6 Combined Cooling, Heating, and Power Systems for Buildings

Combined Cooling, Heating and Power (CCHP) is an efficient, clean, and reliable approach to generating power and thermal energy simultaneously from a single fuel source on site. A CCHP system is usually designed to provide power in the form of electricity while recovering the available waste heat for serving heating and/or cooling load. We start this chapter with an overview of the state-of-the-art in CCHP systems applied to commercial and residential buildings to maximize their primary energy efficiency. We continue with a discussion of available prime mover options ranging from classic technologies, such as internal combustion engines, to emerging technologies such as thermoelectric generators. We also discuss different heat recovery concepts along with their limitations and design challenges. These include gas-to-gas heat exchangers, gas-to-liquid heat exchangers, and condensing economizers, as well as advanced concepts such as transport membrane condensers. We then present the available heat pump technologies that can be matched with the different prime movers to service the building heating and/or cooling load. These heat pump options include classic thermally activated technologies such as the absorption and adsorption heat pumps as well as other emerging technologies such as thermo-acoustic heat pumps and the Vuilleumier cycle.

A properly designed building CCHP can meet the entire building thermal load and offset significant electricity consumption at higher primary energy efficiency compared to conventional technologies — heating equipment and purchased electricity from the grid. To guide the design if building CCHP, we first address the two approaches to sizing CCHP and identifying system configurations: electric load following and thermal load following. We also present sample thermal and electric load profiles for different types of buildings and present a step-by-step CCHP system design and integration for a health care facility. Furthermore, we discuss several of the system integration challenges. Finally, we present a quick discussion on the economic and feasibility assessment of building CCHP systems.