Searching For right Inverter

Dear Memebrs
I am living in Pakistan, a developing country, with little knowledge of solar technology. We have access to solar cells but quality inverter suited to our conditions is a problem. Following are the main issues we face.

Abundant sunlight for twelve months.
Regular blackout of utility power hence requiring backup.
Reverse metering option is not provided by Utility power companies hence will like to go for ahybrid solution without supply back to the grid option.
Volatge = 220
Frequency = 50 hertz.

A good inverter preferably sine wave inverter with back up and having hybrid function which can work with out being tied to grid or which doesnot supply power back to grid but can take power from grid is something I am looking for.

An advice in this regard will be great.

Comments

  • stephendv
    stephendv Solar Expert Posts: 1,571 ✭✭
    Re: Searching For right Inverter

    Hi,

    You will need 4 main components for this type of installation:
    - Solar panels with a Vmp and Voc rating that match your battery bank and charge controller limits. You mentioned you have access to solar cells, but it's rarely possible to build reliable panels from cells yourself. More cost effective to buy the complete panels.
    - A charge controller to charge the battery bank, this connects between the solar panels and the battery bank.
    - Deep cycle batteries, batteries used in forklifts tend to be the most cost effective over the long term, especially if you can find them locally.
    - Battery based inverter/charger like this: http://www.victronenergy.com/inverters-chargers/multiplus-12v-24v-48v-800va-3kva/ or this: http://www.studer-innotec.com/?cat=sine_wave_inverter-chargers&id=432 Note that this is a different type of inverter than a "solar inverter".

    If you're starting out, you could get help from a company who installs these systems. Studer-innotec is a swiss company who seem to have 2 resellers in Pakistan who could help you out:
    http://www.studer-innotec.com/?cat=distributors
  • BB.
    BB. Super Moderators, Administrators Posts: 33,590 admin
    Re: Searching for right Inverter

    Welcome to the forum Shafiq.

    Just to be clear--A hybrid inverter (at least as I use the term) is capable of both Grid Tied (feeding power back to the grid) and Off Grid operation.

    And then there are the plain Grid Tied (solar panels + GT Inverter) that feeds back to the grid--Plus the standard Off Grid inverter (battery bank + inverter to feed connected loads, and some way to power the battery bank, AC battery charger from Grid or generator, and/or solar array).

    One of the questions we are always asked is a Hybrid type (or GT Inverter) that can supply power to the home's electrical wiring, but not feed back to the grid. There are some systems that sort of have this function (Xantrex XW series), but so far, it does not seem to do that function very well or accurately.

    So--There is the standard way of doing making local power. A battery bank + Solar array, an Off Grid Inverter, some sort of AC Battery charger (powered by the grid and/or backup generator), and an AC transfer switch. This is just a variation of the typical UPS (uninterruptable power supply) used for computer systems the world over.

    UPS type operations are pretty reliable and efficient... But you cannot use the "excess" solar panel power once the battery bank is full, unless you force a "fail over" to inverter power.

    Running from the battery bank works fine--But tends to cycle the batteries and they may not last as long (cycle life tends to be shorter than float life--standby service).

    In the US, I tend to find that utility power costs around $0.10 to $030 per kWH--While a pure off grid system costs around $1-$2+ per kWH (GT is around $0.10 to $0.30 per kWH and Hybrid systems are around $0.45 to $0.75 per kWH). So, in general, an off grid (or even hybrid) inverter power system costs more to operate vs utility power, and is really only useful for back/emergency power--Particularly in regions where afternoon power outages are common (just setup an AC battery charger from grid, battery bank, and Inverter plus automatic AC transfer switch). Just recharge from grid, and switch over to battery bank for the typical 3pm-8pm blackouts.

    The costs of off grid systems, battery banks (need replacement every 5-8 years), AC Inverter/Chargers/etc. every 10+ years, and battery maintenance/distilled water all make off grid/hybrid systems terribly expensive to supply a lot of power (for A/C, refrigerator, water pumping, etc.). And is difficult to justify from a $$$/kWH accounting point of view.

    So--We always get back to the basics. Use a Kill-a-Watt type meter to measure your current power usage (refrigerators, lighting, computers, heating, etc.) and spend time/money on conservation (insulation, double pane/glass windows, using low power/"green" versions of appliances like laptop computer vs desktop, TV/entertainment systems that are designed to use less power, turn off satellite boxes/digital video recorders/computers when not in use, LED or Florescent lighting, etc.). My own home, and others I have seen can save upwards of 50% of their power usage without too much change in lifestyle.

    Once "extreme" conservation has been implemented--Then look at alternative forms of power. Solar power can be very cost effective in certain applications, especially if you can remove the battery bank from the operation. For example, if you have a well, a solar panel powered well pump slowly filling a cistern/storage tank during the day, and gravity or small pressure/boost pump for home water. Or using solar thermal panels for hot water/home heating (solar thermal collectors, metal tubes+flat plates in insulated glass covered box, etc.) can be good do it yourself projects.

    Also, there are newer technologies that can help. For example there are now electric water heaters that use "heat pumps" (sort of a reverse air conditioner) that take the heat from the air/room and pump it into a hot water storage tank. This can be 2-3x more efficient vs a normal "resistance" heating type water heater. If you have air conditioning already, a "de-super heater" can take the "free" waste heat from your A/C system and heat a water tank too.

    Anyway--my two cents on how I would proceed. What do you think would be good projects for your home/region? And some more reading:

    Thread with lots of projects and information on solar power+conservation

    230 VAC 50 Hz Kill-a-Watt type power meter
    www.theenergydetective.com (example of whole-home AC power monitor system)
    All About off grid Inverters
    Choosing an inverter for water pumping
    Deep Cycle Battery FAQ
    www.batteryfaq.org

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • BB.
    BB. Super Moderators, Administrators Posts: 33,590 admin
    Re: Searching for right Inverter

    By the way, I have merged your threads to keep the responses/conversations in one place. Should be less confusion since both posts ask very similar questions.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • shafiq
    shafiq Registered Users Posts: 2
    Re: Searching for right Inverter

    Thanks for a detailed reply.

    I have been thinking and trying a solution for this issue for quite some time. I have 800 watt q cell panels installed but the inverter keeps on blowing its feds every two months :( it was local inverter and an mppt charger was integrated into it.

    I will like your comments on a model which I have in my mind, I install an mppt charger to charge battery bank, 25 volt system, and install a relay operated with sun switch, when there is sun light it will cut off grid power and when there is no sunlight it will shift to grid power. There are limits of load depending on solar panels installed and inverter capacity, thus forcing to apply such system to essential load in the home with an independent wiring or circuit. An inverter with built in mppt charger and sunlight sensor which gives out 220 volt ac at 50 hertz frequency from a reputable company can serve this purpose, was just wondering if there is one already available in the market so it saves us trouble and will be more reliable. Going for hybrid was to avaoid independant circuit limited to essential loads.

    Anyways thanks for the input. xantrex xw seems interesting but dont know if they have a model which is designed for 220 volts at 50 hertz frequency. If you can refer to one that will be great.
    Regards
  • stephendv
    stephendv Solar Expert Posts: 1,571 ✭✭
    Re: Searching for right Inverter
    shafiq wrote: »
    I have been thinking and trying a solution for this issue for quite some time. I have 800 watt q cell panels installed but the inverter keeps on blowing its feds every two months :( it was local inverter and an mppt charger was integrated into it.

    I will like your comments on a model which I have in my mind, I install an mppt charger to charge battery bank, 25 volt system, and install a relay operated with sun switch, when there is sun light it will cut off grid power and when there is no sunlight it will shift to grid power. There are limits of load depending on solar panels installed and inverter capacity, thus forcing to apply such system to essential load in the home with an independent wiring or circuit. An inverter with built in mppt charger and sunlight sensor which gives out 220 volt ac at 50 hertz frequency from a reputable company can serve this purpose, was just wondering if there is one already available in the market so it saves us trouble and will be more reliable. Going for hybrid was to avaoid independant circuit limited to essential loads.

    Anyways thanks for the input. xantrex xw seems interesting but dont know if they have a model which is designed for 220 volts at 50 hertz frequency. If you can refer to one that will be great.

    Xantrex XW comes in a 4kW and 6kW version and 220V 50Hz. Both of the battery inverters I mentioned in my first response are 220V 50Hz.
    All of them will do what you want, except that they use the battery voltage to determine when to switch to grid, so there is no need for a relay activated by solar. They can also be programmed to switch to the grid if the peak current is above a certain value.