Hybrid Ground-Source Heat Pumps for Cooling Cellular Tower Shelters: from Campus Living Laboratory to Nationwide Deployment

Abstract

Tens of thousands of cellular towers are in operation across the U.S. Most of the cell towers are accompanied by a small shelter that houses electrical equipment continuously generating around 8 kWth of heat. The annual electricity bill for cooling these shelters with conventional air-source heat pump (ASHP) systems and their corresponding carbon footprint are significant. This paper presents methodology and results of techno-economic and environmental modeling of five different cooling configurations for shelters located across various states with different climates. The five configurations include: case 1: ground-source heat pumps (GSHP)-only; case 2: GSHP + air economizer (AE); case 3: GSHP + dry-cooler (DC); case 4: ASHP-only (business as usual – BAU); and case 5: ASHP + AE. With no consideration of incentives or rebates, base case results show that the total cost of ownership (TCO) for all configurations is the lowest for states located in cooler climatic regions (e.g., Maine, Minnesota, Colorado), and the highest for states located in warmer climatic regions (e.g., California, Florida). The configuration with the lowest overall TCO is case 5: ASHP + AE, and the highest is case 1: GSHP-only. Furthermore, the configuration with the lowest lifetime electricity consumption and CO2e emissions is case 2: GSHP + AE, and the highest is case 4: ASHP-only. With the use of energy-efficient GSHP systems, regions with high electricity prices and consumption will experience lower costs and environmental impacts from a reduction in operating conditions over the lifetime of the system (20 years). It is expected that the prospect of GSHP systems will be more favorable in the future than in today’s economy when incentives and rebates, increasing electricity prices, and carbon taxes are considered.