This paper, prepared by a special task force of the IEEE PES Renewable Technologies Subcommittee, is a review of hybrid renewable/alternative energy (RE/AE) power generation systems focusing on energy sustainability. It highlights some important issues and challenges in the design and energy management of hybrid RE/AE systems. System configurations, generation unit sizing, storage needs, and energy management and control are addressed. Statistics on the current status and future trend of renewable power generation, as well as some critical challenges facing the widespread deployment of RE/AE power generation technologies and vision for future research in this area are also presented. The comprehensive list of references given at the end of the paper should be helpful to researchers working in this area.

The intermittency of renewable energy sources makes the use of energy storage systems (ESSs) indispensable in modern power grids for supply-demand balancing and reliability enhancement. Besides pumped-storage hydroelectric power stations, energy storage deployment worldwide is still quite low. However, the status quo might rapidly change as the energy storage technologies are growing and facilitating market regulations are being ratified. Battery energy storage systems (BESSs), Li-ion batteries in particular, possess attractive properties and are taking over other types of storage technologies. Thus, in this article, we review and evaluate the current state of the art in managing grid-connected Li-ion BESSs and their participation in electricity markets. The review mainly includes battery modeling, the architecture of battery management systems (BMSs), the incorporation of BESSs for electricity market services, global utility-scale battery storage facilities, and challenges in implementing and managing grid-connected BESSs.

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).

In March 2011, Japan suffered devastating damage from the Great East Japan Earthquake (GEJE) and accompanying tsunami, which caused massive blackouts affecting 8.5 million customers. Damage to power stations, including Fukushima Daiichi Nuclear Power Station, caused a long-term, nationwide power shortage. Other infrastructure and customer facilities were damaged as well. Demand-side resiliency means the availability of electricity to consumers, which is an important factor that affects business continuity. Onsite generation and microgrids have been recognized as important measures that improve resiliency; successful real-life applications of these technologies, such as the Sendai Microgrid and Roppongi Hills, have increased after the GEJE. Metrics on the importance of loads or facilities and resiliency are needed to encourage investment by supporting business operators' decision making and enabling quantitative analyses of the tradeoff between cost and resiliency improvement. This paper presents a comprehensive outline of experiences and lessons learned from the GEJE from the viewpoint of demand-side resiliency-or the availability of electricity to consumers. Damage to power systems and power supply capability through power source loss, best practices (including microgrids), and post-disaster responses and lessons learned are all examined.