Combi Heating System Control to Reduce Heat Pump On-Off Cycling
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Solution Overview
Problem
Heat pumps used in combi heating systems experience inefficiencies due to frequent on-off cycles, particularly for thermally driven types like sorption and heat engines, which affect their effectiveness and efficiency.
Innovation Solution
A combi heating system with a control system that manages operation modes (space heating, water heating, and combination modes) to minimize on-off cycles by continuing heat pump operation after demand termination, redirecting loop heat energy, and optimizing blower and pump operations based on temperature sensors and timers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the heat pump is cycled on and off frequently to match heating demand, then the system can respond quickly to temperature changes, but the heat pump effectiveness and efficiency deteriorate
Solution Approach 1:
The control system performs preliminary actions by continuing to operate the heat pump and redirecting loop heat energy to the AHU or IST after the thermostat call terminates. This anticipatory action prevents immediate shutdown, maintaining heat pump effectiveness while still responding to temperature changes. The system prepares for future demand by keeping components warm and operational.
Solution Approach 2:
The invention maintains continuity of useful action by extending heat pump operation beyond the thermostat call termination. The control logic keeps the heat pump running for a predetermined time or until specific temperature conditions are met, ensuring continuous heat production rather than intermittent cycling. This continuity preserves heat pump efficiency while meeting heating demands.
2Reliability
If the heat pump operation is extended beyond demand termination, then the on-off cycle frequency is reduced and efficiency is improved, but the risk of overheating or energy waste increases
Solution Approach 1:
The control system uses feedback from temperature sensors and thermostat signals to regulate extended heat pump operation. The control logic monitors loop temperature, AHU temperature, and IST temperature to determine when to continue or stop operation. This feedback mechanism ensures the heat pump runs long enough to maintain efficiency but stops before causing energy waste or overheating.
Solution Approach 2:
The system changes operational parameters dynamically by adjusting the duration and conditions of extended heat pump operation based on multiple factors including outdoor temperature, indoor temperature differential, and heating demand patterns. These parameter changes optimize the balance between maintaining heat pump efficiency and preventing energy waste, adapting to different operating conditions.
3Loss of energy
If multiple components (AHU, IST, heat pump) are coordinated to share heat energy, then overall system efficiency is improved, but the control system complexity increases
Solution Approach 1:
The invention merges the control of multiple components (heat pump, AHU, IST) into a unified control system that manages heat energy distribution across all components. By combining these functions under single control logic, the system coordinates heat sharing between components to improve overall efficiency. The control system determines when to redirect loop heat to the AHU or IST based on their respective needs, creating a synergistic energy management approach.
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
Enhances system efficiency by reducing the frequency of on-off cycles, maximizing heat pump operation duration, and utilizing residual heat effectively, thereby improving overall heating system performance.
Implementation Method 1
a heat pump moves energy from a low temperature source to a high temperature sink
Implementation Method 2
a hydronic loop configured to direct hydronic flow between the hydronic heat pump, the IST and the AHU
Data Source
AI summary
A system that includes a hydronic heat pump; an indirect storage tank (IST) configured to heat potable water stored therein; an air handler unit (AHU) configured to heat an enclosure; a hydronic loop configured to direct hydronic flow between the hydronic heat pump, the IST and the AHU; a temperature control system comprising a space heating thermostat configured to control an air temperature in the enclosure and one or more IST thermostats configured to control a temperature of the potable water in the IST; and a control system comprising control logic configured to control operation of components of the combi heating system among a plurality of predetermined operating modes, in response to an operating call from the temperature control system.