"Smart and Synergy Grids: the Leaf versus the Tree"
The tree pattern is the model of classical energy (or flows in general) distribution: remote production in a big central unit and then hierarchical distribution down to the single house. The tree pattern is Thomas Edison and electricity companies’ major contribution to urbanism at the end of 19th century. The efficiency and resilience problem of this pattern is that lower (and even intermediary levels) in the hierarchy are entirely disconnected, which not only creates losses in the flows (and a peak approach because there is no possibility of local transfers) but it makes them entirely vulnerable to any damage and break in the upper levels of the hierarchy. The paper is intended to provide an overview of an opposite concept we call Synergy Grids. This concept is based on an extension of a relatively well-known concept called smart grids. While current work on Smart Grids focuses on the optimization of supply and demand of electricity within large regions, Synergy Grids concentrate on a neighbourhood scale and multiple systems, including supply, demand and optimization of thermal energy, potable and grey-water systems, local renewable and DC power systems within buildings. All of these systems will require optimization algorithms and systems and a new form of zone management to be successful. The paper will eventually consider relevant issues in building uses, density and configuration. Smart or synergy grids are the opposite of hierarchical tree organisations, with not only local production, but also many loops and connectivity at the lower levels of the hierarchy, which increases the efficiency, the stability and the resilience of the system, like in the blood system or in a river delta. This pattern is similar to a leaf with multiple loops and connectivity. The paper will develop a mathematical approach of the synergy grids optimization and show that the most efficient and resilient structure is a size/frequency distribution of its elements following a Pareto law (an inverse power law), that is a scale free fractal. This is true for natural and artificial systems. This is the key of an efficient design of such a grid and even a way of measuring its theoretical gains of productivity according to different designs, scaling levels, degrees of connectivity. The paper thus integrates the optimisation of components (building scale) and the optimisation of the whole (urban scale) though a scaling approach based on the contemporary theories of complexity.