Elemental Sulfur as a Thermal Energy Storage Medium
Engineering Technology Department, College of Engineering
Student Researchers: Andrew Liu, Evan Fullerton, Saul Ugarte
Advisor: Dr. Reza Baghaei Lakeh
Abstract
The largest portion of the world’s ever-increasing energy demands are
currently being met by fossil fuels, which are limited resources and damage
the environment. Being able to meet increasing energy demands in a
sustainable manner has become a global initiative. Efforts are being taken to
increase the feasibility of renewable energy sources to address this issue.
Solar energy is a promising energy source; however, it is an intermittent
source due to day/night cycles and weather patterns. Solar thermal energy
storage increases the dispatchability of solar energy by allowing a thermal
power plant to operate at night, or during unfavorable weather conditions.
Research is being conducted to determine a storage medium that can reach
and maintain high temperatures, ideally one that is inexpensive, is relatively
abundant, has a low vapor pressure, and does not degrade.
Compared with other material, the combination of low vapor pressure, low
cost, and availability makes elemental sulfur a great candidate for thermal
energy storage. In this project, elemental sulfur is tested in designed storage
tubes to investigate the feasibility of using elemental sulfur as a thermal
storage medium. This testing will be conducted in a high temperature oven
with temperature and pressure probes in the sulfur container. Several cycles
of heating and cooling is being conducted to simulate real-world conditions of
a thermal energy storage system.
Experimental Setup
Validation of Results
Conclusion
• The experimental setup consists of 20 k-type thermocouples.
• The thermocouples measure the internal and external temperature
of the single-element storage tubes.
• The accuracy of the measure temperatures are confirmed by doing
a pilot experiment “ice-bucket challenge”
Ice-bucket Experiment
Figure 2: Laboratory setup including High Temperature Oven, Data Acquisition Device,
and lab computer
In this experiment the fabricated thermocouples are calibrated and
tested. The k-type thermocouple readings were compared with the
theory of transient natural convection.
The current effort at Cal Poly Pomona is a part of a collaborative
project with University of California Los Angeles (UCLA). The project is an
excellent opportunity to gain valuable insight in the engineering fields of
heat transfer, thermodynamics, materials science, as well as renewable
energy, and an opportunity to demonstrate our knowledge in the
aforementioned fields as engineers. This project provides opportunities to
work with other students and faculty from other institutions, as well as
experience working in industry. Additionally this research may prove
invaluable to the future of thermal energy storage, making renewable
energy a more competitive source of energy.
• The thermocouples were used to measure the surface temperature
of a very small sphere (D = 5 mm).
• The spheres were placed in an ice-bucket for 30 minutes to ensure
the temperature of the sphere is at 0 °C.
• The Data Acquisition system was utilized to capture the temperature
of the sphere as a function of time.
• The sphere was then removed from the ice-bucket and was
exposed to room temperature. The variations of surface temperature
of the sphere was recorded.
• The variation of temperature of the sphere was then compared with
transient conduction theory and perfect agreement was observed.
Figure 3: Thermal Energy Storage System, Left: Single-element storage tube; right:
storage tube bank
Figure 1 - Plot depicting vapor pressure of sulfur compared to other materials
Objectives
 Elemental sulfur will be tested in a single-tube configuration to moderateand high-temperature condition. The allotropic benefits of sulfur will be
tested. Single tube will be designed based on inputs from material
compatibility study for appropriate linings, etc.
 Containment materials and linings will be identified based on material
compatibility analyses for elemental sulfur and containment material
candidates for different temperature ranges. Corrosion rates will be
measured for moderate- and high-temperature conditions.
Figure 5: Thermal testing of a modular Thermal Energy Storage system. In the next phases
of the project, lab-scale and pilot-scale demonstration of the system will be performed at
UCLA and Cal Poly Pomona
Figure 4: Computational model of the Thermal Energy Storage tank
Figure 4: The agreement between experimental results of temperature
measurement versus the predicted values by transient conduction
theory.