The Experts below are selected from a list of 327 Experts worldwide ranked by ideXlab platform

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

  • Demonstration and optimization of a Solar District Heating system with ground source heat pumps
    Solar Energy, 2020
    Co-Authors: Junpeng Huang, Jianhua Fan, Simon Furbo
    Abstract:

    Abstract Experimental and theoretical investigations have been carried out on the first large scale Solar assisted ground source heat pump (SAGSHP) for Heating and cooling of a village in the outskirts of Beijing. Long term performances of the system without and with Solar Heating were monitored. A TRNSYS model of the SAGSHP system was developed and validated against the measured data. Based on a parametrical investigation using the model, an optimized solution was proposed. It is shown that adding a domestic hot water system to the original SAGSHP system will not only help to secure thermal balance of the ground but also reduces primary energy consumption for hot water by 70%. The system COP increases by 9.4% from 2.42 to 2.65 and the annual overall operating cost decreases from 892,000 CNY to 794,000 CNY with only a small increase in equipment cost. Under the premise of ensuring thermal balance of the ground, there is an optimal match between the size of the ground heat storage, the collector area and the tank volume. Experience and lessons learned from the project are conducive to successful implementation of similar projects in the future.

  • large scale Solar District Heating plants in danish smart thermal grid developments and recent trends
    Energy Conversion and Management, 2019
    Co-Authors: Zhiyong Tian, Bengt Perers, Junpeng Huang, Jianhua Fan, Shicong Zhang, Jie Deng, Weiqiang Kong, Simon Furbo
    Abstract:

    Abstract Large Solar collector fields are very popular in District Heating system in Denmark, even though the Solar radiation source is not favorable at high latitudes compared to many other regions. Business models for large Solar Heating plants in Denmark has attracted much attention worldwide. Denmark is not only the biggest country in both total installed capacities and numbers of large Solar District Heating plants, but also is the first and only country with commercial market-driven Solar District Heating plants. By the end of 2017, more than 1.3 million m2 Solar District Heating plants are in operation in Denmark. Furthermore, more than 70% of the large Solar District Heating plants worldwide are constructed in Denmark. Based on the case of Denmark, this study reviews the development of large Solar District Heating plants in Denmark since 2006. Success factors for Danish experiences was summarized and discussed. Novel design concepts of large Solar District Heating plants are also addressed to clarify the future development trend. Potential integration of large Solar District Heating plants with other renewable energy technologies are discussed. This paper can provide references to potential countries that want to exploit the market for Solar District Heating plants. Policy-makers can evaluate the advantages and disadvantages of Solar District Heating systems in the national energy planning level based on the know-how and experiences from Denmark.

  • Feasibility study on Solar District Heating in China
    Renewable and Sustainable Energy Reviews, 2019
    Co-Authors: Junpeng Huang, Jianhua Fan, Simon Furbo
    Abstract:

    Abstract Solar thermal has contributed little for space Heating in China. In 2014, although China shared 75.8% of the total Solar collector installations in the world, only less than 0.3% of the Solar collectors were used for space Heating. To promote Solar District Heating (SDH) in China, based on Danish experiences and Chinese clean Heating transformation practices, a PEST (policy, economics, social, and technology) analysis and a SWOT (strengths, weaknesses, opportunities, and threats) analysis on SDH development in China were conducted. An extensive survey and on-site investigation were carried out to identify the applicability of SDH in rural areas. SDH development strategies, roadmap, and decision-making process for a SDH project are summarized. SDH has a broad application prospect in China with abundant Solar resources and favorable policies. The Solar heated floor area can achieve 756 million m2 with an assumption of 3% coverage of the total heat demand of buildings. Particular areas with low population density, scarce resources, and strict environmental requirements, e.g., Tibet, should be given a high priority for SDH. Rural villages and small towns with better infrastructure, e.g., District Heating networks, are the best target market for SDH in the next five years. With the development of seasonal heat storage technologies and the accumulation of practical experience, SDH can be expanded to industrial parks, large residential communities in sparsely populated northwest China. Integration of Solar heat with existing Heating networks in big cities with central Heating will be challenging in the long run.

  • Economic analysis and optimization of combined Solar District Heating technologies and systems
    Energy, 2019
    Co-Authors: Junpeng Huang, Jianhua Fan, Simon Furbo, Daochuan Chen, Yanjun Dai, Weiqiang Kong
    Abstract:

    Abstract To find an optimal economic solution for Solar District Heating (SDH) in China, an evaluation model based on the levelized cost of heat (LCoH) is developed. A Python program is developed to calculate the LCoH of SDH systems using the quasi-dynamic test method. Based on these calculations, the trend of LCoH with Solar collector area under different Heating load intensities, Heating terminal units, heated areas and land rents is discussed. The optimal Solar collector area and the Solar fraction are determined for combinations of Solar thermal with four types of auxiliary heat sources, including air source heat pumps, ground source heat pumps, gas boilers and gas boilers with seasonal heat storage. The calculations show an economic optimal Solar fraction of 11%–33% for a SDH system with heat pumps. High dependency of LCoH on network temperature is found for a SDH system with gas boilers. Seasonal heat storage minimizes LCoH of a SDH system with gas boilers at 100% Solar fraction. The findings can be used as a reference for local authorities, consultants and engineers in the early energy planning to determine the optimal proportion of Solar energy in a District Heating system with the lowest operating cost.

  • thermo economic optimization of a hybrid Solar District Heating plant with flat plate collectors and parabolic trough collectors in series
    Energy Conversion and Management, 2018
    Co-Authors: Zhiyong Tian, Bengt Perers, Simon Furbo
    Abstract:

    Abstract Large-scale Solar Heating plants for District Heating networks have gained great success in Europe, particularly in Denmark. A hybrid Solar District Heating plant with 5960 m 2 flat plate collectors and 4039 m 2 parabolic trough collectors in series was built in Taars, Denmark in 2015. The Solar Heating plant was used as a reference case in this study. A validated TRNSYS-GenOpt model was set up to optimize the key design parameters of the plant, including areas of both collector types, storage size, orientation of the parabolic trough collectors and so on. This study introduces a generic method to optimize the hybrid Solar District Heating systems based on levelized cost of heat. It is found that the lowest net levelized cost of heat of hybrid Solar Heating plants could reach about 0.36 DKK/kWh. The system levelized cost of heat can be reduced by 5–9% by use of Solar collectors in the District Heating network in this study. The results also show that parabolic trough collectors are economically feasible for District Heating networks in Denmark. The generic and multivariable levelized cost of heat method can guide engineers and designers on the design, construction and control of large-scale Solar Heating plants.

Kai Sirén - One of the best experts on this subject based on the ideXlab platform.

  • Computational comparison of a novel decentralized photovoltaic District Heating system against three optimized Solar District systems
    Energy Conversion and Management, 2019
    Co-Authors: Hassam Ur Rehman, Janne Hirvonen, Risto Kosonen, Kai Sirén
    Abstract:

    Abstract Climate change is one of the biggest challenges at the present time, and to tackle such issue, Solar energy and efficient buildings, in general, can be used. The goal is to design and optimize photovoltaic based decentralized District Heating system and later compare it—economically and technically—against three different optimized typologies of Solar District Heating system in Nordic conditions. The photovoltaic based decentralized system consists of one centralized low temperature tank charged by photovoltaic and air-water heat pumps and a borehole thermal energy storage, while the decentralized high temperature tank charged by an individual water-water heat pump in each house. The centralized warm tank charges the borehole thermal energy storage. The other three systems are photovoltaic based centralized, roof-mounted Solar thermal based centralized and roof-mounted Solar thermal based decentralized District Heating systems. In Solar thermal based systems, collectors are used to directly charge the short-term storage tanks instead of the photovoltaics/heat pump combination. The proposed system is simulated using TRNSYS software. Lastly, purchased electricity and life cycle costs of the system are minimized using multi-objective optimization and the genetic algorithm. The results indicated that the decentralized photovoltaic based system outdoes all the other systems in terms of techno-economic performance. The purchased electricity can be reduced by 22% while at the same time life cycle cost can be reduced up to 40%, compared to the worst optimized system (Solar thermal based centralized system). Moreover, the decentralized photovoltaic based energy system has a payback period of 9–27 years, compared to the Solar thermal based system and the conventional single building-heat pump system, i.e. around 17–58 years and 15 years, respectively. The highest renewable energy fraction for Heating can be close to 99% for this system. The decentralization and electrical based District systems are better in terms of life cycle cost, payback period and in terms of technical performance, compared to traditional single house and Solar thermal based District Heating systems.

  • techno economic optimization and analysis of a high latitude Solar District Heating system with seasonal storage considering different community sizes
    Solar Energy, 2018
    Co-Authors: Janne Hirvonen, Hassam Ur Rehman, Kai Sirén
    Abstract:

    Abstract A Solar community meets a significant amount of its energy demand through Solar energy. In a high latitude country like Finland, the seasonal mismatch of Solar availability makes it very difficult to achieve high renewable energy fractions without seasonal storage. In this study, a Solar community located in Finland was optimized with respect to energy demand and life cycle cost. To gain better understanding of both technical and economical scaling effects, the optimization was done separately for four cases with 50, 100, 200 and 500 buildings. The study was performed for Finnish conditions using dynamic TRNSYS simulations and optimized with a genetic algorithm, using the MOBO optimization tool. The modeled energy system had Solar thermal collectors and Solar electric panels for energy generation, two centralized short-term storage tanks and a seasonal borehole thermal energy storage system (BTES) for energy storage, and a ground source heat pump for additional heat generation. The larger communities provided noticeable cost-benefits when aiming for high performance. Larger seasonal storages allowed more direct utilization of seasonally stored heat, lowering the need for the heat pump and reducing electricity demand. Comparing the best and worst performing optimal energy system, annual demand for Heating electricity was reduced by 80%. Renewable energy fractions close to 90% for Heating were possible for all community sizes, but the large communities could obtain them with about 20% lower costs.

  • Performance comparison between optimized design of a centralized and semi-decentralized community size Solar District Heating system
    Applied Energy, 2018
    Co-Authors: Hassam Ur Rehman, Janne Hirvonen, Kai Sirén
    Abstract:

    Abstract Solar thermal energy is widely recognized as one of the most important renewable energy resources. However, in high latitudes, due to various climatic and mismatch challenges, such Solar District Heating networks are difficult to implement. The objective of the paper is to optimize and compare two different design layouts and control strategies for Solar District Heating systems in Finnish conditions. The two different designs proposed are a centralized and a semi-decentralized Solar District Heating system. The centralized system consists of two centralized short-term tanks operating at different temperature levels charged by a Solar collector and heat pumps. Borehole thermal energy storage is also charged via these two centralized tanks. In contrast, the semi-decentralized system consists of one centralized low temperature tank charged by a Solar collector and a borehole thermal energy storage and decentralized high temperature tank charged by an individual heat pump in each house. In this case, borehole thermal energy storage is charged only by the centralized warm tank. These systems are designed using the dynamic simulation software TRNSYS for Finnish conditions. Later on, multi-objective optimization is carried out with a genetic algorithm using the MOBO (Multi-objective building optimizer) optimization tool, where two objectives, i.e. purchased electricity and life cycle costs, are minimized. Various design variables are considered, which included both component sizes and control parameters as inputs to the optimization. The optimization results show that in terms of life cycle cost and purchased electricity, the decentralized system clearly outperforms the centralized system. With a similar energy performance, the reduction in life cycle cost is up to 35% for the decentralized system. Both systems can achieve close to 90% renewable energy fraction. These systems are also sensitive to the prices. Furthermore, the results show that the Solar thermal collector area and seasonal storage volume can be reduced in a decentralized system to reduce the cost compared to a centralized system. The losses in the centralized system are 40–12% higher compared to the decentralized system. The results also show that in both systems, high performance is achieved when the borehole storage is wider with less depth, as it allows better direct utilization of seasonally stored heat. The system layout and controls varied the performance and life cycle cost; therefore it is essential to consider these when implementing such systems.

  • Influence of technical failures on the performance of an optimized community-size Solar Heating system in Nordic conditions
    Journal of Cleaner Production, 2018
    Co-Authors: Hassam Ur Rehman, Janne Hirvonen, Kai Sirén
    Abstract:

    Abstract There is a substantial need to accelerate the advancement and implementation of clean energy technologies in order to solve the challenges of the energy crisis and climate change. Solar Heating technology is a feasible solution among clean energy technologies. In real conditions such complex systems often suffer from different kinds of technical failures and deviations reducing the system performance. This paper focuses on the challenges of a Solar District Heating system at high latitudes, proposes an optimized solution and investigates the influence of possible failures in planning, implementation and operation phase. The configuration proposed is a heat pump connected between two tanks, using Solar-charged borehole storage to directly charge the lower temperature tank. Dynamic simulations were performed and a multi-objective optimization was carried out. The impact of the considered system solutions on the renewable energy fraction, purchased electricity and investment cost as a function of demand, Solar thermal and photovoltaic areas, tanks and borehole volumes have been evaluated. The influence of 10 different technical failures was investigated. The study showed that in the optimized system, the most serious faults were i) de-stratification of the storage tanks (23–35% increase in annual purchased electricity) ii) on-off instead of variable speed control of the Solar circulation pump (1–22% increase) and iii) reduction in heat pump performance (7–21%). These numbers of course depend on the initial assumptions, but still they show the magnitude of performance reduction some failures can achieve. Therefore, these parameters need to be considered during the implementation of such a system.

  • Design and optimization of a De-centralized community sized Solar Heating system for Nordic Region
    Proceedings of SWC2017 SHC2017, 2017
    Co-Authors: Hassam Ur Rehman, Janne Hirvonen, Kai Sirén
    Abstract:

    There is a need to accelerate the application of advanced clean energy technologies to resolve the challenges of climate change. Solar Heating is a feasible solution among clean energy technologies. These technologies are not yet highly used in high latitudes due to various challenges. This paper focuses on the community sized Solar District Heating system configuration for cold climates. The proposed configuration consists of a partially decentralized Heating system. Each individual house heat pump was connected between large centralized Solar-charged low temperature tank and smaller de-centralized individual high temperature tank in each house. Additionally, the large centralized tank was directly charged by Solar-charged borehole storage during winters. Dynamic simulation approach was used through TRNSYS software coupled with MOBO (multi-objective building optimizer) for NSGA-II optimization algorithm. The purchased electricity and investments were two objectives minimized. The impact of the energy system on the renewable energy fraction, purchased electricity and investments as a function of the building Heating demand, collectors and photovoltaic areas, short-term tanks storages and boreholes volumes were evaluated. Results showed that purchased electricity varied 47 kWh/m2/yr-25 kWh/m2/yr and renewable energy fraction 75%-91%.Peer reviewe

Christian Holter - One of the best experts on this subject based on the ideXlab platform.

  • BIG Solar Graz: Solar District Heating in Graz – 500,000 m2 for 20% Solar Fraction
    Energy Procedia, 2016
    Co-Authors: Patrick Reiter, Hannes Poier, Christian Holter
    Abstract:

    Abstract District Heating (DH) became a central technology for providing heat and hot water in the residential and service building sector of the city of Graz over the years. It covers with approximately 1000 GWh/a (in 2013) 39% of the overall heat demand and is planned to be extended extensively in the coming years. Current heat generation for Graz is mainly from waste heat from fossil fired combined heat and power (CHP) plants in and nearby Graz. The operator of these plants announced their closure in 2020 due to low electricity prices in the European market (gas plants) and due to maturity (coal plants). Thus vanished 80% of heat production need to be replaced. Therefore, in 2014 the Graz city senate constituted a project team to find various options for providing heat for DH in Graz and its surrounding communities for 2020/30. One promising concept is a large scale Solar thermal system including seasonal storages and heat pumps. The local energy provider agreed to carry out a feasibility of such a large-scale Solar thermal power plant in order to analyze its potential in detail, whereas first results of this study are presented within the present paper. The purpose of the feasibility is to determine the optimum size of the Solar system to be best integrated in the future District Heating system. The feasibility study includes the investigation of appropriate areas for collectors and storages, the design of a technical concept using dynamic simulation, an economical evaluation and the investigation of legal issues. The price to be compared with is the heat production cost from gas boilers. First results show the best feasibility of the system between 150,000 m2 and 650,000 m2, providing 9 to 26% Solar fraction of District heat demand. While the study is ongoing first results show a high potential for the large scale Solar system being a feasible concept for the urban District Heating of Graz. Further in depth simulations will be done after all relevant parameters have been clarified in detail. Thereby economical optimization and the definition of the final dimensions of the whole system will be done.

  • big Solar graz Solar District Heating in graz 500 000 m2 for 20 Solar fraction
    Energy Procedia, 2016
    Co-Authors: Patrick Reiter, Hannes Poier, Christian Holter
    Abstract:

    Abstract District Heating (DH) became a central technology for providing heat and hot water in the residential and service building sector of the city of Graz over the years. It covers with approximately 1000 GWh/a (in 2013) 39% of the overall heat demand and is planned to be extended extensively in the coming years. Current heat generation for Graz is mainly from waste heat from fossil fired combined heat and power (CHP) plants in and nearby Graz. The operator of these plants announced their closure in 2020 due to low electricity prices in the European market (gas plants) and due to maturity (coal plants). Thus vanished 80% of heat production need to be replaced. Therefore, in 2014 the Graz city senate constituted a project team to find various options for providing heat for DH in Graz and its surrounding communities for 2020/30. One promising concept is a large scale Solar thermal system including seasonal storages and heat pumps. The local energy provider agreed to carry out a feasibility of such a large-scale Solar thermal power plant in order to analyze its potential in detail, whereas first results of this study are presented within the present paper. The purpose of the feasibility is to determine the optimum size of the Solar system to be best integrated in the future District Heating system. The feasibility study includes the investigation of appropriate areas for collectors and storages, the design of a technical concept using dynamic simulation, an economical evaluation and the investigation of legal issues. The price to be compared with is the heat production cost from gas boilers. First results show the best feasibility of the system between 150,000 m2 and 650,000 m2, providing 9 to 26% Solar fraction of District heat demand. While the study is ongoing first results show a high potential for the large scale Solar system being a feasible concept for the urban District Heating of Graz. Further in depth simulations will be done after all relevant parameters have been clarified in detail. Thereby economical optimization and the definition of the final dimensions of the whole system will be done.

  • big Solar graz Solar District Heating in graz 500 000 m2 for 20 Solar fraction
    Energy Procedia, 2016
    Co-Authors: Patrick Reiter, Hannes Poier, Christian Holter
    Abstract:

    Abstract District Heating (DH) became a central technology for providing heat and hot water in the residential and service building sector of the city of Graz over the years. It covers with approximately 1000 GWh/a (in 2013) 39% of the overall heat demand and is planned to be extended extensively in the coming years. Current heat generation for Graz is mainly from waste heat from fossil fired combined heat and power (CHP) plants in and nearby Graz. The operator of these plants announced their closure in 2020 due to low electricity prices in the European market (gas plants) and due to maturity (coal plants). Thus vanished 80% of heat production need to be replaced. Therefore, in 2014 the Graz city senate constituted a project team to find various options for providing heat for DH in Graz and its surrounding communities for 2020/30. One promising concept is a large scale Solar thermal system including seasonal storages and heat pumps. The local energy provider agreed to carry out a feasibility of such a large-scale Solar thermal power plant in order to analyze its potential in detail, whereas first results of this study are presented within the present paper. The purpose of the feasibility is to determine the optimum size of the Solar system to be best integrated in the future District Heating system. The feasibility study includes the investigation of appropriate areas for collectors and storages, the design of a technical concept using dynamic simulation, an economical evaluation and the investigation of legal issues. The price to be compared with is the heat production cost from gas boilers. First results show the best feasibility of the system between 150,000 m2 and 650,000 m2, providing 9 to 26% Solar fraction of District heat demand. While the study is ongoing first results show a high potential for the large scale Solar system being a feasible concept for the urban District Heating of Graz. Further in depth simulations will be done after all relevant parameters have been clarified in detail. Thereby economical optimization and the definition of the final dimensions of the whole system will be done.

Sergio Sibilio - One of the best experts on this subject based on the ideXlab platform.

  • Integration of Micro-Cogeneration Units and Electric Storages into a Micro-Scale Residential Solar District Heating System Operating with a Seasonal Thermal Storage
    Energies, 2020
    Co-Authors: Antonio Rosato, Antonio Ciervo, Giovanni Ciampi, Michelangelo Scorpio, Sergio Sibilio
    Abstract:

    A micro-scale District Heating network based on the operation of Solar thermal collectors coupled to a long-term borehole thermal storage is modeled, simulated and investigated over a period of five years. The plant is devoted to covering the domestic hot water and space Heating demands of a District composed of six typical residential buildings located in Naples (southern Italy). Three alternative natural gas-fueled back-up auxiliary systems (condensing boiler and two different technologies of micro-cogeneration) aiming at balancing the Solar energy intermittency are investigated. The utilization of electric storages in combination with the cogeneration systems is also considered with the aim of improving the self-consumption of cogenerated electric energy; heat recovery from the distribution circuit is also evaluated to pre-heat the mains water for domestic hot water production. The performances of the proposed plant schemes are contrasted with those of a typical Italian decentralized Heating plant (based on the utilization of natural gas-fueled non-condensing boilers). The comparison highlighted that the proposed configurations can decrease the primary energy consumption (up to 11.3%), the equivalent emissions of carbon dioxide (up to 11.3%), and the operation costs (up to 14.3%), together with an acceptable simple pay-back period (about 4.4 years).

  • Effects of Solar field design on the energy, environmental and economic performance of a Solar District Heating network serving Italian residential and school buildings
    Renewable Energy, 2019
    Co-Authors: Antonio Rosato, Antonio Ciervo, Giovanni Ciampi, Sergio Sibilio
    Abstract:

    Abstract In this paper a centralized hybrid renewable District Heating system based on the exploitation of Solar energy and integrated with a seasonal borehole thermal energy storage is investigated with reference to a 5-year period by means of the dynamic simulation software TRNSYS. The plant is devoted to satisfy the energy demand for Heating purposes and domestic hot water (DHW) production of a small-scale District composed of six residential buildings and three schools under the climatic conditions of Naples (south of Italy). Four configurations of the Solar field consisting of different combinations of Solar thermal collectors (SCs) and photovoltaic/thermal panels (PVTs) are analyzed upon varying both (i) the technology of SCs (flat plate or evacuated tube heat pipe) as well as (ii) the control logic of Solar circuit (operation with constant or variable flow rate of heat carrier fluid). The simulation results have been compared with those associated to a conventional decentralized Heating system in terms of primary energy consumption, carbon dioxide equivalent emissions and operating costs in order to assess (i) the potential energy, environmental and economic benefits as well as (ii) the impact of Solar field design on the overall system performance.

  • Integration of Micro-Cogeneration into a Solar Heating Network Operating with a Seasonal Borehole Thermal Energy Storage while Serving a Small-Scale Italian Residential District
    Midori Printing CO. LTD., 2019
    Co-Authors: Antonio Ciervo, Antonio Rosato, Giovanni Ciampi, Sergio Sibilio, Michelangelo Scorpio
    Abstract:

    A micro-scale Solar District Heating network integrated with a seasonal borehole thermal energy storage is modelled, simulated and analysed over a 5-year period. The system is devoted to satisfying the Heating demand of a District consisting of 6 typical single-family houses under the climatic conditions of Naples (south of Italy). The proposed plant is investigated by considering three alternative natural gas-fuelled back-up systems (boiler and micro-cogeneration units) in order to compensate the intermittency of Solar source. The performance of the District Heating network are compared with those of a conventional decentralized plant in order to assess the potential energy, environmental and economic benefits

  • Thermo-economic sensitivity analysis by dynamic simulations of a small Italian Solar District Heating system with a seasonal borehole thermal energy storage
    Energy, 2018
    Co-Authors: Giovanni Ciampi, Antonio Rosato, Sergio Sibilio
    Abstract:

    Abstract Solar energy is a promising option for reducing both energy consumption and harmful gas emissions. Seasonal thermal energy storage is a challenging key technology able to minimize the mismatch between the availability of the Solar energy and the thermal energy demand. In this paper, a Solar District Heating system (basically composed of a Solar collectors array, a short-term thermal energy storage (STTES), a long-term borehole thermal energy storage (BTES), an auxiliary natural gas-fired boiler and a heat distribution network) has been analysed by means of dynamic simulations over a 5-year period when serving a District composed of 6 typical single-family houses under the climatic conditions of Naples (center Italy). A sensitivity analysis has been carried out by simulating 27 configurations obtained by varying Solar collectors area, volume of STTES and volume of BTES. The simulations results have been compared with those associated to a conventional Heating system in terms of primary energy consumption, carbon dioxide equivalent emissions, operating costs as well as simple pay-back period in order to (i) evaluate the potential benefits, (ii) explore the influence of the components size on the system performance and (iii) establish some simple rules for the initial design of the main subsystems.

  • Dynamic performance of a Solar urban District Heating system upon varying the characteristics of seasonal thermal energy storage
    'Faculty of Mechanical Engineering and Naval Architecture Univ. of Zagreb', 2018
    Co-Authors: Antonio Rosato, Antonio Ciervo, Giovanni Ciampi, Sergio Sibilio
    Abstract:

    A Solar District Heating system serving a small-scale urban District located in Naples (Italy) is analysed by means of the software TRNSYS over a 5-year period. The plant is based on the utilization of a flat plate Solar collectors field connected to a seasonal double U-pipe vertical Borehole Thermal Energy Storage (BTES). A parametric analysis has been performed in order to analyse the performance of the District Heating network upon varying the characteristics of the BTES in terms of volume, number of boreholes, thermal conductivity of soil, thermal conductivity of grout, U-pipe spacing and heat carrier fluid. The primary energy consumption, the equivalent CO2 emissions and the operating costs of the proposed system have been evaluated based on the simulation results and compared with those associated to a conventional Heating system assumed as reference in order to assess the potential benefits achievable by optimizing the long-term storage design

Hassam Ur Rehman - One of the best experts on this subject based on the ideXlab platform.

  • Towards positive energy communities at high latitudes
    'Elsevier BV', 2021
    Co-Authors: Hassam Ur Rehman, Reda Francesco, Paiho Satu, Hasan Ala
    Abstract:

    Solar and wind energy are the significant renewable energy sources that can be used to tackle the climate change issue. The aim of the study is to design and compare different architectures of community-level energy systems, in order to find a positive energy community in cold climate. The design proposed is a centralized Solar District Heating network, which is integrated with renewable-based electricity network to meet the Heating and electrical demand of a community of 100 houses. The renewable-based energy system consists of photovoltaic panels, wind turbines and stationary electrical storage. In present study the demand of the building appliances, District Heating network auxiliaries and electric vehicles are included. TRNSYS is used to simulate these systems. Lastly, multi-objective optimization is done using MOBO (Multi-objective optimization tool). The objective of the optimization problem is to minimize two objective functions-the imported electricity and the life cycle costs. The onsite energy fraction, matching and exported electricity are also evaluated for comparison. The optimization results illustrate that in terms of imported energy, the cases with 600 kW (200 wind turbines) and storages are better compared to the cases without the turbines and storage. For the high performing system (200 turbines with storages and 75 electric vehicles), the corresponding onsite energy fraction (OEF) varied from 1% to 97% and the onsite energy matching (OEM) varied from 76% to 62%, respectively, while the imported electricity can be reduced to 2 kWh/m2/yr. However without storage, the onsite energy fraction (OEF) varied from 1% to 58% and the onsite energy matching (OEM) varied from 90% to 27% respectively. In all the systems, initially investments are made in the wind turbines, storages and lastly in the photovoltaic panels to improve the performance of the optimized solutions. It is found that storages can improve the onsite fraction and matching. Moreover, photovoltaic becomes more important in the cases with higher number of electric vehicles.Peer reviewe

  • Performance comparison between optimized design of a centralized and semi-decentralized community size Solar District Heating system
    'Elsevier BV', 2020
    Co-Authors: Hassam Ur Rehman, Hirvonen Janne, Sirén Kai
    Abstract:

    Solar thermal energy is widely recognized as one of the most important renewable energy resources. However, in high latitudes, due to various climatic and mismatch challenges, such Solar District Heating networks are difficult to implement. The objective of the paper is to optimize and compare two different design layouts and control strategies for Solar District Heating systems in Finnish conditions. The two different designs proposed are a centralized and a semi-decentralized Solar District Heating system. The centralized system consists of two centralized short-term tanks operating at different temperature levels charged by a Solar collector and heat pumps. Borehole thermal energy storage is also charged via these two centralized tanks. In contrast, the semi-decentralized system consists of one centralized low temperature tank charged by a Solar collector and a borehole thermal energy storage and decentralized high temperature tank charged by an individual heat pump in each house. In this case, borehole thermal energy storage is charged only by the centralized warm tank. These systems are designed using the dynamic simulation software TRNSYS for Finnish conditions. Later on, multi-objective optimization is carried out with a genetic algorithm using the MOBO (Multi-objective building optimizer) optimization tool, where two objectives, i.e. purchased electricity and life cycle costs, are minimized. Various design variables are considered, which included both component sizes and control parameters as inputs to the optimization. The optimization results show that in terms of life cycle cost and purchased electricity, the decentralized system clearly outperforms the centralized system. With a similar energy performance, the reduction in life cycle cost is up to 35% for the decentralized system. Both systems can achieve close to 90% renewable energy fraction. These systems are also sensitive to the prices. Furthermore, the results show that the Solar thermal collector area and seasonal storage volume can be reduced in a decentralized system to reduce the cost compared to a centralized system. The losses in the centralized system are 40–12% higher compared to the decentralized system. The results also show that in both systems, high performance is achieved when the borehole storage is wider with less depth, as it allows better direct utilization of seasonally stored heat. The system layout and controls varied the performance and life cycle cost; therefore it is essential to consider these when implementing such systems.Peer reviewe

  • Influence of technical failures on the performance of an optimized community-size Solar Heating system in Nordic conditions
    'Elsevier BV', 2019
    Co-Authors: Hassam Ur Rehman, Hirvonen Janne, Sirén Kai
    Abstract:

    There is a substantial need to accelerate the advancement and implementation of clean energy technologies in order to solve the challenges of the energy crisis and climate change. Solar Heating technology is a feasible solution among clean energy technologies. In real conditions such complex systems often suffer from different kinds of technical failures and deviations reducing the system performance. This paper focuses on the challenges of a Solar District Heating system at high latitudes, proposes an optimized solution and investigates the influence of possible failures in planning, implementation and operation phase. The configuration proposed is a heat pump connected between two tanks, using Solar-charged borehole storage to directly charge the lower temperature tank. Dynamic simulations were performed and a multi-objective optimization was carried out. The impact of the considered system solutions on the renewable energy fraction, purchased electricity and investment cost as a function of demand, Solar thermal and photovoltaic areas, tanks and borehole volumes have been evaluated. The influence of 10 different technical failures was investigated. The study showed that in the optimized system, the most serious faults were i) de-stratification of the storage tanks (23–35% increase in annual purchased electricity) ii) on-off instead of variable speed control of the Solar circulation pump (1–22% increase) and iii) reduction in heat pump performance (7–21%). These numbers of course depend on the initial assumptions, but still they show the magnitude of performance reduction some failures can achieve. Therefore, these parameters need to be considered during the implementation of such a system.Peer reviewe

  • Towards positive energy communities at high latitudes
    Energy Conversion and Management, 2019
    Co-Authors: Hassam Ur Rehman, Francesco Reda, Satu Paiho, Ala Hasan
    Abstract:

    Abstract Solar and wind energy are the significant renewable energy sources that can be used to tackle the climate change issue. The aim of the study is to design and compare different architectures of community-level energy systems, in order to find a positive energy community in cold climate. The design proposed is a centralized Solar District Heating network, which is integrated with renewable-based electricity network to meet the Heating and electrical demand of a community of 100 houses. The renewable-based energy system consists of photovoltaic panels, wind turbines and stationary electrical storage. In present study the demand of the building appliances, District Heating network auxiliaries and electric vehicles are included. TRNSYS is used to simulate these systems. Lastly, multi-objective optimization is done using MOBO (Multi-objective optimization tool). The objective of the optimization problem is to minimize two objective functions-the imported electricity and the life cycle costs. The onsite energy fraction, matching and exported electricity are also evaluated for comparison. The optimization results illustrate that in terms of imported energy, the cases with 600 kW (200 wind turbines) and storages are better compared to the cases without the turbines and storage. For the high performing system (200 turbines with storages and 75 electric vehicles), the corresponding onsite energy fraction (OEF) varied from 1% to 97% and the onsite energy matching (OEM) varied from 76% to 62%, respectively, while the imported electricity can be reduced to 2 kWh/m2/yr. However without storage, the onsite energy fraction (OEF) varied from 1% to 58% and the onsite energy matching (OEM) varied from 90% to 27% respectively. In all the systems, initially investments are made in the wind turbines, storages and lastly in the photovoltaic panels to improve the performance of the optimized solutions. It is found that storages can improve the onsite fraction and matching. Moreover, photovoltaic becomes more important in the cases with higher number of electric vehicles.

  • Computational comparison of a novel decentralized photovoltaic District Heating system against three optimized Solar District systems
    Energy Conversion and Management, 2019
    Co-Authors: Hassam Ur Rehman, Janne Hirvonen, Risto Kosonen, Kai Sirén
    Abstract:

    Abstract Climate change is one of the biggest challenges at the present time, and to tackle such issue, Solar energy and efficient buildings, in general, can be used. The goal is to design and optimize photovoltaic based decentralized District Heating system and later compare it—economically and technically—against three different optimized typologies of Solar District Heating system in Nordic conditions. The photovoltaic based decentralized system consists of one centralized low temperature tank charged by photovoltaic and air-water heat pumps and a borehole thermal energy storage, while the decentralized high temperature tank charged by an individual water-water heat pump in each house. The centralized warm tank charges the borehole thermal energy storage. The other three systems are photovoltaic based centralized, roof-mounted Solar thermal based centralized and roof-mounted Solar thermal based decentralized District Heating systems. In Solar thermal based systems, collectors are used to directly charge the short-term storage tanks instead of the photovoltaics/heat pump combination. The proposed system is simulated using TRNSYS software. Lastly, purchased electricity and life cycle costs of the system are minimized using multi-objective optimization and the genetic algorithm. The results indicated that the decentralized photovoltaic based system outdoes all the other systems in terms of techno-economic performance. The purchased electricity can be reduced by 22% while at the same time life cycle cost can be reduced up to 40%, compared to the worst optimized system (Solar thermal based centralized system). Moreover, the decentralized photovoltaic based energy system has a payback period of 9–27 years, compared to the Solar thermal based system and the conventional single building-heat pump system, i.e. around 17–58 years and 15 years, respectively. The highest renewable energy fraction for Heating can be close to 99% for this system. The decentralization and electrical based District systems are better in terms of life cycle cost, payback period and in terms of technical performance, compared to traditional single house and Solar thermal based District Heating systems.