Microinverters

Historically with solar electric design and installation, an inverter has been used to convert the ambient voltage of the solar electric dc system whether 12V or 24V or 48V to that of the traditional ac grid voltage that is used in homes, 120V or 240V.

This meant that all wiring must lead to the inverter to make the conversion from dc to ac so the power could be used in the home. This method causes some problems since more wire is needed, shading of one small part of one solar panel can affect the entire array and one has less flexibility.

Enphase Energy has laid claim to being the first to produce a microinverter system available for commercial or residential applications.

Microinverters reduce the bulk, space and noise of traditional inverters. A microinverter mounts below each PV panel, converts that panel’s DC current to AC and then ties directly into the existing wiring and power panel of the house. This saves the expense of heavy gauge copper wire, as well as the task of running it to your garage (or other centralized location) from the PV array. At a few dollars per foot, that wire amounts to a lot of money in labor and material. According to the Enphase Energy website, their microinverter can boost performance of PV panels by 5%-25%.
(from http://solar.calfinder.com on 9-29-09)

Here’s a short discussion from Home Power magazine April/May 2010 of a homeowner’s install of his solar electric using microinverters

“In 2008, Enphase microinverters hit the residential Photovoltaic(PV) market. Each module/inverter pairing operates independently…instead of a single inverter, I used 21 small ones. Each inverter reports the performance to an Envoy communications gateway via the AC wiring, then the gateway sends data to a web site to track performance for each module/inverter pair.

The AC wiring from the particular model of microinverter I selected can parallel up to 15 units. They plug into each other like extension cords. Since we have 21 units installed, we ended up with two AC circuits that are fed into a subpanel(through two 15A breakers) and then to the building’s main load center.”

This home installer did mention that the demand for microinverters is so strong that he had trouble getting all he needed at one time and frankly the testing for these products does not have much of a track record since they are so new(although they do offer test data on their website)

Here’s some spec data from the Enphase company website

Here’s some news from the Enphase website for possible investors

We feel that with the continued reduction of cost per watt of solar panels and innovative inventions such as the microinverter that home power via solar electric will increase in popularity. BUT the utilities will always be a consideration and unless they are induced to give more favorable buy back rates then true solar electric success will be postponed.