Seeking Houseboat Off Grid Solar System design

[Bill C]

Want to convert a 75'x18' houseboat to an off grid solar/battery system. Usage estimate is less that 5 kWh per day (4 ton A/C, two 25 cubit ft refrigerator/freezers, chest freezer, range, microwave, dishwasher, trash compactor, washer/dryer, multiple TVs). Dreaming of a large array and 20-30+ kWh battery bank. Boat has a 20 kW gas genset that could be used for backup on cloudy days. Located on a large fresh water lake in the western US.

Looking for someone to design a system for me. Any referrals or recommendations?

 

[AnarchyJet]

Is the genset 120 or 240 volts? Are there any DC loads or is everything AC? What you want could easily be $30-$40k installed, is that within the budget?

 

[LakeHouse]

Usage estimate is less that 5 kWh per day (4 ton A/C, two 25 cubit ft refrigerator/freezers, chest freezer, range, microwave, dishwasher, trash compactor, washer/dryer, multiple TVs).

I think you are way, way underestimating your usage. 5kWh will run that ac unit for about 75 minutes or so, and then you've used your entire day's worth of energy. OR you could run the dryer for an hour or so. OR you could run the two fridges and chest freezer for the entire day (an average of 200W over 24 hours is about 5kWh).
I'm not trying to say that running the houseboat off of solar is impossible, but you should start with a more realistic estimate of your actual power needs. The resource section has a great tool for an energy audit here.
The biggest limitation you're likely to run up against on a houseboat is real estate for panels. In my experience there isn't usually a huge amount of top deck space that isn't used for something already, but your particular case may be different.

 

[SparkyGage]

...
The biggest limitation you're likely to run up against on a houseboat is real estate for panels. In my experience there isn't usually a huge amount of top deck space that isn't used for something already, but your particular case may be different.

Looking at the logistics of fitting it, I'm wondering about that too. Most of the panels I've looked at are between 16-22wt per SqFt. so if you have a 75x18 boat that's a 1350SqFt rectangle. If you can cover 75% as a combination upper canopy and using the front deck cover, that gives you roughly 1000SqFt (and roughly 3000lbs of panels and mounts). So at 20wt per SqFt you have 20kwt potential under ideal conditions. A boat that size should be able to handle the weight just fine (we used to park two SeaDoos on the roof of our 60x14 back in the day). I doubt you could cover more than 75% without making it look like a WWI aircraft carrier.

So this is what I think is reasonably possible (and required) with panels on the market from my spreadsheet that I'm using for my roof. I'll let some other folks with more experience with outputs comment on how many KWh you could expect.

If it was me, I would focus on a battery system first before doing the panel install. I'd want to know what I can (and can't) run together. That AC and the dryer are your two biggest loads as I'm sure they are both likly 220 50A circuits. Your solar panels will give you what they can give you, but that battery bank and charge/inverter is where all that power is living - and thats a LOT of power. You could put 4 4.8KWh batteries in a rack in a closet about the foot print of your stacked washer/dryer.

All that said, I'm just some guy on the internet. These are all the things that I would want to discuss with a pro if I'm looking at doing a $30-60k of modifications to my boat. Looking forward to seeing how it works out! (Well I'm hoping)

 

[Skypower]

Those roof mount residential condensers that they put on those houseboats are typically noisy energy hogs. A newer inverter type would be a great investment and reduce your energy consumption by half. Another option is to additionally install small mini splits for the staterooms so you only cool down the sleeping areas at night as needed. MarinAir unit's are perhaps another option but they are more costly usually require through hull screened intakes and that means a haul out $$. Even with a lot of panels, it still may still be a loosing battle, so I’d plan 45 to 90 kWh worth of batteries and charge them up at 75% of the generator’s rated capacity to be efficient and to limit the run time and noise. That might be for a few hours every three days or so.

 

[Bill C]

Is the genset 120 or 240 volts? Are there any DC loads or is everything AC? What you want could easily be $30-$40k installed, is that within the budget?

240 volt genset. Everything is AC. Yes that is within budget.

 

[Bill C]

I think you are way, way underestimating your usage. 5kWh will run that ac unit for about 75 minutes or so, and then you've used your entire day's worth of energy. OR you could run the dryer for an hour or so. OR you could run the two fridges and chest freezer for the entire day (an average of 200W over 24 hours is about 5kWh).
I'm not trying to say that running the houseboat off of solar is impossible, but you should start with a more realistic estimate of your actual power needs. The resource section has a great tool for an energy audit here.
The biggest limitation you're likely to run up against on a houseboat is real estate for panels. In my experience there isn't usually a huge amount of top deck space that isn't used for something already, but your particular case may be different.

My bad. I meant under 5kW per hour on average, not per day.

 

[Bill C]

Those roof mount residential condensers that they put on those houseboats are typically noisy energy hogs. A newer inverter type would be a great investment and reduce your energy consumption by half. Another option is to additionally install small mini splits for the staterooms so you only cool down the sleeping areas at night as needed. MarinAir unit's are perhaps another option but they are more costly usually require through hull screened intakes and that means a haul out $$. Even with a lot of panels, it still may still be a loosing battle, so I’d plan 45 to 90 kWh worth of batteries and charge them up at 75% of the generator’s rated capacity to be efficient and to limit the run time and noise. That might be for a few hours every three days or so.

Agreed. I am planning to change out the residential condenser for a soft start/variable speed marine (water cooled) unit in the hull (frees up deck space too).

 

[Skypower]

Agreed. I am planning to change out the residential condenser for a soft start/variable speed marine (water cooled) unit in the hull (frees up deck space too).

Do be warned that water cooled type has some things that you must be aware of. The thru hull MUST be a screened! Preferably with mesh 3/16 to 1/4” diameter holes. You will then need a valve, quality strainer$$ and the recommended pump. The aforementioned. Must be below water line because the pump is NOT self priming. A flow switch should be installed to prevent the system from damage if the system is clogged. In winter the water flowing out is cold and if it stops flowing the heat exchanger can freeze and crack! The only other problem is people keep telling me the my bilge pump is running and have to thank them and explain the it’s the air conditioning LOL. Do install or make sure your bilge water alarm is working. It is after all another hole in the boat.

 

[chrisski]

For a 50 kWh daily power requirement where that 5 kW/h you mentioned for 10 hours, I estimate you need 20 kW of panels, or 110 square meters. If you can site these correctly, then as low as 10 kW of Panels, or 55 square meters. I do think my numbers on square meters are lower than you need. I use 180 watts per meter squared as a realistic estimate of how much a panel is rated. Paying top dollar for the best panesl available will not bring the real estate required down very much.

I think the best you can realistically hope for with real estate available is power some systems that don't take a lot of power or to build a system to power a couple hours a day.

 

[LakeHouse]

My bad. I meant under 5kW per hour on average, not per day.

Ah, I see. That’s a common unit confusion: It wouldn’t be 5 kW per hour, just 5 kW. As in: average usage is 5kW.
If you used 5kW (kW are a measure of power, or energy per unit time) for one hour, that would require 5kWh of energy (kWh are a measure of energy, which what batteries store).

Anyway, 5kW is a lot of power.