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Pressure sensor for state of charge measurements in latent thermal energy storage (P-SOC).

Number: 3427

Author(s) : RENDALL J., TAMRAPARNI A., SHEN Z., SHRESTHA S.

Summary

In thermal energy storage systems that undergo latent energy change, the state of the charge of the system is a critical piece of information required for optimal operation of the thermal energy battery (i.e., the amount of latent energy left in the thermal battery, such as is 25%, 50%, or 85%). In sensible energy storage, inexpensive thermocouples are often used but do not describe the latent energy change well because the energy transfer happens at a constant temperature. The state of charge (SOC) measurement technique developed in this paper uses the well-known physics principle of Pv = nRT by measuring the pressure changes in an airtight tank outfitted with an expansion vessel. The method can be applied to determine the latent thermal energy storage SOC for phase change material (PCM) in thermal storage applications. This paper first outlines derivation of the mathematics for a simple system without an expansion vessel. The paper next introduces the experimental apparatus and heat loss experiment that quantifies the effect of ambient temperatures on SOC experiments. The results indicate that the model is correct for the working principle of the sensor and notes the linear relationship between the system pressure and the SOC of the PCM. The low cost of pressure sensors (<$200) when compared with the cost of high-accuracy flow meters (>$1,000) and temperature sensors (>$50) that use energy balance methods per local measurement suggests this sensor is an economical way to measure SOC globally and is the new state-of-the-art sensor for SOC determination. Furthermore, energy based SOC measurement have increasing uncertainty for two reasons, as they leave the initial condition of a known temperature in the liquid or solid state and during periods of partial charge the heat loss or gained from ambient is often significant during periods of low use or system downtime.

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  • Original title: Pressure sensor for state of charge measurements in latent thermal energy storage (P-SOC).
  • Record ID : 30032933
  • Languages: English
  • Source: 2024 Purdue Conferences. 8th International High Performance Buildings Conference at Purdue.
  • Publication date: 2024/07/15

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