NREL is a national laboratory of the U.S. Department of Energy

Office of Energy Efficiency and Renewable Energy

Operated by the Alliance for Sustainable Energy, LLC

ed NREL logo, June 15, 2009

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Assessing the Solar Resource

All CSP technologies use collectors to focus sunlight onto 

receivers in the process of converting solar energy to electricity. 

CSP systems rely on “seeing” the direct solar beam—known 

as Direct Normal Irradiance (DNI); consequently, measuring, 

mapping, and modeling the DNI resource are essential.

In the Solar Resource and Meteorological Assessment 

Project (SOLRMAP), NREL collaborates with multiple 

industry partners to collect precise, long-term solar resource 

measurements. This information helps to minimize the

technical and financial risks of new solar energy projects. 

Industry partners fund the cost of instruments, maintenance, 

and station operations; NREL provides expertise for station 

design, instrument selection, data acquisition, quality 

procedures, data analysis, calibrations, and data distribution. 

One objective of SOLRMAP is to acquire ground-based data 

that will help upgrade models that use satellite imagery to 

estimate solar radiation. NREL uses satellite images to 

generate hourly estimates of DNI and global horizontal 

irradiance across the United States. Higher-resolution models, 

now in development, feature 15- to 30-minute temporal and 

4-km x 4-km spatial resolution. NREL maintains the National 

Solar Radiation Database and other solar data and mapping 

resources at www.nrel.gov/rredc/solar_resource.html. 

Our primary tool for gathering and presenting DNI 

information is the Solar Power Prospector (http://mercator.

nrel.gov/csp/). The Prospector allows users to investigate the 

historic solar resource for individual 12-km x 12-km grids 

throughout the country, as well as to examine land topography 

and ownership. Proposed Renewable Energy Zones (REZs), 

solar-suitable brownfield sites, and other information are also 

provided. NREL analysts use the data to develop case-specific 

maps of solar potential for policymakers and for related 

studies, such as the Western Governors’ Association 

Renewable Energy Zones initiative.

The NREL resource assessment team is also developing 

methods for forecasting the solar resource. We are 

investigating data from sky imagers and short-term cloudmotion images to provide short-term forecasts up to six 

hours in the future. Standard weather forecasting models,

supplemented with mesoscale models, are used for dayahead and longer forecasts. The activities are coordinated 

with experts from the National Oceanic and Atmospheric 

Administration (NOAA), NASA, and international 

organizations.

Predicting Performance and Cost

With our models, users can predict the performance and 

cost of solar technologies at specific sites. The models can 

also help analysts assess the potential market penetration 

and economic impact of CSP under different policy and 

deployment scenarios.

The Solar Advisor Model (SAM) provides a consistent 

framework for analyzing and comparing power system costs 

and performance across the range of solar technologies and 

markets—from photovoltaic (PV) systems for residential and 

commercial markets to CSP and large PV systems for utility 

The Concentrating Solar Power (CSP) program at the National Renewable Energy Laboratory (NREL) measures and models 

the solar resource, develops and uses computer models for system performance and technology deployment modeling, and 

investigates the environmental benefits and impacts of utility-scale solar power.

Solar Resource and 

Meteorological 

Assessment Project 

(SOLRMAP) stations, like 

the one being installed 

here, collect solar resource 

measurements used to 

plan and locate new 

CSP plants. SOLRMAP is 

a collaboration between 

NREL and its partners 

in the energy industry.

PIX 16994; Credit, Tom Stoffel

Modeling and Analysis of CSP Systems 

Thermal Systems Group: CSP Capabilities
National Renewable Energy Laboratory

1617 Cole Boulevard, Golden, Colorado 80401

303-275-3000 • www.nrel.gov 

Printed with a renewable-source ink on paper containing at least 

50% wastepaper, including 10% post consumer waste.

NREL is a national laboratory of the U.S. Department of Energy

Office of Energy Efficiency and Renewable Energy

Operated by the Alliance for Sustainable Energy, LLC

NREL/FS-550-48661 • August 2010

markets. The software integrates an hourly simulation model 

with performance, cost, and finance models to calculate 

energy output, energy costs, and cash flows. SAM can also 

account for the effect of incentives on cash flows. Most of 

SAM’s inputs can be used as parametric variables for sensitivity 

studies to investigate the impacts of variations in physical, 

cost, and financial parameters on model results. SAM can be 

downloaded at https://www.nrel.gov/analysis/sam/.

The Regional Energy Deployment System (ReEDS) is an 

electric-sector capacity expansion model developed at NREL 

to model the future electric grid. In 2007, this tool was used to 

estimate the cost and transmission requirements of generating 

20% of U.S. electricity from wind power by 2030. CSP plants 

with storage and PV technologies have been added to the 

model, which is being used to perform solar deployment 

analyses for scenarios such as DOE’s Solar Vision Study.

Originally developed in 2002 for the DOE’s Wind Powering 

America project, the Job and Economic Development Impact 

(JEDI) model has been expanded to include the job and 

economic impacts of parabolic trough CSP facilities. The 

project-specific data include costs associated with constructing 

the facility, as well as equipment costs, other services, fees, and 

annual operating and maintenance costs. Users can include the 

portion of expenditures to be spent locally, financing terms, 

and local tax rates. JEDI provides reasonable default values for 

each of the inputs needed for the analysis, but users have the 

option to indicate project-specific data for most categories. 

The spreadsheet-based JEDI models can be downloaded at 

www.nrel.gov/analysis/jedi/.

Environmental Impact

The vast potential of utility-scale solar power has raised 

concerns about how the plants will affect the desert 

ecosystem. NREL is supporting the joint DOE/BLM 

programmatic Environmental Impact Statement (PEIS) being 

performed by Argonne National Laboratory (http://solareis.anl.

gov/). The PEIS will identify solar power impacts and 

mitigation methods. The project is also helping the BLM 

identify preferred zones for solar development.

Although PV and dish/engine CSP systems use no cooling 

water, trough and power tower CSP systems preferentially 

use water to cool their thermoelectric power cycle. Dry-cooling 

technologies can reduce CSP water consumption by more than 

90%, allowing CSP power plants to “grow” megawatts with less 

than one-twentieth the amount of water used by common 

southwestern crops. To save precious water resources while 

promoting clean solar power, NREL continues to investigate 

the best methods for integrating dry-cooling technologies into 

parabolic trough and power tower technologies. 

SolTrace

SolTrace is a software package that models solar power optical 

systems and analyzes their performance. Engineers can use it to 

develop complex solar optical designs that could not previously 

be modeled.

SolTrace can model parabolic trough collectors, point-focus 

concentrating systems, and power towers. It rapidly displays 

and saves data as scatter plots, flux maps, and performance 

graphs. SolTrace can model optical geometry as a series of stages, 

composed of optical elements that possess attributes such as 

shape, contour, and optical quality. It can also model any number 

of stages containing any number of different elements, and it 

features an extensive variety of available shapes and contours.

To enhance speed and portability, NREL is converting 

SolTrace to C++. The new version will incorporate a graphical 

user interface to aid in geometry design. It will interface with 

other solid modeling and finite-element analysis tools for input 

and, as an additional output option, it will provide performance 

data directly to the Solar Advisor Model. 

Contact Craig Turchi, Craig.Turchi@nrel.gov, 303-384-7565.

Thermal Systems Group: CSP Capabilities

The Solar Advisor Model (SAM) enables users to analyze and compare the cost, 

financing, and performance of solar power systems at specific sites. Shown here 

is a SAM interface displaying output data in several table and graph formats.

NREL