Placement of Sensors

Proper placement of the collector temperature sensor is important for good system operation. The sensor must have a good thermal contact with the collector plate or piping. Collector sensors may be located on the collector plate, on a pipe near the collector, or in the collector outlet pipe. The best of all is on the collector plate, but this is not the easiest, because dismantling and modification on one collector of the array is required, which would need to be done on site. The easiest and...

Pipes Supports and Insulation

The material of a solar energy system piping may be copper, galvanized steel, stainless steel, or plastic. All pipes are suitable for normal solar system operation except plastic piping, which is used only for low temperature systems, such as swimming pool heating. Another problem related to plastic piping is its high coefficient of expansion, which is 3-10 times as high as that for copper pipes and causes deformation at high temperatures. Piping that carries potable water may be copper,...

Load Heat Exchanger Size Correction

Heat Exchanger Correction Factor

The size of the load heat exchanger strongly affects the performance of the solar energy system. This is because the rate of heat transfer across the load heat exchanger directly influences the temperature of the storage tank, which consequently affects the collector inlet temperature. As the heat exchanger used to heat the building air is reduced in size, the storage tank temperature must increase to supply the same amount of heat energy, resulting in higher collector inlet temperatures and...

Energy Demand And Renewable Energy

Many alternative energy sources can be used instead of fossil fuels. The decision as to what type of energy source should be utilized in each case must be made on the basis of economic, environmental, and safety considerations. Because of the desirable environmental and safety aspects it is widely believed that solar energy should be utilized instead of other alternative energy forms because it can be provided sustainably without harming the environment. If the world economy expands to meet the...

Energyrelated 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 recognized universally and historical data verify that there is a strong relationship between the availability of energy and economic activity. Although in the early 1970s, after the oil crisis, the concern was on the cost of energy, during the past two decades the risk and reality of environmental degradation have become more...

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 nm) and absorption of infrared radiation (Dincer, 1998). A global environmental problem is the depletion of the stratospheric ozone layer, which is caused by the emissions of chlorofluorocarbons (CFCs), halons (chlorinated and brominated organic compounds), and NOx. Ozone depletion can lead to increased...

Ann applications in solar energy Systems

Artificial neural networks have been used by the author in the field of solar energy, for modeling the heat-up response of a solar steam generating plant (Kalogirou et al., 1998), the estimation of a parabolic trough collector intercept factor (Kalogirou et al., 1996), the estimation of a parabolic trough collector local concentration ratio (Kalogirou, 1996a), the design of a solar steam generation system (Kalogirou, 1996b), the performance prediction of a thermosiphon solar water heater...

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 (solar radiation, wind, falling water, and various plants i.e., biomass), gravitational forces (tides), and the heat of the earth's core (geothermal) as the resources from which energy is produced. These resources have massive energy potential however, they are generally diffused and not...

Differential temperature controller

Williams Pump Controller

One of the most important components of an active solar energy system is the temperature controller because a faulty control is usually the cause of poor system performance. In general, control systems should be as simple as possible and should use reliable controllers, which are available nowadays. One of the critical parameters that need to be decided by the designer of the solar system is where to locate the collector, storage, over-temperature, and freezing-temperature sensors. The use of...

A

Where M actual mass of storage capacity kg . Although, in Eq. 11.48 , is included on both sides of equation, it is relatively easy to solve for by trial and error. Since the , -charts are given for various storage capacities and the user has to interpolate, the use of Eq. 11.48 is preferred, so the actual charts are not included in this book. The -charts are used in the same way as the -charts. The values of max Y, and X need to be calculated from the long-term radiation data for the particular...

Passive Space Heating Design

Passive solar heating systems require little, if any, non-renewable energy to function. Every building is passive in the sense that the sun tends to warm it by day and it loses heat at night. Passive systems incorporate solar energy collection, storage, and distribution into the architectural design of the building and make minimal or no use of mechanical equipment, such as fans, to deliver the collected energy. Passive solar heating, cooling, and lighting design must consider the building...

O

Grid Connected Schematic Diagram

FiGURE 9.13 Schematic diagram of a battery. Other parameters related to batteries are the charge or discharge regime and the lifetime of the battery. The charge or discharge regime, expressed in hours, is the parameter that reflects the relationship between the nominal capacity of a battery and the current at which it is charged or discharged for example, a discharge regime is 40 h for a battery with nominal capacity of 200 Ah that is discharged at 5 A. The lifetime of the battery is the number...

Natural ventilation

Natural Suction Ventilation

One way of achieving comfort is by direct evaporation of sweat with air movement through ventilation openings. In many parts of the earth, in some months of the year, local cooling of a building can be achieved with natural ventilation. This is achieved by allowing air that is colder than the building to enter the building. Doing so removes some of the heat stored in the building. The reduction of cooling load varies from 40 to 90 . The lower number applies in warm, humid areas and the larger...

Location of Auxiliary Heater

One important consideration concerning the storage tank is the decision as to the best location for the auxiliary heater. This is especially important for solar space-heating systems because larger amounts of auxiliary energy are usually required and storage tank sizes are large. For maximum utilization of the energy supplied by an auxiliary source, the location of this energy input should be at the load, not at the storage tank. The supply of auxiliary energy at the storage tank will...

Parabolic Trough Collector Systems

Reverse Osmosis Schematic Diagram

Details of this type of collector are given in Chapter 3, Section 3.2.1. As was seen in Chapter 3, parabolic trough collectors are the most mature solar technology to generate heat at temperatures up to 400 C for solar thermal electricity generation or process heat applications. The biggest application of this type of system is the nine southern California power plants known as solar electric generating systems SEGS , which have a total installed capacity of 354 MWe Kearney and Price, 1992 ....

Collector flow rate correction

The -chart of Figure 11.2 has been generated using a collector antifreeze solution flow rate equal to 0.015 L s-m2. A lower flow rate can reduce the energy collection rate significantly, especially if the low flow rate leads to fluid boiling and relief of pressure through the relief valve. Although the product of the mass flow rate and the specific heat of the fluid flowing through the collector strongly affects the performance of the solar energy system, the value used is seldom lower than the...

Pebble bed storage size correction

For the development of the -chart of Figure 11.6, a standard storage capacity of 0.25 cubic meters of pebbles per square meter of collector area was considered, which corresponds to 350 kJ m2- C for typical void fractions and rock properties. Although the performance of air-based systems is not as sensitive to the storage capacity as in liquid-based systems, other storage capacities can be used by modifying the factor X by a storage size correction factor, Xc X, as given by Klein et al., 1977...

Backpropagation architecture

Architectures in the back-propagation category include standard networks, recurrent, feed forward with multiple hidden slabs, and jump connection networks. Back-propagation networks are known for their ability to generalize well on a wide variety of problems. They are a supervised type of network, i.e., trained with both inputs and outputs. Back-propagation networks are used in a large number of working applications, since they tend to generalize well. The first category of neural network...

Photovoltaics

The Cleopatra Alembic

Becquerel discovered the photovoltaic effect in selenium in 1839. The conversion efficiency of the new silicon cells, developed in 1958, was 11 , although the cost was prohibitively high 1000 W . The first practical application of solar cells was in space, where cost was not a barrier, since no other source of power is available. Research in the 1960s resulted in the discovery of other photovoltaic materials such as gallium arsenide GaAs . These could operate at higher temperatures than silicon...

Exercises

6.1 A building has a peak heating load equal to 18.3 kW and a peak cooling load of 23.8 kW. Estimate the seasonal heating and cooling requirements if the heating degree days are 1240 C-days, the cooling degree days are 980 C-days, the winter indoor temperature is 23 C, and the summer indoor temperature is 25 C. The design outdoor temperature for winter is 2 C, and for summer, it is 39 C. 6.2 Estimate the overall heat transfer coefficient of a wall that has the following layers Outside plaster,...

Integrated Collector Storage Systems

Cpc Concentrator

Integrated collector storage ICS systems use the hot water storage as part of the collector, i.e., the surface of the storage tank is used also as the collector FIGURE 5.4 Mantle heat exchanger concept. absorber. As in all other systems, to improve stratification, the hot water is drawn from the top of the tank and cold make-up water enters the bottom of the tank on the opposite side. Usually, the storage tank surface is selectively coated to minimize heat loss. The main disadvantage of the ICS...

Insolation On Tilted Surfaces

The amount of insolation on a terrestrial surface at a given location and time depends on the orientation and slope of the surface. In the case of flat-plate collectors installed at a certain fixed angle, system designers need to have data about the solar radiation on the surface of the collector. Most measured data, however, are for either normal incidence or horizontal. Therefore, it is often necessary to convert these data to radiation on tilted surfaces. Based on these data, a reasonable...

References

Solar process heat in breweries and dairies. In Proceedings of EuroSun 98 on CD ROM, Portoroz, Slovenia. Benz, N., Gut, M., Beikircher, T., 1999. Solar process heat with non-concentrating collectors for food industry. In Proceedings of ISES Solar World Congress on CD ROM, Jerusalem, Israel. Blanco, J., Malato, S., Fernandez, P., Vidal, A., Morales, A., Trincado, P., et al., 1999. Compound parabolic concentrator technology development to commercial solar...

Direct Collection Systems

Double Slope Solar Still

Among the non-conventional methods to desalinate brackish water or seawater is solar distillation. This process requires a comparatively simple technology and can be operated by unskilled workers. Also, due to the low maintenance requirement, it can be used anywhere with a smaller number of problems. A representative example of the direct collection system is the typical solar still, which uses the greenhouse effect to evaporate salty water. It consists of a basin in which a constant amount of...

Exploded View Of A Flat Plate Collector And Absorbed Details

Exploded View Flat Solar Collector

Copyright METEOTEST Bern, Switzerland FIGURE 2.30 Annual total solar irradiation on horizontal surface for Europe. Source Meteonorm database of Meteotest www.Meteonorm.com . Copyright METEOTEST Bern, Switzerland FIGURE 2.30 Annual total solar irradiation on horizontal surface for Europe. Source Meteonorm database of Meteotest www.Meteonorm.com . Global radiation, annual mean 1981-2000 www.meteonorm.com Copyright METEOTEST Bern, Switzerland FIGURE 2.31 Annual total solar irradiation on...

Storage capacity correction

It can be proven that the annual performance of liquid-based solar energy systems is insensitive to the storage capacity, as long as this is more than 50 L of water per square meter of collector area. For the f-chart of Figure 11.2, a standard storage capacity 75 L of stored water per square meter of collector area was considered. Other storage capacities can be used by modifying the factor X by a storage size correction factor Xc X, given by Beckman et al., 1977 Mwa actual storage capacity per...

Mixedmode type

Decrease Firewood Sahara Desert

The mixed-mode dryer is similar to the distributed type with the difference that the walls and roof of the dryer are made from glass, to allow solar energy to warm the products directly, as shown in Figure 7.13. It should be noted that, because drying efficiency increases with temperature, in conventional dryers the maximum possible drying temperature that would not deteriorate the product quality is used. In solar dryers, however, the maximum drying temperature is determined by the solar...

Collector test results and preliminary collector selection

Collector testing is required to evaluate the performance of solar collectors and compare different collectors to select the most appropriate one for a specific application. As can be seen from Sections 4.1-4.5, the tests show how a collector absorbs solar energy and how it loses heat. They also show the effects of angle of incidence of solar radiation and the significant heat capacity effects, which are determined from the collector time constant. Final selection of a collector should be made...

Solarrelated air conditioning

Desiccant Wheel

Some components of systems installed for the purpose of heating a building can also be used to cool it but without the direct use of solar energy. Examples of these systems can be heat pumps, rock bed regenerators, and alternative cooling technologies or passive systems. Heat pumps were examined in Section 6.3.5. The other two methods are briefly introduced here. Rock bed regenerator. Rock bed or pebble bed storage units of solar air heating systems can be night-cooled during summer to store...

Comparison

Solar Profile Angle

The mode of tracking affects the amount of incident radiation falling on the collector surface in proportion to the cosine of the incidence angle. The amount of energy falling on a surface per unit area for the four modes of tracking for the summer and winter solstices and the equinoxes are shown in Table 2.2. This analysis has been performed with the same radiation model used to plot the solar flux figures in this section. Again, the type of the model used here is not important, because it is...

Theoretical Performance Of Thermosiphon Solar Water Heaters

The performance of thermosiphon solar water heaters has been studied extensively, both experimentally and analytically, by numerous researchers. Among the first studies were those of Close 1962 and Gupta and Garg 1968 , who developed one of the first models for the thermal performance of a natural circulation solar water heater with no load. They represented solar radiation and ambient temperature by Fourier series and were able to predict a day's performance in a manner that agreed...

Air Systems

A schematic of a basic solar air heating system with a pebble bed storage unit and auxiliary heating source is shown in Figure 6.11. In this case, the various operation modes are achieved by the use of the dampers shown. Usually, in air systems, it is not practical to have simultaneous addition and removal of energy from the storage. If the energy supplied from the collector or storage is inadequate to meet the load, auxiliary energy can be used to top up the air temperature to cover the...

Windows Sunspaces

The direct gain system is the simplest way of achieving passive heating. In this system, sunlight enters through windows or skylights and is absorbed by the inside surfaces of the building. In a direct gain system, thermal collection, dissipation, storage, and transfer of energy take place within the habitable space. This is the most effective of all passive concepts from the point of view of energy collection and simplicity. Additionally, this system allows the use of sun for lighting daylight...

Wall And Roof Transfer Functions

Conduction transfer functions are used by the TFM to describe the heat flux at the inside of a wall, roof, partition, ceiling, and floor. Combined convection and radiation coefficients on the inside 8.3 W m2-K and outside surfaces 17.0 W m2-K are utilized by the method. The approach uses sol-air temperatures to represent outdoor conditions and assumes constant indoor air temperature. Thus, the heat gain though a wall or roof is given by bn te,9-n6 rc Cn - dn 4e,9-n6 A n 0 n 0 n l qe,9 heat gain...

E hhxi E hxo

Where m is the mass flow rate and x is mass concentration of LiBr in the solution. The first law of thermodynamics yields the energy balance of each component of the absorption system as follows E m.h i - E hh o EQ - EQo W 0 6.70 An overall energy balance of the system requires that the sum of the generator, evaporator, condenser, and absorber heat transfer must be 0. If the absorption system model assumes that the system is in a steady state and that the pump work and environmental heat losses...

Concentrating Collectors

Stationary Compound Parabolic Collector

As we have seen in Section 3.2, concentrating collectors work by interposing an optical device between the source of radiation and the energy-absorbing surface. Therefore, for concentrating collectors, both optical and thermal analyses are required. In this book, only two types of concentrating collectors are analyzed compound parabolic and parabolic trough collectors. Initially, the concentration ratio and its theoretical maximum value are defined. The concentration ratio C is defined as the...

Indirect Collection Systems

The operating principle of indirect collection systems involves the implementation of two separate subsystems a renewable energy collection system solar collector, PV, wind turbine, etc. and a plant for transforming the collected energy to freshwater. Some examples employing renewable energy to power desalination plants are presented in this section a more extensive review is presented in Section 8.5. The plant subsystem is based on one of the following two operating principles Phase-change...

Solar azimuth angle z

Sun Azimuth

The solar azimuth angle, z, is the angle of the sun's rays measured in the horizontal plane from due south true south for the Northern Hemisphere or due north for the Southern Hemisphere westward is designated as positive. The mathematical expression for the solar azimuth angle is This equation is correct, provided that ASHRAE, 1975 cos h gt tan 6 tan L . If not, it means that the sun is behind the E-W line, as shown in Figure 2.4, and the azimuth angle for the morning hours is tc z and for the...

Solar industrial Air and Water Systems

Auxiliary Solar Heating Sytems

The two types of applications employing solar air collectors are the open circuit and the recirculating applications. In the open circuit, heated ambient air is used in industrial applications where, because of contaminants, recirculation of air is not possible. Examples are paint spraying, drying, and supplying fresh air to hospitals. It should be noted that heating outside air is an ideal operation for the collector because it operates very close to ambient temperature, thus more efficiently....

Integraltype

Passive Solar Drying Principle Diagram

Integral-type, natural circulation, solar energy dryers are also called direct passive solar energy dryers. In this system, the crop is placed in a drying chamber, FIGURE 7.15 Schematic diagram of an integral-type passive solar dryer. FIGURE 7.15 Schematic diagram of an integral-type passive solar dryer. which is made with transparent walls therefore, the necessary heat is obtained by the direct absorption of solar radiation at the product, from the internal surfaces of the chamber, and by...

Instrumentation

Instrumentation used in solar energy systems varies from very simple temperature and pressure indicators, energy meters, and visual monitors to data collection and storage systems. It is generally preferable to have some kind of data collection to be able to monitor the actual energy collected from the solar energy system. Visual monitors are used to provide instantaneous readings of various system parameters, such as temperatures and pressures at various locations in the system. Sometimes,...

Steam Generation Methods

Unfired Boiler For Steam Generation

The steam-flash system is shown schematically in Figure 7.5. In this system, water, pressurized to prevent boiling, is circulated through the collector and flashed across a throttling valve into a flash vessel. Treated feedwater input maintains the level in the flash vessel and the sub cooled liquid is recirculated through the collector. The in situ boiling concept, shown in Figure 7.6, uses a similar system configuration with no flash valve. Sub cooled water is heated to boiling and steam...

HEAT sToRAGE sYsTEMs

Thermal storage is one of the main parts of a solar heating, cooling, and powergenerating system. Because for approximately half the year any location is in darkness, heat storage is necessary if the solar system must operate continuously. For some applications, such as swimming pool heating, daytime air heating, and irrigation pumping, intermittent operation is acceptable, but most other uses of solar energy require operating at night and when the sun is hidden behind clouds. Usually the...

The Multi Stage Flash MSF Process

Multi Stage Flash Solar Desalination

The MSF process is composed of a series of elements, called stages. In each stage, condensing steam is used to pre-heat the seawater feed. By fractionating the overall temperature differential between the warm source and seawater into a large number of stages, the system approaches ideal total latent heat recovery. Operation of this system requires pressure gradients in the plant. The principle of operation is shown in Figure 8.4. Current commercial installations are designed with 10-30 stages...

Qu AcFr[GtTa UlT Ta

Heat Balance Solar Colector

This is the same as Eq. 3.31 , with the difference that the inlet fluid temperature T replaces the average plate temperature Tp with the use of the FR. In Eq. 3.60 , the temperature of the inlet fluid, T, depends on the characteristics of the complete solar heating system and the hot water demand or heat demand of the building. However, FR is affected only by the solar collector characteristics, the fluid type, and the fluid flow rate through the collector. FIGURE 3.29 Collector flow factor as...

Ammoniawater absorption systems

Contrary to compression refrigeration machines, which need high-quality electric energy to run, ammonia-water absorption refrigeration machines use low-quality thermal energy. Moreover, because the temperature of the heat source does not usually need to be so high 80-170 C , the waste heat from many processes can be used to power absorption refrigeration machines. In addition, an ammonia-water refrigeration system uses natural substances, which do not cause ozone depletion as working fluids....

European standards

In the framework of the European Committee for Standardization, CEN Comit Europ enne de Normalisation , the operation of a new technical committee dealing with solar thermal collectors and systems has been initiated. Specifically, CEN TC 312, Thermal solar systems and components, was created in 1994, following a request of the European Solar Thermal Industry Federation ESTIF to the CEN Central Secretariat. The scope of CEN TC 312 is the preparation of European standards to cover terminology,...

General Remarks

The -chart design method is used to quickly estimate the long-term performance of solar energy systems of standard configurations. The input data needed are the monthly average radiation and temperature, the monthly load required to heat a building and its service water, and the collector performance parameters obtained from standard collector tests. A number of assumptions are made for the development of the -chart method. The main ones include assumptions that the systems are well built,...

Absorbed Solar Radiation

The main factor affecting the power output from a PV system is the absorbed solar radiation, S, on the PV surface. As was seen in Chapter 3, S depends on the incident radiation, air mass, and incident angle. As in the case of thermal collectors, when radiation data on the plane of the PV are unknown, it is necessary to estimate the absorbed solar radiation using the horizontal data and information on incidence angle. As in thermal collectors, the absorbed solar radiation includes the beam,...

Power Tower Systems

Solar Tower Direct Steam Generation

As was explained in Chapter 3, Section 3.2.4, power towers or central receiver systems use thousands of individual sun-tracking mirrors, called heliostats, to reflect solar energy onto a receiver located atop a tall tower. The receiver collects the sun's heat in a heat transfer fluid molten salt that flows through the receiver. This is then passed optionally to storage and finally to a power conversion system, which converts the thermal energy into electricity and supplies it to the grid....

Pv System Gives 9a When The Solar Radiation Is 750

When the array supplies all energy to a DC load, the actual energy delivered, Ed,dc, is obtained by When the battery directly supplies a DC load, the efficiency of the battery, r bat, is accounted for, and the actual energy delivered, Ed,dc,bat, is obtained from When the battery is used to supply energy to an AC load, the inverter efficiency is also accounted for Ed,ac,bat EA nbat ninv ist 9.46 Finally, when the array supplies all energy to an AC load, the actual energy delivered, Ed,ac, is...

A Brief HiStory Of Solar Energy

John Ericsson Parabolic

Solar energy is the oldest energy source ever used. The sun was adored by many ancient civilizations as a powerful god. The first known practical application was in drying for preserving food Kalogirou, 2004 . Probably the oldest large-scale application known to us is the burning of the Roman fleet in the bay of Syracuse by Archimedes, the Greek mathematician and philosopher 287-212 B.C. . Scientists discussed this event for centuries. From 100 B.C. to 1100 A.D., authors made reference to this...

Review Of Renewable Energy Desalination Systems

Renewable energy systems offer alternative solutions to decrease the dependence on fossil fuels. The total worldwide renewable energy desalination installations amount to capacities of less than 1 of that of conventional fossil-fueled desalination plants Delyannis, 2003 . This is mainly due to the high capital and maintenance costs required by renewable energy, making these desalination plants non-competitive with conventional fuel desalination plants. Solar desalination plants coupled with...

Thermal Analysis Of Flatplate Collectors

Tilted Flat Plate Collector

In this section, the thermal analysis of the collectors is presented. The two major types of collectors, flat plate and concentrating, are examined separately. The basic parameter to consider is the collector thermal efficiency. This is defined as the ratio of the useful energy delivered to the energy incident on the collector aperture. The incident solar flux consists of direct and diffuse radiation. While flat-plate collectors can collect both, concentrating collectors can utilize direct...

Pool Heating Systems

Solar pool heating systems require no separate storage tank, because the pool itself serves as storage. In most cases, the pool's filtration pump is used to circulate the water through solar panels or plastic pipes. For daylong operation, no automatic controls are required, because the pool usually operates when the sun is shining. If such controls are employed, they are used to direct the flow of filtered water to the collectors only when solar heat is available. This can also be achieved by a...

Thermal Analysis of Compound Parabolic Collectors

Compound Parabolic Collector

The instantaneous efficiency, r , of a CPC is defined as the useful energy gain divided by the incident radiation on the aperture plane that is, In Eq. 3.85 , Gt is the total incident radiation on the aperture plane. The useful energy, Qu, is given by an equation similar to Eq. 3.60 , using the concept of absorbed radiation as Qu Fr SAa - ArUL T - Ta 3.86 The absorbed radiation, S, is obtained from Duffie and Beckman, 1991 S GB,CPCTc,BTCPC,Ba B GD,CPCTc,D TCPC,Da D GG,CPCTc,G TCPC,GaG tc...

Collector Thermal Efficiency

Parabolic Trough Collector Efficiency

The collector performance test is performed under steady-state conditions, with steady radiant energy falling on the collector surface, a steady fluid flow rate, and constant wind speed and ambient temperature. When a constant inlet fluid temperature is supplied to the collector, it is possible to maintain a constant outlet fluid temperature from the collector. In this case, the useful energy gain from the collector is calculated from From Chapter 3, we have seen that the useful energy...

General regression neural network architecture

Generalized Regression Neural Network

Another type of architecture is general regression neural networks GRNNs , which are known for their ability to train quickly on sparse data sets. In numerous tests, it was found that a GRNN responds much better than back-propagation to many types of problems, although this is not a rule. It is especially useful for continuous function approximation. A GRNN can have multidimensional input, and it will fit multidimensional surfaces through data. GRNNs work by measuring how far a given sample...

Concentrating collector acceptance angle

Sthe Transfer Solar Energy Graphs

Another test required for the concentrating collectors is the determination of the collector acceptance angle, which characterizes the effect of errors in the tracking mechanism angular orientation. This can be found with the tracking mechanism disengaged and by measuring the efficiency at various out-of-focus angles as the sun is traveling over the collector plane. An example is shown in Figure 4.8, where the angle of incidence measured from the normal to the tracking axis i.e., out-of-focus...

Info

Longitude of the station W West, E East Degrees Minutes Elevation of station in meters above sea level had observations, measurements, or estimates made at daily, instead of hourly, intervals. Consequently, the data values for broadband aerosol optical depth, snow depth, and days since last snowfall represent the values available for the day indicated. With the exception of extraterrestrial horizontal and extraterrestrial direct radiation, the two field positions immediately following the data...

Reverse Circulation In Thermosiphon Systems

At night or whenever the collector is cooler than the water in the tank, the direction of the thermosiphon flow reverses, thus cooling the stored water. It should be noted that thermosiphon collector loop circulation is driven by thermal stratification in the collector loop and the section of the tank below the collector flow return level. The major problem in thermosiphon system design is to minimize heat loss due to reverse thermosiphon circulation at night, when the sky temperature is low....

Solar water heater performance evaluation

Many test procedures have been proposed by various organizations to determine the thermal performance of solar water heaters. Testing of the complete system may serve a number of purposes. The main one is the prediction of the system's long-term thermal performance. System testing may also be used as a diagnostic tool to identify failure and causes of failure in system performance. other purposes include the determination of the change in performance as a result of operation under different...

Hourly Utilizability

Utilizability can also be defined as the fraction of incident solar radiation that can be converted into useful heat. It is the fraction utilized by a collector having no optical losses and a heat removal factor of unity i.e., Fr to 1, operating at a fixed inlet to ambient temperature difference. It should be noted that the utilizability of this collector is always less than 1, since thermal losses exist in the collector. The Hottel-Whillier equation Hottel and Whillier, 1955 relates the rate...

Solar Power Paris Expositions

Solar Thermal Turbine Diagram

As was seen in Chapter 1, Section 1.5, solar thermal power systems were among the very first applications of solar energy. During the 18th century, solar furnaces capable of melting iron, copper, and other metals were constructed of polished iron, glass lenses, and mirrors. The furnaces were in use throughout Europe and the Middle East. The most notable examples are the solar furnace built by the well-known French chemist Lavoisier in 1774, various concentrators built by the French naturalist...

Cggb

3 _ 9.81 X 0.707 X 314.7 - 296.8 X 0.023 Therefore, from Eq. 3.11 , we have the following. _ 1708 sin 1.8 X 35 16 j 132,648 X cos 35 ' The convection heat transfer coefficient from glass to ambient is the wind loss coefficient given by Eq. 3.28 . In this equation, the characteristic length is the length of the collector, equal to 2 m. Therefore, hcgi-a hw 8.6 2.5 0'6 20'4 11.294W m2-K To check whether the assumed values of Tg1 and Tg2 are correct, the heat transfer coefficients are substituted...

Polar ns axis with ew tracking

Solar Tracking Advantage

For a plane rotated about a north-south axis parallel to the earth's axis, with continuous adjustment, 9 is equal to FIGuRE 2.13 Daily variation of solar flux tilted N-S axis with tilt adjusted daily. FIGuRE 2.13 Daily variation of solar flux tilted N-S axis with tilt adjusted daily. FiGuRE 2.14 Daily variation of solar flux polar N-S axis with E-w tracking. FiGuRE 2.14 Daily variation of solar flux polar N-S axis with E-w tracking. This configuration is shown in Figure 2.10b. As can be seen,...

Parabola construction

Eurotrough Drive System

To achieve cost-effectiveness in mass production, the collector structure must feature not only a high stiffness-to-weight ratio, to keep the material content to a minimum, but also be amenable to low-labor manufacturing processes. A number of structural concepts have been proposed, such as steel framework structures with central torque tubes or double V trusses and fiberglass Kalogirou et al., 1994b . A recent development in this type of collectors is the design and manufacture of the...

Testing and computer simulation

ISO 9459-4 is a procedure for characterizing annual system performance and uses measured component characteristics in the computer simulation program TRNSYS described in Chapter 11, Section 11.5.1 . The procedures for characterizing the performance of system components other than collectors are also presented in this part of ISO 9459. Procedures specified in ISO 9806-1 see Chapter 4 are used to determine collector performance, whereas other tests are specified for characterizing the storage...

Optimum Collector Temperature

Iso 9806 Report

By substituting Eqs. 3.133 and 3.134 into Eq. 3.142 , the rate of entropy generation can be written as S Ur Tr _ T0 _ Q Q _ UrAr Tr _ T0 3.145 By applying Eq. 3.137 in 3.145 and performing various manipulations, The dimensionless term, Sgen UrAr, accounts for the fact that the entropy generation rate scales with the finite size of the system, which is described by By differentiating Eq. 3.146 with respect to 9 and setting it to 0, the optimum collector temperature 9opt for minimum entropy...

Heat Loss Surface Convection 3600

A 500 m2 light-colored swimming pool is located in a normal suburban site, where the measured wind speed at 10 m height is 3 m s. The water temperature is 25 C, the ambient air temperature is 17 C, and relative humidity is 60 . There are no swimmers in the pool, the temperature of the make-up water is 22 C, and the solar irradiation on a horizontal surface for the day is 20.2 MJ m2-d. How much energy must the solar system supply gss to the pool to keep its temperature to 25 C The energy balance...

Solar Dryers

Solar drying is another very important application of solar energy. Solar dryers use air collectors to collect solar energy. Solar dryers are used primarily by the agricultural industry. The purpose of drying an agricultural product is to reduce its moisture content to a level that prevents its deterioration. In drying, two processes take place One is a heat transfer to the product using energy from the heating source, and the other is a mass transfer of moisture from the interior of the...

Solar sorption cooling

Sorbents are materials that have an ability to attract and hold other gases or liquids. Desiccants are sorbents that have a particular affinity for water. The process of attracting and holding moisture is described as either absorption or adsorption, depending on whether the desiccant undergoes a chemical change as it takes on moisture. Absorption changes the desiccant the way, for example, table salt changes from a solid to a liquid as it absorbs moisture. Adsorption, on the other hand, does...

Genopt and trnopt programs

When simulation models are used to simulate and design a system, it is usually not easy to determine the parameter values that lead to optimal system performance. This is sometimes due to time constraints, since it is time consuming for a user to change the input values, run the simulation, interpret the new results, and guess how to change the input for the next trial. Sometimes time is not a problem, but due to the complexity of the system analyzed, the user is just not capable of...

The Heat Balance Method

The heat balance method is able to provide dynamic simulations of the building load. It is the foundation for all calculation methods that can be used to estimate the heating and cooling loads. Since all energy flows in each zone must be balanced, a set of energy balance equations for the zone air and the interior and exterior surfaces of each wall, roof, and floor must be solved simultaneously. The energy balance method combines various equations, such as equations for transient conduction...

Solar Angles

Latitude Angle Solar

The earth makes one rotation about its axis every 24 h and completes a revolution about the sun in a period of approximately 365.25 days. This revolution is not circular but follows an ellipse with the sun at one of the foci, as shown in Figure 2.3. The eccentricity, e, of the earth's orbit is very small, equal to 0.01673. Therefore, the orbit of the earth round the sun is almost circular. The sun-earth distance, R, at perihelion shortest distance, at January 3 and aphelion longest distance, at...

Cell Temperature

As was seen in Section 9.1.3, the performance of the solar cell depends on the cell temperature. This temperature can be determined by an energy balance and considering that the absorbed solar energy that is not converted to electricity is converted to heat, which is dissipated to the environment. Generally, when operating solar cells at elevated temperatures, their efficiency is lowered. In cases where this heat dissipation is not possible, as in building integrated photovoltaics and...

Black box correlation procedures

ISO 9459-2 is applicable to solar-only systems and solar preheat systems. The performance test for solar-only systems is a black box procedure, which produces a family of input-output characteristics for a system. The test results may be used directly with daily mean values of local solar irradiation, ambient air temperature, and cold-water temperature data to predict annual system performance. The results of tests performed in accordance with ISO 9459-2 permit performance predictions for a...

Vm N Vc

The equivalent series resistance of the module, given by 4. The thermal voltage in the semiconductor of a single solar cell, given by The current practice dictates that the performance of a PV module is determined by exposing it at known standard rating conditions SRCs of irradiance, GUo 1000 W m2, and cell temperature, Tf 25 C. These conditions are different from the nominal operating cell temperature NOCT , as indicated in Table 9.1. Irradiation GUo 1000 W m2 Cell temperature T 25 C...

Solar Steam GeneratiOn Systems

Parabolic trough collectors are frequently employed for solar steam generation because relatively high temperatures can be obtained without serious degradation in the collector efficiency. Low-temperature steam can be used in industrial applications, in sterilization, and for powering desalination evaporators. Three methods have been employed to generate steam using parabolic trough collectors Kalogirou et al., 1997 1. The steam-flash concept, in which pressurized water is heated in the...

Heat pump Systems

Heat Pump Install Parallel

Active solar energy systems can also be combined with heat pumps for domestic water heating or space heating. In residential heating, the solar energy system can be used in parallel with a heat pump, which supplies auxiliary energy when the sun is not available. Additionally, for domestic water systems requiring high water temperatures, a heat pump can be placed in series with the solar storage tank. A heat pump is a device that pumps heat from a low-temperature source to a higher-temperature...

Evaporation heat loss

The following analysis is for a still pool as per ISO TR 12596 1995 1995a . The evaporative heat loss from a still outdoor pool is a function of the wind speed and of the vapor pressure difference between the pool water and the atmosphere, given by qe 5.64 5.96vo3 CPw - Pa 5.18 qe heat loss by evaporation MJ m2-d . Pw saturation water vapor pressure at water temperature, tw kPa . Pa partial water vapor pressure in the air kPa . v0.3 wind speed velocity at a height of 0.3 m above the pool m s ....

Horizontal ns axis with ew tracking

Day Energy Curve

For a plane rotated about a horizontal north-south axis with continuous adjustment to minimize the angle of incidence, 9 can be obtained from Kreith and Kreider, 1978 Duffie and Beckman, 1991 cos 9 sin2 a cos2 6 sin2 h 2.28a or from this equation Meinel and Meinel, 1976 cos 9 cos cos h cos 6 sin2 h 2.28b The basic geometry of this configuration is shown in Figure 2.10d. The greatest advantage of this arrangement is that very small shadowing effects are encountered when more than one collector...

Unglazed Collectors

Unglazed collectors are more difficult to test, because their operation is influenced by not only the solar radiation and ambient temperature but also the wind speed. The last factor influences the collector performance to a great extent, since there is no glazing. Because it is very difficult to find periods of steady wind conditions constant wind speed and direction , the ISO 9806-3 1995 for unglazed collector testing recommends that an artificial wind generator is used to control the wind...

Water Systems

Solar Space Heating Systems Diagram

Many variaties of systems can be used for both solar space heating and domestic hot water production. The basic configurations are similar to the solar water heating systems outlined in Sections 5.2.1 and 5.2.2. When used for both space and hot water production and because solar-heated water can be added to storage at the same time that hot water is removed from storage to meet building loads, the system allows independent control of the solar collector-storage and storage-auxiliary-load loops....

2880 Kj Of Solar Energy

Repeat Example 4.2 by considering the system to have a fully mixed storage tank of 100 L and no load. The initial storage tank temperature at the beginning of the day is 40 C and the environmental temperature at the area where the storage tank is located is equal to the ambient air temperature. The tank UA value is 12 W C. Calculate the useful energy collected over the day. By using Eq. 5.34 , the new storage tank temperature can be considered as the collector inlet. This is correct for the...

Declination

Solar Energy Variation During The Day

As shown in Figure 2.3 the earth axis of rotation the polar axis is always inclined at an angle of 23.45 from the ecliptic axis, which is normal to the ecliptic plane. The ecliptic plane is the plane of orbit of the earth around the sun. As the earth rotates around the sun it is as if the polar axis is moving with respect to the sun. The solar declination is the angular distance of the sun's rays north or south of the equator, north declination designated as positive. As shown in Figure 2.5 it...

Process Selection

During the design stage of a renewable energy-powered desalination system, the designer must select a process suitable for that particular application. The factors that should be considered for such a selection are the following Kalogirou, 2005 1. The suitability of the process for renewable energy application. 2. The effectiveness of the process with respect to energy consumption. 3. The amount of freshwater required in a particular application, in combination with the range of applicability...

Cpc Evacuated Tube

Heat Storage Latent Tank

FIGURE 3.7 schematic diagram of an evacuated tube collector. influences, such as condensation and moisture, cause early deterioration of internal materials, resulting in reduced performance and system failure. Evacuated heat pipe solar collectors tubes operate differently than the other collectors available on the market. These solar collectors consist of a heat pipe inside a vacuum-sealed tube, as shown in Figure 3.7. In an actual installation, many tubes are connected to the same manifold as...

T-s Diagram Of Regenerative Rankine Cycle

Rankine Cycle Diagram Reheat

Or h4. h3 - turbine h3 - h4 3151 - 0.8 3151 - 2787 2860 kJ kg. At point 5, P5 13 bar and T5 390 C. From superheated steam tables, h5 3238 kJ kg and s5 7.212 kJ kg-K. At point 6, s6 s5 7.212 kJ kg-K. From the problem definition, P6 0.16 bar. From steam tables, s6f 0.772 kJ kg-K and s6g 7.985 kJ kg-K. Therefore, at this point, we have a wet vapor and its dryness fraction is s - sf _ 7.212 - G.772 7.9S5 - G.772 At a pressure of 0.16 bar, hf 232 kJ kg and hfg 2369 kJ kg therefore, h6 hf xhfg 232...

Air System Thermal Storage

Hot Air Collector

The most common storage media for air collectors are rocks. Other possible media include PCM, water, and the inherent building mass. Gravel is widely used as a storage medium because it is abundant and relatively inexpensive. In cases where large interior temperature swings can be tolerated, the inherent structure of the building may be sufficient for thermal storage. Loads requiring no storage are usually the most cost-effective applications of air collectors, and heated air from the...

Building construction Thermal Mass Effects

Heat can be stored in the structural materials of the building to reduce the indoor temperature, reduce the cooling load peaks, and shift the time that maximum load occurs. The storage material is referred to as the thermal mass. In winter, during periods of high solar gain, energy is stored in the thermal mass, avoiding overheating. In the late afternoon and evening hours, when energy is needed, heat is released into the building, satisfying part of the heating load. In summer, the thermal...

Dish Systems

Solar Dish Systems

As was seen in Chapter 3, Section 3.2.3, dish systems use dish-shaped parabolic mirrors as reflectors to concentrate and focus the sun's rays onto a receiver, which is mounted above the dish at the dish focal point. The receiver absorbs the energy and converts it into thermal energy. This can be used directly as heat or can support chemical processes, but its most common application is in power generation. The thermal energy can be either transported to a central generator for conversion or...

Suntracking Concentrating Collectors

Sun Collector Convection

Energy delivery temperatures can be increased by decreasing the area from which the heat losses occur. Temperatures far above those attainable by flat-plate collectors can be reached if a large amount of solar radiation is concentrated on a relatively small collection area. This is done by interposing an optical device between the source of radiation and the energy-absorbing surface. Concentrating collectors exhibit certain advantages over the conventional flat-plate type Kalogirou et al.,...

Compound Parabolic Collector

Compound Parabolic Collector

,ec n 2 lt e lt 3n 2 - ec 5.16 The two expressions for p 9 are equivalent for the point P in Figure 5.5, where 9 9c -rc 2. The curve is generated by incrementing 9 in radians, calculating p, then calculating the coordinates, X and Y, by X R sin e - p cos e Y -R cos e - p sin e Figure 5.5 shows a full, untruncated curve, which is the mathematical solution for a reflector shape with the maximum possible concentration ratio. The reflector shape shown in Figure 5.5 is not the most practical design...

Desalination Processes

Desalination can be achieved using a number of techniques. Industrial desalination technologies either use phase change or involve semipermeable membranes to separate the solvent or some solutes. Therefore, desalination techniques may be classified into the following categories phase change or thermal processes and membrane or single-phase processes. All processes require a chemical pre-treatment of raw seawater to avoid scaling, foaming, corrosion, biological growth, and fouling and also...

Galvanic corrosion

Galvanic corrosion is caused by the electrical contact between dissimilar metals in a fluid stream. It is therefore very important not no use different materials for the collector construction and piping manifolds. For example, if copper is used for the construction of the collector, the supply and return piping should also be made from copper. Where different metals must be used, dielectric unions between dissimilar metals must be used to prevent electrical contact. Of the possible metals used...

Degree Day Method

Frequently, in energy calculations, simpler methods are required. One such simple method, which can give comparatively accurate results, is the degree day method. This method is used to predict the seasonal energy consumption. Each degree that the average outdoor air temperature falls below a balance temperature, Tb, of 18.3 C 65 F represents a degree day. The number of degree days in a day is obtained approximately by the difference of Tb and the average outdoor air temperature, Tav, defined...

Building Heat Transfer

Heat Transfer Through Wall

The design of space heating or cooling systems for a building requires the determination of the building thermal resistance. Heat is transferred in building components by all modes conduction, convection, and radiation. In an electrical analogy, the rate of heat transfer through each building component can be obtained from Q _ total UA X ATota 6.28 ATtotal total temperature difference between inside and outside air K . totai total thermal resistance across the building element, YRi m2-K W . A...

Materials Processing

Solar energy material processing involves affecting the chemical conversion of materials by their direct exposure to concentrated solar energy. For this purpose, we use solar furnaces made of high-concentration, hence, high-temperature, collectors of the parabolic dish or heliostat type. Solar energy can also assist in the processing of energy-intensive, high-temperature materials, as in the production of solar aluminum, the manufacture of which is one of the most energy-intensive processes. It...

Indirect Water Heating Systems

Indirect Hot Water System

A schematic diagram of indirect water heating systems is shown in Figure 5.11. In this system, a heat transfer fluid is circulated through the closed collector loop to a heat exchanger, where its heat is transferred to the potable water. The most commonly used heat transfer fluids are water-ethylene glycol solutions, although other heat transfer fluids such as silicone oils and refrigerants can be used. When fluids that are non-potable or toxic are used, double-wall heat exchangers should be...