The Orca power plant is located on the north end of Cordova across the street from the Alaska Marine Highway System’s ferry dock. It was built in 1984 and has been a primary source of power for Cordova.
The plant contains five diesel engine driven generators, three larger “main” units and two smaller “peaking” units. The total load capacity of this plant is a little over 10.8 megawatts (MW).
The largest of the units, installed in 2009 is an Electro-Motive Division (GM) model 710-G4CT2. It is a 5000 horsepower, 900 RPM, turbocharged 20 cylinder four stroke V-configuration engine. It turns a 900 RPM 3 phase 12,470 volt generator with a rated load capacity of 3.7 MW. These modern high power engines are commonly seen in today’s railroad locomotives. The second large unit is an Electro-Motive Division (GM) model 645-E4, which is a 3600 horsepower 900 rotations per minute (RPM), turbocharged 20 cylinder four stroke V-configuration engine, turning a 900 RPM 3 phase 2400/4160 volt generator with a rated load capacity of 2.5 MW. These engines are also used in railroad locomotive applications. The third of the large units is a Fairbanks Morse model 38 TD 8 1/8, which is an opposed piston 3,360 horsepower 720 blown and turbocharged inline 12 cylinder engine turning a Louis Allis 720 RPM 3 phase 12,470 volt generator with a rated load capacity of 2.4 MW.
These engines are of an interesting design in that there are no cylinder heads, but instead have an upper and lower crankshaft and two pistons per cylinder that compress the air/fuel mixture in the middle of the cylinder from above and below. They were originally designed for use as submarine propulsion units because of their ability to produce large amounts of horsepower in a relatively limited space.
The two smaller units are Caterpillar model 3516’s , which are 1200 RPM turbocharged 16 cylinder V-configuration engines, turning Kato Engineering 1200 RPM 3 phase 480 volt generators with a rated load capacity of 1.1 MW each.
A UTC/Pratt-Whitney Power Systems 280 PureCycle Organic Rankine Cycle (ORC) heat recovery unit was first brought online on June 1, 2012. This unit, in simple terms, is a refrigeration system operating backwards, heat injection rather than heat removal. It is connected to the EMD 710 generating unit’s glycol cooling circuit and increases the fuel efficiency of the unit by 4.5% (ORC – 159 net kW/EMD 710 – 3513 kW). The Organic Rankine Cycle is integrated with our SCADA system and monitored by the power production staff.
The Orca power plant is also the central control point of Cordova Electric Cooperative’s (CEC) entire generation and distribution system. All diesel and hydro operations at all three power plants are monitored, controlled and run from one computer station through a state of the art Supervisory Control And Data Acquisition (SCADA) automation system that also monitors and controls CEC’s substation located approximately two miles east of the Orca plant. With this SCADA system operators can manually control all generation units, distribution feeders, and dam operations as well as monitor the status of all critical dam, unit, and feeder details from one central location.
With a sophisticated feature called “Demand Control” engaged, the SCADA system is, in effect, in an “auto pilot” state that will make all decisions and necessary adjustments to the electric utility system to maintain a steady, clean and reliable supply of power for the City of Cordova and the surrounding area.
The main focus of Demand Control is to provide the most efficient use of the available hydroelectric power, keeping the use of diesel units to an absolute minimum.