Fifteen months ago I got a tour of the power plant in my home town of Graettinger, Iowa. This was posted on the Stranded Wind Initiative web site but somehow never made the jump to DailyKos.
I've been thinking along these lines again as we're working on a project in southern California that has a generating component. I ran across this tonight while looking up other stuff and figured folks here might want to have a look around a small town power plant.
I recently got a chance to tour the Graettinger Municipal Light Plant, photographic the facility, and grilling the manager, Scott Tonderum, on the details of the operation. I was quite surprised to learn that our electricity is already 62% renewable here, and that one of our backup systems is a world war II ship's engine converted for generating duties.
First, some words about customers. The city has a population of just under a thousand. There is a typical Iowa brick K-12 school that is now a shared facility with Terril, 12 miles to the northwest. There are two large manufacturing operations, Energy Panel Systems which employs about a hundred, and Shaver Manufacturing, which is about half that size. The main street, pictured below looking east, has a dozen businesses, and there are a handful of light manufacturing type businesses found just north of the main street area. The city is served by Union Pacific rail and there is a large grain elevator and associated outbuildings
Power for the town arrives at a 69,000 volt substation a mile east of the city and lands in another 69,000 volt substation directly adjacent to the light plant.
This 69,000 volt system bears around 300 amps at peak times, providing the 2.2 megawatts of power needed to cool the city at the height of summer.
I was surprised to learn that fully 62% of our existing electricity is generated from renewable sources, with 56% coming from hydroelectric and 6% from wind. The mix for 2008 will advance slightly to 65% renewable, 13% from wind of that coming from wind, and a slight decrease in hydroelectric to 52% making up the balance. The city owns a one megawatt share in a coal fired plant on the west side of the state.
The city's original generating plant is long gone, but one of the generators from the first major upgrade remains in service. This is a retired marine diesel from a ship that served during world war II. The large, round object in the photo just to the left of Mr. Tonderum is the actual generator itself.
A second upgrade was performed in the later 1950s, when this 500kw 1957 Superior diesel generator was installed. Those who recall the operation from that time are long retired, but we suspect a pair of these provided power continuously with the larger unit being put into service when the load spiked.
The plant's two older diesels are cooled by an oil to water heat exchange system. The brown lines are the oil feeds to the machines above them on the ground floor and the blue lines run to an outdoor heat exchanger.
The heat exchanger stands behind the building next to the 14,000 gallon diesel tank. If all three generators are running flat out consumption is 200 gallons per hour. The system is sized to stand a three day main grid outage over the Fourth of July holiday. This only happens when the need is dire; diesel generation costs at least triple what coal fired power does.
Generator technology has evolved over the years and the new Cummins Onan 2.0 megawatt unit can support the town on its own in all but the hottest weather. No water to oil cooler lines for this guy - the radiator for this unit is mounted on the roof.
These units have two uses, backup power in the event of outages, and they also support the grid in times of peak usage. They're called into service during the "dog days", usually late July or early August, and they receive tests just a little more often than a quarterly basis through the rest of the year.
Hydroelectric supplies much of the base load for the area and a single large wind turbine could nearly free the city of fossil fuel inputs for electric generation. I'm going to look into what would be required to get this done.