# Presentation: 784408

## Use and Validation of theSolar Advisor Modelfor Photovoltaic Applications

- Chris Cameron
- Solar Systems Department
- Sandia National Laboratories
- March 13, 2008

- Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company,for the United States Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000.

## Why Levelized Cost of Energy?
To measure cost-competiveness of solar energy
Cost-competitiveness key to very wide-scale use
Absent policy drivers
Looking beyond incentives, net metering, and green markets
Metric that captures all economic costs
Unlike manufacturing cost ($/Wp), module efficiency, etc.
Note – other metrics, e.g. first cost, ROI, etc. may be more important in the market place
SAM developed to enable use of LCOE metric
Also supports “Systems-Driven Approach*” to technology development

- To measure cost-competiveness of solar energy
- Cost-competitiveness key to very wide-scale use
- Absent policy drivers
- Looking beyond incentives, net metering, and green markets
- Metric that captures all economic costs
- Unlike manufacturing cost ($/Wp), module efficiency, etc.
- Note – other metrics, e.g. first cost, ROI, etc. may be more important in the market place
- SAM developed to enable use of LCOE metric
- Also supports “Systems-Driven Approach*” to technology development

**Levelized Cost of Energy**

- *Chris Cameron and Craig Cornelius, “A Systems-Driven Approach to Solar Energy R&D”, http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=4304320

## Market analysis to establish targets
Reference system designs for target markets
Technology Improvement Opportunities (TIO’s)
Reduce cost, increase performance and reliability 
Perform Parametric Analysis to downselect TIO’s
Pursue multiple pathways to reduce risk
Measure Progress
Apply stage-gate management to evaluate progress

- Reference system designs for target markets
- Technology Improvement Opportunities (TIO’s)
- Reduce cost, increase performance and reliability
- Perform Parametric Analysis to downselect TIO’s
- Pursue multiple pathways to reduce risk
- Measure Progress
- Apply stage-gate management to evaluate progress

**Systems-Driven Approach**

## Targets defined relative to market prices
Market prices reflect analysis of Energy Information Administration data
Residential/Commercial market prices based on utility rates
Utility market price based on Levelized Cost of Energy (LCOE) from new combined-cycle gas turbine in SW US
Nondispatchable power has a market price of 4¢/kWh

- Market prices reflect analysis of Energy Information Administration data
- Residential/Commercial market prices based on utility rates
- Utility market price based on Levelized Cost of Energy (LCOE) from new combined-cycle gas turbine in SW US
- Nondispatchable power has a market price of 4¢/kWh

**Market Analysis**

| Market | Residential | Commercial | Utility |
| --- | --- | --- | --- |
| U.S. Market Price (2005) | 5.8-16.7 | 5.4-15.0 | 4.0-7.6 |
| PV Targets | 8-10 | 6-8 | 5-7 |

**Solar Program 2015 Targets (¢/kWh)**

**Example Analysis**

- Impact of Inverter on First- and Life-Cycle Cost
- Residential System
- Note the impact of Operation and Maintenance Cost (O&M)
- Suppose a 2 kW System at $5/W installed
- Annual output ~ 4,000 kWh
- @ 10 ¢/kWh, system output is worth $400/yr
- No room for $100 service calls
- PV modules may be reliable
- What about the inverter?

## Inverter Contribution to LCOEAnalysis and Assumptions

- 5

- $0.90

**Inverter Contribution to LCOE****Analysis and Assumptions**

**0.3 ¢/kWh****0.4 ¢/kWh**

**0.8****¢/kWh**

**6.9 ¢/kWh****2.6 ¢/kWh**

**2.4¢/kWh**

**1.8¢/kWh**

**1.9 ¢/kWh****0.9 ¢/kWh**

** **
** **
** ****Inv. Lifetime (yrs)**
**Sys O&M****(% of installed cost)**

- $0.69
- 100.3%

- $0.30
- 200.2%

**Cost of Replacement/Repair (parts and labor) at end-of-life assumed to be same as component cost of original inverter in nominal dollars,**e.g. original inverter cost $2,000 in 2005, cost to replace in 2015 is $2,000in 2015 $’s, including parts and labor (cheaper in 2005 $’s)

**Inv. Cost ($/Wac)**

**$35/yr**

**$500/yr**

**4 kW**

** ****4.7 kW**

** ****5.9 kW**

- 50.5%

**Component Costs @**

**2007-2011 MYPP**

**$5.51/Wp**

## Inverter efficiency (dc to ac) improvements have small effect on LCOE
Not much room for improvement 
Array Utilization also Important
Assumes (nearly) perfect:
Maximum power point tracking
Wakeup and shutdown
No power fold-back due to heat 
System design can interfere with max. power point tracking
Shading
Different string orientations

- Not much room for improvement
- Array Utilization also Important
- Assumes (nearly) perfect:
- Maximum power point tracking
- Wakeup and shutdown
- No power fold-back due to heat
- System design can interfere with max. power point tracking
- Shading
- Different string orientations

**Inverter Efficiency**

## Primary system-level trade-off is first-cost vs. reliability

**Parametric Analysis**

- Contribution of 5 kW Inverter to LCOE

## Parametric Analysis

**Parametric Analysis**

**Recall – cost of repair/replacement including labor is original cost.****No other service cost is in this analysis.**

## PV Performance Models in SAM

- Modules
- Single-point efficiency with single temperature coefficient module model
- Sandia PV Array Performance Model
- CEC/Wisc 5-parameter model
- Inverters
- Single-point efficiency inverter model
- Sandia Inverter Performance Model

**Performance Models**

## Won’t uncertainty in solar resource dominate model errors?

- Yes – actual system output is dominated by weather
- But, improved accuracy enables technology choices: A vs. B.  5% better performance is significant.
- Improved accuracy enables evaluation of impact of design changes, e.g. anti-reflective glass on annual performance
- Some module tests at Sandia are industry-funded to keep results of prototype testing proprietary
- Accurate models useful for performance monitoring to detecting problems

**Who Cares?**

## CEC 5-parameter model
More readily available coefficients
short circuit current
open circuit voltage
current and voltage at maximum power point
temperature coefficient of the open circuit voltage
temperature coefficient of the short circuit current

- More readily available coefficients
- short circuit current
- open circuit voltage
- current and voltage at maximum power point
- temperature coefficient of the open circuit voltage
- temperature coefficient of the short circuit current

**Sandia Array Performance Model**
- ~40 coefficients measured in 1⁄2 day test on two-axis tracker
- Coefficients for similar modules can be estimated
- Model uses beam and diffuse data
- Coefficients include:
- Isc, Voc, Imp, Vmp with 4 temp coeff.
- Polynomial representation of air mass
- Angle of incidence modifier
- Thermal model for cell and module operating temperatures vs wind speed and ambient temperature
- Demonstrated for moderate concentration
- Believed applicable to high concentration and multijunction cells
- Downside – database is not current

**Module Model Comparison**

## Slide 13

## Slide 14

## Slide 15

## CEC Inverter Test Data

**5-7 tests are done on a single inverter at each power level and voltage.**
**Coefficients are derived from this or similar data**

**W**

## CEC Inverter Test Summary

## Model vs. Weighted

**Model vs. Weighted**

## System derate factors present major uncertainty
Module model eliminates PV module nameplate rating
Inverter model addresses inverter efficiency
System degradation is entered as a rate
Remainder of values are from Bill Marion’s PVWATTs site.

- System derate factors present major uncertainty
- Module model eliminates PV module nameplate rating
- Inverter model addresses inverter efficiency
- System degradation is entered as a rate
- Remainder of values are from Bill Marion’s PVWATTs site.

## Validation of system performance against measured weather and system data, including for concentrators
Navigant Consulting Inc developing SAM-interactive, spreadsheet-based, system cost model
NCI also developing manufacturing cost model to support module cost inputs
Support SAI partnership use of SAM

- Navigant Consulting Inc developing SAM-interactive, spreadsheet-based, system cost model
- NCI also developing manufacturing cost model to support module cost inputs
- Support SAI partnership use of SAM

**Near-term Efforts**