8. Conclusion

The storage of heat or cold is one of the important building blocks with great potential for a transition to clean, low-carbon energy. The applications targeted are mainly heating and cooling in the residential and tertiary sectors, which account for a very large share of energy expenditure in our countries. The challenge would be to develop cost-effective and efficient long-term storage systems that could, for example, transfer solar thermal heat or cold from one season to another, thus freeing us from fossil fuels and saving electricity. However, their development remains limited by a number of technical and economic factors. Sensible heat storage is well known and used, especially for short periods. For economic reasons, water remains the main storage medium. The main obstacles to development are the high volumes required for inter-seasonality. Underground storage is promising, but requires...