TRNSYS Software Research Articles

Operating characteristics of photovoltaic/thermal–ground source heat pump system in cold regions

To investigate the operating performance of photovoltaic thermal integrated heat pumps in terms of the effects of the control strategy and the component parameters, this paper considers an office building in Zhengzhou city as the research object. A photovoltaic/thermal integrated ground source heat pump system model is established using TRNSYS software. Using this model, a system is developed with four operating modes based on temperature differences and seasonal control. The soil temperature, the unit energy consumption, and the solar energy guarantee rate are used as indicators to study the soil’s thermal balance and the energy consumption characteristics of the model system in the four operating modes. The effects of the control strategy design and the photovoltaic/thermal collector area on the system performance are analyzed, and the annual cost method is used to evaluate the system’s economy. The research results indicate that the tank heating mode’s closing temperature increased from 47 °C to 49 °C, the system energy consumption and power generation were reduced by 1.86 % and 1.24 %, respectively, and the instances of unsatisfied demand for domestic hot water were reduced by 19.05 %. The soil temperature increased gradually with increasing photovoltaic/thermal collector area, but the rate of this increase slowed down at larger areas; when the area increased from 50 m2 to 100 m2, the soil temperature increased by 16.6 %, but when the area increased from 200 m2 to 250 m2, the temperature then only increased by 10.6 %. In addition, there is a specific photovoltaic/thermal collector area that can maintain the soil temperature in equilibrium. When compared with a solar-assisted ground source heat pump heating system, the photovoltaic/thermal integrated ground source heat pump heating system can save 63.2 % in terms of operating costs and can reduce the annual cost by 60.9 % over a 10-year period. The research results show that the law of the photovoltaic/collector area affects the soil heat balance, and also provide data support for promotion of photovoltaic/thermal integrated ground source heat pump systems from both performance and economic perspectives.

Numerical simulation of the thermal behavior of Silica Aerogel in a commercial building in Tunisia

In order to ensure energy savings and improve occupant comfort in a building, it is necessary to explore passive approaches such as optimizing insulation, orientation and the choice of appropriate materials. Among these materials are Silica Aerogel, capable of playing an insulating role while maintaining energy performance. The objective of this study is to simulate the dynamic thermal behavior of an administrative office model with and without Silica Aerogel material using TRNSYS software. The office temperature is assumed to vary over time or imposed at the set temperature. The results show that the influence of different parameters (meteorological temperature, the composition of a wall, the solar flux density and the indoor air set temperature) and the nature of the walls (with insulation (Silica Aerogel) and without insulation) have a significant effect on the thermal behavior of a tertiary building and on energy consumption in heating or air conditioning mode.

Novel design of a CCHP system to boost nearly zero-carbon building concept

The accumulation of carbon dioxide in the atmosphere is responsible for global warming. To address this issue, this study develops and optimizes a novel and economically viable combined cooling, heating, and power (CCHP) system for an educational building with minimal CO2 emissions. The main components of the system include a gas turbine cycle, a molten carbonate fuel cell, a heating system, an electric chiller, and an absorption chiller. Optimization is conducted based on a 4E (energy, exergy, economic, and environmental) analysis using TRNSYS and MATLAB software. The optimized CCHP system has a unit product cost of $52.44/h with an overall exergy efficiency of 44.34 %, generating 0.39 kg of CO2/kWh. Furthermore, the objective of a nearly zero-carbon system is achieved by integrating carbon capture and storage (CCS) into the original CCHP system. A novel cryogenic carbon capture unit is implemented to capture CO2 from the flue gas. Integrating CCS reduces CO2 emissions by up to 91 %, presenting a cost-effective approach to carbon offset. Although there is a modest increase in operational costs ($53.46/h) and a slight decrease in exergy efficiency (43.3 %), these trade-offs are necessary to attain an environmentally responsible system. Overall, the optimized CCHP system with the integrated CCS shows potential as an energy-efficient solution for the selected educational building while reducing CO2 emissions.

Solar-powered adsorption desalination utilizing composite silica gel with a humidification-dehumidification desalination system

This work comes in light of addressing crises of freshwater scarcity, energy demand, and climate change to investigate innovative configurations of hybrid adsorption desalination integrated with a humidification dehumidification system powered by solar energy or waste heat in four operation modes. The investigation includes economic cost analysis and system performance using raw silica gel and silica gel/CaCl2 adsorbents under the weather data of Assiut-Egypt. System performance has been evaluated regarding daily water production, gain output ratio, and cooling effect using TRNSYS and MATLAB software. The combined configuration with heat recovery (the fourth mode) using silica gel/CaCl2 gives a relatively high freshwater production (69 m3/ton.day in June) compared with the basic adsorption desalination system using raw silica gel (7.1 m3/ton.day in June). Silica gel/CaCl2 in the first mode presented the highest cooling effect (555 W/kg) in June compared with silica gel in the primary system (197 W/kg). The third configuration's solar-powered silica gel/CaCl2 system shows a clear superiority of 1.8 in gain output ratio, compared with the basic system with and without heat recovery (0.54 and 0.4, respectively). The third configuration also provided the cheapest freshwater production among all configurations at 2 $/m3 in June.

Research on the optimization of the clean heating system for regional residential buildings based on the multi-objective optimization strategy

For the residential building district heating (RBDH) system, choosing the appropriate combination of heat sources according to local conditions is the key to improving economic efficiency. In this study, three climatic regions in China were selected, namely, a hot summer and cold winter region, cold region, and severe cold region. Among them, Nanjing, Tianjin, and Shenyang were selected as typical representative cities in the hot summer and cold winter region, cold region, and severe cold region, respectively. Taking the levelized cost of heat (LCOH) as the economic evaluation index and considering the carbon emission cost of the system operation, the energy consumption and the CO2 emissions were analyzed. TRNSYS software was used to simulate and analyze the system performance. The multi-objective optimization based on a genetic algorithm was proposed to optimize system parameters. From an economic point of view, the SA system was suitable for the hot summer and cold winter region, the SAS system was suitable for the cold region, and the SE system was suitable for the severe cold region. The operation control strategy based on quality adjustment can reduce heating energy consumption and maintain indoor temperatures at approximately 20°C. The proportion of clean energy heating in the optimized heating system decreased after the multi-objective optimization strategy. However, the initial investment and maintenance costs of the system were reduced, which reduced the LOCH of the system. Therefore, the multi-objective optimization strategy can effectively reduce the heating costs.

Economic optimization of exterior wall insulation in Chinese office buildings by coupling artificial neural network and genetic algorithm

Envelope insulation is an essential measure to reduce building energy consumption and is the focus of many building energy codes. In China, the current standard (GB 55015-2021) only specified limit values for the thermal conductivity (U) of the exterior walls, and it ignored variations in building characteristics and internal parameters. Therefore, it is difficult for architects to quickly determine the exterior wall U-value in building design and retrofit. To address this issue, the exterior wall U-values of office buildings in China were economically optimized by TRNSYS, ANN, and GA. To begin with, the effect of enhancing exterior wall insulation on the heating and cooling energy consumption of office buildings was investigated by TRNSYS software, taking into account variations in building characteristics. Moreover, the exterior wall U-values of office buildings were optimized by coupling ANN and GA. The results showed that the design values of the GB 55015-2021 did not achieve the optimal results in China, and the most economical exterior wall U-value was 0.24 W/(m2·K) in Harbin, 0.24 W/(m2·K) in Beijing, 0.42 W/(m2·K) in Changsha, 1.82 W/(m2·K) in Guangzhou, 0.66 W/(m2·K) in Kunming. Compared with the pre-optimization, the annual life cycle cost of building heating and cooling reduced by 0.96 % in Harbin, 2.07 % in Beijing, 1.44 % in Changsha, 1.68 % in Guangzhou, and 7.37 % in Kunming. In addition, variations in building parameters should be considered in the design phase of new buildings or in the renovation of old buildings, such as internal heat gain, which may lead to different optimal results.

Design and optimization of a geothermal absorption cooling system in a tropical climate

The electricity required for air conditioning is soaring worldwide. Absorption chillers represent an alternative to classical vapor compression systems, using heat instead of electricity. However, absorption chillers powered by renewable geothermal heat have received little attention so far. This paper introduces a system using a hot geothermal fluid (typically in the range of 80–110 °C) to produce cooling through a single-effect absorption chiller, and Domestic Hot Water (DHW) through a heat exchanger. It considers a hotel located in Martinique, a French Caribbean island. The electric consumption of every subsystem has been thoroughly estimated. The originality of this paper is twice: i) the system is modelled in TRNSYS software considering dynamic conditions, ii) the system undergoes surrogate modelling and multi-objective optimization to minimize both the cost and the CO2 content of the delivered thermal energy. Several scenarios are considered, depending upon the geothermal temperature, mass flow rate, well remoteness, and demand size. The studied system appears to be systematically more expensive than a combination of a classical vapor compression chiller and a boiler for DHW. However, it can significantly decrease the CO2 content of the provided energy, especially in an island where most electricity is generated from fossil fuels. The proximity of the geothermal well and the use of the warm water leaving the absorption generator (here for DHW production) appear to be key factors for system relevance, along with a hotter geothermal fluid (e.g., 110 °C instead of 80 °C).

Transient multi-objective optimization of solar and fuel cell power generation systems with hydrogen storage for peak-shaving applications

The present article introduces an innovative solution to improve performance efficiency while shaving the demand during peak hours. The idea focuses on efficient gas turbine and Rankine cycle hybridization for power and hydrogen production based on high-temperature heliostat solar towers. The proposed model is simulated via TRNSYS software to assess the performance transiently and then optimized through the artificial neural network in MATLAB program to minimize the calculation time. The key economic, environmental, and energy indicators are evaluated, compared, and optimized for this. According to the effect of main design parameters, including gas turbine inlet temperature, mass flow rate, and heliostat area, on the system's indicators, there is a conflictive trend among the power productivity, cost, and emission index, signifying the optimization significance. The optimization results show that the net power, efficiency, cost, and CO2 emissions are 298,300 GJ, 30.7%, 3.6 M$, and 20,760 tonnes under optimal conditions. This working condition is obtained by electing turbine inlet temperature, solar area, and airflow rate of 1087 °C, 91,200 m2, and 68,817, respectively. At this condition, while 71.18% of the yearly primary energy is provided by the sun, biomass meets the rest, showing the importance of renewable combination to achieve the highest independence from the grid. Finally, the system can generate an additional 585 kg/day of hydrogen that could be used in relevant industries.

Dynamic simulation of the performance of a solar assisted heat pump in different climates

One method to reduce energy consumption in buildings is using solar-assisted heat pumps, in which the combination of heat pump and solar collector is used to improve the thermal performance. In this paper, TRNSYS and EES software are used to simulate the performance of an indirect expansion solar-assisted heat pump. Dynamic simulation of the system is performed by changing parameters such as the mass flow rate of the collector working fluid and the collector area in five climates including Hot/Dry, Cold/Dry, Moderate/Humid, Hot/semi-Humid, and Hot/Humid. The results show that, in January, the Cold/Dry climate had the lowest free energy ratio (FER) because of the high space heating load. In this month, the Hot/semi-Humid climate has the highest FER, because of the higher solar radiation and no need for space heating. The annual FER in the Hot/Dry zone is 71% which is higher than that of other zones. The lowest FER is related to Moderate/Humid climate due to high humidity and cloudiness.

Preparation and performance study of a novel radiant panel for thermal and cooling storage with phase change materials

Phase change radiant panels (PCRPs) with thermal storage can enhance the heat capacity of buildings, and reduce building energy consumption. In this paper, a composite phase change material (CPCM) was prepared by paraffin wax-lauric acid/expanded graphite (PW-LA/EG) and applied to radiant panels. This CPCM exhibits a broad temperature range for phase change (10°C - 40°C), with EG at the optimal mass fraction of 14% and PW-LA at the optimal ratio of 1:1. It has a moderate latent heat capacity, a thermal conductivity of 1.692 W/mK, and excellent thermal stability. Furthermore, the simulations were performed in this paper, and the year-round comfort, thermal storage/release characteristics, and the influencing factors of PCRPs were evaluated by TRNSYS software. The results show that the PCRP can enhance indoor comfort throughout the year and exhibit excellent thermal storage and release properties. The analysis of influencing factors indicates that the thickness of the PCM has a small impact on the PCRP. It is recommended that a radiant panel coverage rate of at least 70% and a water supply time of 10 h in summer and 8 h in winter. These optimized parameter values can offer valuable guidance for the design and practical application of PCRPs. Practical application Phase change materials have been widely studied as materials used for thermal energy storage. The radiant panel with phase change materials can enhance the heat capacity of buildings, and reduce building energy consumption. This paper proposes a phase change radiant panel that can be used to solve the problem of year-round energy storage of radiant panels in hot summer and cold winter areas. Furthermore, this paper uses TRNSYS software to study the performance of the phase change radiant panels and offers valuable guidance for the design and practical application of PCM radiant panels.

Optimization of solar and heat pump complementary powered desiccant air conditioning system

The effective utilization of renewable heat sources is critical for energy saving in desiccant air conditioning systems. A new solar and heat pump complementary powered desiccant air conditioning system is proposed. The system consists of a solar and water source heat pump complementary reheat subsystem, a two-stage desiccant wheel, a three-stage air cooler, and a two-stage heat pipe exchanger. Simulation are performed in the transient simulation software TRNSYS, and the particle swarm optimization and the Hooke Jeeves algorithm with life cycle cost as the objective function are applied to optimize the collector area, the heat storage tank volume and the water-source heat pump power. The results show that the monthly average coefficient of performance of the system is 5.1, 5.6, 5.5 and 4.8 in June, July, August and September, respectively. Compared to the conventional air conditioning system, the new system has a 58.4% reduction in operation cost and a payback period of 6.6 years. The CO2 emission reduction rate of the new system can reach 65.2% in July and 65.1% in August, while it is the lowest in September at 62.9%. Based on the above, the new system has better energy efficiency, economic and environmental benefits.

Optimizing Renewable Energy Integration: A Case Study of Standalone PV-Battery Systems in IZTECH Campus

In this research paper the feasibility of renewable-powered, self-sufficient university campuses was explored by conducting a technoeconomic analysis of standalone PV-Battery systems for the buildings of Izmir Institute of Technology (IZTECH) in Izmir, Turkey. Given the high energy demand and dependence on fossil-based grids by universities, integrating renewables becomes important for minimizing carbon footprints. In this study the campus's solar potential was focused and the techno-economic feasibility of grid-independent operations provided by PV-battery systems was evaluated. Four scenarios were investigated: (i) maximum PV installation for each building (MPVB), (ii) maximum PV installation for the entire campus (MPVC), (iii) necessary PV installation for self-sufficiency of each building (NPVB), and (iv) necessary PV installation for self-sufficiency of the whole campus (NPVC). The first two scenarios considered the maximum achievable rooftop PV installation while the latter two included additional PV installation to cover all electricity needs. For all scenarios both lead-acid and Li-ion batteries were considered. Mathematical models were developed using PVSol and TRNSYS software, and technoeconomic analysis was conducted using Levelized Cost of Energy (LCOE) and Net Present Value (NPV) methods. It was found that the NPVC scenario with lead-acid batteries is the most favorable, as it minimizes battery utilization by enabling more PV installation and facilitating energy transfer between buildings. Additionally, the research showed that off-grid PV-battery systems are economically less feasible compared to on-grid counterparts, primarily due to the high cost of batteries.

Comprehensive Investigation of Solar Water Heater System Performance, Stratification, Charging, and Discharging Efficiency Using TRNSYS Software

Comprehensive Investigation of Solar Water Heater System Performance, Stratification, Charging, and Discharging Efficiency Using TRNSYS Software

Sustainable off-grid residential heating and desalination: Integration of biomass boiler and solar energy with environmental impact analysis

As global energy demand rises and the environmental impact of fossil fuel-based heating systems becomes increasingly evident, transitioning to renewable energy sources like solar and biomass for residential use is imperative. This is further underscored by the growing scarcity of freshwater resources, especially in arid urban environments. This study introduces an innovative off-grid system that effectively integrates a floor heating system with a vapor compression desalination unit. The novelty of this study lies in its approach to combining solar and biomass energies for both heating and desalination in a single off-grid system. The system's electrical and thermal energy needs are met by combining photovoltaic thermal collectors and a biomass boiler. Using TRNSYS software, the system's performance was evaluated in varying design configurations across Riyadh, Doha, and Abu Dhabi, targeting optimal thermal comfort for a standard residence with four occupants. Results show Riyadh leading in solar fraction at 48.43%, followed by Abu Dhabi (47.23%) and Doha (44.85%). The optimal equivalent heat transfer coefficient for the floor heating system varied notably between these cities, with Abu Dhabi requiring a lower coefficient to achieve thermal comfort. Additionally, a life cycle analysis revealed that the biomass boiler is the predominant source of CO2 emissions, contributing over 70% of the total in each city. Riyadh exhibited the lowest CO2 emissions, attributed to its higher solar fraction. This study demonstrates the system's versatility across different urban climates and its potential to lessen dependence on traditional energy sources, positioning it as a promising solution for future off-grid applications.

Influence of building thermal envelope modeling parameters on results of building energy simulation

The paper investigates the influence of input values for building energy model parameters on simulation results. The methodology is based on dynamic simulations in TRNSYS software, including models for three different buildings, with variations in different parameters such as referent dimensions, infiltration, envelope thermophysical properties, and thermal capacitance of interior space. The method is applied to a case study of theoretical buildings located in Slovenia. Obtained results suggest that the accuracy of model parameters’ inputs related to thermal properties of glazing have the most significant impact on simulation results, where reduction in g-value from 0.62 to 0.22 reduces simulated qH,nd and qC,nd for 25% and 95% respectively. Referent dimensions for modeling floor area are the least influential parameter, where for Building III (BSF = 0.36) the change of referent dimensions results in variations of simulated qH,nd and qC,nd for less than ±1%, while for Building I (BSF = 0.62) qH,nd and qC,nd variations are up to ±20%. In general, for all model parameters, with a reduction of BSF, the influence of input variations is also reduced, meaning energy models for large buildings are more robust and less biased to deviation in simulation results from the inaccuracy of model inputs.

Enhancing indoor thermal comfort and sustainability: A solar-driven desiccant cooling and adsorption chiller system with environmental impact assessment

Addressing indoor thermal comfort in buildings located in hot and humid climates is a persistent challenge, demanding innovative cooling solutions that are both efficient and environmentally responsible. This paper introduces a new integration of a Phase Change Material (PCM)-based solar desiccant cooling system with an adsorption chiller, a setup designed to enhance indoor thermal comfort conditions while utilizing renewable energy sources. This research simultaneously leverages the heating and cooling capacities of the adsorption chiller, leading to an efficient system performance. The TRNSYS software is used to evaluate the system's behavior in a typical house with moderate cooling demand and characterized by high relative humidity. Two types of solar collectors, the evacuated tube and Wavy Direct Absorption Solar Collectors (WDASC), are evaluated to supply the required thermal energy, providing a comprehensive assessment of the system’s efficiency under different configurations. Additionally, the study conducts a comprehensive Life Cycle Assessment (LCA) to quantify the Global Warming Potential (GWP) of the systems. The results confirm the proposed system's capability to maintain indoor thermal comfort within acceptable Predicted Mean Vote (PMV) and Predicted Percentage of Dissatisfied (PPD) ranges. The evacuated tube collector showed marginally better performance (average PMV: 0.018, average PPD: 6.7 %) compared to the WDASC (average PMV: 0.075, average PPD: 7.3 %). Additionally, the evacuated tube collector demonstrates superior energy (75.68 %) and exergy (10.82 %) efficiencies compared to the WDASC. The system utilizing the evacuated tube collector surpasses the WDASC configuration, achieving a higher Coefficient of Performance (COP) of 0.47 compared to 0.41, and emitting lower GWP values of 0.0194 kg-CO2 per kWh of cooling capacity compared to 0.0201 kg-CO2. An analysis of Embodied Energy reveals that the adsorption chiller is the most significant contributor to lifecycle energy consumption, with a quicker Energy Payback Time (EPBT) for the evacuated tube system (2.75 years) compared to the WDASC system (3.94 years). This research thus contributes a highly efficient, sustainable, and environmentally friendly solution to the challenge of cooling in buildings, setting a new standard for future green building practices.

Modeling of a solar thermal system as a power supply alternative for a resistor water distillation system using TRNSYS

The sizing of a solar thermal system to feed the water distillers in the laboratory of the Santander Technological Units is presented, proposing a comparative study between three calculation methods (f-chart, instantaneous and ACSOL) for the estimation of the surface of solar capture, finally supported by modeling in the TRNSYS software of the final system, to evaluate its behavior dynamically during one year. Initially, a search for information is carried out to establish the models to develop each of the calculation methods, additionally technical data is collected from the laboratory equipment to determine the consumption of hot water. Subsequently, each of the calculation methods is applied in order to size the catchment surface, to finally carry out a comparative study between the results obtained, determining which is the most appropriate method for the calculation and defining the dimensions of the same, to develop a modeling of the dynamic behavior of the system through the TRNSYS Software. The final result presents a storage system with an average temperature of 62.13 ° C and solar collectors with an average temperature of 58.7 ° C for one year of operation. Finally, the operating time of the resistive stills is reduced from 11 hours a day to 6 hours with the integration of the Thermosolar system.

Assessment of prosumer-based energy system for rural areas by using TRNSYS software

The prosumers are the new performers progressing towards a low-carbon future. Renewable-based power generation is essential, even in rural areas, to pave a path toward sustainable development. This study establishes a simulation model for two identical residential buildings to assess the prosumer's impact on future local (standalone) energy systems. According to the climate condition of Pakistan, the technical, economic, and environmental performance of the standalone system is evaluated using TRNSYS software. Assumptions and modeling of different components, photovoltaic (PV) panels, and batteries are also discussed. This study provides the starting point of a real-time framework of energy trade between two rural houses connected with a common microgrid. Both houses are medium-sized family houses with almost identical electricity demands. One house has PV mounted on the rooftop, with the battery as an optimal energy storage option. Attention is given to peak demand management and surplus energy during enough production hours. A dynamic energy management approach between two buildings is proposed based on TRNSYS and blockchain. Simulation results show that the real-time implementation of local energy production and energy trading at the household level facilitates achieving the dual benefits of reducing consumer costs and maximizing self-consumption.

Analysis of the Influence of Envelope Heat Gain on Hygrothermal Comfort in Tropical Housing: The Case of Benin

The current construction of residential buildings in Benin neglects the importance of thermal insulation of their envelopes. Instead, it relies on active systems as a solution to mitigate over-consumption of electrical energy and guarantee a certain level of thermal comfort inside these buildings. It should be noted that Beninese architects are generally unfamiliar with these thermal aspects.
 The main aim of this study is to assess the effects of thermal insulation on walls and roof, determine the optimum thickness of insulating materials, and integrate a controlled mechanical ventilation system to improve thermal comfort in a humid tropical climate. The investigations were carried out on an example of a typical residential building located in Cotonou, Benin, with precise geographical coordinates (latitude 6°38' North, longitude 2°34' East). To analyze the thermal behavior of this building, a series of dynamic thermal simulations were carried out using TRNSYS software, which was used both to model the building structure and to run the various simulations.
 The results of this study revealed that thermal insulation of the walls and roof, using polystyrene, significantly reduced the need for air conditioning. What's more, the integration of a controlled mechanical ventilation system not only ensured indoor air quality, but also helped regulate indoor humidity, reducing it from 67% to 76%.

Optimizing winter climate control in high-altitude smart greenhouse through renewable energy integration

In the context of food security in mountain regions, this study explores the potential of a Smart Greenhouse (SGH) to address the challenges posed by climate change and limited resources. The SGH utilizes an 8 m2 solar water heating system, weather stations for external temperature and humidity monitoring, as well as internal light, humidity, and temperature sensors to create an optimized environment for crop cultivation. Experiments were conducted with various crops within the SGH during the harsh winter months, typically rendering the cultivable land fallow due to extreme cold conditions. The SGH is equipped with sensors and communication technologies, ensuring continuous data collection and the automated regulation of heating, ventilation, and air conditioning systems. Located in Genekha, Thimphu, this pilot SGH seamlessly integrates renewable energy technology to provide heat during the cold winter season, obviating the need for external heating sources in the summer. The study employed TRNSYS and OpenStudio simulation software to assess the SGH's performance, focusing on temperature and humidity control inside and outside the greenhouse. Additionally, soil pH and nutrient content were examined, and the time required for crop growth and harvesting was recorded. In conclusion, this paper acknowledges some of the current design's limitations and presents recommendations for future enhancements, with a focus on the specific context of improving crop production and food security in mountainous regions.