Italian startup Energy Dome has proposed a dome full of carbon dioxide (CO 2 ) gas to maintain electric grids when nonrenewables are not providing sufficient power (night time for solar and calms for wind). When the grid has excess electrical power, compressors inside the dome compress the CO 2 while a refrigeration/heater system takes away the heat of compression to a heat storage unit. The compressed CO 2 has a tremendous advantage in that it can become liquid at room temperature while storing a great deal of energy. When electricity is needed, the refrigeration/heater system puts heat into some of the CO 2 , and the warmed CO 2 becomes a gas, expands through a turbine, and thus delivers electricity back to the grid. Energy Dome claims that they should be able to store electricity at half the price of lithium batteries.