Planning 14.4 kw system w/ 24 2v Surrette and PV & integrate 15 kw diesel

2 Posts
Feb 1, 2007 10:23 pm
Planning 14.4 kw system w/ 24 2v Surrette and PV & integrate 15 kw diesel

We have a remote summer fishing lodge in Canada currently using 15 kw diesel on a 24/7 basis. It is often working at 100% capacity. We want to install an inverter, battery and PV system to cut fuel & emmisions. As a fly-in every drum of diesel costs double once we haul it by float plane.

1/ Some folks have reccommended the most bang for the buck might be to get the system without any PV panels and that would allow us to cut the generator run time and keep the cost lowest. Any comments on this?

2/  My generator guy who is now also into alternative power has given me a number of options on configuration. The latest configuration he suggests is one OBPS4 VFX3648Q 14.4 Outback Power Center, 3 MX60 MPPT Charge Controllers, 24 Surrette 2V 2KS-33PS 2491 Ahr@100 hr rate Cells and 30 Sharp 165 watt panels plus the combiner boxes, breakers, mounts and cables. In studying all this over the last year, I understand that it is best to stick to 1 string of cells as opposed to multiple strings. I am leanning towards moving up to the 24 of the 2YS-31PS 3426 Ahr Cells instead to get the additional 37% battery capacity. Any body have pricing on 24 of these batteries and do I need 3 of the MX60's?

3/  Also, I see at the altenergystore.com online store that the OBPS4 VFX3648Q has a bunch of optional add ons. What do I want or need? For example an Amp hour meter or one of the other options?

4/  I don't see lightening arrestors listed by my guy. What do I want?

5/  I'm in a very short rot season @ 52.5 degrees Latitude so can I save the money on PV mounts and use treated wood bolted to my steel roof? I understand a need to maintain at least 3" of space for venting / cooling. I also will build the roof to the optimal pitch and face due south.

6/  What total wattage of panels do I want for the 15kw setup? At 21.6 kw my guy had 72 x 150 w = 10,800 watts and now he specified 30 x 165 w = 4950 watt for the 14.4 kw. Based on the ratio he used for the 21.6, I calculate that I should be 7200 watts @ 14.4 kw inverter sizing. I am confused and based on the reccomendation of completely skipping the PV panels, I guess that all this really only changes my fuel consumption by either increasing or decreasing the amount of power from PV. Yes/No?

Any help you folks can offer will be greatly appreciated. I am a jack of all trades and master of none so I do know a little about many things but alt energy is one that I'm only learning.

Thanks,  Tom Metzner www.bullmoosecamp.com   
 
 
351 Posts
Feb 3, 2007 05:15 pm
Re: Planning 14.4 kw system w/ 24 2v Surrette and PV & integrate 15 kw diesel

Tom:

1) Running batteries with a generator may not save you any money. It is all dependent on the loads you see. If you are running the genset with moderate to heavy loads 24/7, having the batteries won’t really do anything for you.
To save money, you need to be running the genset for hours at low load (say during late night/early morning). Then the batteries can carry the loads during the low use hours and be charged up during moderate load periods. 
You also have to look at where your high load periods fall.  You may have to delay the battery charging to avoid the highest load periods. Otherwise, the charging may put you into a longer 100 percent capacity period and you could be forced to cut other loads to support the charging.  So, you might not save fuel or emissions with this option. In the worst case scenario, because of inefficiencies, you might actually increase your total fuel burn.

2) You should be looking at C20 rates, not C100.  What you are calling a 2391 AH battery is 1766 AH at the C20 rate.  So your entire bank of batteries is 3532 AH with 1766 AH usable. 1766 AH at 24V is 42.384kWh.  I think that your guy actually planned to use about 20kWh to keep the batteries above the 75% state of charge. (Ask him)

If that is the case, I would recommend against the larger batteries.  They are about 285 lbs apiece as compared to the 200 lb and they are about $100 more, each. There is a tremendous difference in trying to lift a 285 lb battery in and out of an airplane, as compared to 200 lbs. And if they are charging by the pound, it adds up to 2040lbs more for shipping.

You need at least 3 of the MX 60’s, and that is cutting corners a bit. You have 4950watts of panels or 206 amps at 24 volts. The 3 MX60s are good for 180amps or 4320watts. Personally, I would use 4 of them. I do not like the idea of losing up to 624 watts of generation at peak sun. This could be up to 2.5kwh per day.
I would also discuss this issue with your guy to find out what his logic is.

3) The remote monitoring system is a great convenience, but not a necessity. Many of the other meters etc are bought by people that do not get the monitoring system. 

4) Lightning is not real common in my area.  We consider lightning arresters to be a waste of money. How much lightning do you have ? Do you use arrestor systems on your buildings ? If not, I don’t think I would worry much about them.  If you do use protection on your buildings, then you probably want arrestors for your system.

5) I do not like roof mounts. That is the worst place for them IMHO. But sometimes, particularly in built up areas, you are forced to put them there.
Put the panels and racks on the ground. That way you can clean them easier. The cleaner they are, the more power they will produce.  If you get snow, it is real easy to sweep them off. Ground mounting also facilitates adjustable racks.  Rack adjustment could increase your output and save fuel over non-adjustable racks.
You don’t fall off the roof (easy to do on a 50plus degree metal roof) nor do you damage the roof by walking on it.

6) You are focusing on kw which is a rate of energy (or peak flow). You need to look at Kwh which is a quantity of energy. Your 14.4kw system will handle flows of 14.4kw at periods of peak flow. Your battery bank is sized based upon the quantity of electricity that is expected to be used, expressed in kwh.
As an example: lets say that there are 10 hours at night where you use an average of 2kw an hour. That is 20kWh to be supplied by your batteries.  At 24vdc that would be about 833AH.  That’s about 23 percent of the suggested battery bank.
With the 4950 watts of PV panels (and 4 MX 60s), it will take about 4.04 hours of full sun to replace the 20,000 Wh (20kWh).

This way you have eliminated 10 hours of fuel for the genset at night (probably about 20 gallons of diesel), the panels recharge the batteries during the day, and you have very little, if any, load on the genset for charging batteries.

My final comment would be what about energy conservation measures to conserve fuel, lower the peak demand and reduce overall energy consumption.  How much have you done ?  My experience is that energy conservation is always cheaper than generation.  Proper energy conservation steps could also reduce the size and cost of the PV system that you are planning. 

Hope this helps,
Ken
 
2 Posts
Feb 3, 2007 06:07 pm
Re: Planning 14.4 kw system w/ 24 2v Surrette and PV & integrate 15 kw diesel

Thanks for the detailed answers Ken!

1/ My fuel consumption runs at 4 x 55 drums every 10 days during the busy season and only 3 x 55 gallon drums in 10 days (my oil change frequency) during the time when we have few people and lower temps in the fall. The ammeters run at 60+ amps each when it's bogging and often at 15 and 20 while not much is going on. We do have some stuff to possibly improve efficiency, however in the world of competing for customers, any gains i make are wiped out by guests bringing coffee makers, microwaves and other such stuff. Ultimately, people want and expect more comfort in the vacation environment so yes, we can go to more efficient DC pumps in place of the AC ones we now have and since my fridges and freezers are 12 years old and newer, I might save some there too... but unless I can figure out a way for breakers to pop when people plug stuff in, they'll find a receptacle somewhere.

2/ I don't have any problem with the 300# weight of a cell since over a summer we unload about 100 55 gallon drums of gasoline and diesel. They run 380 to 400 pounds with the gas in heavier drums and fuel oil in thin ones. At the other end they load with a chunk of roller wheel conveyor and more guys but at our end it's down hill to the dock via a ramp. At camp we have big carts and now even a Kubota R310 wheel loader with bucket or forks and ability to lift a 1200# pallet. It was disassembled and slung in by chopper in 2000. The bigger batteries at only $100 more and much more capacity are still likely a better value regardless of the 50 cents a pound it costs for the floatplane charter. My generators have 20,000 and 5000 hours on them (both 1998) and the likelihood is we'll sell one and buy a new more efficient tier 2 emission 25 kw to run as the primary in another year.
I appreciate the heads up on the MX60s too!

4/ Lightening is frequent and we have a 140 foot communication tower right in camp. It doesn't get hit often and everything is well grounded both at the tower and around camp. Nothing currently has arrestors and we've never lost a radio phone or anything else since the tower went up in 1985.
5/ Great point on the roof mount issue! I'll opt for an off ground station at waist level to eliminate weed issues and mower shrapnel and keep myself safe on Terra firma.

6/ based on my ammeters over a typical day I'd say we likely average 12000 watts most days and 4000 watts at night though since it's never been metered, I'm only guessing. The fuel burn of 4 drums in 10 days equals 220 gallons in 240 hours or a gallon an hour. The cooler and less busy times its more like 3/4 of a gallon average.

I'm still not sure what I'm doing but will keep studying.

Again, thanks a bunch!

Tom


 
1 Posts
Feb 4, 2007 09:37 am
Re: Planning 14.4 kw system w/ 24 2v Surrette and PV & integrate 15 kw diesel

Hey, was in here reading this and am looking forward to gaining some advice from you guys. I run a resort off the grid and operate with an 80kw, have been wanting to look into alt. energy, as running these generators arent getting cheaper. 1st prob. is we dont get sun in the winter ( so no solar) but we do have a creek, (pretty good size) and am looking for advice about a possible water turbine that would be set in the creek for water to pass through. Any advice would be great. Jason Cataldo
jasoncataldo @ hotmail.com
 
351 Posts
Feb 4, 2007 01:26 pm
Re: Planning 14.4 kw system w/ 24 2v Surrette and PV & integrate 15 kw diesel

Jason:

You need to give us a description of the creek.

Describe the following for the low flow condition (summer).
How wide and deep. How fast does it flow ?  How much water would you estimate (gallons or cubic feet per minute or second)?
How much head is there (How many vertical feet from where you are thinking about setting the turbine to the high point on your property)?


Ken
« Last Edit: Feb 4, 2007 01:32 pm by ken hall »
 
2 Posts
Apr 7, 2007 06:13 pm
Re: Planning 14.4 kw system w/ 24 2v Surrette and PV & integrate 15 kw diesel

why dont you try a air to water/ energy system.
take a look at a2wh.com.
 
Apr 8, 2007 05:31 am
Re: Planning 14.4 kw system w/ 24 2v Surrette and PV & integrate 15 kw diesel

You say that 15kW genset runs 100% - 24/7?
I will start with that.
15000 X 24 = 360000
360000 / 48 = 7500
7500 X 5 = 37500
Now let me explain what all that is.
15000 = 15 kW gentset at 100%
24 hours a day
360000 watt hours a day or 360 kWh's
48 volts dc nominal
7500 amphours minimum battery storage
37500 recommended amphour battery storage. To help keep the batteries in a shallow cycle to extend there overall lifetime, make the minimum 7500 amphours 20% of the total capcity of a battery bank.

Now to replace that with PV modules.
I will have to assume an average number of hours of equivalent full rated charge from a PV module per day of 4 hours.
360000 / 4 = 90000
Now let me explain that.
360 kWh's
4 hours of equivalent full rated charge per 24 hour period
90,000 watt PV array at 48 volts nominal

Oh! One more thing.
90000 X 5 = 450000
Now let me explain that.
90000 watt PV array
5 dollars per rated watt of PV
450000 dollars
I haven't even gotten into all the other costs yet. The batteries the inverters the electrical..... I will spare you though because I think you understand the simple math behind sizing a PV battery charging system now. Oh! I was being liberal with that 4 hours of full rated charge from a PV module and conservative with the $5 per rated watt for PV. As with all other things in this life, your mileage my vary!
 

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