Energy and underground

Driven by urbanization growth, in recent years, the relationships among energy systems and underground space are becoming more and more intense for many reasons: the severe competition in the land use, the security of energy commodities management, the need of huge infrastructures for mass and energy transportation (e.g. pipelines), the safety requirements against seismic events and eventually, economic and environmental considerations. For such reasons, nowadays underground space is becoming an extremely important as an alternative for urban areas expansion, if properly planned. In fact, a correct underground space planning strategy, together with the progressive developments of suitable integrated connections between surface and subsurface can increase the livability of cities and improve public health. Population in urban areas is expected to grow, in particular in developing economies (such as China); this phenomenon leads to an increasing pressure on urban areas to supply the growing energy needs. In fact, several end-use services should be fulfilled to provide indoor comfort in buildings, for mobility of people and goods, etc. Anyway, only a very limited amount of energy can be generated inside urban areas (from municipal solid wastes, from thermal/solar PV and heat pumps installations); as a consequence, the majority of the energy commodities are produced, converted and stored in power plants located far from cities and require huge transport infrastructures. In this paper, the cost/benefit relationship between underground and energy use is explained by reviewing main application of existing underground space utilizations for energy processes (distribution, storage and generation), as well as other innovative opportunities. From the analysis of past experiences analysis, the main conclusion is that a rational approach in urban energy planning procedures, integrating both over- and below-ground space utilizations, could help to raise the quality of energy services and it is fundamental for reaching a smarter and more resilient society. In such a new Underground Urbanism approach, the need for long-term Integrated Master Plans that propose suitable Guidelines is highlighted.