Note: This is the first article of a three-part series covering plastics in solar energy (photovoltaic) (1) trends, (2) material/process advances and (3)applications.

Most people no longer ask whether solar energy/photovoltaics (PV) will be a success, the question is now rather which forms of PV will be successful.

PV will become cost competitive with a significant portion of new total electricity generation worldwide by 2020. The total global installed PV capacity is fast approaching 100 gigawatts (GW) — up from 1.5 GW in 2000 to 92 GW at mid-year 2015.

In 2015, for the second straight year, solar PV was the leading source of new electricity capacity installed, beating out wind, gas, coal and nuclear. This trend is expected to continue as solar installed costs continue to fall.

In the past five years, the price of installed PV systems has dropped significantly. These price reductions are primarily attributable to steep reductions in the price of PV/solar modules.

From 2008 to 2015, annual average module prices on the global market fell by approximately $2.60/watt, representing about 80 percent of the total decline in PV/solar module system prices over that period. The cost of electricity produced from solar installations has been steadily dropping toward that of standard grid electricity.

BP Solar Home Solutions
Path to grid parity.

Continuous reduction in PV cost is a key driver in this market. Prices for solar panels have declined by around 75 percent in the past 10 years. Government policies and incentives are also significant market drivers. For example, solar PV installations in China will exceed 4 GW in the second half of this year as the country's planning body has raised its solar energy target from 15 GW to 21 GW by year end 2015.

In certain states in the US, Renewable Portfolio Standards that include specific requirements for solar (i.e. solar carve-outs) mandate energy suppliers and utilities to generate or procure a certain percentage of electricity from solar or risk paying a steep Alternative Compliance Penalty (ACP).

Solar/PV devices produce electricity that :

  • requires little or no maintenance
  • causes no pollution
  • does not deplete materials
  • is silent

Other drivers are:

  • Ability to integrate PV into building materials
  • Ability to operate in low/indoor lighting, flexibility/rollability, lightweight and lower cost creates demand for nano-based solar cells
  • Ever-smaller portable personal electronic devices with growing power requirements accelerates portable power demand

Let's look at the building-integrated photovoltaic (BIPV) market forecast and drivers. The growing availability of energy-efficient, flexible and transparent solar materials is transforming the way architects and building engineers view and use photovoltaic systems. The emerging BIPV market offers a new way for the housing and global solar industries to develop new revenue streams.

Market researchers at Navigant Research project the total capacity of BIPV systems will grow to 2,250 megawatts (MW) globally by 2017, up from approximately 400 MW in 2012, with BIPV roofing the largest near- and mid-term market segments. This global market is conservatively on target to quadruple over the next five years, growing from $606 million in 2012 to an estimated $2.5 billion by 2017 perhaps as high as $3.7 billion under a more aggressive forecast.

Energy-efficient, flexible and transparent solar materials, which offer superior vertical performance (i.e. on walls) and subtle red, green or blue color options are beginning to emerge. This will allow BIPV features to expand outside the limited current options, which are largely restricted to rooftops and spandrels.

Navigant Research
BIPV revenue ($ million).

Major market drivers are:

  • PV improvements and rapidly falling cost per watt
  • new high-efficiency CIGS technology panels and shingles that facilitate rooftop installations
  • Solar crystalline-silicon modules and thin film tiles/shingles that aesthetically blend into building facades, atria and rooftops
  • New building energy regulations in the European Union (EU) and elsewhere

In the EU, all new buildings must be nearly zero-energy consumption buildings by year-end 2020. New buildings occupied and owned by public authorities must comply with the same criteria by year-end 2018. The buildings sector represents 40 percent of the EU's total energy consumption. Reducing energy consumption in this area is therefore a priority under the "20-20-20" objectives on energy efficiency.

A newly announced $4 million grant will subsidize the construction of at least 25 net-zero energy homes (NZEHs) in four Canadian provinces. The initiative is being funded by the Canadian government's ecoENERGY Innovation Initiative (ecoEII), homebuilders and building materials manufacturers.

Coincidentally, Natural Resources Canada is providing $1 million in new funding for the Smart Net-Zero Energy Buildings Strategic Network (SNEBRN), an alliance of researchers from 15 Canadian universities. The money is to be used to research and test new net-zero technologies for both houses and commercial buildings.

While new construction that incorporates BIPV attracts much attention, retrofits is also a promising market. To spur the use of low-cost residential and small commercial rooftop solar systems in the U.S., the Department of Energy has launched the SunShot competition to challenge U.S. teams to quickly drive down the cost of installed rooftop PV systems.

"America's Most Affordable Rooftop Solar Competition" offers a total of $10 million in prize money to the first three U.S. teams that can install 5,000 rooftop solar PV systems at an average price of $2 per watt. By setting an ambitious target, the competition aims to spur creative public-private partnerships, original business models and innovative approaches to make solar energy affordable for millions of families and businesses.

Delving further, transparent nanofilm for solar window application combines advanced conductive plastic and nanoplastic technologies. Transparent thin films able to absorb light and produce an electric charge over a comparably large area have been developed by researchers at the Department of Energy's Los Alamos National Laboratory. The material could potentially be used in the production of transparent solar panels or solar windows.

The material is made from a semiconducting polymer (polyphenylene vinylene, PPV) injected with carbon-rich fullerenes. Under monitored conditions, it is able to self-assemble and form a reproducible pattern like a honeycomb.

The honeycomb thin film was made with a flow of micrometer-size water droplets spread across a thin layer of the polymer/fullerene blend solution. As the solvent evaporates, the polymer develops into a hexagonal pattern, which takes on a honeycomb-like appearance.

U.S. Department of Energy, Los Alamos National Laboratory
Transparent nanofilm honeycomb structure. Top image: Scanning electron microscopy image and zoom of PPV honeycomb. Bottom images (left to right): Confocal fluorescence lifetime images of conjugated honeycomb, of polymer/fullerene honeycomb double layer, and of polymer/fullerene honeycomb blend. .

The material remains largely transparent because the polymer chains pack densely only at the edges of the hexagons, while remaining loosely packed and spread thin across the centers. The densely packed edges strongly absorb light and may also facilitate conducting electricity while the centers do not absorb much light and are relatively transparent.

The slower the solvent evaporates, the more tightly packed the polymer, and the better the charge transport. The next step will be to use these honeycomb thin films to fabricate transparent and flexible organic solar cells and other devices.

The honeycomb structure was verified for its uniformity by using different scanning probes and electron microscopy methods. Additionally, the optical properties and charge generation at the edges, centers and nodes where individual cells connect on the structure were tested with time-resolved confocal fluorescence microscopy.