LAB-BASED ASSESSMENT OF SAND AS A POTENTIAL THERMAL ENERGY STORAGE MEDIUM

Shreyas K Bapu (2106281)Supervisor: Dr. Samia Cunningham

Background

The net Solar Energy reaching the Earth’s Surface in a year exceeds the total human energy consumption by 20,000 times. Since,this is not completely accessible due to natural factors like day/night cycle, geographical location & Atmospheric absorption; the most attractive solution to storing this energy would be Thermal Energy Storage (TES).

ObjectiveŸThe capacity of Sand to behave like a potential Thermal Energy

Storage medium is analysed by designing and modeling a lab-scale setup.

ŸVarious physical properties of sand such as thermal conductivity, heat transfer and temperature-depth relations shall be studied under a variety of lab-generated conditions.

MethodŸThe sand is subjected to a light source having spectral

characteristics similar to the Black Body spectrum of the Sun, and its behaviour is analysed under the lab conditions.

ŸThe thermal properties of the sand are evaluated at various depths and temperatures using Excel Spreadsheets linked to Statistical Software such as Rstudio.

Figure 1: Why sand?

Project Description

Ÿ- Qualitative Analysis used to select Materials for experimentŸ- CAD Model generated for Sand Container

Figure 2 : Frontal & Sectional CAD View of Setup

Materials:- Plexiglass Container with perforations at 2 cm separation- 2 light source - Quartz-Tungsten Halogen-Everspring Sa-122 500 W - Metal Halide - OSRAM PowerStar 400 W/D- DrDaq Data Logger + Temperature Probes

Figure 3: TES system experimental setup

ResultsThe data is obtained for 2 different light sources and multiple depths. They are coherent and can be expressed using raw graphical data & Statistical Software (R program + R Studio)ŸRaw Graphical Data: The variation in temperature for each sample

produces a set of heating and cooling graphs.

Figure 4: Average heating/ cooling

Ÿ Statistical Software Analysis: The statistical analysis is done using the R Studio tool. Pearson’s Product-Momentum correlation shows a Negative Correlation found between temperature & depth independent of Heating & Cooling characteristics.

Figure 5: General trend- temperature v/s depth

The average Temperature Characteristics for the light sources show a negative correlation between temperature & depth as well.

Figure 6: Average temperature characteristics( box & scatter plot)

Conclusion

There is a definite negative correlation between Temperature & Depth, as seen for both light sources. The surface has a higher ‘rate of temperature variation’ compared to the sub surface. It should be noted that these results are with respect to laboratory conditions and can’t be applied to external environments.

References

ŸA. Gil, M. Medrano, I. Martorell, A. Lázaro, P. Dolado, B. Zalba, and L. F. Cabeza, “State of the art on high temperature thermal energy storage for power generation. Part 1—Concepts, materials and modellization,” Renew. Sustain. Energy Rev., vol. 14, no. 1, pp. 31–55, Jan. 2010.

ŸM. C. Golob, “Convective heat transfer performance of sand for thermal energy storage.” Georgia Institute of Technology.