The Universal Studio on October 31st witnessed Tesla’s dream of powering the world through sustainable energy taking a step ahead with the unveiling of a solar roof. CEO Elon Musk introduced to the world how Tesla has been planning to harvest solar energy. If the traditional roof top solar panels come to your mind when I say solar roof, you might want to check out what Tesla has created!
The solar roofs are designed to be used with the Tesla Powerwall 2. This integration is to store energy generated during the day and for use at night.
Roof top solar panels, street lighting panels, ocean and land installations of solar panels were being used for decades. So what made Elon Musk remark: “I don’t know why nobody’s done this before. It blows my mind”. Notably, this technology unveiling comes weeks before the much discussed Tesla and SolarCity merger plans in November.
Let’s try stripping down the solar roof tiles to find out.
The Solar Roof Tile
A solar roofing tile is made of a glass layer, some color louver films to impart aesthetics and the very important solar cells. Sun shines on the tiles, through the glass and the films, and through to the underlying solar cell which converts the light into electricity. The tiles are said to use “hydrographic coloring” – basically, a water-based printing process – and the micro-louvers on the films are said to make the various roof tile colors possible.
Tesla partnered with 3M for the color louver films and joined hands with Panasonic to develop the solar roof tiles. Tesla and SolarCity also plan to work with Panasonic to integrate SolarCity’s Silevo solar cell technology, which the company earned through an acquisition several years ago. Silevo had pioneered the “heterojunction cell” – which is multiple layers of semiconductors – using a 6-inch wafer, while Panasonic hasn’t yet transitioned to using this 6-inch wafer. “We’ll take Silevo’s learnings on 6-inch and apply them to the learnings that Panasonic has achieved over the years for scaling heterojunction cells to gigawatts and beyond,” said SolarCity CTO Peter Rive.
BAPV or BIPV – What’s your ideal choice?
Tesla’s solar tiles constitute building-integrated photovoltaics (BIPV) that replaces specific building material. This is in contrast to traditional rooftop solar installations, which entails attaching a photovolatic module to a building separately. The goal of BIPV is to integrate installation as part of a construction project rather than a separate post-construction addition, making BIPV an efficient building material rather than a luxury add-on.
Building-applied photovoltaics or BAPV, on the other hand, refers to solar cells/panels that are retroactively installed on a building. While BAPV is much more common than BIPV, BIPV is truly the ideal scenario that Tesla aims to achieve.
Many stakeholders had agreed that solar installation needed to be rebranded as an aesthetic and technical improvement during home renovations, rather than a hefty module that is nailed onto the rooftop. Tesla’s new roofing product aims to bring solar cells further into the mainstream by removing any sort of visual setbacks homeowners may fear.
Cost per efficiency of solar tiles
To impart durability, longevity and safety to a building, BIPVs need to incorporate various layers and films. This affects the efficiency of solar cells and increases the cost per unit of energy generated. The efficiency of BIPVs versus its purchase cost has been a deterrent to its widespread acceptance. This was one of the reasons why Dow Chemicals cancelled its five-year-old solar roof “POWERHOUSE™ Shingles” project in June 2016.
Tesla, however, thinks it can get to a solar cell cost of 40 cents per watt over time at large scale, which is competitive with current commodity solar panels. Tesla also believes its cells will have efficiencies in the range of 22% to 24% – an improvement over commodity solar panels that more commonly convert around 10% to 15% of light into electricity.
Solar Roof Patents
Many of the U.S. patents held by SolarCity protect technologies relates to improved systems for mounting photovoltaic cells. According to an analysis by Innography, SolarCity filed 20 patent applications with the USPTO and published them this year.
Solar panels for Spanish tile roofs are also discussed within US Patent Application No. 20150075100, titled “Flashing System for Mounting Photovoltaic Arrays Onto Tile Roofs”. The tile hook and flashing assembly that would be protected includes a lower flashing, an upper flashing and a tile hook extending through an aperture in both flashings. This installation assembly is designed for use with Spanish tiles in such a way that doesn’t enable water to leak through the roof.
Silevo’s acquisition by SolarCity strengthened the solar cell technology and patent portfolio. Silevo’s energy efficient heterojunction solar cells as
mentioned above, have been patent protected. US 8872020 titled “Heterojunction solar cell based on epitaxial crystalline-silicon thin film on metallurgical silicon substrate design” claims a technology where solar cells include multiple epitaxially grown layers.
Further improvements in the amount of energy that can be generated by a solar cell panel are described in U.S. Patent Application No. 20150090314 titled “High Efficiency Solar Panel”. The solar panel disclosed here contains a plurality of solar cells arranged into a plurality of subsets so that cells are electrically coupled in a series; the subsets of cells are electrically coupled in parallel and the number of cells in each subset is large enough so that the output voltage of this panel is substantially the same of the output of a conventional solar panel. This innovation enables superior performance in solar cell energy generation while having an output voltage which is compatible with conventional solar cells.
Predicting Tesla’s Next Move
While critics claim the launch of Tesla Solar Roof as investment bait to assure investors about the predicated $2.2 billion acquisition of SolarCity on November 17, technologist and researchers eagerly wait to witness the efficiency of the solar roof as promised by Musk. The world however, is unanimously awestruck by the aesthetics of the solar roof and definitely finds it worth adopting as roofing solution if the costs of the solar roofs are pocket friendly.
Building the Tesla Ecosystem
The announcement of Tesla’s solar tiles does necessarily mean a solar power revolution; the reason being Tesla says it won’t start installing the product in any consumer homes in the U.S. until next year. Business strategies, market demands, technologically advancement and cost per efficiency are the multiple factors that can change the hype of the Tesla Solar Roofs.
Nevertheless, Tesla’s aim to build a solar power ecosystem is evident. Solar roofing, Powerwall and Tesla cars taken together represent a new kind of ecosystem that carries a promise of self-sufficiency in addition to ecological benefits.
The next important technological focus that can be predicated in light of the current product launches are cost effective and high efficiency semiconductor based solar cells that can convert solar energy efficiently and better power storage technology to store the generated energy to meet undisrupted energy usage. For Tesla to upbeat any competition in solar power harvesting, it would have to work towards increasing the efficiency and reducing the cost the solar ecosystem apart from publicizing the cool looking solar tiles and green environment.
(Featured image source: https://commons.wikimedia.org/wiki/File:Roof_of_black_bricks_under_sun.jpg#)