Final energy consumption in Switzerland for 2015 represented 232.8 TWh in total. Of which 18.5% (42.8 TWh) is due to industrial consumption only. The distribution of thermal needs within this sector consist of process heat (54.4%), space heating (9.9%) and hot water produc-tion (1.7%) which combined represent the main part of the total industrial energy consump-tion (66% or 28.4 TWh) [Kemmler et al., 2016]. Process heat only represents 23.3 TWh/year which is close to 10% of the final energy consumption in Switzerland.
Figure 2 offers a breakdown at subsector level showing which areas are dominant from a heat need point of view in the Swiss industries. The chemical field accounts for the most important consumption of process heat which represents 27% of that from all subsectors. Minerals (18%), food (14%) metals (13%) and paper (9%) industries also show large process heat needs. These five industries together add up to 81% of all process heat consumption in the country hence being the fields to target with the integration of high temperature heat pumps given their large potential.
The repartition of heat needs within industrial subsectors has been illustrated as a breakdown by temperature range for France [DuPont et al., 2009] and Germany [Wolf 2014]. The study by [Nellissen et al., 2015] shown in Figure 3 is based on data from 2012 gathered from 33 Eu-ropean countries where it identifies a potential for industrial heat pump application of 174 TWh under 150 °C. Important Swiss industrial sectors with large heat consumption show fol-lowing share of heat needs in the 100°- 150 °C range to total needs below 150 °C: 28% for food and tobacco, 46% for chemical, 11% for paper industries. These sectors show following proportion of needs below 150 °C compared to the total heat needs: 90% for food and to-bacco, 23% for chemical and 50% for the paper industry [Nellissen et al., 2015].
Figure 1: Final heat demand in the Swiss industry by subsector for 2015 in [TWh/yr]. Blue lines shows process heat needs; orange lines combine space heating and hot water needs of the industries [based on data for year 2015 from Kemmler et al 2016]
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Figure 2: European repartition of heat needs by industrial subsector based on 2012 data from 33 countries [Nellissen et al., 2015]
A detailed breakdown by type of process within each industrial subsector [Lauterbach, 2011]
shows that typical industrial heat demands between 100 °C and 140 °C originate from drying (food and beverages, paper, fabricated metal, rubber and plastic, textiles and wood), pasteuri-zation and sterilipasteuri-zation (food and beverages), distillation (chemicals), evaporating, cooking and thickening (food and beverages, chemicals), surface treatment (machinery and equip-ment), coloring (textiles) and compression (chemicals, wood).
Waste heat can be found in various forms: diffuse, liquid or gaseous effluents. Diffuse heat is difficult to collect but liquids and gases offer a more accessible recovery [ADEME , 2015].
The thermal level given from the effluents can be heightened through the use of heat pumps in order to provide heating either to the same or a different process on site or else to pre-heat air, water or raw materials. Sources from which waste heat can be collected under 100 °C are cooling water come from air compressors and cold production, ovens and metalwork pieces.
Gaseous effluents include hot air from drying, compressors, cooling and end of process vapor or flash steam. A fraction of flue gazed can also be used at these temperatures [ADEME, 2015].
The higher temperature level of waste heat compared to this of ambient air or ground heat makes it an attracting source providing better COP for heat pumps and as the case may be also a steady supply during the year. The bottleneck however regarding the real reachable po-tential of IHP application identified in the previous section is the amount of heat available in the effluents. If waste heat is lacking in the proper temperature levels than the application of heat pumps is compromised. The quantity of heat provided at the condenser is however greater than that of the heat source due to the energy transmitted to the compressor which is COP dependent.
Evaluating the amount of waste heat by subsector and temperature level is a difficult task un-less a large scale study gathering inputs from numerous industries is conducted. Some pro-jects of this nature took place in Canada [Innovagro consultants, 2011], France [DuPont and Sapora, 2009], Norway [Enova, 2009] and also for the Swiss canton of Valais [CREM, 2012].
The most relevant information from a high temperature heat pump integration point of view is presented below.
In Switzerland, a thermal waste cadaster was set up by canton of Valais [CREM, 2012]. It is based on data collected from close to 200 industries. Information gathered cover type of efflu-ent (gaseous, liquid, and solid), seasonality and qualification of the effluefflu-ent (temperature
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level). The georeferenced data was put together and displayed on a map thus further allowing identification of possible synergies between industries or with residential areas to supply heat needs via a district heating network.
Various valorization paths were selected. A large potential above 600 GWh/year was identi-fied for district heating and takes into account effluents of 85°C up to 100°C. The share of ef-fluents which can be used for heating or hot water production amounts to 16 GWh/year and lies between 50 °C and 60 °C. The largest potential of 941 GWh/year was identified between 10 °C and circa 50 °C for heat pump application. A combination of effluents from these dif-ferent temperature levels could be used as a source for high temperature industrial heat pumps. Use of waste heat is already applied by 23 companies who took part in the survey.
The recovered energy represents a total of 522 GWh/year worth of electricity and heat com-bined. This high value accounts for one third of the whole potential.
In France, a study compared heat demand at 60 °C – 140 °C with available heat sources at 35 -70 °C [Dupont et al., 2009] according to various industrial subsectors. Results show that four industrial sectors should be able to cover their needs in process heat between 60 °C to 140 °C using waste heat: food products and beverages (104% coverage rate), dairy (109%), transport equipment (127%) and cement, lime and plaster (131%). The sugar industry presented sepa-rately from the food subsector shows the least interest of all (0.08%). These results are en-couraging since food and dairy as well as the mineral industry make up a large part of the Swiss process heat consumption. Pulp, paper and paper products show a limited perspective with 6% coverage rate opportunity. Iron based metal work could cover 9% of its needs through waste heat valorization. The chemical sector has not been evaluated. The authors mention that care should be taken about the possibility of existing recovery equipment which aren’t ta en into account.
Norwegian study [Enova, 2009] has collected information on waste heat from 72 industries which represent 63% of the energy consumption in the country. The share of water, vapor and exhaust are given as percentage of the energy use by subsector. In the chemical field 157% of total energy accounts for in waste heat. This can be explained by exothermal reactions taking place in this specific subsector. The total waste heat available in the food sector amounts to 15%. The total waste heat potential identified for all sectors represents 35.8% of the final in-dustrial energy use. his value can’t be used as such and applied to the Swiss industry be-cause the industrial landscape isn’t ali e. However this high value is promising.
The temperature level at which the waste heat is available is key for IHP application. The chemical field which showed an interesting potential in terms of waste heat quantity sees 76.6% of its effluents temperature situated between 40 °C and 60 °C which would corre-sponds to ’ GWh/yr applied to Switzerland. The food industry has 30.5% available waste heat between 40 °C and 60 °C which corresponds to 153 GWh/yr applied to Switzerland and an additional 18% between 60 °C and 140 °C. The pulp and paper industry shows good poten-tial with 49.1% of its effluents being between 40 °C and 60 °C (459 GWh/yr). Metal indus-tries show various potentials. While recovery potential for aluminum mostly lies between 60
°C and 140 °C and under 40 °C, in the iron and steel industries mostly shows waste heat above 140 °C but also 18.6% in the 40 °C to 60 °C range. As for the cement and leca subsec-tor, its process needs are situated at very high temperatures which is reflected in the waste heat available above 140 °C only. With the hypothesis of a COP value of 3, the coverage rate of the corresponding needs in the range 100-150 °C defined above is approximately of 25%
for the food sector, 300% for the pulp and paper and 390% for the chemical field. These result shows different trends than these presented by [Dupont et al., 2009] but the temperature ranges were also based on other references. This highlights the need for caution in using global statistics and stresses the requirement for specific data on the area covered by a study.
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