Thermoelectric Energy Storage System With Dual Thermal Baths

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Solution Overview

Problem

Current thermoelectric energy storage systems have limited round-trip efficiency due to the second law of thermodynamics, coefficient of performance, and temperature differences, leading to significant energy loss during charging and discharging cycles.

Innovation Solution

A thermoelectric energy storage system with a working fluid circuit and thermal storage medium circuit, utilizing two separate thermal baths with minimized temperature difference during charging and maximized difference during discharging, along with cooling and heating devices to adjust storage tank temperatures, and operating sections transcritically to enhance efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If a single thermal bath is used for both charging and discharging cycles, then the system structure is simple, but the round-trip efficiency is limited due to temperature differences

Engineering Contradiction:

Improveround-trip efficiencyVSAvoidsystem structure

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

The single thermal bath is segmented into two separate thermal baths: a first thermal bath for the charging cycle and a second thermal bath for the discharging cycle. This segmentation allows independent temperature optimization for each cycle, improving round-trip efficiency by minimizing temperature differences during heat transfer operations.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The temperatures of the thermal baths are optimized as separate parameters: the first thermal bath temperature is set close to the hot storage tank temperature during charging, while the second thermal bath temperature is set to maximize the temperature difference during discharging. This parameter optimization resolves the efficiency limitation.

Inventive Principle:

Principle #35Parameter changes

2Productivity

If the temperature difference between thermal bath and hot storage tank is maximized, then heat transfer rate increases, but the coefficient of performance declines and energy loss increases

Engineering Contradiction:

Improveheat transfer rateVSAvoidcoefficient of performance

Core Design Contradiction:

ProductivityVSLoss of energy

Solution Approach 1:

Different temperature difference strategies are applied locally to different cycles: during charging, the temperature difference is minimized to maximize COP, while during discharging, the temperature difference is maximized to maximize heat transfer rate and energy recovery. This local optimization resolves the contradiction between productivity and energy loss.

Inventive Principle:

Principle #3Local quality

3Ease of manufacture

If resistor heaters are used to provide thermal energy, then the system is simple, but the round-trip efficiency is approximately 40%

Engineering Contradiction:

Improvesystem simplicityVSAvoidround-trip efficiency

Core Design Contradiction:

Ease of manufactureVSLoss of energy

Solution Approach 1:

The resistor heating system is replaced with a heat pump-based charging cycle that uses a first thermal bath and minimizes temperature difference during heat transfer. This substitution improves round-trip efficiency by utilizing thermodynamic cycles rather than direct resistive heating, while maintaining system simplicity through standardized heat pump technology.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach increases the round-trip efficiency and reduces system costs by minimizing electricity input during charging and maximizing energy recovery during discharging, while maintaining cost-effectiveness.

Implementation Method 1

During a charging cycle, the second heat exchanger is in connection with a first thermal bath, and the temperature difference between the first thermal bath and a hot storage tank is minimized

Methodology Applied

Scientific EffectHeat transfer: Conduction (thermal)

Implementation Method 2

During a discharging cycle, the second heat exchanger is in connection with a second thermal bath, and the temperature difference between the second thermal bath and the hot storage tank is maximized

Methodology Applied

Scientific EffectHeat transfer: Conduction (thermal)

Implementation Method 3

Thermal energy can be stored in the form of sensible heat via a change in temperature

Methodology Applied

Scientific EffectSensible heat storage: Thermal Energy Storage

Data Source

PatentEP2241737B1Thermoelectric energy storage system having two thermal baths and method for storing thermoelectric energy

Publication Date: 2015.06.03 ABB RES LTD

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AI summary

A system and method for storing and retrieving energy in a thermoelectric energy storage system is described. The thermoelectric energy storage system comprises a working fluid which is circulated through a first and second heat exchanger (18, 14, 30), and a thermal storage medium which is circulated through the first heat exchanger (18). The second heat exchanger (14, 30) is in connection with a first thermal bath (20) during a charging cycle and with a second thermal bath (34) during a discharging cycle. In this way roundtrip efficiency is improved through minimizing the temperature difference between the first thermal bath (20) and the hot storage tank (24) during charging, and maximizing the temperature difference between the second thermal bath (34) and the hot storage tank (24) during discharging.