14D tech vs Snowy 2.0 Hydro, page-22

They are using a gas burner system at SA Water to heat the silicon, then using the heat in that stored system to heat air and run it through a turbine. 50% electrical efficiency would be quite good, considering the most efficient gas engine generators don't usually operate at 50% electrical efficiency.

The silicon unit or heat accumulator and the turbine exhaust are used for heating sources. This combines with the electrical output for a CHP overall efficiency which hasn't been completely proven yet - though the claim is in the 80-90% range that most CHP setups operate at.

They are claiming this is more efficient than usual as the focus is in heat recovery and utility. Lower emmissions and with the ability to run for a period of time when gas isn't available, which is yet to be determined or proven it seems. Also with a chance to time shift the heat stored for use later.

There is an electric heated version also which aims to take advantage of cheap power to heat the unit and the output is sent to industrial heat users and when the big bucks are on, they export electricity at a profit.