Proper AC To DC Conversion—A Simple Way To Reduce Energy Costs

Note: Third in a series on Energy Solutions.

The demand for expanded wireless coverage and capacity means more power is needed for cell sites. Increased coverage and capacity equals an increase in energy costs for operators. As energy costs continue to rise, effectively managing network energy demands becomes even more critical.

Most cell sites utilize DC power—either -48VDC or +24VDC. The grid AC power is converted to DC power by rectifiers, which typically have 89 to 92 percent peak efficiency. Remember the words “peak efficiency” because they are very important in this context.

Peak efficiency drops by several percentage points when the load is 40 percent of the DC power plant capacity. Most sites are configured with redundant rectifier units for several reasons: worst-case scenarios for peak power requirement, redundancy and increase bandwidth demands. They typically operate well below the 40 percent capacity and at lower efficiency values. This results in increased energy consumption and incremental heat loss, which must be removed by expending additional energy through air-conditioners or DC-powered fans.

So, how do we ensure that DC rectifiers in cell sites operate at peak efficiency during all conditions? Well, it is important to implement an energy management scheme using a system controller that continuously measures the current load and allows the minimum number of rectifiers to provide the required power. The system controller also loads different rectifiers in sequence, so that they share the duty cycle equally over time. Sudden load changes are handled without service degradation or interruption by the batteries and the quick response of the rectifiers.

Today, rectifiers are available providing up to 94 percent efficiency and costing slightly more than lower efficiency ones. Using high-efficiency rectifiers with an energy management scheme reduces site energy consumption and heat losses—approximately five percent in yearly energy savings. You may think that’s a small number; however, it is important to note that any reduction in energy consumption due to higher efficiency not only saves site operating expenses, but also reduces the costs associated with cooling and carbon dioxide emissions associated with grid power generation.

CommScope integrates the latest generation of high-efficiency rectifiers in our power and power backup solutions, helping operators lower their energy consumption and providing them with significant cost savings.

So, what types of energy concerns are you having at your cell site?