Multi-Criteria Economic Analysis of a Pumped Thermal Electricity Storage (PTES) With Thermal Integration

Abstract

The interest toward large-scale electric energy storage technologies is increasing with the large deployment of new renewable capacity. In case of several hours of storage duration, there is no consensus on which technology is the most suited. Several technologies have been recently proposed, among which is pumped thermal electricity storage (PTES), which is a technology based on the idea of storing electrical energy as heat. PTES is usually less efficient than electrochemical batteries, but it is characterized by a lower cost per kilowatt hour, which could make it a suitable alternative for applications with long storage duration. In this study, a recently proposed PTES system based on the use of heat pumps and organic Rankine cycles is investigated from a thermo-economic point of view. The system is powered by both electric and low-grade thermal energy, thus taking advantage of waste heat to increase the electric performance. As the system design both affects efficiency and cost, a trade-off must be found. In this study, this task was performed by means of a multi-objective optimization approach. The relation between electrical round-trip efficiency and system cost is analyzed, and the impact of several design specifications such as boundary conditions, nominal power rating, and storage duration is discussed. Finally, the results are generalized by defining some cost scaling correlations. Large-size configurations (5 MW of charging power for 8 h of storage) may achieve equipment purchasing costs as low as 140 e/kWh and 2,300 e/kW, with an electrical round-trip efficiency of 0.6. These results show that the investigated technology may be suitable in the context of large-scale and long-duration energy storage.

Advanced exergy analysis of a Joule-Brayton pumped thermal electricity storage system with liquid-phase storage

“…In this investigation, the power capacity is fixed to 10 MW and the charge/discharge times are set to 6 h. The thermodynamic parameters of the PTES system are optimised using the optimisation method [71] to achieve the highest roundtrip efficiency considering the limitations of the working temperature of the storage materials and the manufacturing capability of the main components in practical applications. A sequential quadratic programming algorithm [72] has been proven to be the most reliable method for solving the optimisation problem. A multi-start strategy that begins from different randomly selected initial points is utilised to prevent the solver from being trapped in local minimum solutions.…”

Rankine Carnot Batteries with the Integration of Thermal Energy Sources: A Review

“…To be fair, LAES, and analogous systems, may also benefit from the use of waste heat. However, LAES internally produces and recovers heat up to 200 • C from the charge phase [38,39]. Therefore, low-temperature heat sources may not be useful.…”

Storage Futures Study: The Challenge of Defining Long-Duration Energy Storage

“…Figure 2 takes the same approach as in Figure 1, but in this case calculates the duration of storage needed for New York, accounting for the different size of the system. 6 Because New York experiences longer load peaks (illustrated here by the purple area being wider), that system would require about 5.5 hours to achieve the same net load reduction in proportion to the Florida case above.…”

“…Establishing the capacity credit of storage as a function of duration is important for many regulatory and market reasons, including the ability of a utility or load-serving entity to meet resource adequacy standards set at the local, state, or regional level. It also establishes the ability of individual plants to receive capacity payments in wholesale markets or as part of power purchase agreements 6. The peak load in Florida in this year was about 1.6 times that in New York, so we are simulating a proportionally smaller storage power capacity (1,065 MW in New York vs. 1,740 MW in Florida).…”