Many broadcast facility operators are finding that the cost of purchasing and operating air conditioning systems is increasing. The typical air conditioning unit requires ongoing maintenance and eventual replacement on a 5 to 8 year cycle.
There is high interest among broadcasters and RF network operators to reduce their overall transmission facility cost of ownership. In this article, Geoffrey Mendenhall from Harris Broadcast Communications, investigates a new evaluation process and analysis tool to design a transmission facility for lowest TCO.
The Total Cost of Ownership (TCO) includes much more than the initial cost, energy consumption, and maintenance of the transmission equipment. The acquisition, maintenance, operating, and training costs of all the other required systems in the transmission facility must also be considered to arrive at lowest TCO. Besides the reduction in direct operating costs, the benefits of reduced TCO include a reduction of carbon footprint in support of green technology. The comprehensive analysis includes the tradeoffs between air and liquid cooling system impact on the overall facility, floor space requirements, size, and the thermal efficiency of the transmitter building.
WHAT CONTRIBUTES TO TOTAL COST OF OWNERSHIP?
Acquisition cost of transmission equipment
Installation cost of transmission equipment
Operating cost of transmission equipment power consumption
Maintenance cost of transmission equipment
Acquisition cost of facility cooling system (HVAC, etc.)
Installation cost of facility cooling system (HVAC, etc.)
Operating cost of facility cooling system power consumption (HVAC, etc.)
Maintenance cost of facility cooling system (HVAC, etc.)
Periodic replacement cost for facility cooling system (HVAC, etc.)
Acquisition cost of power conditioning or other special equipment
Maintenance cost of power conditioning or other special equipment
Acquisition or recurring lease cost of floor space required
Training costs for all required equipment
As outlined above, the total cost of ownership must take into account far more than the initial purchase cost of the transmission equipment. Many facility design and purchase decisions are still being made on the basis of the transmitter and antenna costs in isolation from the many additional costs associated with the rest of the supporting infrastructure required to make the facility work. To understand the true cost of ownership, all of the above facility cost items must be taken into account.
WHAT IMPACT DOES TRANSMITTER SELECTION MAKE ON TCO?
Physical size and foot print (FT2)
Power density of transmitter (Watts / FT3)
Type of cooling – air or liquid
Operating efficiency (AC to RF) of the transmitter
AC power requirements – (1) phase or (3) phase (polyphase power may be costly to bring to some sites)
AC input voltage and voltage regulation requirements
Maintainability – hot swappable modules, air or liquid filter replacement, all other maintenance tasks
Commonality of transmitter types – spares sharing, common training and operational requirements
N+1 transmitter system architecture can reduce number of backup transmitters required
The choice between air or liquid cooling for the transmission equipment can make a significant difference in the overall cost of ownership. Although the initial purchase cost of a liquid cooled transmitter is typically higher than an equivalent air cooled transmitter, the elimination of most of the costs associated with air conditioning can make the breakeven period short on the cost difference of the transmitter and provide significant long term operational savings.
Many broadcast facility operators are finding that the cost of purchasing and operating air conditioning systems is increasing. The typical air conditioning unit requires ongoing maintenance and eventual replacement on a 5 to 8 year cycle. The combined operating, maintenance, and replacement costs become a significant part of the overall facility operating cost.
Liquid cooled transmitters have significantly lower energy consumption than the combined energy consumption of an air cooled transmitter and the required air conditioning.
TRANSMITTER EFFICIENCY OPTIMIZATION
Several recent technology advancements have significantly improved transmitter operating efficiency. The introduction of 50V LDMOS RF transistors has made a significant improvement in transmitter power amplifier operating efficiency. Figure-1 shows a comparison of three different MOSFET technologies currently used in broadcast transmitters. Figure-2 shows improved efficiency and power gain of the latest generation 50V LDMOS RF transistors.
FET TECHNOLOGY COMPARISON
FIGURE – 1
PERFORMANCE SCALE FROM (1 = POOR) TO (5 = BEST)
50V LDMOS technology offers higher amplifier gains of 19dB in digital DVB-T operation and 21dB in FM operation, thereby reducing the inefficiency of the drive stages. Typical DC to RF efficiency of over 28% in DVB-T operation and 84% in FM operation can be achieved.
50V LDMOS EFFICIENCY AND GAIN
The latest generation switching power supplies have significantly improved the conversion efficiency from the AC mains input power to the DC power required by the LDMOS RF transistors. Typical power supply conversion efficiencies have improved from 85% to 95%. Switching power supplies have also eliminated the need for outboard voltage regulators with their associated operating, cooling, and maintenance costs. Switching power supplies make it possible to use either polyphase or single phase AC power sources. Remote transmission facility locations where polyphase power is not available can eliminate the cost of bringing polyphase power to the facility or the costs of converting single phase power to polyphase power.
Advanced signal processing enables both Real Time Adaptive Correction (RTAC) and Advanced Crest Factor Reduction (ACFR) that allow the RF power amplifiers to operate more efficiently closer to saturation than previously possible
Regardless of whether an air cooling system is used or a liquid cooling system is used, the energy consumption of the cooling system can be significantly reduced by carefully matching the system capacity to the ambient conditions. Variable speed cooling systems adaptively utilize thermal feedback to consume only as much energy as required for the current temperature and heat load.
There may be a small benefit to sharing a common air conditioning system across several transmitters, but there is a bigger benefit to sharing a common liquid cooling system across multiple transmitters. In some cases, it may even be possible to share the building’s liquid to air heat exchanger, thereby eliminating the need for separate liquid to air heat exchangers. This would be particularly attractive for transmission facilities atop high buildings.
HARRIS TOTAL COST OF OWNERSHIP ANALYSIS TOOL
Harris has been working with several customers, including visits to customer facilities to develop a comprehensive tool to evaluate and capture all the items that impact the TCO of a specific facility. An analysis tool is under development to make it easier to survey a facility and input all the relevant data to get useful information. This tool, shown in Figure-3, can also be used to design a new facility from the ground up for minimum TCO.
It provides a comprehensive inventory of all identifiable and quantifiable costs associated with operating a facility.
All of the baseline data related to the location based energy costs, HVAC, floor space, maintenance, and other costs are first entered into the tool. Comparisons can be made for the TCO of various transmitter types.
The energy consumption and cooling requirements for many different models of Harris transmitters are built into the tool for direct calculation of the total cost of ownership over various time frames.
Figure-3 shows an example of a TCO analysis of an air cooled transmitter. Figure-4 shows a similar example of the same TCO analysis for a comparable liquid cooled transmitter.
2500W AIR COOLED TRANSMITTER TCO EXAMPLE
2500W LIQUID COOLED TRANSMITTER TCO EXAMPLE
Inputs to the analysis include:
• Transmitter and operating mode (picks up all operating parameters)
• Transmitter acquisition, installation, and commissioning costs
• Facility location and energy cost per kW-Hr
• Heat to closed loop indoor environment or vented to outdoor environment
• HVAC acquisition and installation costs
• HVAC maintenance and replacement costs
• HVAC operating costs based on SEER rating, climate, ducting, etc.
• Liquid cooling system acquisition and installation costs
• Liquid cooling system operating costs
• Annual maintenance costs
• Annual facility rent based on volume occupied
• Training costs
Outputs from the analysis include:
• First year TCO including acquisition cost and training cost
• Annual ongoing TCO
• 5, 10, 15, and 20 year cumulative TCO
• Total heat output (BTU/HR), indoors and/or outdoors
• Cooling required (tons)
• Cooling energy consumption and annual cost
• Total annual energy consumption (kW-Hr), annual carbon emissions
• Footprint, volume occupied, and rental costs
The Harris TCO tool also includes a comparison tool, shown in Figure-5, which will allow comparison of various models of Harris transmitters to each other and to competitive transmitters. The payback period to overcome the differential capital expenditure with the reduced operational expenditure is also calculated. Figure-5 shows a TCO comparison of several air cooled transmission systems to a similar size liquid cooled transmission system.
TCO COMPARISON OF FOUR DIFFERENT TRANSMISSION SYSTEM CONFIGURATIONS
CHOICE OF TRANSMITTER COOLING TECHNOLOGY
The choice between an air cooled and liquid cooled transmitter has a high impact on the total cost of ownership particularly, if only one type of cooling is used throughout the broadcast transmission facility. The energy consumption of a liquid cooling system is a small fraction of the energy consumption of an air cooling system that moves a similar amount of heat from the building. As additional, new transmitters are added to a facility with existing air conditioning, there will be little need to add additional air conditioning capacity, but the inefficiency of the existing air conditioning system will still dominate the facility cooling system energy consumption. If a new facility or an existing facility is converted to all liquid cooled transmitters, the amount of air conditioning can be dramatically reduced to remove only the small amount of latent heat from the transmitters and auxiliary equipment racks.
Liquid cooled transmitters typically have twice the power density, per unit volume, of comparable air cooled technology. This is because the volume needed by the open area of the air cooled heat sinks is compressed down to the thickness of the liquid cooled chiller plates. A 2:1 reduction in floor space and vertical height (volume) can significantly reduce the cost of facility space especially in high rise buildings. Figure-7 and Figure-8 show examples of current production liquid cooled UHF power amplifier module. Figure-9 and Figure-10 show how liquid cooled PA modules are integrated into a complete transmitter system.
In configuring a transmission system there are a number of critical decisions to be made from the selection of transmission equipment – efficiency and cooling to the cooling technology used in transmitter, which have large impact on TCO. In addition to the initial hardware cost, broadcasters should consider all acquisition, operating and maintenance costs, all elements in power consumption budget and the necessary building volume and floor space needed to house the transmission equipment.
Harris has developed a prototype tool to make is easier to analyze and calculate the total cost of ownership for a broadcast transmission facility. This tool brings into focus many of the costs of facility operation that are often ignored when planning a new facility or upgrading an existing facility. When finalized, this tool will help the transmission facility designer make the right design choices to reduce the total cost of ownership.
 Freescale Semiconductor White Paper: “50 Volt LDMOS – An Ideal RF Power Technology for ISM, Broadcast and Radar Applications”
 Transmitter efficiency: Overview. (n.d.). Retrieved from http://te.cavellmertz.com/index_js.php
 Total cost of ownership. (2012, January 6). In Wikipedia, The Free Encyclopedia. Retrieved from http://en.wikipedia.org/w/index.php?title=Total_cost_of_ownership&oldid=469902093
 McLane, Paul “This Calculator Is ‘Cool Stuff’ Radio World, 06.01.2001 http://www.rwonline.com/article/this-calculator-is-%E2%80%98cool-stuff/23605
 Federal Electronics Challenge http://www.federalelectronicschallenge.net/resources/docs/costofown.pdf
 Total Cost of Ownershiphttp://techwise-research.com/types-of-studies/total-cost-of-ownership-tco