Two -Phase Polytropic Energy Storage

The University of Edinburgh team will work with engineers at Artemis Intelligent Power Ltd to design a compact grid-scale
energy storage facility. The energy storage concept uses a polytropic compression and expansion in a Joule or Brayton
cycle to convert mechanical work to heat, and back. For these processes it uses large, slow moving, piston machines,
giving adequate time for heat exchange processes to occur with high efficiency. Secondary liquids are introduced into the
working gas to absorb and reject heat, so that it can be transferred directly into unpressurised thermal stores (without
recourse to large heat exchangers) - one very hot, the other very cold. All of the processes are theoretically fully reversible.
Each process is being designed to occur with minimal losses, with the aim of equaling or exceeding the efficiency of
pumped hydro storage. Artemis Digital Displacement machines provide the controllable wide motion ratios required to
efficiently interface the high-speed electrical generators to the low-speed compressor expander machines such that
constant power levels are maintained.
This being a first phase programme, it is anticipated that the end goals of this 12 month project will be an outline design,
system simulation model, some critical-path component development to verify performance prior to moving onto building a
pilot energy storage facility.

The electrical grid needs storage to absorb diurnal variations solar power, it also needs storage to buffer the variability of
wind, wave and tidal power. Arguably, with a lot of inexpensive storage available on the grid, much more renewable
generation can be integrated. Conventional generation can be displaced. The reduction of reliance on fossil fuels will
increase the energy security of the UK and improve air quality. It will also demonstrate to other countries a route forward to
decarbonising our global economy and thus reducing one of the significant drivers of climate change.
People involved in the manufacture and operation of such facilities will gain their livelihoods from them. The relatively
compact critical components can be manufactured in the UK and exported elsewhere, improving the trade balance of the
UK and thus increasing wealth.
Everyone benefits! Except perhaps people involved in mining and selling coal.