1,720,979 research outputs found
Investment analysis of gas-turbine combined heat and power systems for commercial buildings under different climatic and market scenarios
No full textThe aim of the proposed work is to investigate the technical and economic suitability of a gas turbine combined heat and power system in commercial buildings. These systems are widely recognised as a promising technology to provide significant fuel savings and carbon emissions reduction where they have been widely used in industrial settings due to the relatively constant electrical and thermal loads required for industrial processes. However, their deployment has been relatively stagnant over the last few decades due to challenges such as poor planning and policy measures, energy market changes and regulatory barriers. In this context, a preliminary system design and optimisation procedure has been developed based on a sensitivity analysis of different scenarios of building loads, market and weather conditions. The optimisation is performed considering several technical and environmental parameters (e.g., energy and exergy efficiencies and primary energy saving), as well as economic indexes (e.g., net present value, pay-back period, profitability, etc.). This allows the suitability assessment of the investment for different market price scenarios under different heating degree days demand scenarios. The analysis is carried out using an Italian case study as it exhibits a wide range of heating degree days variability, while subject to a single pricing market. Results show that strong correlations occur between the technical and economic performance indices and the weather conditions for all considered configurations. The methodology and conclusions, if coupled with the possibility of applying clustering techniques to determine common patterns of energy consumptions in building blocks, represent a powerful toolset to carry out preliminary techno-economic assessment of a combined heat and power system
Optimal control of fan coil battery air and water flow rates requiring minimal on-line measurements
No full textFan coil units are widely used in air-conditioning systems for heating and cooling of commercial buildings. Control - capable of achieving better operational efficiencies and at the same time, guarantying thermal comfort - is paramount in order to achieve optimal operation. The present paper presents a novel generalised control strategy, requiring only minimal input data, for optimising fan speed in order to reduce. Different control models are implemented to predict fan coil capacities and associated total power consumption. The developed strategy has been compared to fixed speed and benchmark fan speed control strategies, using both a steady state and a quasi-steady state algorithm, for various building loads. Results show average reduction in fan coil battery power consumption of 34% and 43% in heating and cooling mode respectively, when the optimal control is compared to fixed fan speed settings. Savings between 4.9% and 9.1% can be achieved by the control algorithms if compared to the benchmark fan speed control strategies
Diversification, concentration and renewability of the energy supply in the European Union
No full textEnergy security assessment quantifies the energy supply to a population and the likelihood, or risk, of an energy disruption or shortage and represents an important aspect of national security, economic stability and prosperity. The quantification of the state of energy supply is context-dependent and involves multiple perspectives: infrastructural, technological, environmental, market, social and geopolitical. Among all the different and relevant aspects involved, diversity and dependence of the energy fuel mix are two of the main energy security dimensions. The present paper investigates the diversification of the energy supply in Europe, by analysing import dependence, market concentration and renewable energy resource deployment in the European Union over the last decade. The analysis utilises a set of indicators aimed at measuring the fuel mix diversity, market concentration, geopolitical stability, renewable energy share and stochasticity - both at single country and at aggregated European levels. Results show a stable evolution of the diversity of the fuel mix and a relatively low market concentration of the period examined. However, the import dependency reduces the energy security by approximately 30% due to the high proportion of imports from a limited number of countries. Moreover, an increasing trend in renewable electricity production share is evident over the last decade, albeit with differences between member states, as a result of the decarbonisation policies implemented by the European Union
Environmental and economic benefits of building retrofit measures for the residential sector by utilizing sensor data and advanced calibrated models
No full textThe present paper investigates the energy savings associated with the implementation of retrofitting measures on Irish residential buildings. A detached residential dwelling, representative of approximately 40% of the residential stock in Ireland, was selected as experimental test bed. The building was progressively retrofitted to an all-electric dwelling. Retrofit measures included the installation of a photovoltaic array, a geothermal heat pump, an electric vehicle charging point, along with building fabric upgrades. The building was equipped with a home area network with more than 30 sensors with 15 min monitoring resolution. The experimental data collected during the experimental campaign aided the comprehensive calibration of an EnergyPlus model. This model was used to investigate the effectiveness of the implemented retrofit measures in terms of energy savings and CO2 reductions. Real-time data from the Irish power system operator was used to calculate the building carbon footprint for different levels of renewable energy penetration to the national grid. Results show that the all-electric retrofitted building can achieve energy savings of up to 45%, with CO2 reductions of approximately 29%, compared to the pre-retrofitted building. Implementing the retrofit measures at scale could potentially lead to carbon emission reductions up to 14% for rural areas in Ireland
Data-driven predictive control for unlocking building energy flexibility: A review
No full textManaging supply and demand in the electricity grid is becoming more challenging due to the increasing penetration of variable renewable energy sources. As significant end-use consumers, and through better grid integration, buildings are expected to play an expanding role in the future smart grid. Predictive control allows buildings to better harness available energy flexibility from the building passive thermal mass. However, due to the heterogeneous nature of the building stock, developing computationally tractable control-oriented models, which adequately represent the complex and nonlinear thermal-dynamics of individual buildings, is proving to be a major hurdle. Data-driven predictive control, coupled with the “Internet of Things”, holds the promise for a scalable and transferrable approach, with data-driven models replacing traditional physics-based models. This review examines recent work utilising data-driven predictive control for demand side management application with a special focus on the nexus of model development and control integration, which to date, previous reviews have not addressed. Further topics examined include the practical requirements for harnessing passive thermal mass and the issue of feature selection. Current research gaps are outlined and future research pathways are suggested to identify the most promising data-driven predictive control techniques for grid integration of buildings
Energy assessment of hybrid heat pump systems as a retrofit measure in residential housing stock
No full textHybrid electric-gas heat pump systems are a possible retrofit option in older residential buildings. Older buildings can be challenging to retrofit and in this context hybrid systems can offer an intermediate route to decarbonisation of building heating energy demand. This is especially the case, where deep retrofit measures coupled with monovalent electric heat pump systems may not be feasible from an economic perspective. The aim of the current paper is to examine the suitability of a hybrid electric-gas heat pump system in comparison to electric heat pump systems as a retrofit measure for Irish housing stock and to benchmark both options against existing fossil fuel baseline systems. A detailed building energy model of a residential dwelling was developed and calibrated to within acceptable ASHRAE standards. An energy assessment was carried out which investigates each retrofit scenario. Key findings include: (i) both the all-electric and hybrid heat pump systems deliver primary energy savings compared to the fossil fuel baseline systems, (ii) hybrid systems attain higher primary energy savings compared to all-electric heat pump, where the hybrid system incorporates flexible delivery temperatures compared to a fixed delivery temperature tor the all-electric heat pump system
Flexibility assessment of a combined heat-power system (CHP) with energy storage under real-time energy price market framework
No full textThe use of on-site generation can significantly enhance the primary energy savings of a building while acting as a hedge against rising electricity prices. Among other techniques, combined heat and power systems have proved to be reliable and economically suitable technologies in building applications and provision for their promotion has been set out by the European Union over the last few years. Moreover, demand side management programs can provide additional revenue streams which can further benefit the feasibility of combined heat and power technology in a commercial building while providing services to the grid network. In this context, the aim of the present paper is to investigate the techno-economic performance and energy flexibility potential for demand response programs of a gas turbine combined heat and power unit with thermal and electrical storage in commercial buildings. A short assessment overview on demand side management and demand response programs, with a special focus on combined heat and power systems, is provided to introduce the main aspects of these initiatives. Combined heat and power system, technical parameters and operating control strategies are investigated to determine their effects on system efficiencies and economics. Finally, real time pricing and energy storage are examined to establish the implications on a combined heat and power system in a demand-side management framework. Results show that savings of 7% can be obtained by the introduction of thermal energy storage systems, making them suitable for combined heat and power systems in building applications. Operating in a real-time market, the year-on-year savings associated with the combined heat and power are greater than when fixed rate tariffs are considered, especially with the electric energy storage system installed, since it allows the exploitation of price fluctuations. However, the current high investment cost of electric storage makes this solution economically unsuitable, leading to poorer combined heat and power economic performance
On the assessment and control optimisation of demand response programs in residential buildings
No full textThe ability to control and optimise energy consumption at end-user level is of increasing interest as a means to achieve a balance between supply and demand, particularly when large penetration of distributed renewable energy sources is being considered. Demand Response programs consist of a series of externally-driven control strategies aimed at adapting consumer end-use load to specific grid requirements. In a demand response scenario, a network of connected systems can be exploited to activate balancing strategies, to provide demand flexibility during periods of high stress for the grid. However, the widespread deployment of demand response programs in the building sector still faces significant challenges. Smart technology deployment, the lack of common standardised assessment procedures and metrics, the absence of established regulatory frameworks are among the main obstacles limiting the development of portfolios of competitive flexibility assets. The residential sector is even more affected by these challenges due to a marginal economic case, the issue of long term harmonisation of hardware and software infrastructure and the influence of the end-user behaviour and preferences on energy consumption. The present paper provides a review on the current developments of the Demand Response programs, with specific reference to the residential building sector. Methodologies and procedures for assessing building energy flexibility and Demand Response programs are described with a special focus on numerical models and available control algorithms. Moreover, markets schemes and social aspects - such as technology acceptance and awareness - and their influence on smart control technologies and algorithms are discussed. Current research gaps and challenges are identified and analysed to provide guidance for future research activities
Technical and economic assessment of a hybrid heat pump system as an energy retrofit measure in a residential building
No full textAir to water electric heat pumps are one technological solution to achieve energy defossilisation goals for heating of residential building stock. Nevertheless, they may not necessarily be the only solution for all residential building stock. A case in point is where extensive fabric refurbishment is impracticable or where electric heat pumps are installed where low ambient temperatures prevail and/or high water delivery temperatures must be utilised. For such instances, hybrid (gas and electric) heat pumps offer an alternative option by facilitating fuel source switching between electricity and gas, when ambient temperatures are low or high water supply temperatures are required. In the current study, the effectiveness of an air-to-water electric heat pump and hybrid heat pump are examined for different building retrofit scenarios for a residential dwelling located in Ireland. This is achieved by means of a sensitivity study of a validated building simulation model, incorporating both heat pump systems, subject to different building retrofit scenarios. Relative to a conventional oil-fired boiler, for a deep building retrofit scenario, the hybrid and electric heat pumps achieve primary energy reduction of 128 kWh/m2/year (72%) and of 123 kWh/m2/year (70%), respectively. Considering the associated carbon footprints, the reductions were found to be 29.7 gCO2e/m2/year (74%) for the hybrid heat pump, and 27.6 gCO2e/m2/year (68%) for the electric heat pump. Finally, the deployment of either an electric heat pump or hybrid heat pump for deep building fabric retrofit achieves approximately half of the heating system capital cost return within 20 years
Demand response algorithms for smart-grid ready residential buildings using machine learning models
No full textThis paper assesses the performance of control algorithms for the implementation of demand response strategies in the residential sector. A typical house, representing the most common building category in Ireland, was fully instrumented and utilised as a test-bed. A calibrated building simulation model was developed and used to assess the effectiveness of demand response strategies under different time-of-use electricity tariffs in conjunction with zone thermal control. Two demand response algorithms, one based on a rule-based approach, the other based on a predictive-based (machine learning) approach, were deployed for control of an integrated heat pump and thermal storage system. The two algorithms were evaluated using a common demand response price scheme. Compared to a baseline reference scenario, the following reductions were observed: electricity end-use expenditure (20.5% rule-based and 41.8% predictive algorithm), utility generation cost (18.8% rule-based and 39% predictive algorithm), carbon emissions (20.8% rule-based and 37.9% predictive algorithm)
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