Name: Carrizo Energy Solar Farm: Proposed Thermal Plant and Land Transfer
Address: US

Overview

The Carrizo Energy Solar Farm was a proposed solar thermal power plant with an installed capacity of 177 MW, intended for development by the energy company Ausra. The project was situated in California's Carrizo Plain, specifically near the community of Simmler. Although the facility was designed to harness solar energy, the project ultimately reached a cancelled operational status and was never fully commissioned, despite initial plans for a 2010 start date.

The strategic selection of the Carrizo Plain was driven by specific grid infrastructure advantages rather than purely meteorological factors. While the region receives less direct sunlight compared to the Mojave Desert—a location that hosted several other solar thermal plants under consideration at the time—the Carrizo site offered significant logistical benefits. The primary advantage was its proximity to an existing high-voltage transmission line originally associated with the Diablo Canyon Power Plant. This existing infrastructure was expected to reduce both the capital cost and the construction timeline required to integrate the new solar capacity into the broader California grid.

Ausra, the designated operator and developer, aimed to leverage this transmission access to mitigate the typical interconnection delays faced by renewable energy projects in California. The 177 MW capacity was intended to contribute to the state's solar thermal portfolio, utilizing concentrated solar power (CSP) technology typical of Ausra's portfolio during that period. However, the project remained a proposal and did not advance to full operational status, reflecting the complex economic and infrastructural challenges facing large-scale solar thermal developments in the region during the early 2010s.

Project Specifications and Technology

The Carrizo Energy Solar Farm was designed as a 177 MW solar thermal power plant, utilizing concentrated solar power (CSP) technology rather than photovoltaic panels. The project was developed by Ausra, which specialized in the Compact Linear Fresnel Reflector (CLFR) technology for this installation. This specific CSP approach uses long, slightly curved mirrors to focus sunlight onto fixed elevated absorber tubes, distinguishing it from parabolic trough or power tower systems. The plant was intended to be located in California's Carrizo Plain, near Simmler. While this region receives less direct solar irradiance than the nearby Mojave Desert, the site selection was strategically driven by infrastructure advantages. The location is situated close to an existing high-voltage transmission line originating from the Diablo Canyon Power Plant. Proximity to this grid connection was projected to significantly reduce both the capital cost and the construction timeline for the solar farm.

Key Project Specifications

Parameter	Value
Installed Capacity	177 MW
Technology	Compact Linear Fresnel Reflector (CLFR)
Developer/Operator	Ausra
Location	Carrizo Plain, near Simmler, California
Estimated Cost	$550 million
Grid Connection	Diablo Canyon Power Plant transmission line

The project carried an estimated development cost of $550 million. Upon completion, the 177 MW capacity was projected to generate enough electricity to power approximately 60,000 homes. The integration with the Diablo Canyon transmission infrastructure was a critical component of the project's economic viability, allowing for efficient energy export to the broader California grid. The use of Ausra's CLFR technology aimed to offer a cost-competitive alternative to other CSP designs prevalent in the Mojave Desert during the same period.

Site Selection and Grid Integration

This specific site selection presented a strategic compromise between solar resource availability and grid infrastructure costs. While the location does not receive the highest levels of solar irradiance found in other prominent solar thermal development zones, it offered significant advantages in terms of transmission integration.

Solar Irradiance Comparison

The Carrizo Plain receives less direct sunlight compared to the Mojave Desert, a region that has become a primary hub for solar thermal power plant development. The Mojave Desert is noted for having several other solar thermal plants under consideration due to its superior solar resource potential. Despite the lower irradiance levels at the Carrizo site relative to the Mojave, the location was deemed viable for a 177 MW solar thermal facility operated by Ausra. The decision to proceed with the Carrizo site indicates that factors beyond peak solar yield, such as land availability and grid proximity, played a critical role in the project's feasibility analysis.

Grid Integration and Transmission Advantages

A key strategic advantage of the Carrizo Plain location is its proximity to existing high-voltage transmission infrastructure. The site is located near an existing transmission line originating from the Diablo Canyon Power Plant. This pre-existing grid connection significantly reduced both the cost and the time required to construct the plant's electrical interconnection. By leveraging the Diablo Canyon transmission line, the project aimed to minimize the capital expenditure typically associated with building new transmission corridors to remote solar sites. This integration strategy was intended to accelerate the project's timeline and enhance its economic competitiveness, compensating for the slightly lower solar irradiance compared to Mojave Desert alternatives.

Commercial Framework and Contracts

The commercial viability of the Carrizo Energy Solar Farm was anchored in a strategic Power Purchase Agreement (PPA) with Pacific Gas and Electric (PG&E), one of California’s largest investor-owned utilities. This contractual framework was designed to secure a stable revenue stream for the 177 MW solar thermal project, mitigating some of the financial risks associated with early-stage concentrated solar power (CSP) developments. The agreement with PG&E was critical for Ausra, the operator and primary developer, as it provided the off-take certainty necessary to justify the capital expenditure required for construction in the Carrizo Plain.

Levelized Cost of Energy

A key component of the project’s financial modeling was its claimed levelized cost of energy (LCOE), which was projected at 10.4 cents per kilowatt-hour. This cost metric was central to the project’s competitive positioning within the California energy market, particularly when compared to other renewable and conventional sources under consideration by PG&E. The 10.4 cents/kWh figure reflected the specific economic assumptions of the time, including anticipated solar irradiance levels, equipment costs, and operational expenditures for the solar thermal technology employed by Ausra.

While the Carrizo Plain receives less solar irradiance than the renowned Mojave Desert—a region that hosts numerous other solar thermal plants—the project’s financial model accounted for this geographical disadvantage. The lower insolation in the Carrizo Plain was partially offset by significant infrastructure advantages, most notably the proximity to an existing high-voltage transmission line from the Diablo Canyon Power Plant. This existing grid connection was expected to reduce both the capital cost and the time required for grid integration, thereby supporting the targeted LCOE of 10.4 cents/kWh.

Despite these favorable commercial terms and strategic location benefits, the Carrizo Energy Solar Farm ultimately remained a proposed project. The interplay between the PPA terms, the projected LCOE, and broader market dynamics—including fluctuations in solar technology costs and shifting utility procurement strategies—played a role in the project’s eventual status as cancelled. The financial framework established by the PG&E agreement and the 10.4 cents/kWh cost projection remains a notable case study in the economic challenges faced by early solar thermal developments in California.

Timeline of Development and Cancellation

The development of the Carrizo Energy Solar Farm followed a compressed timeline, moving from proposal to cancellation within a single year. The project was initially targeted for commissioning in 2010, positioning it as a rapid-entry solar thermal initiative in California. However, the operational status ultimately shifted to cancelled, with the final announcement made in November 2009. This decision coincided with the sale of the land, effectively concluding the immediate development phase for the 177 MW facility.

Year	Event
2009	Project cancellation announced in November; land sale initiated.
2010	Targeted commissioning date (pre-cancellation).

The cancellation in November 2009 marked a significant shift for the proposed 177 MW solar thermal power plant. Despite the strategic advantages of the location near Simmler in California's Carrizo Plain, the project did not proceed to construction. The site was selected for its proximity to an existing transmission line from the Diablo Canyon Power Plant, which was expected to reduce both the cost and time required for grid integration. Although the location receives less solar irradiance than the Mojave Desert, the transmission infrastructure was a key factor in the initial feasibility assessment. The decision to cancel the project and sell the land in November 2009 occurred before the 2010 commissioning target could be reached. Ausra, the operator behind the initiative, had planned to build the facility to leverage the nearby transmission capacity. However, the cancellation indicates that either financial, technical, or market conditions changed rapidly between the proposal phase and the end of 2009. The project remains a notable example of the volatility in early solar thermal development in California, where proximity to infrastructure did not guarantee completion. The land sale finalized the end of the immediate development efforts for this specific 177 MW capacity plan.

Why it matters

The Carrizo Energy Solar Farm represented a significant, albeit unrealized, milestone in the early development of concentrated solar power (CSP) technology in the United States. As a proposed 177 MW solar thermal facility, it highlighted the strategic competition between different solar technologies during a pivotal period of renewable energy expansion. The project was designed to utilize solar thermal technology, distinguishing it from the photovoltaic (PV) systems that have since dominated the solar market. This distinction is critical because solar thermal plants, like the one planned by Ausra, often incorporate thermal storage capabilities, allowing for more consistent power output compared to the variable generation of early PV installations. The choice of technology for Carrizo reflected a broader industry debate regarding the most efficient way to harness solar energy for grid stability and cost-effectiveness.

Strategic Location and Infrastructure Synergies

The project’s significance is further underscored by its strategic location in California's Carrizo Plain, near Simmler. While the region receives less solar irradiance than the nearby Mojave Desert, the site offered a compelling logistical advantage: proximity to an existing transmission line from the Diablo Canyon Power Plant. This infrastructure synergy was a key factor in the project's feasibility, as it significantly reduced the capital expenditure and time required to integrate the new solar capacity into the regional grid. By leveraging the Diablo Canyon line, the Carrizo project demonstrated how existing fossil fuel and nuclear infrastructure could be repurposed to support renewable energy integration, a concept that has become increasingly relevant in modern grid planning.

Impact on Regional Solar Development

Although the Carrizo Energy Solar Farm was ultimately cancelled, its planning and development phase contributed to the broader ecosystem of solar projects in California. The project’s evaluation of site-specific conditions, such as solar irradiance and transmission access, provided valuable data for subsequent developments in the region. Notably, the insights gained from the Carrizo proposal influenced the development of the Topaz Solar Farm, another major solar installation in the Carrizo Plain. The Topaz project, which successfully came online as a large-scale photovoltaic farm, benefited from the earlier analysis of the plain’s solar potential and infrastructure connections. The contrast between the cancelled solar thermal Carrizo project and the successful PV Topaz farm illustrates the evolving technological preferences and economic realities that have shaped California’s solar energy landscape.

What distinguishes solar thermal from photovoltaic technology?

Solar thermal energy, also known as concentrated solar power (CSP), differs fundamentally from photovoltaic (PV) technology in how it converts sunlight into electricity. While PV panels use semiconductor materials to generate direct current (DC) electricity when photons strike the surface, solar thermal plants use mirrors or lenses to concentrate a large area of sunlight onto a small receiver. This concentrated heat is then used to produce steam, which drives a turbine connected to a generator, effectively creating a traditional thermal power cycle. The Carrizo Energy Solar Farm was designed to utilize this thermal approach, specifically employing Compact Linear Fresnel Reflector (CLFR) technology developed by Ausra.

Compact Linear Fresnel Reflector Technology

The CLFR system used in the proposed Carrizo project represents a specific evolution of solar thermal design. Unlike parabolic troughs, which use curved mirrors to focus light onto a linear receiver tube, or power towers, which use hundreds of heliostats to focus light onto a central tower, CLFR technology uses long, flat or slightly curved mirror segments arranged in rows. These mirrors track the sun’s movement and reflect light onto fixed elevated absorber tubes. This design offers structural advantages, as the flat mirrors are often easier to manufacture and install than curved parabolic surfaces, potentially reducing balance-of-system costs. The heat collected in the absorber tubes is transferred via a heat transfer fluid to a steam generator, producing the steam necessary to drive the turbine-generator set. This thermal inertia allows for more straightforward integration of thermal storage systems, enabling the plant to continue generating electricity for several hours after sunset, a key advantage over standard PV systems.

Comparison with Photovoltaic Developments

The technological distinction between the proposed solar thermal plant and subsequent developments on the same land highlights the different engineering approaches to harnessing solar energy. While the Carrizo project by Ausra focused on thermal concentration using mirrors, later projects on the Carrizo Plain, such as those involving First Solar, utilized photovoltaic technology. PV systems convert sunlight directly into electricity without the intermediate step of generating steam. This means PV plants generally have fewer moving parts and can be more modular, but they typically produce power only when the sun is shining, unless paired with battery storage. The choice between solar thermal and PV often depends on factors such as land availability, transmission proximity, and the need for dispatchable power. The Carrizo Plain’s location, while receiving less direct sunlight than the Mojave Desert, offered proximity to existing transmission infrastructure from the Diablo Canyon Power Plant, a factor that influenced the initial selection of the solar thermal approach for the 177 MW project.

Carrizo Energy Solar Farm: Proposed Thermal Plant and Land Transfer