Simple Monitoring

Why simple monitoring of SHIP?

Owners of SWHS for industrial processes (SHIP) want to save fuel and money with their SWHS as expected by the system designer. Therefore they have to know, if their SWHS runs efficiently. Simple monitoring systems shall provide information to the system operator, if the SWHS perform as expected.

Definition and objectives

Simple monitoring is characterised by

an optimised data-accuracy-to-cost relation (sensors are used, which provide a minimum accuracy level and are optimised by the cost to accuracy level)

medium resolution (only heat meter data must be stored, a low temporal resolution is sufficient, e.g. solar yield per hour or per day)

measurement of basic data (only the most important values are measured)

easy interpretation (the data watched should be easy to interpret)

The objectives of simple monitoring are

to provide easy to understand information on the functionality of the SWHS

to give an indication, if the performance is significantly lower than expected, that the user can call the system supplier for control and maintenance

Simple monitoring concept for SHIP systems

Based on the analysis of representative examples and the scientific monitoring of two Indian SHIP systems within the SoPro India project and the experiences from monitoring on SWHS in Germany, following recommendations are made for simple monitoring.

In the following the monitoring systems are described.

Operation of collector circuit

The correct operation of the collector and the collector circuit can be checked by inspecting the temperatures of the collector (close to the collector outlet), and the storage tank temperatures at the top and at the bottom. These temperatures are perhaps already measured by the controller, otherwise they can be measured electronically or mechanically.

The SHIP system is operating efficiently, if on a sunny day:

the collector temperature is between 60C and 90C during circulation of the water

the collector temperature is above 80C if the water is not circulating

the temperature at the bottom of the storage tank did increase significantly during the day

the pump is operating in a forced circulation system if the temperature difference between the collector outlet and the storage tank at the bottom is above a threshold set by the controller

Temperature sensors at the collector (left, middle) and at the bottom of the storage tank (right)

Solar yield delivered to the process

What finally counts is the solar energy delivered to the process. The amount of energy can be measured by a heat meter installed between the storage tank and the heat demanding process.

The SWHS supplier should predict the solar yield delivered to the process based on the basic assumptions on solar irradiation, solar collector efficiency and process heat demand, preferably using a planning software The annual solar yield measured should be compared with the predicted solar yield. Minor deviations could be caused by variation of solar irradiation (which vary typically by about 10% from year to year). If the solar yield is significantly lower than predicted, the SWHS supplier should be asked to maintain the system and evaluate the reason for the lower performance.

Heat meter with temperature (T) and flow rate (F) sensors measuring the heat delivered to the process