Category: 4.Performance of Solar Collectors

Today, most scientists and engineers use personal computers for data acquisition in laboratory research, test and measurement, and industrial automation. To perform the tests outlined in this chapter as well as whole-system tests, a computer data acquisition system (DAS) is required. Many applications use plug-in boards to acquire data and transfer them directly to computer…

In the framework of the European Committee for Standardization, CEN (Comité Européen de Normalisation), the operation of a technical committee dealing with solar thermal collectors and systems has been established. 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…

As we have seen in Chapter 3, the materials used for the construction of the collector should be able to withstand, in addition to the effects created because of the circulating fluid (corrosion, scale deposits, etc.), the adverse effects of the sun’s ultraviolet radiation, and the collector should have an operation life of more than 20 years.…

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…

With the procedure described earlier in this chapter for the performance evaluation of solar energy collectors, the collector performance equation is derived which can be used for the prediction of its output under any conditions. The basic aim of the collector testing is the determination of the collector thermal efficiency under specific conditions and as…

In the equations representing the performance of the solar collectors presented so far, the inlet fluid temperature is used. In some European standards, however (e.g. EN 12975-2: 2006), the average temperature is used, Tm, defined as the arithmetic average of the inlet and outlet temperatures [(Ti + To)/2] and the efficiency is plotted against (Tm − Ta)/Gt. In this case…

For locations that do not have steady environmental conditions for long periods of time, the transient or dynamic system test method can be used. This method involves monitoring the transient response of a collector over a number of days, which include both clear and cloudy conditions. The performance data obtained from the dynamic method allow a…

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…

Flat-plate collectors The performance Eqs (4.9) and (4.11) for FPCs assume that the sun is perpendicular to the plane of the collector, which rarely occurs. For the glass cover plates of an FPC, specular reflection of radiation occurs, thereby reducing the (τα) product. The incidence angle modifier, Kθ, is defined as the ratio of (τα) at some incident angle θ to (τα)…

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…