System for new construction

First, I'm a complete newbie to this forum and the whole solar thing, so please forgive any violation of forum policy in asking this.

I am in the process of building my dream home.  We are hoping to integrate a solar panel system and have started exploring battery backup options. The house is 6500 sq ft with multiple loads that I think I can keep in 20-25 kW range. I have two 5 ton geothermal units for HVAC and gas tankless water heaters.  There are presently near 200 can lights that will be LEDs consuming 10 Watts per light.  We'll be adding a few low voltage systems for accent lighting and maybe another 75-100 LEDs with outside lights, pendants, chandeliers, ceiling fans, etc...  There will be a separate cooling system for an approximate 450 cubic ft wine cellar, plus a Sub-Zero 15' wine refrigerator for white wines.  We have a 60" Wolf dual fuel range, Sub-Zero Pro48 refrigerator, SZ refrig/freezer drawer, SZ ice maker, Wolf microwave, Wolf steam over, and Miele dishwasher in kitchen.  There will be 8 ceiling fans (BigAssFans ranging from 52" to 84").  We would like to have power accessible to most of those loads during a loss of power from grid.  We have purchased a 20kW Generac Synergy generator, but wouldn't mind adding a battery bank with solar panels to charge during day.

Ideally, I'd also love to isolate the electronics from the unstable grid power.  In addition to above load, there will be a control 4 system to manage security, HVAC and lights.  There's a distributed video system with a total of 9 TVs and distributed audio to 20 different zones.  There is also a media room with 7000 watts of power to a 7.4 speaker system using B&W speakers and Classe amps.  There is a projector in that room.  The electronics may represent another 10-15 kW.

So, I need a little help or direction in trying to prepare a system that would electrically isolate the electronics and provide a short backup (likely no more than 1-2 hours to give time to turn off those electronics in case of power failure or maybe keep playing through a short interruption), plus provide enough load to support the more critical loads until generator powers up.  We have had 2 short power outages in the past couple months (presently living about 200 yards from building site), and live in a tornado/storm rich zone that is prone to having power outages during spring/summer storm season.  Would like to keep most of our lifestyles intact even if we are living "off-grid" for a few days following a big storm. Don't plan to watch movies in the theater, but would like to have HVAC, kitchen appliances, part of our lights, and a couple TVs.

I've been looking at 64 SolarWorld 285W panels on 4 dual axis trackers. Have the Generac 20 kW already. Would like to add battery bank and necessary equipment.  I've spoken to a local company about the system, but they seemed a little lost.  I don't know enough to even direct them in the right direction.  I understand what my patients go through when I explain a procedure to them...

Thank you in advance for any help.

CWJ

Comments

  • BB.BB. Super Moderators, Administrators Posts: 32,006 admin
    With solar--You need to add up all your loads (Watts and kWatts) and how long (average kWatts * Hours of operation).

    In general, Grid Tied Solar can be cost effective when compared with the cost of utility power. However, you need to understand what your specific utility offers in terms of "net metering" or other billing options (basically, you are using the utility like a giant AC battery). GT Solar can save you money on power. Around $0.15 or a bit less per kWH is quite possible with GT power systems (turnkey install).

    Off grid solar power, and battery backed off grid solar power (and Hybrid systems that do both GT and Off Grid power) tend to be much more expensive to operate. Somewhere in the $0.50 to $1.00 to $2.00+ per kWH hours. You need to replace batteries every ~5-8 years, electronics (inverters + battery chargers) every 10+ years. And these costs add up.

    For random short term outages-- A genset with reliable fuel supply (natural gas, propane, diesel, etc.) is going to be your best bet. Very little costs if the genset is not running, and roughly $1.00 per kWH for power when it is running.

    If you want plan for weeks to months without power--Then, possible off grid solar power + batteries can make sense for you.

    An off grid home can have a sort of normal electrical life with ~3.3 kWH per day (or 100 kWH per month) with a reasonably small/cost effective system (a perhaps $20-$30,000 or so installed).

    But when you add HVAC and Refrigerators + other loads--You are looking at relatively large and expensive systems (LED TVs, LED Lights, Laptop computers, etc. have really reduced the power usage of those appliances over the years).

    Can still make sense to you (there are more and more off grid folks that run AC off grid these days--Mini Splits can be very interesting).

    In any case--Do not spend any money on solar until you have worked out the basics (we should be able to help you here). A too small system that does not meet your needs--Worthless. And over-sizing a system by 2-4x makes for a terribly expensive system to install and maintain.

    A "small" system that can do 3.3 kWH per day (3,300 WH) is something that can be a do it yourself system. Something that does 30 kWH per day (900 kWH per month)--That may need help of a professional installer unless you have a lot of electrical/contracting experience. And when you toss in a battery bank--That can even through licensed electricians for a loop (most do not work with lower voltage/high current DC systems/battery banks).

    You can choose to battery back (UPS--Unterruptable Power Supply) a few "critical loads" (computers, perhaps some lighting and TV) to run the loads until the genset kicks in.

    You can also have an off grid/backup battery system that powers the smaller devices/lights over night (quiet time), and run the genset during the day for the larger loads (well pumps, HVAC system, Refrigerators, etc.).

    Power usage is a highly personal set of choices--Trying to understand your needs and not trying to put my lifestyle onto your choices. (I have a Grid Tied system and a small AC genset for backup power).

    Remember too--Depending on where you live, you may have other limitations. Cities shut down water when sewer pumps have no power after a couple of days--Cable/Internet/Cell phones may have hours (or a few days) of backup power--So you have to look at your ability to stay behind if you need city Water/Sewer/etc.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • westbranchwestbranch Solar Expert Posts: 5,183 ✭✭✭✭
    Where to begin?

    In Iceland they have a saying,
     'Living on top of a volcano makes you realize what is important and necessary in Life'...

    Don't build a mansion in the Tornado zone.... you need a well built bunker. Oh ya ....media room...

    As Bill said you can have a 'roughing it' style of backup power, what is not absolutely essential, does NOT get connected to the circuits powered by solar... cripes the media room uses enough to power a whole house...

    Only power 1 tv by solar...  not 9
    Downsize the refrigeration units...
    You did not mention water, does it need a pump?
    What about the nat Gas for cooking ( propane?) what is your back up for all those gadget that use gas?
    Subterranean wine cellars do not need cooling...
    Isolate the electronics means you probably want a whole house UPS...

    More later, there is a lot to think about and plan for...
    hth




     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • cotyjewellcotyjewell Registered Users Posts: 4
    Thanks for the comments.

    The HVAC units each use about 1-1.5 kW when running.  We have installed capacitors to help "jump start" the compressors and should lower the starting load to around 3 kW. 

    The total lighting load should stay around 4 kW, and we have it segmented into 2 panels with "essential" loads and non-essential.  Hoping to keep essential load to around 1kW.  

    We have segmented the electronics as well.  Most will be on the non-essential panel (except Control 4 main controller and security). I have the generator set to maintain the essential panel with loss of grid power, but would like to isolate some of the non-essential panel with battery backup for protection and "cleaner" electricity to the expensive electronics.  The media room is a HUGE investment and if I need to spend $20-30k to protect it, I'm willing.

    The house is being built in Norman OK.  There are plenty of tornados in the spring/summer and of course ice storms in the winter.  The neighbors have been without power for as long as a week in the past few years, and I have a friend that lives a few miles north that has gone 10 days without power.  I want to prepare for that possibility, but not with everything in the house.  There is a safe room in the house, and it has isolated circuits to it for lighting, small tv, and refrigerator.

    Electricity here costs around $0.11/kWh, but goes to $0.25/kWh during peak hours.  I'd like to offset that expense, or eliminate it if possible.

    Oh, I also have a large fish aquarium being built that will add another 1-2kW to load.

    Water is on municipal supply, but there is a well that could be used as needed.  There is an aerobic septic system being installed.  There is natural gas for cooking and running generator.

    So, I'd like to plan for 15-20 kW of total load for back-up long-term and another 20kW on the non-essential panel with battery isolation and short-term backup.  

    Hope I gave you enough information to better direct everyone.

    Thanks in advance for your help.

    CWJ 
  • BB.BB. Super Moderators, Administrators Posts: 32,006 admin
    Realize that off grid power (and generator backup) is going to be something like 10x the cost of power for your utility power.

    For example, a 20 kWatt genset running at ~1/2 load is going to consume:

    http://www.dieselserviceandsupply.com/Diesel_Fuel_Consumption.aspx

    Roughly 0.9 gallons per hour.
    • 24 hours per day * 7 days * 0.9 gallons per hour * $2.00 per gallon = $302.40 worth of fuel for 1 week outage
    And who wants to live next to a diesel genset running 24x7 on a smaller piece of property (noise, smell, fumes).

    Or ~$1,200 per month. And that is assuming ~10 kWatt load full time (installation & maintenance costs not included). Or:
    • 10 kWatt * 24 hours per day * 30 days per month = 7,200 kWH per month
    • 7,200 kWH per month * $0.15 per kWH = $1,080 per month electric bill\
    In reality--You probably use more like ~1,000 to possibly 3,000 kWH per month on average (at least during the summer). In general, the average power consumption in the US is around 600 to 1,000 kWH per month, and if you live in areas with high A/C demand (electric heat, electric hot water, electric cooking, etc.) could run 1,000 to 3,000 kWH per month.

    Just to get a line in the sand--Say you want 1,000 kWH per month with a ~6 kWatt Hybrid AC inverter. Can do both "off grid" for power outages--And also do Grid Tied operation (feed solar energy back into grid when AC mains are up--Get some money back from your installation costs).

    Sizing of the battery bank. Using rules of thumbs to get you "close" for planning an optimum system. 2 days of battery storage and 50% maximum battery discharge (for long life):
    • 1,000 kWh per month / 30 days = 33.3 kWH per day = 33,300 WH per day
    • 33,300 WH per day * 1/0.85 inverter eff * 1/48 volt battery bank * 2 days storage * 1/0.50 max discharge = 3,265 AH @ 48 volt battery bank
    Next, sizing the solar array. Two calculations, one based on 5% to 13% rate of charge. And second based on hours of sun you get on average.
    • 3,265 AH * 59 volts charging * 1/0.77 panel+controller derating * 0.05 rate of charge = 12,509 Watt array minimum (emmergency, seasonal usage)
    • 3,265 AH * 59 volts charging * 1/0.77 panel+controller derating * 0.10 rate of charge = 25,18 Watt array nominal (full time off grid)
    • 3,265 AH * 59 volts charging * 1/0.77 panel+controller derating * 0.13 rate of charge = 32,523 Watt array "cost effective" maximum
    And then based on where you live. Using a fixed array for Norman Ok:

    http://solarelectricityhandbook.com/solar-irradiance.html

    Norman
    Average Solar Insolation figures

    Measured in kWh/m2/day onto a solar panel set at a 55° angle from vertical:
    (For best year-round performance)
    Jan Feb Mar Apr May Jun
    3.94
     
    4.21
     
    4.97
     
    5.46
     
    5.37
     
    5.58
     
    Jul Aug Sep Oct Nov Dec
    6.02
     
    5.69
     
    5.31
     
    4.77
     
    4.03
     
    3.69

    Toss the bottom 3 months (assume use genset for bad weather), you get February at 4.21 Hours of sun per day (break even month):
    • 33,300 WH per day * 1/0.52 off grid system eff * 1/4.21 hours of sun = 15,211 Watt array "minimum"
    A 6 kWatt AC inverter would probably run your home and 1 HVAC system + a "normal lifestyle" when off grid. For $4,600.

    http://www.solar-electric.com/inverters-controllers-accessories/inverters/xain/schneider-electric-xw-plus-inverters-accessories/schneider-electric-xw-6848-inverter.html

    A 3,265 AH @ 48 volt battery bank could be made from 4x of these ~$8,100 batteries (each). 2 in series, then 2 parallel strings:

    Crown Industrial Battery - 24 Volts, 1720 Amp-hours

    You can get 12,000 to 32,000 Watt array at ~$1 per watt.

    You would need charge controller(s):
    • 80 amp charge controller * 1/0.77 panel+controller derating * 59 volts charging = 6,130 Watt array per controller max
    So ~2-3 of them at @ ~$700 to $1,600 each.

    http://www.solar-electric.com/inverters-controllers-accessories/chco/schneider-electric-solar-controllers.html

    And you will need solar panel mounts (used to be ~$0.50 per Array Watt--Don't know what it costs now). And wiring. And replace electronics every ~10+ years. Batteries every 10-20 years (those where longer life fork lift batteries I pointed too.

    The links are to our host (I do not work for them or get paid by NAWS) and are there to start your education. In general are good/reliable product at industry "reasonable" pricing. You are welcome to pick other hardware/suppliers--We are an "open source" website who was started and kindly supported by Northern Arizona Wind & Sun. The vast majority of us here are volunteering our time.

    So--Just really round numbers (excluding labor and contractor fees), you are looking at somewhere around $80,000 to $100,000 in hardware costs (don't forget taxes, shipping+insurance) for a 1,000 kWH per month system. A 100 kWH per month system would be roughly 1/10th the cost.

    Just some quick back of the envelope calculations to get you started based on some guesswork on my part.

    Questions?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • westbranchwestbranch Solar Expert Posts: 5,183 ✭✭✭✭
    edited March 2016 #6

    re: the house construction....  Have you investigated Insulated Concrete Forms?  They are extremely effective  and solve a lot of Standard Frame construction issues.  Very strong and very effective at moderating interior temps, which will lower HVAC system power demands.. We used this brand..http://logixicf.com/ based on a comparison of different assembly factors..  Our simple , sort of , basement walls were erected in 2 days, by 3 people...
    hth

     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • solar_davesolar_dave Solar Expert Posts: 2,382 ✭✭✭✭

    re: the house construction....  Have you investigated Insulated Concrete Forms?  They are extremely effective  and solve a lot of Standard Frame construction issue.  Very strong and very effective at moderating interior temps, which will lower HVAC system power demands.. We used this brand..http://logixicf.com/ based on a comparison of different assembly factors..  Our simple , sort of , basement walls were erected in 2 days, by 3 people...
    hth

    There is a house about 2 blocks from here constructed of ICF's and the power bill is substantially lower.  I guess the payback here is like 3 years vs the extra costs. They certainly would make for a good off grid home.
  • westbranchwestbranch Solar Expert Posts: 5,183 ✭✭✭✭
    Based just on the reduction in time and ease of assembly, I would not hesitate to use them again. 
    Just make sure the contractor has experience with them, there are some tricks that one needs to know first...

     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • JoshKJoshK Solar Expert Posts: 232 ✭✭
    edited March 2016 #9
    Hi cotyjewell.  Man, I think I heard a slurping sound while reading your list of loads in the first post :)  I have given a lot of thought to the best way to handle new construction.  One of the solutions I came up with is to use 2 separate panels.  1 would be dedicated to the things you are willing and able to take off-grid entirely (router/modem, lights, etc).  The other for the things you don't care about or are not cost-effective (sorry, the A/C goes here).  Then if the power fails you only lose half the house.  Another cool option that comes with this is having a battery charger available to turn on if the sun hasn't shined in days.  Lots quieter that a generator.
  • westbranchwestbranch Solar Expert Posts: 5,183 ✭✭✭✭
    Look for posts by Mangas, he has a large house that has a solar system for each side of the house....

    here is one about new equipment for HVAC  etc...
    http://forum.solar-electric.com/discussion/comment/351716#Comment_351716

     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • cotyjewellcotyjewell Registered Users Posts: 4
    Thanks for the great replies and information.

    JoshK, we have planned 2 panels and might expand to a third panel.  Thinking of doing 1 panel for electronics, 1 for essential loads and 1 for non-essential loads.  That would allow us to provide battery back-up and isolation to the sensitive electronics and generator backup for the essential loads.  

    Bill, great information.  I spoke to someone local today and he quoted roughly $75k for a system using 64 SolarWorld 285W panels with ground mounts (should generate 18+kW).  He didn't budget as much as you did for batteries though, so he might be a little lean.

    Westbranch, we've already passed the point on using ICF.  Thought about it too late or would've done it.  We saw some information on ICF at a home and garden show in Jan.  Kicking ourselves some over it.

    Appreciate all of the information  Think I have some direction to head now.  Going to meet with the local installer next week to go over the project more.  That'll give me some time to explore everything based on the above recommendations.

    Thank you!
    CWJ
  • JoshKJoshK Solar Expert Posts: 232 ✭✭
    edited March 2016 #12
    One final thought I'd like to leave you with is resale down the road.  If this huge system doesn't have a big override switch, your investment might become a liability when it starts scaring potential buyers.  Hopefully you will have many happy years in it.  But it will be on the market someday.
  • Dave AngeliniDave Angelini Solar Expert Posts: 6,028 ✭✭✭✭✭
    I agree with Josh. I have been involved in a few of these huge projects. The ones with the best chance of completing successfully
    are done in stages or phases. Do you really need all 6,500 square feet to go online with the certificate of occupancy?
    Would you explain a complicated procedure to your patient while they were sedated? Not a great analogy but will the market price of a comparable home justify this dream?
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

  • solar_davesolar_dave Solar Expert Posts: 2,382 ✭✭✭✭
    JoshK said:
    One final thought I'd like to leave you with is resale down the road.  If this huge system doesn't have a big override switch, your investment might become a liability when it starts scaring potential buyers.  Hopefully you will have many happy years in it.  But it will be on the market someday.
    I don't know about that, well down here at least.  You flash that $25 electric bill for May or June and the buyer's eyes do perk up. You show them that there has been minimal down time or maintenance and they like that too.
  • JoshKJoshK Solar Expert Posts: 232 ✭✭
    edited March 2016 #15
    What if they start asking questions and you admit there is only 1 year left on the batteries, and how many thousands of $ to replace them? ouch.  And what if they hate the idea of watering batteries?  Or are just intimidated by electricity and want the ignorance-is-bliss of the grid?
    I would totally build in an over-ride to give them an out at the very least.  AND flash that $25 electric bill. :smiley: 
  • solar_davesolar_dave Solar Expert Posts: 2,382 ✭✭✭✭
    JoshK said:
    What if they start asking questions and you admit there is only 1 year left on the batteries, and how many thousands of $ to replace them? ouch.  And what if they hate the idea of watering batteries?  Or are just intimidated by electricity and want the ignorance-is-bliss of the grid?
    I would totally build in an over-ride to give them an out at the very least.  AND flash that $25 electric bill. :smiley: 
    No batteries here just grid tie! ;)

  • JoshKJoshK Solar Expert Posts: 232 ✭✭
    Alright, but the OP specifically asked about battery backup.  On a huge system.
  • cotyjewellcotyjewell Registered Users Posts: 4
    I don't want this to come across as arrogant, but this home is going to be $1.5-1.6M.  If you can afford to buy that price house, you can afford to replace $30k in batteries...

    CWJ
  • JoshKJoshK Solar Expert Posts: 232 ✭✭
    edited March 2016 #19
    Yea no big surprise here, I caught you were a doctor and also that price doesn't scare you.  But buyers can get a loan to buy the house.  They probably can't get a loan to replace their batteries.  Also, you would be amazed how short-sighted the average person is... they will not spend $30K to save on future electric bills or the planet.  It's just not in the average person.

    I'm not trying to talk you out of installing it.  Do it.  I'm just recommending an override switch/plan.
  • Dave AngeliniDave Angelini Solar Expert Posts: 6,028 ✭✭✭✭✭
    What trackers are you going to use? Outback and Schneider both make systems that will self consume energy if you utility is not offering favorable rates. Plan your sub-panels for the critical loads and really consider using ductless mini-split heat pumps. You will save a ton of energy by going ductless. Even big projects should always keep the "less is more" design principal in mind. Good Luck!
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

  • asadlarik3asadlarik3 Registered Users Posts: 9 ✭✭
    edited March 2016 #21
    for loads that you want to isolate with battery backup for clean power, just go for online ups systems for those loads or check this dedicated equipment http://www.apc.com/shop/us/en/categories/power/audio-video-solutions/av-power-conditioners-with-battery/av-power-conditioners-battery-backups/_/N-1waw8zf. It is best solution for your sensitive equipments. For your solar go for only grid-tie system to lower your energy costs. your generator should be your main backup for all loads, use the battery backup budget on a bigger grid-tie system or/and generator, also it will save you alot in installation costs which again you can use for a bigger grid-tie system or/and generator.
  • JoshKJoshK Solar Expert Posts: 232 ✭✭
    Here's a perfect post about how a buyer can feel when they unwittingly become the owner of a power plant:
    http://forum.solar-electric.com/discussion/350522/im-so-lost
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