About Sierra SunTower

eSolar heralds a new era of solar energy with the unveiling of Sierra SunTower. Challenges that once thwarted widespread solar thermal power generation — including cost, speed of deployment, and environmental sustainability — have now been met. eSolar delivers a new blueprint for solar energy in California and beyond.

Sierra SunTower supplies 5 MW of clean, renewable energy to the grid. The full-scale power plant, the first commercial CSP tower in the United States, supplies electricity to Southern California Edison (SCE) and will power up to 4,000 homes.


  • Southern California Homes – Sierra SunTower will produce 5 MW of electricity powering up to 4,000 homes.
  • Job Creation – The project created over 250 construction jobs and 6 permanent jobs.
  • Local Community – Sierra SunTower provides a new local tax base, as well as direct and indirect economic benefits during development, construction and operation.
  • Greenhouse Gases – 5 MW of clean solar power generation will offset more than 7,000 tons of CO2 each year.
  • Clean and Reliable – Efficient and clean solar power is reliably available during peak demand.

Environmental Facts

The 5 MW output of Sierra SunTower will reduce CO2 emissions by 7,000 tons per year. For perspective, Sierra SunTower’s annual impact is equivalent to:

  • Planting 5,265 acres of trees
  • Removing 1,368 automobiles from the road
  • Saving 650,000 gallons of gasoline

The Construction and History of Sierra

With the learning from Littlerock, it was time for eSolar to test our ideas of large scale mass-manufacturing and modular field design in a commercial project which gave rise to the Sierra SunTower project starting in 2009. eSolar worked with manufacturing partners to develop an automated assembly line used to create over 24,000 heliostats. eSolar designed every part for easy manufacturing, shipping and installation.

eSolar's pre-fabricated mirror frames fit easily into standard shipping containers for delivery to the site.

eSolar’s pre-fabricated mirror frames fit easily into standard shipping containers for delivery to the site.

The eSolar field layout employs repeating geometries that eliminates the need for high-precision surveying and ground penetration.

The eSolar tessellated field layout eliminates the need for high-precision surveying and ground penetration.

eSolar's small, flat mirrors are installed using basic hand tools. Deployment is fast, efficient, and requires a minimum of training thereby reducing on-site labor costs.

Our small mirrors are installed with basic hand tools requiring little training and reducing on-site labor costs.

eSolar developed this project from start to finish, covering all aspects of the project lifecycle, even designing the first generation Solar Receiver System (SRS) used on this site. Sierra Sun Tower demonstrated eSolar’s goals of commercial viability and rapid deployment by going from initial ground-breaking to supplying electricity to the grid in less than twelve months.

Sierra Sun Tower’s commissioning marked very important firsts:

  • The first time Spectra, eSolar’s control software, integrated with a real power plant’s Distributed Control System (DCS)
  • The first time we used mass-produced wind turbine industry monopoles to hold our solar receivers
  • The first time we were able to convert our steam into electricity

eSolar has collected much more than just solar thermal energy at Sierra, we have collected an immense amount of data, knowledge and experience. Since the completion of Sierra, we have improved and tested new ideas at the site including:

  • Partnering with B&W to test eSolar’s Solar Collector System (SCS) on a different solar receiver
  • Upgrading one of its fields with all new electronics
  • Implementing a new generation Spectra, including large improvements in our throttle control, aim-point management, and calibration process

The process of upgrading a field, rolling out new software and firmware and designing against a new solar receiver provided even more lessons and experience for the eSolar team.

Sierra SunTower Field 2 producing electricity from steam with the B&W Direct Steam Solar receiver

Sierra SunTower Field 2 producing electricity on B&W’s External Solar Receiver.

Sierra SunTower Field 1 producing electricity.

Sierra SunTower Field 1 producing electricity on eSolar’s Internal Cavity Receiver.