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Graphite Storage - How it Works

The function of the energy storage block developed by CBD is to store large amounts of thermal energy for later use. The process takes advantage of the patented process in which graphite is heated to high temperatures, with the heat extracted at a later time using imbedded heat exchangers. Key design elements of the energy storage module are:

» Structure size standard and based on a 20ft container footprint;
» Graphite heated by distributed Silicon Carbide heating elements (418kW);
» Energy extracted by imbedded stainless steel high pressure piping;

In its current design configuration, each block contains approximately 19 tonnes of graphite and will store approximately 5.5MWh of thermal energy. The Energy Storage Module (ESM) consists of a number of high quality graphite blocks stacked together. Installed within these blocks are heating elements used to heat the graphite and the unit operates at high temperatures of up to 650°C. Insulation surrounding the ESM minimises heat loss and allows the energy to be stored for extended periods of time. Energy is then extracted from the ESM when required by passing water through heat exchangers within the graphite block. As the block is at a high temperature, the water is converted into steam and then passed through a steam turbine generator to convert the heat into electricity.

For any particular application, a number of these modules are interconnected to form the RAPS Energy Storage System.  This system is an integrated energy storage technology which utilizes synthetic graphite to store thermal energy.

The key processes of the RAPS Energy Storage System are:

» Capture of electrical energy input (from the grid or renewable sources), via an array of resistive heating elements which are embedded in graphite blocks

» Storage of heat within graphite blocks which are capable of storing large amounts of thermal energy at high temperatures for relatively long periods of time with minimal loss of energy

» Extraction of energy, via a system of heat exchangers embedded in the graphite blocks.  The high thermal conductivity of the graphite allows the heat to be quickly and efficiently transferred to the heat exchangers.  The working fluid within the heat exchangers, typically water, is heated to produce superheated steam.  This steam can be used to drive a conventional steam turbine/generator set to produce electricity or the steam can be used to transfer thermal energy directly to another application.