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GridFree Technology - Frequently Asked Questions

GridFree Microinverters (AC micro inverters) - Frequently Asked Questions


See the information published at EV-POWER.EU:


Study the support sections at the GWL/Blog:




1. - How can be a source of electric energy directly connected to grid (household 230V socket)? Isn't that dangerous?

For a limited amount of time, the GridFree installation can be connected as a testing installation using one or two MicroInverters directly into the AC 230V grid socket (along with device that consumes the energy supplied from the solar panels).

The MicroInverter includes a protection technology which constantly checks the voltage. In case the 230V grid goes down, the microinverter disconnects immediately.

For larger and permanent installation we recommend to make a professional installation including additional protection devices such as circuit breakers, surge protectors and current relays.

See also at GWL/Blog:




2. - How is possible that the energy from MicroInverter is preferred over the energy from the standard Grid?

This is the natural quality of the electric energy. Electricity prefers to be taken (consumed) from the nearest source first. Additionally the MicroInverter constantly manages the voltage of the Grid. The output voltage of the microinverter is always set slightly higher to ensure it will be used by your device first. Perfect frequency and phase matching is always ensured. These parameters of the grid-tied micro-inverter are certificated by the European directive EN, DIN and tested by TÜV and VDE.

See also at GWL/Blog:




3. - What is the output of the GridFree microinverter? Is it sine or other waveform?

The GridFree solar microinverter works only in harmony with the AC 230V grid. It follows the grid waveform. The grid must by high quality sine form AC grid. The microinverter will not work with a poor quality grid.

See more at GWL/Blog:




4. - What is the actual power consumption of the MicroInverter?

During the energy generation the micro inverter runs at around 95% efficiency. This means with powering by 240Wp panel at the peak sun intensity, the power consumption of MicroInverter is about 12W. To make the MicroInverter running it is necessary to generate at least 20W power by panel. Without any power to be generated, MicroInverter turns into a stand-by mode with maintaining of monitoring of AC Grid voltage. The average stand-by mode consumption is about 0.2W per Inverter. The stand-by mode can be turned off simply by disconnecting the inverter from the AC Grid.

See more at GWL/Blog:




5. - Can the MicroInverter work in a completely stand-alone installation (Off-Grid)?

No, the MicroInverters are grid-tied inverters designed as on-grid (grid-tied). That is why they will work only with AC 230V grid connected. If you disconnect the grid, the MicroInverter shuts down immediately. This function is mandatory to comply with the EU regulations.

Follow more for the Micro-Inverter safety and operation FAQs:

  • Q: Can the Micro-Inverter work in off-grid mode (island mode)?
  • Q: How will the Micro-Inverter behave when the grid is down?
  • Q: What will the Micro-Inverter do when there is short circuit on the AC power line?
  • Q: The grid utility company in my country does not allow to connect any solar products tied with grid. They require full galvanic separation. What to do?
    http://gwl-power.tumblr.com/post/37583550069/




6. - Can you make a microinverter unit for me that will work in an off-grid mode? I need only 200W, when the sun is shining. This would be very good solution for me. When sun is shining I have 230V/200W when there is no sun, there is nothing. I will pay to you some more money if you unlock the unit to work in off-grid mode.

The grid-tied and off-grid inverters are completely who types of products. The grid-tied inverter follows AC power wave from the grid, so their design is simple, because they do not need to modulate the 50Hz frequency. The off-grid inverters need to modulate the sine wave to make the 230V AC by themselves. Simply said, there is no easy way for the grid-tied inverter to become the off-grid inverter. That is why the GridFree MicroInverters can operate only with the AC grid and cannot change to off-grid mode.

Additionally consider that the sunshine is not a stable power source. When clouds pass through the sky, the energy will drop bellow the 200W of the panels. This is why you need some battery in the off-grid system to make the stable energy source for the operation of the inverter and the attached equipment.




7. - Can I use your microinverter to charge the batteries? I plan this setup: the solar panel will be connected to the microinverter; the microinverter will power the 230V battery charger; the battery charger will store the energy in the batteries. This way I can use the 230V charger for the battery I already have. What do you think?

What you plan is a kind of an off-grid installation. Note that the MicroInverters do not work without the grid. They must be connected to the grid to start the operation. They follow (or harmonize) with the grid for operation. There is no way to make the inverters work without the AC grid of good quality.

Hint: for charging batteries, we suggest to use the MPPT chargers (regulators). They work directly with DC (from solar panels) to DC (to battery).

Follow more for the Micro-Inverter safety and operation FAQs:




8. - Why do you recommend using large size 290Wp to 310Wp panel with MicroInverter that has maximum power of 230W (250W) AC?

The power rating of a solar panel in the datasheet (e.g. 260Wp or 310Wp) is considered as "Watt peak". This power is available only in perfect conditions (sunshine 1000W/m2). For majority of locations such ideal condition is available only a few days during year. Most of the year, the sunshine intensity is much lower. To utilize the MicroInverter to full potential it is better to use larger panels. MicroInverter is using MPPT technology and thus utilizes maximal power from solar panels.

Tip: During winter it is possible to connect two or three solar panels to maintain power generation through MicroInverter.




9A. - Is it possible to combine the MicroInverter with batteries to provide energy during night?

Yes! By using the MPPT solar regulators you can charge the battery with energy from solar panels. To gain the energy from the battery pack (24V) you can connect the battery output to the MicroInverter. This way you can use the energy stored in the batteries in moments without sunshine.




9B. - Can I charge the battery (from a solar panel) during the sunny day and use this battery to power the GridFree micro inverter in the evening to produce 230VAC? In other words can the micro inverter operate from a battery source?

Yes, the GridFree micro inverter supports the battery operation. When connected to battery the micro inverter will work at maximum power (i.e. 250W) and provide the energy to the grid. This way the inverters can be used as energy storage solution. However please note that the function of the microinverter will stay as grid-tied inverter, even though it is powered from the battery. The inverter must be connected to the grid and it will work only when the grid is on and the quality of the grid meets the EN50438 requirements.

See examples for the energy storage solutions at the GWL/Power Blog. Check examples of model installations.




10. - The nominal output power on the microinverter is 250W. Is it possible to reduce the power to lower value, e.g. 100W?

There is no way to reduce the power rating inside the inverter. The inverter always works at full power according to the power of the DC supply provided. When connecting solar panels you can reduce the power by connecting a smaller size solar panel or panels. See an example of the regulation at our GWL/Blog:


Note: when using the microinverter with a battery, the micro inverter will always work at full power. There is no way to regulate the power of the microinverter.




11. - How exactly is the microinverter connected to the 230 V AC grid systems? From the different images or demos shown I can only see proprietary special plugs.

Please follow the support at GWL/Blog:




12. - I have an off-Grid (autonomous) 6kW array with a 3000W inverter. How can I connect the MicroInverters into this system?

The MicroInverters are only working with the regular AC grid. They will not work with the local off-Grid (autonomous) system. Please follow the support at GWL/Blog:

  • Question: Can the micro-inverter (in the GridFree installation) work in an island mode against some sine wave DC/AC generator? (e.g. in parallel with my own independent 230V island system)?
    http://gwl-power.tumblr.com/post/92902308866/




13. - I have tested the inverter in my home. It works fine and generates electricity perfectly. When I bring the same installation to my brother in the village the inverter does not work. What is the problem?

Most likely the quality of the grid at you brother’s place in the village is not good enough to allow for the microinverter operation. The usual problem of villages is the low voltage (much less than 230V) or unstable voltage with some signal noises that prevent from the inverter operation. The microinverter must follow the regulations for the grid quality and they are not allowed to start working when the quality of the grid is poor.

For your application (in the countryside) you may wish to change to a fully off-grid system rather than using the GridFree with MicroInverters.




14. - Should I inform my Grid Operator (Energy billing company) about my GridFree installation?

Do you inform your Grid Operator when you reduce your consumption from the Grid, for example when changing from normal light-bulbs to more efficient LED-bulbs? No!

So there is no legal need to inform the Grid operator about your self consumption GridFree installation.

When the Micro-Inverters are operated in the Grid-Free type of installation, all energy generated by the micro-inverter(s) will be used directly at the place and no energy will be provided to the grid. In this type of GridFree installation, there is no need for the user to inform or consult with the Grid operator.




15. - Is it necessary for the microinverter to comply with the Regulation VDE-AR-N4105?

If you are using the microinverter in the GridFree installation (for 100% self-consumption) the compliance with VDE-AR-N4105 is not needed. The GridFree installation means that all energy from MicroInverters is consumed locally and there is no overflow of energy from MicroInverters to the public grid.

From the point of view of the Grid operator, the GridFree installation does not exist. So there is nothing to regulate as required by VDE-AR-N4105.

See also more details at the GWL/Blog:




16. - Do your MicroInverters work without gateway?

Yes, each microinverter works fully independently. There is no need to buy the central gateway. (Some manufacturers offer inverters or solar optimizers that work only with the main unit). This is not the case with GWL inverters.




17. - What is the function of the eGate? Do you recommend using it?

The eGate is useful for the installations of larger solar systems, where you with to have additional protection and full monitoring of each microinverter. The eGate collects data and sends the data to the central system – SEDAS (operated by the microinverter supplier).




18. - What is the wiring of the MicroInverters? How to make the real connection of the system?




19. - Is it possible to have my electric energy meter go in the opposite way to decrease the amount of energy on the display?




20. - Remember: the production and consumption must be on the same phase!

In 3 phase systems, for your GridFree installation it is necessary to have the production (solar panels with MicroInverters) and the consumption connected on the same phase (wiring section).

In order to benefit from the GridFree self energy generation, we suggest to connect most of the equipment with continuous consumption on the wiring of the same phase.




21. - What happens when the consumption is lower then production from solar panels?

The energy in amount of difference between higher production and lower consumption will overflow to public grid. You have to avoid to this situation if you have no deal about this supporting with your grid operator or low in your country not allows these overflows.

The best and save way how to protect from overflows to the public grid is current monitoring relay




22. - Where is the best to use the GridFree?

In all cases of permanent consumption which has each house (200W - 300W) to cover this consuption or in cases with consuption through the day like basen filtering/heating, ventilation, dehumidifying, air-condation, etc.
It is also suitable to use in companies to cover consumption of servers or other permanent running appliences through the day.





Do you want to know more?

Check the overview of the GridFree-related information

Do you have more questions?

Be sure to let us know. Just use the form bellow to contact us.

 
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