Situational System

3 Posts
Feb 12, 2011 08:21 am
Situational System

I have a desire to get an expandable solar system started. I have quite a few issues that I think might be expensive problems. My biggest problem is myself, since I am pretty insistent that the system be off grid capable.
Basically I would want to start with a 1 KW system, grid tied, battery back up that could be expanded with additional panels to up to a 6 KW system, with the capability of accepting energy from a generator, and watermill or windmill or the kids new stationary pedal bike charger I built.
The problems I think lie in the distances. The main electrical box coming into my house is at the house, the sub box on the shop building that has the 85% solar exposure roof, and happens to be about 150 feet from the house and across a creek.
I had a fairly large local solar company come out and give me an estimate, which they rescinded a month later. They said they no longer wanted anything to do with battery based grid tie systems, and were pulling all their contracts.
I am now in the mind to purchase a system and just do it myself. If you have any ideas or suggestions for the system please post them.
« Last Edit: Feb 13, 2011 08:00 am by Joe Bick »
351 Posts
Feb 14, 2011 12:28 pm
Re: Situational System

Your post generates a lot of questions.
Have you quantified your wind and hydro resources ? A lot of people think they have a resource until they measure it.   If you have a good hydro resource, that is the first thing I’d put in.  How much head and flow do you have that you can use ?
Why are you insisting on battery backup ? Do you have a lot of outages of long duration ?  Have you quantified what size of battery bank you will need and do you expect it to grow with the rest of the system ?
Have you done a load inventory and executed energy conservation efforts to control the size of your system ?  6kW is a lot of power.  Or are you thinking of “selling the excess”.  Most power companies have different rules for system that produces something near the total annual usage or less, and a system that generates excess power.  The additional requirements to become a power producer often drive the cost up to the impractical range.
Your idea of connecting the pedal bike charger to the system is an un-necessary complication.  Might as well send the kids out to carry water from the creek to the swimming pool with a cup.  Buy a battery and a small 12V TV and keep it as a separate system.
Why locate the solar panels on the shop roof that is so far away ?  How about a nice ground based rack system closer to the house ?
99 Posts
Feb 14, 2011 01:22 pm
Re: Situational System

I have a desire to get an expandable solar system started.


I am pretty insistent that the system be off grid capable.

I agree completely.  The grid is old, dependent on subsidies, and increasingly unreliable.  And in the event of economic and/or social collapse, it'll be completely useless.  However, perhaps you should reconsider the grid-tie portion.  If it's off-grid capable, why maintain a grid connection at all?  The grid is like training wheels.  If you still think you need it, your system is not truly off-grid capable.

Basically I would want to start with a 1 KW system, grid tied, battery back up that could be expanded with additional panels to up to a 6 KW system, with the capability of accepting energy from a generator, and watermill or windmill or the kids new stationary pedal bike charger I built.

It sounds like you need to establish your actual requirements.  Sure you can start with 1kW and expand it, but it will be cheaper and easier to start with the minimum of what you actually need.  In my experience, you're going to need *at least* 1-2kW of solar and 1kW of something counter-cyclical to solar -- wind is good, though water is great if you have it.  If you only use solar, you'll need *at least* 3kW and a bigger battery bank.  These figures are dependent upon you having high-efficiency appliances and lighting and NO electrically-powered heat (incl. hot water, dryer, oven, etc.).

The problems I think lie in the distances.

Distances can be solved with two methods -- up-sizing your wiring or up-converting your voltage, or both.  My system is 24V.  That's what my wind turbine puts out and what I designed my battery bank for.  The solar accomodates that too, by down-converting from 48V at the charge controller.  I like 24V because many things natively operate at that voltage, including a wide selection of down-converters to 12V.  I have no problems getting 24V some 150' to the opposite side of my house with virtually no voltage drop.  The wire isn't terribly expensive, but it's not cheap.  I don't recall what guage I used, but it's whatever was recommended by the wire guage charts.  If you want to use a cheaper guage wire, design your system to be 48V.  However, understand that some of your other components may be more expensive.

I had a fairly large local solar company come out and give me an estimate, which they rescinded a month later. They said they no longer wanted anything to do with battery based grid tie systems, and were pulling all their contracts.

That's typical.  It's cheaper and easier for them to install grid-tie-only systems.  And because of tax rebates, they have plenty of business doing only those.  I personally think it's insane to do a grid-tie system, as there is no benefit from the expense.  You're still dependent on the grid, but now a very expensive producer.

You'll be better off doing it yourself.  I wouldn't trust most of them to touch my system anyway.  I started off using a contractor because the wind turbine was only available through a dealer-installer.  They screwed everything up.  Reversed polarity, no disconnects, no fuses or lightning protection, inappropriate grounding, etc.  I had to redo everything.  It's best just to do it yourself from the beginning -- as long as you do plenty of research and ensure you're being safe.
3 Posts
Feb 15, 2011 09:40 am
Re: Situational System

Thanks for the replies Ken and Thomas,
I have spent three years getting to this stage. I got my first solar estimate when I got back from Iraq with the suspicion that the global reserve currency might have a problem...
So I got an estimate for $55K (after rebate), no battery back up and not enough rack room/ panels cover more than 60% of my usage. I have spent a lot of time getting efficient since then. I can list every load in my home and shop, the time it is used, and a 10% overage for inefficiency and sloppiness.
My most recent estimate was for 4KW, $25K, before rebate, including batteries and installation.
I refuse to carry debt, so now we are 60 days down the road and I am prepared to pay them, they do not want to do it.
The currency crisis is gathering steam (price inflation due to excess reserve printing)so I want to get something on line now, even if it is insufficient. I can build a gasifier and run a generator.
I need 2KW minimum to operate my home. Call it the survival load.
4KW covers my total needs as my family lives right now.
6KW covers my intended aquaponics based greenhouse garden.
The bicycle charger is more for remedial attitude adjustments of my kids than for charging. I have two 5 hp lawnmower engines that run off stratified downdraft gasification to 12V alternators. I have a year round stream running 80+ GPM average with 17' of head and no intention currently of harnessing that for more than mechanical, large waterwheel torque to operate other equipment, and maintain the water in the stream bed.
I intend to use 6V golf cart batteries, (wide spread, large capacity, locally available, easily replaced) but I am willing to listen to other alternatives and give them consideration. I have first hand seen lead acid batteries last over 20 years on a system that was not drawn down more than 10% of battery charge.
 I think that about covers the situation.
So should I just call the sales people here at the altE store and go with whatever they recommend?
By the time we get done writing this, every $100 in the bank will only have $80 in purchasing power left.....Thanks to Bernanke.
26 Posts
Feb 15, 2011 06:30 pm
Re: Situational System

Personally, I would only go with batteries designed and warrantied for long life in the intended role.  Golf cart batteries may work well, but what if, as you fear, we have a global currency crisis and you cannot find replacements in 3-5 years?  I'd rather have something I know will last at least 10 years and have been known to last 20+ years, which the Rolls-Surrette deep cycle batteries are known for.  I've also just recently added two redundant parallel banks in case one or more of the batteries fail.  If you only have a single string of batteries, e.g. 6x4V=24V or 8x6V=48V, then the loss of only one of them results in the entire string being worthless since you cannot maintain your system voltage without it.  I have two strings of 6x4V in parallel (or I will just as soon as the new ones are delivered anyway), preventing a single point of failure.  Therefore, I'm confident my batteries will see me through the current economically/politically/socially volatile times.

How about this system built from parts available on AltE:

Plus shipping of course, but you can probably get free shipping for an order of that size (plus some 5-10% discount probably).

That's also tax-deductible... I think it's a 30% federal rebate, so you'll get $10k back.  In fact, if you buy this or anything similar, stop paying taxes for the rest of the year if your normal tax liability is less than $10k.

That gets you almost the 6kW you were looking for, plus redundant strings of deep-cycle batteries, and redundant grid-capable inverters, for barely more than you were willing to shell out for only 4kW.  Granted, you have to install it yourself, but that's the only way you'll know it's done right, plus you'll be intimately familiar with it so that you can troubleshoot in the future. 

BTW, that list assumes that you have 30' available across your roof -- 3 strings of 9 panels; each string connected in series for 108V to one of the charge controllers.

I would build the battery boxes out of plywood.  I used 3/4" so that I could screw them on-edge.  Insert a 2" PVC pipe for a vent.

For best results, add a wind turbine or water turbine to this system.  I would recommend the Bergey XL.1 1kW turbine on an 80-100' tower.  Cost should be around $8k, tower & accessories included.  If that's too much, I would eliminate one of the strings of PV panels (plus 2 mounts and 1 charge controller) to get the wind turbine.  It's counter-cyclical to the solar, so you'll greatly improve your average production.  I have direct experience with this.

As far as being debt-free, that is a noble goal, but directly at odds with your recognition that the central bank is inflating our currency to nothing.  The most rational course right now is to take a home equity loan at 3-4% interest to purchase capital improvements such as this.  Leave your liquid assets in inflation-protected investments such as precious metals, commodities, and mining company equities.  So long as you have assets that can be liquidated to pay the debt in full at will, you are essentially debt-free.  But the leverage of cheap credit at a time when the real inflation rate is far greater than your interest rate is too good to rationally pass up!
26 Posts
Feb 15, 2011 06:48 pm
Re: Situational System

BTW, I would seriously recommend tapping the water resource.  Investigate that further before doing the solar even.  You may be able to power your entire load requirement just with the water.  The battery/inverter setup can be the same.  You would just need an appropriate micro water turbine, alternator, and charge controller.
26 Posts
Feb 15, 2011 07:16 pm
Re: Situational System

Here's a diagram I created when I was spec'ing out a system for my father.  Thought it might be helpful to visualize.

In this case, he already had a main utility-connected breaker panel and would be adding the off-grid stuff, transferring some of his circuits to the uninterruptible panel.  My preferred design would be to remove that panel altogether and move all of the loads to the FlexWare panel, perhaps with subpanels.  The utility grid would be directly connected to the Outback panel then.

I also prefer moving as many circuits to DC as possible.  E.g. replace the well pump, refrigerator, lighting, etc., so as to have the improved efficiency and fault-tolerance of not needing the inverters for those loads.  DC-direct also eliminates power factor losses on pumps, motors, CFL & LED lighting, etc.

I think the system design here is overkill for any residential purpose, but he wanted to do this for tax reasons without having to change any loads to make them more efficient.  With proper care to make the loads as efficient as possible, anyone should be able to eliminate 1/2 to 3/4 of the solar and 1/2 of the wind and be just fine.  This system ought to be able to power a small community, which I guess it very well might if/when the SHTF.
3 Posts
Mar 2, 2011 02:24 pm
Re: Situational System

I am trying to digest this and looking over the area I have to place it.
I have a 120 volt sub panel at my shop which is 150 feet from the house and the main panel. Unfortunately the shop roof is the only spot on the property with 85% or better solar exposure, so I have to put the panels there.
Due to the wire loss, I am guessing that the whole system should be located there and the 120 Volt AC should be run back to the main panel at the house?
$30k for the system is not unreasonable. I am going to look online for some how to educational videos for putting this thing together.
I will also be contacting the folks who own the water rights and seeing if I can use them when they are not irrigating their ranch, which would be winter, the least solar producing time! Hopefully it works out!
I am going back to re read all the info, and will post again when I get done.
99 Posts
Mar 4, 2011 12:59 am
Re: Situational System

I would recommend bringing a DC line back to the house if you can, for the reasons given previously, in addition to your AC.  According to the method recommended by AltE, if you wanted to run 450 Watts of loads on DC (more than enough for most lights and small appliances), could find a 6% voltage drop sufferable, and you had a nominal system voltage of 24V, then your Voltage Drop Index would be: VDI = (19*150)/(6*24) = 19.79, which is #4 AWG wire.  If your batteries were at 25V, then a 6% drop would give you 23.5V at your load when drawing 19A (456W).  You can get 150ft of #4 THWN (direct burial) wire for about $175.  If you wanted to upgrade to #2 THWN, it'd be about $350 for 150', and you would only get 4% voltage drop over 150' for a 19A load.  Or you could up your load to 30A (720W) at 6% voltage drop.  You could of course likewise keep increasing the gauge (and price) to achieve less voltage drop at higher amperages.  You have to define your likely loads and budget to figure out which is best.  But at least some capacity to run DC loads directly off the batteries is a good idea for fault tolerance, redundancy, efficiency, etc.
99 Posts
Mar 4, 2011 12:50 pm
Re: Situational System

I would definitely locate the bulk of your system in your shop.  You want your solar panels, charge controllers, batteries, and inverter to be close together.  Also, I like to keep explosive things like hydrogen-producing batteries and propane tanks a good distance from the house just in case.  Inside the house, the AC panel should be set up just as if it had a normal grid connection.  That should not be affected by the fact that you have batteries and an inverter in your shop.  But if you're bringing 24VDC in as well, that should have its own breaker panel (Square-D QO is what I use), and then you can use a voltage converter to step down to 12VDC and have another sub-panel (or maybe 2 -- one on each side of the house) for that.  This way you can have 24V loads (maybe a well pump, refrigerator compressor, etc) and 12V loads (lights, outlets for computers, cell phone chargers, etc.).

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