Analysis of the economic feasibility and reduction of a building’s energy consumption and emissions when integrating hybrid solar thermal/PV/micro-CHP systems

The aim of this paper is to assess the performance of several designs of hybrid systems composed of solar thermal collectors, photovoltaic panels and natural gas internal combustion engines. The software TRNSYS 17 has been used to perform all the calculations and data processing, as well as an optimisation of the tank volumes through an add-in coupled with the GENOPT® software. The study is carried out by analysing the behaviour of the designed systems and the conventional case in five different locations of Spain with diverse climatic characteristics, evaluating the same building in all cases. Regulators, manufacturers and energy service engineers are the most interested in these results. Two major contributions in this paper are the calculations of primary energy consumption and emissions and the inclusion of a Life Cycle Cost analysis. A table which shows the order of preference regarding those criteria for each considered case study is also included. This was fulfilled in the interest of comparing between the different configurations and climatic zones so as to obtain conclusions on each of them. The study also illustrates a sensibility analysis regarding energy prices. Finally, the exhaustive literature review, the novel electricity consumption profile of the building and the illustration of the influence of the cogeneration engine working hours are also valuable outputs of this paper, developed in order to address the knowledge gap and the ongoing challenges in the field of distributed generation

Optimization of a small-scale polygeneration system for a household in Turkey

With environmental concerns, alternative solutions for generating electricity while decreasing the consumption of fossil fuels have gained a great importance. Polygeneration is one of these solutions which is also capable to increase the technical performance of electricity generation. Polygeneration systems are available in large scale, medium scale and small scale. This study focuses on small scale polygeneration systems specifically for residential applications. Type and size of the components and the system’s operational strategy plays a significant role in polygeneration system design as these factors affect the system cost and also environmental impacts. This study aims to propose a guide for component selection, sizing and addressing a suitable operational strategy for a predefined system configuration. Decision making criteria is defined for component selection by a comprehensive literature review. Internal combustion engines, Stirling engines, micro gas turbines and fuel cells are investigated within these criteria. This provides the user an insight on component selection. When combined with factors such as market conditions, location and especially household demand profile, a selection can easily be made by the customer. For component sizing and operational strategy, a model has been implemented in Matlab. A baseline case model with a predefined system configuration and operational strategy was defined. The baseline case system includes a prime mover, a back-up auxiliary boiler, a vapor compression refrigeration chiller, a thermal energy storage and solar thermal collectors for the domestic hot water demand. The operational strategy is defined as thermal load following. For the case study, this model was altered for different cases with alterations on the operational strategy and the system configuration in order to identify the optimal solution for the user where the total annual cost is minimized while satisfying all kinds of end-use demands of a single-family household in Ankara, Turkey. The results also give insights on the effect of having solar thermal collectors and a thermal energy storage coupled with a CHP unit on the overall system

A Combined Organic Rankine Cycle-Heat Pump System for Domestic Hot Water Application

This paper investigates a novel system to improve the efficiency of using natural gas for domestic heating. The exhaust from a gas burner powers a small-scale Organic Rankine Cycle (ORC) system using hexane as the working fluid, which is used to directly drive the compressor of a heat pump, using R134a as the working fluid. Water is heated from ambient by passing it through three heat exchangers, the condenser of the Heat Pump, the condenser of the ORC, and the secondary heat exchanger that is heated by the hot flue gas from the burner after it transfers the heat to the evaporator of the ORC subsystem. By using the heat generated from the burning of gas in a burner in this way, a fuel-to-usable-heat efficiency of up to 160% is projected, outperforming the other technologies discussed, giving it the potential to significantly reduce energy demand and carbon emissions. This paper investigates the effect of varying ambient conditions upon the cycle, namely the temperature of ambient air, which has a strong effect on the performance of the heat pump

A BRIEF REVIEW ON THE ADVANTAGES, HINDRANCES AND ECONOMIC FEASIBILITY OF STIRLING ENGINES AS A DISTRIBUTED GENERATION SOURCE AND COGENERATION TECHNOLOGY

The present paper aims to provide a brief review of the potentiality and economic feasibility of the Stirling engine as a distributed generation source and cogeneration technology. Another objective was the determination of hindrances which may be preventing the feasibility of the Stirling technology. With these intentions, a research based on a combination of preselected keywords was performed at the Metasearch of CAPES (Brazil's Higher Education Coordination of Personnel Perfecting). No filters in relation to the research period or to particular geographical regions were employed, thus publications until 2017’s middle were included and the research was conducted on a global level. Next, the selection of papers which contained some of the keywords was made, consisting initially of the read of the publications’ abstracts. The remaining ones were then further explored and had their relevant information incorporated, according to the scope of this work. It is worth mentioning that other accredited sources which dealt with important aspects of the topic were also included. Furthermore, a table containing some examples of products concerning the application of the Stirling engine as a distributed generation and cogeneration technology is presented. Ultimately, it is concluded that the Stirling technology, despite its advantages and suitability regarding the proposed applications, is not yet commercially feasible, having currently only a minor presence in the market. This scenario can be attributed to the need for further research and technical development as well as cost reduction

Optimisation of stand-alone hybrid energy systems for power and thermal loads

Stand-alone hybrid energy systems are an attractive option for remote communities without a connection to a main power grid. However, the intermittent nature of solar and other renewable sources adversely affects the reliability with which these systems respond to load demands. Hybridisation, achieved by combining renewables with combustion-based supplementary prime movers, improves the ability to meet electric load requirements. In addition, the waste heat generated from backup Internal Combustion Engines or Micro Gas Turbines can be used to satisfy local heating and cooling loads. As a result, there is an expectation that the overall efficiency and Greenhouse Gas Emissions of stand-alone systems can be significantly improved through waste heat recovery. The aims of this PhD project are to identify how incremental increases to the hardware complexity of hybridised stand-alone energy systems affect their cost, efficiency, and CO2 footprint. The research analyses a range of systems, from those designed to meet only power requirements to others satisfying power and heating (Combined Heat and Power), or power plus both heating and cooling (Combined Cooling, Heating, and Power). The majority of methods used focus on MATLAB-based Genetic Algorithms (GAs). The modelling deployed finds the optimal selection of hardware configurations which satisfy single- or multi-objective functions (i.e. Cost of Energy, energy efficiency, and exergy efficiency). This is done in the context of highly dynamic meteorological (e.g. solar irradiation) and load data (i.e. electric, heating, and cooling). Results indicate that the type of supplementary prime movers (ICEs or MGT) and their minimum starting thresholds have insignificant effects on COE but have some effects on Renewable Penetration (RP), Life Cycle Emissions (LCE), CO2 emissions, and waste heat generation when the system is sized meeting electric load only. However, the transient start-up time of supplementary prime movers and temporal resolution have no significant effects on sizing optimisation. The type of Power Management Strategies (Following Electric Load-FEL, and Following Electric and Following Thermal Load- FEL/FTL) affect overall Combined Heating and Power (CHP) efficiency and meeting thermal demand through recovered heat for a system meeting electric and heating load with response to a specific load meeting reliability (Loss of Power Supply Probability-LPSP). However, the PMS has marginal effects on COE. The Electric to Thermal Load Ratio (ETLR) has no effects on COE for PV/Batt/ICE but strongly affects PV/Batt/MGT-based hybridised CHP systems. The higher thermal than the electric loads lead to higher efficiency and better environmental footprint. Results from this study also indicate that for a stand-alone hybridised system operating under FEL/FTL type PMS, the power only system has lower cost compared to the CHP and the Combined Cooling, Heating, and Power (CCHP) systems. This occurs at the expense of overall energy and exergy efficiencies. Additionally, the relative magnitude of heating and cooling loads have insignificant effects on COE for PV/Batt/ICE-based system configurations, however this substantially affects PV/Batt/MGT-based hybridised CCHP systems. Although there are no significant changes in the overall energy efficiency of CCHP systems in relation to variations to heating and cooling loads, systems with higher heating demand than cooling demand lead to better environmental benefits and renewable penetration at the cost of Duty Factor. Results also reveal that the choice of objective functions do not affect the system optimisation significantly

Energy analysis of a Micro-CHP demonstration facility

Cooling, Heating, and Power (CHP) systems have been around for decades, but systems that utilize 20 kW or less, designated as Micro-CHP, are relatively new. Micro-CHP systems show the most promise for a distributed generation scheme to decentralize the national energy grid. A demonstration site has been constructed at Mississippi State University to show the advantages of these systems. This study is designed to evaluate the performance of a Micro-CHP system and a conventional high-efficiency system. Performance and cost factors can be evaluated for the demonstration site operating under either the CHP system or the conventional system. These results are computed from an energy analysis on collected data. This dissertation introduces a new comparison factor to examine different CHP systems. This new factor is called the System Energy Transfer Ratio (SETR). Other considerations in this study include an extensive literature survey that reviews CHP systems, their components, modeling, and other topics concerning CHP systems operation. In addition, the demonstration facility will be discussed in detail presenting the various components and instrumentation. Furthermore, the energy analysis will be presented, examining the equations used to evaluate the raw data from the demonstration site. An uncertainty analysis will be presented for the experimental results. Raw data was collected for 7 months to present the following results. The combined cycle efficiency from the demonstration site was averaged at 29%. Maximum combined cycle efficiency was evaluated at 58%. The average combined boiler and engine cost, per hour of operation, is shown as $1.8 for heating and$3.9 for cooling. The cooling technology used, an absorption chiller, has been shown to exhibit an average COP of 0.27. The proposed SETR for the demonstration site is 22% and 15%, for heating and cooling, respectively. The conventional high-efficiency system, during cooling mode, was shown to have a COP of 4.7 with a combined cooling and building cost of $0.2/hour of operation. During heating mode, the conventional system had an efficiency of 47$0.28/hour of operation

Energy analysis of a Micro-CHP demonstration facility

Cooling, Heating, and Power (CHP) systems have been around for decades, but systems that utilize 20 kW or less, designated as Micro-CHP, are relatively new. Micro-CHP systems show the most promise for a distributed generation scheme to decentralize the national energy grid. A demonstration site has been constructed at Mississippi State University to show the advantages of these systems. This study is designed to evaluate the performance of a Micro-CHP system and a conventional high-efficiency system. Performance and cost factors can be evaluated for the demonstration site operating under either the CHP system or the conventional system. These results are computed from an energy analysis on collected data. This dissertation introduces a new comparison factor to examine different CHP systems. This new factor is called the System Energy Transfer Ratio (SETR). Other considerations in this study include an extensive literature survey that reviews CHP systems, their components, modeling, and other topics concerning CHP systems operation. In addition, the demonstration facility will be discussed in detail presenting the various components and instrumentation. Furthermore, the energy analysis will be presented, examining the equations used to evaluate the raw data from the demonstration site. An uncertainty analysis will be presented for the experimental results. Raw data was collected for 7 months to present the following results. The combined cycle efficiency from the demonstration site was averaged at 29%. Maximum combined cycle efficiency was evaluated at 58%. The average combined boiler and engine cost, per hour of operation, is shown as $1.8 for heating and$3.9 for cooling. The cooling technology used, an absorption chiller, has been shown to exhibit an average COP of 0.27. The proposed SETR for the demonstration site is 22% and 15%, for heating and cooling, respectively. The conventional high-efficiency system, during cooling mode, was shown to have a COP of 4.7 with a combined cooling and building cost of $0.2/hour of operation. During heating mode, the conventional system had an efficiency of 47$0.28/hour of operation

State of art of small scale solar powered ORC systems: a review of the different typologies and technology perspectives

Abstract Solar thermoelectric, even for small sizes, is continuing to garner more attention, by virtue of maturation of small size organic Rankine cycle generators, and of small size absorption chiller even if cost and reliability are still not optimal. Indeed, solar thermal power technology improvement would consent to stimulate an ambit already present in Europe and Italy with a well-known tradition and established leadership and efforts focused on a single solar technology would bring to positive effects concerning controllable electric and thermal energy uses. In this context, the present work tries to summarize the possible cycles and fluids that can be applied in a small solar thermal power plant. Despite a plethora of simulated and experimental cycles and fluids, the simplest cycle using near isentropic fluids seems to be the best choice for a small ORC-based CHP system, even if particular attention has to be done to all the sizing parameters (electricity, heating and cooling demand; area and type of solar collector; flow and temperature of the thermal carrier; flow, temperature and pressure of the working fluid; storage volumes; etc.). Indeed, efficiency and reliability of the reported systems are very different, but, it seems that global efficiency of even more than 10% and global cost of even less than 10,000 €/kW can be obtained even at size of few kW if adequate systems are constructed and managed

Selected Papers from SDEWES 2017: The 12th Conference on Sustainable Development of Energy, Water and Environment Systems

EU energy policy is more and more promoting a resilient, efficient and sustainable energy system. Several agreements have been signed in the last few months that set ambitious goals in terms of energy efficiency and emission reductions and to reduce the energy consumption in buildings. These actions are expected to fulfill the goals negotiated at the Paris Agreement in 2015. The successful development of this ambitious energy policy needs to be supported by scientific knowledge: a huge effort must be made in order to develop more efficient energy conversion technologies based both on renewables and fossil fuels. Similarly, researchers are also expected to work on the integration of conventional and novel systems, also taking into account the needs for the management of the novel energy systems in terms of energy storage and devices management. Therefore, a multi-disciplinary approach is required in order to achieve these goals. To ensure that the scientists belonging to the different disciplines are aware of the scientific progress in the other research areas, specific Conferences are periodically organized. One of the most popular conferences in this area is the Sustainable Development of Energy, Water and Environment Systems (SDEWES) Series Conference. The 12th Sustainable Development of Energy, Water and Environment Systems Conference was recently held in Dubrovnik, Croatia. The present Special Issue of Energies, specifically dedicated to the 12th SDEWES Conference, is focused on five main fields: energy policy and energy efficiency in smart energy systems, polygeneration and district heating, advanced combustion techniques and fuels, biomass and building efficiency