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

日中地域別における分散型エネルギーシステムの総合評価に関する研究

本研究では日中建築分野の省エネルギーを促進するため、地域ごと、建物種別ごとに分散型エネルギーシステム導入の最適化モデルと総合評価方法を提案し、日中における気候別都市を対象とし、分散型エネルギーシステムの導入により、建物エネルギー消費の特徴を分析したものである。北九州市立大

An Economic, Energy, and Environmental Analysis of PV/Micro-CHP Hybrid Systems: A Case Study of a Tertiary Building

Our present standard of living depends strongly on energy sources, with buildings being a primary focus when it comes to reducing energy consumption due to their large contribution, especially in tertiary buildings. The goal of the present study is to evaluate the performance of two different designs of hybrid systems, composed of natural gas engines and photovoltaic panels. This will be done through simulations in TRNSYS, considering a representative office building with various schedules of operation (8, 12, and 24 h), as well as different climates in Spain. The main contributions of this paper are the evaluations of primary energy-consumption, emissions, and economic analyses for each scenario. In addition, a sensitivity analysis is carried out to observe the influence of energy prices, as well as that of the costs of the micro-CHP engines and PV modules. The results show that the scenario with the conventional system and PV modules is the most profitable one currently. However, if electricity prices are increased in the future or natural gas prices are reduced, the scenario with micro-CHP engines and PV modules will become the most profitable option. Energy service engineers, regulators, and manufacturers are the most interested in these results

Assessing the influence of legal constraints on the integration of renewable energy technologies in polygeneration systems for buildings

Hybrid polygeneration systems offer a great opportunity to meet growing energy demands with cost efficiency and environmental benefits. The identification of the optimal solution (configuration and operational strategy) is strongly affected by the relationship between the system and its surroundings. Previous studies have analyzed the influence of boundary conditions on the synthesis of polygeneration systems for buildings. However, local regulations are often disregarded or oversimplified in those studies. Therefore, this paper aims to evaluate the influence of legal conditions on the integration of renewable energy technologies in polygeneration systems for buildings. A comprehensive synthesis model is developed, including different types of legal conditions, such as power exchange modalities, subsidies/surcharges on energy prices and investment costs, and total ban on fossil fuels. Then, the model is applied to the case study of a Brazilian hospital. The current Brazilian net metering scheme is implemented. Results show that natural gas cogeneration is an attractive solution to cover the hospital's energy demands with or without the possibility of selling/exporting electricity. Also, the Brazilian net metering scheme, by itself, is not enough to ensure renewable energy deployment. An in-depth discussion about the conditions that would promote renewable energy integration is reported and recommendations are made on how current policies can be improved, including the need to explicitly address renewable technologies, the application of minimum renewable fractions, and the role of renewable heat/cooling. While the case study considers the specific circumstances in Brazil, it provides insights that can be extended to other countries or applications

Small-Scale Compressed Air Energy Storage Application for Renewable Energy Integration in a Listed Building

In the European Union (EU), where architectural heritage is significant, enhancing the energy performance of historical buildings is of great interest. Constraints such as the lack of space, especially within the historical centers and architectural peculiarities, make the application of technologies for renewable energy production and storage a challenging issue. This study presents a prototype system consisting of using the renewable energy from a photovoltaic (PV) array to compress air for a later expansion to produce electricity when needed. The PV-integrated small-scale compressed air energy storage system is designed to address the architectural constraints. It is located in the unoccupied basement of the building. An energy analysis was carried out for assessing the performance of the proposed system. The novelty of this study is to introduce experimental data of a CAES (compressed air energy storage) prototype that is suitable for dwelling applications as well as integration accounting for architectural constraints. The simulation, which was carried out for an average summer day, shows that the compression phase absorbs 32% of the PV energy excess in a vessel of 1.7 m(3), and the expansion phase covers 21.9% of the dwelling energy demand. The electrical efficiency of a daily cycle is equal to 11.6%. If air is compressed at 225 bar instead of 30 bar, 96.0% of PV energy excess is stored in a volume of 0.25 m3, with a production of 1.273 kWh, which is 26.0% of the demand

Island-based polygeneration systems : feasibility of bBiomass-driven distributed concepts

The colossal risks and challenges posed by climate change require innovative solutions that must fulfil energy service demands sustainably. The concept of small-scale, biomass-based polygeneration (SBP) is one such technological approach, which optimizes locally supplied fuels to provide several energy services like electricity, heating, cooling, potable water, and/or bio-chemical products. By presenting chosen SBP systems and models employed in various socio-geographic locations, in particular distributed applications, the thesis identifies benefits as well as drawbacks of the SBP concept and aims to promote its wider usage in the field. Because a multitude of technologies can be applied for polygeneration system design, the thesis starts with a thorough review of the highly complex and rapidly evolving field, where relevant literature is presented and assimilated. Based on this review, several models have been created for various solar-assisted SBP systems: Firstly, a small-scale Combined Cooling, Heating, and Power (CCHP) system based on biomass gasification has been investigated for a hotel resort on one of the Andaman Islands, India. Apart from economic and environmental superiority compared to a fossil-fuel reference system, the study also expanded technological aspects by adding a socio-political analysis of the benefits and drawbacks of the system for the entire island community. In the second study, a novel control algorithm was devised for a biogas-based polygeneration system generating electricity and potable water generation for a rural off-grid village in El Pando, Bolivia. It was found that the proposed system could lead to significant cost and emissions reductions paired with greater energy autonomy. In the third study, an optimization model for a combined gasification-based CCHP/Heat Pump (HP) system is presented for a tourist facility in Barcelona considering various climate scenarios. The study reveals that the system design is only slightly affected by future changes in climate and that the CCHP/HP system shows only a moderate economic performance but still considerable CO2-savings potential. The overall findings of these studies reveal that the economic feasibility of SBP systems depends greatly not just on their inherent design but also on their location. However, all proposed polygeneration systems could lower emissions significantly, while excelling in energy efficiency as well as adaptability towards service demands and other technologies. The presented studies contribute to the state of the art by adding innovative polygeneration system designs, proposing new modelling approaches and subsequent models including SBP system enhancing technologies, as well as by investigating the effects of geographical location and climate change on the system design process.Los colosales riesgos y retos puestos por el cambio climático requieren soluciones creativas para satisfacer las demandas de servicios energéticos de una manera más sostenible, comparado con los sistemas actuales. El concepto de poligeneración a escala pequeña y basada en biomasa (Small-scale, biomass-based polygeneration o SBP) es uno de estos enfoques, que optimiza el uso de combustible locales para proveer varios servicios energéticos como electricidad, calor, enfriamiento, agua potable y/o productos bioquímicos. Presentando una selección de sistemas SBP y modelos empleados en varias localizaciones socio-geográficas, esta tesis identifica los beneficios e inconvenientes del concepto SBP con el objetivo de promover su un uso más amplio en el mundo. Como se puede aplicar una multitud de tecnologías para el diseño de sistemas SBP, la tesis empieza con una revisión profunda del campo, altamente complejo y dinámico, donde la literatura relevante está presentada en una forma estructurada y resumida. Basado en esta revisión, se han creado varios modelos SBP para varios sistemas SBP con asistencia solar: Principalmente, se ha investigado un sistema de generación conjunta de frio, calor y electricidad (en inglés: Combined Cooling, Heating, and Power or CCHP) basado en gasificación de biomasa para un resort (hotelero) en una de las islas Andamán, India. Además de mostrar de una superioridad económica y ambiental comparado con el sistema de referencia de combustibles fósiles, el estudio expandió el conocimiento científico añadiendo un análisis socio-político de los beneficios e inconvenientes del sistema SBP para la comunidad de la isla entera. En el segundo estudio, se ha desarrollado un nuevo algoritmo de control para un sistema de poligeneración basado en biogás, que genera electricidad y agua potable para una comunidad rural y sin conexión a una red eléctrica más grande en el Pando, Bolivia. Se ha revelado que el sistema propuesto podría bajar significantemente los costes y las emisiones junto con un aumento de la autonomía energética. En el tercer estudio se ha presentado un modelo de optimización para un sistema combinado de CCHP y bombas de calor (sistema CCHP/HP), que se considera para una estructura museístico-turística en Barcelona y para varios escenarios climáticos. En el estudio se ha descubierto que el cambio climático influye sólo ligeramente en el diseño del sistema óptimo, y que el sistema CCHP/HP demuestra sólo un moderado desempeño económico, similar al convencional, pero también un potencial considerable para la reducción de emisiones de CO2. El conjunto de los estudios revela que la viabilidad económica de los sistemas SBP depende altamente no solo de su diseño inherente, sino también de su entorno. De todos modos, todos los sistemas SBP propuestos podrían bajar las emisiones significantemente, mientras sobresalen en eficiencia energética y adaptabilidad a servicios energéticos y tecnologías alternativas. Los estudios presentados contribuyen al estado del arte añadiendo diseños innovadores de sistemas SBP, proponiendo nuevos enfoques de modelado y cálculo, y subsecuentemente nuevos modelos incluyendo tecnologías aumentando sistemas SBP, e investigando los efectos de la ubicación geográfica y del cambio climático al proceso del diseño de los sistemas SBP.Sammanfattning Klimatförändringen bär med sig kolossala risker och utmaningar, som kräver innovativa lösningar för att tillhandahålla energitjänster på ett mer hållbart sätt än med tidigare energisystem. Konceptet med småskaliga, biomassa-baserade polygeneration (SBP) system är ett sådant teknologiskt tillvägagångssätt, vilket optimerar användningen av lokalt producerat bränsle för att tillhandahålla olika energitjänster som elektricitet, värma, kyla, dricksvatten, eller/och bio-kemiska produkter. Doktorsarbetet identifierar för- och nackdelar hos olika SBP konceptet genom att presentera ett urval av SBP system och modeller av dem för olika geografiska regioner, med mål att främja vidare applikation av dem i fält. Eftersom en mängd tekniker kan användas för design av polygenerationssystem, börjar avhandlingen med en grundlig genomgång av det mycket komplexa och snabbt utvecklande området, där relevant litteratur presenteras och assimileras. Baserat på denna recension har flera modeller skapats för olika solassisterade SBP-system: För det första har ett småskaligt kombinerat kyl-, värme- och kraftsystem (CCHP) baserat på biomassaförgasning undersökts för en hotellanläggning på en av Andamanöarna, Indien. Bortsett från ekonomisk och miljömässig överlägsenhet jämfört med ett referenssystem för fossila bränslen har studien även inkluderat tekniska aspekter genom att lägga till en socio-politisk analys av fördelarna och nackdelarna med systemet för hela ö-samhället. I den andra studien utvecklades en ny regleralgoritm för ett biogasbaserat polygenereringssystem som genererar el och renar vatten till dricksvatten för en by utan elförsörjning i El Pando, Bolivia. Det konstaterades att det föreslagna systemet kan leda till betydande kostnads- och utsläppsminskningar i kombination med större energiautonomi. I den tredje studien presenteras en optimeringsmodell för ett kombinerat förgasningsbaserat CCHP / värmepumpsystem (HP) för en turistanläggning i Barcelona under olika klimatscenarier. Studien avslöjar att systemdesignen bara i låg grad påverkas av framtida klimatförändringar och att CCHP / HP-systemet endast visar en måttlig ekonomisk prestanda men fortfarande en betydande potential för CO2-besparingar. De övergripande resultaten av dessa studier visar att den ekonomiska genomförbarheten för SBP-system inte bara beror på deras inneboende design utan också på deras lokalisering. Alla föreslagna SBP-system kan emellertid sänka emissionerna betydligt, samtidigt som de sticker ut i energieffektivitet samt anpassningsbarhet efter energitjänster och annan teknik. De presenterade studierna bidrar till vetenskapen genom att lägga till innovativa SBP-systemdesigner, föreslå nya modelleringsmetoder och efterföljande modeller inklusive SBP-systemförbättrande teknik, samt genom att undersöka effekterna av geografisk plats och klimatförändringar på systemdesignprocessenErasmus Mundus en serveis energètics sostenible

A Real-time Rolling Horizon Chance Constrained Optimization Model for Energy Hub Scheduling

With the increasing consumption of energy, it is of high significance to improve energy efficiency and realize optimal operation of the multi-energy system. Among the many energy system modeling methods, the concept of “energy hub (EH)” is an emerging one. However, the previous EH models only included one or a few of constituting components. The construction of an energy hub model that integrates energy storage systems, photovoltaic (PV) components, a combined cooling heating and power (CCHP) system and electric vehicles (EVs) is explained in this thesis. The inclusion of the CCHP system helps to meet the energy demand and improve the mismatch of heat-to-electric ratio between the energy hub and the load. Additionally, vehicle-to-grid (V2G) technology is applied in this EH; that is, EVs are regarded not only as load demands but also as power suppliers. The energy hub optimization scheduling problem is formulated as a multi-period stochastic problem with the minimum total energy cost as the objective. Compared to 24-hour day-ahead scheduling, rolling horizon optimization is used in the EH scheduling and shows its superiority. In real-time rolling horizon scheduling, the optimization principle ensured that the result is optimized each moment, so it avoids energy waste caused by overbuying energy. As part of electricity loads, EVs have certain influence on energy hub scheduling. However, due to the randomness of the driving patterns, it is still very difficult to perfectly predict the driving consumption and the charging availability of the EVs one day in advance. Chance constrained programming can hedge the risk of uncertainty for a big probability and drop the extreme case with a very low probability. By restricting the probability of chance constraints over a specific level, the influence of the uncertainty of electric vehicle charging behavior on energy hub scheduling can be reduced. Simulation results show that the energy hub optimization scheduling with chance constrained programming results in a less energy cost and it can make better use of time-varying PV energy as well as the peak-to-valley electricity price

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