District Heating By-Pass Valve Control to Reduce Peak Thermal Demand
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Solution Overview
Problem
District heating networks experience peak thermal demand issues due to prolonged shutdown or attenuation of heating systems in connected buildings, leading to inefficient energy management and increased power plant load.
Innovation Solution
The method involves remotely controlling by-pass valves in the primary water circuit to create a closed loop for pre-heating water during low thermal demand periods, using empirical approaches and thermo-fluid dynamics simulations to adjust energy delivery, thereby reducing the thermal energy required at peak demand times.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If heating systems are shut down or attenuated for prolonged periods, then energy consumption is reduced, but thermal demand peaks occur when systems are restarted
Solution Approach 1:
The system performs preliminary heating of the network water before the actual thermal demand peak occurs. By opening by-pass valves in advance, hot water is circulated through the network to pre-heat the water in the pipes and heat exchangers, so that when heating systems are restarted, the thermal demand peak is significantly reduced because the network is already warm.
2Power
If by-pass valves are opened to pre-heat network water, then thermal demand peak is reduced, but thermal energy usage increases
Solution Approach 1:
The system changes operational parameters by controlling the timing and degree of by-pass valve opening. Instead of always operating at full capacity or completely shutting down, the system adjusts the by-pass flow rate and duration based on predicted thermal demand patterns, optimizing the balance between pre-heating benefits and energy consumption.
Solution Approach 2:
The control system uses feedback from temperature sensors and flow meters to monitor the actual state of the network. This information is fed back to the controller, which adjusts by-pass valve positions and pump speeds in real-time to achieve optimal pre-heating while minimizing unnecessary energy consumption. The system learns from historical data to improve its predictions and control strategies.
3Speed
If water is circulated in primary pipes to pre-heat, then network is ready to react to thermal peaks faster, but energy consumption during low demand increases
Solution Approach 1:
Instead of continuous circulation, the system uses periodic or intermittent circulation of hot water through the network during low-demand periods. The by-pass valves are opened at specific intervals or for specific durations to achieve sufficient pre-heating, then closed to minimize energy consumption. This periodic action maintains network readiness while reducing continuous energy loss.
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 reduces the maximum power peak by up to 25% and ensures thermal comfort by pre-heating the network, allowing hot water to reach buildings faster, while maintaining a balance in thermal energy usage and primary energy consumption.
Implementation Method 1
the water circulating in the closed circuit is pre-heated in order to accumulate thermal energy useful for the next time interval in which the thermal request of the plant increases
Implementation Method 2
to circulate the water in the primary pipes and therefore heat up in preparation for the thermal demand
Data Source
Figure 1a
Figure 1b
Figure 2
AI summary
A method of controlling a by-pass valve of a district heating grid or network to provide thermal power to at least one user, includes the steps of: Supplying a delivery pipe (2) with hot water at a temperature T delivered from a power plant (1) when the by-pass valve (6) in correspondence with the users (or in other points of the network) is open so as to defining a closed loop which excludes, at least partially, the heat exchanger (5) of a substation and including the return pipe (3) so that the ΔΤ = Tdelivery - TReturn on ignition decreases; Closing the by-pass valve (6) so that the hot water of the delivery pipe (2) passes through the heat exchanger (5) and the ΔΤ is lower than that of when the feeding step started.