Houseboat Solar

Re: Houseboat Solar

Fred,

This is how I would do the guesses... Lets say you have 10x 13 Circuline lamps and run them 5 hours a night:

• 10 x 13 watts * 5 hours = 650 watt*hours per night

Using the PV Watts program for Sacramento California, assume 0.52 derating (end to end efficiency from panel to AC power outlet). And in your case, assume that you will be using the boat during the six months of summer and will be mounting the panels flat to the roof (no way to point at sun consistently). Use 1kW (1,000 watts) of solar panel as nice round number (also smallest wattage allowed by program).

"Station Identification"
"City:","Sacramento"
"State:","California"
"Lat (deg N):", 38.52
"Long (deg W):", 121.50
"Elev (m): ", 8
"PV System Specifications"
"DC Rating:"," 1.0 kW"
"DC to AC Derate Factor:"," 0.520"
"AC Rating:"," 0.5 kW"
"Array Type: Fixed Tilt"
"Array Tilt:"," 0.0"
"Array Azimuth:","180.0"

"Energy Specifications"
"Cost of Electricity:","12.5 cents/kWh"

"Results"
"Month", "Solar Radiation (kWh/m^2/day)", "AC Energy (kWh)", "Energy Value ($)"
1, 1.87, 25, 3.12
2, 2.98, 39, 4.88
3, 4.28, 64, 8.00
4, 5.92, 85, 10.62
5, 7.20, 104, 13.00
6, 7.83, 108, 13.50
7, 7.88, 110, 13.75
8, 7.08, 99, 12.38
9, 5.75, 78, 9.75
10, 3.96, 55, 6.88
11, 2.33, 30, 3.75
12, 1.73, 22, 2.75
"Year", 4.91, 819, 102.38

For September, the lowest of 6 months worth of production, we get 78 kWhrs per month or 78/30=2.6 kWhrs per day. Assuming 650 WH per day needed:

• 650 Watt*Hours / 2,600 WH per 1,000 watt of panels = 250 watts of solar panel minimum (in September, you may need generator during bad weather)

To size the battery, we generally recommend 3 days of no sun and 50% maximum discharge--so, for a 12 volt system:

• 650 WH * 1/12v battery * 1/0.85 eff inverter * 3 days * 1/0.50 max discharge = 406 Amp*Hours @ 12 volts

Now, given that this is a house boat, has a generator, you are not there all of the time, and you may be limited in weight/space for a battery bank--dropping the bank down to 200 Amp*Hours would not be out of the question (you will have to watch charging to make sure you do not run the battery below 20% state of charge and get it recharged > 80% before storage)--Knowing your 1/2 sized bank will need to be replaced 2x+ as often as the larger bank.

Hardware wise--250 Watts of solar panels is not that much... MorningStar makes a wide range of PWM (cheaper) and MPPT type (more expensive) charge controllers. On the "high end", look at Morningstar SunSaver 15 Amp MPPT Solar Charge Controller. For a PWM controller, you probably need to look at a 25-30 amp minimum rated controller (MPPT does current limit so you can run at the limit without a problem).

Morning Star also has had a Dual Battery PWM charger for use with Starting and House battery systems.

If you want/need more solar panels, you can also look at the brand new Morning Star TriStar MPPT controllers (45 and 60 amp)... Very nice units.

You may also want to look at the Rogue MPPT controller too.

Xantrex also makes very nice larger MPPT controller and has very reliable PWM too.

The inverter is also an important choice for your system... Some really consume power (6-8 watts or more with no loads) and others have a standby mode where they run a pulse of 120 VAC every couple of seconds to see if there is an >8 watt 120 VAC load... For a smaller 12 volt system the TSW (True Sine Wave) MorningStar 300 watt/600 watt surge/12 volt inverter is a nice product.

If you have larger loads, some folks will put on a second, large and cheap MSW inverter (run a pump, microwave, etc.)--they do work for the most part--but if you can justify a TSW--I would high recommend one.

To monitor your battery bank--I really like to recommend a Battery Monitor. Victron Energy also makes a couple of battery monitors that a few people here have recommended too.

There are lots of FAQ's you can read (on PWM/MPPT controllers, Battery Banks, Inverters, etc...). Please let us know what more information you are looking for.

-Bill

Re: Houseboat Solar

I just took a guess at your needs---I have no idea if they are what you will really need...

For larger charge controllers, the Morning Star MPPT (45./60 amp) or Xantrex 60 Amp MPPT would be fine. Check the logging options... If you are into internet, the MS 60 amp includes an Internet Server.

You can put the panels in Parallel instead of series (depending on your battery bank voltage)--but in any case, if you are adding more panels, a larger controller will be required.

Charge Controllers--The Xantrex TC-2 series seems really nice (I like the Power Factor Correction if you are going to be using a small generator to bulk up your battery bank--PF correction reduces the AC current used by the battery charger--and allows a smaller generator to run a larger battery charger).

There is a larger Xantrex TC-2 charger, but it may be hard to get (call NAWS for more information). Iota is a very nice AC charger too (no PF correction or remote temperature sensor).

If you will be using dock power/genset a lot--you might want to look at a Inverter/Charger combination... Xantrex makes some very nice ones--Basically they act like a large UPS--Have an internal transfer switch/battery charger and when AC power goes away, they switch to an off-grid inverter.

-Bill