Opportunities in Solar Technology
(Abhishek Uppal)

Solar technology harnesses solar energy to create electricity and heat. Although we count on the sun for all of our energy, solar energy conventionally refers to two core technology groups:

Solar Photovoltaic (PV): Where a solar cell is used to convert light into electric current using the photoelectric effect. Photons from sunlight hit the solar panel, knocking electrons loose, which flow through the multi-layered cell creating electricity.

Solar thermal Solar thermal breaks down into two broad sub-categories:

Solar thermal power, where sunlight is used to heat water to low or medium temperatures. This technology is used to heat pools, for cooking, or to desalinate or disinfect water;
Concentrated solar power (CSP), where sunlight is used to boil water, producing steam that drives turbines.

The solar sector is growing rapidly. Lux Research, predicts that the market will grow to $100 billion by 2013.

Early research/proof of concept: The estimated 2013 market size for organic and Grätzel PV is $18.4 million, up from $2.42 million in 2008. Grätzel PV is a technology where light is absorbed by organic dye molecules, which transfer electrons to titanium dioxide nano-particles. Research is currently being conducted on the ideal dyes to use, but ruthenium polypyridine is emerging as the leading dye. In the lab, efficiencies of 11% have been achieved, but significant improvements over the early pilot efficiencies of 2.5% are needed before this can move into later stages of development.

Lab testing: The estimated 2013 market size for thin-film solar is $25.8 billion, up from $7.13 billion in 2008. While thin-film technologies have been in development since the 1970s, most are still nascent, with significant room for efficiency improvements. Amorphous silicon has made advances in repeatability, but cell efficiency is still low, around 5-6%, compared to nearly 20% for polysilicon. Next-generation (“micromorph”) amorphous silicon holds much promise, improving efficiency to 8-8.5%, but significant room for improvement remains.

Lab testing: The estimated 2013 market size for multi-junction PV is $1.20 billion, up from $341 million in 2008. Multi-junction PV cells are generally constructed with a layer of gallium arsenide and gallium indium phosphide on top of a germanium substrate. Multi-junction PV cells have achieved very high efficiencies (43% in lab testing and 37% in commercial applications), but they remain expensive, and will require significant cost reduction before they can be deployed commercially at scale.

Commercial with refinements needed: The most mature thin-film technologies have been developed by First Solar. Using cadmium telluride semi-conductors, First Solar has brought costs down to $1.12/Watt. While First Solar’s cell efficiency of 10.6% is respectable for thin-film technology, there is still significant room for improvement in the next few years.

Commercial: The estimated 2013 market size for crystalline silicon PV is $64.1 billion, up from $33.4 billion in 2008. There are a number of sub-technologies within crystalline silicon PV, including mono-crystalline modules and polycrystalline modules. While manufacturers continue to improve efficiency and bring down costs, this opportunity is at commercial scale today.

Commercial: The estimated 2013 market size for solar thermal is $9.26 billion, up from $1.10 billion in 2008. There are a variety of sub-technologies within solar thermal, which are distinguished by how the solar heat is concentrated. Parabolic mirrors, Fresnel mirrors and heliostat mirrors are all used to concentrate solar energy onto a receiver, warming a working fluid that, in turn, boils water and drives turbines. The technology is commercial and scalable today.