eSolar uses vertical mirrored towers of that perfectly concentrate sunlight on a ground target.

There are two ways to harness energy from the sun. One is through photovoltaic panels, which transform sunlight directly to electricity. But — news flash — the sunlight also produces heat, which can be concentrated using mirrors to produce steam, which then drives electric turbines. 

It’s this second form — called solar thermal or concentrated solar power — that has the most potential for utility-scale power generation. In fact, there are already solar thermal plants operating in the deserts of Nevada and California, using low rows of curved mirrors to concentrate sunlight.

But Bill Gross at eSolar thinks that he can improve on that fairly basic technology. Instead of rows of mirrors, eSolar uses vertical mirrored towers of that perfectly concentrate sunlight on a ground target. Using sophisticated software that Gross helped write himself — he was an Internet entrepreneur before breaking into alternative power — the mirrors perfectly track the sun as it crosses the sky, maximizing the amount of electricity that can be produced. The result is a relatively compact but power utility-scale plant that gets the most out of that free source of energy called the sun.

eSolar designs and develops Concentrating Solar Power (CSP) projects that start at 46MW and are scalable to any size.  eSolar power plant technology utilizes small, flat mirrors which track the sun with high precision and reflect the sun’s heat to a tower-mounted receiver, which boils water to create steam. This steam powers a traditional turbine and generator to produce solar electricity.

The simple concept of making renewable energy cost-competitive with fossil fuel energy has driven eSolar to engineer a paradigm shift in CSP technology, providing a cost-effective and scalable solution. eSolar partners with leading energy companies around the world to enable complete project capabilities, ranging from technology development and component manufacturing to power plant construction and operation.

eSolar was founded by the Pasadena-based business incubator Idealab in 2007 as a developer of concentrating solar power (CSP) plant technology. The company aims to develop a low cost alternative to fossil fuels through a combination of small heliostats, modular architecture, and a high-precision sun-tracking system.

eSolar has designed heliostats that are smaller than the industry norm, allowing for pre-fabrication, mass-manufacturing, and easy installation, thereby reducing production and installation costs.

eSolar has developed a sun-tracking control system that is able to calibrate heliostats and monitor the performance of each heliostat within the field. Tests have shown an unprecedented pointing accuracy and high thermal concentration ratios.

An array of heliostats reflect solar radiation to a tower mounted thermal receiver. The concentrated solar energy boils water in the receiver to produce steam. The steam is piped to a steam turbine generator which converts the energy to electricity. The steam out of the turbine is condensed and pressurized back into the receiver.

eSolar’s field layout design is built around the concept of scalable modules. Each module comprises several thousand heliostats arranged in two subfields – north and south – which track the sun and concentrate solar energy to the tower mounted receiver. The field layout is a simple, regular design that eliminates precision surveying and ground penetration.

A 46 MW eSolar power unit consists of sixteen heliostat fields and towers, a single steam turbine generator set, and a steam condenser, with a typical footprint of approximately 100 hectares (250 acres). These basic 46 MW units are designed to be scaled up to fit specific power requirements.

In the summer of 2009, eSolar unveiled the 5 MW Sierra SunTower plant, a commercial facility in Lancaster, California that demonstrates the company’s technology. Sierra SunTower is interconnected to the Southern California Edison (SCE) grid and, as of spring 2010, is the only commercial CSP tower facility in North America.

Sierra SunTower includes two eSolar modules. 24,000 heliostats, divided between four sub-fields, track the sun and focus its energy onto two tower-mounted receivers. The focused heat converts feedwater piped to the receivers into superheated steam that drives a reconditioned 1947 GE turbine generator to produce electricity. The steam passes through a steam condenser, reverts back to water through cooling, and the process repeats.

During the 12 months of construction, Sierra SunTower created over 300 temporary jobs. In operation, the site employs 21 permanent employees. Sierra Suntower has been certified by the California Energy Commission as a renewable energy facility. Power from the facility is sold under a Power Purchase Agreement (PPA) with SCE, providing renewable energy for up to 4,000 homes.

The 5 MW output from Sierra SunTower reduces CO2 emissions by 7,000 tons per year, an amount equivalent to planting 5,265 acres (21.31 km2) of trees, removing 1,368 automobiles from the road, or saving 650,000 gallons of gasoline.

NRG Energy, Inc. partnered with eSolar in February 2009 to develop solar power plants with a total generation capacity of up to 500 MW at sites within California and across the Southwestern United States. Additionally, NRG invested approximately $10 million for equity and associated development rights for three projects and a portfolio of PPAs to develop, build, own and operate up to 11 eSolar modular solar generating units at these sites. The development assets will use eSolar’s concentrating solar power (CSP) technology to sell renewable electricity under contracted PPAs with local utilities seeking competitively priced, zero-carbon solar power

In June 2008, eSolar signed a PPA with Southern California Edison (SCE) – the largest electric utility in California – to build a total of 245 MW of concentrating solar power plants. In June 2009, eSolar partnered with NRG Energy (NYSE: NRG) to develop a 92 MW solar power plant under a PPA with El Paso Electric Company. This contract is the first and only contract to deliver solar thermal power in New Mexico and will help El Paso Electric meet its renewable portfolio goals. eSolar has further projects under development with NRG in California.

In June 2009, Pacific Gas and Electric Company teamed with eSolar and NRG for 92 MW of renewable solar thermal power. PG&E delivers some of the nation’s cleanest energy to 15 million people in northern and central California.

1. How Their System Works

A field of sun-tracking heliostats reflects solar heat to a thermal receiver mounted atop a central power tower. The focused heat boils water within the thermal receiver and produces steam. The plant pipes the steam from each thermal receiver and aggregates it at the turbine, powering a power generator. The steam then reverts back to water through cooling, and the process repeats.

2. Patented Heliostat Design

A small and mass-manufactured heliostat is the building block of the eSolar® solution. eSolar designed the heliostats for deployment in pre-fabricated "heliostat sticks" that can be installed easily with a minimum of training. Low wind profile design allows fields of eSolar® heliostats to be installed faster than any competitive CSP solutions.

3. Modular Field Layout

Thousands of systematically spaced heliostats combine to form the eSolar® modular field, comprised of north and south facing mirror sub-fields. Both mirror fields concentrate sunlight to a thermal receiver mounted atop a central tower. The sub-field design optically optimizes the layout to maximize the harvested thermal energy.

4. Scalable Units

A 46 MW eSolar® power unit consists of 12 towers (each with its own north-south heliostat sub-field), a turbine generator set, and a steam condenser. 46 MW power units fit on approximately 100 hectares (250 acres). eSolar can construct multiple 46 MW units scalable to any required size of output.

Partners With Penglai on Landmark Solar Thermal Agreement For China

eSolar, a global provider of reliable and cost-effective concentrating solar power (CSP) plants, and Penglai Electric, a privately-owned Chinese electrical power equipment manufacturer, today announced a master licensing agreement to build at least 2 gigawatts (GW) of solar thermal power plants in China over the next 10 years.

The deal was signed in the Chinese State Council building with government officials in attendance and represents the country’s largest CSP project.

Penglai Electric plans to develop 2 GW of power plants by 2021 using eSolar’s proven solar thermal technology. The solar thermal power plants will be co-located with biomass electricity generation facilities. Penglai Electric will leverage local manufacturing to source some of the equipment. In total, the plants will eliminate 15 million tons of carbon dioxide emissions annually.

"Using the power of the sun, eSolar’s technology minimizes the environmental impact on manufacturing and deployment while maximizing land and cost efficiency," said Liu Guangyu, chairman and CEO of Penglai Electric. "We are extremely grateful to the Chinese government for playing a major role in promoting zero-carbon renewable energy."

"With Penglai as our partner and with the strong support of the Chinese government, eSolar is proud to be the first company to deliver the benefits of cost-effective solar thermal power to China," said Bill Gross, founder and chairman of eSolar.

China Huadian Engineering Co. will lead the construction process. At completion, China Shaanxi Yulin Huayang New Energy Co. will own and operate the first 92 MW plant. "To date, eSolar offers the only CSP tower technology that has demonstrated commercial maturity and economic feasibility," added Zhao Weikang, chairman and president of Shaanxi Yulin Huayang New Energy Co. "We’re excited to build our initial hybrid plant as part of the 170-square kilometer Yulin Alternative Energy Park, the first large scale alternative energy park in China. Our work is aligned with the government’s continuing policy to curb carbon emissions and combat climate change."

China is currently the market leader in the PV manufacturing industry. The deal represents the country’s first major move into concentrating solar thermal power. The Chinese government recently announced its aggressive plans to increase the country’s renewable power generation capacity to 15 percent by 2020.

China Shandong Penglai Electric Power Equipment Manufacturing Co., Ltd was founded in 1987 as the preferred vendor for the state-owned Chinese Power Complete Equipment Co., Ltd (CPCEC) and the Chinese Academy of Electric Power Design ( Penglai Electric is one of the many independently owned and operated enterprises conceived as a result of the Chinese economic reform.

With its own core team of about 1,000 employees, its main line of business includes manufacturing auxiliary and energy-saving components for 200MW, 300MW, and 600MW to 1,000MW fire-powered electrical power plants. Since 2001, Penglai Electric Power has been granted ISO9001 quality assurance and self import and export privileges. By synergistically combining its technical expertise, manufacturing capability, and trading know-how, Penglai Electric offers comprehensive solutions in research and development, technical consultation, auxiliary component introduction and manufacturing, installation, and tuning for more than 60% of the major fire-powered electrical plants in China. Penglai Electric is based in Penglai, Shandong, China.

eSolar is an Idealab company founded in 2007 to develop modular and scalable solar thermal power plant technology. In the summer of 2009, eSolar unveiled the 5 MW Sierra SunTower Plant, the only commercial CSP tower facility in North America. The eSolar solution marries a low-impact, pre-fabricated form factor with advanced computer software engineering to meet the demand for reliable and cost-competitive solar energy. eSolar’s proprietary solution resolves issues of price, scalability, speed of deployment, and grid impact that have historically stymied solar thermal adoption, thus affording dramatic reductions in the cost of solar thermal energy. eSolar is based in Pasadena, California.