Editor’s note: Sad reality but true: the handsets and smart phones have all the glamour and get all the attention, but it’s the “invisible” network and management of base stations and cell sites that makes all this mobile connectivity really possible. And, a large and even less-recognized part of a successful cell site design is the power subsystem, both primary and backup.
The white paper “Hybrid Energy Deployment: What to Consider When Enabling Alternative Energy Sources at the Cell Site” from Emerson Network Power (a business of Emerson) is a detailed, technical look at these issues, complete with graphs, charts, analyses, discussion, and equations. It provides insight and recommendations for properly evaluating, selecting and operating smart hybrid-energy solutions at telecom cell sites.
It explores opportunities for improvement ranging from more precise configuration and dimensioning of hybrid systems to implementation of intelligent hybrid technologies that make hybrid solutions even more efficient and change the value proposition for some network providers.
Among the issues which this paper discusses in much greater detail, for designers considering hybrid technologies or looking to maximize an existing hybrid infrastructure, are these:
●Active Management and Smart Hybrids: Hybrid deployments traditionally have been purchased as static hardware with a general maintenance or warranty contract only. This is an acceptable solution to minimize immediate capital spending. However, for those operators focused on minimizing medium- to long-term operational and capital costs and maximizing ROI, smart hybrids with active management can aid with achieving additional savings.
Advanced analytics and remote management can deliver measurable load, environmental and performance improvements. Intelligent solutions can, for example, alert if a battery cell may be damaging an entire string or if a single dirty solar panel is reducing the output of an entire array. They also can adjust cooling operation if load or temperatures vary, change maintenance dispatch schedules if a generator is operating less than usual, and notify if fuel quality degrades.
●Generator: Generators that are part of a dynamic hybrid energy solution are most cost efficient when properly dimensioned and intelligently managed with the provider’s operational cost goals in mind. A chronological on/off with an existing generator can work—but will it ensure optimal maintenance cycles, maximum battery life and efficiency, or factor in sun position?
The hybrid generator solution is best engineered by factoring in these and other energy, load and site considerations and will affect the selection of generator size, alternator profile, fuel source and security measures, and more. Further, by actively managing a smart hybrid site, generator maintenance cycles and fuel usage can be further cost optimized as site and load conditions evolve.
●Batteries: In hybrid solutions, batteries are critical elements for successful cost minimization. Errors in battery selection and operation can be among the most costly for a provider, yet are the most common.
Selection of the right batteries (among many options for chemistry and construction) must be based on clear capital and operational goals, rather than trends. More than any other element, batteries will benefit from active management of charge, ensuring long service life, minimal site cost and maximum uptime for the provider.
●AC Line Conditioning: Some hybrid solutions are in areas with grid power that is either unreliable or low quality. Ensuring that proper technologies are used to protect the active devices on the site is imperative. Insulation and voltage regulation are effective and cost efficient.
More sophisticated techniques such as phase selection, filtering, power source blending, and other methods further contribute to leveraging the grid, while not falling victim to it. Smart hybrids with active management in these environments are particularly important to reduce generator run time and ensure best charge conditions for batteries. This will minimize operational costs and extend the life of the site investment.
●Solar: Solar is becoming a viable power source for cell sites around the world. Proper use of solar power begins with understanding solar intensity and seasonal variances in order to design sites for their unique physical conditions. Solar also is a low-density power solution and requires the greatest space or creativity to deploy.
Security and maintenance also must be considered—protecting panels from theft, misalignment, and sub-optimal operation due to dirt is important. Periodic maintenance is required, but a smart hybrid system, actively managed, can minimize cost by dispatching service personnel only when cleaning or repair is necessary.
●Wind: Wind is best in an array of turbines for large power delivery connected to a reliable electric grid. The scale of the utility turbines with multi-point deployment allows for cost-effective management of maintenance and wind variability. The use of wind turbines at a cell site needs to account for community acceptance, for the ability to run unattended under all conditions, and for the inevitable windless days. For a single-point, off-grid cell site, wind is a challenging power source to be effective—for cost or energy—but it can be successful in some locations.
●Fuel Cells: Fuel cells are an option from an environmental point of view, and there are various technologies that have been deployed successfully. The biggest challenges to cost-effective use at cell sites are the startup time—a battery is always necessary—and the fuel supply-chain. Until these two items are addressed, this technology is best directed to sites with strict emissions mandates.
About the author
Dave Wilson is Application Engineering Director for Energy Systems at Emerson Network Power.
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