Wind and Solar Integration in Colorado: Challenges and

Solutions

Wind and Solar Integration in Colorado: Challenges and

Solutions

Colorado Rural Energy Agency

Energy Innovations Summit

Energy Storage for Intermittent Resources: Is the “Silver Bullet” on the Horizon?

Keith Parks, Senior Analyst

October 14, 2011

Agenda

Colorado Wind & Solar Energy Today

Renewable Energy Integration Challenges

Solar

Wind

Is Storage the Solution?

Natural Gas Price

Carbon Policy

Integration Costs

Colorado Wind and Solar Today

PSCo – 1735MW

SPS – 736MW

NSP-MN – 1591MW

Xcel Energy – 4062MW

Wind = 1735MW

1159 turbines

Solar = 131MW*

8652 installations

*includes 27.4MW Utility Scale Solar PV at two installations

2x30MW utility scale solar facilities to be operational by end of 2011

Additional 400MW of wind energy installed by end of 2012

Solar Energy Integration

PV is the dominant solar technology on the system and will be for the near-term

PV is dramatically affected by cloud cover – variability can occur in seconds.

Peak production from fixed-axis installations match poorly with system peak needs

SunE Alamosa – Single Axis Tracking (7.1AC)

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Wind Energy Integration

Wind variability is over a longer time frame – tens of minutes to hours.

Production peaks at all times of the day – not just at night.

Wind has a low capacity value over summer peak periods

PSCo Wind Output (MWh)

Wind Energy Integration

In real-time, more wind means fewer dispatchable resources are on-line to manage the variability. Additionally, wind competes with traditional baseload facilities for system bandwidth. Occasional wind energy curtailment is required to maintain system reliability.

PSCO Wind as a Percentage of Obligation Load (Jan 2009 thru Oct 2011)

35.4%

55.6%

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Is Storage the Solution?Is Storage the Solution?

Charging Fuel (% of Time) vs. CO2 CostSystem with Coal Base Load

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Coal

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Relative Value of StoragePSCo System (Coal Baseload)

Increasing CO2 Price

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Wind Integration Costs: Uncertainty and Variability

Public Service Company of Colorado 2 GW and 3 GW Wind Integration Cost Study. August 19, 2011. Pg 24.

Integration Cost for Storage Sensitivities

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UpgradeCabinCreek

NewStorage

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Energy Storage Reduces Wind Integration Costs

Upgrade Cabin Creek

Increase upper pond

Higher nameplate capacity

Increase turnaround efficiency

Additional Storage Resource

2nd Cabin Creek

Conclusion

Currently, PSCo system uses Cabin Creek and gas storage as buffers

System doesn’t have sufficient wind curtailment exposure that can be cured by energy storage in the near-term

Storage capital costs above arbitrage value

BUT…as more renewable energy is integrated into the system, energy storage provides more value. We will continue to evaluate role and economics of storage.

Near-Term Mitigation Strategy

Lower the FloorLower plant minimum capacityDecommit - Reevaluate “must run” statusDecommission baseload (CACJA)

Upgrade Existing Storage Facilities (ie Cabin Creek)Increase upper pond capacityMove black start capability to diesel generators

Enable Wind to Participate in System BalancingImplement set point control at wind plants (“optimal” curtailment)Better forecasts = Better planning

Long-Term Solutions…Add New Storage FacilitiesDispatchable Loads

A Big Picture View of Wind Curtailment

A Big Picture View of Wind Curtailment

System Perspective (2013)

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System Minimum = Must Take Contracts + Coal Minimum Capacity + Must-Run Gas Minimum Capacity - Pumping Capacity

Dispatchable Coal

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System Minimum = Must Take Contracts + Coal Minimum Capacity + Must-Run Gas Minimum Capacity - Pumping Capacity

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Visualization of How Off-Peak Load Helps Mitigate Wind

Curtailment

Visualization of How Off-Peak Load Helps Mitigate Wind

Curtailment

System Bottoming Effects (No Storage)System with Coal Baseload

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Off Peak Charging Increases Load...

And Reduces Curtailed Wind

Xcel Energy Wind and Solar Future

Xcel Energy Wind and Solar Future

Xcel Energy Wind Farms Today

PSCo – 1735MW

SPS – 736MW

NSP-MN – 1591MW

Xcel Energy – 4062MW

Xcel Energy manages output from 4.1GW (2972 turbines) of wind energy across the three operating companies (NSP-MN, PSCo, SPS) and seven states (CO, TX, NM, WY, MN, SD, ND)

Forecast by end of 2011 Q3

Xcel Energy Wind Generation Growth

Xcel Energy has been the nation’s largest wind power provider for seven consecutive years.*

Current resource plans have 5GW installed by 2015.

PSCo will be at nearly 2GW by the end of 2012.

Installed Wind Capacity (MW)

*American Wind Energy Association (AWEA); US Wind Industry Annual Market Report 2010

5000 MW

3432 MW

4062 MW

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Colorado Solar Generation Growth

HB10-1001 creates minimum retail distributed generation* requirement

Requirement is largely met through Solar Rewards program (current 99.4MW)

Solar Gardens legislation (HB10-1342) allows for community solar facilities (<2MW) to qualify as well.

Distributed Solar PV Capacity

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*Retail Distributed Generation - Must be renewable energy (wind, solar, bilmass, hydroelectric) installed on the distribution system. There are further requirments

regarding the how much can be residential vs commercial/industrial, amount installed by year, etc

Why Forecasting?Why Forecasting?

Obligations and Resources Today

Net Load – Load less variable output generation.

Traditional Utility Paradigm

Mid-Merit

Baseload

Peakers Renewables

PSCo - April 26, 2010 to May 2, 2010

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Loads and Resources Today

Loads and Resources are forecast every working day for operational planning purposes. This is called day-ahead commitment.

PSCo - April 26, 2010 to May 2, 2010 Actual – Thick Line; Forecast – Thin Line

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Forecasts of loads, variable energy generation, and unit availability are inputs to the operational planning process. Typically 18 to 42 hours ahead, but as much as five days.

Wind

Loads

Loads and Resources Today

Uncertainty is driven by the wind portfolio.

PSCo - April 26, 2010 to May 2, 2010

Mean Absolute Error

Load = 86MW

Wind = 245MW

Net Load = 240MW

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Renewable Energy Integration Solutions

Renewable Energy Integration Solutions

Loads and Resources – A New Paradigm

High Penetration Portfolio

Balance Portfolio

Variable

Traditional Utility Paradigm (w/ some RE)

Mid-Merit

Baseload

Peakers Renewables

RE Forecasts are nice but don’t affect operationsRE is must-takeFossil-based facilities operate to a define dutyNew facilities chosen for least-cost energyStorage facilities dispatched to peak shave

RE Forecasts drive operational decisionsRE is dispatchableFossil-based facilities are modified for flexible dutyNew facilities chosen for least-cost energy w/ flexible optionalityStorage facilities dispatched for RE/load shifting