Off-grid system review

[Hilltopsolar]

CoD,

I would love to find out more about your area and how you are moving forward with construction. I will PM you soon. (need 1 more post to PM)

We are developing a 2000 sq.ft. home at an off-grid location in Hawaii. Due to the fact that most of the solar systems in Hawaii are grid-tie, our solar subcontractor does not have a terrible amount of experience with 100% off-grid systems utilizing batteries and a generator. I would be grateful for a little input on your end:

The system:

30 SolarWorld SW 280 mono panels
Outback GS 8048A inverter
16 Rolls S550 batteries (20.5 Kwh)
1 Generac 10kw generator

The house will have electric appliances (range, oven, dish-washer, laundry and dryer). We recognize this is not ideal, but plan on using these appliances mostly during the day-time (we are located on the dry side of the island with heaps of sunshine) and staggered (not running everything at once). Nevertheless, we will still probably use about 10Kwh of juice at night (dish-washer, tv, lights, etc.).

My main concern is the generator. I would like a system that supports the batteries anytime the load is at a certain level or if the batteries reach a certain point of depletion. Not sure if the Generac is ideal for this... Also, does the Outback GS 8048A include generator support? Or would we be better served with a different inverter.

Your input is greatly appreciated.

[Sunking]

Per the spec sheet, its draw is 1.5 kW.

http://www.lenntech.com/grundfos/CRN...-G-V-HQQV.html

If the motor is 100% efficient, yours is 84.2%, then 1 hp = 747 watts. Which means your pump is (1500 watts / 747) x .842 = 1.7 horsepower.

[Cult of Dionysus]

3 hp pump for 4 to 6 hours use daily is not 6 to 8 kwhs, it is around 8 to 14 kwhs. just make sure you understand this. well you can do this on the sun hours with extra panels.

Per the spec sheet, its draw is 1.5 kW.

http://www.lenntech.com/grundfos/CRN01/96516527/CRN-1-27-A-P-G-V-HQQV.html

[paulcheung]

I have to power a 3 hp Grundfos pump for 4-6 hours a day. That alone can use between 6 and 8 kWhs. We also have a full-sized fridge, dishwasher (2 loads per day), front load washing machine (2 loads a day), 65" tv (3-4 hours a day), led lights, computers, etc.

Gonna check with the guy who put in that crazy Aquion system who has been posting here. He said he has a Honda EU7000 (though he's waiting for the auto-start system to become available). Same island.

3 hp pump for 4 to 6 hours use daily is not 6 to 8 kwhs, it is around 8 to 14 kwhs. just make sure you understand this. well you can do this on the sun hours with extra panels.

[Cult of Dionysus]

Also, with my 12k gallon water tanks, I could avoid running the water pump for more than two weeks (assuming 600g a day of use). So if there's a terrible few days of weather, which happens like once or twice each winter, I could reduce my daily power consumption down to 6-8 kWh in a pinch, if necessary.

[paulcheung]

If what the Smart Carbon Technology from Trojan is true PSOC. It is a plus as every day 100 % SOC is not practical with Solar charging. I would recommend Trojan in this case.

[Sunking]

Rolls ship from Canada.

Nova Scotia but I get the point.

[Amy@altE]

In today's economics I do not recommend Rolls. If you were to hire me as your engineer I would have you consider Trojan IND29-4V a 4 volt 1600 AH battery with a 36/96 warranty. It is another solid 5 to 7 year US made battery at $18K vs say a comparable Rolls series 5000 2KS33P a 2 volt 1640 AH cell at $22.6K. That is some serious cash savings for like products.

Rolls ship from Canada. I checked their shipping calculator, they don't include HI, so you'd need to get a custom shipping quote.

Good point about the Trojans. Another plus for them is they are typically a 1-2 week lead time, as opposed to Roll's 6-8 weeks. Not a deal breaker if you plan for it, just another data point.

[Willy T]

Rolls is a Brittish made product

Rolls Batteries

" Surrette Battery Company is one of North America's leading lead-acid battery manufacturers. Established in 1935, with a production facility in Salem, Massachusetts, Surrette relocated to Canada in 1959 and is the Nation’s only remaining independent battery manufacturer.

At their ISO registered production facilities in Springhill, Nova Scotia, Surrette manufactures a full range of Rolls batteries for railroad, marine, motive power and renewable energy applications. With complete distribution throughout North America, and customers around the World, Surrette batteries are considered the best and toughest for the specific markets they serve. "

[Sunking]

http://www.hawaiienergyconnection.co...iiSolarMap.jpg

Fall within the 6.4 zone (though this is annual average, not winter average).

For off grid you design on worse case month, not a yearly or season average. Use an average and you go dark or run on generator.

[Sunking]

But earlier you had said that (not calling you out, just trying to find clarity on this point):

ou can go as low as 80% DOD in a pinch. The thing with batteries when you look Discharge vs Cycle Life you are looking at accelerated lab test in a controlled environment under computer control with as many as 5 to 10 cycles in a day. Fact is all batteries have a Calender Life whether you use them or not. When the warranty ends is when the Calendar life Ends.

So when you look at those cycle vc DOD charts first look at the warranty. Example 24/60 is 5 years or roughly 2000 cycles. Now look at the chart and find where the DOD meets 2000 cycles. That will tell you how far you can go, but I did not tell you that.

Right I said in a pinch you can go as low as 80%, but that is not a design goal.

The 6-CS-25P are Series 5000 batteries with a 36/120 month warranty.

That tells you are looking at a 5 to 7 year battery which is roughly 2000 cycles. But that in no means you want to discharge 80% DOD every day. Just one cloudy day without a generator means you have to go dark for at least 1 full day of sunshine to recharge. Even at 50% DOD means a full day to recharge without a generator. Minimum design goal 5 day reserve capacity giving you 2.5 to 4 cloudy days.

In today's economics I do not recommend Rolls. If you were to hire me as your engineer I would have you consider Trojan IND29-4V a 4 volt 1600 AH battery with a 36/96 warranty. It is another solid 5 to 7 year US made battery at $18K vs say a comparable Rolls series 5000 2KS33P a 2 volt 1640 AH cell at $22.6K. That is some serious cash savings for like products. Trojan is much easier to make a warranty claim in the USA as Rolls is a Brittish made product.

Shipping is another huge cost factor to Hawaii. Which is less shipping from the mainland USA or England?

[Willy T]

Remember that the Rolls / Surrettes batteries and especially the 6CS25P's are Industrial Batteries. Study up on their requirements for charging and maintenance. Commission them properly and do not expect any consistency for the first 100 cycles, in their SG level and Capacity. It takes the first full cycle ( 50% dod ) break in period to finish forming the plates.

Good Battery that will give you many years of service.

[Cult of Dionysus]

What are you doing to use that much power in Hawaii? Arc welding hobby?

One thought on using the Honda as an autostart generator is that both the LP and the auto start are a hack. Who is going to fix it when it breaks? Even though you may never use the generator, I suggest you answer the repair question before picking a brand.

One possibility is to have the generator installed by the good local generator guy. It's only an on/off interface to the charge controller (plus electrical). There's not going to be any value in calling your solar sub when the engine won't start.

I still think the Honda may be the way to go, especially with your big and expensive battery system. If you bought the Generac for off grid you would have a controller that would do monthly testing, which is an advantage. But the hardware is not as well designed and made as the Honda. With the generac and similar you would typically have a service contract and the unit would report monthly to the installer with who you would have a service contract.

You seem to be spending money to insure trouble free electrical service. Part of that equation is service.

I have to power a 3 hp Grundfos pump for 4-6 hours a day. That alone can use between 6 and 8 kWhs. We also have a full-sized fridge, dishwasher (2 loads per day), front load washing machine (2 loads a day), 65" tv (3-4 hours a day), led lights, computers, etc.

Gonna check with the guy who put in that crazy Aquion system who has been posting here. He said he has a Honda EU7000 (though he's waiting for the auto-start system to become available). Same island.

[Cult of Dionysus]

Personally, I'd go with the 6-CS-25Ps, but not at 80% DoD. Still plan on a lower DoD, and you'll get an even better life out of them.

I'd also upgrade to the Mate3 instead of Mate2. Your installer can order the FP2 from Outback with the upgraded Mate, or just switch it out himself if he already has the FP2 in stock. MUCH more user friendly and has remote monitoring capabilities with their new OpticsRE capability.

Thanks. Even at 50% DoD, these batteries will deliver more than the S-1660s. Plus they package a lot better for the space restrictions that I have.

Will push for the Mate 3 as you suggested.

[Cult of Dionysus]

You need to find a better map as that says you get 2 Sun Hours.

http://www.hawaiienergyconnection.com/wp-content/uploads/manual/galleries/sunHours/images/sun-hawaiiSolarMap.jpg

Fall within the 6.4 zone (though this is annual average, not winter average).