Thread by @bananelectrons

#ThursdayMoney 🧵

This week we got deep analysis of possible #FusionEnergy cost valuation with @JesseJenkins in the authors' list!🙀🙀🙀

While it is difficult to determine cost of a particular design when much of underlying fusion technology has yet to be developed, it is possible to set cost targets by determining the value of a design with a particular set of operational parameters in a simulated future scenario

This is the first study of the equilibrium value of fusion at various levels of capacity penetration for the United States, and the first investigation of the value of integrated thermal storage for fusion plants in an hourly model

Authors developed an abstracted operational model for a fusion plant and linearized it for implementation in GenX, a linear programming electricity system capacity expansion model
The model is based on a pulsed tokamak, since tokamaks are the most mature concept

They used GenX to study the value and role of fusion in a decarbonized electricity system circa the 2040s, optimizing electricity technology investments and hourly operation across 20 model zones to minimize total system cost

In order to understand the design space of model tokamaks, athours varied tokamaks' behavior from pulsed to nearly steady-state, and varied the variable operations and maintenance cost to reflect uncertainty in the costs of replaceable components such as the blanket and divertor

Authors determined cost thresholds as function of capacity penetration for a range of plants in three main scenarios

The pulsed tokamak designs studied range from pessimistic to optimistic
While all plants use the same parameters for their power conversion systems, the fusion cores have different operational constraints and costs described in the table above

The three scenarios, termed low, medium, and high fusion market opportunity, differ in the cost of fusion’s competitor technologies and quantity of flexible loads in the system, but all have identical nominal loads, with average and peak values of 600 GW and 1100 GW, respectively

Figure shows the cost thresholds for a marginal plant for each plant designs in each scenario, as the fusion capacity penetration is set from 10 GW to 350 GW

This figure shows how cost thresholds for fusion at various capacity penetrations vary between the 3 main scenarios with the cost of other resources

Particularly at low fusion capacity penetrations, the cost of fission strongly affects the potential value of fusion
NG-CCS = natural gas generation + carbon capture&storage

Pulsed tokamak designs may require intermediate thermal storage system (TSS) to supply power conversion system (PCS) with heat during dwell period; PCS typically cannot handle sudden decline in heat as end of the fusion pulse
these systems store few minutes of heat
f.e.

Authors independently optimize the core capacity, storage energy capacity, and PCS generation capacity in each model zone
This allows for generators to be oversized relative to their fusion cores, in order to serve a peak in demand

The option to build storage is more valuable at lower fusion capacity penetrations because the optimal storage quantity per plant is larger

This suggests that a TSS could be especially valuable for the first generation of fusion plants

As fusion penetration increases and the total thermal storage capacity along with it, the marginal value per unit of additional storage capacity declines

Thermal storage modifies the operational patterns of the cores and PCSs and increases the utilization of the plants
The optimal thermal storage system (TSS) duration generally ranges from 2 h to 8 h, depending foremost on the storage capacity cost,...

...and the optimized generator capacity generally ranges from 1.1 to 1.35 of the amount needed to serve the fusion cores without storage

The TSS increases the value of the fusion core capacity by $490/kW, about 20%, as it increases its annual utilization from 87% to 93%, and increases the net output of the plant from 82% to 90% of its potential

Optimal hourly operational behavior of the fusion cores and PCSs for plants with pessimistic cores with and without a TSS option, in a typical geographic region of a medium market opportunity scenario with a total system fusion capacity of 100 GW

Part (a) shows load in zone, parts (b) and (d) shows thermal power output of core normalized by its peak power, parts (c) and (f) show net generation of plant normalized by its long-run capacity, and part (e) shows state of energy storage in the TSS measured in hours of the peak

value of fusion plant depends strongly on its marginal cost of net power generation, so fusion developers must take into account costs of operating and maintaining future reactors, not only the capital cost

Plant value depends only weakly on the particulars of an hourly-scale pulse cycle when examined with an hourly resolution

This study finds that equilibrium capacity penetration of fusion increases significantly with relatively small decreases in cost of marginal plant

This suggests that if cost targets for initial market penetration can be met, further cost decreases could allow fusion to reach a much higher capacity

Finally, integrated thermal storage such as molten salt increases the plant value by a modest amount, by better serving daily demand cycles It would be especially valuable while the total fusion capacity is small, which could help fusion find an initial market

The value of fusion energy to a decarbonized United States electric grid

@JacobASchwartz @JesseJenkins
@ScottCHsu @swurzel