Uninterruptible Power Supply using solar?

levsmith
levsmith Solar Expert Posts: 56 ✭✭
Hey everyone,

I am in the process of buying a house and have been interested in solar for a while now. Hopefully I will get a chance to try it out once I get out of the apartment!

Anyways, the house has a basement and of course a sump pump. I am curious if anyone knows of an uninterruptible power supply that can be used with an off grid system. I will be out of town some weekends and the house is in the boonies so the main thing I am worried about is a heavy storm that knocks out the power and floods the basement all while I'm gone. So my thought is to get a little off-grid system to play with and experiment to run some smaller stuff while I'm there and when I'm gone it can serve as a battery backup for the sump pump. I know you can get battery backup power supplies for computers that automatically kick in when the main power goes out and that is kind of what I am looking for but on a bigger scale. What I am imagining is something that plugs into your wall and also into your inverter, runs on mains until it goes out and then switches to pull from the inverter. Does something like that exist?

Thanks for any help!

Comments

  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Uninterruptible Power Supply using solar?

    There are many ways to achieve UPS for either a single device or indeed the whole house. It is a matter of scale, which of course means money.

    Since the sump pump is likely 120 VAC, its power can simply be part of the inverter-backed circuit. This can be designed with or without solar recharging of the batteries.
  • levsmith
    levsmith Solar Expert Posts: 56 ✭✭
    Re: Uninterruptible Power Supply using solar?
    There are many ways to achieve UPS for either a single device or indeed the whole house. It is a matter of scale, which of course means money.

    Since the sump pump is likely 120 VAC, its power can simply be part of the inverter-backed circuit. This can be designed with or without solar recharging of the batteries.

    Thanks for the reply Cariboocoot. Can you go into a little more detail on the inverter-backed circuit? Unfortunately I dont have a system yet so I dont know much more about them than the basic function of how the system as a whole works.
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Uninterruptible Power Supply using solar?

    The most common system of this sort uses an inverter-charger. When AC is available from the grid the inverter-charger uses the power to maintain the batteries; loads are 'passed through' to the grid. When the grid goes down the inverter-charger takes over supplying AC power to the loads. Solar can be added to keep the batteries charged if the grid outage is extended.

    A more expensive but somewhat more practical system is the hybrid grid-tie system, which uses batteries for back-up power and can sell 'surplus' output from the solar panels to the utility.

    Another idea is to have the off-grid inverter available as a "back up generator" using a automatic transfer switch to change the load from grid to inverter in the event of a grid outage.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Uninterruptible Power Supply using solar?

    Or you go with a simple (and cheap) 12 volt or 24 volt DC marine sump pump... Of course, there are very high quality and expensive sump pumps too.

    And even domestic water powered sump pumps too.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • levsmith
    levsmith Solar Expert Posts: 56 ✭✭
    Re: Uninterruptible Power Supply using solar?

    Ok. Your third idea is more like what I was thinking, at least until I get a big enough system to make it cost effective to go grid tie. I guess I am looking for a small automatic transfer switch that you could run just a few things from. The only automatic transfer switches I have seen in the past are very big and have to be put in by an electrician. I am thinking very small scale, like a smart power strip with 2 plugs, one to pull from the main utility and one to pull from the inverter, that will switch automatically.

    Thank you for your help. I dont know why I didn't think of searching for a small automatic transfer switch but I was able to find a 30 amp for for $200. I'll keep looking to see if there is anything else. Thanks again, you got me going!
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Uninterruptible Power Supply using solar?

    You can get a 30 amp transfer switch for around $60. These types of transfer switches have a ~20-30 second delay to allow a generator to start and stabilize before transferring power.

    Or, you can even just purchase a Relay with the coil powered by the AC mains... If the mains fail, the relay fails over to the AC output of an inverter.

    There are lots of ways of doing this stuff (including big transfer switches with generator remote control, weekly cycling, etc.). And there are AC inverters that have the transfer switches built in.

    A lot of this depends on your needs and power requirements.

    This website by poster 2manytoyz has lots of pictures and discussions (near bottom of page, on right) about his emergency power backup systems (solar+batteries+genset). Most if it is DYI so you can see how the pieces play together.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Uninterruptible Power Supply using solar?

    For a very small, 'single circuit' 15 Amp switch you might have to build it yourself: double pole relay capable of handling the current load held closed by grid AC. Grid goes down, relay releases, loads switch from grid to inverter.
  • levsmith
    levsmith Solar Expert Posts: 56 ✭✭
    Re: Uninterruptible Power Supply using solar?
    BB. wrote: »
    You can get a 30 amp transfer switch for around $60. These types of transfer switches have a ~20-30 second delay to allow a generator to start and stabilize before transferring power.

    Or, you can even just purchase a Relay with the coil powered by the AC mains... If the mains fail, the relay fails over to the AC output of an inverter.

    There are lots of ways of doing this stuff (including big transfer switches with generator remote control, weekly cycling, etc.). And there are AC inverters that have the transfer switches built in.

    A lot of this depends on your needs and power requirements.

    This website by poster 2manytoyz has lots of pictures and discussions (near bottom of page, on right) about his emergency power backup systems (solar+batteries+genset). Most if it is DYI so you can see how the pieces play together.

    -Bill

    Thanks Bill. I checked out those transfer switches and it doesn't really look automatic to me. From the instructions, it basically says you turn on your alternative power and it will switch sources. If I'm not there, it wouldn't work automatically correct?

    Also, thanks for the link to 2manytoyz. Looks like a great website and something to keep me busy for a while!
    For a very small, 'single circuit' 15 Amp switch you might have to build it yourself: double pole relay capable of handling the current load held closed by grid AC. Grid goes down, relay releases, loads switch from grid to inverter.

    Now this sounds interesting. Unfortunately I dont have any experience with building stuff from scratch, only repairing, so I would have no clue where to start on something like that. Although it does sound like it is very simple. I am always up for learning if someone is willing to teach! It will be a few months before I have to the money to get into solar but sounds like something I would like to try when I do.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Uninterruptible Power Supply using solar?

    The answers is "it depends"... For example, you can get an AC Inverter that has "Search Mode"--Basically, the inverter pulses the AC line once a second looking for a >6 watt load. If it finds one, it turns on full time (until the loads "go away").

    So--You can use a simple transfer switch/relay connected to the 120 VAC AC Main, and the inverter connected to the backup contact(s). When AC Main fails, the relay fails over to the inverter output and starts the inverter up.

    Of course, there are some inverters that have remote On/Off switches too... So, you could have a multipole relay also turn on the inverter directly and such.

    For a smaller AC system, the MorningStar 300 watt TSW 12 volt inverter is really hard to beat. It has both search mode and remote on/off configurations... And so far, has proved to be a rugged/reliable unit (many people around here use them--I do not have any off grid systems--Mine is Grid tied).

    People have used the simple relay approach for an RV (shore power / inverter power), and for a more simple generator approach (cabin powered by inverter, manual pull/electric start genset switches to AC power and AC Battery charger for poor weather conditions).

    Very simple, low(er) cost system. Of course, you can spend a bit more for larger power output and more options.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Photowhit
    Photowhit Solar Expert Posts: 6,002 ✭✭✭✭✭
    Re: Uninterruptible Power Supply using solar?

    While you need an inverter/charger for the first senerio to work usually, there are also pass through inverters like the prosine 1800 and 1000, some of the hardwire models have an internal transfer switch, they were originally made for marine use.
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
  • levsmith
    levsmith Solar Expert Posts: 56 ✭✭
    Re: Uninterruptible Power Supply using solar?

    Ok just an update. I looked and looked at 2manytoyz website last night and couldn't find anything about building a simple automatic transfer switch so I decided to just search google tonight "for build an automatic transfer switch" and his was the third result. I'm not sure how the 2manytoyz site is mapped but just in case anybody else happens to come across this thread looking for the same thing, here is the link. http://2manytoyz.com/ats.html

    Anyways, thanks again for all of the help guys. What he built was almost exactly what I had pictured in my head but just didn't know what the internals would be. I'm sure I'll be back as I start experimenting!