Solar energy is a promising renewable option to provide energy demands in combination with conventional energy sources. However, to enhance the integration of renewable energies into the industrial section, it is necessary to employ thermal energy storage media. Among different thermal energy storage options, concrete has proven to be a very effective sensible thermal energy storage solution. However, its main raw material (i.e., the Portland cement), is the cause of huge CO2 emissions to the environment. This study focuses on the design, manufacture, assembly and experimentation of thermal energy storage blocks made of alternative binders in substitution of Portland cement: i.e., hybrid materials and alkaline activated materials. The thermal energy storage blocks have been thermally cycled, with a charging temperature of 228 °C and a discharging temperature of 30 °C, in order to analyze the operational times and temperatures. The results obtained are very promising and comparable to those of the Portland cement system. Charging times have improved, with the alternative materials achieving temperature increases of up to 4%, while greater stabilization has been achieved during discharge, with the fluid reaching temperatures up to 6% higher than the reference system. These advancements support efficient, sustainable thermal energy storage technologies.