Unintended Consequences: The Impacts of Wind Energy on Rural Alaska Diesel Power Systems

David Lockard and Alan Fetters, Alaska Energy Authority

Presentation Goals

• Describe impacts of wind turbines on rural Alaska diesel power system operation (a moving target)

• Assess significance of those impacts• Discuss opportunities to optimize operation of

wind and diesel components of wind-diesel power systems

Wind Impacts on Power SystemsTechnology Estimated Reduction

in Fuel SavingsComments

Heat Recovery 10-25% May be jacket-water, wet manifold, or stack HR

Diesel Efficiency ?-30% See genset manufacturer’s efficiency curve. Also depends on penetration level.

Wind Turbine Station Service

1-8% Resistance heaters (controls, powerhouses, transmissions), meters, controls, startup power, etc.

Power Factor Correction

1-3% Sychronous converters, capacitors, “big iron”, static VAR compensators, etc. (Unalakleet PF < 0.4 at times)

Line and transformer losses

2-5% Typical losses based on design criteria

Wind energy used for thermal purposes

50% Oil heating efficiency is approximately twice diesel generation efficiency

Cat 3456 w/ Custom Wet Manifold

Before After

Chitina Stack Heat Recovery

Kotzebue Wind Impact on HR

• Kotzebue Heat Recovery:– Water heating– District heating– Summer ice making with absorption refrigeration– ORC/stack heat recovery

KEA goal of using 85% of energy in fuel.

10 in operation6 in construction6 in design16 in feasibility

Wind-powered Electric Boilers

Nikolski Wind Example

• Wind Turbine: One 65 kW Vestas• Gensets: – One- 37 kW, mechanically fuel injected– Two- 71 kW, mechanically fuel injected

• Avg load = 30 kW• School closed• Electric heaters at school, lodge and powerhouse• Recent blackouts due to insufficient thermal loads

to absorb peak wind output (80 kW?)

Nikolski Diesel Dispatch ScenariosElectric Load Scenario Diesel Dispatch Wind Dispatch

Low load 20 kW – 30 kW Maximize diesel use to reduce risk of wet stacking 37kWgenset and improve diesel efficiency

Thermal purposes

30 kW – peak load (40 kW) Maximize diesel use to reduce risk of wet stacking 71kW genset and improve diesel efficiency

Thermal purposes

John Deere Engine RecommendationsAugust 2004

Generator efficiency is also affected by power factor. The inductive current in the generator increases the resistive losses in the generator and lowers efficiency. The highest generator efficiency is at unity PF. A generator mayrun at 92% efficiency at 1.0 PF and only 90% efficiency at 0.8 PF.

Tier 4 Concern

• Tier 4 diesel gensets will have exhaust emission equipment that requires minimum stack temperatures for the oxidation catalyst to work. At low genset loads, those temperature requirements will be met by burning additional fuel in the stack to meet emission requirements.

• AEA has requested an EPA waiver for some of the Tier 4 genset requirements

Conclusions• Wind turbines have multiple impacts on the

performance and economics of diesel power systems.• Wind-diesel economic analysis should include the

impacts on heat recovery, diesel efficiency, power factor and quality, station power use, and line/transformer losses.

• Wind energy used for heating purposes saves about 50% less fuel than when used for electrical purposes.

• Diesel power system technology is changing rapidly, which makes it even more challenging to integrate wind power.