Photovoltaic Glass Units (PVGUs), are compatible with standard glazing systems, combine energy efficiency, high density solar power generation and transparency

Tech Bites Says:

By producing see-through photovoltaic modules that can be integrated with nearly any curtain wall-type glazing system, Pythagoras Solar hopes to make it easy and economical to add solar-electric capabilities to the large expanses of glass found in office, industrial, and commercial buildings. Known as Photovoltaic Glass Units (PVGUs), the modules employ a prism system that steers most of the so-called direct sunlight striking its surface to an integrated silicon solar cell while allowing the indirect light that contains visual information to pass through it. The result is a window that produces up to 140W/square meter of electrical power, dramatically reduces a building’s cooling requirements, and still provides its occupants with a clear view of the world.

Udi Paret, Pythagoras’ Vice President of Business Development, says that the system’s pricing will be competitive with standard high-end glazing materials (vacuum glass, triple-glazing, electro-chromic systems, etc...), but it actually pays for itself by providing a significant offset to a building’s electricity bill. In fact, Paret claims that the technology has a sub-3 year payback in areas with higher utility rates and favorable feed-in tariffs.

Although there are several companies already producing so-called building-integrated photovoltaic (BIPV) systems, Pythagoras’s transparent PVGUs were designed to get around most of the power density and aesthetic trade-offs that have limited the utility of earlier BIPV products. While most BIPV systems use amorphous thin-film PV material placed directly on the window’s surface, the Pythagoras modules uses a cast acrylic prism system to direct the sunlight to high-efficiency polycrystalline silicon cells that are placed perpendicular to the window pane. The module’s integrated wiring system has been designed to enable quick, reliable assembly in construction site environments. A simple locking connector allows the outputs from each window frame to be tied together and brought to a standard terminal block at the end of the array that can be connected to a micro inverter or the building’s main PV power bus.

The module's prisms divert most of the so-called direct sunlight, but they still provide up to 75% transparency for the reflected light from the scenery so that occupants sill enjoy a great view. The prisms also serves as a concentrator that makes efficient use of the costly silicon cell and allows the modules to be as tall as 4” while still remaining thin enough (typically 1”) to drop directly into commercial window frame designs. Since the concentrated sunlight can cause significant heating of the solar cell, it is mounted on an integral heat sink that dumps captured heat to the outside.

One of the few downsides with the Pythagoras PVGUs is that while they are excellent at reducing solar-related heat gain, they are not as good at reducing heat loss as non-PV glazing options. The thickness of Pythagoras’s modules will vary by applications, so it’s impossible to pin down the window’s actual R value but, given a nominal 1” thickness, it’s safe to assume it will be in the neighborhood of R-3. While this is fairly good for a standard double-pane window, today’s triple-glazed or vacuum pane glazing systems are much better than this. In its defense, Pythagoras says that once the initial products are launched it will be relatively easy to tweak the design to deliver higher R values for applications in Northern latitudes. But even the existing system’s thermal performance should be more than adequate to justify its use in many applications in moderate and cool climates.

The other concern I have is whether Pythagoras can get their pricing low enough to be commercially competitive. While not an easy task, they have certainly done lots of things that may actually allow them to fulfill their promise of delivering a PV window system that is in the ballpark with other premium non-PV products. Part of this strategy is to insure the windows can be built with standard materials and processes and to minimize the additional assembly steps they require. Individual PV modules are made on a simple assembly line (Flextronics has the initial manufacturing contract) and are then laminated with ordinary glass panes into standard-sized insulated glass panels. According to Pythagoras, these PVGUs can be substituted for normal insulated glass units (IGUs) in nearly any window frame or glazing structure with no additional labor cost.

The PVGU’s ability to work seamlessly with the industrial glazing industry’s manufacturing and distribution infrastructure gives Pythagoras a double-pronged strategy for achieving market share. They have signed relationships with material suppliers and manufacturers (Flextronics), as well as several glazing companies that fabricate the actual curtain walls and skylights for big buildings. They also have agreements with vertically-integrated manufacturers that make standard “white label” building products. “Our first products are optimized for large commercial and hi-rise buildings though down the road we’ll have standard ones for the residential market as well, skylights in particular” added Paret.

Paret says that having worked hard to make the PVGUs “just another glazing option” has helped earn Pythagoras a very warm reception from the usually-conservative building materials industry. He said that the AEC (architect, engineer, construction) community as well as large glazing and integrated glass companies are have been very enthusiastic about the technology and are eager to explore potential applications for Pythagoras products.

If Pythagoras can truly meet the challenges of making durable, competitively-priced PV windows, it should help move building-integrated solar systems from the limited applications they enjoy today into the mainstream of commercial and industrial architecture.   For more information, visit Pythagoras Solar’s web site - http://www.pythagoras-solar.com,

Pythagoras Solar Says:

Pythagoras Solar Announces Photovoltaic Glass Unit (PVGU), First Green Building Material to Combine Energy Efficiency, High Density Solar Power Generation and Transparency

Relationships with Arkema, China Sunergy and Flextronics Will Help Company Scale

SAN MATEO, CALIFORNIA and TEL AVIV, ISRAEL—(May 18, 2010)—Pythagoras Solar, a provider of advanced building-integrated photovoltaic (BIPV) products, today announced plans to commercialize the industry’s first energy efficient, transparent and high power density photovoltaic glass unit (PVGU). The company’s groundbreaking new technology is the first to combine energy efficiency, solar power generation and appealing aesthetics in a single green building material – a solar window. PVGU products will be available for curtain walls, skylights and windows in the second half of 2010.

Pythagoras Solar also announced that it has established formal relationships with Arkema, China Sunergy and Flextronics, all of which will help Pythagoras Solar to quickly scale its operations as it prepares for commercial production and distribution.

Triple Value BIPV Technology

Pythagoras Solar leverages a combination of patent-pending optics, high-efficiency crystalline silicon, advanced materials science and simulation software to create a highly efficient photovoltaic glass unit (PVGU), a new category of green building material. Unlike existing BIPV products, Pythagoras Solar curtain walls, skylights and windows simultaneously block solar radiation; concentrate sunlight and convert it into solar power; and deliver a high level of transparency for optimal daylighting and aesthetics. A video animation and images of the PVGU platform are available at www.pythagoras-solar.com.

“Our new PVGU technology finally bridges the gap between energy efficiency and energy generation – enabling the architecture, engineering and construction sectors to accelerate the deployment of cost-effective distributed power generation and to advance aesthetically-pleasing Net Zero Energy Buildings,” said Gonen Fink, co-founder and CEO, Pythagoras Solar. “Our partners across the value chain are responding very positively to the combination of economic, environmental and aesthetic benefits.”

Designed to be an easily integrated component of conventional building construction, Pythagoras Solar products offer triple-value benefits by combining the energy efficiency benefits of an insulating glass unit (IGU), the shading and lighting benefits of patent- pending optics, and high-efficiency solar power generation, which combined offer architectural adaptability and increased real estate value.

Pythagoras Solar is already working with large-scale materials, manufacturing and building industry partners, thus ensuring quality and reliability; simplifying procurement and installation; and reducing costs.

“We are very excited to partner with Pythagoras Solar on the production of the company’s revolutionary PVGU products. Our early involvement in the design process will not only help the team to optimize the product in the early stages of development, it will also help to leverage Flextronics’ scalable and repeatable manufacturing process,” said E.C. Sykes, president of Flextronics Industrial. “We are always happy to provide our industry leading Clean Tech solutions and services to companies such as Pythagoras Solar that enable green applications which meet the high quality requirements of the solar industry and are aesthetically pleasing.”

BIPV Market Opportunity

Research firm NanoMarkets forecasts the global BIPV market to exceed $8 billion by 2015. Pythagoras Solar has raised a total of US$11M in seed and venture capital funding to date, including US$10 million in a Series A funding round led by Israel Cleantech Ventures to invest in R&D and product commercialization.

“Pythagoras Solar’s approach to BIPV is unique and overcomes barriers to adoption for the architecture, engineering and construction community,” said Meir Ukeles, partner, Israel Cleantech Ventures. “As the solar PV market matures, we expect that BIPV will represent a much larger portion of new distributed generation installations given the volume of available square footage for PVGU installations.”