Distributed generation, microgrids, thermal energy storage, and micro-combine heat and power generation

Abstract

Energy sustainability is the cornerstone to the health and competitiveness of the industries in our global economy. It is more than being environmentally responsible, means the ability to utilize and optimize multiple sources of secure and affordable energy for the enterprises, and then continuously improve the utilization through systems analysis, energy diversification, conservation, and intelligent use of these resources. Distributed energy resources (DER) and dispersed generation systems are becoming more important in the future electricity generation. A description of distributed energy resource and types, characteristics, performances, is the subject of this chapter. Brief presentations of the power system interfaces, power electronics, and control of distributed generation systems are also included. The chapter presents an overview of the key issues concerning the integration of distributed and dispersed generation systems, the role of thermal energy storage (TES) systems and the main applications. A synopsis of the main challenges and issues that must be overcome in the process of DG and DER applications and integration are presented. Particular emphasis is placed on the need to move away from the fit and forget approach of connecting DG to electric power systems to a policy of integrating DG into power system planning and operation through active management of distribution networks and application of other novel concepts. Several distributed energy systems, together with energy storage capabilities, expected to have a significant impact on the energy market are presented and discussed. Microgrid is a new approach of power generation and delivery system that considers DG, DER, and loads, often controllable loads is set as a small controllable subsystem of a power distribution network. The microgrid subsystem has characteristics, such as the ability to operate in parallel or in isolation from the electrical grid, having the capabilities and functionalities to improve service and power quality, reliability, and operational optimality. Microgrids may also be described as a self-contained subset of indigenous generation, distribution system assets, protection and control capabilities, and end user loads that may be operated in either a utility connected mode or in an isolated from the utility mode. In addition to providing reliable electric power supply, microgrids are also capable of providing a wide array of ancillary services, such as voltage support, frequency regulation, harmonic cancellation, power factor correction, spinning, and nonspinning reserves. A microgrid may be intrinsically distributive in nature including several DGs-both renewable and conventional sourced energy storage elements, protection systems, end user loads, and other elements. In order to achieve a coordinated performance of a microgrid (or several microgrids) within the scope of a distribution company, it is required to perform distributed or cooperative control. This harvested energy through such applications can be released onto the grid, when needed, to eliminate the need for high-cost peak generators or can be used local for heat and hot water or other industrial process applications. Microcombined heat and power (CHP) systems powering up to about 10 kWe are considered as a future key technology for the building or facility energy supplies from the viewpoints of heating system users, manufacturers, and energy suppliers. CHP plants can be based on conventional diesel, gas or biomass engines, gas turbines, Stirling engines, or fuel cells. Energy storage systems are an important component of the renewable energy technology applications. Among the storage technologies, the TES, a technology that stocks thermal energy by heating or cooling a storage medium and use the stored energy at a later time for heating, cooling and power generation. TES systems are used particularly in buildings and in industrial processes, while the main advantages of using TES in an energy system, building or industrial process include an increase in overall efficiency and better reliability, leading to the reductions in investment and running costs, and less environmental pollution of the environment. Energy storage inclusion into distributed generation systems provides the user dispatchability of DER, while improving the overall system performances and capabilities. All of the DER and DG technologies require specific power electronics and control schemes to convert the generated power into useful power that can be directly interconnected with the grid or that can be used for specific applications. This chapter presents convenient resources to understand the current state-of-the art power electronic interfaces for DER and DG applications. In this chapter, a description of TES systems and microCHP generation systems is presented with references to heating, ventilation, and air conditioning systems. A discussion on the major components of such systems, load analysis and methods for improving the energy efficiency of existing systems are also included in this chapter. After completing this chapter, the readers are able to understand the importance and role of the thermal energy systems and storage, energy conservation and efficiency in building electrical and mechanical systems, and in industrial energy systems and equipment. A special attention is given to the understanding and learning about micro-CHP generation systems, components and configurations of such systems, their operation, functions, and capabilities.