Application of combined heat-and-power and absorption cooling in a supermarket

In recent years, it has become standard practice to consider Combined Heat- and-Power (CHP) systems for commercial buildings. CHP schemes are used, bec ause they are an efficient means of power generation. Unlike conventional p ower stations, they produce electricity locally and thus minimise the distr ibution losses, however, they also utilise the waste heat from the generati on process. In applications where there is a combined heating and electrici ty requirement, a very efficient means of energy production is achieved com pared to the conventional methods of providing heating and electricity. Wit h new initiatives from the UK government on reduced energy-use, energy-effi cient systems such as CHP have been considered for new applications, This p aper summarises the results of an investigation into the viability of CHP s ystems in supermarkets, The viability of conventional CHP has been theoreti cally investigated using a mathematical model of a typical supermarket. Thi s has demonstrated that a conventional CHP system may be practically applie d. It has also been shown that compared to the traditional supermarket desi gn, the proposed CHP system will use slightly less primary energy and the r unning costs will be significantly reduced. An attractive payback period of approximately 4 years has been calculated. Despite these advantages a cons iderable quantity of heat is rejected to atmosphere with this system and th is is because the configuration utilises the heat mainly for space heating which is only required for part of the year. To increase the utilisation ti me, a novel CHP/absorption system has been investigated. This configuration provides a continuous demand for the waste heat, which is used to drive an absorption chiller that refrigerates propylene glycol to -10 degrees C for cooling the chilled-food cabinets. The results show this concept to be the oretically practical. The system has also been shown to be extremely effici ent. with primary energy savings of approximately 20%; when compared to tra ditional supermarket designs and this would result in significant revenue c ost savings as well as environmental benefits. Based upon these savings a p ayback period for this system of approximately 5 years has been demonstrate d. (C) 1999 Elsevier Science Ltd. All rights reserved.