Small Inverter

Does the Grid Tie market offer a small inverter that rides the grid through a 120vac duplex receptacle and inputs between 500-1000 watts ? I would like to tie several small PV panels into the thing and be able to recover this small amount of power without purchasing a huge amount of gear and not use a string of batteries.

Comments

  • System2System2 Posts: 6,290 admin
    Re: Small Inverter

    thes nothing affordable. sunnyboy makes the smallest grid tie inverter available (900w or 600w i forget) and as i recall it required the panel voltages to be at a certain level to function. for example i have three sharp 175w panels, and as i recall i would have to geta 4th sharp and series them all for it to work. also, i highly doubt it is a standard plugin AC receptacle but the docs did say it could be placerd anywhere in the house, implying should shouldn;t need to do much wiring to dirtectly tie it in. l0ook into the small sunnyboys they will list exact specs.

    there was a thing called the OK4U that did what you wanted for about 100w i think it was, but they were exhorbitantly priced and discontinued. (try ebay)

    ALSO i saw in recent ,months a new panel out (that i posted a thread about here, can;t recall brand) that had an integrated griod tie ac inverter, but it also was prohibitively expensive.

    -Matt
  • BB.BB. Super Moderators, Administrators Posts: 29,696 admin
    Re: Small Inverter

    There would be several legal reasons why you would not find such a system for the US (or probably anywhere else).

    1. It is not safe--Standard wall outlets are required to be protected by a 15-20 amp fuse. A thousand watt system will add almost 10 more amps to a branch circuit. Too much current would be available to other appliances and home wiring plugged into other outlets on the same branch circuit. Overloads could cause a fire and other problems.

    2. Solar panels are installed outside and subject to lighting and other electrical sources. Solar panels need to be properly (and permanently) grounded or there will be a shock/fire hazard.

    3. Since panels need to be physically attached to a roof or ground mount to ensure that they are not blown around in storms, the mounts(especially) are usually checked by building inspectors to ensure that they (and the structure) are safe.

    4. Any permant electrical system needs to be installed per code. It is against the fire code (in many areas) to connect, for example, a fan to the wall and run an extention cord to a wall outlet.

    5. The electric utility requires the system to be code inspected and insurance to be supplied by the owner. They don't want unknown/unapproved systems connected to their systems for concerns of electrocuting their linemen with improperly connected equipment. Also, a lockable and labeled switch needs to be installed outside the home to turn off the solar grid tied system. If they don't know about your system, they can turn it off when needed. If they know about your system, they will lock off your main power (or cut your utility connection) if needed. In some cases (at least in California), a very few downtown cities have (I am guessing here) "matrix" connected power systems for redundancy (and maybe power sharing from different power feeds). They have protection against reverse energy flow and will open breakers if reverse power flow is detected (a small solar PV system obviously won't make a difference, but it is in their terms of service to prevent net generators in those areas).

    6. The utilities really don't want generators connected to their system. Government(s) have forced them to allow "green" power connections under certain rules (billing, insurance, safety, locking points, total attached "micro" generators to their grid, etc.). Attaching systems without approvals are illegal. If they find your meter going backwards, they will disconnect you (at the very least).

    In reality, Grid Tied systems are not that expensive to install a new circuit breaker and dedicated branch circuit for your system (when compared to the costs of the panels and inverter). If you have a specialized need (such as mounting your solar panels/inverter on a trailer that you can haul from your winter to summer home), you might be able to get approval to install a dedicated branch circuit/outlet to your outside wall to connect a portable equipment. Or just install an exterior junction box to connect your small system and get it over with.

    If you want to only connect a 100 or 200 watts to your branch circuit, there are those panels with dedicated "micro" grid tie inverters would be a close as you could get to a minimum "pluggable" type system. At a 100-200 watts, it is small enough that it would rarely turn your meter backwards or that one or two panels would attract much attention of the city or utility. You still will have many of the same issues as detailed above (safety and legal)--just to a smaller degree and less likely to get caught or have fewer nasty surprises..

    There is one solar panel manufacturer that attaches a small grid tie inverter to the back of each panel. It sounds ideal (other than being more expensive than a normal panel with external inverter installation) for what you want to do--but I don't remember their name, and have not found a link for them yet... Somebody else here will probably have the link. For larger installations, a dedicated grid tie inverter is probably the best way to go...

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • crewzercrewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    Re: Small Inverter

    Bill,

    I believe you're thinking of Exeltech's PV AC Modules. As best I can tell, they are still "vapor ware".

    Regards,
    Jim / crewzer
  • BB.BB. Super Moderators, Administrators Posts: 29,696 admin
    Re: Small Inverter

    Jim,

    That there be what I was thinking of... Sounds like a nice idea, but probably not cost effective in the long term (life of panel and electronics--especially exposed to weather, frequently don't have the same life time and one may be forced to junk one part of the system or the other--electronics or solar panels).

    MG,

    I am sorry I posted so much on the issue--It is that there are many issues when working with utility power and home wiring. And the reasons for some regulations are not always obvious as to why certain things are not allowed... The engineer leaked out of me in that post.

    I did find one company that appears to make a small 120 watt grid tie inverter--but it is on a Netherlands site--so I don't know if it is available for the US:

    http://www.zonnepanelen.wouterlood.com/solar_pages_uk/inverters.htm (Soladin 120 manufactured by Mastervolt)

    In the end, the 1-4kWatt inverters are running around $0.50 per watt (+/-) and the solar panels are running about $5.00 (+/+) a watt retail... So getting an oversided grid tie inverter is not going to be the most costly part of the system.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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