Renewable energy is on the rise while utility providers are required to either reduce carbon dioxide emissions or to increase their percentage of renewable energy sources. One of the major issues hindering this rise is to overcome the intermittent nature of renewable energy such as solar and wind, as the sun is not shinning at night and wind tends to be strongest during night. Mechanisms to store surplus energy to meet the continuous demand throughout the day and to meet the peak load demands are critical for a robust and vibrant renewable energy development. Popular methods to achieve this are Pumped-Storage Hydropower (PSH) system and Compressed-Air Energy Storage (CAES). A new method, Pumped-Heat Electricity Storage (PHES) system, is catching on to further the energy storage technologies in helping mitigate the global warming.