How PV grid-tie inverters can zap utility power factor

mike95490mike95490 Solar Expert Posts: 8,490 ✭✭✭✭✭
(I thought I posted this a couple of days ago, but can't find it)


This article is from Photovoltaics World

http://tinyurl.com/GTI-PowerFactor-Woes

How PV grid-tie inverters can zap utility power factor

by Gerritt Lee, contributor

The rush to harness energy from the sun to make electricity has inevitably fueled the development of large industrial-grade grid-tie inverters (GTI) that convert DC from photovoltaic (PV) panels into AC power for commercial use. Compared to their residential forerunners that generated only a few kilowatts (kW) of power, the mammoth systems of today are designed to put out upwards of 100kW. While these super-sized powerhouses can dramatically lessen reliance on utility power, there is something else they do that may surprise you.

Customers with PV systems that have displaced a good portion of utility power and whose loads have a sizable reactive component can actually see utility power factor deteriorate after their system is connected to the grid. Low power factor presents a heavier generation and transmission burden on the power grid and also deposits a larger carbon footprint. Because of this, most tariffs have provisions allowing the utility to charge a penalty for low power factor. But it is possible to address this problem.

..... The missing piece of the puzzle is the fact that GTIs are designed to operate with a unity power factor output and be synchronized with grid frequency. Recall that a system with unity power factor exhibits 100% real and 0% reactive power. So the GTI does not contribute any reactive kVar production to the equation, which leaves the utility to bear the entire burden. The reason for the mysterious drop in power factor now becomes clear.



So, does anyone know if this is a factor/problem with small scale (homeowner) systems, or does the transformer inside solve/correct this ?
Mike
Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
|| Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
|| VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

solar: http://tinyurl.com/LMR-Solar
gen: http://tinyurl.com/LMR-Lister ,

Comments

  • icarusicarus Solar Expert Posts: 5,389 ✭✭✭✭
    Re: How PV grid-tie inverters can zap utility power factor

    Mike,

    I believe we had a very lively thread on this subject about 4 months ago. I would do a search, but my satellite connection is very slow tonight.

    Tony
  • RCinFLARCinFLA Solar Expert Posts: 1,280 ✭✭✭
    Re: How PV grid-tie inverters can zap utility power factor

    Even a few hundred kW's of solar infusion is a drop in the bucket with respect to grid power.

    Sounds like just another stab by power companies to squash alternate energy that they don't directly control, and do it as politically correct as possible.

    As an aside, there was article in today's newspaper that Florida Power & Light is building a 75 megawatt solar-thermal generator in Martin county. Article says it will create enough power to serve 11,000 homes. Cost of project is $476M which comes to $43,279 per house.

    That would be about 40 years to breakeven. FPL is asking for overall rate increase and is guarantied 12% profit margin. They have also got approval to begin adding a surcharge for nuclear plant expansion eventhough they don't yet have approval to do so. If expansion is denied they don't have to give back any of the surcharge.
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