Sandia National Laboratories

Over the last 7 years, problems have been identified in some of the solar-powered sites, including shorter than anticipated battery life, reliability of the charge controllers, vandalism, and theft. In addition, as automation systems become more complex, sizing the solar-energy system is becoming increasingly important to provide reliable system operation.

To help eliminate future problems, Reclamation and Sandia National Laboratories have initiated a cooperative effort to determine what data and analysis are needed to anticipate impending system problems with these automated sites. Experience in anticipating problems at these photovoltaic powered sites is to be extended to other sites that use fixed power as well. The approach will be to monitor system parameters and use that real-time data for analysis. In addition to water levels used for gate control, system diagnostic measurements will be recorded that include current, voltage, and acceptable environmental conditions that describe normal system operation. Abnormal operating conditions can be recognized as deviations from this standard profile. This analysis can support a program of pro-active system maintenance to prevent or minimize downtime.

The solar energy system consists of several components. They are the photovoltaic (PV) modules, a battery for energy storage, and a charge controller that interfaces with the storage battery and the PV modules. The PV module converts the sunlight to electrical energy that can be stored in the battery for operation during the night or periods of reduced sunlight. A charge controller is used to protect the battery from being overcharged by the PV modules and it protects the battery from being too deeply discharged.

Photovoltaic modules are the most reliable component in this type of renewable energy system. Manufacturing and design have sufficiently improved so that 20-year lifetimes are attainable. Charge controllers are continuing to improve with expected increasing lifetimes as well. The storage medium of choice is still lead acid batteries in many applications. Batteries require continuing care to provide lifetimes that are cost-effective. Measurements of the load of the gate system are proposed so that the energy needs of the systems can be compared with the potential generation and storage capability of the PV modules and battery. These measurements are of the current and voltage required for gate operation. In addition temperature measurements in the battery compartment are needed since extreme temperatures can be a major factor in decreasing battery life.

The approach will be to monitor system parameters and use the real-time data for analysis. In addition to parameters required for gate control, system diagnostic measurements will be recorded that include current, voltage, and environmental conditions such as temperature. Data will be collected to establish normal operating profiles for system operation in terms of these current, voltage, and temperature measurements. System profiles may be created in terms of upper and lower limits, simple nomograms, or algorithms to monitor system operation. Abnormal operating conditions can be recognized as deviations from this standard profile. This analysis can support a program of pro-active system maintenance to prevent or minimize system failures.

In summary, techniques will be developed and implemented in the control program to recognize and alert the system operator of impending problems. Using the results of the Reclamation/Sandia collaboration, the results of the real-time analysis, including the health of the automation system, will be displayed on web sites to alert canal managers of potential problems.

This process has already begun. For example, the status of the Sevier Valley/Piute automation system (see Fig. 5) is displayed on a web site (www.sevierriver.org) which collects data every hour. One of the parameters which is monitored is battery voltage (see Fig. 8). This provides important information on the state of the solar-energy system, and is thus used to anticipate problems. In the future, additional troubleshooting parameters will be added to the system (i.e., current draw).