Energy analysis of energy users The aim of an energy analysis of energy users is to get a good understanding of the size, characteristics and main determinants of the energy use of an entity, whether that is a household, office building, industrial production site, or power plant. Such an energy analysis generally forms the basis for further action to improve energy efficiency, reduce energy costs, reduce emissions, etc. An energy analysis generally combines top-down and bottom-up information. Top-down information is information about the entity as a whole (e.g. total energy purchase), whereas bottom-up information is information about individual equipment. The following is a generic procedure for an energy analysis:
1. Determine total energy use. Total energy use is determined for all relevant energy carriers, using energy bills and meter readings. Such sources provide not only totals per year or per month, but also additional information such as day/night ratios of electricity use and peak demand.
2. Registration of equipment. An overview is made of all the energy-using equipment and all the energy conversion equipment (e.g. boilers). The nominal capacity is determined for all the equipment; this is often indicated on the equipment, or information is available from the manufacturer. The operation time, or the equivalent operation time, is also determined for all equipment. The product of the nominal capacity and operation time provides the annual amount of energy use of the equipment. Other operational parameters are also registered, like temperature set points.
3. Registration of building characteristics. An overview is made of the characteristics of the buildings: (i) area of the various components of the building envelope (walls, roofs, windows); (ii) degree of insulation of the various components; (iii) volume of the various parts of the building; (iv) ventilation rate of the building. This information is necessary to determine the energy use for space heating and cooling (see Section 3.2).
4. Additional measurements. When the information provided in the two previous steps is not complete or not accurate enough, additional measurements of the uncertain energy flows are necessary.
5. Closing the energy balance. Finally, the energy balance is drawn up. The total energy inputs to the facility (step 1) are compared with the amounts converted and used (steps 2–4). In case these figures do not agree, additional investigations and measurements are necessary to bridge the gap. Note that this is actually a simple application of the first law of thermodynamics.