Trends in Technology: Alternative Power

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Clearing snow from the PV array in winter; just one more day in the life of a broadcast engineer.

Dual diesel generators. Rarely have I seen a mountain-top or remote transmitter site without a diesel generator as a backup power source. Even if you were to pay your local utility company upfront to run the power lines needed up the road to the transmitter site, it’s very likely that you’ll still want to put a generator in as well. At what point does it make just as much sense to install two generators, and to skip the utility power? To determine that, you must, at the very least, consider the following:

1. Actual capital cost of a second generator
2. Installation expense of a second generator
3. Cost of installing large fuel storage tank(s)
4. Expected lifetime of generator running 50 percent of the time
5. Fuel expense to run one of the two generators continuously
6. Likelihood that fuel deliveries will be difficult in bad weather
7. Generator maintenance

Dc controllers and 120Vac sine wave inverters for KLRD’s hybrid power system

I do know of one circumstance in which a dual generator system was built and put in to full-time use, because although it was anticipated that utility power would eventually be installed, it was delayed, and the station owner didn’t want to wait for it before turning up the site. John Burger was the chief engineer for KTRB during this undertaking. He described for me what happened. “In 2006 KTRB-AM was a C-O-L change from Modesto, CA to San Francisco. In SF it was designed to operate from separate day (non-D, 50kW) and night (directional, 50kW) sites. The daytime site was to be located in Sonoma County. The nighttime site is located in Sunol, California,” John said. “The Sonoma site never came to be. This consumed much time and money. Construction on the nighttime site began July 2006. The site is several miles from public roads and PG&E (the major local utility). PG&E service would have been available if access could have been secured from one of the surrounding ranches, but this was not immediately forthcoming. Therefore the site was designed and built to run on generators.

“The power plant was designed to use alternating sets of day/night generators. We had two 35kW generators for daytime (non-transmitting) operation of the site, and two 260kW generators for nighttime on-air operation. The system was to be controlled by a series of transfer switches that alternated day/night operation as well as alternate day operation. Daytime/nighttime operating hours were to be controlled by a timer. Access to the site was along a road belonging to the San Francisco Water District, which ran along one side of a reservoir that is a large part of San Francisco’s drinking water system. Due to concerns about diesel being spilled into the reservoir we were ‘encouraged’ to install LPG generators. Fuel storage is a 10,000 gallon tank. The Bay Area Air Quality Management District mandated that each large generator be equipped with a catalytic converter the size of a VW Beetle, and costing as much as a Porsche Boxster.

- continued on page 3

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