If researchers could develop a low cost, invisible solar cell to sub in for ordinary window glass, the result would be a sustainability twofer of epic proportions. Windows are notorious as a weak spot for energy efficiency, even in newer buildings. That goes double for millions of older buildings in the U.S. Upgrade to new see-through solar cell windows and you get to cut down on energy loss, keep all the energy savings from using natural daylight whenever possible, and generate renewable energy, too.
In terms of President Obama’s national energy policy, see-through glass solar cells provide another pathway for transforming the nation’s stock of older, inefficient buildings from an energy-sucking liability into a major source of clean, renewable energy. With that in mind, let’s take a look at the invisible solar modules being developed in a public-private partnership between the National Renewable Energy Laboratory and a company called New Energy Technologies, Inc.
A Long Road To Invisible Solar Cells
We first noticed New Energy Technologies (NET) back in 2011, when its SolarWindow transparent solar window coating caught the attention of the Department of Energy.
The coating is based on the “world’s smallest functional organic solar cells,” which according to NET are about one-fourth the size of a grain of rice. Rather than relying on silicon, the cells are based on inexpensive hydrogen-carbon materials (they fall into the category of organic solar cells).
The technology showed promise but in order to break into the mass market for single family homes and commercial buildings it needed to be scaled up in size and come down in price, and NET entered into an agreement with NREL to accomplish that.
Working with NREL, by 2012 the company succeeded in producing a transparent solar module of about 26 square inches. That might not sound like much but it was 14 times bigger than previous modules.
Just last week, NET renewed its cooperative R&D agreement with NREL to work on improving the coating’s performance and longevity, as well as developing more cost-effective manufacturing methods for commercial-scale production.
There’s a new twist to the research, too. NET and NREL will also be adapting SolarWindow to work on flexible surfaces including both transparent and tinted plastics.
Advantages of Solar Coatings
No single photovoltaic technology can achieve the best energy bang for the buck universally, so don’t expect SolarWindow (or similar products) to replace conventional solar panels. However, solar coatings do have some advantages that can help get low-cost solar power out of the lab and into widespread use.
The chief overall advantage is that solar coatings can be applied to a wide variety of existing surfaces or seamlessly integrated into new infrastructure. NET is currently planning on several main applications: flat glass for single family homes and commercial buildings (for both new construction and replacement windows), structural glass walls and “curtain walls” for tall buildings, decorative interior glass walls and surfaces (SolarWindow can harvest artificial light as well as sunlight), flexible films (similar to conventional window-tinting film) that could be applied to glass in new or existing buildings, and a line of building products with integrated solar capabilities.
As we’ve noted previously in CleanTechnica (here and here, for example), solar coatings also don’t require any particularly new manufacturing processes. The can be sprayed, painted or applied to surfaces through low cost, energy efficient roll-to-roll methods that can don’t require any new breakthroughs in manufacturing. NET’s SolarWindow, for example, can be sprayed onto glass at room temperature.
Mining the Built Infrastructure
The partnership between NREL and NET dovetails with President Obama’s Better Buildings Initiative along with the SunShot renewable energy initiative and Re-Powering America’s Land. Together, these three programs support and coordinate private companies, academic institutions and federal laboratories to achieve a new paradigm for domestic energy resources. Rather than focusing on releasing more ancient carbon from the earth, Better Buildings redirects innovators and engineers to concentrate on improving energy efficiency and repurposing the nation’s built environment into a vast network of clean energy harvesting opportunities.
Looking at the big picture, taxpayer support for new energy technologies should be far from controversial. U.S. policy has always been to provide taxpayer support for energy development as a matter of national security, economic development and public welfare. That’s a fungible principle of good government, not an ideology that only applies where fossil fuels are concerned (unless fossil fuels are your religion, but that opens a whole new can of worms).
For that matter, fossil fuel operations have always come with a price paid in high risks, lower quality of life and poor public health outcomes for local communities. Combined with the rapid pace of resource depletion, habitat destruction and population growth it’s clear enough that fossil fuels are not sustainable over the long run, even without the added complication of global warming.
Image (cropped): Building by See-ming Lee 李思明 SML
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