BRIGHTSOURCE ENERGY: POINTING THE WAY TO SOLAR ENERGY WITH HELIOSTAT TECHNOLOGY
As oil and natural gas prices continue to rise, companies are increasingly looking for viable alternatives to fossil fuels like solar energy. Although, there remains one question about this seemingly unreliable form of energy: how can we leverage the full power of the Sun’s rays, in the most energy-efficient, cost-effective way, to gain the greatest energy value?
BrightSource Energy, Inc. has an answer: motion-controlled, Sun-tracking heliostats (mirrors) that follow the Sun to capture the maximum solar energy output. Most people are familiar with solar panels on roofs of houses that use photovoltaic cells to capture the Sun’s rays and convert to energy. BrightSource uses heliostats (a different kind of panel), which are motion controlled and direct the Sun’s rays toward a water tower, boiling the water inside and efficiently producing renewable energy in the concentrated solar power (CSP) system.
BrightSource designs, develops, and deploys concentrated solar thermal technology to produce high value steam for electric power, petroleum, and industrial-process markets worldwide. Combining breakthrough technology with world-class solar thermal plant design capabilities, BrightSource generates clean energy, reliably and responsibly, while minimizing impact to the environment and helping customers meet their clean energy goals.
The challenge? Finding a company to deliver the most energy-efficient, motion control technology to capture the Sun’s immense power.
Analog Devices and its ADI Trinamic™ motion control technology proved worthy of the challenge.
AT A GLANCE
BrightSource has pioneered CSP by combining breakthrough solar technologies with advanced storage, implementation, and optimization capabilities. By harnessing and managing renewable energy resources, BrightSource delivers CSP with thermal energy storage to produce clean, reliable, and cost-competitive solar energy.
Successfully access and leverage the optimal percentage of the Sun’s rays in order to gain the most energy value.
Need precision movements of heliostats to precisely direct the Sun’s rays toward a water tower, boiling the water inside and efficiently producing renewable energy in the CSP system.
The ADI Trinamic TMC5130 IC. BrightSource chose this specific IC due to its broad, proven commercial usage and special features; in particular, its CoolStep™ and StallGuard™ technologies.
HOW CONCENTRATED SOLAR POWER WORKS
CSP is an elaborate design of sophisticated machinery that creates and stores thermal energy for use in generating electricity. A typical CSP plant involves tens of thousands of Sun-tracking heliostats mounted on dual-axis trackers that follow the Sun and aim its energy to the molten salt receiver (MSR) at the top of a central tower. The tower transfers the molten salt to a tank which acts as a giant, charged battery. From there, it flows to a heat exchanger that creates steam and turns a turbine generator to deliver synchronous, reliable, and renewable electricity to the grid.
- Solar-tracking heliostats capture the Sun’s rays and concentrate them on the molten salt receiver (MSR) on the water tower.
- The molten salt inside the receiver absorbs the solar energy and heats up to over 1000˚F (538˚C).
- The molten salt is stored in a tank that acts as a giant, charged battery.
- It then flows through a heat exchanger where it heats steam to turn the turbine generator.
- The renewable, reliable energy generated then goes to the grid.
A SHINING EXAMPLE OF RENEWABLE, SOLAR POWER ENERGY
BrightSource currently operates the largest solar, thermal power stations in the U.S., the Ivanpah solar power generating system in the Mojave Desert. This massive project consists of 173,000 heliostats and generates 392 MW power, enough to power 100,000+ homes in southern California. In addition, ADI’s TMC5130 is being used in BrightSource’s Redstone project in South Africa, which includes 42k heliostats.
The key for BrightSource to generate such massive amounts of clean energy is to ensure its solar panel heliostats move in coordination with the Sun’s position in the sky. This way they can capture 100% concentration of the Sun’s rays directly on the panels. In order for this to occur, these heliostats must utilize motion control motors to precisely follow the Sun’s path.
The challenge for BrightSource was to partner with a company who had a history of delivering a level of extremely precise, motion-activated technology necessary to be deployed on thousands of heliostats. What’s more, this technology had to meet certain, stringent requirements: be able to endure unpredictable, harsh weather conditions; be of a small size to fit within the constraints of the panels; be extremely energy efficient; and, of course, be able to deliver consistent, reliable, and ultraprecise results.
ADI TRINAMIC: PUTTING CLEAN SOLAR ENERGY IN MOTION
“We’re very happy with ADI and its extensive R&D support throughout the whole process. We hope to continue this relationship and collaboration. (ADI’s) insights and expertise proved it is far beyond a mere chip provider.”
BrightSource, Senior Hardware Engineer and Team Leader
INCREASED RELIABILTY, EFFICIENCY — REDUCE SAFETY MARGINS
ADI TRINAMIC COOLSTEP TECHNOLOGY
With ADI Trinamic, BrightSource received the power and energy efficiency performance it needed to add to its overall sustainability and energy production goals. The ADI Trinamic CoolStep feature is important to BrightSource since the units that control the motors are powered by 12 W PV panels and a 36 Wh powerpack backup, making energy efficiency a crucial aspect of its operation.
Originally developed for medical devices and lab automation, CoolStep is a sensorless, load-dependent, current control that always drives motors at the minimum amount required for the actual load condition. By doing so, the technology reduces the motor energy consumption, and heat generation. Also, by eliminating the current safety margin and allowing for temporary current boosts, CoolStep allows for smaller motors since less torque reserve is required.
ADI TRINAMIC STALLGUARD TECHNOLOGY
The ADI Trinamic StallGuard feature is a sensorless load measurement for stepper motors, which allows BrightSource to perform load detection on heliostats that require high reliability movements. StallGuard gives cost-effective feedback on the diagnostics on the load-angle along with sensitivity data that can be adjusted to fit the application’s need. This makes it ideal for sensorless homing, self-calibration, distance measurement, or to verify all mechanics still function within the safety margins.
Implemented in a standard stepper motor driver, the sensorless load detection eliminates the need for reference or limit switches and reduces cost and complexity of applications where precise referencing is required. Normally, open-loop stepper drives lose step count in overload situations as they stall; for example, when an axis is obstructed. StallGuard prevents step loss, keeping step count integrity by stopping the motor when the set load value is reached. The sensorless technology can detect up to 1024 different load levels, allowing for high resolution feedback for continuous monitoring of the system.
FUTURE LOOKS BRIGHT FOR SOLAR ENERGY TECHNOLOGY
Clean, abundant, solar energy is expected to grow exponentially year-over-year, as technologies to enhance solar energy’s impact expand and evolve. Collaborations like between ADI and BrightSource will have a major effect in helping expansion and adoption of solar energy into the mainstream.
This partnership has resulted in what amounts to a two-prong approach to sustainability: ADI provides technical expertise and system solutions in the form of extremely precise, energy-efficient components; and BrightSource delivers extremely efficient, powerful, solar energy to help lessen reliance on fossil fuels.