• Energy Research
• DE close
• Energy close
• Aurora Universities Network close

Computer-based simulations of Organic Rankine Cycles (ORC) have been extensively used in the last two decades to predict the behaviour of existing plants or already in the design phase. For time-varying heat sources, researchers typically rely on either quasi-steady state or dynamic simulations. In this work, the two approaches are compared and the trade-off between them is analysed, taking as benchmark waste heat recovery with ORC from a billet reheating furnace. The system is firstly optimized in MATLAB® using a quasi-steady state approach. The results are then compared with a corresponding dynamic simulation in Dymola. In the case of waste heat from billet reheat furnace, the quasi-steady state approach can successfully capture the fluctuations in waste heat. For heat source ramps from 110% to 40% the nominal value in 30 s, dynamic effects lead to 1.1% discrepancies in ORC net power. The results highlight the validity of the quasi-steady state approach for techno-economic optimization of ORC for industrial waste heat and provide a valuable guideline for developers, companies and researchers when choosing the most suitable tool for their analysis, helping them save time and costs to find the most appropriate approach.

Computer-based simulations of Organic Rankine Cycles (ORC) have been extensively used in the last two decades to predict the behaviour of existing plants or already in the design phase. For time-varying heat sources, researchers typically rely on either quasi-steady state or dynamic simulations. In this work, the two approaches are compared and the trade-off between them is analysed, taking as benchmark waste heat recovery with ORC from a billet reheating furnace. The system is firstly optimized in MATLAB® using a quasi-steady state approach. The results are then compared with a corresponding dynamic simulation in Dymola. In the case of waste heat from billet reheat furnace, the quasi-steady state approach can successfully capture the fluctuations in waste heat. For heat source ramps from 110% to 40% the nominal value in 30 s, dynamic effects lead to 1.1% discrepancies in ORC net power. The results highlight the validity of the quasi-steady state approach for techno-economic optimization of ORC for industrial waste heat and provide a valuable guideline for developers, companies and researchers when choosing the most suitable tool for their analysis, helping them save time and costs to find the most appropriate approach.

The transition in the energy market and the growing share of renewable energy sources have been boosting the research in new power cycles. For example, the concept of batch evaporation in the Misselhorn Cycle promises to increase the overall efficiency in low-temperature applications and therefore saves resources. In this paper, a dynamic evaporator model was extended in order to prove the feasibility of the Misselhorn Cycle despite its transient character. In this context, the thermal capacity of the wall material as well as the residence time of the heat source medium were added. The previous, underlying model predicted an improved system efficiency for the Misselhorn Cycle of about 50% compared to an Organic Rankine Cycle (ORC) at 100+C. Initially, the results of the extended model showed a negative influence of the inertial effects on the possible net power output (advantage over ORC only 10%). However, an unheated discharge phase and reduced dimensions of the heat exchanger could compensate these drawbacks and achieved results (about 40% better than ORC) in the same range as the previous, simple model predicted. These findings prove the general practical feasibility of the Misselhorn Cycle.The transition in the energy market and the growing share of renewable energy sources have been boosting the research in new power cycles. For example, the concept of batch evaporation in the Misselhorn Cycle promises to increase the overall efficiency in low-temperature applications and therefore saves resources. In this paper, a dynamic evaporator model was extended in order to prove the feasibility of the Misselhorn Cycle despite its transient character. In this context, the thermal capacity of the wall material as well as the residence time of the heat source medium were added. The previous, underlying model predicted an improved system efficiency for the Misselhorn Cycle of about 50% compared to an Organic Rankine Cycle (ORC) at 100+C. Initially, the results of the extended model showed a negative influence of the inertial effects on the possible net power output (advantage over ORC only 10%). However, an unheated discharge phase and reduced dimensions of the heat exchanger could compensate these drawbacks and achieved results (about 40% better than ORC) in the same range as the previous, simple model predicted. These findings prove the general practical feasibility of the Misselhorn Cycle.

The transition in the energy market and the growing share of renewable energy sources have been boosting the research in new power cycles. For example, the concept of batch evaporation in the Misselhorn Cycle promises to increase the overall efficiency in low-temperature applications and therefore saves resources. In this paper, a dynamic evaporator model was extended in order to prove the feasibility of the Misselhorn Cycle despite its transient character. In this context, the thermal capacity of the wall material as well as the residence time of the heat source medium were added. The previous, underlying model predicted an improved system efficiency for the Misselhorn Cycle of about 50% compared to an Organic Rankine Cycle (ORC) at 100+C. Initially, the results of the extended model showed a negative influence of the inertial effects on the possible net power output (advantage over ORC only 10%). However, an unheated discharge phase and reduced dimensions of the heat exchanger could compensate these drawbacks and achieved results (about 40% better than ORC) in the same range as the previous, simple model predicted. These findings prove the general practical feasibility of the Misselhorn Cycle.The transition in the energy market and the growing share of renewable energy sources have been boosting the research in new power cycles. For example, the concept of batch evaporation in the Misselhorn Cycle promises to increase the overall efficiency in low-temperature applications and therefore saves resources. In this paper, a dynamic evaporator model was extended in order to prove the feasibility of the Misselhorn Cycle despite its transient character. In this context, the thermal capacity of the wall material as well as the residence time of the heat source medium were added. The previous, underlying model predicted an improved system efficiency for the Misselhorn Cycle of about 50% compared to an Organic Rankine Cycle (ORC) at 100+C. Initially, the results of the extended model showed a negative influence of the inertial effects on the possible net power output (advantage over ORC only 10%). However, an unheated discharge phase and reduced dimensions of the heat exchanger could compensate these drawbacks and achieved results (about 40% better than ORC) in the same range as the previous, simple model predicted. These findings prove the general practical feasibility of the Misselhorn Cycle.

Abstract Increasing demand response (DR) from households, industry and tertiary sector may provide substantial flexibility in renewable-based energy systems, but the deployment of DR is currently limited. This study examines the future economic potential DR in the renewable rich northern European region, and also analyses power markets impacts of large-scale DR deployment in the region. For the quantifications, the energy system model BALMOREL is used, modified to include a detailed temporal modelling of available DR potentials. Results show that among the DR options analysed, space heating and water heating provide the highest shares of loads shifted. The overall demand response potential is particularly high in Norway and Sweden, due to wide-spread electric space- and water heating. Low variable costs make these DR applications economically feasible for deployment, despite high supply-side flexibility provided by regulated hydro power. DR may contribute to peak shaving of up to 18.6% of total peak load in 2050. Revenues from DR-application yield very different results depending on techno-economic parameters, potentials and the price volatility in the various analysed market areas. Results show an insignificant change in CO2 emissions between scenarios with and without demand response.

Abstract Increasing demand response (DR) from households, industry and tertiary sector may provide substantial flexibility in renewable-based energy systems, but the deployment of DR is currently limited. This study examines the future economic potential DR in the renewable rich northern European region, and also analyses power markets impacts of large-scale DR deployment in the region. For the quantifications, the energy system model BALMOREL is used, modified to include a detailed temporal modelling of available DR potentials. Results show that among the DR options analysed, space heating and water heating provide the highest shares of loads shifted. The overall demand response potential is particularly high in Norway and Sweden, due to wide-spread electric space- and water heating. Low variable costs make these DR applications economically feasible for deployment, despite high supply-side flexibility provided by regulated hydro power. DR may contribute to peak shaving of up to 18.6% of total peak load in 2050. Revenues from DR-application yield very different results depending on techno-economic parameters, potentials and the price volatility in the various analysed market areas. Results show an insignificant change in CO2 emissions between scenarios with and without demand response.

Energy system models often rely on assumptions about the infeed of renewable energies. Despite their significance, the renewable time series are often based on single weather years, selected without applying clear criteria. For planning purposes of photovoltaic plants or heating and cooling systems, it is common practice to artificially create weather years composed of months from different years. However, there are only few models for the composition of artificial weather years that represent a well-defined high- or low-infeed-scenario. A new method is proposed to artificially construct infeed time series on system level. Under the assumption of a normal distribution, we compose an infeed time series which aims at meeting a certain quantile of annual infeed. Thus, it is possible to construct different infeed scenarios, to model the inter-year variability of the renewable infeed. The method at hand can be useful for everyone who uses exogenous infeed time series in energy modeling.

Energy system models often rely on assumptions about the infeed of renewable energies. Despite their significance, the renewable time series are often based on single weather years, selected without applying clear criteria. For planning purposes of photovoltaic plants or heating and cooling systems, it is common practice to artificially create weather years composed of months from different years. However, there are only few models for the composition of artificial weather years that represent a well-defined high- or low-infeed-scenario. A new method is proposed to artificially construct infeed time series on system level. Under the assumption of a normal distribution, we compose an infeed time series which aims at meeting a certain quantile of annual infeed. Thus, it is possible to construct different infeed scenarios, to model the inter-year variability of the renewable infeed. The method at hand can be useful for everyone who uses exogenous infeed time series in energy modeling.