NRGDivert to Battery
Category: Development
Development redirecting to inverter with CUMon
Logs Offline !
The CUMon Logs have been taken off line whilst the new Energy diverter is developed.
Development Notes
The current software that has been developed with CUMon measures Current magnitude and does not need to worry about the current phase because it determines export and imports by cross-correlating the PV amplitude with the Grid Connection amplitude.
Inverters and CT coils
Inverters use CT coils or Modbus meters on their Grid Connections to determine the power flow to or from the the Grid
CT Coils can only measure current amplitude. You do not know the phase angle of that current . To measure whether the current is flowing in or out of your house you need a Voltage value to combine with the Amplitude value from the CT coil. With Normal Grid AC to an inverter you can combine the CT Amplitude with a Voltage reading to calculate this.
With CUMon we work with a CT coil that just requires to be clipped into the Grid AC connection and the orientation of the CT coil is not needed to be known because the Current flow is determined by the Cross Correlation to the PV current.
We have chosen an inverter that has a Modbus meter replacement option that allows an NRGDivert module to mimic the Modbus meter and control how the inverter perceives the virtual “Grid connection” and thus control whether power is diverted to battery or to house/Grid.
Progress so far
- We have successfully interfaced with Modus on the Inverter and have been able to control the Flow of power in and Out
- We have used a very basic control loop to divert energy to the battery
- We have supplied the house with power from the battery
Notes
- The inverter can be set in Charge the battery mode or charge Or power the House Mode
- The MODBUS meter supplies a varied interface with lots of data available but the Inverter only seems to read the bare minimum 3 registers of Reactive power
Problems
- We have to emulate reactive power and this is currently unknown by CUMon
- We have a control loop that is basic and gets lost easily
- The inverter “remembers” the power output state and continues to drive this even if the control loop fails
Conclusion
The process is possible and the concept has been proven with an engineering setup. The Control loop needs work but is feasible
Not a Complete Waste !
So if you have been watching our Logs for the last month you might be concerned that the NRGDivert has Stopped or failed ! well the problem was the our Hosting service provider changed servers on us and replaced the server software with a different package. This caused massive failure of the logging.Logs between the 24th or April and 2nd of June were Broken and should be ignored. We hopefully have resolved this now so from the 2nd of June Logs are good again. We appologise for any confusion and misdirections.
The Logs are left in place for Recording Keeping purposes Only.
The development changing the logging has resulted in a faster and more secure and robust logging process.
Get your free energy diverter
Starting in March 2024 we are giving away to the first 5 applicates that meet the criteria and ask to join a full NRGDivert setup
This system was developed to divert excess PV electrical power to a local energy sink rather than exporting it back to the grid. The original test bed setup is being enhanced by adding Solar battery storage and the excess energy use case will therefore change. We will continue to support this system but without a suitable test bed we cannot show/prove it continues to work. So you will need to agree to performing as an anonymous test bed and have a suitable setup to qualify.
Comment below if you are interested.
Energy Diversion to a Battery
What is needed to Divert usable energy to a Battery ?
Assuming that the Voltage of the Battery is 48V. We need at least this voltage to Charge it.
If we are going to use make domestic use of this Battery power we will need an inverter.
Scope of this Development
The scope of diverting energy from an existing Solar PV setup to a Battery and making use of that energy is daunting ! Being at the scale of a full PV System just without the actual Panels. So we are left with the practical problem of how much of a Home Generation system we need to duplicate !
Possible approaches
- Use NRGDivert to create a 48v Compatible Charger for the Battery
- Find Component subsystems to Interface CUMon to and then program them.
- ??
Arguments and Reasoning
Regarding 1 above the simplest approach is to transform the diverted power,rectify and stabilise it.This works to fill the Battery however does not then provide a solution to make use of this power. The problem of providing the energy back into a domestic environment is that this is constrained by a plethora of regulations any Niche-tec system would have to comply with.
In the case of 2 above we would need standalone systems to work as our subsystems.
So we are looking to energy divert using a Hybrid inverter. This will ensure the existing PV system remains inviolate and allow the add on system to be stand alone. This perhaps marginalises the usabilitiy of the system for other developers.
Development Description
The aim of the development therefore is to emulate a CT (Current Transformer sensor) to interface back to a hybrid inverter and that way control the charge and discharge of the battery on the new inverter. This emulation to be completely digital by emulation of the RS485 Modbus Protocol.
This limits the scope of the development to a manageable and achievable goal. Removes the Legal/regulation conformity and produces a system that diverts Excess Solar into a Battery. Furthermore a WIFI CT RS485 Device could find other applications.
NRGDivert Non Intrusive energy diversion
Home solar installations generate power allowing your home to use what power you can and any excess is exported back to the grid. if you don’t have any way to store this electricity and can’t make use of it, then it is exported back to the grid at a low nominal rate.
Making use of that energy yourself is usually the most cost benefit to you.
There are many reasons you may not want to change your electrical setup to upgrade your system to make better use of the energy.
There is a way to determine how much spare electricity you are generating CUMon does that function and logs your consumption over time allowing you to identify when you are exporting and how much energy you could be using. CUMon requires no actual wiring changes to your house. Providing you can identify the wire that connects you to the Grid and the one returning to your Consumer unit from your inverter you can wrap a current sensor around it. So CUMon requires no electrical rewiring. Just Clamping the sensors around wires is truly non Intrusive. This can be performed by anyone !
CUMon connects to your home WIFI and broadcasts this information within your home network.
What is non intrusive energy diverting.
Non intrusive Energy Diverting energy diverting is when the signal from CUMon is detected and acted upon by a device.
Current developments
We have NRGDivert Boards that can turn on driving power to devices within your home. They are experimental but they work we trying to identify the final form of these.
They currently they fit behind an existing 3 pin socket and proportionally turn on or off.
Example testbed is an 13A Immersion heater that heats hot water allowing the energy to be stored in the hotwater tank these could be used with any resistive load that can handle being Switched On and Off.
Or take the form of an ESP-01S Board that works in a switch on when spare current exceeds a preset value and switch off when it drops below
Future Development Aims
We wish to expand on the functionality of the NRGDivert to send that energy to a House Battery.
How can I get involed
We are looking for test beds to add to the CUMon logging and welcome fellow developers to put your CUMon logs online and will make available the broadcast message format for home users that wish to participate and control their own energy usage.
We have spare prototype boards for CUMon users wishing to build their own NRGDiverter we offer these free while they last and will charge remake costs for future ones when we have to reorder so get in early if you want a free NRGDivert PCB
CUMonitor as Canbus Controller
So the aim is to create a zero export controller using CUMonitor.
To interface with the Invertor a device is required to connect to the CAN bus.
From a previous investigation for Badger we established that using a daughter board with the CUMonitor is a viable way to interact with the CAN Bus.
So establishing control of the inverter should be possible using similar hardware.
The good part is that no existing wiring will need to be changed and adding the control will only require low voltage CAN bus connections.
One problem is that the inverter is mounted in the roof space and that the Can bus controller will need direct access to the inverter
CUMonitor as a Zero Export technique
What does a Zero export Controller do and can we replace it with a CUMon ?
A zero export controller balances the energy from the Inverter and Battery with that consumed within the house. By ensuring that non of that energy is sent to the Grid. It proves that it has achieved this by measuring the current to the grid and finding it zero.
CUMon already uses the two current sensors to read PV current generated and the Exported Current. It then makes a prediction of whether the system is exporting to the Grid. To get it to function as a Zero export controller it needs to exert control over the inverter.
This should be possible using control on the RS485 or CAN bus. Most modern inverters have the export monitoring and control as an option built in.
CUMon offers the advantage that there is no rewiring of Mains Power and it is attached purely by using current clamps of existing cables
To get control of the inverter would require connecting to the CAN bus inputs and acting as a grid export current sensor.
This is definitely worth considering as there is no mains voltage involved it should prove a safe option for energy divertion
Daves CUMonitor gets an NRGDiverter
Dave’s been running with an CUMonitor for a while now and wanted to investigate driving his underfloor heating using a NRGDivert. On the 15th of May one was installed after some testing we found that the underfloor heater only consumed about 1.4 Amps when fully on. After further investigations we found out that the under floor heating was controlled by WIFI already and the only convenient place to install the NRGDiverter was before the WIFI underfloor heating controller. This meant that the high speed switching of the supply could damage the WIFI switch. So A 100% on/off mode was added to NRGDivert.
And the WIFI Switch was controlled by a 3rd party App consequently this NRGDiverter was controlling nothing .
CUMonitor Testing for Badger on RS485
We received and inquiry from the owner of a solar installation Nick Name “Badger” that has a wiring setup where the inverter has been wired to the consumer unit board using a 3 core cable that presents no opportunity to use a current clamp without cutting into the cable. Also there is no ready supply near the consumer unit.
So we have resolved to add Modbus functionality to read the current directly from the inverter using RS485. The functionality on the Inverter allows this.
Testing Results are here in the badger folder.
We are also trialing Dual logging with second CUMonitor configured to record additional analog traces