TRNSYS Research Articles

A Projective Integration Method for Transient Stability Assessment of Power Systems With a High Penetration of Distributed Generation

The impact of numerous distributed generators (DGs) coupled with the implementation of virtual inertia on the transient stability of power systems has been studied extensively. Time-domain simulation is the most accurate and reliable approach to evaluate the dynamic behavior of power systems. However, the computational efficiency is restricted by their multi-time-scale property due to the combination of various DGs and synchronous generators. This paper presents a novel projective integration method (PIM) for the efficient transient stability simulation of power systems with high DG penetration. One procedure of the proposed PIM is decomposed into two stages, which adopt mixed explicit-implicit integration methods to achieve both efficiency and numerical stability. Moreover, the stability of the PIM is not affected by its parameter, which is related to the step size. Based on this property, an adaptive parameter scheme is developed based on error estimation to fit the time constants of the system dynamics and further increase the simulation speed. The presented approach is several times faster than the conventional integration methods with a similar level of accuracy. The proposed method is demonstrated using test systems with DGs and virtual synchronous generators, and the performance is verified against MATLAB/Simulink and DIgSILENT PowerFactory.

Energy Performance and Environmental Impact of an Active Domestic Solar Water Heater in Maghreb Arab Union Countries

In this paper, an active domestic solar water heater is modeled under the climate conditions of five cities of Maghreb Arab Union countries by using Transient System Simulation Software Program. The aim is to evaluate the energy saving, payback period as an economic indicator, and the environmental benefit in reduction of greenhouse gases. Depending on the climate zone, it is found that the system has the potential to save annually between 3506-4130 kWh with a mean annual solar fraction between 71-100 % and has a payback period of 9.07-27.48 years. Another benefit of using the proposed system is the environmental issue; which results in reducing CO2 emission by an amount between 2-3.8 tCO2. These variations between can be attributed to the energy considerations in each country.

Design and Analysis of Integrating the Solar Thermal energy in Anaerobic Digester using TRNSYS: Application kenitra-Morocco

The aim of this research was to design a solar heated system to enhance the anaerobic digestion treatment at mesophilic condition for the UASB (Up flow Anaerobic Sludge Blanket) digester system, the solar energy absorbed by flat plate collectors was transferred to heat storage tanks, which continuously supplied an anaerobic reactor with water at a maximum temperature of 37°C. For this purpose, we have developed two models for a 70 l bio-digester coupled to a solar thermal system (low temperature) using the TRNSYS (Transient System Simulation) platform. The thermal performances and the dynamic behavior of the systems under the climatic conditions of the city of Kenitra-Morocco are studied and the two designs were compared between each other in order to optimize the systems which have an excellent thermal performance.

Investigation of Heat Pump Operation Strategies with Thermal Storage in Heating Conditions

A heat pump with thermal storage system is a system that operates a heat pump during nighttime using inexpensive electricity; during this time, the generated thermal energy is stored in a thermal storage tank. The stored thermal energy is used by the heat pump during daytime. Based on a model of a dual latent thermal storage tank and a heat pump, this study conducts control simulations using both conventional and advanced methods for heating in a building. Conventional methods include the thermal storage priority method and the heat pump priority method, while advanced approaches include the region control method and the dynamic programming method. The heating load required for an office building is identified using TRNSYS (Transient system simulation), used for simulations of various control methods. The thermal storage priority method shows a low coefficient of performance (COP), while the heat pump priority method leads to high electricity costs due to the low use of thermal storage. In contrast, electricity costs are lower for the region control method, which operates using the optimal part load ratio of the heat pump, and for dynamic programming, which operates the system by following the minimum cost path. According to simulation results for the winter season, the electricity costs using the dynamic programming method are 17% and 9% lower than those of the heat pump priority and thermal storage priority methods, respectively. The region control method shows results similar to the dynamic programming method with respect to electricity costs. In conclusion, advanced control methods are proven to have advantages over conventional methods in terms of power consumption and electricity costs.

Simulation of a biomimetic façade using TRNSYS

Biomimicry – innovation inspired by nature – is a creative methodology that translates characteristics from the biological world to the domain of human technology. Functional biomimicry offers opportunities to advance the development of flexible building facades. Following biomimetic principles, external fur and bioheat transfer (blood perfusion) and were combined into a mathematical model of a commercial office building façade for a west-facing wall of an office building situated in Melbourne, Australia. TRaNsient SYstem Simulation (TRNSYS) software tool was used to determine temperatures and heat transfer of this biomimetic façade in summer design conditions compared to a reference. The biomimetic façade was simulated to provide cooling of greater than 50Wm−2 and reduced mean surface temperatures in the occupied zone by 2.8°C, compared with the reference.

Envelope Design Optimization by Thermal Modelling of a Building in a Warm Climate

Finding the most appropriate configuration of building components at the design stage can reduce energy consumption in new buildings. This study aims to optimize the design of the envelope of a new residential building located in a warm climate (southern Italy). The thermal behaviour of the building has been analysed to evaluate the indoor operative air temperature for several configurations. The building prototype has been modelled using the dynamic simulation software TRNSYS 17 (A transient system simulation program, University of Wisconsin, Solar Energy Laboratory, USA, 2010) using a sequential search technique. Starting from the simplest building configuration, the main evaluated components are: walls, slab-on-ground floor, roof, shading, windows and internal heat loads. For each of these components, different design options have been modelled and compared in terms of indoor thermal comfort. Comfort parameters have also been taken into account to evaluate users’ satisfaction with the optimized configurations. The study of the operative air temperature demonstrates that the absence of insulating layers in the ground floor ensures a lower internal temperature in summer. The paper shows how each component impacts the thermal behaviour of the whole building. It highlights the usefulness of the envelope design optimization that is characterized by high values of heat storage capacity, enabling internal temperature fluctuations to be kept under control, especially during summer.

Performance of Radiant Heating Systems of Low-Energy Buildings

After the introduction of plastic piping, the application of water-based radiant heating with pipes embedded in room surfaces (i.e., floors, walls, and ceilings), has significantly increased worldwide. Additionally, interest and growth in radiant heating and cooling systems have increased in recent years because they have been demonstrated to be energy efficient in comparison to all-air distribution systems. This paper briefly describes the heat distribution systems in buildings, focusing on the radiant panels (floor, wall, ceiling, and floor-ceiling). Main objective of this study is the performance investigation of different types of low-temperature heating systems with different methods. Additionally, a comparative analysis of the energy, environmental, and economic performances of floor, wall, ceiling, and floor-ceiling heating using numerical simulation with Transient Systems Simulation (TRNSYS) software is performed. This study showed that the floor-ceiling heating system has the best performance in terms of the lowest energy consumption, operation cost, CO2 emission, and the nominal boiler power. The comparison of the room operative air temperatures and the set-point operative air temperature indicates also that all radiant panel systems provide satisfactory results without significant deviations.

Experimental study on the shading performance of a window integrated with grid shading configuration

The aim of the current article is to investigate the shading performance resulted from windows integrated with grid shading configuration and air gap. First, a geometric method based on a light tracing algorithm was presented in order to evaluate the shading performance of complex fenestration system. The consequential energy consumption of a typical residential building structure with complex window system was analyzed. Then a scale experiment setup was built to validate the geometric method. Transient System Simulation Program (TRNSYS) or experiment method is not applicable in the case of complex configurations, and, therefore, the geometric method is an acceptable alternative way to evaluate the shading performance of such window systems. According to the comparison between window surface temperature and indoor air temperature, the window with an air gap and grid shading configuration were proved to be capable of achieving a better thermal insulation in buildings and be more energy efficient. Finally, based on the geometric method, a detailed parameter analysis on grid shading configuration was also conducted. The optimal shading configuration size was discussed, for the specified typical residential building structure applied in the current article, the optimal grid shading configuration in Shanghai (warm–humid climate zone) is pitch to width ratio = 6, which could efficiently improve the energy systems by 38%.

Assessment of Natural Ventilation Potential for Residential Buildings across Different Climate Zones in Australia

In this study, the natural ventilation potential of residential buildings was numerically investigated based on a typical single-story house in the three most populous climate zones in Australia. Simulations using the commercial simulation software TRNSYS (Transient System Simulation Tool) were performed for all seasons in three representative cities, i.e., Darwin for the hot humid summer and warm winter zone, Sydney for the mild temperate zone, and Melbourne for the cool temperate zone. A natural ventilation control strategy was generated by the rule-based decision-tree method based on the local climates. Natural ventilation hour (NVH) and satisfied natural ventilation hour (SNVH) were employed to evaluate the potential of natural ventilation in each city considering local climate and local indoor thermal comfort requirements, respectively. The numerical results revealed that natural ventilation potential was related to the local climate. The greatest natural ventilation potential for the case study building was observed in Darwin with an annual 4141 SNVH out of 4728 NVH, while the least natural ventilation potential was found in the Melbourne case. Moreover, summer and transition seasons (spring and autumn) were found to be the optimal periods to sustain indoor thermal comfort by utilising natural ventilation in Sydney and Melbourne. By contrast, natural ventilation was found applicable over the whole year in Darwin. In addition, the indoor operative temperature results demonstrated that indoor thermal comfort can be maintained only by utilising natural ventilation for all cases during the whole year, except for the non-natural ventilation periods in summer in Darwin and winter in Melbourne. These findings could improve the understanding of natural ventilation potential in different climates, and are beneficial for the climate-conscious design of residential buildings in Australia.

Modeling and simulating urban outdoor comfort: Coupling ENVI-Met and TRNSYS by grasshopper

In urban areas the impact of built environment on wellbeing and human health should be considered due to urban heat island phenomenon. The present research aims at identifying a method for an accurate estimation of thermal outdoor comfort and mean radiant temperature, modeling and simulating the effects of urban form and vegetation on microclimate of cities. In order to reach this main objective, this research incorporates CFD based simulation tool ENVI-met and TRNSYS (Transient Systems Simulation) by means of Grasshopper. The results of the study demonstrate the reliability of the proposed method, i.e. that a combination of ENVI-met and TRNSYS increases the simulation accuracy in terms of outdoor thermal comfort, especially during night. This method allows exploiting the potentialities of both ENVI-met and TRNSYS for the calculation of urban features (urban form, vegetation, canyon proportion, etc.) affecting urban microclimate.

Power System Transient Stability Analysis Using Hybrid Model Based on the Finite Element Method

This paper presents a simple, but very powerful, numerical algorithm for the power system transient stability simulation. The aim of this paper is to fill the gap between the Transient Stability Programs (TSP) and the Electromagnetic Transient Programs (EMTP) by developing a new simulation tool based on the finite element (FE) representation of the power system element. The proposed hybrid model based on the Finite Element Method (FEM) allows us to avoid disadvantages of TSP comparing to EMTP that leads to the simulation of the electromechanical transients in a more accurate and efficient way. In order to show the principles of the proposed method in details, the proposed numerical method has been tested and compared to the solutions obtained by the well known and established EMTP simulation tool where a very good correlation has been demonstrated.

The effects of climate change on heating energy consumption of office buildings in different climate zones in China

Climate plays an important role in heating energy consumption owing to the direct relationship between space heating and changes in meteorological conditions. To quantify the impact, the Transient System Simulation Program software was used to simulate the heating loads of office buildings in Harbin, Tianjin, and Shanghai, representing three major climate zones (i.e., severe cold, cold, and hot summer and cold winter climate zones) in China during 1961–2010. Stepwise multiple linear regression was performed to determine the key climatic parameters influencing heating energy consumption. The results showed that dry bulb temperature (DBT) is the dominant climatic parameter affecting building heating loads in all three climate zones across China during the heating period at daily, monthly, and yearly scales (R 2 ≥ 0.86). With the continuous warming climate in winter over the past 50 years, heating loads decreased by 14.2, 7.2, and 7.1 W/m2 in Harbin, Tianjin, and Shanghai, respectively, indicating that the decreasing rate is more apparent in severe cold climate zone. When the DBT increases by 1 °C, the heating loads decrease by 253.1 W/m2 in Harbin, 177.2 W/m2 in Tianjin, and 126.4 W/m2 in Shanghai. These results suggest that the heating energy consumption can be well predicted by the regression models at different temporal scales in different climate conditions owing to the high determination coefficients. In addition, a greater decrease in heating energy consumption in northern severe cold and cold climate zones may efficiently promote the energy saving in these areas with high energy consumption for heating. Particularly, the likely future increase in temperatures should be considered in improving building energy efficiency.

Building-scale experimental validation of a new model for walls with phase change materials

The current article presents the building-scale experimental validation of a new model for walls equipped with phase change materials. The one-dimensional conduction heat transfer equation is solved using an explicit finite-difference method coupled with an enthalpy method to consider the variable phase change materials thermal capacity. The model is implemented in the transient system simulation tool simulation tool and referred to as Type 3258, and the method used to couple this component to the multi-zone building (known as Type 56) is discussed. The experimental investigation is performed in two identical full-scale test-cells (only one with phase change materials) exposed to the ambient environment. Experimental data are first used to benchmark a transient system simulation tool simulation model of the test-cell without phase change materials. After calibration, the phase change materials model is experimentally validated with data from the phase change materials-equipped test-cell. Compared to the benchmarking procedure (without phase change materials), the root mean square deviation values between the experiments and the simulations (with phase change materials) are lower or in the same order of magnitude. Simulation accurately reproduces the impact of adding phase change materials to the test-cell as observed in the experiments, such as mitigation and time-shift effects. A discussion about computation time concludes the present study.

Simulation of solar cooling system based on variable effect LiBr-water absorption chiller

In solar absorption cooling system, the instability of solar power causes mismatch between the solar collector and the absorption chiller. The variable effect absorption cycle was proposed to improve this. In order to investigate its solar driving performance, a Compound Parabolic Collector (CPC) driving variable effect LiBr-water absorption cooling system is simulated. Model of the variable effect LiBr-water absorption chiller is built through artificial neural network (ANN) modeling based on 450 groups of experimental data. Good agreement between the prediction and experimental data is achieved with correlation coefficient of 0.994. The CPC driving absorption cooling system is then built in TRaNsient SYstem Simulation program (TRNSYS) based on the chiller model. The daily performance of this system is calculated and analyzed. The variable effect chiller can work with low driving temperature, which guarantees a long working period. Besides, the variable effect chiller has high COP under high driving temperature, which ensures a competitive overall efficiency. The calculation shows that average chiller COP of 0.88 and solar COP of 0.35 are obtained. The effects of solar collector area, storage tank volume and cut-off driving temperature on the system performance are analyzed. The optimal solar collector area and tank volume are obtained.

Performance analysis and economic assessment of solar thermal and heat pump combisystems for subtropical and tropical region

In the present research, combinations of solar collectors and air-source heat pumps for domestic hot water (DHW) are addressed in terms of hydraulic layout and climate conditions. TRaNsient SYstems Simulation (TRNSYS) software was implemented to simulate and examine the heating capacities of various DHW systems. For validating the numerical results, a demonstration site featuring a solar collector and heat pump combisystem with real-time monitoring sensors was established in Tainan, Taiwan. The corresponding parameters of TRNSYS modules were also tested and validated using experimental data. For comparison with the electrical heating water system, three common DHW systems—a conventional solar DHW system, a single-tank solar combisystem, and a dual-tank solar combisystem—were selected, and their technical and economical aspects were assessed. To determine the effect of climate conditions, two metropolitan cities in Taiwan were simulated: Taipei represented subtropical cities and Kaohsiung represented tropical cities. Results for both Taipei and Kaohsiung showed that the dual-tank solar combisystems had the lowest electrical consumption levels and operating costs. The incremental capital costs of the solar combisystems were considered, and realistic payback periods were calculated to determine economic feasibility.

Experimental evaluation of a triple-state sorption chiller

This paper presents the experimental testing results of a novel triple-state sorption chiller with integrated cold storage. The performance of the chiller was measured for hot water inlet temperatures between 65 °C and 95 °C, heat rejection inlet temperatures between 15 °C and 35 °C, and chilled water inlet temperatures between 10 °C and 25 °C. An empirical model was developed for implementation in the TRaNsient SYstem Simulation (TRNSYS) software. To validate the model, a five-hour experimental charge test was conducted during which the hot water and heat rejection inlet temperatures were continuously varied. The model was able to predict the total heat input and heat rejection energy to within 0.7% and 1.3% of the experimentally measured values, respectively.

Multiscale Simulation of Power System Transients Based on the Matrix Exponential Function

Power system electro-magnetic transient programs (EMTP) have been popular among researchers and practitioners due to their detailed component modeling and high simulation accuracy for complex system operations. Despite broad applications in simulations with wide range of timescales, the small discretization step of these programs makes their use very time-consuming for system studies with long time span. Facing the increasingly complex power system transient characteristics and simulation demands, a multiscale algorithm that integrates the simulations of the electromagnetic and slower electromechanical transients is desirable. The multiscale simulation algorithm preserves the high fidelity of the EMTP and attains higher efficiency for the overall transient simulation. In this paper, we achieve this goal by exploiting the unique properties of the matrix exponential function. The proposed algorithm is capable of utilizing large step sizes to speed up the simulation of slow dynamics, whereas the fast transients are accurately reconstructed through efficient dense output mechanism, which is built upon the matrix exponential function computation. Numerical studies including a large-scale wind farm simulation are conducted to demonstrate the effectiveness of the proposed multiscale algorithm.

Experimental and numerical studies to assess the energy performance of naturally ventilated PV façade systems

This paper presents a holistic approach to assess the energy performance of a naturally ventilated PV façade system. A rigorous combined experimental and numerical approach is established. The real energy performance of the system has been evaluated through a long-term high resolution monitoring of a typical ventilated PV façade system. A numerical model based on TRaNsient SYstem Simulation (TRNSYS) package was developed to assess the thermal and energy performance of the system, which has been verified by a series of statistical analysis using the data collected from the experiment. The validated model was then used to assess the energy and thermal performance of a 7.4kWp prototype ventilated PV façade system in Izmir, Turkey. The results of this study demonstrated that ventilation in the air cavity of the PV façade system could significantly improve energy performance of the system even in a southeast facing façades. The quantitative analysis provides useful guidance to the system designers for the improvement of energy efficiency of the PV facade system.

A new local pressure loss coefficient model of a duct tee junction applied during transient simulation of a HVAC air-side system

Most of the local pressure loss coefficient (LPLC) models for duct fittings used in heating, ventilation and air conditioning (HVAC) air-side system transient simulations are simplified. The LPLCs are defined as having a constant value at the rated flow condition or as having a polynomial function of the flow ratio (or velocity ratio). To determine the influence of these simplifications, this study used a diverging tee junction as an example. First, we performed CFD calculations to generate a new LPLC dataset and trained a data-driven model using feature weighted support vector regression (FWSVR) combined with particle swarm optimization (PSO-FWSVR). Finally, we compared this new LPLC model with the two traditional models at the level of both individual junction and air-side system. The results show that the accuracy of the new model is greatly improved and the LPLC model can have a significant impact on the system operation condition.

Influence of voltage harmonics on transformer no-load loss measurements and calculation of magnetization curves

This paper investigates the voltage distortion phenomenon during no-load testing of transformers, its influence on no-load loss calculations, and a novel measurement technique that is unaffected by harmonics for obtaining transformer magnetization curves. Owing to economic reasons, no-load loss correction for distorted test waveforms has been addressed to some extent in existing standards, while not much has been done on the aspect of calculation of magnetization characteristics. This is important for parameter estimation and transformer modeling in power system transient simulations. Results from two test cases are presented, one is based on factory testing with 290-MVA, three-phase, three-legged power transformer and second is a more comprehensive analysis using a laboratory test setup with a 22-kVA single-phase transformer. Application of loss correction equations and limits based on existing testing standards was evaluated and found to result in overcompensation, while calculation of magnetization curves based on existing methods resulted in error up to 20%. Whereas, application of proposed measurement technique based on voltage “Zero-Crossing” detection is shown to result in negligible error. The proposed measurement technique uses the same input signals as in a standard no-load test procedure. Hence, it can be easily implemented in parallel with existing instrumentation.