Maximizing Hydropower Use in the Cordova Electric Cooperative Grid
This ongoing 2014 project is exploring the potential for optimizing the generation mix in Cordova, Alaska. It will assess the technical and economic feasibility of adding an energy storage solution and demand response to reduce the use of diesel generation.
Cordova is a small city located near the mouth of the Copper River on the southeast edge of the Prince William Sound. There is no road system connecting it to any other Alaska city, and the community relies on power generated from two run-of-the-river hydropower stations and several diesel generators. The Cordova Electric Cooperative (CEC) provides electricity to the City of Cordova and to several fish processing plants.
Hydropower provides 24% of the total statewide electrical power in Alaska and more than 60% in Cordova. Hydropower plants have proved to be long-term, reliable and relatively inexpensive. With increased interest in replacing fossil fuel-powered generation with renewable energy resources, the statewide inventory of installed hydropower capacity will continue to expand.
Historically, Cordova's hydropower has been sufficient to meet nearly all demand during the summer months. However, recent increases in energy demand from the fish processing industry has exceeded the capacity of the hydropower plants, forcing CEC to supplement with diesel generation.
Currently, when hydropower is the sole generation source, one 3 MW hydropower turbine is used for frequency regulation, which results in a reduction of 500 kW of available capacity. While hydropower capacity is not sufficient to meet daytime demand, the hydropower plants do not operate at full capacity during off-peak hours. Since these hydropower systems do not include dams that provide water storage, the water that is normally diverted for power generation is simply spilled down the creeks. The result is significant loss of potential power production and, thus, power sales from a very cheap generation resource. The need for alternative frequency regulation services, along with the desire to maximize the use of hydropower, is the impetus for this study, which assesses the technical and economic feasibility of achieving maximal hydropower use via energy storage and demand response technologies.
Initial assessments show that in 2012/2013, over 2,000 MWh of potential hydropower production were not realized due to demand being below hydropower capacity. While it is not certain that the full amount of lost production is recoverable, this gives a tangible initial economic case to further explore possible solutions.
Research partners are analyzing data provided by CEC to better understand the economic potential of an energy storage and demand response solution to utilize this spilled energy. An energy balance model (EBM) has been employed to model the generation and demand mix and to develop a range of scenarios that optimally incorporate energy storage and demand response solutions. Maximum value of an energy storage and demand response system can be achieved only if it precludes diesel generation during peak demand periods, so load growth scenarios will be added to the model to understand the future value of a solution.
The goal of the EBM is to understand the value of making the additional 500 kW of hydropower generation available to meet energy demand and creating an energy storage solution to shift generation from peak to off-peak periods and assessing how off-peak demand can be increased while reducing peak demand through demand response solutions. Based on model results, possible energy storage and demand response solutions for both applications will be identified and incorporated into the EBM, facilitating recommendations for optimal sizing and scheduling.
Furthermore, ACEP researchers have studied the potential and options for installing controlled electro-thermal loads at the Orca Diesel Power Plant and the Bob Korn Memorial swimming pool in Cordova. The Orca plant currently utilizes diesel-fueled boilers to keep engines in hot standby when the grid is running on 100% hydropower, which results in fuel costs for heat of over $80,000/year (2014 numbers). Similarly, the swimming pool requires over 16,000 gal/year of diesel fuel for heat. Utility-dispatched electric heaters that would supplement heating loops when excess hydropower is available, may significantly reduce diesel fuel use. Conceptual designs developed by ACEP incorporating efficiency upgrades and thermal storage systems may reduce fuel use by over 20,000 gal/year for both systems.
Photo Left: Schrader falls basin. Courtesy of M. Mueller-Stoffels, ACEP/UAF.
Photo Center: 3 MW Hydropower turbine at the Power Creek powerhouse. Courtesy of M. Mueller-Stoffels, ACEP/UAF.
Photo Right: Power Creek Hydropower water intake structure. Courtesy of M. Mueller-Stoffels, ACEP/UAF.