CO2 Heat Accumulator Cycle for Decentralized Renewable Energy Storage
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Solution Overview
Problem
Current energy storage methods for renewable energy sources like solar and wind energy are inefficient and uneconomical, leading to unpredictable energy supply and reliance on conventional fossil fuel-based systems for load balancing, as they cannot store energy locally and release it on demand as electrical or thermal energy effectively.
Innovation Solution
A reversible thermal cycle using a heat accumulator driven by excess energy conversion into electrical energy, employing a heat pump process with carbon dioxide as the working medium, allowing for decentralized and efficient storage and release of energy as electrical or thermal energy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If chemical batteries, water electrolysis, compressed air storage are used to store renewable energy, then energy can be stored and released, but the performance and economy are insufficient compared to conventional energy supply
Solution Approach 1:
The patent changes the physical state parameters of the working fluid (carbon dioxide) between supercritical and gaseous phases to enable efficient energy storage and retrieval. By controlling temperature and pressure parameters, the system achieves high-efficiency thermal energy storage that overcomes the limitations of chemical batteries and compressed air storage.
Solution Approach 2:
The patent utilizes phase transitions of carbon dioxide between supercritical and gaseous states to store and release thermal energy. During charging, the working fluid transitions to supercritical state and stores thermal energy; during discharging, it transitions back to gaseous state and releases energy to drive the turbine generator.
2Reliability
If conventional energy supply with large fuel deposits and central power plants is used, then electrical energy can be supplied reliably, but the system is not decentralized and cannot store energy locally
Solution Approach 1:
The patent segments the energy storage system into modular components (heat exchangers, turbines, compressors) that can be deployed at decentralized locations near renewable energy sources. This allows local energy storage and utilization without relying on large central power plants and transmission networks.
Solution Approach 2:
The patent introduces a thermal energy storage intermediary system using carbon dioxide as the working fluid. This intermediary converts electrical energy from renewable sources into thermal energy for storage, and then converts stored thermal energy back to electrical energy when needed, enabling decentralized energy management.
3Productivity
If solar and wind energy are generated decentralized but not in line with demand, then renewable energy can be utilized, but the unpredictability must be compensated by reserve capacities
Solution Approach 1:
The patent implements preliminary action by storing thermal energy in advance when renewable energy is abundant. The system charges the thermal storage during periods of excess solar or wind energy generation, preparing stored energy for later use when demand exceeds renewable supply, thereby eliminating the need for fossil fuel reserve capacities.
Solution Approach 2:
The patent ensures continuity of useful action by maintaining a continuous cycle of energy conversion and storage. The thermal energy storage system operates continuously to balance supply and demand, converting renewable energy to thermal storage during surplus periods and converting thermal storage back to electrical energy during deficit periods, eliminating energy waste.
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
Enables a time-unlimited, needs-based, and economically competitive supply of electrical and thermal energy from renewable sources, achieving high energy efficiency and reducing reliance on fossil fuels, with a heat pump index of more than 4:1 and a useful energy efficiency of 152% over the entire cycle.
Implementation Method 1
the working medium of the cycle process evaporating below its critical pressure in a process stage of evaporation by supplying ambient heat
Implementation Method 2
before being compressed to supercritical pressure
Implementation Method 3
in which case it releases part of its thermal energy above the critical temperature recuperatively and in an approximately isobaric manner to a heat transfer medium that Heat itself stores
Implementation Method 4
is condensed in a second cooling stage recuperatively in parallel material flows under supercritical pressure
Implementation Method 5
the gaseous working medium of the cyclic process is completely condensed by dissipating its heat of condensation to the environment
Implementation Method 6
raised in this supercritical state in a first stage in parallel material flows vaporized and overheated by the recuperative supply of thermal energy from the storage
Implementation Method 7
is expanded to condensation pressure and up to near the upper temperature of the first stage for evaporation and overheating
Implementation Method 8
in the discharge cycle the cyclic process is operated as a power process, with or without decoupling of thermal energy for the generation of electrical energy
Data Source
Figure 1
AI summary
The invention relates to a method for storing and recovering energy, in particular solar and wind energy that is converted into electric energy and is used to charge and discharge a heat accumulator with the aid of a circulatory process, which operates as a thermal pump process that absorbs local ambient heat and raises the temperature level of the latter, thus thermally charging the heat accumulator. The working fluid of the circulatory process, after evaporation by the ambient heat below its critical temperature, is recuperatively pre-heated to above its critical temperature by the addition of internal process heat, prior to compression at supercritical pressure, before releasing part of its thermal energy, which is latent above its critical temperature, after compression in a first cooling stage to a heat transfer medium. In a second, parallel cooling stage the thermal energy is then recuperatively transferred, prior to being relaxed to an evaporation pressure that lies close to the temperaure level of evaporation by condensation, back to said fluid in order to reheat itself prior to compression and to the heat transfer medium via separate mass fluxes.