A Vision for Autonomous Powered Small Cells in an Energy Constrained 5G Network with Emphasis on Energy Storage

This paper provides a vision for autonomously powered small cells placed within an energy constrained telecommunications network where easy access to power without grid connection will be critical. There has been a significant transformation in the telecommunications network in recent years where the requirement for more bandwidth has shifted the focus from coverage to increasing capacity owing to the proliferation of mobile connectivity for social networking, on-demand video and gaming. Small cell technology is the telecommunication industry's solution to this problem for hot spot coverage and maximum utility of the available spectrum. Non-conventional deployment scenarios will be encountered owing to the small size of future products and the dense networks within which they operate where the connection to the electrical grid maybe prohibited by cost or availability. We propose an alternative energy harvesting and storage solution to power the vast number of small cell products using a combination of solar panels, rechargeable batteries and smart control of the product functionality to enable total system energy optimisation. The efficiency of solar cells and in particular the energy density (Wh/L) of rechargeable battery technology has been identified as major hurdles preventing the mass adoption of autonomous power solutions. In particular, this paper will focus on the energy storage requirements of small cells where the critical design parameter is small size and therefore high energy density (Wh/L) is a primary driver for future telecommunications battery technology. Maximising the volumetric capacity of both anode and cathode with a large potential difference between them is the key to obtaining high energy density. For nearer-term impact a combination of a high volumetric capacity silicon anode with a lithium cobalt oxide cathode has been identified as having the appropriate properties to meet the needs of high energy density and long lifetime within telecommunications deployments. Such a system could have an energy density twice that of current state-of-the-art Li-ion batteries. A research roadmap is presented that describes longer term potential chemistries with even greater energy density, however, significant research effort is required to progress this technology.