A MILP model for integrated plan and evaluation of distributed energy systems

In the last decade, technological innovations and a changing economic and regulatory environment have resulted in a renewed interest for distributed energy resources (DER). However, because of the lack of a suitable design tool, the expected potential of DER penetration is not always exerted sufficiently. In this paper, a mixed-integer linear programming (MILP) model has been developed for the integrated plan and evaluation of DER systems. Given the site's energy loads, local climate data, utility tariff structure, and information (both technical and financial) on candidate DER technologies, the model minimizes overall energy cost for a test year by selecting the units to install and determining their operating schedules. Furthermore, the economic, energetic and environmental effects of the DER system can be evaluated. As an illustrative example, an investigation has been conducted of economically optimal DER system for an eco-campus in Kitakyushu, Japan. The result illustrates that gas engine is currently the most popular DER technology from the economic point of view. Although holding reasonable economic merits, unless combined with heat recovery units, the introduction of DER technologies may result in marginal or even adverse environmental effects. Furthermore, according to the results of sensitivity analysis, the optimal system combination and corresponding economic and environmental performances are more or less sensitive to the scale of energy demand, energy prices (both electricity and city gas), as well as carbon tax rate.