A student at the National University of Science and Technology (NUST) has developed an innovative thermal energy storage system that could offer Zimbabwean industries a cost-effective and environmentally friendly alternative to conventional battery technologies.
Phakamile Mlala, a third-year Electronics Engineering student, designed a granite-based thermal battery that stores heat rather than electricity. Constructed primarily from steel and locally available granite rock, the system is capable of retaining and releasing thermal energy for industrial applications over an estimated lifespan of between 20 and 30 years.
The innovation seeks to address two major challenges associated with conventional lithium-ion batteries: their limited lifespan in industrial environments and the high costs associated with their disposal.
While lithium batteries used in domestic solar systems can typically last between three and four years, their lifespan is significantly reduced in industrial settings where they undergo frequent charging and discharging cycles. In some cases, industrial batteries may require replacement after just six to eight months of intensive use.
Beyond replacement costs, the disposal of lithium batteries presents an additional challenge. Because they contain hazardous materials and chemicals, safe disposal often requires specialised processes that can be costly and environmentally burdensome.
Mlala's thermal battery offers a potential solution to both problems. With an expected operational life of up to three decades, the system dramatically reduces the need for frequent replacements. Furthermore, because granite is a naturally occurring rock and poses no environmental hazard, disposal costs at the end of the battery's life are effectively eliminated.
The technology operates by drawing ambient air into the system using a fan. The air is circulated through heated granite, where thermal energy is stored. As the air passes through the heated rock, it absorbs the stored heat before being released for industrial use.
The resulting hot air can be applied across a range of sectors, including food processing, textile manufacturing and agricultural production. The current focus of the project is tobacco curing, a process that requires a consistent and reliable heat source. Given Zimbabwe's status as one of Africa's leading tobacco producers, the technology could provide significant value to the industry.
The battery can be charged through multiple energy sources. Solar power offers a renewable charging option, while industries can also take advantage of lower off-peak electricity tariffs by storing heat during the night and releasing it during the day when demand and energy costs are higher.
Looking ahead, Mlala envisions the technology being used to capture and store waste heat generated by factories, industrial machinery, generators and even emerging artificial intelligence data centres, thereby improving overall energy efficiency.
A working prototype has already been developed and incorporates advanced monitoring and control systems. Temperature sensors continuously track thermal conditions within the battery, while a control mechanism regulates output temperatures by blending heated air with cooler ambient air to meet specific operational requirements.
The innovation comes at a time when many Zimbabwean industries and small-scale enterprises continue to grapple with unreliable electricity supplies and rising energy costs. Conventional heating methods, including diesel-powered and electric heating systems, remain expensive and often unsustainable.
By harnessing locally available materials and combining them with intelligent monitoring technologies, the granite battery presents a practical solution for industrial energy storage and thermal management.
The project also reflects the growing role of innovation and home-grown research in addressing national development challenges. By integrating simple engineering principles with data-driven control systems, the technology aligns with the objectives of the Fourth Industrial Revolution while remaining accessible and affordable for local industry.
For Zimbabwe, Mlala's invention demonstrates how locally developed technologies can leverage abundant natural resources to deliver sustainable, low-cost solutions with the potential to transform industrial operations and support economic growth.