(627g) Combined Heat and Power for Residential Neighborhoods: A Data-Driven Modeling and Optimization Study

Combined heat and power (CHP) facilities are a very promising path to reducing CO₂ emissions and increasing efficiency in the power generation sector, especially when combined with residential solar power generation. CHP facilities rely on natural gas, a cleaner fuel than coal, to generate electricity and hot and chilled water. The ability to supply these essential residential utilities in an efficient way on a medium to large scale opens the path for combining district cooling, heating and power generation, and suggests that CHP plants are a very appealing choice for providing integrated utilities for the neighborhood of the future. Yet, there are currently no CHP plants that serve just residential neighborhoods, and published works exploring this possibility are scarce.

Approximately 20% of the electricity produced in the United States is used in the residential sector, with about half of this energy going to heating, ventilation, and air-conditioning (HVAC) systems [1]. Coal-fired power plants, which provide a majority of the electricity, have very high CO₂ emissions and among the lowest efficiencies of all power generation facilities. CHP plants powered by natural gas can reach efficiencies over 80%, more than twice that of coal-powered plants, which are often less than 38% [2]. In combination with district cooling, CHP plants also lower CO₂ emissions by a factor of 10 [3]. In a CHP case study conducted by Austin Energy, the local power utility in Austin, TX, in 2010, Austin Energy’s Fayette Power coal-powered plant was only able to convert 35% of the primary fuel into electricity, and an additional 6% was lost in transmission to a large consumer (Dell Children’s Medical Center) situated less than 10 miles (16.8km) away. A subsequent investment in a localized CHP facility at Dell Childern’s demonstrated that at least 75% of the primary energy source (natural gas) can be converted to power with no transmission losses [4]. Yet- and in spite of these appealing energy efficiency benefits - there are currently no CHP plants in the United States that provide integrated utilities (heating, cooling and power) to residential neighborhoods, and studies exploring such opportunities are not available.

In the paper, we describe the optimal integration of a CHP plant as a utility producer for a residential neighborhood, and the potential for using photovoltaics and energy storage, implemented in a centralized fashion, to alleviate fluctuations in residential demand. Utilizing data collected by Pecan Street Research Inc., a smart-grid demonstration project headquartered at The University of Texas at Austin, residential heating, cooling, and electricity demand are analyzed and evaluated. These data are then used to create a time-resolved energy profile pertaining to residential energy demand. Subsequenlty,  we compute an optimal operating strategy for an integrated CHP/solar utility and determine the optimal ratio of generating capacity between CHP and photovoltaic generation, such that the effect of fluctuations in energy demand is minimized. We demonstrate that CHP a viable means for providing district-level cooling and power in a predominantly cooling climate and, furthermore, we study the economic and operational impact of integrating, in a similarly centralized manner, CHP production with various forms of energy storage (e.g., thermal, electrical).

References

[1] U.S. Energy Information Administration, “Annual Energy Review 2011.” 27-Sep-2012.

[2] Combined Heat & Power Association, “What is CHP?”

[3] DHC + Technology Platform, “District Heating & Cooling.” Mar-2012.

[4] Jim Collins. Combined Heat & Power Conference 2011, “Case Studies: Mueller Energy Center at Dell Children’ Medical Center, Austin, TX.” 3-Nov-2010.