At an international industry conference in December 2015, Maarky Thermal Systems president Dr. Ranga Nadig delivered his paper entitled “Nitrogen Based Thermal Storage Medium for Concentrated Solar Power Plants”. The said paper is a patent pending concept of Maarky Thermal Systems.
The paper notes that in a Concentrated Solar Power Plant, thermal storage is used to negate the loss of electrical power generation at night. At daytime the thermal storage material is heated to higher temperatures and then stored in huge containers. In the evening, high pressure steam is generated using the energy from the heated material. This high pressure steam powers a turbine generator which produces electricity.
The preferred thermal storage material is molten salt. Using molten salt poses a number of difficulties. This includes having to obtain it in large amounts and transporting it to the solar plant which may be in a remote location. Inconsistencies in the salt composition can cause changes in thermal properties and melting temperature. The freezing point of molten salt is also at 550ºF needing expensive additives to lower the freezing point.
Using nitrogen has a number of advantages over molten salt. It can be simply be extracted from the air at the plant site and with 80 percent of the atmosphere composed of nitrogen the supply is abundant and free. It can be stored in huge containers and has stable thermodynamic properties. The freezing problem no longer exists as nitrogen stays in gaseous state over a wide temperature range.