- Student Dissertation or Thesis
The electricity system is transitioning from a system comprised primarily of dispatchable generators to a system increasingly reliant on wind and solar power|intermittent sources of electricity with output dependent on meteorological conditions, adding both variability and uncertainty to the system. Dispatchable generators with a high ratio of fixed to variable costs have historically relied on operating at maximum output as often as possible to spread these fixed costs over as much electricity generation as possible. Higher penetrations of intermittent capacity create market conditions that lead to lower capacity factors for these generators, presenting an economic challenge. Increasing penetrations of intermittent capacity, however, also leads to more volatile electricity prices, with highest prices in hours that renewable sources are unavailable. The ability of dispatchable generators to provide energy during these high priced hours may counteract the loss of revenue from reduced operating hours. Given the disparate revenues received in this volatile market, the relative competitiveness of generation technologies cannot be informed by their cost alone; the value of generators based on their production profiles must also be considered. Consequently, comparisons of generator competitiveness based on traditional metrics such as the levelized cost of electricity are misleading, and power system models able to convey the relative value of generators should instead be used to compare generator competitiveness.
The purpose of this thesis is to assess the relative competitiveness of generation technologies in an efficient market under various penetrations of intermittent power. This work is specifically concerned with the relative competitiveness of power plants equipped with carbon capture and storage (CCS) technology, nuclear power plants, and renewable generation capacity. In order to assess relative competitiveness, this work presents an extensive literature review of the costs and technical flexibility of generators, with particular attention to CCS-equipped and nuclear capacity. These costs and flexibility parameters are integrated into a unit commitment model. The unit commitment model for co-optimized reserves and energy (UCCORE), developed as part of this thesis, is a mixed integer linear programming model with a focus on representing hourly price volatility and the intertemporal operational constraints of thermal generators. The model is parameterized to represent the ERCOT power system and is used to solve for generator dispatch and marginal prices at hourly intervals over characteristic weeks. Data from modeled characteristic weeks is interpolated to estimate generator profits over a year to allow for a comparison of generator competitiveness informed by both costs and revenues.
Scenario analysis conducted using the UCCORE model shows that the difference in energy prices captured by generators becomes an important driver of relative competitiveness at modest penetrations of intermittent power. Increasing the ratio of intermittent to dispatchable capacity causes intermittent generators to depress market prices during the hours they are available due to their coordinated output. Prices, however, rise in hours when intermittent capacity is unavailable because of scarcity of available capacity. This work develops the weighted value factor to compare the revenues of intermittent and dispatchable generation capacity. The weighted value factor is the market value of a generators production profile relative to an ideal generator dispatched at full capacity for all hours. The results show that as the proportion of intermittent capacity increases, the relative value of dispatchable generators also increases and at an increasing rate. At high penetrations of intermittent capacity, the power system experiences increasing risk of generation shortages leading to exceptionally high prices. In these systems, dispatchable generators able to capture peak pricing become most profitable. At lower penetrations of intermittent capacity, peak pricing remains influential, but is less extreme and the relative importance of low capital and fixed costs increases. The sensitivity of generator profitability to assumed value of lost load, oil and gas price, and carbon price is also assessed.
The key implication of these results is that efficient price signals may lead to opportunities for investment in dispatchable generators as the proportion of intermittent capacity on a power system increases. Markets and models that do not capture the full hourly volatility of efficient energy prices, however, are missing critical signals. The importance of these signals on relative competitiveness increases with the penetration of intermittent power. Without accounting for price volatility, markets and models will undervalue dispatchable capacity and overvalue intermittent capacity.