First considerations on the Balance of Plant for a HELIAS fusion power plant

Abstract

A first conceptual design of the Balance of Plant for a HELIAS power plant equipped with a Helium Cooled Pebble Bed (HCPB) Breeder Blanket (BB) is presented in this work. 5 inboard and 10 outboard cooling loops extract the heat from the blanket. Heat exchangers are used to transfer the thermal power from the helium to solar salt, which transports the heat out of the stellarator building and into an industrial 2-tank thermal energy storage system (IHTS/ESS). For electricity generation, the heat from the solar salt is transferred to the feedwater, which is boiled and superheated in the steam generator and then used in the turbine.In absence of a detailed design for the HCPB BB in stellarator geometry and the ex-vessel piping, a sensitivity study was carried out for the pressure drop of the cooling loops which showed that even small changes in the pressure drop have significant impact on the required pumping power.Finally, an exemplary runtime scenario is presented demonstrating the capability of a stellarator fusion power plant equipped with an IHTS/ESS to operate very flexibly (±20%) in an envisaged dynamic future energy system. Considering demand forecasts and the ESS, a stellarator fusion power plant (FPP) seems well equipped to cope with fluctuating grid demands within its technical limitations. If the conceptual idea for the HELIAS BoP as presented in this paper can be confirmed by more detailed technical studies, then a stellarator FPP could potentially contribute to grid stabilization in a future energy system while replacing fossil fuel power plants as a sustainable energy source.

Economically optimized design point of high-field stellarator power-plant

“…This overall optimistic PP efficiency results from the simplifications that were carried out in the 0D system analysis, which did not account for the electric power consumption of a series of auxiliary systems such as the tritium plant, power supplies for the magnet systems, additional coolant pumps, or vacuum pumps. These additional internal electric power requirements could amount up to 320 MW [19-21, 37, 42, 56, 115] reducing P e to 0.7 GW and the plant efficiency to η PP = 39%, similar to other reactors studies [19,56,115]. The reduction in P e would increase the COE to 71 $ MWh −1 and the TDC cost per watt to 4.2 $ W −1 and TCC cost per watt to 7.6 $ W −1 .…”

“…The thermal plant efficiency η th was varied from 35% to 70% to represent the current and possible improvements in thermal plant such as multi-stage improved Brayton or Rankine cycles, as well as the different operating temperatures [20,42,43,115]. Increasing η th has a major impact on reducing the COE, as it increases P e for the same P fus .…”