In the case of the Gas-TESS I think the idea is biogas is being produced anyway and has to be dealt with (releasing it into the atmosphere is worse than releasing co2, biogas is mainly methane) so the options are burn it in biogas engines and generate electricity when it might not necessarily be needed or flare it, which wastes it and produces CO2 anyway. The third option is to use the TESS to store the energy for when it is needed, reducing the amount of power needed to be drawn from the grid (some of which is generated by fossil fuels, so additional co2) and also produce heat for the biodigesters.
In the case of the TESS-Ind and TESS-Grid, the aim is to charge it electrically, which of course means it can be charged with renewable energy, and displace other means of heating, for example, the burning of LPG.
Thats the theory, what we are waiting on now is whether it actually works (I.e. has a satisfactory round trip efficiency in the real world), and delivers a great enough cost saving in reality.
