Domestic Hot Water Loop Return Control for Intermittent Heat Recovery
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Solution Overview
Problem
Centralized domestic hot water production systems using intermittent heat sources face challenges in user comfort due to long pipe lengths, leading to delayed hot water delivery and significant heat losses, which result in energy wastage and potential overheating risks.
Innovation Solution
A control method for regulating the domestic loop return, connecting it alternately to a preheating tank and a backup tank based on temperature differences, optimizing energy recovery and reducing overheating risks by ensuring efficient use of intermittent heat sources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the sanitary loop return is directed to the auxiliary tank for heating, then user comfort is quickly achieved with hot water delivery, but heat losses in the loop become very high leading to energy wastage
Solution Approach 1:
The patent introduces a three-way valve as an intermediary device that mediates between the sanitary loop return and two different tanks (preheating tank and auxiliary tank). This valve dynamically directs the loop return to the appropriate tank based on temperature conditions, allowing the system to achieve both quick hot water delivery and reduced heat losses by selecting the optimal destination for the return water
Solution Approach 2:
The system monitors temperature parameters (T_pre of preheating tank, T_ret of loop return, T_aux of auxiliary tank) and changes the routing parameter based on these measurements. When T_pre - T_ret exceeds threshold ΔT_up, the system switches the loop return destination from auxiliary tank to preheating tank, optimizing energy recovery based on temperature differential
2Loss of energy
If the loop return is sent to the preheating tank to recover heat from intermittent sources, then energy savings improve, but the risk of overheating increases
Solution Approach 1:
The system implements feedback control by continuously measuring temperatures in the preheating tank, auxiliary tank, and loop return. The control device uses this feedback information to dynamically adjust the three-way valve positioning, ensuring that heat recovery operations do not push the preheating tank temperature beyond safe thresholds, thus balancing energy savings with overheating prevention
Solution Approach 2:
The system dynamically adjusts the loop return routing based on real-time temperature conditions rather than using a fixed configuration. The three-way valve position changes dynamically in response to temperature measurements, allowing the system to maximize heat recovery when conditions are favorable while preventing overheating when the preheating tank temperature approaches dangerous levels
3Adaptability or versatility
If long pipe lengths are used in centralized systems, then hot water can be delivered to multiple users, but user comfort deteriorates due to delayed hot water delivery and significant heat losses
Solution Approach 1:
The system performs preliminary heating actions by directing loop return water to the preheating tank when temperature differentials indicate favorable conditions for heat recovery. This preliminary action pre-heats the water in the preheating tank using waste heat from the loop return, reducing the energy needed for subsequent heating and minimizing heat losses in the distribution pipes before water reaches users
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 method enhances energy savings by 1% and reduces the frequency of booster tank ignitions, maintaining similar overheating risk levels while improving user comfort and energy efficiency.
Implementation Method 1
The invention relates to the field of systems for producing domestic hot water (DHW) by intermittent heat source (solar thermal, system for recovering waste heat from an industry, etc.)
Implementation Method 2
The booster tank 12 can take different forms: gas boiler, biomass, fuel oil, heat pump, electrical resistance, etc.
Implementation Method 3
The booster tank 12 can take different forms: gas boiler, biomass, fuel oil, heat pump, electrical resistance, etc.
Implementation Method 4
The preheating tank 11 and the booster tank 12 are each connected to a heat exchanger 17, 18 which can be external or internal to the tank
Implementation Method 5
Two types of hydraulic component 5 allow this control: thermostatic mixing valves and motorized three-way valves
Implementation Method 6
The usual control rule for this three-way valve is represented on the picture 3. According to this rule, if the loop return can cool the preheating tank 11 (which will then be able to recover more heat from the intermittent source 20), then the loop return is sent to this tank 11. Otherwise, it is injected into the booster tank 12
Implementation Method 7
the centralized systems 1 are usually equipped with a sanitary loop 13 which ensures a permanent circulation of hot water from the production installation to the draw-off points 2
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
The invention relates to the field of domestic hot water (DHW) production systems using intermittent heat sources (solar thermal, industrial waste heat recovery systems, etc.). It proposes a control method that allows, on the one hand, for the recovery of more intermittent heat with improved efficiency compared to prior art, and on the other hand, for the optimized use of energy stored in the preheating tank. Its application is particularly advantageous in the field of domestic hot water distribution for collective use with a centralized installation.