## 3 Levelised Cost of Electricity of CSP Plants Based on sCO\({}_{2}\)
### Overall Analysis of the Levelised Cost of Electricity
This is to be expected and is confirmed here by the larger production of electricity of the plant in Las Vegas. Another interesting aspect, which is not as evident, is the impact of the dispatch control scheme, which yields a very variable plant performance pattern. For supercritical Carbon Dioxide plants based on the Allam cycle, the dispatch control proposed in SAM by default (Cases 1 and 3) is able to produce 5 GWh/year more energy than that proposed in the SunShot Vision Study. In order to find the reasons for this, it is reminded that the latter scheme was based on lower power settings to extend the operating time of the plant in periods with expectedly low solar availability, as opposed to the scheme proposed by SAM where power generation is maximised regardless of a potentially higher number of start-ups. The superior performance of this approach will have to be compared against the economic impact of the latter on maintenance costs in an actual power plant. Alas, as expected, the higher yield of Cases 1 and 3 in both locations translate into higher capacity factors. Interestingly, the impact of dispatch control on plant performance for a conventional CSP plant based on a steam cycle is exactly the opposite. The dispatch control proposed in the SunShot Vision Study produces a higher yield than the default control proposed by SAM. The margin between the two is again in the order of 5 GWh/year, and the reasons for this are found in the off-design performance of the steam cycle, and to make it even more interesting, for a CSP plant using sCO\({}_{2}\) technology based on the Partial Cooling cycle, the annual production of electricity seems to be totally insensitive to the dispatchability scheme adopted, as shown in Figure 7. The patterns discussed are applicable to both locations, which supports their dependence on the characteristics of the power block and not on the boundary conditions of the power block. All this opens a very interesting research pathway incorporating the combined optimisation of both cycle technology, cycle layout and dispatch control scheme. From a quantitative standpoint, the foregoing qualitative considerations translate as follows, for the cases considered. A CSP plant based on the Allam cycle in Las Vegas achieves 10% higher yield and capacity factor than if it were located in Tonopah and the difference would increase to about 12.5% if a Partial Cooling sCO\({}_{2}\) or a steam cycle were used. Regarding dispatch control, the SunShot Vision Study setting yields 3% higher \(E_{year}\) and \(CF\) when using the Allam cycle whereas a 3% drop in these parameters must be expected when considering a steam-turbine CSP plant. Further to the discussion in the previous paragraph, this can also be explained by the fact that SAM's Default and SunShot Vision Study's dispatch control modes are specifically designed for steam and sCO\({}_{2}\) power cycles respectively. The same capacity to significantly change the results is not observed when assessing the two sets of financial assumptions. The input parameters considered in the SunShot Vision Study always lead to better financial results than SAM's, yielding higher \(NPV\) and lower \(LCoE\) for a given location, as shown in Figure 8. This is mostly due to the longer lifetime and higher \(IRR\) considered, even if the former model presents a larger debt fraction, set to 60% (versus 50% for SAM's default case) of the total capital cost. It is also observed that \(NPV\) depends on the financial model given the minor deviations seen between different locations, cycles or dispatch control systems. On the other hand, \(LCoE\) happens to be strongly affected by all the factors considered so far. In particular:  
* Las Vegas yields lower \(LCoE\), even if some \(LCoE\)s obtained with the SunShot Vision Study case considering the Allam cycle in Tonopah are comparable to those obtained by the SAM setting in Las Vegas, regardless of the cycle used.