Author Topic: OFF GRID POWER; various thoughts on...  (Read 465402 times)

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Offline glenn kangiser

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Re: OFF GRID POWER; various thoughts on...
« Reply #150 on: March 23, 2009, 06:50:31 AM »
I have to use the generator every so often in long storms in winter so it is a bit of a problem unless you are way overbuilt.

Our wind generator really helped during this storm - it took over so no need to run the generator.
« Last Edit: March 23, 2009, 07:30:36 PM by glenn kangiser »
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Re: OFF GRID POWER; various thoughts on...
« Reply #151 on: March 23, 2009, 07:40:37 AM »
That's the balance. If you can generate enough power through the winter you're probably way overbuilt for summer, but then you run the generator which you want to avoid.

At some point I would like to have some wind generation, but right now I think it would be cheaper to just hook up another four panels to the array. My wife thinks I should stop thinking about it so much and look at the fact that we ran the generator for about ten hours all winter, and around four hours of that was necessary to charge and then equalize the batteries.

Maybe she has a point.

Offline MountainDon

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Re: OFF GRID POWER; various thoughts on...
« Reply #152 on: March 23, 2009, 09:24:42 AM »
If that's all the genny had to run, and if things are working well you're probably okay. Your wife may be right; time to leave well enough alone.
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Re: OFF GRID POWER; various thoughts on...
« Reply #153 on: March 23, 2009, 09:27:00 AM »
Yeah, you're both probably right, Don.

Offline glenn kangiser

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Re: OFF GRID POWER; various thoughts on...
« Reply #154 on: April 08, 2009, 09:24:29 PM »
Recovering the batteries.... not a fast process but it is working.  I find that the fastest improvement is gained from the controlled equalizing and again the critical point seems to be about 31.8 on 24v or 15.9 on the 12v system.  That seems to be where we come back to after going to around 32v or 16v for equalizing voltage. 

Per a tip on a charger site I have gone to equalizing with the constant voltage (wire feed) function of my DC generator welder. 

The rewards?  These are 3 year old Trojan L16's valued at around $3000 and once they are fully recovered I think they will be usable for another 10 years if I keep the desulfators running on the system and charge health sufficient most of the time and good.  Stuff does happen though - extended storms - pumping during cloudy days - things that need watching but don't always get it.

Changing to a Grundfos SQFlex pump could help a lot also.

Xtreme says even average batteries have enough material in them to go 10 years.  Keeping enough water in them is key to good life also - as they get older they need more - as they equalize monitor them and don't allow water to go below the top of  plates.

The Xtreme recovery charger (list around $800) seems to be helping also but the equalization with the welder was necessary to help it along on these big batteries.  Not allowing overheating is necessary.  The voltage rise to 16 or 32 with plenty of water over the plates is necessary for a speedier recovery.  Sulfation is almost not seen on the plates now but I don't want to overdo the recovery with the welder.  I monitor with a voltmeter as I do the equalization. 
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Offline Pritch

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Re: OFF GRID POWER; various thoughts on...
« Reply #155 on: April 08, 2009, 10:41:59 PM »
Glenn,

Is the cost of all this battery rehab going to be offset by their added life? 

--Pritch
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Offline glenn kangiser

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Re: OFF GRID POWER; various thoughts on...
« Reply #156 on: April 09, 2009, 06:08:24 AM »
The recovery charger I got at wholesale as my friend is a regional distributor and I am set up at dealer rates.  I was going to get it anyway when I found out what it would do as I have a lot of machinery that is randomly abused in a sort of nonsensical rotation--- producing lots of damaged batteries. d*  ...so I would not include the total cost in there for it.  Say $200 of it.

The equalization is something which could have prevented the problem in advance but needs to be done on a continuing basis, so lets say an added cost of $100 for extra welder fuel. 

Somewhere between the time I get paid for and the time I don't get paid for is the reality of what it costs me to gain something I wouldn't have otherwise.  I try to work on this as I work on in shop projects so I can monitor it  while I work.  All in all I say yes- I should come out at least $2000 ahead at today's prices.

Note that I don't devote a lot of time to improving the condition of the batteries and that they are currently in use along with my 20 other L16's.  That is why this is taking a long time.  I leave the desulfator recovery charger running and switch it around to different pairs of batteries every few days. I have improved them enough to have put them online and they prevent having to turn on the generator in all but the longest storms ar cloudy periods.  We have used maybe 5 to 10 gallons of generator gas in about the last 2 months.

The trick seems to be to get the specific gravity SG of all cells up to good - not having one cell with low SG in a group.  A hydrometer will monitor it on Lead Acid  batteries - not so on AGMs, Gel or others so it is my opinion that Lead Acid are easier to and have a greater chance of recovery from abuse.  It is common to accidently abuse your batteries - especially if you are not aware of the problems... and even if you are.  That is where the proper knowledge to do this comes in handy.  Also - what if there is ever a problem getting them - due to the economic downturn and destruction of US industry or energy sources?

Badly abused batteries can take several months to improve as is mentioned in the book by another free battery proponent, Poor Man's Guide to Wind Power - or close to that.  He tells how to build your own desulfator.  It was not for sale on line the last time I checked, an e-book--- but I bought it when it was.
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Offline Pritch

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Re: OFF GRID POWER; various thoughts on...
« Reply #157 on: April 20, 2009, 01:02:34 AM »
Thanks Glenn.  Do you have any experience with the automatic battery waterers that are out there? 

-- Pritch
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Offline glenn kangiser

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Re: OFF GRID POWER; various thoughts on...
« Reply #158 on: April 25, 2009, 07:45:17 PM »
Haven't come across them, Pritch.  Years ago when I worked at Dodge, I believe, we had a battery filler that was spring loaded on the spout, as I recall - you would push it down and it would stop when the battery was properly filled. 

I currently have a plastic gallon milk jug with a snap on top and a stiff hose pushed through that.  It works well to fill them.   I fill it with rainwater from a 50 gallon drum and use that to fill the batteries.  Probably time to check the drum for mosquito larvae.
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Offline MountainDon

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Re: OFF GRID POWER; various thoughts on...
« Reply #159 on: April 25, 2009, 07:58:52 PM »
I still have one of those Glenn. They work well.



I don't know anyone who uses the auto waterers
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Offline MountainDon

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Re: OFF GRID POWER; various thoughts on...
« Reply #160 on: April 28, 2009, 08:35:23 AM »
Iíve touted the advantages of a MPPT [Maximum Power Point Tracking] Charge Controller in many places on the forum without saying anymore than they are more efficient. Just what does more efficient mean and how is it accomplished?


Iíll begin with a description of how a conventional charge controller, that is any non-MPPT type, works.

In use a conventional charge controller basically connects the output from the PV panels to the batteries. This forces the PV panels to operate at the battery voltage. Battery voltage is not the ideal operating point at which modules produce their rated maximum power.

For an example, letís look at a system one of my neighbors use, since I already have the numbers. He uses six BP 80 watt panels. They are nominally rated as 12 Volts; 17.6 Volts at maximum power rating (Vmp), maximum current output of 4.5 amps (Imp). 17.6 x 4.5 = 79.2 watts. Close enough to be sold as 80 watts. He uses four 12 volt batteries to store the power. The panels are connected in parallel. For the purpose of comparison Iím going to simplify the system down to a single panel.

Situation #1.
The panel puts out a maximum of 4.5 amps. The batteries are sitting at 12 volts. That drags the panel voltage down to 12; 12 x 4.5 = 54 watts. Weíve just lost 26 watts worth of power; 32% of what was purchased. Those 26 watts are not going anywhere, they are not being produced because the panels donít match the batteries.

The panels need to have a higher voltage rating than the batteries though to make up for cloudy days when their output falls. Panel output also falls under high temperature conditions.

Situation #2.
The same 4.5 amp panels, but the batteries have been discharged to where their voltage is down to 11 volts. That drags the voltage of the panels down and we end up with 11 x 4.5 = 49.5 watts, a loss of 30.5 watts; 38% of the rated power.

With MPPT the charge controller momentarily disconnects the panels from the batteries. It then looks at the output of the PV panels and the voltage of the batteries.  It then calculates the best combination of volts and amps to charge the batteries with the maximum amount of power. In other words the MPPT controller can reduce the voltage to match the battery and increase the amps. A conventional controller can not increase the amps.

Inside the MPPT controller is a high efficiency DC to DC converter controlled by a computer chip. It samples the PV panel output and battery voltage continuously; this only takes micro seconds. The DC to DC converter can increase the amperage output to the batteries.

MPPT controllers are best at increasing power output in cold weather and conditions of low battery state of charge. Since cold weather usually means winter that also usually equates to fewer hours of useful sunshine for generating power.

Typical cold weather increases can range from 20 to 40% more power with a MPPT controller. Warm weather increases will be less, maybe only 10 Ė 20% depending on battery use.

The MPPT controller also excels at making best use of the PV panel power over long runs of wire. The PV panels can be connected in series for lower losses in transmission and then brought down to the 12 volts needed for the batteries. There are limits to the upper voltage range for every controller, so that must not be exceeded.


The DC to DC converter actually takes the input DC and changes it to a high frequency AC. Then it converts that AC down to a voltage better suited to the battery condition. They are extremely efficient and small in size.



« Last Edit: April 28, 2009, 09:15:27 AM by MountainDon »
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Offline MountainDon

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Re: OFF GRID POWER; various thoughts on...
« Reply #161 on: April 28, 2009, 08:40:10 AM »
Further note to the above:

The gain in current of a MPPT controller is roughly the same proportion as the percentage difference between the panel voltage and the battery voltage. If the panel is 17 volts and the battery 12 V the gain is 17/12 = 1.41 or 40%. This is under ideal conditions and never happens in real life.

The above equation assumes that the current at 17 volts and 12 V is identical. In real life it is not. The nameplate panel ratings are at bright sun and 25 deg panels. If you have bright sun, it heats your panels and you no longer have 25 deg panels. A good rule of thumb is take the nameplate MPP rating and multiply by 0.9 - 0.95.

Heat affects the equation by decreasing the 17 V MPPT and of course lowering the gain. As the battery fills, the 12 is increasing to say 13 or 14, hence the proportion increase in charge current decreases. Note however that the highest increase occurs where you need it the most - into discharged batteries.
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Offline Windpower

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Re: OFF GRID POWER; various thoughts on...
« Reply #162 on: April 29, 2009, 10:41:26 AM »
Thanks Don

I am convinced I need the mppt type

I have almost talked myself into the Xantrex XW 60

the outback has some very nice features but the Xantrex line of inverters and controlers look very compatible with my plans -- they have a single status panel and a remote output that can be programed to start the genny if needed
( a great feature if I go away for a couple days and my DW has to deal with a low power situtation)

and the Xantrex is on sale at the Solar Biz for $470


basically I will have the 2460 watts of solar panels

6  Air X   400 watt wind generators

and a back up diesel (or propane or gas)  genny 

conservatively I should get about 300 KW Hrs a month from the panels and about 180 from the air 400's per month

16 KW hrs per day should be more than enough without the genny unless I really start running the power tools in the shop


Often, our ignorance is not as great as our reluctance to act on what we know.

Offline MountainDon

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Re: OFF GRID POWER; various thoughts on...
« Reply #163 on: April 29, 2009, 05:47:31 PM »

the outback has some very nice ..... the Xantrex line of inverters and controlers .....they have a single status panel and a remote output that can be programed to start the genny if needed
( a great feature if I go away for a couple days and my DW has to deal with a low power situtation)
Outbacks can do all that too. Either should get the job done though.
Just because something has been done and has not failed, doesnít mean it is good design.

Offline glenn kangiser

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Offline Source_to_Sea

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Re: OFF GRID POWER; various thoughts on...
« Reply #165 on: May 07, 2009, 04:38:24 AM »
Don - how's the reliability on these things? Any more/less than a typical controller.


Offline MountainDon

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Re: OFF GRID POWER; various thoughts on...
« Reply #166 on: May 07, 2009, 05:36:40 AM »
Good reliability from what different vendors have said and from the few people I know with them.


The biggest problem source would be from voltage spikes. Use proper lightning arrestors and size the PV string to prevent cold weather wake up shock.
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Offline EcoHeliGuy

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Re: OFF GRID POWER; various thoughts on...
« Reply #167 on: May 10, 2009, 07:36:13 PM »
I have been looking at the Outback system.

Can you explain to me how the MATE and FLEXNET works?

I'm not rapping my head around this at all. so if you can just explain what they do would be great.

I think the Flexnet shows you the info about how your system is operating, but where does the MATE come into play?

as I said totally lost here and might have confused my self.


Also you guys talk about tools in your shop, could you give me a rough idea if I have a hobby wood working shop, for making small things like cutting boards how much extra capacity I'm looking at needing in a battery system? I'm not worried about extra panels as I would only be in the shop maybe one day out of two weeks, so the battery system should be all topped up by then. I just need a rough bases here as to what kind of load someone might use playing with a drill press and a plainer, maybe half a days worth of playing around in the shop might not need more battery capacity? after counting in the added margin in the system anyway?

Thanks

Offline glenn kangiser

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Re: OFF GRID POWER; various thoughts on...
« Reply #168 on: May 10, 2009, 08:08:22 PM »
I think the whole system would have to take into consideration the size of the tools you may want to use in the shop.

I think if you are capable of powering your washing machine you could be capable of powering some of the small shop tools.  Many of these tools are used only for a small amount of time and likely if you are not using them a the same time as the washing machine is running then you would be OK.  I have two 4024's making 240 volts or 120 and find that I can do most anything in the shop with about 2500 watts of panels and a 1000 watt wind generator.  For heavy use I can charge or power with the welder generator.  I seldom do though.  I would recommend at least 8 to 12 L16 batteries for shop use.  I also power a wire feed welder sometimes for several hours of off and on welding without the generator.

Even one 4000 watt inverter will handle a lot of shop tools.  A 2 horse motor only takes about 1500 watts under full load but requires extra starting capacity.  I commonly use that and more on my 120v inverter. 
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Offline EcoHeliGuy

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Re: OFF GRID POWER; various thoughts on...
« Reply #169 on: May 10, 2009, 08:16:07 PM »
Thanks that was my thoughts too, but wanted to make sure I wasn't missing anything, a small bench top drill press probly uses about the same power as a stand up vacuum.

another question, am I going to find that the majority of common well pumps are going to be wanting 240V?

I would rather not have to deal with 240V if I don't have too, but at the same time my goal is to have as common of a house as a grid tied one (I know that means big bucks in a solar system)

Offline glenn kangiser

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Re: OFF GRID POWER; various thoughts on...
« Reply #170 on: May 10, 2009, 08:56:58 PM »
Grundfos SQ Flex takes care of that problem- nearly any way you want to power it.
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Offline MountainDon

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Re: OFF GRID POWER; various thoughts on...
« Reply #171 on: May 11, 2009, 01:46:18 PM »
In brief, Outbacks FlexNet is a fancy monitoring system. It acts like a "fuel gauge" style status bar, current state-of-charge and whether you are currently charging or discharging your batteries. It also shows the amount of power your system is currently producing and consuming as well as the amount of power going IN and OUT of your battery bank. Another thing it will do is monitor the cumulative energy your system has produced and consumed as well as the total amount of energy that has gone to charging your batteries. It's 'bells and whisltes'; nice but not necessary, even to a number guy like myself.   ;D

The Mate on the other hand is a remote programming management tool. One Mate can service several inverters and charge controllers. It's very good to have. The Hub will allow the connection of many items to one mate.

Just because something has been done and has not failed, doesnít mean it is good design.

Offline MountainDon

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Re: OFF GRID POWER; various thoughts on...
« Reply #172 on: May 15, 2009, 08:16:20 AM »
Grounding the PV system.

By that I mean the DC side of the system. And by system I mean a stand alone off grid system. The AC side of the system should be treated as any normal grid tied AC system. That means the AC side should have the neutral AC wire bonded (connected) to the grounding electrode conductor (a.k.a. the bare ground wire) at one point, usually within the service panel and then connected to the grounding electrode (the 8 ft copper plated rod in the ground, metal water pipe, etc.)

The DC side is similar but has special requirements. For example, there are special ground requirements and ground fault devices required for any roof top PV panel installations. Iím not going to touch on roof top installations. The following information is intended for ground level or pole mounted panel installations. Let it be noted that references to the NEC rules are made because many of us will have to have our PV installations inspected and approved. Iím not passing judgment of the validity of the NEC rulings, Iím just relaying information as I understand it. If we do not expect to be inspectedÖ well, take this all into consideration.

Letís start with the PV panels themselves. All panel module frames must be connected to a ground. The modules must be bonded to the supporting framework and any other metal parts such as poles, combiner boxes and power centers. The NEC does not consider a connection bolted through an aluminum module frame to a support as a viable ground connection. That is because of the normal oxidation or the anodizing of aluminum. Current rules require special tin plated connectors that are secured to the aluminum with stainless steel 10-32 machine screws and nuts. Recent PV modules are manufactured with marked ground points and a pre-punched hole for the 10-32 fasteners. Self tapping, or self threading screws used to be allowed for ground lug connections. That has been disallowed because of the rule that requires all threaded electrical connections to be able to withstand at least 10 tightening and loosening cycles. Self-threaders fail that test on aluminum.

Hereís a more or less typical NEC drive-you-crazy ruling... Those marked ground points are the only ones recognized for use. The only thing that sets these apart from any other hole is that they are punch marked with a ground symbol and that is the point where the connection was made during testing.     So any other hole could work, itís simply not approved.    d*   Ooops, I was editorializing.

The special approved ground lugs are expensive; (TheSolar.Biz has the best price Iíve seen, about half what most others charge.) An alternate that may be approved by some inspectors, is a stainless steel machine screw and nut with two stainless steel washers. The copper grounding wire would be wound once around the bolt between the two washers and then the bolt tightened.

The module grounding rule goes on to state that removing a panel for maintenance shall not interrupt the grounding of any other module. This also applies to any grounded equipment; removal of any piece of grounded equipment must not interrupt the grounding path of any other equipment. The special ground lugs make this easy as they use a ďlay-inĒ method with set screw for securing the wire to the lug. So the best practice would be to use one of these lugs on each module and on any of the aluminum support arms. Connect all together using bare copper wire of the same size, or larger, as the wire used for the positive and negative module connections, usually 10 AWG. Connecting the ground to a steel component (pole) can be done with more traditional methods (screws, bolts) as long as they are approved for outdoor use. Those little green grounding screws on outlets and what not are not outside approved; they will rust. Use stainless steel and it should be okay.

It should also be noted that grounding lugs must be secured with sole purpose fasteners. That is to say the bolt used for the grounding lug must not also be used to hold other components together. So, no doubling up a ground connector to a bolt that is securing a panel to a mount arm.

In short, the panels, all metal frames and parts should be connected with a bare copper grounding wire; everything from the modules to the combiner box. From the combiner box copper wires will more than likely be connected to a larger diameter wire to transmit the power to the charge controller.

Where oversized wires are used to minimize voltage drop the equipment grounding connector must be of at least the same size as the over sized wires, according to the NEC. That means the third wire must be the same size as the positive and the negative wires. This is commonly overlooked or not understood. This could be expensive on a long panel to controller run, but there is an out. If the distance between the modules and the charge controller and batteries is greater than 30 feet (the NEC is vague on this), the third wire may be dispensed with. This will be referred to as a remote array. As well as the distance requirement, the second condition that must be met is the absence of any other conductive path from A to B. That is, no metal fences, water pipes, metal conduit, communication cables, etc.

There are two ways to ground such a remote array:
1) Bond the negative conductor to the grounding system at both the array and at the inverter/battery/power center location. Do not run any equipment grounding conductors between the two locations. (Run only the positive and negative wires.) Use ground rods at both locations. Do not bond the ground rods together. If the two conditions (distance and no conductive path) cannot be met, then the following method must be used:

2) Do not bond the negative to the grounding system at the array. Bond the negative only at the inverter/battery/power center. Run an equipment grounding conductor between the two locations. Use ground rods at both locations.

In a 12 volt DC system it is not necessary to bond either of the power carrying wires to the grounding electrode. Normally, we will ground the negative wire; most inverters and other equipment is made to operate with the negative grounded.  Most 24 volt DC and all higher voltage systems are required to have a single point where one of the power carrying wires, normally the negative wire, is bonded to the ground wire and the grounding electrode, the same as in an AC system. The rule is actually written around the 50 volt DC figure; below 50 VDC a grounding bond is not required, above 50 VDC it is required. Keep in mind the open circuit voltages during cold weather can be considerably higher than the nominal system voltage. That is why I say some 24 volt systems may require bonding and some may not. I think itís best to bond in any DC system. Note that 48 is the generally acknowledged point where DC voltages become life threatening.

The 12 volt system would be exempt from this bonding but is required to have a properly sized DC rated current overcurrent protection device (fuse or breaker) in each of the negative and positive conductors. These can be expensive and it may be cheaper to install a bonding point and have a disconnect and overcurrent device in only the non grounded wire (positive wire). Also note that low voltage fluorescent lamps start with greater reliability in a grounded system.

The DC connection to the grounding electrode can be confusing. If more than one DC equipment grounding conductor is attached to the grounding electrode, those ground conductors must be the same size as the largest power conductor in the system. This would be the battery cable size in most systems. If there is only one conductor connected to the grounding electrode, the NEC allows DC grounding electrode conductors as small as number 6 AWG (copper to be used. Go figure; I dunno.  ???  The best solution to this problem is to use a common single grounding bus bar in the system. Connect the components to this point. Then connect the equipment grounding conductor from the bus bar to the grounding electrode. For this reason it is also best to use separate grounding rods for AC and DC.

Grounding would not be complete without the mention of lightning protection. The grounding wires connecting the modules to the frames and down to the grounding electrode will serve as a protective path for lightning strikes on an array. However there is still the danger of high voltage surges coursing down the wires to the charge controller and other components or yourself. A lightning arrestor is required. There are ones designed for DC and ones for AC. On the DC side an arrestor should be mounted on the combiner box. There are three wires. One is connected to the positive, another to the negative wires, after all module outputs are combined. The third wire connects to the common ground bus and then to the grounding electrode. If lightning causes a high voltage spike it is diverted to ground.

Just because something has been done and has not failed, doesnít mean it is good design.

Offline glenn kangiser

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Re: OFF GRID POWER; various thoughts on...
« Reply #173 on: May 16, 2009, 06:35:13 AM »
Thanks Don - a lot to digest there.

For uninspected systems a solar electrical system designer clued me in on a low cost alternative for a lightening arrestor.

An automotive spark plug grounded at the base, with the hot terminal connected to the positive lead  from the wind turbine or it could be for an array.  The negatives would be grounded.  In the case of lightening it would easily jump the spark gap of the spark plug on the positive leg, but the generator or array voltage would not.

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Offline MountainDon

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Re: OFF GRID POWER; various thoughts on...
« Reply #174 on: May 18, 2009, 11:31:50 AM »
Interesting idea.  :D
What heat range plug is suggested?
Should it be an resistor type?
Maybe a Bosch 4 electrode platinum, or a SpltFire?  ???

 rofl rofl rofl rofl

Delta arrestor modules are only $40.
« Last Edit: May 18, 2009, 11:58:14 AM by MountainDon »
Just because something has been done and has not failed, doesnít mean it is good design.

 

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