The technological development and economic of scale for solar photovoltaic (PV), batteries and combined heat and power (CHP) have led to the technical potential for a mass-scale transition to offgrid home electricity production for a significant number of utility customers. However, economic projections on complex hybrid systems utilizing these three technologies is challenging and no comprehensive method is available for guiding decision makers. This paper provides a new method of quantifying the economic viability of off-grid PV+battery+CHP systems by calculating the levelized cost of electricity (LCOE) of the technology to be compared to centralized grid electricity. The analysis is inherently conservative as it does not include the additional value of the heat form the CHP unit. A case study for residential electricity and thermal demand in an extreme worst case environment (Houghton, Michigan) is provided to demonstrate the methodology. The results of this case study show that with reasonable economic assumptions and current costs, PV+battery+CHP systems already provide a potential source of profit for some consumers to leave the grid. A sensitivity analysis for LCOE of such a hybrid system was then carried out on the capital cost of the three energy subsystems , capacity factor of PV and CHP, efficiency of the CHP, natural gas rates, and fuel consumption of the CHP. The results of the sensitivity provide decision makers with clear guides to the LCOE of distributed generation with off-grid PV+battery+CHP systems and offer support to preliminary analysis that indicated a potential increase in grid defection in the U.S. in the near future.

a b s t r a c tUntil recently, the relatively high levelized cost of electricity from solar photovoltaic (PV) technology limited deployment; however, recent cost reductions, combined with various financial incentives and innovative financing techniques, have made PV fully competitive with conventional sources in many American regions. In addition, the costs of electrical storage have also declined enough to make PV + battery systems potentially economically viable for a mass-scale off-grid low-emission transition. However, many regions in the U.S. (e.g. Northern areas) cannot have off-grid PV systems without prohibitively large battery systems. Small-scale combined heat and power (CHP) systems provide a potential solution for off-grid power backup of residential-scale PV + battery arrays, while also minimizing emissions from conventional sources. Thus, an opportunity is now available to maximize the use of solar energy and gain the improved efficiencies possible with CHPs to deploy PV + battery + CHP systems throughout the U.S. The aim of this study is to determine the technical viability of such systems by simulating PV + battery + CHP hybrid systems deployed in three representative regions in the U.S., using the Hybrid Optimization Model for Electric Renewable (HOMER) Pro Microgrid Analysis tool. The results show that the electricity generated by each component of the hybrid system can be coupled to fulfill the residential load demand. A sensitivity analysis of these hybrid off grid systems is carried out as a function capacity factor of both the PV and CHP units. The results show that conservatively sized systems are technically viable in any continental American climate and the details are discussed to provide guidance for both design and deployment of PV + battery + CHP hybrid systems to reduce consumer costs, while reducing energy-and electricity-related emissions.

To examine the potential of distributed microgrids using sustainable energy sources centered on retail store parking lots, this study provides a methodology to simulate medium‐scale solar photovoltaic (PV) + combined heat and power (CHP) + battery hybrid microgrid systems deployed at big box retail stores. First, a method is provided to agglomerate 15‐min load data for a community of residences in the region of the store to provide baseline electricity load profiles. The systems are then modeled using dispatch strategies previously shown to be stable for smaller, but more dynamic loaded systems. The methodology is demonstrated with a case study for a Walmart Supercenter located in Nova Scotia, Canada. The electricity generated by each component of the hybrid system is coupled and optimized to fulfill the electric demands of the local community. The results provide the total electricity generated by the PV + CHP + battery hybrid system, total operating hours by each unit, fuel consumed, and hourly energy produced by each unit. The results show that such microgrid systems could serve the electrical needs of ˜1000 people (350 residences) for each parking lot of 3.5 MW PV system and CHP unit of 1 MW. The technical viability of this approach warrants future work.

We consider a continuous review inventory system for inventory model involving lost sales reduction through capital investment cost function and the reduction of lead time further which reduces the ordering cost. To reduce the lost sales rate, two forms of capital investment cost function, viz. logarithmic and power are employed. Two relationships between ordering cost and lead time, viz. linear and logarithmic are considered. We develop four inventory models by taking different combinations of capital investment cost function and ordering cost lead time relationship. Objective of the study is to reduce the total related cost by simultaneously optimizing the order quantity, safety factor, fraction of the shortages during the stock-out period that will be lost and length of lead time. The lead time demand is assumed to follow a mixture of normal distributions. The optimal solution is derived by developing computer programs using the software MATLAB. We also provide four numerical examples to illustrate the models.