•A 2D analytical wind turbine wake model named Jensen–Gaussian wake model is proposed.•The velocity deficit predicted by Jensen–Gaussian model is validated with literature.•The Jensen–Gaussian model ...is improved by a proposed turbulence model.•The Jensen–Gaussian wake model is applied for the turbine layout optimization.•The performance of Jensen–Gaussian model on turbine layout optimization is validated.
The development and validation of a 2D analytical wind turbine wake model based on Jensen’s wake model using Gaussian function is presented in this paper. The velocity deficit predicted by the newly-developed Jensen–Gaussian wake model is compared with wind tunnel experimental measured data in literatures and results show that, the velocity deficit predicted by the model fits well with the measured data at different downwind distances of X=2.5D, X=5D, X=7.5D and X=10D. Considering the turbulence inside the turbine wake, a new turbulence model is developed and based on this, the Jensen–Gaussian wake model was improved and validated. The 2D Jensen–Gaussian wake model is then applied in the wind turbine layout optimizing process within a wind farm based on the multiple populations genetic algorithm (MPGA). The performance of this newly 2D model in the optimization process is validated and compared with the results presented in some typical studies on the turbine layout optimization. The comparison is performed for ‘constant wind speed of 12m/s with variable wind directions’. Using the 2D Jensen–Gaussian wake model instead of Jensen’s wake model in the MPGA turbine layout optimization program, both the total power generation and wind farm efficiency decreased. The wind farm efficiency drop to 77.83%, 78.47% and 81.84% from 96.83%, 96.34% and 96.23% for 38, 39 and 40 wind turbines, respectively which is in accordance with the literatures on the power losses caused by wake effect in large wind farm. The development and application of the 2D Jensen–Gaussian wake model means moretheorysignificance and practicalvalues in wind energy utilization.
This paper presents a detailed feasibility study and techno-economic evaluation of a standalone hybrid solar-wind system with battery energy storage for a remote island. The solar radiation and wind ...data on this island in 2009 was recorded for this study. The HOMER software was employed to do the simulations and perform the techno-economic evaluation. Thousands of cases have been carried out to achieve an optimal autonomous system configuration, in terms of system net present cost (NPC) and cost of energy (COE). A detailed analysis, description and expected performance of the proposed system were presented. Moreover, the effects of the PV panel sizing, wind turbine sizing and battery bank capacity on the system's reliability and economic performance were examined. Finally, a sensitivity analysis on its load consumption and renewable energy resource was performed to evaluate the robustness of economic analysis and identify which variable has the greatest impact on the results. The results demonstrate the techno-economic feasibility of implementing the solar-wind-battery system to supply power to this island.
This paper aims to examine the sustainability and environmental performance of PV-based electricity generation systems by conducting a thorough review of the life cycle assessment (LCA) studies of ...five common photovoltaic (PV) systems, i.e., mono-crystalline (mono-Si), multi-crystalline (multi-Si), amorphous silicon (a-Si), CdTe thin film (CdTe) and CIS thin film (CIS), and some advanced PV systems. The results show that, among the five common PV systems, the CdTe PV system presents the best environmental performance in terms of energy payback time (EPBT) and greenhouse gases (GHG) emission rate due to its low life-cycle energy requirement and relatively high conversion efficiency. Meanwhile, the mono-Si PV system demonstrates the worst because of its high energy intensity during the solar cells’ production process. The EPBT and GHG emission rate of thin film PV systems are within the range of 0.75–3.5 years and 10.5–50g CO2-eq./kWh, respectively. In general, the EPBT of mono-Si PV systems range from 1.7 to 2.7 years with GHG emission rate from 29 to 45g CO2-eq./kWh, which is an order of magnitude smaller than that of fossil-based electricity. This paper also reviews the EPBT and GHG emission rates of some advanced PV systems, such as high-concentration, heterojunction and dye-sensitized technologies. The EBPT of high-concentration PV system is lower, ranging from 0.7 to 2.0 years, but the CO2 emission rate of dye-sensitized PV system is higher than the ones of other PV systems at the moment. The LCA results show that PV technologies are already proved to be very sustainable and environmental-friendly in the state of the art. With the emerging of new manufacturing technologies, the environmental performance of PV technologies is expected to be further improved in the near future. In addition, considering the existing limitations in the previous LCA studies, a few suggestions are recommended.
•Batteries and pumped hydro storage schemes are examined.•Sizing procedure for each option is investigated in detail.•The two schemes are compared in terms of life cycle cost and technical ...viability.•Sensitivity analyses are conducted on five key input parameters.
This study examined and compared two energy storage technologies, i.e. batteries and pumped hydro storage (PHS), for the renewable energy powered microgrid power supply system on a remote island in Hong Kong. The problems of energy storage for off-grid renewable energy were analyzed. The sizing methods and economic models were developed, and finally applied in the real project (case study). The results provide the most suitable energy storage scheme for local decision-makers. The two storage schemes were further divided into 4 options. Accordingly, the life-cycle costs (LCC), levelized costs for the renewable energy storage system (LCRES) and the LCC ratios between all options were calculated and compared. It was found that the employment of conventional battery (Option 2) had a higher LCC value than the advanced deep cycle battery (Option 1), indicating that using deep cycle batteries is more suitable for a standalone renewable power supply system. The pumped storage combined with battery bank option (Option 3) had only 55% LCC of that of Option 1, making this combined option more cost-competitive than the sole battery option. The economic benefit of pumped storage is even more significant in the case of purely pumped storage with a hydraulic controller (Option 4), with the lowest LCC among all options at 29–48% of Option 1. Sensitivity analysis demonstrates that PHS is even more cost competitive by controlling some adjustments such as increasing energy storage capacity and days of autonomy. Therefore, the renewable energy system coupled with pumped storage presents technically feasible opportunities and practical potential for continuous power supply in remote areas.
A simulation model for modeling photovoltaic (PV) system power generation and performance prediction is described in this paper. First, a comprehensive literature review of simulation models for PV ...devices and determination methods was conducted. The well-known five-parameter model was selected for the present study, and solved using a novel combination technique which integrated an algebraic simultaneous calculation of the parameters at standard test conditions (STC) with an analytical determination of the parameters under real operating conditions. In addition, the simulation performance of the model was compared with other models, and further validated by outdoor tests, which indicate that the proposed model fits well the entire set of experimental field test I–V curves of the PV module, especially at the characteristic points. After validation, this model was employed to predict the PV system power output under real conditions. The results show that the predictions agree very well with the PV plant field collected data. Thus, the operating performance of a standalone PV system located on a remote island in Hong Kong has been further evaluated with the aid of this model. It is found that the PV array power output is restricted by the status of the battery bank. This research demonstrates that the PV simulation model developed during the study is simple, but very helpful to PV system engineers in understanding the I–V curves and for accurately predicting PV system power production under outdoor conditions.
•We made a tranparent super-hydrophilic glass coating via a silane coupling agent.•We used TEOS to enhance the adhesion force of the coating.•We fitted the exponential formulas describing the ...relation between contact angle values and the silane coupling agent’s concentrations.
The soiling of the photovoltaic (PV) modules’ front surfaces decreases the power generation efficiency a lot. In this paper, a novel self-cleaning (super-hydrophilic) glass coating material with double layers’ structure is prepared and the synthesis process is simple and low-price. This super-hydrophilic coating barely decreases the transparency of the glass above solar cells in the PV modules. It only reduces about 2.9% of transparency compared with original glass. Briefly, TEOS (Tetraethylorthosilicate) is skillfully utilized as hydrophobic interlayer, connected to the substrate surface and super-hydrophilic layer, whose effective component is a particular silane-coupling agent named as 2-acetoxy (polyethyleneoxy) propyl triethoxysilane (abbreviated as SIA). The interlayer has three advantages: firstly, after the TEOS hydrophobic layer is coated, SIA’s hydrophobic siloxane terminals assemble toward this layer; secondly, SIA’s steric hindrance would decrease obviously because most of the molecules assemble orderly on the interlayer; thirdly, TEOS provides much more grafting sites and more SIA molecules are grafted. Thus, with the increasing TEOS’s concentration, the SIA’s coating becomes firmer, and the SIA’s concentration influences the water contact angle (CA). When it is bigger than 2.5%, the CA is less than 10° and the surface turns to super-hydrophilic. Besides, according to the samples with different SIA’s concentration and contact angle value, a fitting curve whose R2 is higher than 0.95 is made. Based on this, the experimental contact angle value of a surface made from this SIA could be predicted. And the difference between experimental and theoretical contact angle value ranges from 1.11% to 5.88%.
•Develop a parameter determination method for PV module.•Develop a theoretical and simulation model for PV modules/strings/arrays.•Predict PV module/string/array output using this newly developed ...model.•Validate simulation results through field measurements of a real PV system.•Good agreement can be observed between the measured and predicted curves.
In this study, a novel theoretical model, offering a good compromise between accuracy and simplicity, was developed in Matlab for determining solar photovoltaic (PV) module parameters and then fitting the model to experimental I–V characteristic curves of a PV module/string/array. A few inputs are only needed for the model, which can be obtained from the manufacturer datasheet. With this newly developed model, the performance of a PV module/string/array at any solar irradiance and module cell temperature can be easily simulated. To validate the simulation model, the parameters from the simulation and I–V characteristic curves were compared with those from the DeSoto model and other simulation software (INSEL and PVsyst) at different temperature and irradiation. The comparison results present a high degree of agreement. Moreover, a series of field measurements were carried out from an existing 22kWp grid-connected PV system located in The Hong Kong Polytechnic University to further validate the simulation results at a wide range of real operating conditions. To have more realistic results, the model was then slightly modified by including the effect of soiling, aging and other derating factors. Field test results demonstrate that the modified simulation model can accurately predict the I–V curve characteristics of PV modules/strings/arrays demonstrating the feasibility and reliability of the developed simulation model.
The intermittent characteristic of a solar-alone or a wind-alone power generation system prevents the standalone renewable energy system from being fully reliable without suitable energy storage ...capability. In this study, the most traditional and mature storage technology, pumped hydro storage (PHS), is introduced to support the standalone microgrid hybrid solar-wind system. This paper explores a new solution for the challenging task about energy storage. A mathematical model of the hybrid system is developed and the operating principle is introduced. The proposed system is applied in a case study to power a remote island in Hong Kong, and its technical feasibility is then examined. The hour-by-hour simulation results indicate that the intermittent nature of the renewables can be compensated by introducing the PHS technology. Therefore, a reliable and environmentally friendly power supply can be provided. The results demonstrate that technically the PHS based renewable energy system is an ideal solution to achieve 100% energy autonomy in remote communities.
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•Pumped hydro storage is proposed for stand-alone hybrid solar-wind systems.•Mathematical model and operation principle are developed.•A case study is conducted using the model for a research project on a remote island.•Technical feasibility of this system is examined through simulation.
Ground source heat pump (GSHP) is widely studied for building energy efficiency but suffers from soil thermal imbalance and performance deterioration in heating-dominant regions. Photovoltaic (PV) ...collector is commonly used for renewable energy, but the efficiency is constrained by the PV module temperature. The combination of GSHP and photovoltaic/thermal (PVT) is promising to improve the performance of both individual technologies. A comprehensive review has been conducted to present the state-of-the-art of the hybrid PVT-GSHP, in terms of the principles, configurations, and functions. The basic PVT-GSHP systems are classified into four categories: the hybrid PVT-GSHP with PVT for direct heating, the hybrid PVT-GSHP with PVT for temperature increasing, the hybrid PVT-GSHP with multiple energy sources, and the hybrid-GSHP with energy storage/borehole recharge. These hybrid systems can be further combined to achieve advanced hybrid PVT-GSHP systems with more functions and improved performance. For the hybrid PVT-GSHP with PVT for direct heating, preheating and full heating have been used; the preheating yields a higher PV efficiency while the full heating recovers more heat. The hybrid PVT-GSHP with PVT for temperature increasing is more widely adopted, with both PVT electrical efficiency and GSHP heating efficiency significantly improved. For the hybrid PVT-GSHP with multiple energy sources, the current systems were limited to the integration of an air source heat pump as an additional heat source or a cooling tower as an additional heat sink. The hybrid PVT-GSHP with energy storage/ground recharge received the most intensive investigations owing to the reduced thermal imbalance and thus enhanced long-term performance. While most studies used normal flat-plate PVT, advanced collectors including concentrating PVT, building-integrated PVT, and solar-road PVT have also been studied. To facilitate performance improvement and application promotion, some perspectives on future development are presented: (1) advanced ground heat exchangers, i.e., energy geo-structures including the energy pile, energy wall, and energy tunnel; (2) advanced PVT types, i.e., more involvements in the high-temperature PVT and building-integrated PVT; (3) advanced hybrid systems, including driving sorption chillers, regenerating desiccant dehumidifiers, charging thermal batteries; and (4) optimal design and operation, considering local soil properties (e.g. seepage) and climate conditions through transient modeling. This study can facilitate future research, development, and promotion of the hybrid PVT-GSHP technology towards low-carbon buildings.
•The principles, configurations, and functions of hybrid PVT-GSHP are reviewed.•PVT for direct heating and temperature increasing improves system efficiency.•Hybrid PVT-GSHP can work with multiple energy sources or for energy storage.•Advanced ground heat exchangers and solar collectors should be promoted.•Design scheme and operation strategy should be optimized for hybrid PVT-GSHP.
BIPV windows integrate solar cells within window glazing and do not only retain the functionality of conventional windows but also provide other benefits such as electricity generation and thermal ...insulation. BIPV windows are categorized into single glazed BIPV windows, double glazed BIPV windows with/without ventilation and vacuum BIPV windows depending on the configurations of the glazing. The electricity generation, thermal performance and optics of BIPV windows are reviewed in this paper. The results of this study showed that the total heat gain through BIPV windows are less than conventional windows in summer and hence the electricity used by air-conditioning in summer would be reduced. In addition to the electricity produced by BIPV windows, there are great potentials to reduce building energy consumption significantly in hot climate areas. The development and performance of BIPV blinds which integrate solar cells with blinds are also reviewed. BIPV blinds are grouped into outdoor PV blinds, indoor PV blinds and middle PV blinds according to the position of blinds relative to the windows. Future research directions are also suggested for this research domain.
•The BIPV windows are grouped according to the configurations of the glazing.•The power generation, thermal performance and optics of BIPV windows are reviewed.•The development and performance of BIPV blinds are also discussed.
