- Created: Tuesday, 13 March 2018 10:30
- Written by Akash H
Zero Feed - The Why
In India many states experience frequent and crippling power cuts. Solar rooftop systems are springing up everywhere, from small residential houses to large factories in attempt to save costs and in so doing reduce carbon emissions. Many states have not modified their policies yet to allow feed in, which in turn means that all solar generation needs to be used within the premises. This is fine when the installed capacity is much less than the average load, but when a larger solar plant is installed problems can and will occur when loads are less in peak solar hours and during weekends.
Zero Feed - The How
A power meter is installed at the incomer of the building, and is used as a reference to determine the active power load on the building. This meter needs to be able to communicate with Modbus RTU. The Wattmon device is connected to both the power meter and the inverters. It will regularly poll the power meter to determine the active power. As it reaches a threshold value that can be set by the user, it will ramp down the output power on the inverters using power control commands on Modbus RTU. This will effectively limit the amount of generation dynamically so that exporting of power does not happen.
DG Protection - The Why
Diesel generators bridge the gap during power cuts and in some locations they are used 24/7. When coupled with solar grid tie inverters, a saving of fuel can be achieved. However, it is important to balance the amount of solar power generated so as not to trip the genset, which effectively means you need to maintain a certain minimum load on the generator at all times.
DG Protection - The How
A power meter is installed on the output of the genset, and connected to the Wattmon in the same way as with zero feed. The Wattmon monitors the energy generated and if it drops below a set point, it will reduce the power of the inverters so as to ensure that the generator does not trip.
Both these systems can be installed at the same site by using two power meters and some software customization which will allow the set points to vary based on whether grid energy is available or whether the system is running on the generator.
For more details on our system, please contact us.
We are going to be at Intersolar Munich (May 31-June 2) and look forward to meeting you all there at stall B3.472!
We will be showcasing our two existing products, the WattmonPRO and WattmonMINI and launching our newest product, the WattmonMEGA.
The new Sync package in Wattmon allows multiple global variables to be synced between different devices in a virtual cluster. This opens up endless possibilities for distributed control based on data spanning large geographic areas. Devices can be configured to read or write multiple variables.
Zero Feed In
India does not allow grid feed in certain areas, and any energy fed into the grid is charged to the customer. Using WattmonPRO with the Sync package, it is possible to monitor the main incomer power meter with one Wattmon and transmit this data to the cloud and sync it to various rooftop grid tie setups across the campus. At user-definable intervals each Wattmon will receive the total energy being imported/exported and decide on the correct power limit for the inverters, either throttling or increasing production to ensure that all generated energy only goes to the campus and does not get fed back to the grid.
Another application could be to enforce global setting changes across multiple locations in situations where a large number of devices are deployed. For example, a street light controller’s switching time may need to be adjusted remotely and it would be impractical to connect to each controller manually.
How it works
Wattmon devices poll the sync.wattmon.com server periodically for updates to read variables using a unique cluster read key. It can read all variables or a selection. These variables are then updated into the Wattmon’s $_GLOBALS array making it accessible to the scripting language and actions. Additionally, a global sync array is created which also keeps track of the last update to the variable so the device can determine whether the data is current or not.
For write variable, the Sync package takes the values of the global variables and sends them to the server at fixed intervals using a unique write key.
The MAC address of each device is logged on the server, making it easy to debug the system.
The Sync API will be available in the 2.15 release of WattmonOS.