HVAC Thermal Energy Storage Control for Peak Load Shifting
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Solution Overview
Problem
HVAC systems face inefficiencies in heating and cooling capacity per unit of power consumption, leading to high operating costs and size constraints, particularly in managing thermal loads and peak demand.
Innovation Solution
Incorporating a thermal energy storage device (TESD) with a control system that manages refrigerant flow and charging/discharging thermal energy between a condenser and evaporator to optimize HVAC system performance, including the use of thermal energy storage media like water or eutectic materials, and controlling compressor and expansion device operations to enhance energy efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a thermal energy storage device is added to the HVAC system, then energy efficiency ratio (EER) and coefficient of performance (COP) are improved, but device complexity increases
Solution Approach 1:
The thermal energy storage device is integrated into the existing HVAC system by combining it with the refrigerant circulation loop. The TESD is positioned between the condenser and evaporator, allowing it to function as part of the existing refrigeration cycle without requiring a completely separate system. This merging approach improves energy efficiency while limiting the increase in complexity.
Solution Approach 2:
The thermal energy storage device serves multiple functions within the HVAC system: it stores thermal energy during off-peak periods, releases thermal energy during peak demand periods, and can operate in conjunction with the refrigerant cycle to provide both cooling and heating modes. This multi-functionality justifies the added complexity by providing diverse operational capabilities from a single integrated component.
2Loss of energy
If a thermal energy storage device is added to the HVAC system, then operating costs are reduced, but device complexity increases
Solution Approach 1:
The thermal energy storage device accumulates thermal energy during off-peak periods when electricity rates are lower, before the period of high demand. By pre-storing thermal energy when power costs are reduced, the system can meet peak demand without incurring high operating costs, thereby reducing overall operating expenses despite the added system complexity.
3Adaptability or versatility
If the HVAC system is designed for higher thermal load capacity, then thermal load management flexibility is improved, but unit size increases
Solution Approach 1:
The thermal energy storage device adds a temporal dimension to thermal load management by enabling energy to be stored and released across different time periods. Instead of simply increasing the size of the cooling capacity, the system uses the TESD to provide load management flexibility by shifting thermal energy delivery from off-peak to peak periods, achieving adaptability without proportionally increasing unit size.
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 improves energy efficiency ratios (EER) and coefficient of performance (COP), reduces operating costs, allows for flexible thermal load management, and enables unit size reduction by optimizing refrigerant flow and thermal energy storage.
Implementation Method 1
a fluid transitioning from gas to liquid releases heat, while a fluid transitioning from liquid to gas absorbs heat
Implementation Method 2
The refrigerant circulating between the indoor and outdoor heat exchangers transitioning between phases along the way absorbs heat from one location and releases it to the other
Implementation Method 3
a fluid transitioning from gas to liquid releases heat
Implementation Method 4
the refrigerant circulating between the indoor and outdoor heat exchangers transitioning between phases along the way absorbs heat from one location and releases it to the other
Implementation Method 5
TESs shift cooling energy use to non-peak times, thus shifting the load on the HVAC system. They chill storage media such as water, ice, or a phase-change material during periods of low cooling demand
Implementation Method 6
The storage medium is generally water, ice, or a phase-change material (sometimes called a eutectic salt)
Data Source
AI summary
A heating, ventilation, and air-conditioning (“HVAC”) system for use with a refrigerant. The HVAC system includes a compressor, a condenser, an evaporator expansion device, and an evaporator. The HVAC system also includes a thermal energy storage device (“TESD”) including thermal energy storage media in line between the condenser and evaporator. A control system is programmed to operate the compressor and the evaporator expansion device to control the refrigerant flow through the HVAC system. The control system is also programmed to control the refrigerant flow through the TESD to charge the TESD with thermal energy. The control system is also programmed to control the refrigerant flow through the evaporator expansion device and evaporator and discharge the thermal energy from the charged TESD to improve the performance of the HVAC system.