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he technical feasibility and performance of photocatalytic Ti02 coatings in batch-process solar disinfection (SODIS) reactors to improve potability of drinking water in developing countries have been studied. Borosilicate glass and PET plastic SODIS reactors fitted with flexible plastic inserts coated with Ti02 powder were shown to be 2(Jt1o and 25% more effective, respectively, than standard SODIS reactors for the inactivation of E. coli K12. Isopropanol at 100 ppm concentration levels was observed to be completely photodegraded after 24 h continuous exposure to lOG mW/cm2 simulated sunlight in a similar solar photocatalytic disinfector (SPC-DIS) reactor. The technique for p roducing the TiOrcoated plastic inserts is described and demonstrated to be an appropriate and affordable technology for developing countries.

Hidden state models are among the most widely used and efficient schemes for solar irradiance modeling in general and forecasting in particular. However, the complexity of such models – in terms of the number of states – is usually needed to be specified a priori. For solar irradiance data this assumption is very difficult to justify. In this paper, an infinite hidden Markov model (InfHMM) is introduced for short-term probabilistic forecasting of solar irradiance, where the assumption of fixed number of states a priori is relaxed and model complexity is determined during the model training. InfHMM is a non-parametric Bayesian model (NPB) indexed with an infinite dimensional parameter space which allows the automatic adaptation of the model to the “correct” complexity. This facilitates the automatic adaptation of the model to all weather conditions and locations. Posterior inference for InfHMM is performed using the Markov chain Monte Carlo algorithm, namely the beam sampler. Data from 13 different sources are used to validate the proposed model and subsequently it is compared to two well-established models in the literature: Markov-chain mixture distribution (MCM) and complete-history persistence ensemble (CH-PeEn) models. Important results are found, that cannot be derived from the existing finite models, such as the variation of the number of states within and across sites. The comparison of the models shows that the InfHMM is more consistent in term of the forecasting horizon. For reproducibility of the methodology presented in this paper, we have provided an R script for the InfHMM as supplementary material.

The unpredictability of heat demand–supply is one of the major challenges in our future sustainable energy system. Thus, coming up with new methods of heat storage for operating solar systems during low solar irradiance is among the advanced technical approaches in this field. The compact integrated solar thermal collector-storage systems have recently attracted the researchers’ attention due to the direct usage of stored thermal energy as well as the reduced space occupation. The current literature lacks a review paper on investigating various existing designs of such compact PCM-solar systems; thus, this paper analyzes the latest developments on experimentally investigated single-unit PCM-based solar collectors regarding both solar water and air heaters. Various types of solar collectors, including flat plate, evacuated tube, concentrating, and photovoltaic/thermal collectors have been thoroughly reviewed and discussed and the thermodynamic correlations for the system analysis have been given. The investigations revealed that a large proportion of integrated flat plate storage systems have been designed to provide space heating and it was deduced that paraffin and other hydrocarbons were basically used for the low-temperature heat production for domestic uses. Also, the concentrating solar collectors have mostly been utilized for providing the medium temperature for the industrial usage employing salt hydrates and nano-composite based phase change materials possessing higher melting points are adopted. Last but not least, it was concluded that the exergy efficiencies of solar collectors are remarkably low (below 5%), and the hybrid photovoltaic-thermal collectors can encounter this drawback by exploiting the high electrical exergy.

As power system renewable energy penetrations increase, the ways in which key renewable technologies such as wind and solar photovoltaics (PV) differ from thermal generators become more apparent. Many studies have examined the variability and uncertainty of such generators and described how generation and load can be balanced for a wide variety of annual energy penetrations, at timescales from seconds to years. Another important characteristic of these resources is asynchronicity, the result of using inverters to interface the prime energy source with the power system as opposed to synchronous generators. Unlike synchronous generators, whose frequency of alternating current (AC) injection is physically coupled to the rotation of the machine itself, inverter based asynchronous generators do not share the same physical coupling with the generated frequency. These subtle differences impact the operations of power systems developed around the characteristics of synchronous generators. In this paper we review current knowledge and open research questions concerning the interplay between asynchronous inverter-based resources (IBRs) and cycle- to second-scale power system dynamics, with a focus on how stability and control may be impacted or need to be achieved differently when there are high instantaneous penetrations of IBRs across an interconnection. This work does not seek to provide a comprehensive review of the latest developments, but is instead intended to be accessible to any reader with an engineering background and an interest in power systems and renewable energy. As such, the paper includes basic material on power electronics, control schemes for IBRs, and power system stability; and uses this background material to describe potential impacts of IBRs on power system stability, operational challenges associated with large amounts of distributed IBR generation, and modern power system simulation trends driven by IBR characteristics.

Horizontal light pipes (HLP) have shown the potential to convey daylight deeper into buildings. The wide variation in incident angles of sunlight rays and the resulting numerous interreflections of light rays within the pipe are the main reasons for the limited light transmittance of such light pipes during certain daylight periods. This paper presents a research study on different configurations of acrylic laser-cut panels (LCP) applied at the entrance of horizontal pipes as light collectors to increase the transmittance of HLPs and improve daylight autonomy in spaces equipped with HLPs. This study required the development of a suitable methodology. The study begins with an experimental laboratory test of a HLP scale model to determine the light transmittance efficiency (standard daylight guide characteristic) of HLPs with several LCP configurations. The results from the laboratory test are combined with the statistical data for both the direct and diffuse illuminance on the vertical south-oriented surface (Satel-Light database) for the location selected for the analyses (Oslo, Norway). The analyses are discussed via the application of a theoretical model of an office space equipped with a HPL as well as through the concept of daylight autonomy (DA) in an indoor space. The paper shows that a certain static LCP configuration has the potential to increase DA100 and DA300 to 10% and 19%, respectively, at a 2.1 m distance from the facade, and 8.75% and 16%, respectively, at a 4.5 m distance. This paper also contributes to lighting science with its data on the light transmittance efficiency of each LCP configuration, which can be applicable in further research.

Building Integrated Photovoltaic Thermal (BIPV/T) systems which generate electricity and heat simultaneously are promising solutions for Net Zero Energy Buildings (NZEB). Despite BIPV/T offering clear energetic and space saving advantages compared to separate PV and solar thermal, overheating problems occur when no thermal demand exists, resulting in reduced yields, stagnation damage, and excessive fluid flow pressures. This two-part study examines an alternative approach combining BIPV, Planar Liquid-Vapour Thermal Diodes (PLVTD) and Integrated Collector-Storage Solar Water Heaters (ICSSWH) to achieve BIPV/T functionality and retain heat overnight to minimises parasitic demands and reduce overheating. The introductory paper (Part 1 of 2) established novelty and rationale for BIPV-PLVTD-ICSSWH concepts, reviewed state-of-the-art and performance benchmarks, and used theoretical modelling to predict behaviour from key design and operational parameters. This paper (Part 2 of 2) describes prototype realisation and multi-day solar simulator laboratory thermal and photovoltaic testing for covered and uncovered variants exposed to different irradiance levels. Measured solar thermal efficiencies with and without transparent covers were ηT,col = 60% and 58% respectively under zero heat loss conditions whilst overnight heat loss coefficients were Ur,sysAsys/u = 23.0 and 25.4 W·m–3 K−1 respectively, showing good agreement with theoretical predictions. Photovoltaic performance reduced with increasing absorber temperature as expected, although maximum power point efficiencies (ηE,mpp = 11.4% at T1 ≈ 25 °C and 5.6% at T1 ≈ 89 °C, without cover) were lower than expected owing to partial delamination and PV cell damage. The work demonstrates practical operation of a vertical BIPV-PLVTD-ICSSWH, identifies key areas for design development, and highlights benefits of application in NZEB facades.

Perovskite solar cells (PSCs) have been made eligible for proficient power conversion efficiency (PCE) by optimizing the perovskite film’s morphology, formation, interfaces, and charge collection for increased effectiveness. This paper applied a new method for Cu2O/methylammonium lead iodide (MAPbI3)/SiO2 structure with heterojunction PSCs. This paper developed a novel synthesis engineering method for thin Cu2O hole-transporting material layer (HTML) and ultrathin SiO2 electron-transporting material layer (ETML). Cu2O HTML and SiO2 ETML could improve the PCE and carrier charge for recombination and recollection. The architecture includes a reduced film thickness by hetero-contact synthesis engineering, which resulted in an impactful enhancement of open-circuit voltage (Voc). The stable Voc effect was induced by constructing the interfilm of Cu2O and SiO2 between the main CH3NH3PbI3 layers, which transported electrons/electron holes, resulting in an excellent PCE of 18.4%. The fabrication showed that inorganic materials can be applied for the potential interfacial engineering of perovskite-based solar cells.

To maintain the energy quality with high temperature and reduce the energy loss of seasonal heat-storage in solar-assisted ground-source heat pumps (SAGSHPs), a novel SAGSHP system with the heat-cascading of borehole heat-exchangers was designed and its field-test was conducted in this paper. The borehole heat-exchangers were divided into two regions: the core region and the peripheral region. The core region can maintain a high temperature (e.g. 45 °C), which is much higher than in previous studies, and the heat from this region can be used directly, without the operation of a heat pump. A field-test was conducted in a community in the province Shandong, China. The results indicate that a sufficient soil-temperature gradient (the temperature is high in the core but low at the periphery) can be created and maintained. The monthly averaged borehole-wall-temperature difference between the borehole heat-exchangers (BHEs) at the core and the periphery can be as high as 30.1 °C. This means that both cascaded heat-storage and heat-utilization can be realized. In addition, an average performance of CCOP = 5.15 and SCOP = 4.66 can be achieved. Compared with previous studies, despite the lower CCOP, a higher SCOP can be attained, thanks to heat cascade storage and -utilization. The novel approach described in this paper represents a viable alternative for space heating in North China.

The estimation of electrical power generation in photovoltaic (PV) grid-connected systems based on meteorological data is a nontrivial, highly useful task, for instance to achieve accurate energy assessment. Widely used PV generation simulators are PV Systems (PVsyst), System Advisor Model (SAM) and PVLib. These simulators are characterized by presenting numerous features and providing complete results, however the PV estimation model SoL is an example of a new approach to PV generation estimation. SoL is characterized by its simplicity and computational efficiency. The objective of this paper is validating the recently published SoL model using real data from two PV locations for several years and facilities and comparing the results with those of three other PV simulators, namely PVsyst (in Spain), SAM (in Denver) and PVLib (both). It has been found that SoL estimates power production accurately for both locations and its estimations are more precise than those given by PVsyst, SAM and PVLib. It proves to be more computationally efficient than PVsyst, it can work with higher resolutions than SAM and PVsyst and requires fewer inputs than PVLib, SAM or PVsyst. Finally, a self-shading model is proposed as an enhancement for the SoL model. The number of inputs required is minimal, and it is an approximate yet efficient model. The estimation when using the self-shading enhancement is even more accurate than the previous estimation for SoL in locations where self-shading is evident. SoL proves to be an appropriate model for power estimation, and its results are enhanced when using the self-shading model proposed in this paper.

Solar thermal utilization is an important part of renewable energy applications, and its development and application have received extensive attention. Based on the development status of medium and low temperature solar thermal utilization systems, this paper first introduces the application and performance research on subsystems of the solar system including heat collection, heat storage and heat utilization units. It then introduces the theoretical and experimental development of matching relationships and dynamic performance of the medium and low temperature thermal utilization systems. Lastly, a case study analysis of a solar thermal system performance was carried out under different thermal boundary conditions. The influence of the boundary conditions of the heat storage system and the actual weather conditions on its performance is explored. The results showed that the boundary conditions of constant temperature and the boundary conditions of constant heat flow density have their own advantages. The heat source conditions provided by heat transfer medium are similar to the constant heat flux boundary condition. The work of this paper provided a theoretical basis for the subsequent application and performance study of solar medium and low temperature thermal utilization systems.

The Distributed Maximum Power Point Tracking (DMPPT) architecture is employed to overcome the mismatching phenomena in grid-tied photovoltaic (PV) installations. In this kind of architecture, a DC-DC module integrated converter (MIC) manages each PV panel. Thanks to the DC-DC converters, the differences between PV panels do not influence others, maximizing the amount of harvested power. The MIC requirements to make this kind of solutions profitable are voltage step-down and step-up capability, low cost and high efficiency. This paper analyses the Autotransformer Forward-Flyback (AFF) converter. This converter is considered as a MIC candidate for fulfilling the requirements above. The study of the AFF converter includes the steady-state analysis and the small signal analysis in continuous conduction mode. The advantages of the AFF converter are the capability of voltage step-down and step-up; the simplicity since it only includes a single controlled switch; the use of an autotransformer; good dynamic performances and the soft switching characteristics in all the diodes. The paper includes a detailed AFF converter step-by-step design procedure, applied to 100 kW grid-tied PV installation, in which the effect of shadows has been considered. A 225 W AFF converter prototype validates the theoretical analyses, achieving an efficiency up to 94.5%. This work has been supported by the Ministry of Economy and Competitiveness and FEDER funds through the research project "Storage and Energy Management for Hybrid Electric Vehicles based on Fuel Cell, Battery and Supercapacitors" - ELECTRICAR-AG- (DPI2014-53685-C2-1-R)

The invention of heat pipe solar collectors (HPSCs) is considered as an immense step forward towards solving the challenges of conventional solar thermal systems. Their unique qualities have acted as a great motivation for researchers to focus their studies on HPSCs and their applications. A considerable share of these studies has been allocated to theoretical studies due to several technical and economic reasons. However, to the authors’ knowledge and despite many valuable efforts in this field, there is no review paper available to summarise the relevant proposed and developed theoretical models to date and identifies the research gaps in this field. Therefore, in this review paper, the latest theoretical studies in the field of HPSCs along with their advantages, disadvantages, and contribution have been categorized, reviewed, and discussed. First, the operational principles and structure of HPSCs have been explained to create a background for readers. This is followed by a short section dedicated to the simulation of solar radiation as the most important input for all solar mathematical models. In addition, various mathematical approaches including steady state models (i.e. one-dimensional energy balance and thermal resistance network methods), dynamic models, and models for novel configurations and applications of HPSCs have been reviewed. Moreover, mathematical models to determine the exergy efficiency of HPSCs, which is an effective tool to evaluate the solar systems from a thermodynamic point of view, have been presented. Finally, the challenges, research gaps, and recommendations for future research directions have been provided.

Transparent Insulation (TI) systems are regarded as one of the most promising technologies for providing thermal insulation along with transmission of solar energy. TI systems have a wide range of applications in energy conservation and harnessing solar energy. This paper provides an overview of TI systems and TI materials (TIM), by characterising TI systems on the basis of geometry, material used and general heat losses in these geometrical layouts. Evolution of TI applications is presented with the introduction of new materials. Two new types of TIM (polypropylene and cellulose acetate) are reported in this paper in contrast to previous reviews on TIM. A systematic survey of past literature was carried out to present latest research works and development on TI geometrical layouts and applications. An explicit study of TIM and TI system manufacturers has been carried out to show existing trends in TI applications and geometry. In the last decade, aerogels are most frequently used as TIM for providing insulation and daylighting in buildings. It is concluded that in existing TIM technologies, TI systems incorporating aerogel have the lowest thermal transmittance (U-value) and better solar transmittance (g-value) at lower thickness compared with TI systems incorporating other types of TIM. This paper highlights the availability of TIM geometry with desirable applications and TI systems for energy conservation.

Building core sunlighting systems (BCSS) are developed to deliver daylight where it can not be delivered by the conventional methods. A brief history is given of researches and developments into the BCSS over the last fifty years, in addition to a short description of the technologies and components of eighteen fully developed or commercialized systems. The paper classifies and compares the BCSS according to their design approaches so as to conclude the common features of the successful systems. Eight lessons learned have been addressed. The BCSS are technically powerful enough to provide lighting for remote and windowless spaces within buildings, but a couple of significant shortcomings hinders their popularization: cost prohibitive and application limitations. In addition, components costs/performance efficiency trade-off is one of the most fundamental decisions the BCSS designer must make. Finally, the paper presents the most recent design approaches that have been developed to overcome the identified failings.

The production of silicon-calcium alloy is energy intensive (>10,000 kWh/t). This means that energy cost has a relevant influence in the price of the alloy. The utilization of concentrated solar energy in the synthesis of silicon-calcium alloy is proposed in this paper. Metallurgical quality silicon and limestone are used as starting materials (25 wt.%, 50 wt.% and 75 wt.% Si). After a 12 min treatment under power values of around 1 kW and without using special atmosphere, silicon-calcium was detected in all samples, although mixed with the products of reaction (Ca3Si2O7, Ca10O25Si6, SiO2). This last question means that there was not proper separation metal-slag, and it should be improved in future investigations. However, the basic knowledge presented in this paper could be of great interest for an industrial process based on the solar energy. This way, the energy costs could be reduced, the pollutant emissions could be minimized, and the competitiveness of the ferroalloys industry could be increased. Sin financiación 4.608 JCR (2019) Q2, 35/112 Energy & Fuels 1.537 SJR (2019) Q1, 32/297 Renewable Energy, Sustainability and the Environment, 62/626 Materials Science (miscellaneous) No data IDR 2019 UEM

This analysis investigates the design, cost, and performance of the simple, recompression, and partial-cooling configurations of the supercritical carbon dioxide power cycle integrated with a molten salt power tower concentrating solar power system. This paper uses a steady-state model to design each cycle with varying amounts of recuperator conductance to understand performance and cost trade-offs. The recompression cycle can achieve a higher thermal efficiency than the partial-cooling cycle, and the partial-cooling cycle achieves a higher thermal efficiency than the simple cycle. The partial-cooling cycle is the most expensive cycle because it requires more total turbomachinery capacity. However, the partial-cooling cycle has the largest temperature range of heat input. This feature leads to cheaper two-tank thermal energy storage, higher receiver efficiencies, and lower mass flow rates in the power tower. Crucially, the lower mass flow rates significantly reduce pump electricity consumption relative to the recompression-cycle system. Consequently, this study finds that the power tower system integrated with the partial-cooling cycle is both cheaper and generates more net electricity than systems integrated with the other two cycles. Finally, this paper presents a parametric study on the air-cooler approach temperature and shows that small approach temperatures can improve cycle efficiency and increase the temperature range of heat input, which can lead to smaller optimal approach temperatures than may be expected.

Concentrating solar power plants are taking an increasing share in the renewable energy generation market. Parabolic trough is one of such technologies and the most commercially mature. However, this technology still suffers from technical challenges that need to be addressed. As these power plants experience daily start-up procedures, the optimal performance in transient operation needs to be considered. This paper presents a performance based modelling tool for a gas-boosted parabolic trough power plant. The objective of the paper is to define an optimal operational strategy of the power plant start-up procedure with the aim of minimizing its fuel consumption while at the same time maximizing its electric energy output, taking into account all the thermo-mechanical constraints involved in the procedure. Heating rate constraints of the steam generator and the booster heater, and the steam turbine start-up schedule were considered. The simulation model was developed based on a power plant located near Abu Dhabi, and was validated against real operational data with a maximum integral relative deviation of 4.3% for gross electric energy production. A multi-objective optimization was performed for a typical operating week during winter and spring weather conditions. The results suggest that in order to minimize the fuel consumption and at the same time maximize the electric energy production, an evaporator heating rate of 6 K/min is an optimal value both for winter and spring conditions.

In this paper, a continuous adsorption chiller is designed and constructed with micro and Nano-activated carbon/methanol as working pair that works with solar energy. The chiller used in this study includes evaporator, condenser, adsorbent bed and compound parabolic collector. The collectors used in this chiller is a compound parabolic type. Unlike traditional systems that perform refrigeration only during the night, in this paper the continuous refrigeration system with two adsorbent beds can produce cold during the day. The main objective of this study is to investigate the effect of Nano-activated carbon on the refrigerator's performance for the first time. For this purpose, at first experiments are performed with only 200 g micro-activated carbon in each bed. In the next steps, Nano-activated carbon is added to the bed in mass fractions of 4.7%, 11.1% and 18.3%, and the experiments are carried out at the two temperatures (30 and 34 °C). The results showed that the addition of Nano-activated carbon with various mass fractions increases the adsorption level. As a result, the adsorption capacity increased and the COP improved. Thus, the addition of Nano-activated carbon with mass fractions of 4.7%, 11.1% and 18.3% to the adsorbent bed at 30 and 34 °C caused 11%, 21%, 33% and 17%, 23%, 25% increase in COP respectively.

This paper outlines the development of models of a solar field designed to provide thermal energy to a Multi-Effect Desalination (MED) plant. The dynamic model can be used both for simulation and control purposes. Some of these models have been developed based on static and dynamic energy and mass balances, and some others are based on step response methods (experimental tests). The solar field comprises a flat-plate collector field, an air cooler, a heat exchanger and the corresponding pipelines and interconnections. The main purpose of the solar field is to feed the MED unit with hot water within a specific temperature range using two thermal storage tanks as input buffers to the MED system. The main achievement of this paper is that the developed model provides an adequate tradeoff between complexity and performance.

Modern photovoltaics and thermal technologies are widely available for the building sector at competitive prices. However, innovative approaches must be explored and implemented to find new architectural solutions at the building scale. This paper presents an electro-thermal solar concentrator and proposals for its building integration. The proposed device has a small size and is based on a 20x semi-parabolic mirror concentrating the sunlight on a linear focus where a string of mono-crystalline PV cells is placed. A thermal receiver is placed on the back-side of the cells, a fluid circulating in the thermal receiver provides the heat recovery. The linear focus allows a monoaxial sun tracking. The proposed device has been numerically analyzed with the support of experimental data. The small size and the linear focus make feasible the integration of arrays of the proposed innovative device in roofs or facades of both new and existing buildings where they contribute to the auto-generation of a portion of the overall required energy. Several examples of the possibilities of array building integration of the described small-size solar concentrator are proposed. The device can be horizontally and/or vertically mounted to better match the architectural needs. The potential yearly power generation of a single unit three meters long , is evaluated to be as high as 120 kWhelettric/year and 500 kWhthermal/year. Horizontal mounting results in a power production about 30% higher than the vertical mounting. The significance of this paper is that small size, single axis solar tracking, suitable for building integration is presented, studies of its possible integration in the building are given, the power generation capabilities of the proposed solutions are analyzed in detail. These capabilities have been derived using data achieved by experimental tests performed on a prototype constituted by four semi-parabolic mirrors. The novel contribution is that a new research direction toward further improvement of the performance, system design and installation of a prefabricated modular facade component, is presented. Moreover, the proposed PVT low concentrated solar device is integrable into buildings, easy to install and manage. Finally, the modern and attractive architectural designs are proposed.

Many countries have adopted schemes to promote investments into renewable energy sources resulting, among others, in a high penetration of solar PV energy. The system integration of the increasing amount of variable electricity generation is therefore a highly important task. This paper focuses on a residential quarter with PV systems and explores how heat pumps and thermal and electrical storages can help to integrate the PV generation through self-consumption. However, self-consumption and PV integration are not only affected by technologies but also by pricing mechanisms. This paper therefore analyses the impact of different tariffs on the investment and operation decisions in a residential quarter and its interaction with the external grid. The considered tariffs include a standard fixed per-kilowatt-hour price, a dynamic pricing scheme and a capacity pricing scheme. To account for the interdependent uncertainties of energy supply, demand and electricity prices, we use a module-based framework including a Markov process and a two-stage stochastic mixed-integer program. Analysing a residential quarter in Southern Germany as a case study, we find that the integration of a PV system is economically advantageous for all considered tariffs. The self-consumption rate varies between 58 and 75%. The largest PV system is built when dynamic prices are applied. However, the peak load from the external grid increases by a factor of two under this tariff without any incentive for reduction. In contrast, capacity pricing results in a reduction of the peak load by up to 35%.

Fiber-optic solar hybrid lighting for mobile application such as military shelters in remote areas is appealing since high initial costs of such systems appear to be justified. This paper addresses the aspect of two-stage optics for a fiber-optic solar lighting system for the mobile application. More specifically, the focus of this paper is on the design and development of a second stage or secondary concentrator. Two-stage optics offers a distinct advantage of higher sun angle tolerance and hence a low-accuracy tracker can be used for the mobile application. The objective of this study was to design and develop a secondary concentrator that yielded a minimized peak illuminance on the fiber-optic inlet and achieved uniformity, to avoid localized heat damage to the fiber inlet. In addition, the overall goal was to increase the lumen output from the two-stage optics. Specifications for the design of the two-stage concentrator were: (1) the primary stage concentrator was a 10-in. diameter Fresnel lens; (2) solar tolerance angle or the half-angle of acceptance was ±1.75°; (3) the fiber half-acceptance angle was ±40°; and (4) the fiber optic cable diameter was 0.5-in. Raytracing was used to determine the optimum geometry for the secondary lens. Among various geometries simulated included a conical secondary, a Compound Parabolic Concentrator (CPC), and a combination of conical and Compound Elliptical Concentrator (CEC). The analysis showed that a combination design comprising conical/CEC geometry was better than the conical and CPC geometries in terms of greatest overall light output and most reduced peak illuminance on the fiber optic cable. Prototype secondary lenses based on the design were fabricated from acrylic and optical silicones. Testing of the prototype lenses revealed that acrylic secondary performed better than the silicone lenses in terms of the measured lumen output. Testing also showed that the fiber-optic cable temperature was within the maximum operating temperature of acrylic and didn’t suffer any high temperature damage during the five month long outdoor testing.

In this paper, a techno-economic analysis is performed to assess the feasibility of adding an offshore floating solar farm to an existing Dutch offshore wind farm in the North Sea, under the constraint of a certain fixed cable capacity. The specific capacity of the cable that connects the offshore park to the onshore grid is not fully used due to the limited capacity factor of the wind farm. The principle of cable pooling allows to add floating solar capacity. Using weather data it is found that adding solar capacity leads to forced curtailment due to the cable capacity, but this is quite limited as result of the anti-correlation of the solar and wind resource. For the economic analysis, different scenarios regarding subsidy measures are considered for the calculation of net present value and levelized cost of electricity. Also the optimum additional PV capacity for each scenario is computed. The results show that with higher cost per Wp, optimum PV capacity decreases, but more favourable subsidies lead to higher optimized PV capacities. As the aim of the paper is not limited to a case study a methodology is developed for generalization of the techno-economic analysis of a hybrid solar/wind park. In this generalization, the initial investment, system degradation, cable capacity, number of hours when each system is active, and energy price, are implemented to compute the optimum PV capacity regarding the net present value as an indicator for economic analysis of the project.

This paper deals with the state of the art of advanced solar control devices for buildings, with the comparative evaluation of solar-control systems and with guidelines for the development of new solar control systems. It includes multifunctional systems with building integrated photovoltaic (BIPV) and/or building integrated solar thermal (BIST) energy conversion. In order to facilitate and to structure the understanding of solar control systems two multidimensional spaces are introduced: the design space and the evaluation space. The design space contains the design parameters which are to be selected by the designer when solar control devices are to be chosen for specific buildings or when new systems are to be developed, such us the color of the slat of a venetian blind or the fraction of holes (direct transmittance) of a fabric for a roller blind. The evaluation space contains the performance parameters or evaluation criteria, which indicate the design‘s ability to satisfy the functional and aesthetic requirements, such us passive solar gain control or visual comfort. All the design parameters and evaluation criteria are explained in detail in the paper. A chapter with examples of advanced solar control systems completes the overview of the state of the art of solar control systems.

Solar building envelopes are attracting increasing interest. Building-integrated solar thermal (BIST) systems are one of the subgroups of solar building envelopes. This paper summarizes the most important contributions of recent years and extends them. First, BIST elements are defined and available BIST elements are presented. Then, the general functions which BIST systems can provide are presented and the conflict between the constant U and g values of simple planning software and the variable g and U values of BIST elements is discussed. Measurements to characterize BIST elements are presented as well as a design parameter space in which the current BIST elements are located and which can be used when developing innovative new components. Methods to evaluate and compare BIST technologies are presented. The substantial cost savings which were achieved in three building projects between 2002 and 2009 are discussed. Roles within the building process are presented, as well as the general methods and challenges for economic BIST calculations and one economic calculation as an example. Based on existing building processes, a vision for future BIST building process integration is presented. Simple BIST models, which need no programming, are provided with easy-to-use equations. The challenges of standards and regulations are outlined and future research topics are presented. This paper summarizes important recent contributions to BIST research as a basis for future progress in building-integrated solar thermal systems. Instead of aiming to cover all recent BIST developments, the focus is on BIST research findings which are relevant for cost reduction of BIST components and therefore necessary for the economic success of BIST technology. These are discussed, together with proposals for future research.

The paper presents a modified particle swarm optimization (MPSO) control strategy for the maximum power point tracking applied to a multilevel DC-link PV power generation system. This system consists of a chain of PV modules with individual DC-DC converters and has a DC-AC converter at its terminals for generating AC voltage. The proposed MPSO control method can predict all PV voltages at their maximum power point on the basis of respective light level and temperature. A PWM with permutation of DC converter switching is applied to balance switch utilisation. The method is applied to a system of five-voltage levels with two PV-converter units under different light intensities and the results are compared with the perturb and observe (P&O) method and the traditional PSO method under the same operating conditions. The paper shows that the new method gives more rapid convergence, increased power output, and lower total harmonic distortion.

The increase of 1.09 °C in global temperature resulted in significant catastrophes because of the extreme climate. The climate change rate can be slowed down by reducing the levels of CH4 and CO2 in the atmosphere. The solar chimney power plant integrated with a honeycomb photocatalytic reactor (SCPP-HPCR) uses the photocatalytic technology to remove atmospheric CH4. In addition, CO2 emissions can be reduced from coal fired power plant due to the generating capacity of the system. In this paper, the influence of the geometric parameters of the reactor and turbine on the overall performance of the SCPP-HPCR is studied by numerical simulation. The obtained results showed that the flow resistance inside the system was mostly caused by the HPCR at low turbine speed, and primarily by the turbine at high turbine speed. Reducing the pore diameter of the reactor could improve the photocatalytic performance of the SCPP-HPCR more than increasing the turbine speed. The SCPP-HPCR having a pore diameter of 3 mm, porosity of 0.85, and constant turbine speed of 180 rpm, built in Qianyanzhou, China, could remove 2.38 kg of CH4 and reduce 375.52 kg of CO2 in one day.

Photovoltaic (PV) energy development has increased in the last years mainly based on large utility-scale plants. These plants are characterised by a huge number of panels connected to high-power inverters occupying a large land area. An accurate estimation of the power production of the PV plants is needed for failure detection, identifying production deviations, and the integration of the plants into the power grid. Various studies have used Machine Learning estimation techniques developed on very small PV plants. This paper deals with large utility-scale plants and uses all the available information to represent the non-uniform radiation over the whole studied solar field. Variables measured in up to four meteorological stations and distributed across the plant are used. Three PV plants with 1, 2 and 4 meteorological stations have been used to develop Machine Learning models. The hyperparameters were systematically optimised, demonstrating the improvements by comparing with a simple model based on Multiple Linear Regression. The best results were obtained with the Random Forest technique for the three PV plants, providing a RMS error value ranging from 1.9% to 5.4%. The final models were compared with those found in the literature for tiny PV plants showing in general much better performance.

The performance of conventional, water based, solar thermal collectors is limited by some intrinsic limitations, such as the need for high irradiation levels and the heat loss due to the relatively high temperature of the heat transfer fluid. In order to overcome these limitations and to improve the performance of solar thermal collectors, a different kind of heat transfer fluid can be proposed. This fluid is based on the exploitation of the latent heat of fusion/solidification of suspended particles, which change their state of aggregation at a micron scale, but maintain the liquid state of the fluid at a macroscopic scale. The so-called slurry phase materials, or PCS, are examples of this kind of material. In order to evaluate the effectiveness of such a concept, a numerical model of a PCS-based flat-plate solar thermal collector has been developed, presented and discussed. This model has been derived from the well-known Hottel–Whillier model, but several changes have been implemented so that a phase change of the heat transfer fluid can be handled, as well as the thermophysical properties of a non-Newtonian fluid, such as those of a PCS. The paper presents the main and auxiliary equations that have been introduced to modify the Hottel–Whillier model. A numerical analysis conducted with the newly developed model is also presented in the paper. The aim of these simulations was to test the code and obtain a preliminary evaluation of the performance of the novel concept. Different (dynamic) boundary conditions (location, orientation, PCM concentration) were adopted to evaluate the performance of the PCS-based technology and compare it with that of a conventional solar thermal collector. The outcomes of the simulations have proved model robustness and the possibility of using it for preliminary analysis. It was also shown that the adoption of the PCS as a heat transfer fluid can lead to an increase in solar energy exploitation of different magnitude according to the climate. The greatest benefit can be achieved for cold climates. The limitations of the analysis (e.g. fixed, non-optimal flow rate) are also discussed.

The present paper discusses issues related to the three major problems of the built environment in Europe and in particular, the energy consumption of buildings, the energy poverty and the local climate change. The article introduces the idea of a zero concept world where the global impact of the three specific sectors will be diminished. The paper analyses the actual status of each sector and identifies the main problems. It discusses and sets a road map to satisfy this objective, involving future quantitative and qualitative targets for the three considered sectors while it investigates the major technological, economic and social forces and policies that have to be employed in order to minimize the energy consumption of buildings, eradicate the energy poverty and mitigate the local climate change. The links, synergies and impacts between them are analysed in a comprehensive way and the interrelated nature and characteristics of the three sectors is highlighted. The mechanisms to transform the actual problems into opportunities and appropriate drivers for future development are identified and analysed. A road map involving a full estimation of the necessary investments to fulfil the defined targets is presented. The major medium and long term benefits for the society, including the impact on the economy, employment, the environment and health are fully quantified and analysed. (C) 2016 Elsevier Ltd. All rights reserved.

This paper presents a detailed comparison of two different electronic controllers used for driving Solar Photovoltaic water pumping systems in India. A recently developed Sine-wave Pump Controller with MPPT (SPCM) having two stage converter topology offered better performance throughout the operational range, over the most popular controllers using the Variable Frequency Drives (VFD). This paper presents an exhaustive study of SPCM and VFD based controllers in terms of their operational performance at 10 m, 18 m and 20 m head, in terms of quality of output power and quantity of the total water delivered when connected to the same motor-pump set under similar conditions. SPCM with best MPPT efficiency of 99.4%, lowest THD of less than 3% and pumped 30% to 70% more water for same heads. The overall system efficiency of SPCM based pump is 18% higher than VFD based pumping system for the head corresponding to duty point. The output power quality of SPCM is considerably high, with superior sine-wave (crest-factor 1.42 and 1.56 for voltage & current), ensures no voltage spikes even at 60 m of cable length. Thus, the paper establishes performance dominance of SPCM over the VFD based controller through the measurement on actual sample. (C) 2015 Elsevier Ltd. All rights reserved.

This research focuses on daylight assessment in office buildings with different atrium types, proportions and roof aperture designs. The goal is to assess and optimize atrium type and proportions to improve energy efficiency of atrium buildings. This paper investigates daylight metrics in central, attached and semi-enclosed atrium types with different proportions and roof aperture designs, such as monitor and horizontal skylight. Daylight performance is measured based on the proportions of an atrium that are defined by Well Index (WI), used to characterize atria. Climate-Based Daylight Modeling (CBDM) is applied as the assessment strategy with U.S Climate Zone 3 as the climatic setting. Spatial Daylight Autonomy (sDA) and Annual Solar Exposure (ASE) are adopted as the dynamic daylight metrics to compare the results. This study also validates DIVA for Rhino as the simulation tool by comparing daylight results of the computer simulation with the same scale-model. This research applies both scale-model and computer simulation methods to assess daylight and energy performance in atrium buildings based on Well Index. This paper then employs DIVA simulation tool to assess daylight performance based on the Well Index. The results demonstrate that Well Index is a reliable indicator to characterize atrium proportion and confirm that Well Index works with (CBDM). Having assessed the impact of design parameters, such as climate, building thickness, material reflectance, material transmittance, furniture and monitor roof glazing height, the study potentially provides architects with an atrium design database for U.S. Climate Zone 3. This database compares daylight metrics for Well Index of 0.5, 1 and 2 in central, attached and semi-enclosed atrium types using different roof aperture designs.

To increase the efficiency of Concentrated Solar Power (CSP) plants, the use of optimization methods is a current topic of research. This paper focuses on applying an integrated optimization technology to a solar thermal application, more specifically for the optimization of a trapezoidal cavity absorber of an LFR (Linear Fresnel Reflector), also called a Linear Fresnel Collector (LFC), CSP plant. LFR technology has been developed since the 1960s, and while large improvements in efficiencies have been made, there is still room for improvement. Once such area is in the receiver design where the optimal cavity shape, coatings, insulation thickness, absorber pipe selection, layout and spacing always need to be determined for a specific application. This paper uses a commercial tool to find an optimal design for a set of operating conditions. The objective functions that are used to judge the performance of a 2-D cavity are the combined heat loss through convection, conduction and radiation, as well as a wind resistance area. In this paper the effect of absorbed irradiation is introduced in the form of an outer surface of pipe temperature. Seven geometrical parameters are used as design variables. Based on a sample set requiring 79 CFD simulations, a global utopia point is found that minimizes both objectives. The most sensitive parameters were found to be the top insulation thickness and the cavity depth. Based on the results, the Multi-Objective Genetic Algorithm (MOGA) as contained in ANSYS DesignXplorer is shown to be effective in finding candidate optimal designs as well as the utopia point.

This paper develops an optimal control strategy for power dispatch of the grid-tied photovoltaic (PV)–battery–diesel system to power heat pump water heaters (HPWH). The system consists of the PV modules, grid, battery, HPWH, diesel generator (DG) and other domestic appliances. The PV can simultaneously feed in the excess power to the grid and supply the loads. The battery is used as storage of cheaper-to-buy off-peak grid energy, dependent on the time-of-use (TOU) electricity tariff, while the DG is a backup power source to the HPWH. The objective function of the model is to minimize energy and fuel cost while maximizing PV energy trade-off for incentives. The TOU is an important control parameter in this model. The power flows from each power source are the control variables. The optimal control shows a great potential to realize a practical net zero-energy building and demand side management. This model meets both the technical and operational constraints. A case study is done based on a 3 × 16 kW HPWH installed at a Pretoria Hotel in South Africa. Simulations run over a year on selected seasonal dates using the actual measured demand of the HPWH. The optimal control problem is solved using a mixed integer non-linear program and the results show how TOU affects the power dispatch to the HPWH. The energy and cost savings are presented in this paper.

State estimation plays a key role in the development of advanced control strategies for Concentrating Solar Thermal Power (CSP) systems, by providing an estimate of process variables that are otherwise infeasible to measure. The present study proposes a state estimation scheme for a once-through direct steam generation plant, the SG4 steam generation system at the Australian National University. The state estimation scheme is a modified Extended Kalman Filter that computes an estimate of the internal variables of the mono-tube cavity receiver in the SG4 system, from a dynamic non-linear model of the receiver. The proposed scheme augments the capabilities of a Continuous-Direct Extended Kalman Filter to deal with the switched nature of the receiver, in order to produce estimates during system start-up, cloud transients and operation of the plant. The estimation process runs at regular sample intervals and happens in two stages, a prediction and a correction stage. The prediction stage uses the receiver model to calculate the evolution of the system and the correction stage modifies the predicted estimate from measurements of the SG4 system. The resulting estimate is a set of internal variables describing the current state of the receiver, termed the state vector. This paper presents a description of the modified Extended Kalman Filter and an evaluation of the scheme using computer simulations and experimental runs in the SG4 system. Simulations and experimental results in this paper show that the filtering scheme improves a receiver state vector estimation purely based on the receiver model and provides estimates of a quality sufficient for closed loop control.

A detailed methodology to design the size of solar field for a parabolic trough plant is not explicitly available in open literature, particularly if thermal storage and hybridization are also considered, as most of the papers present a gross overview. This paper gives a procedure to determine the annual electricity generated for a parabolic trough based solar plant of a given rated capacity (1–50 MWe), at a chosen location & given hourly annual solar input, specified hours of thermal energy storage using a two-tank molten salt system and specified fraction of hybridization using natural gas. In this methodology losses due to shut down or cloud cover are also covered. The size of the solar field is optimized for the maximum annual solar to electric conversion efficiency using the concept of solar multiple (ratio of actual aperture area to the reference aperture area needed to get rated power output at maximum solar input). This procedure is validated with the existing parabolic trough plants (Solar Energy Generating Systems VI and Solana Generating Station) and it was found that the annual electrical energy generated by the plant matches reasonably well. Jodhpur, in India, was considered as a location for the case study and the results are presented to understand the influence of thermal storage and hybridization for a given capacity of the plant. The results for various combinations of thermal storage hours and fraction of hybridization used with respect to plant capacity, solar multiple, annual plant efficiency etc. have been discussed in detail. It is observed from the results that, under design conditions, the reference aperture area per MW decreases as plant capacity increases and reaches a limiting value asymptotically at a capacity of 50 MW. The optimized size of the solar field, with respect to annual efficiency, is found to be 1.4 and 2.3 times the size under design conditions for zero and six hours thermal storage respectively. The benefit of hybridization is high for lower solar multiples.

Energy storage at low maintenance cost is one of the key challenges for generating electricity from the solar energy. This paper presents the theoretical analysis (verified by CFD) of the night time performance of a recently proposed conceptual system that integrates thermal storage (via phase change materials) and thermophotovoltaics for power generation. These storage integrated solar thermophotovoltaic (SISTPV) systems are attractive owing to their simple design (no moving parts) and modularity compared to conventional Concentrated Solar Power (CSP) technologies. Importantly, the ability of high temperature operation of these systems allows the use of silicon (melting point of 1680 K) as the phase change material (PCM). Silicon’s very high latent heat of fusion of 1800 kJ/kg and low cost ($1.70/kg), makes it an ideal heat storage medium enabling for an extremely high storage energy density and low weight modular systems. In this paper, the night time operation of the SISTPV system optimised for steady state is analysed. The results indicate that for any given PCM length, a combination of small taper ratio and large inlet hole-to-absorber area ratio are essential to increase the operation time and the average power produced during the night time. Additionally, the overall results show that there is a trade-off between running time and the average power produced during the night time. Average night time power densities as high as 30 W/cm 2 are possible if the system is designed with a small PCM length (10 cm) to operate just a few hours after sun-set, but running times longer than 72 h (3 days) are possible for larger lengths (50 cm) at the expense of a lower average power density of about 14 W/cm 2 . In both cases the steady state system efficiency has been predicted to be about 30%. This makes SISTPV systems to be a versatile solution that can be adapted for operation in a broad range of locations with different climate conditions, even being used off-grid and in space applications.

The paper describes the methodology followed for the development of new cool products in order to widen the range of existing solutions both including coloured (even dark) materials and extending the application also to building vertical components. Cool coloured ceramic tiles and acrylic paints for façades and roof membranes have been developed and tested at lab scale. Spectral reflectance measurements have been performed demonstrating a significant improvement of reflectance in the Near InfraRed (NIR) range (up to. +0.40) while keeping dark colour and high absorbance in the visible. The development of new products has been also oriented to the improvement of durability properties, being this aspect of relevance for high reflecting materials that have to keep their cooling properties over the time. While ceramic tiles naturally offer superior resistance to outdoor ageing, a significant increase of biological growth resistance has been achieved also for roof membranes by including ZnO nanoparticles. The approach followed by the authors aimed at delivering products, that besides having higher NIR reflectance, were capable of satisfying industrial and market requirements being compatible with standard manufacturing processes and offering additional functionalities. A complementary paper will be dedicated to the extensive experimental and numerical evaluation of new materials' thermal performances. © 2014 Elsevier Ltd.

There is a general consensus that solar power is one of the cleanest energy technologies available. Nevertheless, investment in large-scale Solar Power Generators (SPGs) is largely impeded by the intermittent nature of solar power. Since the electricity market has a critical responsibility to maintain the reliability of energy supply, the SPG can be registered only as the market semi-scheduled generator (AEMC, 2011). This option excludes the advantages of providing baseload supply, which in turn impedes efficient market contracting for SPGs. The existing approach relies on energy storage or co-generation facilities to be built at the same connection point as the SPG to compensate for output shortages when there is insufficient sunlight. The co-located facilities require significant additional investment in infrastructure.This paper proposes a market based financial approach that does not require an additional construction effort. The approach financially links solar or other intermittent power generation with a gas-fired station through a set of tailored swap-type instruments.These swaps (based on solar energy forecasting) are designed to insure and hedge the SPG against a drop in its output. They contractually link physically separated solar and gas generators to form a single entity termed the Virtual Generator (VG). The VG arrangement requires the SPG to provide solar power when possible and the gas generator to kick in when there is any shortfall due to random clouds or at nightfall. Thus the proposed VG will have the capacity to produce reliable baseload supply. The profitability and design of the proposed financial setup for both the solar and gas generator has been tested in this research. The model has been prototyped on real market and solar data, the results demonstrate the benefits of implementation. While the paper is focused on links with gas generators, the developed financial setup is applicable to a broad range of fast-ramping power generators, such as hydro, including pumped-hydro storage as well as electrical batteries and biofuels. © 2013 Elsevier Ltd.

Heat extraction from the Non-Convective Zone (NCZ) or gradient layer and Lower Convective Zone (LCZ) of the solar pond has been investigated through one-dimensional finite difference transient model. Instantaneous efficiency of the solar pond is introduced and defined in this paper. The solar pond considered in the present study is assumed to have an in-pond heat exchanger for heat extraction. The rate of heat transfer is controlled by the mass flux of heat transfer fluid in this model. As in reality mass flux of heat transfer fluid is the simplest and most practical way to control the rate of heat extraction. In this model for an ideal situation it is assumed that the heat transfer fluid is initially at the local daily average ambient temperature and the in-pond heat exchanger has heat transfer effectiveness equal to unity. With these assumptions the model can predict the thermal performance of the solar pond with maximum heat extraction for a desired mass flux of the heat transfer fluid. This paper presents the comparison of the transient thermal performance of solar pond with heat extraction from LCZ alone and that with combined heat extraction from LCZ and NCZ. It is shown how the efficiency of the solar pond increases when heat is extracted from both NCZ and LCZ. The main objective of this study is to offer a simple method to predict transient thermal performance of a solar pond with heat extraction from NCZ and to estimate the mass flux of heat transfer fluid used in an in-pond heat exchanger for heat extraction from different layers of solar pond. � 2013 Elsevier Ltd.

The association of concentrated solar energy and biomass gasification has often been suggested as an interesting alternative to conventional autothermal processes where a significant portion of the biomass has to be used for heat generation to drive endothermic reactions. It is a clean process able to produce high quality synthesis gas with a higher output per unit of feedstock and that allows for the chemical storage of solar energy in the form of a readily transportable fuel, among other advantages. The present paper describes the latest advances in solar thermochemical reactors for gasification of carbonaceous feedstocks. This work is categorized in this paper into patents and research/journal papers.

Concentrating Solar Cookers (CSCs) are well-known for fast cooking and can significantly contribute to attaining the United Nation's sustainable development goals. CSCs attain intermediate temperatures (120-240 degrees C) and are suitable for several cooking applications. The realistic rating and grading of CSCs is inevitable for establishing their usefulness in urban areas, which is the main objective of the present work. This paper reveals the experimental results of two existing concentrating solar cookers with different geometries and aperture areas. The first cooker is a shallow satellite antenna parabolic dish, and the other is a small deep parabola. Cooker Opto-thermal Ratio (COR) acts as a thermal performance parameter, and glycerin as a test load for their performance evaluation.The mean values of COR for the cookers, CSC1, and CSC3, are 0.180 and 0.092, respectively. The typical theoretical values of maximum achievable fluid temperature are 192.9 and 113.9 degrees C, respectively, and that for reference time are 23.8 and 60.5 min for CSC1 and CSC3, respectively. COR identifies the variation in the performance of CSCs based on a design change. The objective parameters enable realistic intra-cooker performance comparison of the CSCs at intermediate temperatures. The results depict that the existing designs of CSCs can be graded appropriately using COR and provide new insights into their performance at intermediate temperatures realistically. TPP-based realistic rating and grading of existing designs of solar cookers enable their effortless selection as per end-user requirements and help in the faster propagation of solar cooking technology in urban and semi-urban areas. Solar Energy Research Center (SERC), Chile, FONDAP/ANID grant number 15110019 info:eu-repo/semantics/publishedVersion

Off-axis incidence is inherent to sun tracking mirrors, named heliostats. Moreover, heliostat defocus takes place, provided that the focal length of the mirrors usually differs from their distance to the target. Defocus, along with high incidence angles, lead to astigmatic aberrations, that are overlooked by analytic functions based on convolution. This paper presents an analytic function on the image plane that reproduces these aberrations. As the reflection of the heliostat axes is non-orthogonal with defocus, the identification of the reflected axes plays a key role in the resulting model. In comparison with Monte Carlo Ray-Tracing, the model shows correlation coefficients above 90%, except at the tangential and sagittal foci, where the analytic function is indeterminate. An astigmatic parameter is provided to assess the model validity, which is complementary to UNIZAR at high incidence angles. This work has been supported by the Madrid Government (Comunidad de Madrid), Spain under the Multiannual Agreement with UC3M in the line of "Fostering Young Doctors Research" (VISHELIO-CM-UC3M), and in the context of the V PRICIT (Regional Programme of Research and Technological Innovation). Funding for APC: Universidad Carlos III de Madrid (Read & Publish Agreement CRUE-CSIC 2022).

While many remote water pumping systems exist (e.g. mechanical windmills, solar photovoltaic, wind-electric, diesel powered), few combine both the wind and solar energy resources to possibly improve the reliability and the performance of the system. In this paper, off-grid wind turbine (WT) and solar photovoltaic (PV) array water pumping systems were analyzed individually and combined as a hybrid system. The objectives were to determine: (1) advantages or disadvantages of using a hybrid system over using a WT or a solar PV array alone; (2) if the WT or solar PV array interfered with the output of the other; and (3) which hybrid system was the most efficient for the location. The WT used in the analysis was rated at 900 W alternating current (AC). There were three different solar PV arrays analyzed, and they were rated at 320, 480, and 640 W direct current (DC). A rectifier converted the 3-phase variable voltage AC output from the WT to DC before combining it with the solar PV array DC output. The combined renewable energies powered a single helical pump. The independent variable used in the hybrid WT/PV array analysis was in units of W/m 2 . The peak pump efficiency of the hybrid systems at Bushland, TX occurred for the 900 W WT combined with the 640 W PV array. The peak pump efficiencies at a 75 m pumping depth of the hybrid systems were: 47% (WT/320 W PV array), 51% (WT/480 W PV array), and 55% (WT/640 W PV array). Interference occurred between the WT and the different PV arrays (likely due to voltage mismatch between WT and PV array), but the least interference occurred for the WT/320 W PV array. This hybrid system pumped 28% more water during the greatest water demand month than the WT and PV systems would have pumped individually. An additional controller with a buck/boost converter is discussed at end of paper for improvement of the hybrid WT/PV array water pumping system.

Zero energy buildings (ZEB) and zero energy homes (ZEH) are a current hot topic globally for policy makers (what are the benefits and costs), designers (how do we design them), the construction industry (can we build them), marketing (will consumers buy them) and researchers (do they work and what are the implications). This paper presents initial findings from actual measured data from a 9 star (as built), off-ground detached family home constructed in south-east Queensland in 2008. The integrated systems approach to the design of the house is analysed in each of its three main goals: maximising the thermal performance of the building envelope, minimising energy demand whilst maintaining energy service levels, and implementing a multi-pronged low carbon approach to energy supply. The performance outcomes of each of these stages are evaluated against definitions of Net Zero Carbon / Net Zero Emissions (Site and Source) and Net Zero Energy (onsite generation vs primary energy imports). The paper will conclude with a summary of the multiple benefits of combining very high efficiency building envelopes with diverse energy management strategies: a robustness, resilience, affordability and autonomy not generally seen in housing.