Point-of-Use Ozone Heating for Legionella-Safe Hot Water
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Solution Overview
Problem
Existing water heating systems using large thermal storage tanks are prone to Legionella proliferation due to stagnant water at temperatures suitable for bacterial growth, making it difficult to prevent transmission without frequent testing and ozone injection at central locations, which is ineffective at points of use.
Innovation Solution
A compact under-sink heating system with an ozone generation and control system that sanitizes water at the point of use, using an ozone demand indicator and generator to ensure ozone is only produced when needed, reducing the risk of Legionella proliferation without requiring water testing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a large thermal storage tank is used to meet hot water demands, then the heating capacity is improved, but the risk of Legionella proliferation increases due to stagnant water at temperatures suitable for bacterial growth
Solution Approach 1:
The system divides the water heating function into two separate components: a compact instantaneous heating unit (heat pump or electric heater) and a point-of-use sanitization device (ozone generator). This eliminates the need for a large thermal storage tank while providing both heating capacity and Legionella prevention through localized ozone injection at the faucet.
Solution Approach 2:
Ozone is introduced as an intermediary substance to sanitize water at the point of use. The ozone generator injects ozone into the water stream, which kills Legionella bacteria without requiring a large storage tank, thus resolving the contradiction between heating capacity and bacterial proliferation risk.
2Area of stationary object
If ozone injection is implemented at a central location in the water supply network, then the sanitization coverage is improved, but the effectiveness decreases due to re-contamination at points of use
Solution Approach 1:
Instead of injecting ozone centrally and relying on it to reach points of use (top-down approach), the system inverts the approach by placing the ozone generator directly at the point of use (bottom-up approach). This ensures ozone is applied exactly where needed, preventing re-contamination and maintaining sanitization effectiveness.
Solution Approach 2:
The sanitization function is localized to the specific point of use through a compact ozone generator integrated into the faucet assembly. This local quality approach ensures that each faucet receives targeted ozone treatment, making the sanitization effective regardless of the central water supply conditions.
3Measurement precision
If frequent water testing is conducted to detect Legionella, then the detection accuracy is improved, but the operational complexity and cost increase
Solution Approach 1:
The system applies preliminary sanitization action by continuously or periodically injecting ozone into the water at the point of use, preventing Legionella proliferation before it can occur. This eliminates the need for frequent testing to detect Legionella, as the preventive measure ensures the water remains safe.
Solution Approach 2:
The water heating and sanitization system serves itself by automatically detecting water demand through the flow sensor and activating the heat pump/electric heater and ozone generator accordingly. This self-service operation eliminates the need for manual testing and monitoring, reducing operational complexity.
4Volume of moving object
If a compact under-sink heating system is used instead of a large tank, then the space requirement is reduced, but the ability to meet sustained hot water demands may be compromised
Solution Approach 1:
The system replaces the mechanical thermal storage approach (large tank) with an instantaneous heating approach using a heat pump or electric heater combined with a flow sensor. This substitution allows the compact system to meet sustained hot water demands by continuously heating water as it flows, eliminating the need for large storage volume while maintaining productivity.
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
The system effectively sanitizes water at the point of use, reducing the risk of Legionella transmission by utilizing ozone only when water is not in use, thereby preventing re-contamination and maintaining water quality without the need for frequent testing.
Implementation Method 1
a heat pump system having a refrigerant path, at least a portion of which is in thermal communication with the water tank volume such that heat transfers from a refrigerant to the water tank volume
Implementation Method 2
another portion of the refrigerant path includes an evaporator in the housing. The fan is within the housing and may further be within a second housing
Implementation Method 3
an ozone generator configured to be disposed no more than about 72 inches upstream of the point of use on a fluid conductor supplying the water flow at the point of use, wherein ozone generated by the ozone generator is configured to be disposed in the water flow to sanitize the water flow
Implementation Method 4
Supplemental electric heating elements may also be employed to aid fossil fuel-free domestic water heating systems in meeting heating demands
Data Source
AI summary
A sanitizing system for sanitizing a water flow at a point of use, the sanitizing system including an ozone demand indicator configured for determining the existence of a demand for ozone in the water flow; an ozone generator configured to be disposed no more than about 72 inches upstream of the point of use on a fluid conductor supplying the water flow at the point of use, wherein ozone generated by the ozone generator is configured to be disposed in the water flow to sanitize the water flow; and a controller operable to control the ozone demand indicator and the ozone generator responsive to the ozone demand indicator, wherein the controller is configured to cause the ozone generator to start generating ozone upon receiving an indication from the ozone demand indicator that the demand for ozone exists.