• Energy Research

Introduction of an integrated energy service system in an urban area is assumed. An energy supply plant is installed in the area to provide integrated energy service. It supplies electricity, gas, cooling, and heating to consumers. To consider CO/sub 2/ emission constraint in the area, analyses of energy pricing, economic impact on energy consumers, and operation of the system under the constraint of CO/sub 2/ emission were performed. CO/sub 2/ emission and economic impact on the consumers and the supplier of various energy pricing scenarios were calculated using linear programming models. The solution that satisfied the CO/sub 2/ emission restriction, and was economically optimal to the consumers was chosen from the results. The chosen solutions are Pareto optimum solutions of a multiobjective problem that concerns both CO/sub 2/ emission and cost to the consumers.

A practical charging strategy for an individual plug-in electric vehicle (PEV) is proposed. A cost function is constructed to reflect bidirectional electricity trade arising from surplus photovoltaic generation under the reward system called feed-in tariffs and time-of-use electricity pricing. It is then extended to include the revenue for providing vehicle-to-grid frequency regulation. In order to take advantages of high performance existing solvers, several mathematical techniques are applied to transform the discrete non-linear cost function to a differentiable continuous function. In the latter part of the paper, simulations are performed to verify and show the performance of the developed model. A quantitatively developed battery wear model is also applied during the simulations to calculate the effective operational cost, and to compare the costs for different control strategies. From the result of case study, the economic feasibility of the frequency regulation under the given circumstance is addressed as well.

JAPAN WAS AN EARLY LEADER IN MICROGRID research, with the four demonstrations funded by the New Energy and Industrial Technology Development Organization (NEDO) between 2003 and 2008 being particularly influential. In addition, there have been several notable private sector projects, as well as some remote island, dc power, and sustainable community demonstrations. Objectives for the four NEDO projects were primarily to demonstrate the high penetration of local small-scale renewables,local control of diverse resources, islanding, reliability, and heterogeneous power quality (HeQ).

Three kinds of energy service system were examined as alternative energy systems in urban areas. A comparison of these energy systems was performed by finding Pareto optimum solutions for a multi-objective model. The model had two objective functions: CO2 emission and cost to consumer. Various energy pricings were provided in the model as variables. The assumed alternative systems were those in which: (1) every consumer had a cogeneration system (CGS); (2) there was a centralized energy supply plant (ESP) that had a CGS installed and supplied energy (electricity, gas, cooling and heating) to consumers; and (3) both (1) and (2) were installed. Minimization of CO2 emissions and minimization of cost to consumers were assumed as objective functions of the multi-objective model. Energy prices that consumers paid were used in the model as variables. We performed an analysis and comparison of the three kinds of system from the viewpoints of CO2 emission, economic impact on consumers and ESP, using system operations as evaluation indexes.

The activities and present state of R&D and deployment of residential fuel cells in Japan are presented. More than 2,000 fuel cell systems using polymer electrolyte membrane fuel cells (PEFC) have been installed to general homes by the end of 2007. The development of residential solid oxide fuel cell (SOFC) systems is also being promoted toward market launch. The activities of Osaka Gas Ltd. are reported as an example of industrial sector. Osaka Gas is an active leader on residential cogeneration systems, and succeeded on residential micro-gas engine and PEM fuel cell cogeneration systems. The stories on the R&D of fuel cell cogeneration systems, especially on the control strategy improvement for energy saving are presented. The future prospective by authors was also addressed.

Abstract Owing to the high penetration of renewable energy sources, power systems require more flexibility to respond to the fluctuation of variable renewable energy sources. However, flexibility provision by distributed energy resources (DERs) installed on the demand side is a cost-effective measure. In this study, we proposed a scheme that utilizes time-of-use (TOU) electricity rates as an incentive to encourage residential prosumers to provide more flexibility by controlling the DERs. In particular, we developed an energy management system model that applies model predictive control. The TOU rates were designed by an aggregator who traded with markets and prosumers. The DERs of residential prosumers were fuel cells with combined heat and power, CO2 heat pump water heaters, or batteries. Numerical simulations using measured energy demand and insolation data were performed to evaluate the performance of the developed model. According to the results, the developed model could integrate prediction errors and provide flexibility to the grid. Finally, the economies of the aggregator and prosumers were also evaluated.

AbstractThe U.S. Department of Energy has launched the commercial building initiative (CBI) in pursuit of its research goal of achieving zero‐net‐energy commercial buildings (ZNEB), i.e., ones that produce as much energy as they use. Its objective is to make these buildings marketable by 2025 such that they minimize their energy use through cutting‐edge, energy‐efficiency technologies and meet their remaining energy needs through on‐site renewable energy generation. This paper examines how such buildings may be implemented within the context of a cost‐ or CO2‐minimizing microgrid that is able to adopt and operate various technologies: photovoltaic (PV) modules and other on‐site generation, heat exchangers, solar thermal collectors, absorption chillers, and passive/demand‐response technologies. A mixed‐integer linear program (MILP) that has a multi‐criteria objective function is used. The objective is minimization of a weighted average of the building's annual energy costs and CO2 emissions. The MILP's constraints ensure energy balance and capacity limits. In addition, constraining the building's energy consumed to equal its energy exports enables us to explore how energy sales and demand‐response measures may enable compliance with the ZNEB objective. Using a commercial test site in northern California with existing tariff rates and technology data, we find that a ZNEB requires ample PV capacity installed to ensure electricity sales during the day. This is complemented by investment in energy‐efficient combined heat and power (CHP) equipment, while occasional demand response saves energy consumption. A large amount of storage is also adopted, which may be impractical. Nevertheless, it shows the nature of the solutions and costs necessary to achieve a ZNEB. Additionally, the ZNEB approach does not necessary lead to zero‐carbon (ZC) buildings as is frequently argued. We also show a multi‐objective frontier for the CA example, which allows us to estimate the needed technologies and costs for achieving a ZC building or microgrid. Copyright © 2010 John Wiley & Sons, Ltd.