Off grid cooling- Daytime only- Solar Mini-Splits or Propylene glycol.

[SolarCasa]

I am redesigning the off grid solar power system for an ocean front home I am renovating in the lower Baja.

I would like to use the solar power during the day only to cool the home.
I am cooling from about 80 degrees F and 70% humidty.
I would like to get down to 70 degrees F.


I have two ideas:


1. Bank of solar panels with an MPPT charge controller into 4-12v batteries with a 48v dc to 220v ac inverter to power minisplits during the day
The batteries are only being used as buffers to handle large current surges.

2. Bank of solar panels with an MPPT charge controller into 4-12v batteries with a 48v dc to 120v ac inverter to refrigeration units which chill propylene glycol solution which would be circulated to heat exchangers in rooms as needed. Again, the batteries are only being used as buffers to handle current surges.



Anyone been creative with this off grid need?

[solar pete]

I am redesigning the off grid solar power system for an ocean front home I am renovating in the lower Baja.

I would like to use the solar power during the day only to cool the home.
I am cooling from about 80 degrees F and 70% humidty.
I would like to get down to 70 degrees F.


I have two ideas:


1. Bank of solar panels with an MPPT charge controller into 4-12v batteries with a 48v dc to 220v ac inverter to power minisplits during the day
The batteries are only being used as buffers to handle large current surges.

2. Bank of solar panels with an MPPT charge controller into 4-12v batteries with a 48v dc to 120v ac inverter to refrigeration units which chill propylene glycol solution which would be circulated to heat exchangers in rooms as needed. Again, the batteries are only being used as buffers to handle current surges.



Anyone been creative with this off grid need?

Hello SolarCasa and welcome to Solar Panel Talk.

Sounds like you have a lot of reading to do. There are some good stickies in the off-grid section. First thing you HAVE to do if your serious about designing a successful off-grid solar system is a get a handle on how many kWh (kilowatt hours) the system needs to supply each day and how many days automation (days where it can supply power with little sun light to charge the batteries) and allow for a genny to charge batterys in an emergancy or you can use a genny to make the solar system smaller and use the genny to run large loads. Opinions do vary, cheers.

[SolarCasa]

This is just an additional system.

I am not looking to use batteries to power the A/C.
I only want to have A/C when the sun is shining.

The basic system that is there currently uses two sets of solar panels attached to two separate outback MTTP charge controllers in 16 Rolls 6v batteries with an Outback Hub and Mate and two Outback inverters backed up with a Kohler 10kw propane generator.

I have a Generac 3.8kw gasoline generator as a backup when I take the solar system off line.

One set of solar panels has been blown away by hurricanes and the other has 6 250 watt "evergreen" panels in series.
Obviously I am revamping this system- The batteries are shot and will be replaced.
This is system is independent of the AC system I am designing.


The Mini splits are easy to implement but may waste a lot of available solar.

The beauty of the glycol system us that I can use all the solar power and time shift the cooling.
It is not commercially available and would take some major design.

[bcroe]

I understand that the batteries are to stabilize the system, not to power it. In
that case the amount of cooling available will depend on the sun. You will need
a good control system to avoid much Depth Of Discharge, thereby greatly
extending the battery life (or allowing use of smaller ones).

If you really want to do "some major design", find out the internal power scheme
of variable speed compressor units. If running from rectified DC, you might
develop a way to power them direct from the PV/battery voltage. Then tell me
how you did it. Of course the warrantee is lost. Bruce Roe