Solar water heater performance evaluation

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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 weather conditions or with a different load profile.

The International Standards organization (ISo) publishes a series of standards, ranging from simple measurement and data correlation methods to complex parameter identification ones. ISo 9459 was developed by the Technical Committee, ISO/TC 180—Solar Energy, to help facilitate the international comparison of solar domestic water heating systems. Because a generalized performance model, which is applicable to all systems, has not yet been developed, it has not been possible to obtain an international consensus for one test method and one standard set of test conditions. Therefore, each method can be applied on its own.

A total of five international standards on solar domestic water heater performance testing have been published:

ISO 9459-1:1993. Solar heating, Domestic water heating systems. Part 1.

Performance rating procedure using indoor test methods. ISO 9459-2:1995. Solar heating, Domestic water heating systems. Part 2. Outdoor test methods for system performance characterization and yearly performance prediction of solar-only systems. ISO 9459-3:1997. Solar heating, Domestic water heating systems. Part 3.

Performance test for solar plus supplementary systems. ISO 9459-4:1992. Solar heating, Domestic water heating systems. Part 4. System performance characterization by means of component tests and computer simulation.

ISO 9459-5:2007. Solar heating, Domestic water heating systems. Part 5. System performance characterization by means of whole-system tests and computer simulation.

Therefore, ISO 9459 is divided into five parts within three broad categories. rating test

• ISO 9459-1 describes test procedures for characterizing the performance of solar domestic water heating systems operated without auxiliary boosting and for predicting annual performance in any given climatic and operating conditions. It is suitable for testing all types of systems, including forced circulation, thermosiphon, and Freon-charged collector systems. The results allow systems to be compared under identical solar, ambient, and load conditions.

Solar Water Heater Performance Evaluation 305

• The test methods in this standard define procedures for the indoor testing of solar water heaters with a solar simulator. The characteristics of the solar simulator are defined in ISO 9845-1:1992 (see Chapter 4, Section 4.1.3). The entire test sequence usually takes 3-5 days and the result is the daily solar contribution for one set of conditions. An indoor test procedure in which the solar simulator is replaced by a controlled heat source, used to simulate the solar energy gain, is also described. This test has not been widely adopted.

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