Operating performance of multi‐modular water‐phase change material tanks for emergency cooling in an underground shelter

Abstract

Summary Latent heat thermal energy storage can not only alleviate the mismatch between supply and demand but also improve the performance and dependability of the energy system. Unfortunately, previous research achieves a specific engineering load shifting using a single water‐phase change material (PCM) tank, the volume of which is tailored to the specific cooling or heating load. This paper proposes the concept of multi‐modular water‐PCM tanks (MMWPT), which offer flexibility and are simple to be mass‐produced, as thermal storage in an underground shelter's emergency mode. The thermal inertia of the geothermal energy is used to remain the PCM at solid state at first and to naturally cool the tank once they are melted. The mathematical model is created in MATLAB and validated by experiment with an NMBE of less than ±10% and RMSE of less than 30%. In addition, the MMWPT's thermal performance in various matrixes was investigated in an underground shelter where the peak load occurs suddenly and with low frequency. The result reveals that the ∆Twater in the scenario with matrix form of N (number of tanks in series) × 5 (number of tanks in parallel) is almost four times as that with matrix form of N × 1. By separating the water into five parallel water tanks, the corresponding EDD is 1.27‐1.28 times larger. Changing the N from 1 to 2 and 3 could increase the EDD by 3.0%‐12.5% and 5.9%‐25%, respectively. Three acceptable MMWPT matrixes were presented using the effective discharging duration (EDD) and temperature drop as assessment criteria. Additionally, PCM with a maximum phase change temperature (Titalicpch_PCM) of 19.41°C and a connection matrix of 3 × 4 is recommended when using a single charging cycle or active cooling approach. Otherwise, a Titalicpch_PCM of 22.41°C with a connection matrix of 3 × 5 is advised. This research is planned to give references for using the MMWPT in underground shelters to shift loads.

A methodical approach for the design of thermal energy storage systems in buildings: An eight‐step methodology

“…• Step 3: Prior research has focused on achieving a specified load shifting through a single water-PCM tank, with its volume tailored to meet the necessary cooling or heating load. Zeng et al's 57 proposal for thermal storage in the underground shelter's emergency mode also includes MMWPT, which offers flexibility and is simple to mass-produce. The PCM is first kept in a solid form by geothermal energy, and the tank is naturally cooled after the PCM has melted.…”

“…The phase change plates are spaced 20 mm apart. Step 3: Prior research has focused on achieving a specified load shifting through a single water‐PCM tank, with its volume tailored to meet the necessary cooling or heating load. Zeng et al's 57 proposal for thermal storage in the underground shelter's emergency mode also includes MMWPT, which offers flexibility and is simple to mass‐produce. The PCM is first kept in a solid form by geothermal energy, and the tank is naturally cooled after the PCM has melted. Step 4: The geothermal heat pump system (GHPS) is connected in series with MMWPT to provide cooling for the underground shelter in regular and emergency modes, respectively.…”

Standardised methods for the determination of key performance indicators for thermal energy storage heat exchangers

“…Often, the local PCM temperatures are used to validate numerical results with experimental measurements (e.g., [65,98,104,122,129,130]). In contrast, experimental studies are limited to discrete sensor locations (e.g., [63,64,69,72,83,[87][88][89][90][91][92][93][94][95][96][97][98][99][100][101][102][103][104][108][109][110][111][112][113][114][115][116][117][118]) or global liquid fraction techniques (e.g., [87,101]).…”

“…In numerical studies reporting internal energy as a function of time is commonly done although most studies report latent stored internal energy (e.g., [71,99,104,130]) or total liquid fraction (e.g., [65, 66, 68, 70, 71, 75, 77, 93, 99, 102, 104, 106, 109, 111, 113, 115, 120-122, 124-128, 130-132, 134, 136]) instead of total stored energy (e.g., [75,111,115,134,137,138]). In experimental studies, the total liquid fraction is sometimes reported (e.g., [67,87,101]) however local temperature measurements are far more commonly reported (e.g., [63,64,69,72,76,83,[87][88][89][90][91][92][93][94][95][96][97][98][99][100][101][102][103][105][106][107][108][109][110][111][112][113]…”