Solar Energy Concentrators Designed with Algor Software to Provide for Future Energy Needs

A mirrored structure almost 50 feet tall tracks the sun throughout the day, focusing sunlight onto a thermal receiver and engine system which converts it to electricity. This advanced concentrator and power conversion system generates electricity at a cost that can compete directly with conventional power generation sources, making solar energy a promising technology for fulfilling current and future energy needs while reducing current levels of pollution.

The engineers at Science Applications International Corporation (SAIC), including Jeffrey Sandubrae, P.E., a senior engineer at the San Diego, California facility, have used Algor to develop two kinds of solar energy concentrator systems. The parabolic dish system for distributed-receiver applications is projected to be a promising option worldwide, especially in remote areas which are currently without electricity. Central-receiver (power tower) systems utilizing a large field of mirrored heliostats are more likely to be employed in larger installations.

Phase One

Jeffrey Sandubrae, P.E., a senior SAIC engineer who has been using Algor for the last ten years, considered wind, gravity loads, large strains in the mirrors and natural frequencies in the design of the heliostat shown here. 

With funding from the Department of Energy, SAIC and private investors, SAIC has been working on a three-phase program to develop technology which harnesses solar energy. In Phase One, a dish-type concentrator was designed and constructed at the company's test site in Golden, Colorado. 

The dish concentrator employs parabolic-shaped mirrors of thin stainless steel membrane stretched over a steel ring. The steel membrane is laminated with either a thin glass mirror or a silverized polymer reflective film. Using a vacuum, the membrane is pulled into a concave shape.

The mirrors focus the sun's rays onto a thermal receiver which extends about 40 feet out from the center of the structure. The heat is used to run a Stirling heat engine which operates at a solar-to-electric conversion efficiency of over 24%, far exceeding any other type of large solar power system.

The parabolic dish system shown here generates enough solar energy to achieve a solar-to-electric conversion efficiency of over 24 percent, far more than any other type of large power conversion system. Wind, gravity loads, large strains in the mirrors and natural frequencies were considered in the design of the dish concentrator.

Phase Two

Based on experience with Phase One, SAIC set out to reduce material, decrease installation costs and improve manufacturability of the dish concentrator system in Phase Two. By optimizing the cost per kilowatt hour, SAIC projects this product will be viable for use by private and government electric utilities. 

With each design modification, wind, gravity loads and natural frequencies were analyzed using Algor software. "Algor is very interactive, " said Mr. Sandubrae. "I can generate models easily, run a series of analyses and modify the models based on the results."

With each design modification, wind, gravity loads and natural frequencies needed to be considered. The optimized design is being installed at five sites throughout southwestern United States.

This beam/truss model combines the hub and dish structure of the parabolic dish concentrator. Both were modeled and analyzed separately and then combined with Algor FEA software. The hub, dish structure and support for the engine (shown in that order from left to right) were all modeled and analyzed separately.
This model combines the dish structure and the hub.

Heliostat Also Analyzed

Unlike dish systems, which may be used individually, central-receiver systems employ heliostats in larger installations. The heliostats typically are focused around a central receiver which collects the sunlight and transfers the sun's heat to a steam turbine for electricity generation. Each heliostat uses 22 flat mirrors per structure to focus sunlight onto the receiver. The heliostat structure was analyzed for wind, gravity loads, natural frequencies from the tracking engine and large strains.

A prototype heliostat is currently being tested at SAIC’s Golden, Colorado site. Plans exist to install additional heliostats at Sandia National Laboratories in Albuquerque, New Mexico, for optical testing and at Solar Two, a pilot power tower plant at Dagget, California for extended field tests.

The testing at Solar Two will help engineers such as Mr. Sandubrae gain insight into the heliostat’s design, fabrication, installation, performance and reliability. “This is a key step toward the first 50 megawatt electric power tower plant to be sited in the national solar enterprise zone in the southwest desert,” announced a September 1997 SAIC news release.

About Algor

Mr. Sandubrae is a long-time user of Algor who remembers the old days of running analyses on a 286 PC with 10 MB of hard disk space in a DOS environment. Today, he uses Algor's highly graphical Windows 95/NT line of software.

"The software has become so much more graphical and easy to use over the years," said Mr. Sandubrae. "Recently, I've been utilizing the animation capability to create .avi files of mode shapes and deformed shapes. It's very helpful to see these types of movement in action."

"Algor is very interactive," continues Mr. Sandubrae. "I can generate models easily, run a series of analyses and modify the models based on the results."

Download a self-extracting zipped animation (.avi) of an SAIC model (saic.exe, 80 KB).