How do I connect a hybrid AC / DC solar air conditioner

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blue-sails asked Sep 5, '23

How do I connect a hybrid AC / DC solar air conditioner

How do I connect a hybrid AC / DC solar air conditioner?

Hello,

I am seeking out some design ideas with this post.

I have a hybrid 3.5-kWh solar air conditioner.

The solar air conditioner can either take up to 15-amps and 300 VDC, or it can take 11-amps at 220 VAC at 50-Hz, and it is currently connected to 6-305 watt Victron solar panels in series.

I have been thinking of purchasing a Multi RS solar inverter / charger and some lithium batteries to run the air conditioner at night.

I would like to connect the air conditioner in such a way that during daylight hours it can continue to be supplied directly from the solar panels since there are no energy conversion losses, and simultaneously if there is excess power, store the excess power in batteries; however, at night I would like to use the Multi RS’ built in inverter to supply it with AC power, and if possible I would like to supply it with DC power from the batteries.

My preference of priorities is to use:

1- direct solar energy from the solar panels during daylight hours

2- excess stored battery power

3- inverter AC power using the batteries

4- grid power

If I need additional power, I could add a second solar array or supply power from the grid.

One issue is that the Multi RS will work with a 48-VDC battery while the solar array feeding the air conditioner has a higher DC voltage.

Do to the different voltages involved, I would like to get some opinions on how best to connect the different components if possible.

Kind regards,

voltage orion dc-dc Multi RS ac aircondition

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matt1309 answered · Sep 05, 2023 at 02:07 PM

Hi @Blue sails

Yeh I agree AC is by far the easier setup given it's far more common.

DC route would be doable if you dont use a Multi RS and use separate MPPT plus multiplus/quattro. That way you could use the 48v power after the MPPT but before the inverter and use a Smart shunt as a DC power monitor to integrate the aircon usage into VRM.

The way you're currently describing I dont think will work at lesat not without issues (someone please correct me if I'm wrong here). But if I've understood correctly your plan is:

PV -> bus bar

Aircon <-> bus bar

multiRS <-> Bus bar.

I dont know the internals of the aircon however I imagine it has some form of charge controller built in. The MPPT charge controller will make adjustments to find the maximum power point, if there's a charge controller within the aircon unit this will then fight against the MPPT built into the mutiRS.

What you're essentially asking is can you parallel loads on the PV side. After a charge controller (battery side , 48V) you can but before I don't think it's possible or supported.

This forum post might help explain slightly different where they're asking if they can parallel 2 MPPT on PV side but i think the outcome would be the same.

Wiring 2 Victron Smart charge controllers in parallel on PV side | DIY Solar Power Forum (diysolarforum.com)

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blue-sails commented · Sep 06, 2023 at 06:12 AM

Could you please provide a rough sketch of these components and their connections on “…on the PV side. After a charge controller…”

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blue-sails commented · Sep 06, 2023 at 06:12 AM

I appreciate your input.

You are correct from what I have managed to read myself. I do, also, believe that the air conditioner does have some type of MPPT charge controller within it.

It seems based on the MPPT competition that you described that my original idea using the Multi RS would not work.

It’s a pity since this inverter checked a lot of my requirements.

Once again, thanks

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Modifications Space

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Answer 1 · 2023-09-05T07:06:23Z

seb71 answered · Sep 05, 2023 at 07:06 AM

The solar air conditioner can either take up to 15-amps and 300 VDC, or it can take 11-amps at 220 VAC at 50-Hz, and it is currently connected to 6-305 watt Victron solar panels connected in series.

I have been thinking of purchasing a Multi RS solar inverter / charger and some lithium batteries to run the air conditioner at night.

Keep it as it is. Power it from the grid during the night.

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blue-sails commented · Sep 05, 2023 at 08:55 AM

Hello,

“Keep it as it is. Power it from the grid during the night.”

Based on your response, can I assume that you do not think that the Multi RS will be a good match for the hybrid air conditioner?

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seb71 blue-sails commented · Sep 05, 2023 at 11:25 AM

It's not cost effective, if you have grid.

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blue-sails seb71 commented · Sep 05, 2023 at 11:30 AM

Assuming that it was cost effective, how could I connect the different components?

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seb71 blue-sails commented · Sep 05, 2023 at 11:39 AM

For consuming energy from batteries (during the night), Multi RS is not the best choice anyway.

Better option would be a Multiplus II (or a Quattro inverter) and MPPT charger(s).

Still, when you also add the battery, it gets quite expensive.

So still not cost effective.

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blue-sails seb71 commented · Sep 05, 2023 at 12:53 PM

I appreciate it. I will keep this in mind.

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blue-sails seb71 commented · Sep 21, 2023 at 06:00 AM

Hello,

I looked at costs, and the combined cost for solar panels, batteries, GFPD, boxes, cables, other smaller components, and the previously mentioned inverter would have a cost of about €0.143 per kWh which is lower than my current grid cost, and it excludes future price increases for grid electricity.

On a daily basis, once the batteries are full this should allow me to use sunshine energy during daylight hours.

At night and during the winter it would use stored energy.

Additional benefits:

If the grid fails, my air conditioner continues to work.
I can expand the existing solar array without purchasing additional solar chargers.
I can add a separate solar string of around 10-solar panels to the same system without adding additional chargers or inverters.
If I decide to supply energy to my house, I have an installed, running system.
I can add other lower cost air conditioners or resistive heating appliances without caring about competing MPPT.
Once it is time to replace air conditioner unit, the rest of the infrastructure can be used without additional changes. This will further reduce installation costs per kWh.

Possible problems:

I might need to ask for a solar permit since I am inverting solar energy; however, this particular inverter is unable to supply solar energy to the grid. So perhaps I might not need a permit.

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Answer 2 · 2023-09-05T11:43:01Z

matt1309 answered · Sep 05, 2023 at 11:43 AM

Hi @Blue sails

How does aircon get controlled/why is it hybrid?

If hybrid is just an additional feature, then you can achieve your goal using ESS system.

ie normal aircon on ESS would work as you describe. As would all loads ie

Loads are powered by solar, if insufficient power battery is used, if insufficient battery grid is used.

This is a common setup, the only difference with your question is the hybrid element. Happy to help more if you have some more info on your plans of wiring the hybrid element but wiring as normal AC aircon will achieve your required result with an ESS system setup.

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blue-sails commented · Sep 05, 2023 at 01:12 PM

Hello,

They call it hybrid since it can draw power using either direct current or alternating current. If there is insufficient DC power, then it draws the rest from AC, alternating current.

There are two different models of solar air conditioners. There is this hybrid air conditioner which requires between 100 to 300 VDC at no more than 15-amps, and there is an off-grid version which requires 48-VDC at more than 15-amps.

Currently, I am powering the air conditioner during daylight hours with solar panels connected in series. This is providing over 190 VDC at between 2.5 to 3-amps; however, I would like to power it at night as well.

One issue I have during daylight hours is that the amperage is relatively low on a sunny day with the solar panels.

If a small cloud passes over the solar panels, the air conditioner switches off the compressor, and blows air only with the fan. This situation remains until the amperage is sufficient to turn on the compressor again. The air conditioner unit has its own solid state hardware and software to decide on this.

Another issue is that in the winter as the days get shorter, I end up drawing a higher percentage of electricity from the grid.

Regarding the wiring, one option using ESS would be to feed the air conditioner on the AC (alternating current) side from the Multi RS.

On the DC side, the way I was thinking about it would be a common bus bar from which both the air conditioner and the Multi RS draw power. In this way, I thought the air conditioner could use solar electricity directly before inverting it by the Multi RS, but I don’t know if the Multi RS would soak up all the electricity before the air conditioner can get some of it, and I don’t know of other alternatives.

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Answer 3 · 2023-09-05T12:31:53Z

Michelle Konzack answered · Sep 05, 2023 at 12:31 PM

How many kWh dies the AirCondition need at night?

LiFePO4 batteries cost 3-4 times more the Lead-Acid batteries and with the energy you need, i would recomment to use something like SOPzS cells.

With 11A @230V I would suggest a MultiPlus-2 48/5000 which should work with the starting current of an AirCondition.

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blue-sails commented · Sep 05, 2023 at 01:10 PM

Hello,

It depends on the weather and the length of the night, and the season of the year. On average it should use around 550 watts per hour.

I am leaning towards the Lithium batteries since they can soak solar energy faster than lead acid based batteries. I need half as many of them, and I have a longer period of time before needing to replace them since they have about 10-times more cycles per kWh delivered.

I found a 200-amp battery at 51.2-VDC which should provide around 5,000 cycles, and I believe on most days would require no more than a 50% SOC drawdown.

However, it provides me with some flexibility on cloudy days.

Regarding the Multi RS, I chose it for four reasons. First, it will accept the full DC voltage of my solar array in the winter; second, it provides me with the option of adding a second solar array in the future as a backup system without feeding power back into the grid; third, it has an integrated charge controller which a Multiplus inverter lacks, and last it allows the possibility of adding one more solar panel to the current solar array without the need to change solar chargers.

Seven solar panels would be the maximum DC volts (300 VDC) that the air conditioner would accept in the winter as well as my current installation of breakers, GFPD, and load center box. This voltage is below the maximum that the Multi RS will handle; however, it is above the maximum of all other solar chargers controllers from Victron with the exception of the SmartSolar MPPT RS charge controller.

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blue-sails commented · Sep 21, 2023 at 06:08 AM

Hello,

I looked into issues with starting current. This should not be a problem with the Multi RS solar inverter since I am using a relatively efficient small capacity air conditioner.

However, if I should have an issue with starting current, I found a solution using a soft starter device:

https://www.microair.net/collections/easystart-soft-starters

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Answer 4 · 2023-12-19T17:24:17Z

Direct Solar Energy Utilization:
- Connect your solar panels to a charge controller to regulate the energy flow.
- Utilize a Maximum Power Point Tracking (MPPT) charge controller to efficiently manage the solar panel's voltage and current output.
- Directly connect the solar panels to the air conditioner during daylight hours to benefit from direct solar energy without energy conversion losses.
Excess Power Storage in Batteries:
- Use the Multi RS solar inverter/charger alongside lithium batteries to store excess solar energy efficiently.
- Ensure the Multi RS inverter is compatible with your battery's voltage, which is 48VDC. Use a DC-DC converter if necessary to match the voltage.
Night-Time Operation with Battery Power:
- During the night, rely on the stored energy in the lithium batteries to power the air conditioner.
- Use the built-in inverter of the Multi RS to convert stored DC power from the batteries into AC power for the air conditioner.
Managing Multiple Power Sources:
- Set up the system with a priority-based power supply: prioritize solar panel energy during the day, followed by battery power, and then inverter AC power using batteries.
- Consider implementing a smart energy management system or controller to automate the switching between power sources based on your specified priorities.
Voltage Compatibility and System Integration:
- Address the voltage mismatch by using a compatible DC-DC converter to regulate the voltage from the solar array to match the 48VDC battery system.
- Consult with a certified electrician or solar energy specialist to ensure the safe integration of components and compliance with electrical standards.
Scalability and Additional Power Options:
- Plan for scalability by leaving room for additional solar panels or grid power integration if needed.
- Implement monitoring systems to track power flow, energy generation, and consumption for better system optimization.

Remember, it's essential to ensure proper safety measures and compliance with local regulations when configuring and connecting electrical components. Seeking guidance from a certified professional or solar system installer will provide valuable insights for an efficient and safe setup.

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