Solar power system

Greetings all,

I bought a Lunar Stellar 2010 and would like to add air conditioning powered by a generator. I live in the UAE, a hot country, and want to know the best option for the system, including the battery and installation.

Welcome to the forum You really need to speak to a mobile aircon  engineer in your country as  Aircons are region specific i.e in Europe which is colder than the UAE  the maximum ambient they will work in is lower than in the UAE . So you will need one specific to your region, as to powering it off solar power  you will need to to know the power draw of the aircon unit first  then determine what total wattage of solar you need  and  hence the battery back up ( with an inverter to convert the low D.C voltage upto 230V for the Aircon unit)

Be aware that most air conditioners or any appliance with a motor will have a much higher starting current than when its running. For instance the Truma unit in the UK has a running consumption of around 4.5A at 240 volts but has a startup surge of 28A for 160ms (according to its specification)

Dometic also produce caravan aircon units which specify a fuse of 10A in the supply line which implies a max current of around 8-10A with a running load of around 4.5A

What ever you decide to power it with must have the capability of supplying the starting surge for at least 2-3 seconds otherwise you risk damaging the appliance or the power source.

Running a generator for prolonged periods may drive you nuts but is probably a better idea than solar and you could probably get away with something around 3kw although you should ask advice from your chosen air-con manufacturer.

Bear in mind that, even in the UAE,  night times are 10- 12 hours long so you need battery capacity to run the aircon for a minimum of 12 hours together with a solar set up capable of running the a/c all day plus recharging the batteries after they've been depleted overnight

Just doing some simple sums, say you need 5A for 24 hours = 120A at 240 volts = 28.8kWh. Your solar power needs to generate at least that in the 12 hours or less that the sun shines = around 2.5-3kW.

Your batteries need to be able to deliver around 14-15kWh overnight (assuming that the aircon runs continuously). 15kWh at 12v implies a battery size of around 1250a/h without taking all sorts of inefficiencies in inverter and power conversion. Dont forget other stuff as well, like lighting, water pumps, fridge*, water heater* and anything else that requires electrical power.

*Fridge and water heater usually need a 12v supply even if you do run them on gas.

As lead acid batteries shouldn't be discharged below 50% you can double that, whereas LiFePO 4 batteries would probably be more appropriate as they can be discharged to a much lower level although the cost could be quite prohibitive.

Even if you assume that the a/c only runs for 50% of the time you will require a pretty substantial solar and battery set up to keep it running overnight and it would be a good idea to choose batteries that are specifically suited to a high charge/discharge cycling regime to get maximum life out of them.

What about good diesel generator