From 2009 through early 2012, Amonix installed nearly 40 MW AC of its flagship 7700 Solar Power Generator product in locations all across the southwestern USA. Since completion of these projects, Amonix has been adapting lessons learned from the 7700 build-out and new CPV technologies into the company’s 8700 Solar Power Generator, to be released in late 2014. The paper will focus on the features of the 8700 product, including higher performance and lower cost, and how the 8700 plans to keep CPV competitive in the global solar marketplace.
Concentrator PV (CPV) systems have attracted significant interest because these systems incorporate the world's highest
efficiency solar cells and they are targeting the lowest cost production of solar electricity for the world's utility markets.
Because these systems are just entering solar markets, manufacturers and customers need to assure their reliability for
many years of operation. There are three general approaches for assuring CPV reliability: 1) field testing and
development over many years leading to improved product designs, 2) testing to internationally accepted qualification
standards (especially for new products) and 3) extended reliability tests to identify critical weaknesses in a new
component or design. Amonix has been a pioneer in all three of these approaches. Amonix has an internal library of field
failure data spanning over 15 years that serves as the basis for its seven generations of CPV systems. An Amonix
product served as the test CPV module for the development of the world's first qualification standard completed in
March 2001. Amonix staff has served on international standards development committees, such as the International
Electrotechnical Commission (IEC), in support of developing CPV standards needed in today's rapidly expanding solar
markets. Recently Amonix employed extended reliability test procedures to assure reliability of multijunction solar cell
operation in its seventh generation high concentration PV system. This paper will discuss how these three approaches
have all contributed to assuring reliability of the Amonix systems.
After twenty years of commercial deployments of concentrator photovoltaic systems using silicon cells, Amonix has
built a new generation of systems designed for III-V multijunction cells. The resulting 7th-generation systems yield a
considerable performance dividend in the field-proven system design. The first systems, operating in Las Vegas, NV,
achieve AC efficiencies in excess of 25%. Detailed modeling of the cell and system parameters provides a prediction of
energy generation that is within 3% of the measured energy after seven months of operation. The predicted annual yield
in this location is over 2600 kW-hr/kW.
Concentrator systems are emerging as a low-cost, high-volume option for solar-generated electricity due to the very
high utilization of the solar cell, leading to a much lower $/Watt cost of a photovoltaic system. Parallel to this is the
onset of alternative solar cell technologies, such as the very high efficiency multi-junction solar cells developed at
NREL and Spectrolab over the last two decades. The relatively high cost of these types of solar cells has relegated
their use to non-terrestrial applications. However, recent advancements in both multi-junction concentrator cell
efficiency and their stability under high flux densities has made their large-scale terrestrial deployment significantly
Amonix has designed, developed and fabricated modules using the high efficiency multi-junction cells from
Spectrolab. One of these modules has been deployed at the University of Nevada, Las Vegas. The module has been
in continuous operation beginning May 2006. The efficiency has been measured periodically and has shown a
range from 26.1% to 28.5%. The latest measurement, made on February 20<sup>th</sup> showed an efficiency of 28.0 % at
956 DNI and an ambient temperature of 13 °C. This excellent stability of the multi-junction module's performance
promises to pave the way for future installations of this advanced technology. One short-term example of this is a
new Amonix-designed module capable of 30% efficiency and 300 Watts per module. This module's performance,
along with more testing of the long-term performance of the initial design will be presented at the time of the
Over the past 15 years, major advances in Concentrating Photovoltaics (CPV) have been achieved. Ultra-efficient Si solar cells have produced commercial concentration systems which are being fielded today and are competitively priced. Advanced research has primarily focused on significantly more efficient multi-junction solar cells for tomorrow's systems. This effort has produced sophisticated solar cells that significantly improve power production. Additional performance and cost improvements, especially in the optical system area and system integration, must be made before CPV can realize its ultimate commercial potential. Structural integrity and reliability are vital for commercial success. As incremental technical improvements are made in solar cell technologies, evaluation and 'fine-tuning' of optical systems properly matched to the solar cell are becoming increasingly necessary. As we move forward, it is increasingly important to optimize all of the interrelated elements of a CPV system for high performance without sacrificing the marketable cost and structural requirements of the system. Areas such as wavelength absorption of refractive optics need to be carefully matched to the solar cell technology employed. Reflective optics require advanced engineering models to insure uniform flux distribution without excessive losses. In Situ measurement of the 'fine-grain' improvements are difficult as multiple variables such as solar insolation, temperature, wind, altitude, etc. infringe on analytical data. This paper discusses design considerations based on 10 years of field trials of high concentration systems and their relevance for tomorrow's advanced CPV systems.
Amonix has become the first company to begin production of high
concentration silicon solar cells where volumes are over 10 MW/year. Higher volumes are available due to the method of manufacture; Amonix solely uses semiconductor foundries for solar cell production. In the previous years of system and cell field testing, this method of manufacturing enabled Amonix to maintain a very low overhead while incurring a high cost for the solar cell. However, recent simplifications to the solar cell processing sequence resulted in cost reduction and increased yield. This new process has been tested by producing small qualities in very short time periods, enabling a simulation of high volume production. Results have included over 90% wafer yield, up to 100% die yield and world record performance (η =27.3%). This reduction in silicon solar cell cost has increased the required efficiency for multi-junction concentrator solar cells to be competitive / advantageous. Concentrator systems are emerging as a low-cost, high volume option for solar-generated electricity due to the very high utilization of the solar cell, leading to a much lower $/Watt cost of a photovoltaic system. Parallel to this is the onset of alternative solar cell technologies, such as the very high efficiency multi-junction solar cells developed at NREL over the last two decades. The relatively high cost of these type of solar cells has relegated their use to non-terrestrial applications. However, recent advancements in both multi-junction concentrator cell efficiency and their stability under high flux densities has made their large-scale terrestrial deployment significantly more viable. This paper presents Amonix's experience and testing results of both high-efficiency silicon rear-junction solar cells and multi-junction solar cells made for concentrated light operation.