(65d) Design of a Residential System Via Multi-Objective Optimization of a Techno-Ecological Network

Studies such as the Millennium Ecosystem Assessment (MEA) have indicated that anthropogenic activities are not operating sustainably due to the deterioration of natural capital (NC). Therefore, there is a desire to move from the current unsustainable state to a new state that is closer to the goal of sustainability. This poses an enormous multi-disciplinary challenge to industry and academia due to the complex and interconnected nature of the problem.

However, most efforts focus on improving technology as a means of shifting activities towards sustainability. Unfortunately, the second law of thermodynamics indicates that no technology by itself, developed now or in the future, can lead to sustainability, as side effects due to increase in entropy generation are inevitable. Because of this, the idea of integrating ecological solutions with technological solutions has become increasingly attractive due to the self-sustaining properties that ecosystems have shown for millennia. We propose the use of techno-ecological (TE) networks for the design of self-sufficient processes as a step toward sustainability. Here, both technological and ecological subsystems are interconnected through the flow of material and energy to form closed-loop systems that minimize waste and have high overall efficiencies, despite the fact that individual nodes within the network may not be. Also, this automatically accounts for the carrying capacity of the included ecosystems, ensuring that this is not breached.

To illustrate this concept, we have applied TE networks to the design of a residential system. Residential homes account for 15-25% of primary energy consumption in developed countries and therefore much attention is paid to redesigning homes to make them less dependent on non-renewable energy. Again, most work focuses on technological solutions to improve the sustainability of homes. We propose the use of ecosystems as well in the design problem to achieve the goal of sustainability. For example, turf grass and trees can sequester carbon, trees provide natural shading to reduce external cooling loads, on-site water reservoirs for freshwater and water treatment. Also, this system presents many behavioral variables that can be considered for moving the system towards sustainability. This problem is a relevant and accessible illustration of the TE network concept and how it can be applied to the design of a relatively complex system. Results from extensive case studies based on combining the Department of Energy's EnergyPlus building simulation tool with ecological models will be presented.