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Simon Furbo - One of the best experts on this subject based on the ideXlab platform.

  • thermal performance assessment and improvement of a solar domestic Hot Water Tank with pcm in the mantle
    Energy and Buildings, 2018
    Co-Authors: Simon Furbo, Jie Deng, Weiqiang Kong
    Abstract:

    Abstract To develop an appropriate solar DHW (Domestic Hot Water) Tank for residential dwellings and put it into the European solar thermal market for promotion, thermal performance tests of PCM (Phase Change Material) Hot Water storage Tanks of both a prototype and an improved version with a Water volume of 148 l and 35 kg PCM in the mantle has been carried out. The Tank was designed to provide DHW for residential dwellings through a combination of solar and auxiliary heating, concurrently using PCM on the basis of cheap SAT (Sodium Acetate Trihydrate) as a thermal battery to shave off peak auxiliary power or to work under power outage. Heat transfer matching properties of the bottom and the top spirals separately for solar charge and auxiliary charge of the prototype DHW Tank were ascertained in terms of heat exchanger capacity rate (HXCR) and the rule of thumb of boiler powers, respectively. Moreover, heat content of the PCM was estimated via a series of test cycles in order to infer its capacity and stability. It was found that there were some technical problems for the prototype Tank module, such as mismatching property of the heat exchanger spirals, heat mixing phenomena during Hot Water draw-off. Thus, an improved Tank was manufactured based on the test results of the prototype. Further tests indicated that the matching property of the top heat exchanger spiral was ameliorated for auxiliary charge and the heat mixing between Hot Water supply pipe and Water Tank was restrained during discharge, except that the length of the bottom spiral should be further reduced. Regarding the PCM in the mantle, it was inferred that the PCM heat content was somewhat lower than that of ideally working SAT. The PCM tended to perform stably under 16 test cycles with more than 3-month consecutive tests, implying no phase segregation occurred as that would degraded its performance.

  • Thermal stratification built up in Hot Water Tank with different inlet stratifiers
    Solar Energy, 2017
    Co-Authors: Janne Dragsted, Simon Furbo, Mark Dannemand, Federico Bava
    Abstract:

    Abstract Thermal stratification in a Water storage Tank can strongly increase the thermal performance of solar heating systems. Thermal stratification can be built up in a storage Tank during charge, if the heated Water enters through an inlet stratifier. Experiments with a test Tank have been carried out in order to elucidate how well thermal stratification is established in the Tank with differently designed inlet stratifiers under different controlled laboratory conditions. The investigated inlet stratifiers are from Solvis GmbH & Co KG and EyeCular Technologies ApS. The inlet stratifier from Solvis GmbH is a rigid plastic pipe with holes for each 30 cm. The holes are designed with flaps preventing counter flow into the pipe. The inlet stratifier from EyeCular Technologies ApS is made of a flexible polymer with openings all along the side and in the full length of the stratifier. The flexibility of the stratifier prevents counterflow. The tests have shown that both types of inlet stratifiers had an ability to create stratification in the test Tank under the different test conditions. The stratifier from EyeCular Technologies ApS had a better performance at low flows of 1–2 l/min and the stratifier for Solvis GmbH & Co KG had a better performance at 4 l/min. In the intermediate charge test the stratifier from EyeCular Technologies ApS had a better performance in terms of maintaining the thermal stratification in the storage Tank while charging with a relative low temperature.

  • Development of a Hot Water Tank Simulation Program with Improved Prediction of Thermal Stratification in the Tank
    Energy Procedia, 2015
    Co-Authors: Jianhua Fan, Simon Furbo, Hongqiang Yue
    Abstract:

    Abstract A simulation programSpiralSolwas developed in previous investigations to calculate thermal performance of a solar domestic Hot Water (SDHW) system with a Hot Water Tank with a built-in heat exchanger spiral[1]. The simulation program is improved in the paper in term of prediction of thermal stratification in the Tank. The transient fluid flow and heat transfer in the Hot Water Tank during cooling caused by standby heat loss are investigated by validated computational fluid dynamics (CFD) calculations. Detailed CFD investigations are carried out to determine the influence of thickness and material property of the Tank wall on thermal stratification in the Tank. It is elucidated how thermal stratification in the Tank is influenced by the natural convection and how the heat loss from the Tank sides will be distributed at different levels of the Tank at different thermal conditions. The existing equation of the heat loss removal factor used in SpiralSol is evaluated by means of the detailed CFD calculations. A generalized new equation for the heat loss removal factor is obtained by regression. The new equation calculates the heat loss removal factor for a given temperature gradient in the Tank,taking into account the influences of Tank volume, height to diameter ratio, Tank insulation, thickness and material property of the Tankand initial thermal conditions of the Tank. The equation is validated for a Tank volume between 150 l and 500 l, a Tank height to Tank diameter ratio of 1-5,a Tank wall thickness of 1.5 mm to 3 mm for a stainless steel Tank and a Tank wall thickness of between 3 mm to 5 mm for a normal steel Tank. Accuracy and reliability of the SpiralSol program with the improved prediction of heat loss removal factor will be examined in future investigations.

  • thermal stratification in a Hot Water Tank established by heat loss from the Tank
    Solar Energy, 2012
    Co-Authors: Jianhua Fan, Simon Furbo
    Abstract:

    Abstract This paper presents numerical investigations of thermal stratification in a vertical cylindrical Hot Water Tank established by standby heat loss from the Tank. The transient fluid flow and heat transfer in the Tank during cooling caused by standby heat loss are calculated by means of validated computational fluid dynamics (CFD) models. The measured heat loss coefficient for the different parts of the Tank is used as input to the CFD model. Parametric studies are carried out using the validated models to investigate the influence on thermal stratification of the Tank by the downward flow and the corresponding upward flow in the central parts of the Tank. Tank design parameters such as Tank volume, height to diameter ratio and insulation and different initial conditions of the Tank are investigated. It is elucidated how thermal stratification in the Tank is influenced by the natural convection and how the heat loss from the Tank sides will be distributed at different levels of the Tank at different thermal conditions. The results show that 20–55% of the side heat loss drops to layers below in the part of the Tank without the presence of thermal stratification. A heat loss removal factor is introduced to characterize the effect of the buoyancy driven flow on exchange of heat loss between Tank layers by natural convection. Based on results of the parametric studies, a generalized equation for the heat loss removal factor is obtained by regression which takes into account the influences of Tank volume, height to diameter ratio, Tank insulation and initial conditions of the Tank. The equation is validated for a 150–500 l Tank insulated with 0–7 cm mineral wool and a Tank height to diameter ratio of 1–5. The equation will be implemented in an existing Tank optimization and design program for calculation of thermal performance of a Hot Water Tank.

  • buoyancy driven flow in a Hot Water Tank due to standby heat loss
    Solar Energy, 2012
    Co-Authors: Jianhua Fan, Simon Furbo
    Abstract:

    Abstract Results of experimental and numerical investigations of thermal behavior in a vertical cylindrical Hot Water Tank due to standby heat loss of the Tank are presented. The effect of standby heat loss on temperature distribution in the Tank is investigated experimentally on a slim 150 l Tank with a height to diameter ratio of 5. A Tank with uniform temperatures and with thermal stratification is studied. A detailed computational fluid dynamics (CFD) model of the Tank is developed to calculate the natural convection flow in the Tank. The distribution of the heat loss coefficient for the different parts of the Tank is measured by experiments and used as input to the CFD model. Water temperatures at different levels of the Tank are measured and compared to CFD calculated temperatures. The investigations focus on validation of the CFD model and on understanding of the CFD calculations. The results show that the CFD model predicts satisfactorily Water temperatures at different levels of the Tank during cooling by standby heat loss. It is elucidated how the downward buoyancy driven flow along the Tank wall is established by the heat loss from the Tank sides and how the natural convection flow is influenced by Water temperatures in the Tank. When the temperature gradient in the Tank is smaller than 2 K/m, there is a downward fluid velocity of 0.003–0.015 m/s. With the presence of thermal stratification the buoyancy driven flow is significantly reduced. The dependence of the velocity magnitude of the downward flow on temperature gradient is not influenced by the Tank volume and is only slightly influenced by the Tank height to Tank diameter ratio. Based on results of the CFD calculations, an equation is determined to calculate the magnitude of the buoyancy driven flow along the Tank wall for a given temperature gradient in the Tank.

Necdet Altuntop - One of the best experts on this subject based on the ideXlab platform.

  • Experimental investigation on enhancement of thermal performance with obstacle placing in the horizontal Hot Water Tank used in solar domestic Hot Water system
    Renewable Energy, 2019
    Co-Authors: Dogan Erdemir, Hakan Atesoglu, Necdet Altuntop
    Abstract:

    Abstract Horizontal mantled Hot Water Tanks are widely used in solar domestic Hot Water systems. Increasing thermal performance of the Hot Water Tank is significant issue for thermodynamic efficiencies of the system and user satisfaction. This study presents an experimental study for determining the effect of obstacle placing on thermal performance in horizontal mantled Hot Water Tank. Obstacles were positioned perpendicular to the flow direction inside the Tank in different positions. First, one obstacle was placed inside the Tank in different positions and then two obstacles were placed inside the Tank. Results were presented over the temperature distribution inside the Tank, mantle outlet temperature, main outlet temperature, energy efficiency and exergy efficiency. At the end of the study, it was found that obstacle placing in horizontal mantled Hot Water Tank increased the thermal performance of Tank. Temperature distribution results showed that placing obstacle inside the Tank increased stored Hot Water temperature and volume. Mantle outlet temperature could be decreased 1.5 °C, and the main outlet temperature could be increased 3.6 °C by placing obstacles inside the Tank. Consequently, when all performance criteria considered, the best thermal performances were seen in a = 150 mm, a = 150 mm b = 100 mm and a = 350 mm b = 100 mm.

  • Numerical Analysis of Thermal Stratification Obstacles Located Into Mantled Hot Water Tank
    2017
    Co-Authors: Necdet Altuntop, Onur Bor, Nehir Tokgöz, Ömer Özgün
    Abstract:

    In the presented study, a numerical investigation is carried on the effect of using different obstacles on thermal stratification in a mantled Hot Water Tank. Thermal stratification occurs as a result of temperature difference of collected Water in the Tank. The purpose of this study is to provide a better thermal stratification in the Hot Water Tank and increase usage time of Hot Water. Solutions are made for no obstacle and five different obstacles geometries in the vertical cylindrical mantled Hot Water Tank. Collector Hot Water inlet temperature is 350 K, cold Water inlet temperature is 289 K, collector Hot Water inlet velocity is 0.3 m/s, cold Water inlet velocity is 0.1 m/s. Obstacles are located into h=0.15 m, 0.3 m, 0.4 m, 0.5 m, 0.6 m and 0.7 m from the bottom of the Tank for determining the best occurrence of thermal stratification distance. Continuity, momentum and energy equations are considered in the numerical analysis. Solutions are made for two hours unsteady flow conditions and three dimensional cases. At the end of two hours, temperature distributions, Water temperature supplied by the Tank, Water temperature going to collector and various Water temperature differences between Tank outlet and inlet are illustrated with graphs. Placed obstacles have better thermal stratification than pure case. Outer conic and cylindrical obstacles models have better thermal stratification; however, less thermal stratification is achieved with inner conical, inner reverse conical and inner cylindrical obstacle models. There is no positive effect is detected on the placement of obstacles near the ceiling of the Tank and it is decided to place the obstacles between centre and bottom of the Tank to achieve better thermal stratification.

  • Improved thermal stratification with obstacles placed inside the vertical mantled Hot Water Tanks
    Applied Thermal Engineering, 2016
    Co-Authors: Dogan Erdemir, Necdet Altuntop
    Abstract:

    Abstract Thermal stratification is a significant performance parameter for thermal energy storage Tanks. In present study, the thermal stratification of vertical mantled Hot Water Tank was investigated by placing different obstacle inside the Tank. Four different obstacles were placed inside the Tank in four different distances from the Tank bottom. Thus effects of the obstacle types and positions were investigated. At the end of study, it was found that obstacle placed inside the Tank enhanced the thermal stratification. Results were presented in the terms of temperature distribution, energy storing capacity, Richardson Number, consumption outlet and mantle outlet temperature. All these values were improved by placing the obstacle inside the Tank, according to ordinary Tank. The best thermal stratification was obtained between Y = 200 and Y = 300 mm the distance from the Tank bottom. A type obstacle supplied the best thermal stratification.

  • Optimum Dimensions of an Obstacle Placed in a Hot Water Tank for Thermal Stratification
    Energy Exploration & Exploitation, 2005
    Co-Authors: Mevlut Arslan, Necdet Altuntop, Veysel Ozceyhan, Mehmet Kanoglu
    Abstract:

    Dimension of an obstacle placed in a Hot Water Tank for thermal stratification is optimized numerically. Numerical method is validated using both experimental and numerical results. A cylindrical Tank used to store heat for solar collector applications is considered. A cylindrical obstacle with a hole in the middle is placed in the Tank and various f/H and g/D ratios of the obstacle geometry are considered. Here H and D are the height and diameter of the Tank, respectively, where f is the distance from the bottom surface of the Tank to the cold-Water inlet channel and g is the diameter of the hole in the obstacle. Temperature distribution in the Tank, Water temperature supplied by the Tank, and temperature differences at various Tank inlet and outlets are obtained for various f/H and g/D ratios. The results show that placing obstacle in the Tank improves thermal stratification, and thus it increases the temperature of Water supplied by the Tank compared with no obstacle case and that the best thermal stra...

Jianhua Fan - One of the best experts on this subject based on the ideXlab platform.

  • Development of a Hot Water Tank Simulation Program with Improved Prediction of Thermal Stratification in the Tank
    Energy Procedia, 2015
    Co-Authors: Jianhua Fan, Simon Furbo, Hongqiang Yue
    Abstract:

    Abstract A simulation programSpiralSolwas developed in previous investigations to calculate thermal performance of a solar domestic Hot Water (SDHW) system with a Hot Water Tank with a built-in heat exchanger spiral[1]. The simulation program is improved in the paper in term of prediction of thermal stratification in the Tank. The transient fluid flow and heat transfer in the Hot Water Tank during cooling caused by standby heat loss are investigated by validated computational fluid dynamics (CFD) calculations. Detailed CFD investigations are carried out to determine the influence of thickness and material property of the Tank wall on thermal stratification in the Tank. It is elucidated how thermal stratification in the Tank is influenced by the natural convection and how the heat loss from the Tank sides will be distributed at different levels of the Tank at different thermal conditions. The existing equation of the heat loss removal factor used in SpiralSol is evaluated by means of the detailed CFD calculations. A generalized new equation for the heat loss removal factor is obtained by regression. The new equation calculates the heat loss removal factor for a given temperature gradient in the Tank,taking into account the influences of Tank volume, height to diameter ratio, Tank insulation, thickness and material property of the Tankand initial thermal conditions of the Tank. The equation is validated for a Tank volume between 150 l and 500 l, a Tank height to Tank diameter ratio of 1-5,a Tank wall thickness of 1.5 mm to 3 mm for a stainless steel Tank and a Tank wall thickness of between 3 mm to 5 mm for a normal steel Tank. Accuracy and reliability of the SpiralSol program with the improved prediction of heat loss removal factor will be examined in future investigations.

  • thermal stratification in a Hot Water Tank established by heat loss from the Tank
    Solar Energy, 2012
    Co-Authors: Jianhua Fan, Simon Furbo
    Abstract:

    Abstract This paper presents numerical investigations of thermal stratification in a vertical cylindrical Hot Water Tank established by standby heat loss from the Tank. The transient fluid flow and heat transfer in the Tank during cooling caused by standby heat loss are calculated by means of validated computational fluid dynamics (CFD) models. The measured heat loss coefficient for the different parts of the Tank is used as input to the CFD model. Parametric studies are carried out using the validated models to investigate the influence on thermal stratification of the Tank by the downward flow and the corresponding upward flow in the central parts of the Tank. Tank design parameters such as Tank volume, height to diameter ratio and insulation and different initial conditions of the Tank are investigated. It is elucidated how thermal stratification in the Tank is influenced by the natural convection and how the heat loss from the Tank sides will be distributed at different levels of the Tank at different thermal conditions. The results show that 20–55% of the side heat loss drops to layers below in the part of the Tank without the presence of thermal stratification. A heat loss removal factor is introduced to characterize the effect of the buoyancy driven flow on exchange of heat loss between Tank layers by natural convection. Based on results of the parametric studies, a generalized equation for the heat loss removal factor is obtained by regression which takes into account the influences of Tank volume, height to diameter ratio, Tank insulation and initial conditions of the Tank. The equation is validated for a 150–500 l Tank insulated with 0–7 cm mineral wool and a Tank height to diameter ratio of 1–5. The equation will be implemented in an existing Tank optimization and design program for calculation of thermal performance of a Hot Water Tank.

  • buoyancy driven flow in a Hot Water Tank due to standby heat loss
    Solar Energy, 2012
    Co-Authors: Jianhua Fan, Simon Furbo
    Abstract:

    Abstract Results of experimental and numerical investigations of thermal behavior in a vertical cylindrical Hot Water Tank due to standby heat loss of the Tank are presented. The effect of standby heat loss on temperature distribution in the Tank is investigated experimentally on a slim 150 l Tank with a height to diameter ratio of 5. A Tank with uniform temperatures and with thermal stratification is studied. A detailed computational fluid dynamics (CFD) model of the Tank is developed to calculate the natural convection flow in the Tank. The distribution of the heat loss coefficient for the different parts of the Tank is measured by experiments and used as input to the CFD model. Water temperatures at different levels of the Tank are measured and compared to CFD calculated temperatures. The investigations focus on validation of the CFD model and on understanding of the CFD calculations. The results show that the CFD model predicts satisfactorily Water temperatures at different levels of the Tank during cooling by standby heat loss. It is elucidated how the downward buoyancy driven flow along the Tank wall is established by the heat loss from the Tank sides and how the natural convection flow is influenced by Water temperatures in the Tank. When the temperature gradient in the Tank is smaller than 2 K/m, there is a downward fluid velocity of 0.003–0.015 m/s. With the presence of thermal stratification the buoyancy driven flow is significantly reduced. The dependence of the velocity magnitude of the downward flow on temperature gradient is not influenced by the Tank volume and is only slightly influenced by the Tank height to Tank diameter ratio. Based on results of the CFD calculations, an equation is determined to calculate the magnitude of the buoyancy driven flow along the Tank wall for a given temperature gradient in the Tank.

  • Heat Losses from Pipes Connected to Hot Water Storage Tanks
    Proceedings of ISES World Congress 2007 (Vol. I – Vol. V), 2008
    Co-Authors: Elsa Andersen, Jianhua Fan, Simon Furbo
    Abstract:

    The heat loss from pipe connections at the top of Hot Water storage Tanks with and without a heat trap is investigated theoretically and compared to similar experimental investigations. Computational Fluid Dynamics (CFD) is used for the theoretical analysis. The investigations show that the heat loss from an ideally insulated pipe connected to the top of a Hot Water Tank is mainly due to a natural convection flow in the pipe, that the heat loss coefficient of pipes connected to the top of a Hot Water Tank is high, and that a heat trap can reduce the heat loss coefficient significantly. Further, calculations show that the yearly thermal performance of solar domestic Hot Water systems is strongly reduced if the Hot Water Tank has a thermal bridge located at the top of the Tank.

  • Experimental investigations on small low flow SDHW systems based on mantle Tanks
    Proceedings of ISES World Congress 2007 (Vol. I – Vol. V), 2008
    Co-Authors: Simon Furbo, Jianhua Fan
    Abstract:

    Side-by-side tests of two small SDHW systems based on mantle Tanks have been carried out in a laboratory test facility. The systems are identical with exception of the vertical mantle Tank. One of the Tanks is the so-called Danlager 1000 marketed by Nilan A/S. The other Tank is a test Tank produced by METRO THERM A/S. Both Tanks are built into 60 × 60 cm cabinets. In this way it is possible to bring the test Tank on the market. Both Hot Water Tanks have a total volume of 189 l and an auxiliary volume of 86 1 at the top of the Tank heated to 51°C by a 1000 W electrical heating element during the tests. The Hot Water Tank diameter is 492 mm and 400 mm for the Danlager 1000 Tank, respectively the test Tank. The height/diameter ratio for the Hot Water Tank is 2.1 for the Danlager 1000 Tank and 3.9 for the test Tank. The mantle inlet for the Danlager 1000 Tank is located at the very top of the mantle, while the mantle inlet for the test Tank is located 125 mm from the top of the mantle. Both Tanks are insulated with PUR foam insulation filling up the space between the Tanks and the cabinets. Consequently the insulation thickness for the test Tank is greater than the insulation thickness of Danlager 1000.

J P Zhang - One of the best experts on this subject based on the ideXlab platform.

  • simulation of operating characteristics of the silica gel Water adsorption chiller powered by solar energy
    Solar Energy, 2011
    Co-Authors: G Zhang, D.c. Wang, J P Zhang
    Abstract:

    Abstract A lumped parameter model of a silica gel–Water adsorption chiller driven by solar energy was introduced for the operating characteristics investigation. Matlab–Simulink, as a high-performance computing and programming tool, was used to simulate the operating characteristics of the chiller. Effects of the Hot Water Tank capacity, the cycle time and the initial Hot Water temperature on the performance of the chiller were analyzed when the chiller was driven by a stable heat source and solar energy respectively. The simulation results indicated that when the chiller was driven by solar energy, the open circulation of the Hot Water with a short cycle time and the closed circulation of Hot Water with a longer cycle time were better. A proposal was also provided for the chiller driven by solar energy to work under the optimum working conditions, such as Hot Water circulation mode, cycle time and initial temperature.

  • Simulation of operating characteristics of the silica gel–Water adsorption chiller powered by solar energy
    Solar Energy, 2011
    Co-Authors: G Zhang, D.c. Wang, J P Zhang, Y.p. Han, Wanchao Sun
    Abstract:

    Abstract A lumped parameter model of a silica gel–Water adsorption chiller driven by solar energy was introduced for the operating characteristics investigation. Matlab–Simulink, as a high-performance computing and programming tool, was used to simulate the operating characteristics of the chiller. Effects of the Hot Water Tank capacity, the cycle time and the initial Hot Water temperature on the performance of the chiller were analyzed when the chiller was driven by a stable heat source and solar energy respectively. The simulation results indicated that when the chiller was driven by solar energy, the open circulation of the Hot Water with a short cycle time and the closed circulation of Hot Water with a longer cycle time were better. A proposal was also provided for the chiller driven by solar energy to work under the optimum working conditions, such as Hot Water circulation mode, cycle time and initial temperature.

Stephane Grieu - One of the best experts on this subject based on the ideXlab platform.

  • a new strategy based on power demand forecasting to the management of multi energy district boilers equipped with Hot Water Tanks
    Applied Thermal Engineering, 2017
    Co-Authors: Mouchira Labidi, Julien Eynard, Olivier Faugeroux, Stephane Grieu
    Abstract:

    Abstract As part of the second phase of the research project “OptiEnR”, aiming to improve the operation of multi-energy district boilers by adding optimally-designed and managed Hot Water Tanks to the plants, a new and generalized predictive strategy is proposed. This phase of the project was first dedicated to developing both a design approach, based on a parametric analysis, and a sequential management strategy. Basically, the excess thermal energy produced by the wood boiler unit(s) during low-demand periods can then be stored and released when demand is high, instead of engaging a gas boiler unit. However, this preliminary study has allowed us to point out possible improvements in the management of a Tank. That is why we have decided to develop a flexible and generalized strategy based on anticipating changes in power demand. So, the present paper focuses on the optimal management, using a generalized model-based predictive controller, of an ENGIE Cofely’s multi-energy district boiler equipped with a Hot Water Tank. The plant is located in northeast France, in the Grand Est region (Haut-Rhin). The controller makes use of a generic model of the district boiler and power demand is accurately forecasted over the next 24 h thanks to the MRA-ANN approach (i.e. a wavelet-based Multi-Resolution Analysis combined with Artificial Neural Networks). With the predictive strategy, the consumption of gas and carbon dioxide ( CO 2 ) emissions are significantly reduced. In the same time, the overall economic gain is increased. Overall performance is the best with a 200 m 3 Hot Water Tank added to the plant.

  • Methodology for the design of energy production and storage systems in buildings: Minimization of the energy impact on the electricity grid
    Energy and Buildings, 2012
    Co-Authors: Michaël Salvador, Stephane Grieu
    Abstract:

    Human life requires energy. Moreover, people spend around 90% of their time in buildings while about 40% of primary energy needs are due to buildings. That is why the present paper deals with a methodology allowing identifying and assessing the energy impact of a building on the electricity grid. Thanks to both the building models we developed and fuzzy logic contribution (used to control ventilation and develop occupancy scenarios related to human habits and lifestyle), the results we obtained in simulation validate the proposed impact indicator. Different insulation levels were considered as well as energy production (solar pHotovoltaic and thermal panels and a vertical axis windmill) and storage (a domestic Hot Water Tank) systems. These results highlighted the pertinence of such an indicator for optimizing the design of the just-mentioned systems and minimizing the amount of energy exchanged by buildings and the electricity grid. One can promote energy injection or take into account the status of the electricity grid when designing these systems. As a key result, the produced renewable energy is partially self-consumed, what allows for a more efficient and rational use of energy in buildings.