The role of cool thermal energy storage (CTES) in the integration of renewable energy sources (RES) and peak load reduction

The building sector is one of the largest energy consumers. Even though cooling needs do not contribute a large share to the overall energy demand in temperate climates, recent trends show a tendency of large growth. This growth is related to two main drivers: cheap and affordable air-conditioning units that have overrun the market and the more frequent occurrence of hot and extremely hot weather conditions. In combination with inadequate insulation and sealing in most old buildings, both drivers contributed to new cooling installations that are significantly increasing electricity demand and peak load, even at the national level. Consequently, the use of fossil fuels in power plants and electricity import has increased. The development of sustainable buildings and the use of renewable energy sources (RES) seem to be promising solutions. However, the problem of the integration of RES in the current energy system is related to their intermittent nature and uncontrollable occurrence. Cool Thermal Energy Storage (CTES) may play an important role in the management of peak loads and solve the intermittency problem of RES, especially when cooling storage is integrated into district cooling systems. A simple mathematical model of a system with integrated RES and CTES has been developed. Hourly system analyses have been conducted for one building, a group of buildings connected to the district cooling system and a region represented by a mixture of different demands for cool thermal energy. This paper also includes the results for the overall energy efficiency, cost effectiveness and environmental impact of the systems analysed.