In this paper, the thermodynamic and economic efficiency of three different heat supply processes are compared, based on exergy flows and costs of heat. A gas turbine process with a heat recovery boiler, a gas and steam turbine combined cycle process and a high temperature heat pump system recovering waste heat are analysed. The aim is to provide heat as 4 bar(abs) saturated steam. The economic analysis bases on the comparison of the consumption-related costs of heat, the capital-related costs of heat, and the operation-related costs of heat. The results show that the heat pump system has higher exergetic efficiency than the gas turbine or the gas turbine combined cycle process. For the consumption related costs, the economic calculation shows that the operation of a heat pump, working with a coefficient of performance of four and for a natural gas price of 25 €/MWh, is the cheapest way of heat production as long as the electricity price is lower than 45 €/MWh. For the period from January 2013 until June 2016 the total costs of heat, based on real gas and electricity prices from the European Energy Exchange, are calculated and analysed. The results show that the share of heat provided by the heat pump system varies between 45% and 76%. Especially in 2013 and 2014, the economic conditions for operating heat pumps were very good. Since October 2015 the natural gas prices have seen a decrease which favours industrial heat supply with combined heat and power systems.

Increasing demands on mobility and transport, but limited space above ground, lead to new traffic routes being built, even more underground in the form of tunnels. In addition to improving the traffic situation, tunnels offer the possibility of contributing to climate-friendly heating by indirectly serving as geothermal power plants. In this study, the geothermal potential of the future longest railway tunnel in the world, the Brenner Base Tunnel, was evaluated. At the Brenner Base Tunnel, warm water naturally flows from the apex of the tunnel towards the city of Innsbruck, Austria. In order to estimate its geothermal potential, hydrological data of discharge rates and temperatures were investigated and analyzed. The investigations indicated the highest geothermal potential in the summertime, while the lowest occurs during winter. It could be shown that these variations were a result of cooling during discharge through areas of low overburden (mid mountain range), where the tunnel atmosphere is increasingly influenced by the air temperatures outside the tunnel. Nevertheless, the calculations showed that there will be a usable potential after completion of the tunnel.

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SummaryThree different process types of heat supply for industrial production processes requiring low temperature heat at 140°C are analyzed and compared with each other. The thermodynamic and economic efficiency of a gas turbine process with a heat recovery boiler (GT), a gas and steam turbine combined cycle process with a back-pressure turbine (GT-CC) and a high temperature heat pump (HTHP) system recovering waste heat from humid exhaust air between 90°C and 50°C are assessed based on energy flows, exergy flows and costs of heat provided as 4 bar (abs) saturated steam. The economic analysis bases on the comparison of the consumption-related costs of heat, the capital-related costs of heat and the operation-related costs of heat. The payback-times are calculated for different HTHP investment cost levels (1000 EUR/kWQ, 750 EUR/kWQ, 500 EUR/kWQ and 250 EUR/kWQ). To evaluate the effects of fluctuating energy costs, a sensitivity analysis with varying gas and electricity prices has been carried out.The results show that the HTHP system, even with modest performance assumptions, has a higher exergetic efficiency than the GT or the GT-CC process. For the consumption-related costs, the economic calculation shows that the operation of a HTHP, working with a coefficient of performance (COP) of four and for a natural gas price of 25 EUR/MWh, is the cheapest way of heat production as long as the electricity price is lower than 45 EUR/MWh. An electricity price above 45 EUR/MWh makes a GT-CC process more favorable. For the period from January 2013 until June 2016, the total costs of heat and the payback times, based on real gas and electricity prices from the EEX, are calculated and analyzed. For overall cost-optimized heat supply, the results show that the share of heat provided by the HTHP system varies between 45% and 76% between January 2013 and June 2016. Especially in 2013 and 2014, the economic conditions for operating heat pumps were very good. Since October 2015, the natural gas prices have seen a decrease and the economic conditions shifted again favoring the industrial heat supply with combined heat and power systems.

Die Energie ist eine grundlegende physikalische Größe, die in allen bekannten Betrachtungsebenen auftritt und deren Einheit das Joule 1 (1 J) ist. Das Wort Energie kommt aus dem Griechischen und bedeutet "innen wirken", in diesem Sinne die Eigenschaft eines Systems (Körper, Stoff, Mechanismus), aus sich heraus eine bestimmte Wirkung zu entfalten. Beispiele dafür sind gespannte Federn, aufgeladene Batterien, chemisch gebundene Energie in Brennstoffen oder die bei der Kernfusion in Sternen, wie unserer Sonne, freigesetzte nukleare Energie. Die Energie hat grundlegende Bedeutung in biologischen Systemen (Energiezufuhr mit Nahrung) und in unserer Zivilisation (Energienutzung). 5.1.1.2 Energienutzung in der Menschheitsgeschichte Neben der Energiezufuhr über die Nahrungskette hat die Menschheit vor rund 500.000 Jahren begonnen, das Feuer kontrolliert zu nutzen. Dabei wird chemische Brennstoffenergie durch Reaktion mit Luftsauerstoff als Wärme freigesetzt, die aufgrund der hohen Reaktionstemperaturen teilweise als sichtbares Licht abgestrahlt wird. Durch die Verwendung von Feuer stieg der Lebensstandard der Menschen (künstliches Licht, Wärme), und es eröffneten sich neue technologische Möglichkeiten (Bearbeitung von Holz, Stein, Metallverarbeitung). Bis heute geht die zivilisatorische Entwicklung der Menschheit einher mit dem verstärkten Einsatz von Energie. Wind-und Wasserkraft werden seit Jahrhunderten für Mühlen und Bewässerungsanlagen genutzt. Wer über Energie verfügt, kann meist besser leben. Heute sorgt in den industrialisierten