Search

The industry sector has an important role in decarbonising the energy system, as recognised by the European Commission in their 2050 roadmap to a low carbon economy. It has a high share in the final energy use of the European Union, which in 2016 relied heavily on fossil fuels. A shift to a more sustainable energy use is thus needed, requiring both an increased share of renewable energy and a reduction in energy use.In this thesis the manufacturing industry was analysed to show its potential to improve energy use on an energy system and process level. For this purpose the inefficiencies of the industry sector of Denmark were taken as an example and quantified using energy and exergy methods. The developed models were used to quantify the amount of industrial excess heat. Based on these mappings, the potential for recovering and exploiting excess heat was analysed, which required the development of new methods to locate potentials. The methods included spatial, temporal and economic elements to have a realistic assessment of national potentials. This was complemented with multiple case studies, for which the model input uncertainties were taken into account. The second part of the thesis considered specific production processes and methods for assessing them. For the case study of a milk powder production system, different engineering and advanced thermodynamic methods were used for the analysis. The different methods, which include pinch and exergy analyses, located and quantified different optimisation potentials, which were compared against each other. At last, specific optimisation opportunities were identified and evaluated. These consisted of a retrofit heat exchanger network and the integration of heat pumps and solar thermal energy.The results show that the energy efficiency of the Danish manufacturing industry was 80 % and only 72 % when taking the utility system into account. The losses are often in the form of recoverable excess heat. It was found that 1.5 TWh of excess heat could be cost-effectively used for district heating. The tool developed for the case studies enables to overcome some of the barriers for the utilisation of excess heat. It assesses heat sources and possible uses considering the uncertainties and determining important model parameters.The analysis of the dairy factory resulted in potentials for improvement and highlighted merits and drawbacks of the applied methods. The advanced methods allowed for a thorough analysis of components and interactions amongst each other, the engineering approach is quick to indicate possible improvement but requires experience. The specific improvement suggestions show that it is technically and economically possible to reduce energy use by means of heat integration and to partly replace the hot and cold utilities with more sustainable ones.

This report contains an evaluation of the potential waste heat sources in Denmark. The evaluation is based on data from Statistics Denmark on the 15 Danish sectors (the 15 sectors are grouped in five categories that have similar consumption/production patterns). Besides the 15 sectors, the accessible heat from three natural energy sources is also included in the evaluation. The quantification of the potential waste heat is based on a number of approaches such as, professional experience within Viegand Maagøe, input from project partners, theoretical calculations, case studies, input from suppliers, input from end-users etc.It must be emphasized that the total energy consumption used in this study covers all end-users and utility companies and therefore the total energy consumption can be higher than what can be found in other statistic. By including both utility companies and end-users a double counting of net energy input can occur, if e.g. the output from the utility company is used as energy input to the end-users.The total potential for heat recovery is calculated to 212 PJ per year (excluding natural energy sources) which correspond to 13% of the net energy input for end users and producers.The large potential is firstly within the transport (36%), secondly within utility (28%), industry (23%), buildings (11%) and finally the construction sector where the potential is relatively small.The potential for waste heat in the transport sector originates from exhaust gas (high temper-ature from 200°C to 400°C), engine and charge air cooling (low temperature below 80°C).In the utility sector, 43 % of the waste heat originates from condensate from steam power plants which is accessible at a temperature of 20 °C. The remaining 57 % of the waste heat originates primarily from exhaust gas at temperatures from 120°C to 180 °C.In the industrial sector 91 % of the waste heat is accessible at temperatures below 100°C. The low temperature waste heat originates mainly from evaporation, distillation, cooling/refrigeration and space heating.In the building sector the all the waste heat is accessible at temperatures below 100°C and originate primarily from refrigeration/cooling and exhaust from boilers.The potential of waste heat in the construction sector is estimated to be relatively low due the fact the majority of the installations are temporary.The potential for utilising “waste heat” from natural resources is theoretically close to infinite, but economically unfeasible. At the stage of completing the report, there has not been sufficient information to evaluate the low temperature potential that is also economically feasible, so the focus in this report is primarily regarding the temperatures from these natural resources. Solar can supply heat at temperatures up to 100°C, geothermal energy can supply heat at temperatures up to 90 °C and air/water average around 2°C during colder seasons and 17 °C in warmer seasons.When looking across all the sectors there are two major energy sources. One of them origi-nates from cooling/refrigeration, condensate and various industrial processes all below 60 °C and the other major waste heat source comes in the form of exhaust gas from various com-bustion and heating processes.