Home Refurb

My wife and I may be purchasing a new (to us) home in the northeast of Chicagoland and should have the opportunity to do some customization, but the house is at the upper limit of our budget, so we have to be careful how much we do now.

I'm involved with tech industries so having a reliable source of clean (not necessarily green) power is important to me. Having some lights, fridge/freezer that won't defrost, and enough A/C so our pets don't get too hot is important to both me and my wife.

Currently we are looking at installing solar hot water with an option to have it help heat the house via the existing forced air system later. However thats a fairly easy choice with only a comparitivily small investment.

More importantly, I need to have UPS power for some areas of the house and generator power for those areas plus a little more. However we also want the option to add PV and wind later down the line. So we would like to install equipment that would support on-line service plus generator with a battery backup that can be charged via line. Later we want to switch it so the batteries are only changed via wind/solar and excess power can be fed back into grid. Any suggestions on equipment? The current service is 200amp, and I wouldn't be suprised if we ended up with an 8k to 15k watt generator. Although I can't image us pulling that much even with A/C.

Thanks in advance.

Comments

  • BB.
    BB. Super Moderators, Administrators Posts: 33,432 admin
    Re: Home Refurb

    Short answer--looking at the costs of power, installation, and maintenance/fuel...

    0. Utility power for Chicago reported at $0.084 per kWhr
    1. solar thermal (hot water, heating)
    2. solar Grid Tie (maybe $0.30 per kWhr--without rebates/tax credits)
    3. solar hybrid--GT+off-grid emergency power (~$0.50 to $1.00+ per kWhr)
    4. Generator--just fuel costs will be $1.00-$5.00 per kWhr...

    I like to roll the costs out as $/kWhr just so you can decide where to throw your money...

    Conservation, conservation, and reduced energy use/needs are your first three points to spend. Depending on the age of your home, upgrades, appliances, and such--you need to see how much power you are currently using and how much you want to spend on conservation (in rough order of spending priorities; ceiling/wall insulation, sealing air leaks--doors/windows/heating ducting, double/triple pane windows, floor/crawl space insulation, energy efficient heating/cooling, appliances--fridge, freezer, lighting, home electronics).

    And, you have to decide how much "emergency power" you will need (how many watts, how long, type of power--i.e., continuous switching UPS, standby UPS, generator).

    As you can see--just plain old Grid Tied solar+inverter it the most cost effective... If you can run 90%+ of your home on that, and reserve the "expensive" power for those places where it is needed (computer, emergency lighting, heating, fridge/freezer). Because, each time you go through a UPS (for backup power), you throw in another 5-20%+ in losses (increased power bill, increased cooling loads in summer).

    And if you get a 10kW+ generator--you will find that power even small loads--they still suck down the fuel like there is no tomorrow (a good diesel or prime power type genset may be more efficient at low end loads).

    For example, a little 12kW home system uses between 103 and 191 cuft of natural gas per hour (25% and 100% load)... Or for LPG, 1.2-2.4 gph for 1/4 to 100% loading. What is that in LPG costs??? Something like $4-$8 per hour? It may be worth it for an emergency--but only you can decide how much fuel you can store and how much you want to spend (~~50 gallons per day, for two weeks = ~700 gallons of LPG). Plus $5,500 for the generator plus permit, installation, and LPG tank costs (or use natural gas if available for your area at 25%-50% the fuel costs of LPG???)

    As an example--I choose to get a Honda eu2000i (1,600 watt) portable generator for $900. My loads are probably an average of 400 watts (fridge, freezer, a few lights, sump pump, radio/tv). The Honda (set in ECO mode) will average about 1.1 gallons of fuel for 15 hours.... Much cheaper, and much less fuel to store for 2 weeks of power emergency (~14-28 gallons--just siphon from car and a few gas cans with preservative).

    Similar issues if you want a full battery backed grid tied system--the more power you want for backup--the larger the batteries required. And batteries have a lifetime too (~7-15 years), plus maintenance and charging losses.

    If you want to look at a very nice hybrid GT with off-grid backup--look at the Xantrex XW system.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Brock
    Brock Solar Expert Posts: 639 ✭✭✭✭
    Re: Home Refurb

    Shibasun take a look at my www.uwgb.edu/nevermab/solar.htm web page. It sounds like you want something similar to what we did. I started small and just now switched over to a larger 48v system with a 6000w 120/240 inverter. I would suggest starting with standalone / grid tie compatible inverter like the Xantrex XW or an Outback or something similar. I would go bigger then you think so you can grow in to your inverter. Start with maybe 4 golf cart batteries to get your feet wet. Then as you go you can add a good charge controller, again go with a larger one so you can keep adding rather then upgrading the charge controller as you grow and finally adding solar panels to the system.

    While I totally understand Bill’s point about going grid tie for financial reasons, I just can’t help myself from having a HUGE UPS for my house at the same time ;) The advantage of the gird tie inverter like I have is once my batteries get full the rest of the power is just fed to loads downstream of the inverter or if it isn’t being used it can push it back upstream out to the grid (if your approved to do that). I can also run a genset to top of the batteries in the event of an outage, but shut of the genset over night and still run any necessary loads. This does come at a cost of dropping efficiencies from the solar panels from in the low 90’s to mid 80’s. Mostly stand by battery losses and of course adds the cost of the batteries and eventually battery replacement as well. I would hate to have 2000w watts of solar on the roof and have no power in an outage ;)

    As to the type of generators it is hard to beat the newer inverter style gensets like the Honda eu2000i or Yamaha EF2400i both are really quiet and about as efficient as you can get with fuel without going to a larger diesel genset.

    If I had nothing my first purchase would be a Honda 2000i. My second purchase would be a 12v sine wave inverter large enough to run a fridge & freezer that I could hook to my car battery and if I had to idle the car to keep it running.
    3kw solar PV, 4 LiFePO4 100a, xw 6048, Honda eu2000i, iota DLS-54-13, Tesla 3, Leaf, Volt, 4 ton horizontal geothermal, grid tied - Green Bay, WI
  • BB.
    BB. Super Moderators, Administrators Posts: 33,432 admin
    Re: Home Refurb
    shibasun wrote: »
    ...but the house is at the upper limit of our budget, so we have to be careful how much we do now.

    ...comparitivily small investment.

    The reason I was typing about what is "cost effective"... :cool:

    I too like the XW type system--a hybrid Grid Tie and Off Grid system... But the batteries make it very expensive to install and maintain vs the virtually non-existent power outages we have here (maybe a minute once every year or so--or an hour or two once a decade)... To be "green", to me, includes the best use of resources for the job at hand.

    And, for now in my area (SF Bay Area), that is a GT solar plus a genset (also a Honda eu2000i) with 20 gallons of fuel in storage (rotate once a year into my car--so no "extra waste" there).

    However, if I lived in an area with lots of ice storms, hurricanes, etc., where power is out for several weeks or longer and I have need for heat/AC (climate extremes), my choices would probably be different.

    I too hate the idea that my solar panels are just a "glass umbrella" during a power outage... But until Solar Guppy designs and sells that 200-600 VDC input standby solar charge controller (GT inverter voltage compatible)--that is all they will be (short of a 3kW inverter back-fed from a GT inverter with a battery bank and shunt load).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Solar Guppy
    Solar Guppy Solar Expert Posts: 1,989 ✭✭✭
    Re: Home Refurb

    I won't be designing a HV charge controller ... for my current home, if we get a big one that knocks out power for more than a few hours, with the flip of a breaker my 12kw PV ( two Xantrex GT5.0's and a Xantrex GT3.3 ) can backcharge/backfeed the XW-6048's output which will charge the batterys AND run the AC ( as well as the entire home )

    I do have my prototype SC-60's on 5kw of solar that can charge via low voltage ( 100 voc ) but the remainer of the PV is all High Voltage Strings

    With a street price of 2700 on the XW-6048, it's cheaper to back feed via the GT's ( to charge the battery banks ) than have dedicated charge controllers and I beleive that is the direction the market will take an improve this function/feature to be better supported by the XW's

    Even with the battery banks ( 600ah/48V and the XW price ), its a cost effective whole house backup , about 6k, that can run unlimited as long as I get good solar days to recharge the batterys with my oversized solar installation
  • System2
    System2 Posts: 6,290 admin
    Re: Home Refurb

    Thanks for the replies. I used that information to figure out what we wanted to do, however the house didn't work out so I won't be able to apply any of those concepts now. Hopefully in the next year or two, we will either find another house we feel is perfect (with a few changes) to us, or be able to build our own dream home which is green from the foundation up.

    I have saved the thread and the info just in case this thread isn't here when I need it again, and I'm going to try to stay on top of things for the next year so we are ready to go when the situation allows.

    Thanks again!