Abstract
One of the main challenges for a further integration of renewable energy sources in the electricity grid is the development of large-scale energy storage systems to overcome their intermittency. This paper presents the concept named CHEST (Compressed Heat Energy STorage), in which the excess electricity is employed to increase the temperature of a heat source by means of a high-temperature heat pump. This heat is stored in a combination of latent and sensible heat storage systems. Later, the stored heat is used to drive an organic Rankine cycle, and hereby to produce electricity when needed. A novel application of this storage system is presented by exploring its potential integration in the Spanish technical constraints electricity market. A detailed dynamic model of the proposed CHEST system was developed and applied to a case study of a 26-MW wind power plant in Spain. Different capacities of the storage system were assessed for the case under study. The results show that roundtrip efficiencies above 90% can be achieved in all the simulated scenarios and that the CHEST system can provide from 1% to 20% of the total energy contribution of the power plant, depending on its size. The CHEST concept could be economically feasible if its capital expenditure (CAPEX) ranges between 200 and 650 k€/MW.
Highlights
One on the main challenges in the current energy context is a further penetration of renewable energy sources (RESs) into the electricity grid
Later, when the hourly energy price is greater than the average energy price of that month, the organic Rankine cycle (ORC) starts working and the compressed heat energy storage (CHEST) system is discharged
The high-temperature water tank (HTWT) is progressively filled with water coming from the low-temperature water tank (LTWT) and their levels of charge change
Summary
One on the main challenges in the current energy context is a further penetration of renewable energy sources (RESs) into the electricity grid. The previous systems present drawbacks related to location constraints and to their negative environmental impact [4] Another technology is being developed, based on thermal energy storage (TES). Steinmann [6] compared different electricity storage alternatives, such as CAES, power-to-heat-to-power and PTES, in terms of efficiencies and costs He explained the possibility of using the electric energy and the thermal one, enabling a better adaptation to the customer needs. Jockenhöfer et al [5] studied a CHEST system coupled with a low-temperature heat source Their model refers to a system with an input power of 1 MW working in steady-state conditions. Techno-economic assessment of the CHEST system when introduced to the Spanish technical program [20], which includes thermodynamic interactions of the and ORC, their load behavior, and the power profile of the available energy to charge the system.
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