The floodplain areas along the Naryn River in Kyrgyzstan are essential as they hold the riparian (local) ecosystems because they provide firewood, pastureland, and areas for recreation and protection against erosion. Due to limited access to adequate, reliable, and sustainable energy services, the rural population usually derived their energy needs from multiple natural energy resources (i.e., firewood, charcoal, agricultural residues, animal dung, and wood branches). This is considered a common and predominant practice in rural Kyrgyzstan. This situation leads to a negative impact on local ecosystem services. In addition to that, the reliance on solid fuels contributes to indoor and outdoor air pollution, which is partially threatening the local ecosystem services. By contrast, the employment of renewable-based energy supply systems would substantially reduce the burden on the environment, which is mainly untapped. To integrate renewable energies, it is important to understand the energy behavior of floodplain communities. In that response, the presented article is the first attempt to capture the energy identity of the floodplain community of Kyrgyzstan based on a quantitative energy-based (on-site) household survey. Furthermore, the present research article synthesizes the driving factors that have a (direct or indirect) impact on the energy and local ecosystem services. In addition, the present article proposes a brief pathway for the sustainable energy transition. The article records the recommendation to integrate renewable energies to preserve the local ecosystems of Kyrgyzstan.
Im Rahmen des Projekts „Ökologische und ökonomische Optimierung von bestehenden und zukünftigen Biogasanlagen“ wurden je 10 typische Biogasanlagen in Bayern und Nordrhein-Westfalen hinsichtlich Effizienz und Betriebsweise intensiv untersucht. Ziel des vom Bundesministerium für Umwelt, Naturschutz und Reaktorsicherheit geförderten Vorhabens war es, konkrete, auf den Ergebnissen der Anlagenuntersuchung basierende, technische, in die Praxis umsetzbare Lösungsansätze zu erarbeiten und diese verständlich für Planer, Hersteller und Anlagenbetreiber darzustellen. Die im Projekt entstandenen Konzepte zielen darauf ab, einerseits die Wirtschaftlichkeit von bestehenden und zukünftigen Biogasanlagen zu erhöhen und andererseits die Treibhausgasemissionen zu minimieren und damit die Ökologie von Biogasanlagen zu verbessern. Die Kurzfassung der Ergebnisse wurde bereits in der „Handreichung zur Optimierung von Biogasanlagen“ veröffentlicht. Im vorliegenden Bericht wird zunächst die Vorgehensweise bei der Datenerhebung und -auswertung dargelegt. Dabei werden die durchgeführten Messungen (z.B. Eigenenergieverbrauch, Biogasleckstellen) detailliert beschrieben und es wird auf die herangezogenen Kennzahlen zur Bewertung von Effizienz, Wirtschaftlichkeit und Klimagasbilanz eingegangen. Anschließend werden die 20 untersuchten Biogasanlagen hinsichtlich ihrer Betriebsweise und Effizienz beschrieben. Dabei werden allgemeine Kenndaten, der Substrateinsatz, die Funktionsweise, die Strom- und Wärmenutzung und die Steuerung bzw. messtechnische Ausrüstung der jeweiligen Biogasanlagen betrachtet. Anhand der im Rahmen der Anlagenuntersuchung erfassten Daten findet eine Bewertung des Ist-Stands statt, die in eine Schwachstellenanalyse mündet. Zur Identifikation von Defiziten und Problemen werden die jeweiligen Bewertungsbereiche gemäß des Prozessablaufs gegliedert und die 20 untersuchten Biogasanlagen gegenüber gestellt. Nach der Identifikation von Schwachstellen werden diese anhand eines Bewertungssystems auf deren Potenzial hinsichtlich Ökonomie, Ökologie und Umsetzung eingestuft und schließlich 10 Konzepte zur ökologischen und ökonomischen Optimierung von Biogasanlagen ausgearbeitet. Die 10 bedeutsamsten Verbesserungskonzepte sind:
• Verkürzen der Transportwege zwischen Substratlager und Feststoffeinbringung,
• Auswahl des optimalen Entfeuchtungsverfahrens,
• Erhöhen der Substratausnutzung durch den Einsatz hocheffizienter Blockheizkraftwerke,
• Erhöhen der Substratausnutzung durch Vermeiden von Biogasleckstellen,
• Emissionsminderung und Erhöhen der Substratausnutzung durch Abdecken des Endlagers,
• Verringern des Eigenenergieverbrauchs bei der Entschwefelung per Lufteinblasung,
• Verringern des Eigenenergieverbrauchs bei der Feststoffeinbringung,
• Erhöhen der Wärmenutzung durch strukturierte Vorgehensweise bei der Planung,
• Erhöhen der Wärmenutzung durch Nachrüsten von Wärmemengenzählern,
• Erhöhen des Auslastungsgrads des Blockheizkraftwerks.
Die Hersteller von Solarwärmeanlagen bemühen sich stetig um die Senkung der Herstellkosten, vor allem des Solarkollektors, des weithin sichtbaren „Herzstücks“ jeder Solarwärmeanlage. Massiv steigende Weltmarktpreise für die hauptsächlich eingesetzten Werkstoffe Aluminium und Kupfer laufen den Bemühungen nach weiteren Kostensenkungen in der Kollektorfertigung aber leider entgegen. Der Einsatz von alternativen Werkstoffen, wie etwa Kunststoffen, für Solarkollektoren wird daher als vielversprechend angesehen. Die Verwendung von Kunststoffen im Solarkollektorbau kann dabei gleich mehrere Vorzüge bieten. Neben der Einsparung von kostspieligem Kupfer und/oder Aluminium sind mit den polymeren Materialien durch eine mögliche Gewichtsreduzierung gleichzeitig auch Vorteile bei der Montage verbunden. Durch Nutzung moderner Fertigungstechnologien von Kunststoffformteilen kann zudem die Kollektorfertigung automatisiert und damit die Kosten weiter gesenkt werden. Allerdings sind mit dem Einsatz von Kunststoffen bei den thermisch oft hoch belasteten Solarkollektoren auch technologische Herausforderungen verbunden. So stellen beispielsweise die begrenzte Temperatur-, Druck-, UV- und Langzeitbeständigkeit sowie die gegenüber Kupfer schlechtere Wärmeleitfähigkeit kostengünstiger Kunststoffe hohe Hürden für deren Einsatz in Solarkollektoren dar. Im Rahmen des Forschungsvorhabens wurden zunächst die auftretenden Temperaturlasten an den Kollektorbauteilen im Feldtest im Detail erfasst und in Jahreshistogrammen analysiert. Dabei erreicht der im System eingebundene Absorber Temperaturen von bis zu 192°C. Ein dauerhaft stagnierender Referenzabsorber erreicht 208°C und verweilt über 1.100 Stunden im Jahr auf einem Temperaturniveau von mehr als 95°C. Dies verdeutlicht die Notwendigkeit einer Reduktion oder im besten Fall einer aktiven Kontrolle der auftretenden Temperaturbelastungen an einigen Bauteilen, wie etwa dem Absorber. Desweiteren wird aber auch deutlich, dass für sämtliche Gehäusebauteile die Temperaturbelastung nicht die zentrale Hürde für den Kunststoffeinsatz darstellt. Zusammenfassend zeigt sich in den Messungen, dass im Hinblick auf Werkstoffspezifikationen eine sehr diversifizierte Betrachtung der Temperaturverläufe auf Bauteilebene erforderlich ist, anstelle der Angabe einer einheitlichen Maximaltemperatur für den gesamten Kollektor. Anschließend wurden sowohl verfügbare als auch potenzielle Überhitzungsschutzmaßnahmen für solarthermische Kollektoren erfasst und hinsichtlich ihrer Wirkmechanismen systematisiert. Ausgewählte Maßnahmen wurden in einer Simulation unter Nutzung eines speziell entwickelten, dynamischen Kollektormodells auf ihr Einsatzpotenzial hin untersucht. Es zeigt sich. dass eine nennenswerte Reduktion der thermischen Belastung an den Kollektorbauteilen u.a. ohne Einbuße des Anlagenertrages mit verschiedenen Maßnahmen prinzipiell durchaus erreichbar ist und vor allem perspektivisch erreicht werden kann. Das bedeutet, es werden Lösungswege aufgezeigt um den Einsatz neuer Werkstoffe wie etwa kostengünstiger Massenkunststoffe sogar am Absorber, also dem aus Sicht der Temperaturbelastung kritischsten Bauteil, realisieren zu können. Die dargestellten Simulationsergebnisse zeigen darüber hinaus einerseits die Zielparameter für die zweifelsfrei noch erforderliche Entwicklung, andererseits aber auch das Anwendungspotenzial einzelner Lösungen wie etwa den thermochromen Schichten auf, das in der Zukunft in jedem Fall zu heben ist. Auf Basis dieser Ergebnisse wurden Konzepte für Kunststoffkollektoren unter Nutzung adäquater Fertigungsverfahren entwickelt, um die Umsetzungs- und Gestaltungsmöglichkeiten aufzuzeigen. Abschließend wurden diese Konzepte hinsichtlich der Herstellkosten mit Standard-Flachkollektoren verglichen, wobei Kunststoffkollektoren neben den Vorteilen bei der Montage und Installation ein Kostensenkungspotenzial von bis zu 50% Prozent aufweisen können.
The CENTRE OF EXCELLENCE FOR SOLAR ENGINEERING of Ingolstadt University of Applied Sciences investigates the renewable-only based HVAC system of a multipurpose building. The 10.000 m² gross floor area building is part of the biggest logistic-centre in the region serving the AUDI automobile production facilities. On the one hand, the investigation is supposed to demonstrate the potential of solar-assisted cooling, on the other hand, the monitoring focuses on the total energy balance of the building and the various innovative building technologies. Next to a ground source heat pump plant for base-load heating and cooling, the building is equipped with two arrays of solar-thermal flat-plate collectors (108 m² + 178 m²) and a desiccant air-conditioning system (DEC). This consists of two plants with a nominal air flow of 8.000 m³/h each. One of the two plants is monitored, where the plant itself is considered a black box in a first approach, i.e. all incoming and outgoing energy flows and the air condition are measured. Apart from the investigation of the performance of the solar-assisted air-conditioning system, the feasibility of DECoperation using flat-plate collectors available on the market is investigated. During the first year of operation (2006) massive problems occurred in the operation of the DEC-plant. While the degree of comfort in the building was found to be satisfying during the cooling period, the solar-driven DEC-plant showed major deficiencies in cooling performance, hydraulics and control. Especially, a too high rotational speed of the desiccant wheel and an inadequate adjustment of solar collector arrays, DEC-plants and building structure were identified. Therefore, in an overhaul of the system several problems in the hardware were found and corrected such as blocked nozzles due to calcinations, leakages in the sealing of the desiccant wheel and an incorrect installation of a non-return valve in the hydraulic system of the regeneration air heater. Moreover, the control strategy regarding the cooling power of the plant and the speed of the desiccant wheel was checked. In the second year of operation (2007), some deficiencies of the first year were found to be removed, but the plant still did not work according to its capacity. Insufficient dehumidification by the desiccant wheel was identified as a major problem. Based on a detailed analysis of the desiccant wheel, one-sided displacement of the sorbent was supposed to be the reason for insufficient cooling capacity. Obviously, control or mechanical malfunctions during operation have lead to a one-sided oversaturation and thus to a one-sided damage of the desiccant wheel. Consequently, the damaged wheel is to be removed prior to the 2008 cooling period. In order to tap the full potential of both the solar DEC-plant and the building’s innovative concept, a number of further measures, especially concerning the matching of the DECplant and the solar system with the building management, need to be taken in future.
Mit der Verabschiedung des Erneuerbare Energien-Gesetzes (EEG) im Jahr 2000 und den Novellierungen in den Jahren 2004 und 2009 wurde die Voraussetzung für den wirtschaftlichen Betrieb von Biogasanlagen geschaffen.
Jedoch erfüllen nicht alle Biogasanlagen die Erwartungen einer nachhaltigen und klimaschonenden Energieerzeugung. Übereilt durchgeführte und damit unvollständige Planung und qualitativ fragwürdige Ausführung stellen die Hauptprobleme bei Biogasanlagen dar. Die Auswirkungen finden sich sowohl im ökonomischen als auch im ökologischen Bereich (Sonnleitner und Zörner 2008).
Im Rahmen des Projekts „Ökologische und ökonomische Optimierung von bestehenden und zukünftigen Biogasanlagen“ wurden je 10 typische Biogasanlagen in Bayern (BY) und Nordrhein-Westfalen (MS) intensiv untersucht.
In dieser Handreichung werden 10 konkrete, auf den Ergebnissen der Anlagenuntersuchungen basierende, technische, in die Praxis umsetzbare Lösungsansätze detailliert und verständlich für Planer, Hersteller und Anlagenbetreiber dargestellt. Die Konzepte zielen darauf ab, einerseits die Wirtschaftlichkeit von bestehenden und zukünftigen Biogasanlagen zu erhöhen und andererseits die Treibhausgasemissionen zu minimieren und damit die Ökologie von Biogasanlagen zu verbessern.
Messtechnische Analyse der Grundwasserwärmepumpenanlage in einem Büro- und Produktionsgebäude
(2011)
In einer messtechnischen Untersuchung wurde vom KOMPETENZFELD ERNEUERBARE ENERGIEN die Leistungsfähigkeit eines grundwassergespeisten Heiz- und Kühlsystems mit Wärmepumpen in einem Büro- und Produktionsgebäude analysiert und bewertet. Dazu wurde eine umfängliche energetische Bilanzierung von Gebäudetechnik und Gebäude vorgenommen. Innerhalb des mehrjährigen Untersuchungszeitraumes konnten umfangreiche Erkenntnisse über die Effizienz und Arbeitsweise der Heiz- und Kühlanlage gewonnen werden. Dabei wurden eine Reihe von Problemstellungen im realen Anlagenbetrieb identifiziert sowie das Gesamtsystem auf Basis der Messergebnisse optimiert. Um die praxisrelevanten Forschungsergebnisse in zukünftigen innovativen Gebäudetechnikkonzepten einfließen zu lassen wurden konkrete Handlungsempfehlungen für die Planungs-, die Inbetriebnahme- und Einregulierungsphase sowie für die Betriebsführung abgeleitet.
Die im Laufe des vorliegenden Vorhabens zusammengetragenen Informationen zeigen, dass der Blech-Rohr-Absorber als der momentane Stand der Technik verschiedenste Schwächen im technischen als auch wirtschaftlichen Bereich aufweist. Im technischen Bereich liegen diese sowohl im konstruktiven Aufbau aufgrund seiner vielen thermischen Widerstände, als auch in der momentanen Lösung der Verbindungstechnik. Die im Rahmen des Projekts durchgeführte Altkollektoranalyse zeigt, dass bereits früher verschiedenste Absorberbauformen auf dem Markt verfügbar waren. Diese Bauformen sind in der Fachliteratur teilweise dargestellt, jedoch kaum beschrieben oder näher untersucht. Die Analyse der großteils mehr als 20 Jahre alten Kollektoren ergibt, dass Bauformen und Absorbermaterialien bereits damals eine hohe Lebensdauer erreichen konnten. Defizite können nur bezüglich transparenten Abdeckungen, Zwischenschichten, Wärmedämmungen und bezüglich des hohen Absorber- bzw. Kollektorgewichtes ausgemacht werden. Thermographische Untersuchungen belegen, dass damalige volumetrische beziehungsweise teilvolumetrische Bauformen im Vergleich zu heutigen Konstruktionen gleichmäßigere Temperaturverteilungen aufweisen. Die Verbindungstechniken, speziell im Bereich der Blech-Rohr-Absorber, haben sich allerdings in Qualität und Stabilität im Vergleich zu damals verbessert. Hohe Stillstandstemperaturen aufgrund neuer Entwicklungen im Bereich Absorberbeschichtungen und optimierter Glas- und Dämmstoffe bringen jedoch auch die verbesserten Verbindungstechniken zwischen Blech und Rohr an ihre Grenzen. Schliffbilduntersuchungen, durchgeführt an verschiedenen heute im Absorberbau angewendeten Fertigungsverfahren, lassen fertigungs- als auch wärmetechnische Schwächen, wie z. B. inhomogene beziehungsweise spröde Nähte oder kleine Flächen für die Wärmeübertragung, erkennen. In der Konzeptphase werden nach Ausarbeitung einer Anforderungsliste und Untersuchung des Absorbers durch eine Funktionsanalyse verschiedene Lösungsprinzipien erarbeitet. Aus diesen erfolgt die Entwicklung von Absorberkonzepten in Form von Skizzen, die schwerpunktmäßig auf eine volumetrische Durchströmung des Absorbers abzielen. Im nächsten Schritt werden für die aussichtsreichsten Konzepte eingehende Untersuchungen aus technischer und wirtschaftlicher Sicht durchgeführt. Eine Berechnung hinsichtlich technischer Eigenschaften, wie Gewicht, Füllvolumen, Wärmekapazität und vor allem des Absorberwirkungsgradfaktors wird unter anderem durchgeführt. Weiterhin wird eine Voranalyse der Absorberkosten hinsichtlich Material- sowie Fertigungskosten erstellt. Basierend auf diesen Informationen können die Absorberkonzepte abschließend in einer Bewertungsmatrix bewertet werden. Es erfolgt dazu die Festlegung mehrerer differenzierbarer Bewertungskriterien, anhand dessen eine objektive und grundlegende Unterscheidung sowie Klassifizierung der Absorberkonzepte sowohl in technischer als auch wirtschaftlicher Sicht möglich ist. Diese Konzepte sind Ausgangsbasis für ein weiteres, folgendes Projekt, das zuerst auf eine grundlegende Ausarbeitung dieser Konzepte abzielt. Diese werden im nächsten Schritt mit Hilfe einer Simulationssoftware detailliert untersucht und hinsichtlich Wärmeübertragungseigenschaften sowie Druckverlust optimiert. Nach einer erneuten Bewertung ist eine Fertigung der favorisierten Konzepte in Form von Prototypen für praktische Vermessungen und Optimierungen in einem Sonnensimulator vorgesehen sowie die Implementierung in ein neu zu entwickelndes Kollektorgehäuse. Das vorliegende Vorhaben wurde von der Firma Thermo|Solar AG in Zusammenarbeit mit dem KOMPETENZZENTRUM SOLARTECHNIK an der Fachhochschule Ingolstadt durchgeführt. Die Förderung des Vorhabens erfolgte durch die Deutsche Bundesstiftung Umwelt unter dem Aktenzeichen 21543.
Planung, Errichtung, Betrieb und Optimierung einer solarunterstützten Gebäudeheizung in einem Altbau
(2005)
Vor dem Hintergrund der weiteren Verbreitung solarunterstützter Heizungsanlagen auch im Gebäudebestand und der damit oftmals verbundenen Frage nach dem „richtigen“ Kollektortyp initiierte das KOMPETENZZENTRUM SOLARTECHNIK der Fachhochschule Ingolstadt ein Demonstrationsvorhaben zur experimentellen Untersuchung einer entsprechenden Anlage. So wurde ein solarunterstütztes Gebäudeheizungssystem in einem für den süddeutschen Gebäudebestand repräsentativen Zweifamilienhaus realisiert und mit umfangreicher Messtechnik ausgestattet. Die Heizungsanlage besteht aus einem Schichtspeicher (800 l), einem Flachkollektorfeld (Bruttofläche: 6,42 m²) und einem Feld direktdurchströmter Vakuumröhrenkollektoren (15,6 m²). Als zusätzlicher Wärmeerzeuger ist ein Ölkessel (22 kW) vorhanden. Messtechnisch erfasst werden alle Wärmeerzeuger und -verbraucher sowie die Wetterbedingungen. Es zeigt sich in diesem Projekt, dass der Einsatz von solarer Heizungsunterstützung auch in bestehenden Gebäuden durchaus Sinn macht und nennenswerte Brennstoff- und damit CO2-Einsparungen erreicht werden können, falls bestimmte Voraussetzungen erfüllt sind. Als sehr vorteilhaft am beschriebenen Gebäude muss dabei gewertet werden, dass der Heizwärmebedarf in weiten Teilen über Fußbodenheizsysteme mit niedriger Vorlauftemperatur abgedeckt wird. So ist die Einbindung der Solarsysteme in eine bestehende Heizungsanlage unter Weiterverwendung vorhandener Komponenten möglich und besonders sinnvoll. Es zeigte sich im Projektverlauf jedoch, dass die hydraulische und regelungstechnische Realisierung solcher verhältnismäßig komplexer Anlagen äußerste Sorgfalt erfordert. Hinsichtlich der Tauglichkeit der beiden Kollektortypen für solare Heizungsunterstützung bleibt festzuhalten, dass sowohl der eingesetzte Vakuumröhrenkollektor als auch der Flachkollektor prinzipiell dafür als sehr geeignet erscheinen. Dabei blieb der Vakuumröhrenkollektor jedoch hinter dem erwarteten Mehrertrag gegenüber dem Flachkollektor deutlich zurück. So offenbarte der Vakuumröhrenkollektor gerade im realen Winterbetrieb, der eigentlich eine Stärke dieses Kollektortyps darstellen sollte, konzeptionelle Schwächen. Nicht zuletzt angesichts der Tatsache, dass der Vakuumröhrenkollektor selbst bei relativ niedrigen Außentemperaturen keinen beträchtlichen Mehrertrag erbrachte, erscheint damit der Flachkollektor für solare Heizungsunterstützung auch in der Übergangszeit als technisch wie wirtschaftlich äußerst interessante Alternative.
The northern part of the globe is dominated by industrialisation and is well-developed. For many years, the southern part of the world (South Asia, Africa etc.) has been a target of research concentrating on access to energy (mainly electricity) in rural regions. However, the Central Asian region has not been a focus of energy research compared to South East Asia and Africa. Despite plentiful domestically available energy resources, the energy supply in Central Asia is very unevenly distributed between urban and rural areas. Almost half of the total population of Central Asia lives in rural areas and there is a lack of access to modern energy services to meet primary needs. To analyse the energy situation (i.e., electricity, heating, hot water consumption, cooking, etc.) in rural Central Asia, this paper reviews residential energy consumption trends in rural Central Asian regions as compared to urban areas. Furthermore, the paper illustrates the potential of renewable energies in Central Asia. To perform the study, a qualitative comparative analysis was conducted based on a literature review, data, and statistical information. In summary, the presented article discusses the rural energy situation analytically and provides in-depth insights of Central Asian energy infrastructure.
In both rural and urban areas, two-wheeler vehicles are the most common means of transportation, contributing to local air pollution and greenhouse gas emissions (GHG). Transitioning to electric two-wheeler vehicles can help reduce GHG emissions while also increasing the socioeconomic status of people in rural Kenya. Renewable energy systems can play a significant role in charging electric two-wheeled vehicles, resulting in lower carbon emissions and increased renewable energy penetration in rural Kenya. As a result, using the Conventional and Renewable Energy Optimization (CARNOT) Toolbox in the MATLAB/Simulink environment, this paper focuses on integrating and modeling electric two-wheeled vehicles (e-bikes) into an off-grid photovoltaic Water-Energy Hub located in the Lake Victoria Region of Western Kenya. Electricity demand data obtained from the Water-Energy Hub was investigated and analyzed. Potential solar energy surplus was identified and the surplus was used to incorporate the electric two-wheeler vehicles. The energy consumption of the electric two-wheeler vehicles was also measured in the field based on the rider’s driving behavior. The modeling results revealed an annual power consumption of 27,267 kWh, a photovoltaic (PV) electricity production of 37,785 kWh, and an electricity deficit of 370 kWh. The annual results show that PV generation exceeds power consumption, implying that there should be no electricity deficit. The results, however, do not represent the results in hourly resolution, ignoring the impact of weather fluctuation on PV production. As a result, in order to comprehend the electricity deficit, hourly resolution results are shown. A load optimization method was designed to efficiently integrate the electric 2-wheeler vehicle into the Water-Energy Hub in order to alleviate the electricity deficit. The yearly electricity deficit was decreased to 1 kWh and the annual electricity consumption was raised by 11% (i.e., 30,767 kWh), which is enough to charge four more electric two-wheeler batteries daily using the load optimization technique.
A Dynamic Multinode Model for Component-Oriented Thermal Analysis of Flat-Plate Solar Collectors
(2015)
A mathematical model of a flat-plate solar collector was developed on the basis of the physical principles of optics and heat transfer in order to determine collector’s component temperatures as well as collector efficiency. In contrast to many available models, the targeted use of this dynamic model is the detailed, theoretical investigation of the thermal behaviour of newly developed or adjusted collector designs on component level, for example, absorber, casing, or transparent cover. The defined model is based on a multinode network (absorber, fluid, glazing, and backside insulation) containing the relevant physical equations to transfer the energy. The heat transfer network covers heat conduction, convection, and radiation. Furthermore, the collector optics is defined for the plane glazing and the absorber surface and also considers interactions between them. The model enables the variation of physical properties considering the geometric parameters and materials. Finally, the model was validated using measurement data and existing efficiency curve models. Both comparisons proved high accuracy of the developed model with deviation of up to 3% in collector efficiency and 1 K in component temperatures.
More than half of the urban population of Sub-Saharan Africa lives in informal housing conditions. While urban areas are, in general, characterized by a high electrification rate, residents of informal settlements are still affected by energy poverty, the use of traditional energy sources and unreliable electricity supply. The aim of the study is to give an overview of different renewable-energybased solutions which are able to improve local energy provision. These are Solar Home Systems, Mini-Grids, and Energy-Hubs. The technologies are compared to another option for improving energy supply, namely Grid Expansion. The analysis is based on 24 Key Performance Indicators, which can be classified into technical, economic, environmental, social, and political dimensions. The selection of indicators is based on the challenges prevalent in informal settlements that impede a comprehensive, sustainable energy supply. The literature-based indices are used to determine which of the four technologies is a suitable solution for minimizing the challenges prevailing in informal settlements. The resulting matrix provides a holistic comparison and serves as a decision aid in selecting the appropriate technology for future projects in informal settlements, depending on local conditions and the needs of the population. The results show that the Energy-Hub is a valid alternative for energy supply improvement in Informal Settlements.
This paper proposes a home energy management system able to achieve optimized load scheduling for the operation of appliances within a given household. The system, based on the genetic algorithm, provides recommendations for the user to improve the way the energy needs of the home are handled. These recommendations not only take into account the dynamic pricing of electricity, but also the optimization for solar energy usage as well as user comfort. Historical data regarding the times at which the appliances have been used is leveraged through a statistical method to integrate the user’s preference into the algorithm. Based on real life appliance consumption data collected from a household in Morocco, three scenarios are established to assess the performance of the proposed system with each scenario having different parameters. Running the scenarios on the developed MATLAB script shows a cost saving of up to 63.48% as compared to a base scenario for a specific day. These results demonstrate that significant cost saving can be achieved while maintaining user comfort. The addition of supplementary shiftable loads (i.e., an electric vehicle) to the household as well as the limitations of such home energy management systems are discussed. The main contribution of this paper is the real data and including the user comfort as a metric in in the home energy management scheme.
A dynamic flat-plate collector model for parametric sensitivity studies on polymer-based collector designs was developed. Validation using experimental results of conventional flat-plate collectors showed satisfying results especially regarding the calculation of individual part temperatures of a collector. The model was used to predict system efficiency as well as individual part temperatures in order to analyse a polymeric collector approach in comparison to a conventional collector. The simulation results showed that the fractional energy savings of systems with conventional flat-plate collectors cannot be reached with the analysed polymeric collector approach. Also the stagnation temperatures of more efficient approaches are too high for low-cost polymeric materials. The exemplary analysis of annual temperature loads of the backside insulation for different approaches proved the necessity of careful collector design aiming at temperature reduction for all individual collector parts.
AbstractBuildings in rural Central Asia have unique characteristics as they were built during the Soviet era (during 1950–1960) without any energy efficiency measures. The special and aged building stock pose a crucial challenge on energy security and energy supply. However, accurate scientific data on their energy usage is lacking, highlighting a research gap about robust and validated methodology to determine the energy use of rural Central Asian buildings. In response to this need, this research paper proposes a set of generalised residential building typologies for rural Central Asia, with a focus on Kyrgyzstan. The study combines quantitative and qualitative methods, including household surveys, energy demand modelling, EnergyPlus simulations, and result validation. It derives energy-based building typologies from construction year and building envelope characteristics. Through numerous validated simulations, it was identified that the heat demand for rural Kyrgyz houses is 3–5 times here compared to European houses (250–400 kWh/m2). The study revealed the estimated heat demand for homes in rural Kyrgyzstan, indicating a significant potential for improving building energy efficiency in the region. These results can inform specific approaches, such as building renovation plans, energy certification, and renovation strategies. Furthermore, the validated methodology introduced offers opportunities for researchers in the field of building energy efficiency and can be applied to similar regions in Central Asia with comparable building stocks and climates.
Experimental, analytical, or numerical investigations are ordinarily conducted to reveal optimisation potential for solar thermal collectors. At the same time, the ‘Solar Keymark Database’ contains more than 2,000 test reports from certified laboratories featuring properties including thermal efficiency, dimensions, or optical properties. This dataset offers untapped potential for statistical analyses as an alternative optimisation approach. Hence, this paper aims to provide a) the first statistical findings of solar thermal collector properties listed in the Solar Keymark Database and b) insights into statistical relations between these properties. The key correlations observed from the analysis of flat-plate collectors were between efficiency and both gross height (R = 0.30) and gross area (R = 0.27). We concluded that preferable collector designs may be featured with larger area to height ratios. The analyses of evacuated tube collectors revealed a strong correlation between efficiency and transversal incidence angle modifier (R = -0.65) as a result from different tube spacing. It was noticeable that the quasi-dynamic test method reported significantly higher efficiencies (7.14 percentage points) for evacuated tube collectors, which should be carefully considered for future test procedures. Overall, the statistical analysis was in accordance with conventional bottom-up analyses and revealed insightful dependencies for the present collector data.
Insulating glass flat-plate collectors can save cost by being produced quickly and automatically in insulated glass production facilities, and they can be filled with argon to reduce heat loss. During its lifetime, the collector is likely to lose argon because of gradual material degradation of the sealing. However, information on the influence of the argon concentration on the collector efficiency is limited. Therefore, the objective of this research work was to analyse this effect. A theoretical material property calculation of argon-air mixtures was carried out to determine the convective losses with variable argon concentrations. Thermal collector performance was measured experimentally using an outdoor solar tracker test rig. The results strongly suggest, that the influence of argon concentration on both the convective losses and the thermal efficiency is non-linear. The measurements revealed that an argon concentration of 90 % can increase average thermal performance by 6.7 ± 4.8 percentage points. An increase in argon concentration from 0 % to 50 % has almost twice the effect on average thermal efficiency as an increase from 50 % to 90 %. Concluding from these results, an argon leakage threshold of 2.5 percentage points per year is proposed to avoid disproportionate loss of efficiency over time.
This paper introduces a comprehensive approach for sizing grid-connected hybrid renewable energy systems tailored for electric bus fleet operations. The study involves two main steps. First, a mathematical model that optimizes the configuration of such systems by considering daily electric bus consumption, solar irradiance, wind speed, and biomass potential is formulated. The model utilizes Pareto frontier multi-objective optimization to minimize the net present cost, the cost of energy, and greenhouse gas emissions. Second, the model is rigorously applied and tested in a real-world case study in Fez, Morocco, using HOMER Pro; the case study centers on the daily energy requirements of the buses, estimated at 2.5 megawatt hours per day, with a peak demand of 345 kilowatts. Two scenarios are explored, revealing a discernible trade-off dilemma between the full hybrid renewable energy scenario (Scenario 1) and the grid-connected hybrid renewable energy scenario (Scenario 2). In Scenario 2, the grid-connected hybrid renewable energy system demonstrates a notable 42.8% reduction in the net present cost, totaling USD 984,624. Similarly, the levelized cost of energy experiences a significant decrease, reaching approximately 0.08 USD/kWh, marking a 38.1% reduction. However, this apparent economic advantage is juxtaposed with a critical consideration—an increase in greenhouse gas emissions from null to 330,418 kg/year.
The research project ‘Solar Heat in the Liquid Food Industry’ (part of the FORETA Research Network) focused on the development and optimisation of low-temperature heating systems for the liquid food industry. Its main objectives are in energy efficiency, waste heat recovery and the feasibility of a solar-thermal process heating system. Based on the particular simulation results the overall solar-thermal potentials for German breweries and dairies were determined. In this connection a literature review indicated that most of the potential studies on solar-thermal energy use in the industry or related to specific industrial sectors are based on the total use of low-temperature heat. In opposition to these results, the available and mainly limited roof area was found to be a more important aspect for the solar-thermal potential. Hence, the development of a methodology for a site- specific analysis was necessary. The interconnection of only a few defined evaluation criteria resulted in a more realistic estimation of the potential for a solar-thermal heat supply.
PV-Optimized Heat Pump Control in Multi-Family Buildings Using a Reinforcement Learning Approach
(2024)
For the energy transition in the residential sector, heat pumps are a core technology for decarbonizing thermal energy production for space heating and domestic hot water. Electricity generation from on-site photovoltaic (PV) systems can also contribute to a carbon-neutral building stock. However, both will increase the stress on the electricity grid. This can be reduced by using appropriate control strategies to match electricity consumption and production. In recent years, artificial intelligence-based approaches such as reinforcement learning (RL) have become increasingly popular for energy-system management. However, the literature shows a lack of investigation of RL-based controllers for multi-family building energy systems, including an air source heat pump, thermal storage, and a PV system, although this is a common system configuration. Therefore, in this study, a model of such an energy system and RL-based controllers were developed and simulated with physical models and compared with conventional rule-based approaches. Four RL algorithms were investigated for two objectives, and finally, the soft actor–critic algorithm was selected for the annual simulations. The first objective, to maintain only the required temperatures in the thermal storage, could be achieved by the developed RL agent. However, the second objective, to additionally improve the PV self-consumption, was better achieved by the rule-based controller. Therefore, further research on the reward function, hyperparameters, and advanced methods, including long short-term memory layers, as well as a training for longer time periods than six days are suggested.
Building construction in rural Kyrgyzstan is heavily dominated by earthen buildings. Old and inappropriate residential building structures contribute significantly to high domestic space heating energy consumption. Therefore, it is necessary to understand the relevant building construction techniques. However, the scant information on Kyrgyz building techniques, especially for high-altitude rural settlements, was the prime motivation to perform the presented study. The key objective of the study is to investigate residential building construction techniques in high-altitude rural Kyrgyzstan, and this was to be achieved by house visits during field trips, literature review, and pilot interviews with local people. The analysis enabled the detailed identification of individual building envelopes as well as predominant building materials to be recorded. Based on the assessment, a housing profile was created that represents the typical characteristics of traditional rural Kyrgyz houses. Furthermore, the study demonstrates the potential for energy savings in rural Kyrgyz houses of 50–70%. However, local conditions prevent people from making improvements to all domestic energy efficiency parameters simultaneously. Therefore, the study developed a ‘sequential roadmap’ to reduce domestic space heating demand in different phases based on simulation studies. Existing low-income rural Kyrgyz habitations can use the presented roadmap to reduce domestic space heating demand sequentially to overcome financial barriers and, therefore, contribute to establishing sustainable buildings in Kyrgyzstan. These results may be partially replicated in other Central Asian rural communities depending on their location and building characteristics.
Energy is a pivotal element for overall development. Therefore, affordable and clean energy for all (Sustainable Development Goal 7) is one of the important elements. Despite a suitable approach, Kyrgyzstan lags behind to achieve its Sustainable Development Goals by 2030. Improving access to energy can significantly impact the progress of many other sustainable development targets. However, access to reliable, sustainable, and adequate energy is a crucial task in rural Kyrgyzstan. Taking into consideration the energy situation and the importance of the availability of energy services, the overarching aim of the presented article is to map the potential of improving rural energy services to foster overall sustainable development goals. The article presents the most relevant information about rural energy usage behaviour based on three primary pillars: energy demand, energy carrier, and energy sources. In addition, the presented research article synthesises the key driving factors which have a direct or indirect impact on the energy services in rural areas. The summarised data displays a deep insight into a variety of complex and dynamic household energy consumption patterns. The article provides a potential solution nexus to foster improved energy services in rural Kyrgyzstan and therefore to foster the overall sustainable development in Kyrgyzstan. The findings of the article help to formulate a strategy to design rural energy services for policy makers and stockholders.
How to measure flexibility
(2019)
Flexible power provision from biogas can significantly contribute to energy systems with high shares of renewables. However, the characteristics and demands for this flexibility are not clearly defined or measured. In this paper eight indicators are defined to shape “flexibility” and perform a downstream investigation of eight research projects focusing on flexible energy provision of biogas plants. The indicators are structured in three dimensions (1) velocity (ramps) by which the system can be modulated, (2) power range (bandwidth) and (3) duration for specific load conditions. Based on these indicators bottlenecks for the flexibility potential were identified. One crucial result shows that short-term flexibility of biogas plants is mainly driven by properties of the combined heat and power unit (velocity and bandwidth). The long-term flexibility depends mainly on gas storage, mode of operation and ability for modulation of the target gas production.
The potential of combining biogas and photovoltaic (PV) power plants in hybrid systems in the German distribution grid is analyzed. The focus of the present research is on balancing the intermittent power supply from PV power plants with the controllable power production of combined heat and power (CHP) units of biogas plants within a period of seconds. To achieve an increase of the total energy feed-in of biogas and PV power plants to the electricity grid, a biogas plant energy management system is described. System parameters, such as the variable feed-in of PV power plants or power ramps of the start-up process of controllable biogas plant CHP unit, are described and adapted to the global installed capacity of PV power plant and biogas plants in the German distribution grid.
This paper discusses the mechanical behaviour of an all-round fully adhesive supported absorber. Previous research is discussed and compared to the author's own results collected using both laboratory tests and simulation. The influence of the finite-element approach (i.e. geometrically linear or non-linear) was compared. The thermal deformation of a hyperstatic absorber was investigated. The relationship between thermal expansion and pressure change in a gas-filled collector is discussed.
The climate specific effectiveness of solar DEC-systems and relevant preferable adaptions of the system design have been so far predominantly analysed based on individual simulation for selected sites. In order to systematically deduce design-specific outline data for the application of the solar DEC-technology at climatically different sites a methodological zoning approach was further developed. A subsequent meteorological analysis for 17 sites mapping the world climate creates a transparent understanding on the activity of the specific system components. This results in a comprehension on the site-specific effectiveness of solar DEC-systems and provides insights on principally relevant and efficient system configurations.
Kyrgyzstan – a Central Asian country – faces a high degree of energy insecurity. Especially the Kyrgyz power sector suffers from outdated infrastructure and is not capable of fulfilling the growing and fluctuating inter-seasonal energy demand. On the contrary, the country is endowed with an abundant amount of renewable energies, which can significantly contribute to bringing stability to the energy sector. The current energy policy is considered as one of the key barriers to the developing the renewable energy sector in Kyrgyzstan. Hence, there is an immediate need to evaluate the formulated energy policy to investigate gaps and uncertainties. In response to that, the presented study is the first attempt that provides an in-depth assessment of Kyrgyzstan's current energy legislative framework. It determines the primary mechanisms for the operation and conduction of renewable energy sources in terms of legal and economic aspects. Furthermore, it provides detailed insight into the current Feed-in tariff calculation methodology and scrutinizes the special provisions for private investors. Based on the in-depth assessment, the article recapitulates the shortfall in the existing energy policies. The article found that there is huge potential available for the renewable energy market. To unlock that, the presented article emahsised on synergestic policy making approach to overcome barriers and expand the Kyrgyz renewable energy sector. The article further showcased how the improvements in the regulatory framework would raise the interest of the private investors / local energy players to promote the installation of renewable energy technologies over the county.
In rural Kyrgyzstan, the energy need is usually derived from multiple natural energy resources such as firewood, charcoal, agricultural residues, animal dung, and wood branches, which are considered common and predominant practices. Because of the non-sustainable resources and heavy reliance on the environment, Kyrgyzstan is one of the most vulnerable countries to climate change in Central Asia. On the contrary, the great renewable energy potential in Kyrgyzstan is untapped, which could be the most promising solution to ensuring sustainable energy supply in the country. However, because of the lack of scientific knowledge, current energy policies, and the lack of infrastructure, renewable resources are mainly untapped. To exploit the country’s renewable energy potential, there is a need for a systematic diagnosis to develop a strategy to explore renewables in Kyrgyzstan, which is currently missing in the existing literature. In that regard, the presented study aims to assess the current status of renewable energy sources by considering the local energy context from a potential point of view. Further to this, it provides a comparative overview through a matrix of strengths, weaknesses, opportunities, and threats. Such novel analysis would be the fundamental base for formulating policy advice and a national plan to enhance the utilization of renewable energy in Kyrgyzstan. The presented analysis was carried out based on the extensive literature review, the country’s national plan, and the existing energy policies of Kyrgyzstan. The article found out that there is huge potential available for the renewable energy market. As compared to other renewable energy sources, solar energy has great potential and can be considered one of the pioneer sustainable sources for integration into the country’s power generation framework.