 0.67 full height of CPC Axis orientation Receiver axis is horizontal and in a plane with a slope of 350 (transverse) a: absorbtance of absorber 0.95 plate Ng : number of cover plates 1 hR : index of refraction of cover material 1.526 KL : product of extinction coefficient and the thickness of 0.0375 each cover plate Collector slope angle (local latitude) . Evacuated tube collectors
Conventional simple flat-plate solar collectors were developed for use in sunny and warm climates. Their benefits however are greatly reduced when conditions become unfavourable during cold, cloudy and windy days. …
Solar space heating and cooling
The components and subsystems discussed in Section 5.1 may be combined to create a wide variety of building solar heating and cooling systems. There are again two principal categories of …
(Ti — Ta) Gt n = Frto: — c1 — c2 (71) n = Fr no where 0out = T0Ut/T0, = Tjn/To, Ns is the entropy generation number and M is the mass flow number given by: S T N _ SgenT ° Ns Q* and M = mcpT0 Q* (67) and if we denote c0 = FRra and x = (Ti — Ta)/Gt then: n = c0 — c1x — c2Gtx2 (72) And for concentrating collectors the efficiency can be written as: If the inlet temperature is fixed вт = 1, then the entropy generation rate is a function of only M and Uout. These parameters are interdependent because the collector outlet temperature depends on the mass flow rate. c!(Tj — Ta). CGb c2(Tj — Ta)2. CGb (73) and if we denote k0 = FRno, k1 = c1/C, k2 = c2/C and y = (Ti — Ta)/Gb : then: n = k0 — k1y — k2Gby2 (74) . Performance of solar collectors
ASHRAE Standard 93:1986 [108] for testing the thermal performance of collectors is undoubtedly the one most often used to evaluate the performance of flat-plate and concentrating solar collectors. The thermal …
Ozone layer depletion
The ozone present in the stratosphere, at altitudes between 12 and 25 km, plays a natural equilibrium - maintaining role for the earth, through absorption of ultraviolet (UV) radiation (240-320 …
Artificial neural networks in solar energy systems modelling and prediction
Artificial neural networks mimic somewhat the learning process of a human brain They are widely accepted as a technology offering an alternative way to tackle complex and ill specified problems. …
Sun tracking concentrating collectors
Energy delivery temperatures can be increased by decreasing the area from which the heat losses occur. Temperatures far above those attainable by FPC can be reached if a large amount …
. Space heating and service hot water
It is useful to consider solar systems as having five basic modes of operation, depending on the conditions that exist in the system at a particular time [97]: 1. If …
Second law analysis
Tr. The remaining fraction Qo represents the collector - ambient heat loss: Qo = Q* - Q (46) For imaging concentrating collectors Qo is proportional to the receiver-ambient temperature …
Solar thermal power systems
Conversion of solar to mechanical and electrical energy has been the objective of experiments for more than a century, starting from 1872 when Mouchot exhibited a steam-powered printing press at …
Artificial neural networks in solar energy systems modelling and prediction
Artificial neural networks mimic somewhat the learning process of a human brain They are widely accepted as a technology offering an alternative way to tackle complex and ill specified problems. …
Collector absorbing plates
2.1.1.2. The collector plate absorbs as much of the irradiation as possible through the glazing, while loosing as little heat as possible upward to the atmosphere and downward through the …
. Space heating and service hot water
It is useful to consider solar systems as having five basic modes of operation, depending on the conditions that exist in the system at a particular time [97]: 1. If …
. Performance of solar collectors
ASHRAE Standard 93:1986 [108] for testing the thermal performance of collectors is undoubtedly the one most often used to evaluate the performance of flat-plate and concentrating solar collectors. The thermal …
Parabolic trough collector systems
Several parabolic trough solar thermal systems have been build and operated throughout the world. Most of these systems provide process steam to industry. They displace fossil fuels such as oil …
Energy related environmental problems
Energy is considered a prime agent in the generation of wealth and a significant factor in economic development. The importance of energy in economic development is recognised universally and historical …
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 …
Compound parabolic collectors
CPC are non-imaging concentrators. These have the capability of reflecting to the absorber all of the incident radiation within wide limits. Their potential as collectors of solar energy was pointed …
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 …
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: FrUl = c1 + …
Power tower systems
In power tower systems, heliostats reflect and concentrate sunlight onto a central tower-mounted receiver where the energy is transferred to a heat transfer fluid. This energy is then passed either …
Acid rain
This is a form of pollution depletion in which SO2 and NOx produced by the combustion of fossil fuels are transported over great distances through the atmosphere and deposited via …
