New to the forums.

kainekaine Registered Users Posts: 3
I stumbled across these forums and I am glad I did. there seems to be a lot of very negligible people on this forum.
a little about my background.. I have work in energy management for many year's as a install contractor for a lot of different company's and DDC provider's. as well as alarm and CCTV system's.

I am new to the area of green energy for home use and am fixing to break ground on a new house with in the next year.. I am planning on doing both solar & wind power with no connections to any power grids.
The solar part of the build is pretty strait forward. and I am working on building the hub for the turbine right now. the wind here shows a average of 13.8mph. I am planning on building a 6 blade variable pitch turbine with a 11ft sweep and a stop break for locking down the turbine when needed..

one main question I have is where can I find a good PMA for this setup? I was looking MW but after looking around the net for a week I cant really find any that is happy with that company or there product's....
I want to keep the system 12vdc so that I can wire the house with very few inverters. ( I want to use all 12v lighting inside and out. ) as well as any other 12vdc appliance's I can find.

I was thinking that these blades would work but I was wondering if anyone has used them and what there results where with them? but I am planning on using 2 sets on a custom hub.
http://www.ebay.com/itm/310612707161?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2648

I am also planning on using a Arduino Mega to control the turbing blade angle,direction & locking break.

Comments

  • BB.BB. Super Moderators, Administrators Posts: 31,063 admin
    Re: New to the forums.

    Welcome to the forum--I think there was an "auto-correct" that changed the word you intended into the opposite. ;)

    Before getting too deep in design of a wind turbine (not really my field), I would like to revisit your choice of battery bus voltage.

    Energy usage is highly personal... And there are many folks that live on 1kWH per day... And folks with a refrigerator+washer+computer+well pump can do with 3.3 kWH per day in a smallish/highly efficient home...

    But for a full off grid home in a hot area with modern appliances (want a little A/C?), you may be looking at 10 kWH per day (300 kWH per month) or (a lot) more...

    A 12 volt battery bus system is very "practical" at 1 kWH per day... For 3.3 kWH per day, a 24 volt or even 48 volts may make sense. And for larger systems, you should be looking at 48 volt battery bus.

    That will affect the winding of your wind turbine--And if you are looking at a large turbine, you should be looking at a MPPT type charge controller/turbine controller (like the Midnite classic plus Clipper) which would push your optimum turbine voltage upwards of 90 volts or more.

    Anyway, if your home is much more than a few room cabin--I would suggest that you should be looking at 120 VAC lighting anyway. Sending 12 VDC any distance takes lots of heavy copper wire and dedicated breakers/fused circuits.

    The losses of running an AC inverter are not that bad (~85% typical AC inverter efficiency), vs the fact that you can send power much farther on much thinner cable--And you can get 120 VAC LED lighting as cheap, if not cheaper, than 12 VDC counter parts.

    I would suggest a 12 volt system would have around a 1,200 watt or so maximum AC inverter and not too much steady state/12 VDC loads. If you "push" the battery bank to large (>~600-800 AH), you are looking at needing to purchase additional solar charge controllers (a 60 amp charge controller can "manage" a 2x larger solar array on a 24 volt bus vs a 12 volt battery bus--Power=Voltage*Current, double the bus voltage, double the power at the same bus current).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • vtmapsvtmaps Solar Expert Posts: 3,738 ✭✭✭✭
    Re: New to the forums.
    kaine wrote: »
    I stumbled across these forums and I am glad I did. there seems to be a lot of very negligible people on this forum.
    a little about my background.
    <snip>
    I want to keep the system 12vdc so that I can wire the house with very few inverters. ( I want to use all 12v lighting inside and out. ) as well as any other 12vdc appliance's I can find.

    Welcome to the forum,

    BB. was much too gentle... Building a 12 volt system is a TERRIBLE idea. The sooner you realize this, the sooner you can design a cost effective system that will meet your needs.

    You will have better and cheaper bulbs and appliances at 120 v AC. Also, a 12 volt system will vary from 11 to 15.5 volts and this will wreak havoc on some DC bulbs and appliances. (even if your power needs are low enough for a 12 volt system, I still recommend 120 volt lights/appliances)

    By the way, are you considering a DC refrigerator? You can buy AC fridges that are just as efficient and cost MUCH less. The money you save on the fridge can buy a more battery or solar panels.

    I thought about DC wiring (briefly) when I built my house. When I researched bathroom vent fans, I found the most efficient were AC units with DC brushless motors... they had a built in power supply to make DC from AC. (today's power supplies and wall warts are incredibly efficient).

    In the event of a major system failure (including dead batteries) I can flip a switch, start my generator, and I'm back in business... everything works on 120 v AC.

    If you are concerned about the "low load" draw of a large inverter that is left on 24/7, you might consider having two inverters, one small inverter which is on 24/7 and a large inverter that you turn on for laundry, power tools, etc.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • kainekaine Registered Users Posts: 3
    Re: New to the forums.

    in the summer here there is plenty of light to run just solar. but in the winter we are under cloud cover 75% of the day with winds hitting 65 to 70mph gust some days. so for the most part it is ether really windy and cloudy. or its really bright but is still pretty windy most the time.

    also we are going to building 90% underground. and the battery's & charge controllers are going to under ground in the middle of the floor plan.

    What about building 2 systems? one 12v and the other 48v? I will have 150sq/ft of floor space with a 8ft ceiling to setup on. are current energy usage is about 2 to 2.5kwh per day..
    as far as the battery's go i was thinking in the 2000ah range should do pretty good. but I haven't really looked into that past the price of the battery's.
  • BB.BB. Super Moderators, Administrators Posts: 31,063 admin
    Re: New to the forums.

    A 2,000 AH battery bank needs ~5% to 13% rate of charge -- Or upwards of 200+ amps @ 12 VDC.

    Change that to a 48 volt battery bank or ~500 AH and a ~60+ amp charge controller.

    200+ amps, you need 3-4 ~$600 MPPT charge controllers. A 60+ amp charge current only needs ~1 $600 MPPT charge controller (typically around 50-90 amps maximum for standard MPPT controller).

    Also, what AH batteries are you looking at to build at that 2,000 AH @ 12 volt battery bank? My personal suggestion is to build out one series string of batteries/cells. You can go to 2-3 parallel strings, but that adds a bunch of maintenance (more cells to water, more cables to monitor, more fusing/breakers per string) and other issues (battery current balancing and monitoring/diagnosing of possible failing connections/cells)...

    If you are thinking of 20x 12 volt @ 100 AH batteries in parallel--Don't do it--It is a whole lot of trouble to get running right and maintaining the bank.

    The Wind Turbine--You probably will have to build your own PMA--There are probably not many out there that would work well for you (the standard "converted" car/truck alternators don't really work).

    And forces on a 60-90 foot tall tower (or higher) will be huge with a large diameter rotor. And the power will go up with the cube of the wind speed--So if you get these very high winds, your mechanical blade governor and braking system will certainly be put to the test (good to hear you are doing the feathering blades and a brake--You need two or three ways minimum to control/shut down a turbine for reliability/safety).

    This is not my field, but we have recommended (for wind):

    Wind Power Links
    www.otherpower.com (good forum for DIY Wind Power)
    Hugh Piggott - Scoraig Wind Electric site for tons of info (from mike90045)
    Scoraig Wind "Recipe Book" for DYI Turbines (from Chris Olson... From his 4/11/2013 post)
    www.greenpowertalk.org (added from "russ"--Like here but more wind/less solar)

    Wind turbines require maintenance--So having a way of flying the turbine without having to rent a crane/cherry picker (if you do not already own one) every time you need to service the turbine, should save you a lot of costs.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • BB.BB. Super Moderators, Administrators Posts: 31,063 admin
    Re: New to the forums.

    Going from your 2.5 kWH per day number--I would suggest looking at 3.3 kWH per day as this will give you enough power for running a full sized Energy Star rated refrigerator plus other loads. Add a ~1,200 to 1,500 watt minimum TSW inverter, and you are ready to go.

    The math would look something like this. First, sizing the battery bank. First rule of thumb is 1-3 days of storage plus a maximum of 50% discharge for longer battery life. 2 days and 50% maximum discharge is a good "nominal" system design:
    • 3,300 WH per day * 1/0.85 inverter eff * 1/12 volt battery bank * 2 days storage * 1/0.50 max discharge = 1,294 AH @ 12 volt bank
    • 3,300 WH per day * 1/0.85 inverter eff * 1/24 volt battery bank * 2 days storage * 1/0.50 max discharge = 647 AH @ 24 volt bank
    • 3,300 WH per day * 1/0.85 inverter eff * 1/48 volt battery bank * 2 days storage * 1/0.50 max discharge = 324 AH @ 48 volt bank
    So, using my rule of thumb to avoid >100 amps of "nominal" current for DC battery wiring and keep charging current to 60-90 amp maximum range (lots of heavy/expensive copper cabling/fuses/breakers/switches)... A 24 volt battery bank is about the maximum, and 48 volt would be nice.

    All three of the above banks "store" the same amount of energy (power = voltage * current; double the voltage at 1/2 the current is the same amount of power)... It is just the 24 or 48 volt battery bank will be easier to build/maintain and use fewer solar charge controllers for the same size of array (lower DC current).

    And note that my suggested battery bank is almost 1/2 the size of the 2,000 AH @ 12 volt battery bank you are looking at.

    Next, we size the charging system to two different ratings. One is sizing the system to the size of the battery bank (larger battery bank needs more charging current) and to the size of the AC/DC loads. First the battery bank sizing:

    A lead acid battery bank should have 5% to 13% rate of charge (you can go 20-25% rate of charge maximum, but for solar, it is not always cost effective for larger than ~13% rate of charge and you should have a charge controller with a remote battery temperature sensor with >13% rate of charge to help prevent thermal run-away--You should have a RBTS anyway as this is good for the battery and can help optimize charging current.
    • 647 AH * 29 volts charging * 1/0.77 panel+controller derating * 0.05 rate of charge = 1,218 Watt array minimum
    • 647 AH * 29 volts charging * 1/0.77 panel+controller derating * 0.10 rate of charge = 2,437 Watt array nominal
    • 647 AH * 29 volts charging * 1/0.77 panel+controller derating * 0.13 rate of charge = 3,168 Watt array "cost effective maximum"
    Note that a 2x larger battery bank capacity would suggest a 2x larger array/charging source.

    Then there is sizing the array for your available sun and loads. Using PV Watts for a fixed array, tilted to latitude in Fort Worth Texas, we get:
    Month    Solar Radiation (kWh/m 2/day)
    1      4.32     
    2      4.77     
    3      5.50     
    4      5.98     
    5      6.02     
    6      6.25     
    7      6.39     
    8      6.31     
    9      5.83     
    10      5.56     
    11      4.43     
    12      4.10     
    Year      5.46
    
    I may have guessed wrong for your location--4.1 hours of sun minimum sounds like more sun than you get with your 75% cloud cover at times... Anyway, to run the math. I suggest tossing the bottom 3 months (using generator or, hopefully, your wind turbine)--But 4.0 hours is still a good amount of sun, so use that for "our calculations" here:
    • 3,3000 WH * 1/0.52 system efficiency * 1/4.0 hours of sun minimum = 1,587 Watt array minimum
    Because the above has "lots of sun" in winter, the array size would be in the range of 1,587 to 3,168 Watt array--With 2,437 Watt array being a healthy nominal size.

    A 2,437 watt array (note, solar calculations are pretty much 10+/- 10% accuracy, I am just carrying digits so you can follow my math) and 4.0 hours of sun would provide:
    • 2437 Watt array * 0.52 end to end system efficiency * 4.0 hours of sun per day = 5,067 = 5.1 kWH per day
    If your loads are truly in the 2.5 kWH per day--Then you could even make this system smaller and save money on battery bank size.

    From you loads, it sounds like you are going to use a "propane" refrigerator? And probably propane for cooking? Note that propane is heavier than air and is a huge safety issue in bermed and/or buried homes. I do not know anything about building codes for propane in homes/buried homes, but adding a ventilation system around pipes (to positively vent any gas leaks) and other issues using propane stove/heating in home can be a big issue (some people use electric appliances because of the fear of gas explosions).

    If you need heating, a larger solar (and wind?) system may support a nice mini-split heat pump system. They are getting efficient enough that they can be operated from an off grid solar power system (assuming the home is well insulated). Also, a few people hear are evening using heat pump based water heaters too (heat pump water heaters are 2-3x more efficient vs resistance heating--and even giving solar hot water a run for its money in some settings).

    Anyway--Before you spend any money, do a couple paper designs first and see what works best for you.

    I am not a fan of small wind--But if you build the system yourself and can do the erection/maintenance--It can be useful addition for place with poor sun (solar only works well with lots of sun--shading and heavy marine layer/etc. are the enemies of solar electric power).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • kainekaine Registered Users Posts: 3
    Re: New to the forums.
    (assuming the home is well insulated)

    Yes it is going to be.. we are building all but 2 room's completely underground. the living room and kitchen are going to be 6ft from grade level down to the floor and extend about 4ft above ground.
    and then the garage above ground with a second entrance inside. the front door is going to be about 15ft from the garage.
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