A Comprehensive Review on Enhancing Seasonal Energy Storage Systems through Energy Efficiency Perspectives.

The global energy transition requires efficient seasonal energy storage systems (SESSs) to manage fluctuations in renewable energy supply and demand. This review focuses on advancements in SESSs, particularly their integration into solar district heating systems, highlighting their role in reducing greenhouse gas emissions and enhancing energy efficiency. Tanks are the most suitable solutions for seasonal storage, as they can be implemented regardless of location for volumes up to 100,000 m³. However, pits are the most optimal solutions in terms of cost and size, as they can be constructed for volumes up to 200,000 m³. This review analyses key performance indicators such as energy efficiency, cost-effectiveness, and environmental impact, drawing on case studies from countries like Denmark and Germany. Notable findings include Denmark's Silkeborg system, which supplies 22,000 households and reduces CO₂ emissions by 15,000 tons annually. Challenges such as high initial costs and system maintenance remain, but coupling SESSs with heat pumps enhances thermal stratification within SESSs. This approach can reduce the annual cost by up to 9% and the purchase cost of energy by 23%. Future research should focus on innovative materials, system design optimization, and supportive policies to enhance adoption. In conclusion, advancing SESS technologies and integrating them into renewable energy systems is necessary for achieving sustainable energy solutions and mitigating climate change impacts. [ABSTRACT FROM AUTHOR]