As part of the Ivanpah Solar Project, more than 300,000 software-controlled mirrors track the Sun in two dimensions and reflect sunlight to boilers that sit atop three 459-foot-tall power towers. When the concentrated sunlight hits the boilers’ pipes, it heats the water to create superheated steam, providing electricity to 140,000 California homes. (Photo by Dennis Schroeder/NREL)

In 1977, the National Renewable Energy Laboratory (NREL, Golden, CO) started as the Solar Energy Research Institute (SERI), spurred by national concern during the 1973 oil embargo that caused long lines and high prices at gas stations. Three months after his 1977 inauguration, President Jimmy Carter announced his desire to reduce dependence on foreign oil and invest in alternative energy sources. He created SERI with the mission to launch a new American energy industry, and consolidated oversight of U.S. energy policy into the newly formed U.S. Department of Energy.

While early work at SERI concentrated on solar technologies, the focus quickly broadened to include many forms of advanced energy, including wind and biomass. In 1991, President George H.W. Bush elevated SERI to a member of DOE's national laboratory system and changed its name to the National Renewable Energy Laboratory.

Working with partners in industry and academia, NREL delivers the scientific foundation for new energy technologies. NREL advances the science and engineering of energy efficiency, sustainable transportation, and renewable power technologies, and provides the knowledge to integrate and optimize energy systems.

Research Highlights

NREL supports 18 research programs that are organized into six directorates:

  • Bioenergy Science and Technology — This directorate advances technologies to produce bio-based fuels, products, and energy. Research covers exploratory research to pilot-scale processing. Capabilities include biochemical conversion, thermochemical conversion, algal biofuels, and techno-economic and lifecycle analyses.

  • Energy Systems Integration — Energy systems integration explores ways for energy systems to work more efficiently on their own, with each other, and with the electric grid. This directorate employs a holistic approach to developing, evaluating, and demonstrating innovative technologies and strategies to ensure that U.S. energy sources, demand-response programs, and delivery systems work seamlessly together.

  • Innovation, Partnering, and Outreach — This directorate accelerates the transfer of laboratory technologies to the marketplace.

  • Materials and Chemical Science and Technology — This directorate's capabilities span fundamental and applied R&D for renewable energy and energy efficiency. Key program areas include solar energy conversion for electricity and fuels, materials discovery and development for renewable energy technologies, hydrogen production and storage, and fuel cells.

  • Scientific Computing and Energy Analysis — This directorate is home to NREL's capabilities in high-performance computing, computational science, applied mathematics, visualization and data, analysis of energy systems, technologies, policies, resources, and markets.

  • Mechanical and Thermal Engineering Sciences — This directorate conducts research and development to enable technology innovations in NREL's advanced manufacturing, buildings, concentrating solar power, geothermal, transportation, water, and wind research programs.

Even before SERI, research to harness power from the Sun had been going on for hundreds of years. In the past 41 years, NREL has made significant strides in solar technology including these six major breakthroughs:

High-efficiency cells. Silicon solar cells were fairly new when NASA sent the Vanguard I satellite into orbit in 1958. But the cell used for that first solar-powered satellite could only capture and use about 9% of the sunlight that reached it, so the technology was too expensive and inefficient to spark much interest on Earth. In 1984, NREL found that gallium indium phosphide (GaInP) — promising for use in semiconductors but difficult to alloy with other materials — was compatible with gallium arsenide (GaAs). A layer of each was combined to create the “tandem-junction” solar cell.

Thin films. NREL scientists have been working with thin-film photovoltaics (PV) — cells that use much less active material than silicon wafer cells — from the very start of SERI. Researchers have studied various materials and devices, and the greatest commercial success to date has been the cadmium telluride (CdTe) module. NREL has contributed to its success with depositional technology for these materials, and in revealing the fundamental physics underlying the PV process at work at the microscopic and atomic levels.

Reliability science. PV technology may be a scientific marvel, but if solar devices — from cells to modules to systems — could not withstand the rigors of normal operations and extreme weather, they would have remained a laboratory novelty rather than blossoming into today's multi-billion-dollar industry. Understanding the need for robust technology, NREL developed indoor and outdoor testing facilities and procedures that put PV technologies through the paces, ensuring they have the necessary durability to operate reliably for 30 years or more.

Cell and device measurements. Another early NREL focus was to develop the techniques, equipment, and facilities to measure the properties of the PV devices that they and others were creating. They also needed to characterize the devices, determining their efficiency and performance within very strict tolerances. NREL measures, characterizes, and certifies many thousand samples each year.

Third-generation solar cells. Basic NREL research programs that started receiving funding in 1979 led to the creation of what's now known as third-generation solar cells — the first two generations being semiconductors and thin films, respectively. The latest generation has the potential to overcome the theoretical power conversion efficiency limit of 33% that applies to a single semiconductor solar cell.

Perovskites. NREL has only been involved in this emerging solar technology for about five years, but NREL scientists have become world-renowned for perovskite research. Efficiencies continue to climb, from a starting point of less than 4% up to 22% — and perhaps more importantly, NREL is making progress in understanding the causes of perovskite stability issues and mitigating their impact. For example, industry will not accept a device with an excellent initial efficiency, only to see it degrade under humid conditions to drastically lower values. NREL is discovering new perovskite materials and device structures to overcome this potential weakness.

Tech Briefs Magazine

This article first appeared in the September, 2018 issue of Tech Briefs Magazine.

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