Feasibility studies on technical and economic impact of combined heat and power (CHP) generation on energy supply for commercial small & medium size enterprise (SME)

The purpose of this paper is to provide a technical and economic feasibility assessment on a SME to establish if it is suitable to install a CHP plant to provide onsite generation of electrical and thermal energy. The type of SME used for this paper as case study is a large shopping centre located at the south-west of the Republic of Ireland. At present, electrical energy is supplied from the Electricity Supply Board at 10.5kV while thermal energy for hot water is generated using onsite boiler using natural gas as prime fuel. The shopping centre has a total area of 55, 000 m² where 23,225m² is used as rentable retail space. Currently, the shopping centre provides facilities for over 70 commercial units. Electrical energy is distributed via 9 substation supplying different sections of the shopping centre. Each substations is equipped with energy metering facilities and based on annual records the average electrical load on the common areas (Lighting, HVAC, General Services) is 274kW with the peak demand of 345kW in any 15 min period. The average electrical load on the common areas during the day (8:00am-21:00pm) is 217kW, while during the night (21:00pm-8:00am) it is 57kW. From the data obtained from the Electrical Supply Board the average electrical load on the shopping centre is 1.78MW. Electrical energy consumption for each retail unit is individually metered and it is estimated that the main electrical load consists of lighting and HVAC. In the case of the supermarket the highest electrical energy demand is for supplying refrigerators that are required for perishable products. Refrigeration and HVAC can account for 60% of the electrical load on the supermarket.