# Presentation: 916324

## Overcoming Transmission Constraints: Energy Storage and Wyoming Wind Power

- EESAT 2005 San Francisco, October 18, 2005Mindi Farber-DeAnda, SAICVictor Gorokhov, SAICMark Kuntz, VRBBrad Williams, PacifiCorp

## ACKNOWLEDGMENTS

- Funded by the Energy Storage Systems Program of the U.S. Department Of Energy  (DOE/ESS) through Sandia National Laboratories (SNL).

## Project Status

- Since ESA in May, we experienced further contractual issues that delayed our progress
- The analysis is almost complete; report drafting has begun
- Examining rebates and other incentives
- Scrubbed and enhanced the model with:
- Alternate time-of-use schedules and tariffs
- Multiple charge/discharge cycles/day
- Salvage and rebate values
- Scenario comparison

## Wyoming Wind Speed at 50 Meters

## Foote Creek Rim I Layout

- Source:  SeaWest, December 2004.

## Wind Generation from Foote Creek Rim I

## Wind Speed and Turbine Output in SummerJuly 25 – 31, 2003

- Source:  Calculated from SeaWest Data on Wind Speeds at Turbines and Meteorological Stations, December 2004.

## Wind Speed and Turbine Output in WinterDecember 14 - 20, 2003

- Source:  Calculated from SeaWest Data on Wind Speeds at Turbines and Meteorological Stations, December 2004.

## TOT 4A & 4B Transmission Flows in Wyoming 

- Source:  PacifiCorp, 1990 Update of the TOT 4B vs 4A Nomograms, March 1991.

- TOT 4A flows Southwest

- TOT 4B flows Northeast

## PacifiCorp TOT4 System Load in SummerJuly 25, 2003 – July 31, 2003

- Source:  Calculated from PacifiCorp’s End-of-Hour TOT 4A and 4B Load Data in Wyoming.

## PacifiCorp TOT4 System Load in WinterDecember 14, 2003 – December 20, 2003

- Source:  Calculated from PacifiCorp’s End-of-Hour TOT 4A and 4B Load Data in Wyoming.

## Wyoming TOT4 System Load Duration

- Source:  Calculated from PacifiCorp’s End-of-Hour TOT 4A and 4B Load Data in Wyoming.

- 	In 2003, there were 187 hours spread over 47 days in which load duration exceeded 90%.

## Conceptual Plan for Multi-MWh VRB Plant

## Modeling Efforts

- Built and tested Excel model to calculate battery operation based on actual 2003 transmission congestion, wind turbine output, and potential output without congestion
- Performed sensitivity runs against a No Battery case, altering
- Tariff time-of-use factors
- Charge/discharge profile (start/finish times, once & twice a day)
- Capacity (MW capacity, 8 hour discharge)
- Round-trip efficiency
- Installed and O&M costs (current and future)
- Life expectancy
- Interest rates
- Salvage values
- Rebates

## Tariff Assumptions

## Model Sensitivity Runs – Time of Day Profiles

| Variables | Once a Day  | Twice a Day |
| --- | --- | --- |
| Summer Charge | 0:00 - 10:00 | 24:00 - 9:00; 19:00 – 21:00 |
| Summer Discharge | 12:00 - 20:00 | 11:00 – 19:00; 21:00 – 24:00 |
| Winter Charge | 0:00 - 10:00 | 0:00 - 10:00; 15:00 – 20:00 |
| Winter Discharge | 13:00 - 21:00 | 10:00 - 15:00; 20:00 – 24:00 |
|  |  |  |
| Discharged MWh | 4,020 | 6,083 |

- Aligning the battery charge/discharge profile with tariff time-of-use factors increased the MWh discharged and the revenue from capacity charges.
- Restrictive tariff with low winter rates and efficiency losses worked against incremental revenue.

##     Comparison of optimized once a day and twice a day operation yielded 50% more MWh discharged but 2% less incremental revenue

**Model Sensitivity Runs – Time of Day Results**

## Model Sensitivity Runs - Capacity

- Altering battery capacity from 8 MWh to 48 MWh while holding a once a day 10-hour charge and 8-hour discharge.
- 24 MWh is the optimal size.  Energy discharged and revenue per MWh discharged are optimized: 4,020 MWh at $64/MWh.

## Model Sensitivity Runs – Salvage Values

- VRB battery has two electrolyte storage tanks of active vanadium-sulfuric acid solutions
- Vanadium can be recovered from the electrolyte at the end of battery life
- VRB estimates this value at $76/kWh of energy storage capacity
- Compared a range of salvage values to examine the contribution to cost reduction

| Salvage Value | Reduction |
| --- | --- |
| $50/kWh | 13% |
| $76/kWh | 19% |
| $100/kWh | 25% |

## CEC Pilot Performance-Based Incentive Program

- 50¢/kWh incentive for eligible renewable energy systems
- Photovoltaic systems only at present
- Equipment to store the electricity is not eligible (batteries, charge controllers, etc.)
- Incentives are paid for the first three years only
- Maximum available funding;
- $  400,000 per project
- $1,000,000 for corporate or government parent
- Apply to CEC with preliminary reservation; participate in CEC monitoring; submit quarterly invoices to CEC; receive payments within two months
*What if energy storage qualified for 1/10 of this rebate?*

## Model Sensitivity Runs – Rebate Values

| Rebate Value | Reduction |
| --- | --- |
| 0.5¢/kWh | 1.2% |
| 1¢/kWh | 2.4% |
| 5¢/kWh | 11.9% |

- Assume that CEC extends its pilot performance-based incentive program to energy storage
- Energy storage equipment could obtain a “reasonable” portion of the 50¢/kWh renewable energy rebate, e.g.,
-  1%  or 0.5¢/kWh
-  5%  or 1¢/kWh
-  10%  or 5¢/kWh
- The resulting cost reduction during the initial years would be significant:

**Model Sensitivity Runs – Rebate Values**

## Wrapping Up

- Complete analysis in a Final Report by year end 2005
- Perform a team review in January 2006
- Document the model, its ability to handle alternate time-of-use schedules and tariffs.
- The model is robust; it can provide reliable analysis of  wind speeds and turbine outputs in other transmission-constrained markets.
- Thank you to DOE Energy Storage Program, Sandia National Laboratories, Wyoming Business Council, PacifiCorp, and VRB