NREL's concentrating solar power (CSP) program develops models for engineering design, system performance, and technology deployment while investigating the value of dispatchable utility-scale solar power to regional grid networks.
Technology Cost Benchmarking and Roadmapping
We track the cost and performance of CSP technologies. Data on installed CSP projects around the world is compiled in collaboration with SolarPACES—Solar Power and Chemical Energy Systems—and is available on our Concentrating Solar Power Projects database.
We provide cost benchmarking of CSP technologies and current costs and future cost projections for CSP technologies, specifically as part of NREL's Annual Technology Baseline. This information is also used to update the default costs for CSP technologies in the System Advisor Model (SAM) annually. We use the insights from this analysis to identify promising research paths to reduce overall CSP costs in technology roadmaps.
Bottom-Up Cost Analysis
NREL performs bottom-up cost analysis of CSP components. We use tools such as Design for Manufacturing Analysis to assess the impact of materials, design, and manufacturing volume on the cost of high-volume components such as heliostats and parabolic troughs. We analyze power tower receiver and thermal energy storage tank costs using a bottom-up approach that assesses the component design compared to its performance requirements and estimates costs based on material and fabrication specifications.
Model and Software Development
NREL-developed models and software are the tools used to perform techno-economic analysis and are available to the public as open-source code. NREL developed and maintains SolTrace and SolarPILOT to model CSP system optical performance and optimize solar field layouts. We also maintain and update the CSP modules in SAM, such as adding submodels like the supercritical carbon dioxide power cycle option or optimizing dispatch to maximize revenue.
Power Dispatch Optimization and Grid Integration
CSP, coupled with thermal energy storage, offers a uniquely dispatchable renewable resource. As the amount of wind and solar on the grid increases, the rest of the grid must adjust and adapt to accommodate their variable, nondispatchable generation.
NREL analysts quantify the value of CSP with thermal energy storage to the grid. Using a CSP dispatch optimization model in SAM, we optimize CSP plant design and operation based on the time of delivery pricing from grid operators. Conversely, we can measure potential benefits of CSP to a given grid using utility-scale production cost models such as PLEXOS, NREL's Resource Planning Model, and Regional Energy Deployment System Model.
Maps and Geographical Information Systems
The Resource Information and Forecasting group provides the necessary solar data, satellite imagery, and GIS to help analysts and stakeholders better understand the feasibility of locating a CSP plant in a particular area.
- Design for manufacturing analysis
- Bottom-up cost analysis
- Grid optimization modeling
- Technology benchmarking
- System analysis and model development
This project develops software that identifies the optimal operations schedule for an operating plant in a real-time setting based on best-available weather and pricing forecasts, costs, and operational requirements. CSP systems with thermal storage are capable of responsive operation as market or weather conditions vary but are burdened with an abundance of possible operational schedules that satisfy the engineering requirements of the system. Often, trade-offs between near-term revenue gains and long-term costs due to component degradation and maintenance are opaque to plant operators.
This project will leverage prior work on SAM, in CSP dispatch optimization, and in direct normal irradiance forecasting to provide a software tool to be used in situ at operating facilities to execute optimal operational strategies. A tool that automates certain decision-making processes offers several key advantages, including the ability to:
- Simultaneously account for operational factors beyond the knowledge of human operators
- Identify a provably optimal operations schedule
- Generate consistent and improved plant performance across the industry
- Reduce long-term maintenance costs
- Produce smaller modular designs by streamlining operations costs.
This project increases plant revenue while decreasing wear and tear on the plant and long-term maintenance and replacement costs.
Commercial CSP power tower plants use an external receiver to convert sunlight reflected from the solar field to thermal energy. SunShot's 90% annual average receiver efficiency target is a challenging metric for receivers planned to operate at 700°C and above. Cavity receiver designs have a higher optical and thermal efficiency than external receivers but can only be used effectively with shorter towers and smaller fields
This project will develop a cavity-receiver design option for SAM's molten-salt power tower model. The task will develop the framework for a cavity receiver model and demonstrate the model's ability to estimate optical and thermal losses for representative geometries. The model will then be added to the SAM interface and used to perform a case study of a <50-MWe system interfaced with a supercritical carbon dioxide power cycle.
SAM does not include cavity receivers as an option, which limits NREL's ability to evaluate the potential benefits of these smaller-tower designs. The work will allow analysis of small, modular tower systems.
For the CSP Gen3 effort, three potential pathways were identified, each using a different phase of matter to collect and transport thermal energy from the receiver: liquid, particles (solid), and gaseous. The particles (solid) Gen3 pathway was selected to proceed to the demonstration phase. This is expected to be the dominant design for future CSP power tower plants.
SAM has a CSP power tower model that uses molten salt as the heat transfer and storage fluid. This effort will incorporate the particle pathway into the SAM CSP model and will include new subcomponent models for receivers, thermal energy storage, heat exchangers, and piping using materials not previously considered for SAM.
The addition of this Gen3 model into SAM will enable CSP system cost analysis of the particle pathway design to support Department of Energy R&D goals as the Gen3 program progresses.
Technoeconomic Cost Analysis of NREL Concentrating Solar Power Gen3 Liquid Pathway, Online Event: SolarPACES (2020)
CSP Systems Analysis - Final Project Report , NREL Technical Report (2019)