New solar project - 1KW

[markguthrie]

I am just starting to plan a solar project. I am looking to generate enough power to store for overnight use of a air 10k air conditioner, frig, ice maker. I figure I will need about a kilowatt of solar.

I'm planning to either replace my bimini with a rigid top or build a frame and is above the bimini.

I'm working with a company who does this kind of word, but would like to get opinions and ideas from the group. Including batteries, panels, inverter, etc.

This is a start from scratch project.

Next year I am planning to spend a lot of time on the hook and would rather not be running a generator all night. Will probably run the genny daily to top off the batteries, cool the entire boat (4 AC units), and for cooking if needed.

Vessel: Navigator 53'

Thanks for any ideas.

Mark
St Pete, FL

[Wood]

My first concern starting a similar project was what wind loads will the frame and panel fastenment withstand. Everything else fell into place. Unlikely you'll run a 10,000 btu AC for any length of time without a very robust battery system.

ETA - You might wander over to Setsail.com and see what the Dashew's did when they incorporated AC into their battery system.

[skipmac]

Have you done the math on this?

First, a single, typical 110V AC, 10kBTU air conditioner will draw more or less 8 amps when the compressor is running. Assume a 50% duty cycle that will draw about 10 kW hours per day. 1 kW of solar panels on a really good day might charge 6-7 kW hours. So just running one air conditioner you are already way below what you will need in solar panels to replace the charge in the batteries used in a day.

[Wood]

^^^
Add 10% efficiency loss through inverter plus other demands and you're way over 1000AH useable battery capacity at 12v. Air conditioning is a non-starter.

[mako]

Actually skipmac, you just confirmed that his system would work. OP says he just wants to run the aircon at night, which would be about 5kW-hr. Roughly.

OP, do you have the budget to remove that 10k btu aircon and replace with a DC unit? They are much more efficient and that would give you some more buffer.

[barnakiel]

Making the project, decide if you want to allow for the days when the sun is not at 100% its capacity.


Solar capacity drops off quite rapidly when the days get cloudy, foggy or otherwise imperfect. So you want to to answer "what then" for yourself before full commit to the details.


b.

[skipmac]

Originally Posted by makobuilders

Actually skipmac, you just confirmed that his system would work. OP says he just wants to run the aircon at night, which would be about 5kW-hr. Roughly.

OP, do you have the budget to remove that 10k btu aircon and replace with a DC unit? They are much more efficient and that would give you some more buffer.

First, note that I said on a really good day. That also ignores any other loads like fridge, lights, etc. And as mentioned by Wood, efficiency losses and, depending on what kind of battery system, losses in charging.

[joelhemington]

Note: a quality solar panel will lose 20% output in extremely hot weather (90 degrees plus) So even if you have a bright sunny day, don't expect 1,000 watts. Under sail you'll have convection which will mitigate that loss and you won't need A/C as long as you can keep the hatches open. Parallel wire (10 awg) each panel separately so any shading on one won't deplete the rest. This means an MMPT for each panel (cha ching) 1,000 watts of solar should give you a consistent 33 Amp Hours of power per day. Do use LIFPo batteries (another cha ching) as they take a charge much more efficiently and can be safely drawn down to less than 50% charge. In cooler weather, when the panels don't produce as much, you may not need A/C. Get a handle on your Amp hour requirements before designing this system and don't forget about the frig/freezer, nav lights, AIS and autopilot when figuring this number. I suspect that you'll end up needing a 2K solar array with a 2k Lithium bank to do what you're intending.

[Wood]

Originally Posted by joelhemington

<snip>Parallel wire (10 awg) each panel separately so any shading on one won't deplete the rest. This means an MMPT for each panel (cha ching) 1,000 watts of solar should give you a consistent 33 Amp Hours of power per day.<snip>

My design for each 350w panel @ 40' round trip calls for 8 gauge.
I think you meant 330AH.

[joelhemington]

Yep, you're right 330 Amp hours. The no. 10 wire was suggested to control voltage drop, never hurts to go larger if it will fit your lugs.

[Tillsbury]

I seem to remember the o'kellys channel describing solar requirements, and suggesting that the breakpoint for happily using aircon at anchor was around 2000-2500W solar panels. 1kW is going to be very squeaky and doesn't allow you much room for error if any.