The Company Behind the World's Best Solar Panel

SunPower (NASDAQ: SPWR  ) has become a power in the solar industry by building the most efficient and most reliable solar panels in the industry. But what exactly separates a SunPower solar module from the average solar module?

Below, I'll take a look at the technology and how SunPower is building a durable competitive advantage in the solar industry.

SunPower X-Series panel, which can reach efficiency of 21.5%. Source: SunPower.

It all starts with silicon
The vast majority of solar panels built today use silicon semiconductors as their core material. The silicon can either be multi-crystalline or mono-crystalline, but the latter is higher efficiency so that's what SunPower uses.

The other thing SunPower does is use an n-type silicon semiconductor versus the less efficient p-type that's more common in solar today. P-type semiconductors are prone to higher degradation rates both when a panel goes into service and over time, and this n-type construction is one reason SunPower's panels maintain higher efficiency long term. 

What's interesting in the silicon portion of the panel is that SunPower doesn't do anything another company couldn't do if it wanted to. It just chooses materials that are a cut above what most companies are willing to pay for and gets higher efficiency as a result.

Construction of the cell matters
Once silicon is cut into wafers it's time to make a solar cell. This is where SunPower's construction differs greatly from competitors.

A traditional silicon solar cell with ribbons and busbars on the surface of the cell. Image credit: U.S. Department of Energy via Wikimedia.

SunPower uses a solid copper foundation, back contact construction for its solar cells. So, instead of the electrons freed by the sun's energy flowing through ribbons and busbars on the top surface of the cell (seen to the right) they flow out the back of the cell onto a solid copper foundation. This also allows SunPower to place conductors closer together, providing a shorter path for electrons to travel before becoming electrical current.

It's this back contact construction that's so difficult to manufacture in a cost effective manner and results in SunPower having higher costs per watt than many competitors. The upside is that it's inherently more efficient because there's no shading from ribbons or busbars and provides the shorter path to collectors than traditional cells. When combined with the more efficient silicon the back contact construction makes a significantly more efficient solar panel. 

The back contact construction has been known for years but it's not commonly used because it's complex to make. If it weren't, others would be using the technology.

Power production after thermal stress. Source: SunPower.

Cell connections improve reliability
The copper back contact material SunPower uses also improves the connection between each cell, making a more rugged panel (see below). In a solar panel you're essentially connecting about 60-72 distinct power generating cells that connect to make one panel.

In a traditional solar cell, the busbars seen running along the top of the cell are then connected to the cell next to them and so on. If a cell or busbar breaks the entire panel can be compromised. This is problematic because thermal cycles can crack the silicon base or the conductors of a solar cell. With the solid copper foundation SunPower reduces that issue. 

SunPower has also engineered a lot of quality issues out of the solar panel by soldering the copper back plate to the cells next to it. This creates a more durable bond between cells that improves performance under stress from temperature cycles and physical damage to the panel.

Source: SunPower presentation. 

Not only does the back contact construction lead to higher efficiency for SunPower, it leads to a more reliable product long term, something third party testing firms have confirmed time and time again.

Below you can see SunPower's projection of its power advantage over the lifetime of a solar system, driven by the construction I've outlined above. 

Source: SunPower.

Foolish bottom line
There's no doubt that SunPower makes the highest quality and most efficient panel in the industry based on third party testing but the downside is that high-quality panel costs more per watt than competitors. To make up that cost, SunPower can pack more power in a smaller amount of space, lowering cost per kW-hr below the competition, which is the end goal for the solar industry. 

For investors, I think this panel construction advantage is more durable than many people think because SunPower has spent millions developing the technology and manufacturing capability to make high-efficiency panels. This isn't a trivial accomplishment and if others could easily copy it they would have by now.

The high efficiency and reliability are some of the main reasons I own shares of SunPower stock and make the company worth a look for any investor looking into solar energy.


Read/Post Comments (9) | Recommend This Article (15)

Comments from our Foolish Readers

Help us keep this a respectfully Foolish area! This is a place for our readers to discuss, debate, and learn more about the Foolish investing topic you read about above. Help us keep it clean and safe. If you believe a comment is abusive or otherwise violates our Fool's Rules, please report it via the Report this Comment Report this Comment icon found on every comment.

  • Report this Comment On August 31, 2014, at 2:32 PM, photonics wrote:

    Here's a solar module that outperforms over 100 of SunPower's solar panel models with its 92.88% PTC to STC ratio. And it cost far less than SunPower.

    It's less than 1/4 inch thick and It's also bifacial, and frameless, meaning that it can produce power from both sides of the cell. SunPower can't do that. And since it uses a double glass design, light that is reflected off the roof or ground surface strikes the backside of the cells and provide a boost in power above the rated capacity of the module. It's called Hyper X 2 and I think that it's going to give the PV industry a run for its money.

  • Report this Comment On August 31, 2014, at 3:24 PM, fenderola wrote:

    Bifacial solar panels can produce more energy due to the increased irradience from reflected roofing surfaces and other incidental reflections. However, due to the fact that these modules are frameless, it limits the maximum size of this type of module. Additionally the mounting methods become more complex sans frame. Certainly the frameless bifacial modules can produce an increased amount of energy but when you add the cost of additional packaging to protect the glass during shipping, limited size and mounting method, the offset in savings is negligible.

  • Report this Comment On August 31, 2014, at 4:23 PM, photonics wrote:

    The clamp/rubber gasket combinations that are used to mount these frameless modules to standard rails cost just pennies more than standard module clamps. 4 clamps are used just like a standard framed module.

    They are currently available in a 72 cell 360 watt configuration which is larger than most of the commercial and residential modules that are available on the market today.

    Their double glass construction makes for a more rigid design than Gen 1 framed modules, So there truly are no appreciable cost increases when using this technology.

    Although they are priced slightly higher (25 cents more) per watt than conventional lower efficiency, mono facial, framed modules, their increased power output yields a far greater return on investment over the life of the system.

  • Report this Comment On August 31, 2014, at 4:45 PM, Waldo wrote:

    Once again, Ron Wiser is back making lame sales pitches on every solar story. This time under the moniker "photonics" poo poos all other solar companies products and hawks his. Solar troll.

  • Report this Comment On August 31, 2014, at 5:04 PM, photonics wrote:

    Had a little too much over the Labor Day weekend Waldo ?

  • Report this Comment On August 31, 2014, at 7:21 PM, btc909 wrote:

    Waldo go price one of those SunPower panels. Hell pick a lower end model. I would advise sitting on the crapper when you read the price.

  • Report this Comment On September 01, 2014, at 1:42 AM, ridgeback1964 wrote:

    One issue I see is that I could not find them for direct sale. Apparently you have to have them do all the work. I actually know several people that just did the installation themselves with the help of a roofer and an electrician. I did this a year ago and had fun while saving money. This is really not that hard. I plan to add panels to my existing array within the next year, but obviously sun power won't be an option if they won't just sell the panels to me.

  • Report this Comment On September 02, 2014, at 4:35 PM, jargonific wrote:

    Verizon deal should keep their share price moving upward. Other deals likely.

    What's not to like?

  • Report this Comment On September 04, 2014, at 11:07 AM, ffbj wrote:

    I would probably opt for the First Solar flat panel, as I am concerned about hail damage. Normal solar panels will just be destroyed by a hail storm. Of course this depends on the area in which you live, not everyone has hail storms.

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