Electrical Sensitivity

System · May 2010

Okay, this may sound a bit strange but it's for real.

My wife has an odd sensitivity to electrical fields, cell phones, batteries, etc.. Used to be bad - very negative physical reactions to anyone with a cell phone on, especially Verizon. She could literally tell within a few minutes if someone had a cell phone on and was always right. Much better now, but still somewhat of a problem. Also negative reaction to certain computers, especially more powerful ones. She currently has an old Macbook G3 which she is fine with for 2 or 3 hours. We had our old house rewired with shielded wiring.

We have a mountain property (5 acres) and are looking at putting in a ground-mount solar system. We've talked with contractors. Best location for the panels is on a hill about 500 feet away (heavy wire will be used I'm told). We're currently on the grid but are looking at being off-grid in the near future. So we're considering the best place to house the batteries. I'm a newby. I'm guessing having the battery array close to the house is best, but could it be placed 100 feet away? 200 feet away?

Thanks

BB. · May 2010

Re: Electrical Sensitivity

Sorry about the aflection... In an electric/electronic world, it is difficult to get away from the effects of electricity.

Basically, to send power over a distance, the higher the voltage, the less you have to spend on copper/aluminum wire to send it.

So, first, it would be very helpful to understand how much power you need (Watt*Hours or Amp*Hours at what voltage) per day. And possibly by season (winter months means less solar power, may need backup genset and/or more panels). So accurate measurements and how flexible you are regarding your power needs and what power growth you see in the next 5+ years (it is difficult to "grow" a solar system by more than 2x without almost scrapping the original system).

If need to measure your power usage--A Kill-a-Watt Meter is great for 120 VAC power. And an Amp*Hour/Watt*Hour meter like one of these is helpful for DC power measurements.

So, you will have a trade-off... It costs more to send power at high(er)--Solar Charge controllers for battery banks are limited to ~Vmp=100 VDC (although, a new unit should be coming out that may almost double that number).

Another option would be to put the panels+batteries at the remote site, and just send 120/240 VAC split phase to your home (or even higher voltage). Doing things like this will reduce the cost (and size) of the cable run.

If you are concerned with 60 Hz power near your home, perhaps you want to limit yourself to DC only--But even then, DC only is not really DC--it is PWM (pulse width modulation) which may be 1,000-20,000 Hz switching frequency--Basically just higher frequency version of 60 Hz AC power.

Proper wiring practices and shielding may help. But, since there is little information on human sensitivity to EMI/RFI as displayed by your family--There is not much to go on (that I have seen) that describes what works or doesn't work for your requirements. Obviously, you don't want to spend money on something that may not work for you.

So, in designing such a system--it would be helpful to know what is acceptable or not acceptable for your residence.

-Bill

niel · May 2010

Re: Electrical Sensitivity

we ran into a guy some years back with the same affliction, but i do not remember his username or if he solved any of his problems by going solar.

the grid does emit an electromagnetic field as will some of the equipment for solar. this may necessitate keeping it some distance from the house, but the only way to know for sure would be to expose yourself to a system already in place to see its effects and this may apply to the batteries too as they act somewhat as a buffer for electronics. some of this energy will follow the ac output of the inverter(s) and there isn't much one can do about that. with putting batteries farther away the batteries will be in weather extremes and a bit of extra capacity over the normally calculated system should be employed.

even the charge controllers will emit some radiation in the air and through the wires so if you are going off grid to get away from the emf of the grid that you will just be trading it for the solar source that also contains some. it will depend on one's sensitivity as even part b certified equipment will emit some, but it is reduced to a predetermined level.

as to the solar system in general you'd probably want to go with higher voltages from the pvs to help overcome resistive losses which will be somewhat high with that kind of distance involved. the heavy wiring is understandable. the battery bank will no doubt be a 48v to also help in keeping losses down and efficiencies higher. this means an mppt controller and probably the xantrex xw mppt 60-150 at this point to be the best controller overall in your needs.

this is just general talk i give and is probably educating you on some aspects that an installer may not have time to teach you of, but it can give you a general platform that you can strike a more meaningful talk with your installer to achieve the goals you have in mind. he does have other installs that he can allow you to test sensitivities now doesn't he?

System2 · May 2010

Re: Electrical Sensitivity

BB, Niel, thanks very much for the data. I’m not exactly sure what is relevant, but let me see if I can add a bit of data, probably too much.

My wife is fine with our current home (Pasadena, CA) which we had rewired with shielded cables. 200 amp service. 5 BR, 3 baths. Central AC is electric. Energy efficient fridge, dishwasher and some computers, printers, and stereo stuff. Mostly all compact fluorescents. We’re a bit wasteful, but I think our current usage per the power company is about 16 kWh per day.

The mountain home ( 5 acres - 90 miles away) is a 2nd home but may become our primary residence in a few years. It has two small houses/cabins. One is 600 sq. ft. and the other is 1000 sq. ft on 2 floors. Elevation is 4800 feet. Winters are not too bad - a foot or two of snow now and then. Dec – March temps in the 20s, occasionally in the teens. Summers mild. All heating is wood stove, with propane heaters available if we get lazy. We have a great open south-facing hill on the north side of the property. A dirt road goes to where I would put the ground-mount system, with the panels about 500 feet from the houses.

For our current needs at the mountain property (less than home) the installers figured that a 3-4 KW system would be fine, but we’re looking at future possibilities pretty closely. For example, we’re looking at the possibility of gas prices really going through the roof, so we’re considering an all-electric vehicle and charging it from solar. I can’t afford the current, practical (for me) electric cars (Tesla’s 200-mile range roadster is well over $100K). However, I did ask Tesla about solar charging. I was told that a dedicated 3.2kw solar system/solar garage would be practical for a Tesla car driven 12000 miles a year. My wife is also looking at doing ceramics classes up there, so that could involve an electric kiln (which would probably mean on firing days, everything else gets turned off). So more practical for me might be a 6-7 kw system with some room for expansion. Having said that, with a fridge (or snow) and a few light bulbs my wife and I can be quite happy in the mountains for a long time. So while we love our computers, scanners, printers, etc., we can do without them if we need to. But the current insane economic scene has me thinking that having an affluence of power or potential for power would not be a bad thing, either for family or my ability to help my neighbors and others.

Unless there is something I’m missing, I don’t think 60hz is a problem. Don’t have problems at our Pasadena home, on the grid.

Having the panels and the battery bank at the remote site sounds interesting. The two companies who gave me estimates didn’t mention that possibility. I guess that means that the whole system is in the remote area. Not a problem particularly – I could build a shed for that purpose and there is a dirt road that gets to within 30 feet of the panels. Then I’m just running A/C to the house just like a power company would do, is that right?

I might initially be on the grid. Not sure. I think I get the federal credit even if I am not on the grid, but I think the California state credit requires that I be on the grid.
So if I’m on the grid and it goes down I’d need a backup generator. Could be propane or gas. And my area is rather remote so if lines are knocked down by snow it might be 2 – 3 weeks before I’m back in business.

Niels, yes you’re right of course – my wife needs to go to some ground installations and hang around for awhile and see how it is. We will definitely do that.

Oh dear, this post is too long. Sorry. But even if there are no further posts I’ve already benefited from the previous ones. Thanks very much.

Bob

BB. · May 2010

Re: Electrical Sensitivity

Bob,

piperfection wrote: »

For our current needs at the mountain property (less than home) the installers figured that a 3-4 KW system would be fine, but we’re looking at future possibilities pretty closely.

Let's use PV Watts website for Dagget CA, 4kW of panel, 0.52 derating (flooded cell batteries, inverter), fixed mount panels:

"Station Identification"
"City:","Dagget"
"State:","California"
"Lat (deg N):", 34.87
"Long (deg W):", 116.78
"Elev (m): ", 588
"PV System Specifications"
"DC Rating:"," 4.0 kW"
"DC to AC Derate Factor:"," 0.520"
"AC Rating:"," 2.1 kW"
"Array Type: Fixed Tilt"
"Array Tilt:"," 34.9"
"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, 5.59, 338, 42.25
2, 6.03, 320, 40.00
3, 7.10, 422, 52.75
4, 7.74, 436, 54.50
5, 7.42, 417, 52.12
6, 7.42, 392, 49.00
7, 7.33, 390, 48.75
8, 7.40, 398, 49.75
9, 7.34, 391, 48.88
10, 6.76, 386, 48.25
11, 5.78, 332, 41.50
12, 5.20, 318, 39.75
"Year", 6.76, 4541, 567.62

In that area, 4kW of panels would give you roughly 300-400 kWHrs per month for an off-grid system. Or 10-13kWhrs per day...

Now, we are a cheap group of people here--That is a fair amount of power for an off-grid home and does not come cheap. Very roughly, a 4kW system (off grid) might cost $40-$60,000 or so installed (I am not an installer or in the solar business--just trying to set rough expectations). And your power, over 20 years, will probably cost you around $1-$2 per kWH (you will need to replace batteries every 7-10 years or so +/- and may have other occasional hardware issues).

If you have the option for grid power at a reasonable price--You might very well consider going that way, and use either a Grid Tied solar system (works with AC utility power to keep costs down), or a hybrid Grid Tied / Off Grid (GT when the AC utility power is up, off-grid for emergency power). And, you can connect a generator to the system too.

For example, we’re looking at the possibility of gas prices really going through the roof, so we’re considering an all-electric vehicle and charging it from solar. I can’t afford the current, practical (for me) electric cars (Tesla’s 200-mile range roadster is well over $100K). However, I did ask Tesla about solar charging. I was told that a dedicated 3.2kw solar system/solar garage would be practical for a Tesla car driven 12000 miles a year.

I would do a little work with a pencil first to see if Off-Grid solar would give you what you are looking for... A 4kW off grid system will give you ~ 4,541 kWH per year. If the Tesla is 250 WH per mile:

4,542 kWH per year / 0.250 kWH per mile = 18,000 miles per year

Now, that assumes 100% power usage from your off grid system... I would tend to believe that you would be lucky to use 1/2 or even 1/3 of the power generated. A more practical number would be looking at the kWH per day / mileage... 10-13kWH per day:

10 kWH per winter day average / 0.25 WH per mile = 40 miles per day--and you would store about 3 days of sun in your off-grid battery bank--which would give you ~120 miles of useful range from 3 days of winter sun/fixed battery bank storage.

My wife is also looking at doing ceramics classes up there, so that could involve an electric kiln (which would probably mean on firing days, everything else gets turned off). So more practical for me might be a 6-7 kw system with some room for expansion. Having said that, with a fridge (or snow) and a few light bulbs my wife and I can be quite happy in the mountains for a long time. So while we love our computers, scanners, printers, etc., we can do without them if we need to. But the current insane economic scene has me thinking that having an affluence of power or potential for power would not be a bad thing, either for family or my ability to help my neighbors and others.

The kiln may be a poor candidate for solar off-grid power (I don't know how many kWH per firing). Propane would probably be a much better deal.

Also, if the power is random (say 1 Friday every week)--it is expensive to store the power for 1 day a week of heavy use... Or, you over size the panels and throw away power when you have nothing to use it for. And, it may be down to using fuel in the genset vs propane firing directly (I know there can be issues with the "gas" in the kiln--and propane may not be compatible with your wife's glazes).

It depends on your needs and how much you can justify to spend.

Having the panels and the battery bank at the remote site sounds interesting. The two companies who gave me estimates didn’t mention that possibility. I guess that means that the whole system is in the remote area. Not a problem particularly – I could build a shed for that purpose and there is a dirt road that gets to within 30 feet of the panels. Then I’m just running A/C to the house just like a power company would do, is that right?

Yes--sort of... Inverters do waste a bit of power just running. So there are various ways to reduce power usage (say running making AC for a second to check if their are any loads > 8 watts turned on). Larger inverters may take 20 watts or more "just idling".

You can "play games"... Use a bigger inverter in "search mode" to run the fridge, well pump, etc... And run a second, small inverter to operate the cell phone charger, laptop, on demand lighting, etc.

Off grid power is costly, so anything you can do to reduce your loads, and reduce waste--will usually result in substantial savings.

I might initially be on the grid. Not sure. I think I get the federal credit even if I am not on the grid, but I think the California state credit requires that I be on the grid.

If you have grid and it cost you less than $20,000 to run to your home/cabin--it is probably worth it.

There are a couple people here that are looking at bringing power to the edge of the properly, then having to run power for another 1/2-1 mile or so using smaller gauge.wire... This may limit them to 1-2,000 watts peak power. But they can use the power to charge and Off-Grid 6kW inverter+battery bank. It appears the XW system may work well for that application... Basically, for lower power needs, the energy comes from the utility. For higher power needs (or during outages) the power comes from the inverter + battery bank.

So if I’m on the grid and it goes down I’d need a backup generator. Could be propane or gas. And my area is rather remote so if lines are knocked down by snow it might be 2 – 3 weeks before I’m back in business.

A hybrid system (Grid Tie/Off Grid capable inverter + battery bank + backup genset + solar panels as you can afford them) could be your optimum solution.

You have the advantage of grid tied power (unlimited "storage" by the utility, your batteries last a long time because they are mostly "in float mode"). And you have the ability for multiple power sources (utility, solar panels, backup genset). Plus because it is Grid TIed, you should have all of the tax breaks, credits, and rebates available for your system.

The downside is that a hybrid system is not cheap. And you still will have to service and replace batteries every XX years.

You can read about the XW system here (4-6kW inverter + 24 or 48 volt battery bank).

There are a lot of issues to balance out here... Asking the questions now before you sign the contract should get you much closer to your optimum solution for your home/family.

-Bill

niel · May 2010

Re: Electrical Sensitivity

a kiln? i don't think so as electric resistance heat is not a good or efficient way to use solar. to do so would add an enormous expense to the already expensive proposition you already have. if you have the room and $ to burn for it it is possible to do though. my bet would be to use a generator for such a large usage as this would keep some costs down and still allow her to do her baking at the trade-off of a bit of noise and use of fuel.

as to the equipment being remote i only said that to facilitate keeping any possible radiations from the solar equipment farther away from your living area. you could bring it all to the cabin and still make use of shielding and such to help in keeping any stray radiations down. btw, for those out there reading this radiation does not mean radioactivity as that's a different animal.

now the precautions done in your present home can be done for this one too. the higher dc voltages would have less transmission losses than the inverted ac would and when batteries are in a better controlled environment (ie temperature) you may get better performance from them too. flooded lead acid batteries do give off hydrogen gas when charged however and that can be dangerous. many opt for sealed agm batteries when it comes to being in their living quarters area. you could still use the fla type inside, but you need to properly vent the batteries and a large battery bank as what you would need would have that much more of a hydrogen gas problem needing to be vented outside. if you were to get a strong backdraft from the woodburner it could cause major problems and i just don't trust large fla banks in living quarters areas.

you have some options here as even an fla battery bank could be brought close to the cabin being in say a shed nearby. if it is with the rest of the solar equipment then the majority benefit of running the distance with the higher dc voltages from the pvs to overcome losses will be still realized. one thing i would do regardless is to have the pvs fused at or near the pvs for to have the convenience of it near the cabin could allow a high voltage short to occur without the benefit of a fuse popping as the short could bypass the fuses leading to major trouble.

do make your system a bit larger as loads always expand and possibly have a separate array group for the e car. the only trouble with that is it needs to charge during the day and if you are out and about during the day the benefit will not be there in an off grid installation as at least with a grid installation one could use the grid kind of like a battery making it possible to charge an e car anytime.

btw, writing long posts is ok with me and bb is one that is noted for them himself.;):D8)

BB. · May 2010

Re: Electrical Sensitivity

And I have hit the 5,000 character positing limit more than once myself--sometime several times with "one post". :roll:

-Bill

System2 · May 2010

Re: Electrical Sensitivity

Wow, great information! I'm really going to have to think this all the way through a few more times and adjust things. Thanks so much. Bob

Electrical Sensitivity

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