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Feel the Power
APC offers an extensive line of UPS units including the Smart-UPS RT. This series of on-line UPSs comes in power levels from 1 to 10kVA. The 10kVA unit uses 10RU of rack space, weighs 440 lbs, and has a half-load run time of 13 minutes. Serial and Ethernet communications are standard. (Just think about all the e-mails you're going to get when the power goes out!)
One manufacturer you may not have heard of is Falcon Electric. I'd like to point out its SG series of online UPS units, in the power range of 800VA to 6kVA. Falcon also points to another advantage of online UPS technology — the elimination of UPS problems associated with drifting frequencies, as well as voltage, in the output of a generator.
In the design of a new facility, if you decide to provide UPS backup for the entire technical core (or maybe even more) you could easily go with a large UPS that makes use of batteries for energy storage, such as the Tripp Lite Smart Online SU80K modular UPS system that provides 120/208Vac three-phase outputs. It's an online system with all the advantages I've previously described — but it's made up of four separate 20kVA UPSs, which according to Tripp Lite gives the end-user the capability of working on the system even while the load is energized. I should also mention it includes a manual bypass breaker and an automatic bypass function.
There is yet another option for the on-line UPS backup for the technical core — one that uses energy stored in a rotating flywheel as opposed to backup batteries. Active Power offers Clean Source in a wide power range, from 130kVA up to 3600kVA. It's highly efficient — up to 98 percent in fact — and though you won't have to maintain or dispose of large batteries you will need to change bearings for the flywheel upon occasion. I must also mention the application (aside from full-time line power conditioning) is to bridge the gap between the time the utility power goes down and your generator starts. This type of UPS isn't meant to supply an entire facility for a substantial amount of time.
Perhaps you are not in the market for a new generator or UPS, but instead are interested in alternative power sources for your station's studio or transmitter facilities. There are at least two different technologies readily available and warrant your consideration.
It's interesting to note that most energy sources on the earth are in reality derived directly from the sun — whether it is electricity from photovoltaic cells, wind, fossil-fuel or even hydropower. The ideas aren't new but in many cases the specific technology is. When you stand in the sunlight on a hot summer day, it's a little hard to believe that a burning ball of gas 93,000,000 miles away still feels that hot! Indeed, the amount of energy from the sun intercepted by just the Earth's surface is about 7,000 times more than the total global energy consumption (for 2005 anyway).
Going green is, at the very least, a good marketing avenue for radio. Using alternative energy sources, for even a part of a station's energy needs, is relatively easy to do. Let's take a look at a prime example: KGO radio in San Francisco.
The solar power project for KGO is being conducted at the KGO transmitter site near the Dumbarton Bridge in Newark, CA. A major highway is immediately adjacent to the site (in fact the KGO transmitter is commonly known as “the Towers” in traffic reports) and so it provides a lot of exposure to thousands of commuter eyes every weekday. Its first solar power system is made up of photovoltaic cells (PV) manufactured by General Electric and mounted in flat arrays on the roof of the transmitter building and near it on the ground. Its second solar power system is based on the use of concentrator photovoltaics (CPV) and is provided by Solfocus of Mountain View, CA. The CPV system is really quite simple and elegant. Small mirror arrays (main and secondary reflectors — simply a small version of a satellite dish) collect sunlight with a gain of about 500 times. The collected sunlight is then shined on a small PV cell, with efficiency nearly three times that of a standard PV. The CPV cells are mounted in flat-panel arrays that track the sun along azimuth and elevation.
In the case of KGO, this CPV solar system operates in real time, without battery storage. Energy collected from the sun is converted to 60Hz ac, and added to the feed from the local power company, Pacific Gas and Electric. KGO Director of Engineering Joe Talbot expects the peak output from the CPV system to account for about 10 percent of the total needs for the KGO transmitter facility (it is a 50kW site). Talbot also indicates that about half the capital expense of $200,000 will be covered by incentives provided by the state of California in conjunction with PG&E.
The answer is in the wind
If you want to go beyond what KGO is doing and generate power by way of the sun and wind, you can meet (at least part of) your site's needs through the entire day. In theory you could generate power from both the sun and the wind during the day, store some of it in batteries, and perhaps rely upon the wind generator by itself at night. Let's take a look at one station that is generating a substantial part of its needs by way of the wind.
KPAN radio, located in Hereford, TX (in the heart of the Texas panhandle), uses a small wind turbine (the Skystream 3.7) from Southwest Wind Power of Flagstaff, AZ. This unit is rated at 2kW of constant output, with a peak capability of 3.4kW. Like the KGO system, the output of the Skystream 3.7 is in the form of ac power that interconnects with the user's utility feed (if it turns out that the Skystream generates more power than is being used, the utility meter goes backward). Chip Formby of KPAN tells me the entire kit costs about $5,600 — and can even be sourced by mail order. (Installation in the case of KPAN was around $10,000.) Sounds easy enough — but you will need about a half acre of land, a 45' pole, and an average wind speed of at least 10mph. Although the system is brand new (about two weeks old as this is composed) Chip expects the system to provide about 25 percent of the energy needs of the studio facility during the windiest months. He also tells me that the Skystream will power the studio facility completely while the studio is unattended.
As an alternative consideration, you may also want to look at Endurance Wind Power. Its small wind turbines make use of an induction motor, with an output that is 60Hz, and connects directly to the power grid without making use of an intermediate dc to ac inverter.
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