BACKGROUND
Several factors limit thermal storage within a building’s mass. Use of Thermal Energy Storage (TES) allows reductions in vapor compression system size and taking advantage of time-of-day or real-time variable electricity rates. From a grid connection type of view, it enables load shifting or shedding, allowing to adjust electrical load as solar and wind fluctuate. TES can be applied to both air-source and ground-source secondary loop equipment. The secondary loop enabling zoning in future projects (e.g., Springer et al. 2012) – which is not possible with planned low GWP replacement refrigerants due to flammability concerns. While high tech, transition tunable, as well as ‘regular’ phase change materials have gained interest which raises concern regarding competitiveness in the market.
The three known issues that hinder thermal energy storage’s widespread adoption are: (1) zero or near zero maintenance requirement for a 12+ years lifetime, (2) space usage for storage system within building increases cost per usable square footage, and (3) return on investment.
SUMMARY OF TECHNOLOGY
OSU researchers propose optimizing performance of TES system by optimizing a tri-fluid, cross-fin conduction heat exchanger. See Figure 1 for an overall example design.
Figure 1
Figure 1 incorporates several optimized processes using a cross-fin conduction in fin-tube heat exchanger.
Figure 2 AC charging mode: condenser fan on, circulating pump on, compressor on, inside fan off.
Figure 3 Cooling from tank (peak periods): condenser fan off, circulating pump on, compressor off, inside fan on.
Figure 3 Unit cooling (non-peak): condenser fan on, inside fan on, circulating pump off, compressor on.
POTENTIAL AREAS OF APPLICATION
MAIN ADVANTAGES
STAGE OF DEVELOPMENT
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