Imagine a light bulb seven stories tall. Now picture it on its side, 40 feet under water, with a giant three-bladed propeller rotating around the neck. Add a turbine generator inside the bulb and connect it to the propeller (runner blades) and you've got a mind photo of one of the world's largest "bulb turbine" generators.
Two such generators comprise the 40-megawatt hydroelectric power plant located adjacent to the Hannibal Locks and Dam on the Ohio River in New Martinsville, West Virginia.
The New Martinsville/Hannibal Hydroelectric Project is a "run-of-river" powerhouse owned by the City of New Martinsville to be operated to produce the maximum energy output that is compatible with the U.S. Army Corps of Engineers operation of the Hannibal Locks and Dam. Normally the plant will be operated so as to maintain a constant water level of the upstream pool.
This remarkable horizontal turbine technology is harnessing the once-wasted water power that that used to flow over the dam built by the government in the early 70's to promote barge traffic. From a mere 21 foot drop in the river this hydroelectric facility generates enough power for seven cities the size of New Martinsville, population 7,000.
Generating power from water depends not only how far the water falls, but also on how much water there is. "Low-head" plants compensate for lack of height by moving more water - in the case of New Martinsville, about 27,000 cubic feet per second. That's enough to fill a football field about 10 feet deep in about 17 seconds.
Water flows through a short intake canal upstream of the Locks and Dam, around the bulb turbine through 16 wicket gate vanes, which regulates the flow, and out a short, discharge canal into the river downstream of the dam. At the beginning of the intake there are trash-racks installed to prevent damaging debris from entering. Just downstream of the trash-tracks are slots where stop-logs can be inserted to stop the water flow through the plant and with a downstream gate on the lower end of the plant to prevent water from entering the draft tube or passageway of the plant so it can be dewatered and inspected.
The wicket gates or vanes are opened and closed hydraulically to regulate the water flow. Each unit has 16 wicket gates built into the structure of each bulb turbine.
Like the shutter iris of a camera, the wicket gates adjust the water's flow past the runner blades, compensating for changes in the river's natural current. The runner blades are also regulated to get the maximum amount of energy out of the water by adjusting the blade pitch.
The regulating of the wicket gates and runner blades is controlled by a governor system, whereby oil is pressurized to 735 psi to operate the hydraulic components.
The generator voltage of 6900 volts (6.9 KV) is fed to a main transformer which steps it up to 138,000 volts (138KV) in the switchyard on top of the powerhouse, which is connected to the Allegheny Power System substation. A 12,470 volt (12.47KV) overhead distribution line by the Allegheny Power Company system is provided to supply stand-by station service power.
At the top deck of the powerhouse is a gantry crane with a 155 ton capacity of the main hoist and a 2 X 15 ton capacity of the auxiliary hoist. The main hoist is used for handling turbine-generator components and the auxiliary hoists are used for handling stop-logs and removing trash from the intake.
The powerhouse is provided with a fenced parking area and outside the fence are a public recreation and fishing grounds available to the public with restrooms, a fish cleaning station, a picnic shelter and tables, barbecue grills, a handicapped fishing pier with an access ramp, parking areas and access roads. Furthermore, the powerhouse is connected to the City of New Martinsville portable water and sewage systems.