ArrayPower’s claim that is has produced a “sequenced inverter” design should be met with utter joy and a round of applause, since it’s exactly the kind of improvement the solar industry expected. Why? Because it reduces the cost of solar power by 10% and significantly boosts the efficiency of solar panels.
How does it do that? A familiar issue with solar panels is that they’re usually set up in series, so the current starts from one panel and is transferred to the next, until it reaches the end of the line. However, if one panels goes down or is shaded, the current’s transfer is compromised and the power output is brought down.
With these individual inverters, the problem virtually disappears. Instead of connecting all the inverters to one big inverter, each panel gets one “tenant” at its back. This one is equipped with a rectifier and a transistor to give the DC’s (direct current’s) voltage a push from 60 volts to the 208 volts needed by a grid.
The next step involves an inductor to shortly contain the current while the inverter pulsates alternating current. The mix up with the alternating current (AC) of another 3 panels is what allows the device to come up with the three-phase AC the grid tolerates.
In terms of money, this translates to $3.50 per watt, on average, installation included, which adds up pretty well – at the end of the day, it’s less than one third of what it should normally cost you. I think this is excellent news for the potential buyers – if this doesn’t appeal to them, I don’t know what would!
[via Cleantechnica]
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#1 by Kent Kernahan on February 9, 2012 - 12:20 am
Hello all, I am Kent Kernahan, inventor of the PAMCC technology discussed in this article.
In boiling it down, a few aspects are kind of lost.
As patented, the concept slices up the waveform in the time domain.
Pulse Amplitude Modulation Constant Current, its given name, describes it pretty well. The key to the invention is the conversion of Pulse Width Modulation to Pulse Amplitude Modulation by a psudo resonate filter we called a reconstruction filter.
This allowed the Dis-Continuous Mode output of the internal single stage differential boost to be converted into band limited PAM in one step.
As conceived, each PAMCC outputs a series of band limited pulses at a carrier frequency of about 30kHz modulated and synchronized with the baseband grid signal.
The individual PAMCC “Array Converters” are connected in parallel with their pulses offset in time to create a distributed multiphase inverter.
An important distinction from all other approaches that I know of is the carrier + modulation output which classifies each Array Converter as a modulator, a simpler thing than an inverter.
Since the reconstruction filters of each modulator were band limited to about 60kHz and had a bipolar half sine shape, The carrier was effectively canceled without a filter due to the out of phase current summation from multiple PAMCCs on the grid. The inspiration for this part came from multi path and beam forming techniques from my earlier background in RF.
So theoretically, no EMI for a large set because carriers of the same frequency summed out of phase cancel while the in-phase modulation builds. The grid itself actually demodulates a very clean ac waveform.
The idea behind three phase was to make the theoretical energy storage requirement close to zero because the power sum of three phase AC is constant. This means no large energy storage is required.
All in all should need less than half the components of a converter, be small, efficient and low cost.
So far, so good.
Now the mystery, I filed this patent in 2008 (it later issued with no prior art found) then got the company funded in 2009 with a prototype.
Now it is 2012. I can find no evidence that it is listed with FCC, VDE, UL or any other agency. The TR article refers to 7 months of trials and I can find no data of field performance ratios, third party verifications or reliability.
By now there should be PTC (PVUSA) and European weighted efficiency verified by somebody like Fraunhofer or NREL. There should be audited reliability by somebody like Exponent or intertek. There should be a California Energy Commission or other state listing.
The photographs show a case that is maybe twice the size of enphase, however, the design should be a fraction of the part count.
There have been published remarks on the elimination of bypass diodes however, the only patents I have seen published or issued are based on the notion of factory panel calibration and temperature compensation (my earlier work) which may actually cause hot spots and micro cracks as panels age.
Anybody seen an article this year on any of this?
kent@kernahan.org