Arrangement and a method for storing thermal energy in the ground
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Solution Overview
Problem
Current methods for storing thermal energy are inefficient and costly, with limitations in long-term storage and high-temperature energy retrieval.
Innovation Solution
A circuit with a working fluid and electrical heating element is distributed throughout the ground to efficiently store thermal energy, allowing for high-temperature storage and retrieval without pressurization of the working fluid.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If electrical heating element is used to heat the ground directly, then energy conversion efficiency is improved, but temperature control becomes more difficult
Solution Approach 1:
The patent applies local quality by creating distinct thermal zones: a high-temperature central zone around the electrical heating element and lower-temperature peripheral zones where pipes are located. This allows the heating element to operate at very high temperatures for efficient energy conversion while the working fluid in pipes operates at moderate temperatures for practical energy extraction.
Solution Approach 2:
The ground/bedrock acts as an intermediary thermal medium between the electrical heating element and the working fluid in pipes. The heating element heats the ground, which then transfers heat to the working fluid through thermal conduction, enabling temperature control and decoupling the high-temperature source from the moderate-temperature extraction point.
2Use of energy by moving object
If pipes are placed close to electrical heating element, then heat exchange efficiency is improved, but working fluid temperature exceeds maximum allowed temperature
Solution Approach 1:
The patent creates a spatial temperature gradient where the central region around the heating element operates at high temperatures and the peripheral regions where pipes are located operate at lower temperatures. This allows efficient heat exchange while maintaining working fluid temperature within acceptable limits.
Solution Approach 2:
The patent transitions from a one-dimensional heat transfer model (direct contact) to a three-dimensional radial heat transfer model through the ground medium. This dimensional change allows heat to be efficiently transferred through the ground volume while maintaining appropriate temperature gradients and distances.
3Quantity of substance
If ground temperature is increased for higher energy density, then storage capacity is improved, but heat losses to groundwater increase
Solution Approach 1:
The patent converts the potential harm of groundwater contact into a benefit by using groundwater as a thermal barrier. When groundwater approaches the heated zone, it absorbs heat and becomes less dense, rising away from the central high-temperature zone. This creates a natural thermal insulation layer that reduces heat losses while maintaining high energy density in the core storage region.
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 method enables efficient conversion of electrical energy to heat, allowing for long-term storage at high temperatures suitable for district heating, process heating, and electricity generation, while minimizing energy losses.
Implementation Method 1
the electrical heating element is arranged in a channel in the ground to heat the ground for storing thermal energy in the heat storage
Implementation Method 2
each pipe is arranged in a channel in the ground for heat exchange between the working fluid and the ground
Implementation Method 3
heat energy in turn can be stored for long periods at high temperatures in the ground in an efficient way
Data Source
AI summary
An arrangement for storing thermal energy includes a circuit containing a working fluid, where the circuit has a plurality of pipes which pipes are distributed throughout a volume of the ground forming a heat storage. Each pipe is arranged in a channel in the ground for heat exchange between the working fluid and the ground. The arrangement includes an electrical heating element, where the electrical heating element is arranged in a channel in the ground to heat the ground for storing thermal energy in the heat storage. The working fluid is a liquid having a boiling point above 120° C. at atmospheric pressure.