At a cost of about Rs 15 crores per MW, solar PV developers will do well to ensure that they install some critical support systems to ensure that they get the most bang for the buck.
Of special focus for them should be monitoring systems. What are these monitoring systems, how do they work and what specific benefits do they provide to the solar power generator?
Solar PV Monitoring Systems Defined
What is PV Monitoring?
A PV monitoring system essentially involves
- Capturing the power plant/system performance indicators
- Analyzing the plant/system performance indicators
- Identifying the problems affecting the performance of the PV power plant
- Reconfiguring/Re-calibrating the plant as required, eliminating the performance bottleneck.
The first is done using sensors/meters and data loggers. Quite a few data loggers and inverters have the ability to export data and let the operators look at it visually over the web. However, when it comes to analyzing and identifying the problems, it is predominately manual. Reconfiguring based on the feedback is the last stage.
How does it work?
Principle: The output of a solar panel, essentially current and voltage, are stored in the memory of an inverter. These stored values are sent to a central control unit. Now using different means of communication channels like Ethernet, Internet, dial up access, GSM etc. the data is transmitted to a server from where alerts are status messages are sent to the users via SMS, email etc.
Thus, the core parameters measured are:
Grid (injected) current
Grid (injected) power
Apart from the above, the following are also measured and conveyed by the monitoring system:
- Module temperature
- Ambient temperature
- Solar radiation – (W/m2)
- Daily/monthly solar insolation – (J/m2)
- Wind speed
There are basically two types of monitoring.
1) Local monitoring
The most simple inverter check (monitoring) can be performed by reading values on display – display is part of almost each grid-connected inverter. Other possibilities of local monitoring includes monitoring by local PC via RS232 connection and/or remote display located in living room.
The parameters can usually be monitored, data logged and stored in inverter’s memory or external data logger for particular time (up to 1 year usually). Sometimes additional sensor related units (external or internal) are also required
2) Remote monitoring
Remote control and communication between inverters can be realized with RS485 connection or via grid (powerline connection). Distances up to 1200 m represents no problem, several tenth inverters can be connected in chain and monitored at the same time. For remote monitoring different ways of communication can be used: Ethernet, Internet, dial up access, GSM etc. The system can send alerts and status messages to the control center or user. Alerts and system messages can be send by SMS service, GSM, fax machine etc.
The sophisticated systems today that are used for remote monitoring can measure beyond just voltage and current – Module and ambient temperature, Solar radiation, wind speed etc.
Benefits of PV monitoring
The typical monitoring software that comes does a reasonable job of identifying the gross level under performance. But, plants can definitely benefit from more advanced monitoring solutions. Some benefits are
1) Able to see change in the performance and raise a flag before the problem actually happens.
2) Monitors not only performance of the plant but also the health of various components.
3) Helps the plant owners identify any warranty breach so that they can get compensation from the manufacturers.