Solar Photovoltaics and CIGS
Electrical Energy
Worldwide demand for electricity is expected to significantly increase over the next 20 years. The Energy Information Administration of the U.S. Department of Energy estimates that world net electricity consumption will nearly double by 2025.
The overwhelming majority of electricity is currently produced using hydrocarbon sources (natural gas, coal, petroleum). Volatile prices and environmental and political concerns pertaining to fossil fuels have increased interest in electricity created using renewable, clean energy sources such as solar.
The Opportunity
According to the US Department of Energy, PV systems presently represent less than 1% of world energy production and are being adopted as a means to address both rural electrification in remote areas and as supplemental energy sources in grid-connected areas of the world. The market for PV products worldwide has increased over the last six years at an average annual growth rate of over 40%, driven by major governmental incentive programs in Germany, Japan and the United States. The market for PV systems reached approximately two Gigawatts (2 GW) in 2006, with a total installed base of approximately seven GW. By 2010, analyst predictions suggest the annual product market size could range from 5-15 GW worldwide. Some industry analysts postulate an industry potential of up to $1 trillion dollars by 2025.
Solar Photovoltaics
Solar cells work by absorbing light and converting it to electrical power, referred to as the photovoltaic effect. The majority of commercial solar cells in use today are made of silicon, the same semiconductor material used in the microelectronics industry. In addition to the semiconductor materials, solar cells consist of a top and bottom electrical contact to move the electricity out of the solar cell. The performance of a solar cell is measured in terms of its efficiency in converting sunlight into electricity. Typical commercial solar cells have an efficiency ranging between 6% and 18%, meaning that for every 1,000 watts of sunlight striking a solar module, 60 to 180 watts of electricity will be produced.
The bulk of today's market is served with expensive Silicon semiconductor wafer material, which shares its demand with the volatile integrated circuit industry. Recent supply shortages and uncertain raw material costs continue to suggest a demand that far out paces the supply in the next 5-10 years.
Photo Courtesy: Blitzstrom Thin Film Installation
Thin Films
Solar cells and modules made from certain thin film semiconductors have shown to be much less expensive to produce in larger volume requiring much less raw material to produce than silicon based PV cells. Extensive research and development on thin film cells has been conducted for more than 30 years, and recent advances in manufacturing and product commercialization have increased worldwide share of thin film PV to over 7% in 2006.
Thin film PV products exhibit the following attributes:
- Scaleable, low cost manufacturing: Thin film solar cells and modules require a structural "substrate" to support them, such as glass, plastic or metal sheets or foils. Applying the films on these substrates creates a range of manufacturing options that enables continuous and scaleable manufacturing. As much of the equipment to process these substrates is used in other industries, the capital expenditure required to establish large-volume thin film PV product manufacturing plants enables rapid capacity expansion and lowers the cost per watt of products.
- Lower material cost: The substrate and raw materials used in thin film PV products are less expensive than the cost of most semiconductor materials. With increasing thin film manufacturing capacity and process yield improvements product costs are reduced.
- Configurable form factors: Based on the use of a variety of substrates, thin film PV modules can be configured into a number of different form factors to enable a variety of market applications. In particular, flexible thin film modules could enable a new range of products for unique BIPV applications.
- Performance attributes: Thin film PV technologies are generally less efficient than modules made with Silicon. However, thin film PV technologies do exhibit performance advantages in generating energy in low light level and increased temperature environments. This positions them particularly well for applications in regions with less direct sunlight, such as in Northern Europe.
CIGS
Of the three thin film technologies currently being commercialized, solar cells and modules based on copper indium gallium di-selenide (CIGS) have shown the highest laboratory electrical conversion efficiency, can be produced on multiple substrates (glass or foils) , and hold promise for low cost highly scalable manufacturing.