Moving the (battery) goalposts ...

lasitter
lasitter Solar Expert Posts: 56 ✭✭
After moving into my grid-tied house, I lost power very soon for 30 minutes. I was afraid this would happen frequently, so I immediately began planning for significant investments in batteries and gensets.

I learned (here) that carrying the house for a long time with batteries was an expensive proposition. But no matter which you choose (batteries or generators) you're looking at competing costs for maintenance / fuel and eventual component replacement cost.

We've basically not lost power for more than a few minutes since, so I'm trying to approach the problem differently -- by moving the goalposts.

The question I'm framing is now this: If I wanted to support the house in the event of grid failure for only 1-3 hours, three times per year, with an average load of 1.5 kwh and a peak of 3kw, what would that take in terms of AGM batteries?

http://www.solar-electric.com/batteries-meters-accessories/batteries/unba/unba200amagm.html

Four of these gives you 48 volts, and you could double (parallel) them to double your staying power.

Four or eight of these is not a lot of money battery-wise. They are supposed to be relatively low maintenance and they don't produce hazardous gasses like wet batteries, so I could keep them in the basement where they'd be relatively warm and therefore more effective in the winter.

In the event of a grid failure in the summer, they'd only have to carry the system in the daytime when the sun ducked behind a cloud.

I could always add a genset later, but does this sound like a reasonable start as I prepare for the install of the PV panels?

Also: These batteries would basically have the easiest life possible. Most people talk about replacing them every 5-8 years, but I was hoping I might get something better with this kind of treatment. Care to hazard a guess?

Comments

  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    lasitter wrote: »
    ...

    In the event of a grid failure in the summer, they'd only have to carry the system in the daytime when the sun ducked behind a cloud.

    Unless you install a complicated hybrid system, your GTI panels will not be producing any power while the grid is out whether the sun is shining or not.
    An SMA mixed system of Sunny Boy and Sunny Island units would be capable of doing what you want, and with a relatively small capacity battery pack IF they are very low internal resistance, like some AGM and some Lithium chemistries.
    SMA SB 3000, old BP panels.
  • westbranch
    westbranch Solar Expert Posts: 5,183 ✭✭✭✭
    Are the outages prdictable or random? Predictable: you could just use a genset, Random: you will need a basic OG setup designed to meet those peak needs... With Li chemistry, you could do a 75% depletion calculation, FLA or AGM you could go to ~ 50% depletion safely...'
    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
  • lasitter
    lasitter Solar Expert Posts: 56 ✭✭

    inetdog wrote: »
    Unless you install a complicated hybrid system, your GTI panels will not be producing any power while the grid is out whether the sun is shining or not.
    I am definitely thinking about a hybrid inverter -- an off grid AC inverter with the capability to operate in Grid Tied mode. I think it would be an AC2 system, that would allow for the addition of a genset eventually. I want it to automatically flip over on mains failure to providing power to protected circuits.
    Any reason a setup such as this could not usually operate in a mode which allowed for the earning of sRECs and net metering?


  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    lasitter wrote: »


    I am definitely thinking about a hybrid inverter -- an off grid AC inverter with the capability to operate in Grid Tied mode. I think it would be an AC2 system, that would allow for the addition of a genset eventually. I want it to automatically flip over on mains failure to providing power to protected circuits.
    Any reason a setup such as this could not usually operate in a mode which allowed for the earning of sRECs and net metering?


    Nope. No reason at all as long as you are willing to spend the extra money. Look for a hybrid inverter with good generator support if that is likely to become important to you.
    SMA SB 3000, old BP panels.
  • westbranch
    westbranch Solar Expert Posts: 5,183 ✭✭✭✭
    One of the outback models that would fit your needs was the GVFX and GFX, but they recently made some changes to it and it is now IIRC theFXR http://www.outbackpower.com/index.php/outback-products/inverters-chargers/item/fxr-renewable-series-120v-a-models?category_id=444
     
    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
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    There has been one utility (a few years ago in southern California? ) that was giving problems to battery backed hybrid inverters running in gt mode.

    Make sure your utility will let you connect and get a good gt solar plan.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Johann
    Johann Solar Expert Posts: 245 ✭✭✭
    I bought a house also that lost power very often about every 1 week to every 2 weeks from 4 hrs to 12 hrs.
    The first thing I got was a inverter and I put a 175 amp plug on the car battery and a plug that was made for fork lifts on the inverter. This way I could have power in minutes, in case of power loss to tie me over. I had many household items hooked up to the inverter like electric skillet, microwave and tools like circular saw etc. You should had seen people stopping at the road to watch me plug my orange 120volt cord ''into my car'' and use my circular saw and other power tools at the road to fix my wooden mail box post.
    A car alternator will not put out 1.5 -3 kw that you will need, but could tie you over with less power.
    If you lose power only a few times a year and want battery backup, why not use a grid powered battery charger and charge those batteries with an charger? Way cheaper than a complete solar system.

    A generator would be cheaper and you still would have money left to buy fuel for the generator instead buying those 8 batteries. You have to remember that those batteries will start to go bad as soon as they are made and it does not matter if they have an ''easy life''. Those batteries may be maintenance free but there is no way to check those batteries properly for faults to take preventive actions etc before they get damaged and die. Unvented batteries still need to be placed in an area that is vented because overloading and overcharging batteries may still put hydrogen into the air and in your case the basement. 6oz of gas-form hydrogen will rattle all your windows and doors when ignited inside your home,...ask me how I know this.



  • lasitter
    lasitter Solar Expert Posts: 56 ✭✭
    So if you used a panel compatible with the sunny Boy 8000TL, would that be the right unit to handle 8kw in panels, and what charge controller would you need?

    (Several of the SMA model numbers are similar, so I'm not certain of this ...)

    I'm confused about which of these (if either) I should be looking at ...
    http://www.wholesalesolar.com/products.folder/inverter-folder/SB8000US.html
    http://www.wholesalesolar.com/products.folder/inverter-folder/Sunny-Boy-8000TL-US.html

    And with 32 panels, which of the SMA combiner boxe would you need?
    So if you used a panel compatible with the sunny Boy 8000TL, would that be the right unit to handle 8kw in panels, and what charge controller would you need?

    (Several of the SMA model numbers are similar, so I'm not certain of this ...)

    And with 32 panels, which of the SMA combiner boxe would you need?


  • lasitter
    lasitter Solar Expert Posts: 56 ✭✭
    Johann: With PV you get the tax credits and sRECs and the whole thing pays off in a little over four years. After that the sREC income is "found money", and after 10 years you still get net metering.

    I haven't heard about safety concerns you mention regarding AGM batteries.

    The generators I'm considering would run from $5k to $10k installed, depending on the manufacturer and whether I went with natural gas or diesel. That would pay for more than a few batteries. I don't really need diesel, but I love the idea of the quiet reliability of a Perkins genset and how long it could run on the 660 gallons of fuel oil in my basement, if it really had to. I'm not sure how hard people with natural gas generators really push them and then, if they do, how long they last.

    A generator could be a luxury entirely except for the fact that the next town south of here caught a tornado in 2011 that left some people without power for a month. During some natural disasters (earthquakes, Hurricane Sandy) emergency management officials disconnect service in wide areas while attempting to repair delivery networks. While very unlikely, having your own supply of fuel can be very helpful.
  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    lasitter wrote: »
    So if you used a panel compatible with the sunny Boy 8000TL, would that be the right unit to handle 8kw in panels, and what charge controller would you need?

    (Several of the SMA model numbers are similar, so I'm not certain of this ...)

    I'm confused about which of these (if either) I should be looking at ...
    http://www.wholesalesolar.com/products.folder/inverter-folder/SB8000US.html
    http://www.wholesalesolar.com/products.folder/inverter-folder/Sunny-Boy-8000TL-US.html

    And with 32 panels, which of the SMA combiner boxe would you need?
    So if you used a panel compatible with the sunny Boy 8000TL, would that be the right unit to handle 8kw in panels, and what charge controller would you need?

    (Several of the SMA model numbers are similar, so I'm not certain of this ...)

    And with 32 panels, which of the SMA combiner boxe would you need?


    The Sunny Boy is a pure grid tie inverter which will not work without grid power present and will not interface with batteries (too low a voltage.)
    The Sunny Island is pure off grid inverter which can be used to provide a off-grid power from batteries and requires a separate charger to charge the batteries.
    By pairing one SB and one SI you get a hybrid system in which the SI can produce a "dummy" grid power source that provides power at night and also allows the SIs to contribute during the day.
    You cannot connect one set of panels at the same time to a battery charger (CC) and to a Grid Tie Inverter (GTI.)
    SMA SB 3000, old BP panels.
  • lasitter
    lasitter Solar Expert Posts: 56 ✭✭
    inetdog: OK, so I'm working to understand this ...

    http://www.outbackpower.com/index.ph...ategory_id=444
    http://www.outbackpower.com/outback-...-230v-e-models

    Would either of these function in as the all-in-one that's been mentioned?
    You cannot connect one set of panels at the same time to a battery charger (CC) and to a Grid Tie Inverter (GTI.)

    Could anyone here provide me with a kind of diagram showing how all the pieces would work with one another? In particular which SB / SI components I should be looking at to support 8kw of panels, combining, charging, etc.?
  • lasitter
    lasitter Solar Expert Posts: 56 ✭✭
    inetdog wrote: »
    You cannot connect one set of panels at the same time to a battery charger (CC) and to a Grid Tie Inverter (GTI.)
    So there is no setup of components that can take power accumulated from the panels and seamlessly provide some of it to a charging function, some of it to loads within the house, and the rest to the grid?
  • verdigo
    verdigo Solar Expert Posts: 428 ✭✭
    lasitter wrote: »
    So there is no setup of components that can take power accumulated from the panels and seamlessly provide some of it to a charging function, some of it to loads within the house, and the rest to the grid?


    A hybrid inverter system will do just that. It will function as a GT system untill the grid goes down and function as a off grid system until the grid is restored. Outback's FXR series inverters have generator support and can also be set up to run preferring RE sources while cycling batteries and use the grid to supplement when the sun is less than optimum.
  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    verdigo wrote: »


    A hybrid inverter system will do just that. It will function as a GT system untill the grid goes down and function as a off grid system until the grid is restored. Outback's FXR series inverters have generator support and can also be set up to run preferring RE sources while cycling batteries and use the grid to supplement when the sun is less than optimum.
    You would just have to have an AC powered CC to keep the batteries charged if using SI/SB.
    You cannot use a DC (panel) powered CC and a panel powered GTI unless you switch the panels between the CC and the inverter. Some hybrid inverters (e.g. Xantrex) take battery power to run the GTI function and can also take AC from the same grid connection to recharge the batteries. The panels would connect directly via CC to the batteries.
    You could also divide your panel array up into to subgroups for the SI/SB case.
    SMA SB 3000, old BP panels.
  • lasitter
    lasitter Solar Expert Posts: 56 ✭✭
    http://www.altestore.com/store/Packaged-Systems/AC-Coupled-Systems/Outback-Power-8000W-FLEXcoupled-AC-Coupled-Package/p11117/

    I was talking with an Outback factory rep today and this kit looks like it would have most of the big pieces. Looking at this "book of materials" ...

    1 GS8048A
    1 GSLC175PV1-120/240
    1 MATE3
    1 FW-MB3
    1 HUB 10.3
    2 FM80-150VDC
    1 FW-CCB2

    Optional:
    1 FWPV-12
    12 DIN-15-DC

    It looks like the Hub 10.3 and charge controllers would be extra.

    Would this system default to using power stored from the PV array at night?
  • Sulfur
    Sulfur Solar Expert Posts: 62 ✭✭
    Sunny Island is a 48VDC to 120VAC inveter AND a 120 VAC to 48VDC battery charger. Advice on SI in others earlier posts is wrong. With a SB and SI you can charge batteries, and feed house loads and grid with 240VAC all at same time. SB produces the 240VAC from ~450VDC coming from panels. If wanting to power 240VAC devices with SI in off grid state, you will need 120VAC to 240VAC transformer. The inverter portion of SI is only used when grid is down.