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This poster describes efforts to analyze cycle performance of particle pumped thermal energy storage (PTES) system with concentrating solar power (CSP).
Coupled thermal-hydraulic-mechanical (THM) modeling is applied to investigate the performance of a seasonal high-temperature aquifer thermal energy storage operation based on data and conditions from current site investigations at the Geostorage Forsthaus pilot project in Bern (Switzerland). The model includes subhorizontal sand lenses of various lengths and dips that are embedded in a low permeability clay matrix. Thermal energy storage is simulated by seasonal injection and withdrawal of hot (up to 90 °C) water from a main well, with reservoir pressure regulated by two auxiliary wells at a distance of about 70 m from the main well. The results show how targeted injection into deeper permeable storage formations, along with active deep well pressure control, can effectively minimize geomechanical impact and the potential risk of damaging subsurface storage and sealing formations, or even surface facilities. With such pressure control, the subsurface mechanical responses are dominated by thermal strain and stress, which can be monitored with subsurface fiber optics. The study demonstrates how coupled THM modeling can be applied for the design of a safe and efficient thermal energy storage operation, and how subsurface fiber optic monitoring can be applied for performance confirmation, allowing for more confident operational forecasting.
Free from siting constraints, thermal energy storage (TES) shows promise as an economical alternative to traditional pumped-storage hydropower (PSH) and compressed air energy storage (CAES). As potential thermal energy storage media, many solid particles demonstrate stability over wide temperature ranges which allows for increased sensible energy storage density and is essential in achieving low-cost storage. Silica sand, in the form of a-quartz, is one such candidate. This work presents a brief review of relevant silica thermophysical properties and further investigates the thermal stability of silica particles as a candidate TES media by subjecting them to two different thermal campaigns: (1) a 500-hour thermal treatment at 1200°C under varied atmospheres; and (2) cycling 25, 50, and 100 times between 300°C and 1200°C. For both campaigns, particle stability is examined by means of pre- and post-treatment Mie scattering. An additional XRD analysis is conducted for the 500-hour treatment in air. Results indicate limited changes in both particle distribution and crystallographic structure which is promising for the application as solid particle media for thermal energy storage.
Cost-effective energy storage is a critical enabler for the large-scale deployment of renewable electricity. Significant resources have been directed toward developing cost-effective energy storage, with research and development efforts dominated by work on lithium ion (Li-ion) battery technology. Though Li-ion batteries have many attractive qualities, it is not clear whether they can provide an affordable levelized cost of storage (LCOS) for certain applications, such as buildings. Buildings consume most of the world's electricity, and as much as 50% of their consumption goes toward meeting thermal loads. Thermal energy storage (TES) can provide a cost-effective alternative to Li-ion batteries for buildings; however, two questions remain to be answered. First, how much of total building energy storage requirements can be met via thermal storage for building loads? Second, can the LCOS for TES be favorable compared with Li-ion batteries? In this perspective, using the United States as a case study, we show that the total requirement for TES in buildings is in the range of ~1200–4500 electrical GW h, depending on the fraction of solar versus wind in the generation mix. Furthermore, we show that with at least 25% wind generation, all of the storage needed by buildings to support the grid can be met by TES. We also introduce a framework to calculate LCOS for on-site TES in buildings to enable a direct comparison with electrical storage technologies such as Li-ion batteries. This is not trivial, because the input energy type for TES (electricity) differs from the output energy type (thermal energy), and the efficiency can depend on ambient conditions. Our LCOS analysis shows that in many situations, TES can be more cost-effective for buildings than Li-ion batteries. We conclude our perspective by discussing future research and development opportunities that can significantly advance the deployment of TES for buildings to help enable a renewable electricity-dependent grid.
The development of low cost thermal energy storage technologies is discussed in terms of near term oil savings, solar energy applications, and dispersed energy systems for energy conservation policies. Program definition and assessment and research and technology development are considered along with industrial storage, solar thermal power storage, building heating and cooling, and seasonal thermal storage. A bibliography on seasonal thermal energy storage emphasizing aquifer thermal energy is included.
Thermal energy storage (TES) deployed with concentrating solar power (CSP) has shown value and capabilities in generating dispatchable power. It has attracted significant interest for potential roles in energy storage for various capacities and applications. Energy storage plays an important role in expanding renewable generation and is becoming indispensable in future carbon-free electric power. TES development and deployment provide various possibilities for electric storage and have shown advantages in capacity and flexibility to support renewable integration. In addition, renewable energy integrated with a low-cost TES system can potentially provide a reliable thermal energy supply to displace fossil fuels for broad decarbonization. Varieties of TES technologies and developments breed new areas of growth in TES materials, designs, components, and system configurations, which provide opportunities for substantial cost reduction and performance improvements to meet the technoeconomic challenges in practical applications. This chapter will describe recent progress in thermal energy storage research and development and primarily focus on sensible heat storage and its applications in supplying reliable electricity and industry process heat by integrating with variable renewable energy.
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Cold Underground Thermal Energy Storage (Cold UTES) is an ultra-long duration grid energy storage technology. With Cold-UTES, low-cost grid power is converted to cold thermal energy and stored in the native subsurface rock at the point of use. Cold UTES is one approach within the general category of engineered geothermal systems. Cold UTES for peak-hour cooling of data centers (DCs) was studied for deployment in Maricopa County, Arizona and Loudoun County, Virgina using thermal storage capacities from 4 GWh-th to over 1,000 GWh-th (>1 Terawatt-hour). The two sites have different power and transmission systems, available grid energy resources, daily and seasonal load profiles, weather conditions, and grid regulatory requirements. The study results indicate high value for both locations and because of this, likely indicates value across most of the US and the world. The basis of the study was a 1,000 MW-e hourly electric use of DC computing and auxiliary loads, which was modeled as 1 GW-th of thermal load to a dry cooled heat rejection system - i.e. a cooling system that does not consume water. The electric power required for cooling the DC varies as the air temperature changes. In cold weather only the dry-coolers are used, with an electrical load for cooling load as low as 10 MW-e. In hot summer hours, chillers and dry- coolers are required, which raises the electrical load for cooling load to as much as 300 MW-e. The continuous and peak cooling electrical loads result in a grid interconnection requirement of no less than 1,300 MW-e. From both a grid and thermal design modeling perspective the 1.3 GW-e could either be a single facility or result from the total load at multiple sites.
Thermal Energy Storage for Industrial Applications is a major thrust of the Department of Energy's Thermal Energy Storage Program. Utilizing Thermal Energy Storage (TES) with process or reject heat recovery systems is shown to be extremely beneficial for several applications. Recent system studies resulting from contracts awarded by the Department of Energy (DOE) identified four especially significant industries where TES appears attractive - food processing, paper and pulp, iron and steel, and cement. Potential annual fuel savings with large scale implementation of near term TES systems for these industries is over 9,000,000 bbl of oil. This savings is due to recuperation and storage in the food processing industry, direct fuel substitution in the paper and pulp industry and reduction in electric utility peak fuel use through inplant production of electricity from utilization of reject heat in the steel and cement industries.
The Seasonal Thermal Energy Storage (STES) Program designed to demonstrate the storage and retrieval of energy on a seasonal basis using heat or cold available from waste or other sources during a surplus period is described. Factors considered include reduction of peak period demand and electric utility load problems and establishment of favorable economics for district heating and cooling systems for commercialization of the technology. The initial thrust of the STES Program toward utilization of ground water systems (aquifers) for thermal energy storage is emphasized.
This study examines the thermal performance of concrete used for thermal energy storage (TES) applications. The influence of concrete constituents (aggregates, cementitious materials, and fibers) on the thermal conductivity and specific heat are summarized based on literature and via experimentation at elevated temperatures. It is indicated that concrete with siliceous aggregate, low water/cement ratios, and steel fibers produces better overall thermal properties. The results of literature review and laboratory testing are used for numerical simulation to evaluate the impact of concrete thermal property variability on TES capabilities. The TES module consists of the heat exchanger and surrounding concrete as the storage media. Both idealized cases without heat loss and realistic cases with insulation and heat losses are considered. Furthermore, the result shows that conventional concrete mixes can be tailored to decrease the module charge/discharge durations and increase the amount of thermal energy storage.
Free from siting constraints, thermal energy storage (TES) shows promise as an economical alternative to traditional pumped-storage hydropower (PSH) and compressed air energy storage (CAES). As potential thermal energy storage media, many solid particles demonstrate stability over wide temperature ranges which allows for increased sensible energy storage density and is essential in achieving low-cost storage. Silica sand, in the form of a-quartz, is one such candidate. This work presents a brief review of relevant silica thermophysical properties and further investigates the thermal stability of silica particles as a candidate TES media by subjecting them to two different thermal campaigns: (1) a 500-hour thermal treatment at 1200°C under varied atmospheres; and (2) cycling 25, 50, and 100 times between 300°C and 1200°C. For both campaigns, particle stability is examined by means of pre- and post-treatment Mie scattering. An additional XRD analysis is conducted for the 500-hour treatment in air. Results indicate limited changes in both particle distribution and crystallographic structure which is promising for the application as solid particle media for thermal energy storage.
Parabolic dish solar concentrator cluster concepts are explored, with attention given to thermal storage systems coupled to Stirling and Brayton cycle power conversion devices. Sensible heat storage involving molten salt (NaOH), liquid sodium, and solid cordierite bricks are considered for 1500 F thermal storage systems. Latent heat storage with NaF-MgF2 phase change materials are explored in terms of passive, active, and direct contact designs. Comparisons are made of the effectiveness of thermal storage relative to redox, Na-S, Zn-Cl, and Zn-Br battery storage systems. Molten lead trickling down through a phase change eutectic, the NaF-MgF2, formed the direct contact system. Heat transport in all systems is effected through Inconel pipes. Using a cost goal of 120-150 mills/kWh as the controlling parameter, sensible heat systems with molten salts transport with either Stirling or Brayton engines, or latent heat systems with Stirling engines, and latent heat-Brayton engine with direct contact were favored in the analyses. Battery storage systems, however, offered the most flexibility of applications.
A material called Thermkeep, developed as a low-cost method for the storage of thermal energy for solar electric power generating systems is discussed. The storage device consists of an insulated cylinder containing Thermkeep in which coiled tubular heat exchangers are immersed. A one-tenth scale model of the design contains 25 heat-exchanger tubes and 1500 kg of Thermkeep. Its instrumentation includes thermocouples to measure internal Thermkeep temperatures, vessel surface, heated shroud surface, and pressure gauges to indicate heat-exchanger pressure drops. The test-circuit design is presented and experimental results are discussed.
Thermal energy storage in oil and gas reservoirs leverages the existing surface and subsurface infrastructure, which can pave the way for economic production of geothermal energy. Existing studies on geothermal energy storage are focused mostly on the use of aquifers with more homogeneous rock and fluid properties. Coupling of heat and fluid flow in a multiphase-multicomponent system, such as an oil reservoir, is imperative especially if existing oil field assets need to be repurposed as required for a sustainable energy transition. The objective is to model the subsurface thermo-hydrological processes associated with reservoir performance and operational sustainability. The model evaluates formation pressure and temperature within the reservoir and at the injection/production wells during multiple charge and discharge cycles. Hot water (approximately 200 degrees C) heated by Concentrating Solar Power (CSP) at high pressure is injected into the existing oil reservoir for storage and produced as thermal energy for power generation, which will be accompanied by enhanced oil recovery. To demonstrate the coupled fluid and heat flow during the injection/production cycle in the subsurface reservoir, TOUGH3 (developed by Berkeley Lab) is used to simulate the thermo-hydrological (TH) processes in a multiphase, multicomponent system. Two well geometries are considered within the reservoir grid: 1) a single-well huff-n-puff system (same well is used for injection and production), and 2) an isolated injection-production well doublet. Seasonal charge and discharge cycling are implemented based on the scheduling specified in the model input file. The model reports pressure, temperature, enthalpy, liquid fluxes, heat fluxes, pore velocities, and changes in porosity & permeability due to temperature and pressure variations during the cyclic Reservoir Thermal Energy Storage (RTES) operations. The results from the simulations can be used to optimize the operational parameters (such as well spacing and injection/production rates) and round-trip efficiency for surface power-plants coupled with thermal energy storage over time. They can also serve as important inputs for levelized cost of storage estimations. The research will help to design and integrate surface renewable energy sources, such as concentrating solar power (CSP), with RTES to help balance out power supply and demand on the grid.
The increasing deployment of non‐dispatchable, intermittent renewable energy generation sources to address climate change is placing pressure upon electrical grids’ ability to match supply with demand. The need to deploy large quantities of long duration energy storage assets is rapidly approaching, and innovative methods of energy storage that are low cost, efficient, safe and environmentally benign are needed urgently. CO 2 ‐based Pumped Thermal Energy Storage (PTES) is a low cost, efficient and environmentally safe energy storage technology. PTES uses an electrically‐driven CO 2 heat pump to charge thermal reservoirs that are later used as resources to generate electricity using a CO 2 heat engine. In this program, Echogen and collaborators refined the design of a utility‐scale CO 2 PTES system and demonstrated key technologies that will be required for successful commercial development in a laboratory‐scale system. Component and system‐level performance was evaluated over multiple charge/discharge cycles, with favorable results. Echogen is continuing to develop and commercialize this technology at utility scale.
The project involved considerable industry participation including General Electric (GE, power cycle analysis), Babcock & Wilcox (B&W), Allied Mineral Products (insulation materials), and Worley-Advisian (system integration). They provided insights on their products or services for component and system designs. The project successfully achieved the project goals of demonstrating technology feasibility for long duration energy storage with a technology path towards 5c/kWh levelized cost of storage. The project has generated four patent applications (one awarded patent and three under review), three published journal papers, a draft book chapter, and five manuscripts under preparation, with several conference papers and numerous presentations including invited talks. An intellectual properties (IP) option agreement has been signed with an U.S. manufacturer, with interests from energy developers. Four related projects with $5.5 million DOE funding support more developments for long duration energy storage and broad industry decarbonization.