We had the scoop on SolarEdge a few week's back, and here's the update.

SolarEdge closed its $23 million Round B led by Vertex Venture Capital with the participation of all previous investors. Its previous round was $11.8 million in funding from Walden International, Opus Capital and Genesis Partners.

We've also heard that EnPhase, another player in that field, is in the midst of raising their next round.   SolarEdge had a lot of buzz amongst silicon valley VCs as well as raising the interest in the other players in the solar balance of plant (BoP) sector.

Here's a look at this facet of the solar market.

While high-profile firms like Nanosolar and Solyndra garner the lions share of media and VC attention, one sector of the solar ecosystem has been relatively overlooked -- inverters and balance of plant. While innovation marches on in PV materials, inverter technology and solar installation architecture has been relatively stagnant. Until now.

Innovative firms like SolarEdge are challenging the way PV systems are installed and wired together as well as influencing the way modules are manufactured. And they’re doing it with ICs and semiconductors, not with PV materials.

SolarEdge, in its first interview with the press, has revealed a few tidbits about its technology and announced to Greentech Media that the company is engaged in sales agreements, testing agreements, joint development agreements and has booked significant initial orders for its products from major module manufacturers and system integrators.

The typical solar installation strings together a number of, say, 180W solar panels. Because they are in series the panels act like batteries and the poorest performing panel or a partially shaded or dirty panel can degrade the performance of the entire string. According to SolarEdge, partial shading of solar panels can result in a dramatic reduction of solar panel output. One completely shaded cell can reduce a solar panel’s output by 40 percent to 95 percent.

There are a few different approaches to solving this problem. Startup SolarEdge and a few other firms are leading the way.

The DC approach used by SolarEdge (as well as National SemiconductorTigo Energy and a few others) optimizes the Maximum Power Point current for each module and monitors each panel via an ASIC embedded in the panel. SolarEdge claims that the performance of a PV solar system can be improved by 15 percent to 20 percent by using the company's chips and inverters. There is also a reduction in cabling costs and wiring losses as well as an added element of security and panel-level monitoring.

An alternative AC approach integrates a micro-inverter with each panel and performs the DC/AC conversion at the panel itself, not at the inverter. Rockport-funded Enphase as well as GreenRay and Petra Solar are using variations of this method.

There are some advantages and disadvantages to each architecture. In my conversations with firms like SolarCity and Akeena in the notably conservative installer industry, many were enthusiastic about new energy harvesting technology but reluctant to work with a product that was not yet field proven like the micro-inverters/AC approach.

Nevertheless, expect new thinking and innovation in solar installation architectures because of innovative ICs from the likes of SolarEdge.

Here's a list of some of the players in that field:

Solar Balance of Plant Firms:

ArrayConverter: Currently seeking VC funding, ArrayConverter is designing “self-monitoring AC modules??? with a distributed inverter architecture.

EnPhase: Distributed inverter architecture incorporates micro-inverters into each solar panel instead of on each “string??? of solar panels, potentially generating more power and providing additional monitoring and security benefits. Its most recent VC funding round led by Rockport was $15M in Sept 2008 in addition to the $6.5 million previously raised. Other investors include Applied Ventures and Third Point Ventures.

Green Ray Solar: GreenRay received $2.2 million from the DOE SAI program and closed a $500,000 seed round in 2007 from the Massachusetts Technology Collaborative. Its micro AC inverter allows a DC solar electric or PV module to produce AC power.

MPPC: Maximum power point control of solar panels. Pre-VC.

National Semiconductor: National Semiconductor's "SolarMagic" module is attached to each solar module and maximizes the performance of each solar panel. This looks to be a "DC bus" approach similar to SolarEdge and Tigo.

Petra Solar: Petra received $14 million in first round funding from DFJ Element and BlueRun Ventures in April 2007. They are attempting to improve PV Balance of System performance and cost with fast maximum power point tracking (MPPT). Their power electronics IP is licensed from UCF.

PV Powered: Privately held PV Powered builds inverters for residential and commercial PV as well as data monitoring modules. They claim to be the largest U.S.-based manufacturer of solar power inverter technology and have received $5 million from the DOE’s Solar Energy Grid Integration System (SEGIS) program, a $24 million effort to develop advanced inverters and balance-of-system components as well as funding from the DOE SAI program.

SmartSpark Energy Systems: Received a Series A from Battery Ventures with technology licensed from the University of Illinois. Their SolarBridge product is a PVAC micro-inverter. Other investors include Illinois Ventures and ITEC.

SolarEdge: Distributed inverter architecture using custom chip sets, junction boxes, and inverters built to maximize the energy harvesting capability of PV systems by correcting MPP mismatch, minimizing shading loss, etc.

Tigo Energy: Israeli startup Tigo raised $6 million in funding from Matrix Partners and OVP Venture Partners in June 2008. Tigo Energy’s products can improve output power, up-time, and reliability on existing and new solar installations Tigo claims to improve power output (kWh) in excess of 20 percent depending on weather conditions.