In Search of Skyline Solar – Part 3

[San Jose, California USA]

High Gain Solar (HGS) power plant dedication including HGS module ratings.

After In Search of Skyline Solar – Part 2, I managed to attend the dedication of the Skyline Solar High Gain Solar (HGS) power plant at the Santa Clara Valley Transportation Authority (VTA) Cerone Bus Maintenance and Operations Division a while back on Friday, May 15, 2009. Funny thing was that the VTA Public Information Officer, not Skyline Solar, extended the invitation although the dedication was open to the public.

Skyline Solar Plans Launch of First Product” by Ucilia Wang at Greentech Media captured the limited news originating from the event.

Skyline Solar, Inc. CEO Bob MacDonald thanked San Jose Major Chuck Reed for arranging the match between the VTA and Skyline Solar. The original Skyline Solar deployment site was planned for the Morgan Hill area but this was delayed by land permitting and easement issues.

CEO MacDonald said:

So this is Skyline’s approach to more effectively using materials so that we can get costs down and get the scale up. This is a relatively modest step in that direction, but we intend to be moving very quickly going forward and doing larger projects later this year and substantially larger projects on the MegaWatt scale in 2010.

The 24-30 kWp (kiloWatt-peak) Demonstration Project system capacity was declared to be 27 kWp. I am not sure why this was uncertain. Checking out the HDS Arrays amongst the crowd, I snapped a photo of what I believe is the module rating label. Skyline Solar refers to a module as an HGS Panel.

Max Power (Pmax): 71W
OPEN CIRCUIT VOLTAGE: 16.5V
SHORT CIRCUIT CURRENT: 5.6A
MAX VOLT (UL, IEC): 600V, 1000V
RATED VOLTAGE: 14.2V
RATED CURRENT: 5.0A
@ STC 1000W/m2 CELL T 25°C
Bin No: STR-571


Since this almost matches the theoretical module power rating after dividing 27 kWp by the number of Columns (4), HGS Arrays per Column (6), sections per HGS Array (4), and modules or HGS Panels per section (4), I believe this is measured under concentration conditions.

Each module consists of two independent strings of thirteen (13) monocrystalline solar cells, sized around one quarter of a 156 mm (millimeter) square cell, accessed by a junction box at each end. I guess each quarter cell from unknown suppliers can produce about 1 Watt. Two (2) strings times thirteen (13) cells times 1 Watt equals 26 Watts under one sun. It appears Skyline Solar believes they can extract almost three (3) times the one sun power from the monocrystalline silicon solar cells under 10x concentration.

I asked Skyline Solar representatives two questions.

Q: Why are some modules painted white while most are just aluminum?
A: Specification variation was sited; no one knew why.

I thought either these white modules had different vendor solar cells or the white was supposed to reflect and maybe recapture the light in the trough. As can be seen in the Picasa slideshow solar cell close-up, all the cells were front contact monocrystalline silicon solar cells.

Second, I asked to look at the inverters towards the back of the columns and roped off from the public. I got a quick No on this one even though I offered not to take photos. Of course, I wanted to sneak a peek at the instantaneous power production.

During his remarks, Jeff Byron, Commissioner, California Energy Commission, said:

Utilities like to own and operate their own generation. They really don’t like it when other people have it. It’s nothing disparaging of utilities; that’s their business.

But we want renewables to have an opportunity to have an equal footing, and the way to do that is through a Feed-in Tariff. So if you hear this term, Feed-in Tariff or FiT, we need to make it very easy for projects like this as they scale up into the MegaWatt scale to have an opportunity to easily get on the grid and sell their power in at a reasonable price.

This statement generated loud applause from the audience. Enough said.

6 comments

  1. can it be? says:

    If they’re getting 3x the power from 10x concentration, their thermal degradation and resistive losses must be quite high.
    Pout = (Concentration)*(1 Sun current)*[(1 sun voltage) + 0.17*log(Concentration) – (VlossFromT*OperatingTemp) ] – Resistance*[Concentration*(1 Sun current)]^2
    So without losses Pout (10x) > 10 x Pout(1 Sun)

  2. Edgar A. Gunther says:

    My simple calculations are done top down from the system capacity claimed by Skyline Solar and bottom up from typical monocrystalline silicon solar cell specs. The rating label seems genuine, but I suppose Skyline Solar disinformation is possible.

    As I observed in Part 2, “the concentration resulted in nonuniform solar cell illumination”. This has a direct effect on power production and system efficiency. 10x sunlight is only concentrated on “the horizontal center of the solar cells.”

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