Concentrating Solar Power in the KAPSARC Energy Model

Update: Since this article was published, we have released documentation for the KAPSARC Energy Model. It can be found here.

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--> KAPSARC Policy Paper

The KAPSARC Energy Model (KEM) is an economic planning tool that is designed from the ground up for Saudi Arabia. It consists of six sectors. From the linked paper:

The representation of CSP in KEM is limited to parabolic trough technology with molten salt thermal energy storage. The storage mechanism is allowed to store enough heat to operate the plant at full capacity for up to eight hours. Figure E-4 (below in the linked PDF file, page 26) illustrates the approach taken to model the operating decisions of a CSP plant. Heat transferred out of the solar field may either be used to provide instantaneous heat to the steam generator or be stored for use when it is needed. Using the direct normal irradiation (DNI) measurements made by the National Renewable Energy Laboratory (NREL) and King Abdulaziz City for Science and Technology (KACST) (NREL and KACST (2013)), the amount of solar irradiation directly incident on the aperture plane of the collectors is first calculated to determine the rate of energy transfer from the solar field. Single-axis tracking is done by arranging the collectors along the north-south axis and varying their tilt angle from east to west throughout the day.

Because of irreversiblilities such as friction effects, we consider a 35 percent loss in heat between the point of reception and either the storage device or the steam generator (Rovira et al. (2013)). An energy balance is performed on the storage mechanism that, once heat is stored, considers cycling losses and hourly heat dissipation. Madaeni et al. (2012) estimate a cycling loss of 1.5 percent, and Sioshansi and Denholm (2010) document a 0.031 percent hourly loss of stored heat for a molten salt system. We incorporate a Rankine cycle thermal efficiency for a typical CSP plant to calculate the amount of electricity generated from the heat input.

Like Sioshansi and Denholm (2010), we assume that CSP plants do not contribute to the planning reserve margin due to limitations in ramping and start-up. Although this is the case, we can set the model, as we have done in the policy paper, to allow any percentage of CSP capacity to contribute to the margin.