This program was developed on Labview platform. Labview operating system is the most representative system in the field of graphical programming development platform using virtual instruments. And it is also the most popular and extensive application of data acquisition and control of the development environment. The program will be intuitive and have friendly interface with operator based on Labview. Moreover, the program can be operated easily and operating procedures are shown clearly and intuitively. The whole test process can be seen in the interface and the real-time data can be shown as cures in the graph, so operator can manipulate instruments conveniently and know clearly the true situation what the instrument it is.

The program can be operated in two modes, one is manual operation and the other one is automatic operation. All of information of control system can be displayed on the screen. If there is no problem to deal with by operator, the program will continuously work step by step in the automatic mode.

When some errors happened, the program will enter into the situation of alarm, stop the process and record the situation. According to different test process, the program was operated in different projects, such as determination of daily system performance, determination of the degree of mixing, determination of storage tank heat loss etc. In every test process the interface is made up of three modules, namely flow charts, data curves, error alarm. As shown in Fig.4. In the window of flow chart test system can not only be directly shown in the test process, also be measured and recorded through the data acquisition system, and then be displayed on the real-time curves. These collected data can be used to identify the situation of instruments and supervise the operating situation whether it is normal or not.

The program has many technical advantages as follows. It is simple to develop software to make it suit different conditions by the way of graphical data-flow programming language. And it is convenient to expand and upgrade through modular program. The interactive program interface can make program be operated flexibly.

2. Test Procedure

The test procedure consists of a number of one-day tests which are independent of each other. On each day of the test, the system is allowed to operate outdoors and a single draw-off is applied at the end of day. At the start of each day of the test, the system is preconditioned by flushing it with water at a known temperature. The input, (i. e. the irradiation incident on the system), and the output, (i. e. the energy contained in the hot water draw-off), are measured for each test day and plotted on an input/output diagram. The test days shall cover a range of irradiation values and values of (ta(day)- tmain) so that the dependence of the system performance on these parameters can be established.