Concentrating Solar Power with Thermal Energy Storage

Bill Gould, CTO, SolarReserve
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Bill Gould, CTO, SolarReserve

Bill Gould, CTO, SolarReserve

Concentrating Solar Power (CSP) with Thermal Energy Storage (TES) technology utilizes large tracking mirrors to focus sunlight onto a heat exchanger, where the sun’s thermal energy is captured in a fluid. By using molten salt as both a heat transfer fluid as well as thermal energy storage medium, CSP plants are able to efficiently and cost effectively capture and store the sun’s energy.

SolarReserve’s 110 Megawatt Crescent Dunes CSP Facility in Nevada, with 1.1 Gigawatt-Hours of Energy Storage

As a result, CSP with energy storage is about to play an increasingly key role in the growing clean energy landscape, both here in the U.S. and internationally. Among the most compelling reasons for its adoption are:

1. Ability to meet peak demand
2. Rapidly declining installation costs
3. Local economic benefits, including—high level of content and service localization

Meeting Peak Demand

Curtailment issues and ability to meet shifting peak demand are becoming increasingly critical in California and other global markets with high solar penetration. These issues are reducing the future value of renewables without storage. For example, the peak demand period for Pacific Gas and Electric Company, one of the largest combination natural gas and electric utilities in the United States that provides service to approximately 16 million people in northern and central California, is now from 4 p.m. until 9 p.m., having shifted from an early afternoon peak to an evening peak. Time of Day (TOD) pricing adjustments once provided a substantial boost (about 25 percent) to solar projects, due to the much earlier peak period–but now that parts of the state are awash in new large-scale and rooftop PV, PG&E’s TOD tables have been steadily adjusted such that new solar installations without storage are no longer viable.

  Concentrating Solar Power with energy storage is about to play an increasingly key role in the growing clean energy landscape, both here in the U.S. and internationally 

As the California utilities start deploying more renewables in order to meet the state’s target to get 50 percent of its energy from renewable resources by 2030, the need for renewables with energy storage will grow. Since CSP with TES provides both renewable energy generation as well as bulk energy storage– and is one of the lowest cost bulk energy storage technologies on the market–we do anticipate that the utilities will include CSP with integrated molten salt energy storage as part of their overall portfolio.

On the other side of the world, South Africa’s Renewable Energy Independent Power Producer Procurement Program is driving cost-reduction and innovation that is having a global impact. Under this progressive program, the South Africa Department of Energy has included bidding rounds for CSP plants with energy storage. South Africa’s grid is challenged with increasing demand due to a growing economy. Their peak demand period extends into the evening hours, which is the time of day that the country has been suffering from rolling blackouts due to inability of their utility to meet that demand. Lower cost PV simply can’t meet early morning and evening peak demand (before sunup and after sundown). So CSP with storage provides two advantages: 1) It provides non-intermittent base load power that is more easily integrated into their existing grid and 2) It actually provides real capacity to reliably meet demand during their peak hours, which extends to 9:30 PM.

China is also experiencing similar issues with intermittent renewables and their inability to meet peak evening demand, and are turning toward CSP with energy storage, with a target to build 10,000 megawatts of CSP over the next five years. Not only will CSP with TES provide non-intermittent power to meet their peak demand, the technology will be able to facilitate the deployment of additional wind and PV generation, while ensuring the reliability and security of the new ultra-high voltage transmission lines being constructed to bring clean, renewable power from the north and west regions of China to load centers in the east.

With the agreement signed at COP21, countries pledged to focus further on developing clean, renewable energy sources and move away from the use of fossil fuels. This will clearly bolster the already remarkable growth in renewable energy, and as renewable energy penetration grows, the need for utility-scale renewable generation with storage technology is increasingly important to mitigate intermittency problems, deliver power into peak demand periods, and support transmission system reliability.

Declining Installation Costs

CSP with storage is set to realize falling installation costs as global deployment accelerates. It is a relatively young technology, with a strong roadmap for performance improvements, optimization and cost reduction. Future projects are already seeing 30 percent reductions in capital costs.

SolarReserve is realizing substantial cost optimizations in their CSP with TES technology, including cost and efficiency improvements for their next generation projects. Their 100 MW Redstone South African project with 12 hours of energy storage will earn $125/MWh, without subsidies. This project is designed to operate until 10pm, meeting the South African utility’s peak demand period. The company’s 260 MW Copiapó Chilean project with 13 hours of energy storage will bid at well under $90/MWh, without subsidies. This project is designed as a baseload facility, to meet Chile’s 24/7 demand for power.

It is important to keep in mind that CSP with TES is delivering both energy generation and energy storage, at a combined price. If you separated out the cost of equivalent battery storage, the remaining cost associated with generation would be very competitive with even the lowest PV or wind power prices.

Economic Benefits

SolarReserve’s Crescent Dunes 110 MW project is an example of potential job creation –it has created over 4,300 direct, indirect and induced jobs over the life of the project, with peak on-site employment of over 1,000 construction jobs, including more than 70 subcontractors (about 60 percent of the total) from the state of Nevada where the project is located.

Importantly, CSP projects provide an enormous opportunity for local content. Again using the Crescent Dunes project as an example, equipment and services were purchased across 26 states. All 1.2 million square meters of glass was U.S. sourced, with assembly completed in an on-site manufacturing facility that employed local workers. Virtually all of the 90,000 cubic meters of concrete required for the project was provided from a local supplier. All 2,000 tons of structural steel was U.S. sourced as was most of the piping, cabling and valves.

The breakthrough solar energy storage technology we are utilizing at SolarReserve is just one example of how American innovation finds answers to complex problems–and also can create jobs by the thousands.

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