A promising and shortly emerging energy supply chain network based on residential-scale microgeneration through micro combined heat and power systems is proposed, modeled and optimized in this work. Interchange of electrical energy can take place among the members of this domestic microgrid, which is connected to the main electrical grid for potential power interchange with it. A mathematical programming framework is developed for the operational planning of such energy supply chain networks. The minimization of total costs (including microgeneration system’s startup and operating costs as well as electricity production revenue, sales, and purchases), under full heat demand satisfaction, constitutes the objective function in this study. Additionally, an alternative microgrid structure that allows the heat interchange within subgroups of the overall microgrid is proposed, and the initial mathematical programming formulation is extended to deal with this new aspect. An illustrative example is presented in order to highlight the particular significance of selecting a proper optimization goal that thoroughly takes into account the major operational, technical and economic driven factors of the problem in question. Also, a number of real-world size case studies are used to illustrate the efficiency, applicability and the potential benefits of the microgeneration energy supply chain networks suggested in this study. Finally, some concluding remarks are drawn and potential future research directions are identified.
Although many technical options exist for developing a future sustainable and more environmentally friendly energy supply chain, they are often treated separately driven by their own technical communities and political groups. In this context, energy systems engineering can provide a systematic model-based framework to arrive at realistic integrated solutions to the complex energy problems by adopting a holistic systems-based approach [8] and [10].
Nowadays, it is evident that the classical energy supply chain is rapidly changing to an energy-efficient and low-carbon energy market economy by moving towards more decentralized energy production. In accordance with the energy systems engineering perspective, there is clearly a distributed energy generation option which could play a vital role within the development of sustainable future energy systems, the energy microgeneration. Specifically, the most promising microgeneration technology involves the cogeneration (i.e., combined generation) of electrical energy and heat in small-scale energy generation units that can be directly embedded in the buildings wherein the heat and electricity are to be used. The major benefit of cogeneration systems is that their overall efficiency can be as much as 90%, while if just electricity is produced, an efficiency of no more than 40–45% could be achieved. Additionally, cogeneration networks could serve electricity markets with lower investments in the transmission and distribution grids and with lower energy losses during transmission [18] and [1]. The domestic sector constitutes a key consumer of both electricity and heat, and could benefit from consolidation to meet these demands via micro Combined Heat and Power (microCHP) generators [9]. Several studies demonstrated that microCHP technologies can reduce significantly household energy-costs and carbon emissions, and increase overall energy utilization efficiency [7], [13], [5] and [15].
1.1. Microgeneration vs large-scale centralized generation
It is broadly alleged that microgeneration has diverse benefits over its (typical) large-scale centralized counterpart, including: (i) more efficient use of the thermal energy due to local heat generation thus maximizing the utilization of primary energy, (ii) lessened electricity transmission line load and losses, and transmission lines upgrades, (iii) reduction in the environmental footprint of producing energy, (iv) increase of the stability and reliability of the main electrical grid in electricity demand peak periods or temporal system failures, (v) a more reliable and customized operation under low maintenance needs, (vi) significant decrease in the reliance on the power companies, and (vii) reduced land use for energy generation. Also, small scale energy generation technologies can adapt better and faster to load curve variations than large ones and can ensure the possibility of finding solutions tailored to meet specific energy needs because of their scalability [11]. Overall, the centralized energy generation has been considered more economical, however a mass production of microgenerators will rapidly reduce their associated capital cost. Nevertheless, this mass production of microgenerators will probably result in significant environmental impact, if it is not realized with environmental “friendly” production processes.
Furthermore, it is of particular importance to underline that microgeneration – apart from the apparent cost and environmental benefits – engages people as energy citizens, not merely consumers, giving them responsibilities as they act as producers, consumers and investors, involving an energy literacy which connects everyday behavior with energy use and emissions [3]. A direct output of such energy systems is the generation of more energy-conscious individuals, favoring energy sustainability that is of great significance nowadays.
In this work, a mathematical programming formulation has been developed for the operational planning of residential energy supply chain networks based on microgeneration technologies. Two innovative alternative network structures have been proposed, and a comparative study with the conventional case and the standalone operation of the microgenerators provides significant insights. It is demonstrated that the microgeneration energy supply networks introduced (and especially the Extended structure) clearly overwhelm their counterparts (boiler systems, standalone operation). Assuming appropriate governmental incentives and policies as well as further progress and innovation in microgeneration technologies (such as fuel cells), this type of residential energy microgrids is expected to emerge and expand rapidly in the near future. Finally, further research could be focused on examining alternative microCHP system structures, integrating the operational planning with advance control, and/or considering alternative electricity market environments.
