Monitoring solar PV output
Introduction Monitoring of your solar PV output is useful to see the actual outputs. This can be measured from the inverter and/or mains using current clamps or pulse meters using a standalone monitoring tool or a roll your own system. It can be performed manually by reading inverter logs and updating information to the internet or fully automated. These slides show an overview of different methods of provisioning logging including fully automated logging to the internet using the Aurora 5000 inverter as an example. There will be variations required for other inverters but the same concepts apply.
Monitoring Options Solution Description Advantages Disadvantages Comments Using a stand alone energy monitoring device such as the EW4009 This logs both PV output and grid power, logs data and displays in realtime on a remote (from the sensors) wireless display. Easy to install, inexpensive to buy. Current clamps are not accurate and pick up stray current. Must be installed by an electrician. Easiest and a cost effective solution for most people. Standalone inverter monitoring. Logs inverter activity via a serial or wireless You can see exactly what the inverter is communications interface. Displayed via software producing and any alarms. Excellent to a local PC. accuracy of inverter outputs. Requires networking know how to make it work properly. Only considers PV production, not power consumption. For those who want to know what the inverter is doing. Only shows PV output. Inverter monitoring uploaded to PV Output on the internet. Logs inverter activity via a serial or wireless communications interface. Displayed via PV Output vias the internet. As above. With the advantage of having your monitoring available via any web enabled device. As above. Requires a server device configured to collect and forward data to the internet. Requires configuration of software. As above with the flexibility of access via any web enabled device anywhere, anytime. Full power monitoring via the internet. Logs both production and consumption using meters across PV output and grid and calculates net position. Most precise method and captures the most information. Easiest to configure requiring only a wifi connection to automate. Information available on any web enabled device. Cost - this is the most expensive option. The gold plated solution. Is somewhat less expensive if current clamps are used but this sacrifices precision. Configuration of PV Output is optional but highly recommended.
Overview Standalone monitoring is an out of the box solution that s easy to deploy and configure. Its mentioned here for completeness but won t be discussed at length. Full monitoring of mains and PV is a topic discussed in detail at a later point. Direct inverter monitoring is potentially complex: To monitor the inverter directly the following is required: Understanding the inverter communications options; ie, bluetooth, usb, serial communications protocol of some sort, wireless, either wifi or bluetooth Making a connection to a collection device which might be a smart phone, tablet or PC and appropriate software Configuring the software to communicate Optional uploading to PVOutput.org (automated or manual)
Standalone Monitoring This is the simplest and most cost effective solution. Two current clamps and transmitters are provided and these are installed by an electrician in the meter box - one on the PV out, one on the grid. The receiver is then configured with tariff costs and information is displayed in real time. Data is logged and can be recalled using a PC. Logged data is very coarse, analysis capability very basic. Current clamps are not precise as they will pick up stray current in the meterbox leading to erroneous readings.
Inverter Communications Your inverter may have one or more of the following: usb Serial db9 Serial connector (RS232) RJ45 (RS485 connection) Wireless Bluetooth Wifi The available output determines the connection required to the collection device. Serial software conversion (virtual comms port) will be required for serial connections and must be configured on the collection device. You will need to acquire the appropriate cable and/or serial converter hardware and/or software. For wireless, a tablet or smartphone might be used as well with appropriate software.
Inverter Communications Connection for monitoring will vary according to your inverter but principles are the same. Using the Aurora inverter as an example: Connection is made via the RS485 output to a wifi enabled serial adapter This is connected wirelessly to a collection device (PC, win7) The collection device records continuously and updates via the internet to PVOutput.org.
Inverter Communications For the Aurora inverter serial communications is via twisted pair wires to the serial adapter. The serial adapter also has an db9 connection for RS232 communication which is not required in this case. This transmits the data via wifi to the local network. The existing internet connection on the LAN is used for uploading data to PVOutput. This was in the end a fairly simple solution but required some trial and error to find all the bits and configuration that would work reliably together.
Inverter Communications The collection device is the home theater PC (Win7) which is on 24/7. This means the inverter is continuously monitored. On this device: Wired ethernet connection to the LAN and internet Software for: creating the virtual comms port and enabling serial communications between the devices monitoring the inverter logging the serial data forwarding the logs to PVOutput.org
Inverter Communications Aurora Monitor is used to log the data from the inverter and forward to PV Output. This was the simplest approach considering the available options. It also provides live monitoring and could be used on its own if you didn t want to upload to PVOutput.org.
Flukso and Pulse meters Flukso is an open source hardware project that offers a versatile, well engineered and built monitoring solution. It connects to a wide array of monitoring sensors including current clamps and pulse meters and is provided with its own website for logging and displaying data. It is simple to configure and only requires wifi access for communications. Data can be displayed in PV Output. Pulse meters (or current clamps) are installed by an electrician in the meter box. It makes sense to use pulse meters with this device rather than current clamps for the accuracy. Configuration is simple and the device manages its network connection and uploading of data. This is the best solution at a cost.
PVOutput.org This is a free web based service that is used for displaying, comparing and analysing inverter logs. For displaying inverter logs, setup is very simple and can be: fully automated manual by capturing the data to a CSV file and uploading periodically directly into the PVOutput gui. This provides a good view of production. Tariff information can be added and this then provides basic analysis capability as shown below.
PVOutput.org When configured using the Fluksometer as the data source the additional outputs are automatically aggregated by PVOutput and give realtime readings of your actual energy use and costs as shown below. This is the most precise method of capturing and displaying information. Very good information is available on power usage patterns and the effect of your PV system and consumption habits on energy cost in real time. This is the gold plated solution but is well worth the cost and effort.
PVOutput.org For performing comprehensive analysis such as energy produced vs power used additional sensors and configuration is required such as a Fluksometer and current clamps or preferably pulse meters for mains and PV.
References PVOutput user guide Serial to wifi converter Flukso Fluksometer installation Software for solar inverters PV Beancounter PVOutput without Flukso PVOutput with Flukso