The Exergy scan

The Exergy Scan is a quick tool to estimate the fuel and feedstock losses within a plant and to suggest improvements to reduce these losses. Exergy has to be used to locate the losses of fuel and feedstock. Energy is never lost as stated in the first law of thermodynamics and so energy can not be saved. However, the quality of energy is lost and to qantify this exergy is needed. For a good energy saving study the concept of exergy is needed. However, to perform an exergy analysis is too time consuming. To overcome this problem the Exergy Scan has been developed. In a limited amount of time the exergy losses of the main components can be estimated. Furthermore, the Exergy Scan gives an indication of the amount of exergy loss is relatively high or low for the component under consideration. This indication is given by comparing the exergetic efficiency with common efficiencies and state of the art efficiencies. These values are listed in a database or can be calculated with special developed calculating routines. The optimisation of the system takes place with the onion model.

The onion model means that the optimisation should start in the center of the plant with process optimisation. After the process optimisation follows the different layers of the onion, heat integration, power generation and import or export of energy. The suggested improvements are ranked on the pay back period and the risks assocaited with the improvements. For the estimation of the risks the onion model is used. As the suggested improvement is in the outer layer of the model the risk is lower.

For performing the Exergy Scan an already existing methodology of energy saving studies is used. In the methodology the project management is described.

The Exergy Scan is performed on two companies, namely the car tyre production company Vredestein Banden B.V. and Rockwool Lapinus B.V., a producer of insulation products. The Exergy Scan of Vredestein identified different cost effective improvements, which could lead to a saving of 20% on the total natural gas use. More information (file ExergieVRinternet)

Click here to download the case-study.