About the Solar Advisor Model |

| Overview
The Solar Advisor Model Version 2010 is a performance and economic model designed to facilitate decision making for people involved in the solar energy industry, ranging from project managers and engineers to incentive program designers, technology developers, and researchers. Solar Advisor makes performance predictions and economic estimates for grid-connected solar power projects in the distributed and central generation markets. The model calculates the cost of generating electricity based on information you provide about a project's location, installation and operating costs, type of financing, applicable tax credits and incentives, and system specifications. The Solar Advisor Model can be downloaded for free from the Solar Advisor website https://www.nrel.gov/analysis/sam/. Solar Advisor is based on an hourly simulation engine that interacts with performance, cost, and finance models to calculate energy output, energy costs, and cash flows. The software can also account for the effect of incentives on project cash flows. Solar Advisor's spreadsheet interface allows for exchanging data with external models developed in Microsoft® Excel. The model provides options for parametric studies, sensitivity analysis, optimization, and statistical analyses to investigate impacts of variations and uncertainty in performance, cost, and financial parameters on model results. Solar Advisor models system performance using the TRNSYS software developed at the University of Wisconsin combined with customized components. TRNSYS is a validated, time-series simulation program that can simulate the performance of photovoltaic, concentrating solar power, water heating systems, and other renewable energy systems using hourly resource data. TRNSYS is integrated into Solar Advisor so there is no need to install TRNSYS software or be familiar with its use to run Solar Advisor. The Department of Energy's Solar Energy Technologies Program (SETP) initially developed Solar Advisor for analysis to support the implementation of the SETP Systems Driven Approach. The model also has applications for the solar industry for planning research and development programs, and developing project cost and performance estimates. Solar Advisor is being used as part of the solicitation and evaluation process for SETP funding programs. The current version of the Solar Advisor Model models photovoltaic and concentrating solar power technologies for electric applications in several markets. Solar Advisor also includes a simple model of fuel-based electric generation that can be used to model baseline systems for comparison with the solar technologies. The current version of the Solar Advisor Model does not model solar heating and lighting technologies.
| Photovoltaic Systems
Solar Advisor models grid-connected photovoltaic systems that consist of a photovoltaic array and inverter. The array can be made up of flat-plate or concentrating photovoltaic (CPV) modules with one-axis, two-axis, or no tracking. The current version of the software includes simple models of loads and storage for grid-connected systems with electric storage batteries.
• | See Photovoltaic Systems for a detailed description of the photovoltaic models.
Flat-plate Module Options
• | Simple efficiency
• | Sandia PV Array Performance Model
• | CEC Performance Model
• | PVWatts Solar Array (models a complete system)
Concentrating Photovoltaic (CPV) Module Options
• | Simple efficiency
Inverter Options
• | Single-point efficiency
• | Sandia Performance Model for Grid-Connected PV Inverters
Storage and Loads Options
• | A prototype model is available for testing
The simple efficiency models are simplified representations of either modules or inverters based on rated capacities in Watts or kilowatts and efficiency values. The flat-plate PV simple efficiency model also includes a simple representation of module temperature effects. The Sandia and CEC models include parameter libraries for commercially available PV modules and inverters maintained by Sandia National Laboratories and the California Energy Commission (CEC), respectively. Modules and inverters only recently introduced to the market may not be available in the parameter libraries.
| Concentrating Solar Power Systems
Solar Advisor models parabolic trough, power tower, and dish-Stirling concentrating solar power systems. The trough model is based on NREL's Excelergy model. The dish-Stirling and power tower models are based on research at the University of Wisconsin. Parabolic Trough A parabolic trough system is a type of concentrating solar power (CSP) system that collects direct normal solar radiation and converts it to thermal energy that runs a power block to generate electricity. The components of a parabolic trough system are the solar field, power block, and in some cases, thermal energy storage and fossil backup systems. The solar field collects heat from the sun and consists of parabolic, trough-shaped solar collectors that focus direct normal solar radiation onto tubular receivers. Each collector assembly consists of mirrors and a structure that supports the mirrors and receivers, allows it to track the sun on one axis, and can withstand wind-induced forces. Each receiver consists of a metal tube with a solar radiation absorbing surface in a vacuum inside a coated glass tube. A heat transfer fluid (HTF) transports heat from the solar field to the power block (also called power cycle) and other components of the system. The power block is based on conventional power cycle technology, using a turbine to convert thermal energy from the solar field to electric energy. The optional fossil-fuel backup system delivers supplemental heat to the HTF during times when there is insufficient solar energy to drive the power block at its rated capacity. Solar Advisor includes two parabolic trough models:
• | The physical trough model represents system component performance based on heat transfer and thermodynamic principles.
• | The empirical through model uses a set of equations to represent system component performance based on empirical data obtained from analysis of the performance of installed systems.
Dish-Stirling A dish-Stirling system is a type of concentrating solar power (CSP) system that consists of a parabolic dish-shaped collector, receiver and Stirling engine. The collector focuses direct normal solar radiation on the receiver, which transfers heat to the engine's working fluid. The engine in turn drives an electric generator. A dish-Stirling power plant can consist of a single dish or a field of dishes.
• | See Dish Stirling for information about the dish-Stirling model.
Power Tower A power tower system (also called a central receiver system) is a type of concentrating solar power (CSP) system that consists of a heliostat field, tower and receiver, power block, and optional storage system. The field of flat, sun-tracking mirrors called heliostats focus direct normal solar radiation onto a receiver at the top of the tower, where a heat-transfer fluid is heated and pumped to the power block. The power block generates steam that drives a conventional steam turbine and generator to convert the thermal energy to electricity. Solar Advisor models power tower systems similar to the Solar Two system that use molten salt as the heat transfer fluid with external, cylindrical receivers. It models two-tank thermal energy storage systems.
• | See Power Tower for details about the power tower model.
| Generic (Fuel-based) Systems
The generic system model is a basic representation of a conventional fossil-fuel power plant. The Generic technology option makes it possible to compare analyses of photovoltaic and concentrating power systems to a base case conventional fossil fuel plant in the residential, commercial and central generation markets.
• | See Generic Fossil for details about the generic fossil model.
| Solar Water Heating
The solar water heating model calculates the hourly thermal output and energy savings of a two-tank glycol system with an auxiliary electric heater with storage tank for residential or small commercial applications. Solar Advisor allows you to vary location, hot water load profiles, and the characteristics of the collector, heat exchanger, and solar tank. Future versions of the model include more system types for residential, commercial, and industrial applications. With some knowledge of solar water heating systems and modeling, you can use the current version to model a natural gas auxiliary heater. See Solar Water Heating for details about the solar water heating model.
| Financial and Incentive Models
Solar Advisor's economic model calculates a project's cash flow over an analysis period that you specify. The cash flow captures installation and operating costs, taxes, incentives, and the cost of debt. Solar Advisor uses the system's hourly output for a single year generated by the performance model, and then calculates a series of annual cash flows for revenues from electricity sales and incentive payments, tax liabilities (accounting for any tax credits for which the project is eligible), and loan principal and interest payments. Solar Advisor reports a set of economic metrics such as the levelized cost of energy that it calculates from the cash flow. Solar Advisor also generates a detailed cash flow table that you can use to evaluate a project's value. The economic model can represent projects in the residential, commercial, and utility markets, and account for a wide range of incentive payments and tax credits, which can be based on investment amounts, capacity ratings, and annual electricity production. Residential and commercial projects are assumed to be financed through either a loan or cash payment, and to recover investment costs by selling electricity through either a net metering or time-of-use pricing agreement. For these projects, SAM reports a payback period and net present value in addition to the detailed cash flow table. Utility and commercial third-party projects are assumed to sell electricity through a power purchase agreement at a fixed price with optional annual escalation, and to be required to meet a set of financing constraints. For utility projects, SAM calculates an electricity sales price, internal rate of return, and minimum debt service coverage ratio. Projects with commercial and utility financing can be modeled with or without depreciation using MACRS depreciation schedules or customized schedules. Solar Advisor includes a set of sample templates that contain default cost values that can be used as a starting point for analyses. The default cost values are representative of average U.S. costs at the time of the model's release, but of course do not capture the actual costs for any specific project. For more information about Solar Advisor's cost inputs, see the system costs page for each technology:
• | PV System Costs
• | Trough System Costs for the empirical trough model, and for the physical trough model
• | Dish System Costs
• | Tower System Costs
• | Fossil System Costs
• | Solar Water Heating System Costs
For more details about the financial and incentive modeling see:
• | Financing
• | Tax Credit Incentives
• | Payment Incentives