The Solar Magic explained.
[San Francisco, CA USA]
At Intersolar North America, Ralf Muenster, Director Renewable Energy Segment, National Semiconductor Corporation (NYSE:NSM) presented “Maximizing PV Output with Power Optimizers” in the program session:
Photovoltaic Technology (3): System Technology, Inverters & Off-grid Systems Large Scale PV Power Plants & Concentrating PV
Perhaps bucking to competitive pressure, Mr. Muenster addressed the perennial SolarMagic question, “How does this device work?” Please see SolarMagic, Solar Magic for background.
I didn’t catch the presentation, so I asked Mr. Muenster for the correct description of nominal operation and with SolarMagic installed in the two examples shown below. Setting the context, the presentation slides have been simplified to strings of five (5) photovoltaic (PV) solar modules (i.e. panels) for illustration purposes only.
|From Intersolar North America|
For a nominal installation, Mr. Muenster said:
Typically, you’d have around 10 panels per string and the DC link voltage would be around 300 V [Ed. Note: Volts] in the US; more panels and higher voltages in Europe.
The string current has to be the same for all five panels. The DC link voltage is determined by the centralized inverter, typically optimizing for the uncompromised strings.
Let’s say shade or soiling obstructs one panel in the string making it produce 50% of the power of the other panels in its string. The current of that entire string would be limited to the current through the compromised panel; half the current in this case. Since the DC link voltage on top of the string provides a second constraint, all the panels will be off their maximum power point, creating the 43% power loss in this five panel case.
|From Intersolar North America|
Continuing, Mr. Muenster said:
In a SolarMagic assisted string, the current still has to be the same across all panels. To compensate for the obstructed panel, SolarMagic would increase the current and lower the voltage of the shaded panel, while lowering the current and increasing the voltage of the non-obstructed panels so that at the end the constraint of the DC link voltage is fulfilled, as well.
Proprietary algorithms utilized in SolarMagic translate input voltage (V) / current (I) to the best output V/I and maximize energy transport. SolarMagic does not require complex external communications, yet they are cognitive and sense their V/I environment and collaboratively adjust until optimum module performance is reached.
In order to make the solution user friendly and bullet-proof we chose a highly reliable analog power line communication method combined with proprietary algorithms that are capable of arriving at the optimum solution for the string faster than the speed of fast moving clouds (in fact, fast enough to find the maximum extraction point for solar panels mounted on a moving vehicle).
In terms of speed, traditional (or micro) inverters are at a major disadvantage here since their control loop is limited by the speed of the grid; 50/60Hz [Ed. Note: Hertz or cycles per second].
SolarMagic operates in similar fashion to the SolarEdge PowerBox as described in the SolarEdge Architecture Overview white paper except for SolarEdge’s fixed string voltage.
MSRPs and the Oak Street retrofit
After seeing “SolarMagicTM Reclaims Lost Energy, Boosts Power Production from Normally-Operating Array by 22.6%”, I asked National about the MSRP (Manufacturer Suggested Retail Price) for the Blocking Diode and SolarMagic Power Optimizer (9 pak) and have not gotten a response thus far. Pricing queries to SolarMagic distribution partner AEE Solar have also been unanswered.
GoGreenSolar.com Founder & CEO Deep Patel said:
The MSRP of the individual SolarMagic units and the blocking diode are as follows:
SolarMagic (High or Low voltage version) – $312.45
SolarMagic Blocking Diode (600v string) – $124.05
I’m not sure what happened to the MSRP prices. When I went to their roadshow the MSRP price they were thinking of was “$199″ but obviously it’s much more. I wonder why? It’s quite strange.
If I stick with the announced SolarMagic $199 MSRP even though volume discounts would be expected, the Oak Street Affordable Housing partial retrofit cost:
6 strings * 12 modules per string * SolarMagic MSRP = 72 * $199 = $14328
(ignoring the cost of the six (6) Blocking Diodes, one per string)
While the Oak Street Affordable Housing case study concludes:
As a result, the system is now averaging a 22.6% improvement in AC output and running at an effective de-rate of approximately 82%; this is well in excess of its forecast production rate. The system is now producing more power than it did when newly installed.
I observe the retrofit is not equated to an incremental cost per kiloWatt-hour or LCOE (Levelized Cost of Energy).
Towards the end of “Fremont-based solar company eyes expansion with $2B backlog” by Mary Duan for the Silicon Valley / San Jose Business Journal:
Ralf Muenster, director of National Semiconductor’s renewable energy segment, said the company has shipped thousands of them since the product launched.
“Every panel supplier is now looking to differentiate,” Muenster said.
Meanwhile, I hear Enphase Energy has “shipped well over 30,000 microinverters to date”. In addition, Enphase microinverters “compensate at the cycle frequency of 60Hz (approximately 16 milliseconds) which Enphase believes is fast enough response time in the real world using a proprietary technique called ripple correlation that has excellent static and dynamic accuracy. All the microinverters track for MPPT autonomously so each associated module output is maximized.”