Exergoeconomic analysis of glazed hybrid photovoltaic thermal module air collector

In this paper, an exergoeconomic analysis has been carried out and on the basis of this analysis it has been concluded that in terms of energy saving the glazed hybrid photovoltaic thermal (PVT) module air collector offers a greater potential compared to PV module. The experimental validation for glazed hybrid PVT module air collector has also been performed and it has been observed that there is a good agreement between the theoretical and experimental values with correlation coefficient in range of 0.96–0.99 and root mean square percentage deviation in range of 2.38–7.46. The experiments have been carried out on clear days during the month July 2010 to June 2011. For the validation of theoretical results with experimental results, a typical day of winter month (December 08, 2010) and summer month (April 11, 2011) has been considered. An experimental uncertainty for December and April month is 11.6% and 2.1% respectively. The annual overall thermal energy and exergy gain are 1252.0 kWh and 289.5 kW h respectively. The annual net electrical energy savings by glazed hybrid PVT module air collector is 234.7 kW h.     

The effect of hybrid photovoltaic thermal device operating conditions on intrinsic layer thickness optimization of hydrogenated amorphous silicon solar cells

Historically, the design of hybrid solar photovoltaic thermal (PVT) systems has focused on cooling crystalline silicon (c-Si)-based photovoltaic (PV) devices to avoid temperature-related losses. This approach neglects the associated performance losses in the thermal system and leads to a decrease in the overall exergy of the system. Consequently, this paper explores the use of hydrogenated amorphous silicon (a-Si:H) as an absorber material for PVT in an effort to maintain higher and more favorable operating temperatures for the thermal system. Amorphous silicon not only has a smaller temperature coefficient than c-Si, but also can display improved PV performance over extended periods of higher temperatures by annealing out defect states from the Staebler–Wronski effect. In order to determine the potential improvements in a-Si:H PV performance associated with increased thicknesses of the i-layers made possible by higher operating temperatures, a-Si:H PV cells were tested under 1 sun illumination (AM1.5) at temperatures of 25 °C (STC), 50 °C (representative PV operating conditions), and 90 °C (representative PVT operating conditions). PV cells with an i-layer thicknesses of 420, 630 and 840 nm were evaluated at each temperature. Results show that operating a-Si:H-based PV at 90 °C, with thicker i-layers than the cells currently used in commercial production, provided a greater power output compared to the thinner cells operating at either PV or PVT operating temperatures. These results indicate that incorporating a-Si:H as the absorber material in a PVT system can improve the thermal performance, while simultaneously improving the electrical performance of a-Si:H-based PV.     

Overall thermal energy and exergy analysis of hybrid photovoltaic thermal array

In this paper, overall thermal energy and exergy analysis has been carried out for different configurations of hybrid photovoltaic thermal (PVT) array. The hybrid PVT array (10.08 m × 2.16 m) is a series and parallel combinations of 36 numbers of PV modules. A one-dimensional transient model for hybrid PVT array has been developed using basic heat transfer equations. On the basis of this transient model, an attempt has been made to select an appropriate hybrid PVT array for different climatic conditions (Bangalore, Jodhpur, New Delhi, and Srinagar) of India. On the basis of high grade energy (i.e. overall exergy gain), case-III has been selected as the most appropriate configuration because overall exergy for case-III is 12.9% higher than case-II. The overall thermal energy and exergy gain for Bangalore is 4.54 × 10⁴ kW h and 2.07 × 10⁴ kW h respectively which is highest in comparison to the other cities.     

Energy matrices analyses of hybrid photovoltaic thermal (HPVT) water collector with different PV technology

In this paper, an attempt has been made to evaluate and compare the energy matrices of a hybrid photovoltaic thermal (HPVT) water collector under constant collection temperature mode with five different types of PV modules namely c-Si, p-Si, a-Si (thin film), CdTe and CIGS. The analysis is based on overall thermal energy and exergy outputs from HPVT water collector. The temperature dependent electrical efficiency has also been calculated under composite climate of New Delhi, India.It is observed that c-Si PV module is best alternative for production of electrical power. Maximum annual overall thermal energy and exergy is obtained for c-Si PV module. The maximum and minimum EPBT of 1.01 and 0.66 years on energy basis is obtained for c-Si and CIGS respectively, whereas on exergy basis maximum EPBT of 5.72 years is obtained for a-Si and minimum of 3.44 in obtained for CIGS PV module. EPF and LCCE increase with increasing the life time of the system.     

Performance evaluation of water and air based PVT solar collector for hydrogen production application

This study aims to investigate the performance of the Photovoltaic Thermal (PVT) collector based hydrogen production system. For this purpose, a solar assisted water splitting system is fabricated. This system comprises the array of photovoltaic (PV) cells with 0.303 m² surface area, a spiral flow thermal collector with 12.7 mm outer diameter, 10.26 mm internal diameter, 10 m length copper tube and Hoffman voltameter. The results have been taken for three different mass flow rates (0.008, 0.01 and 0.011 kg/s) and compared with the reference PV module. This study results clearly show that the collector outlet temperature, output voltage and output power increase as the flow rate increases and the PV module temperature decreases with an increase of flow rate. The maximum thermal and electrical efficiency of 33.8% and 8.5% are observed for water based PVT solar collector with 0.011 kg/s flow rate at 12.00. It is also noted that the hydrogen yield rate increases significantly with an increase in flow rate. The highest hydrogen yields of 17.1 ml/min are obtained at a fluid flow rate of 0.011 kg/sec at 12.00.     

A probabilistic method for calculating the usefulness of a store with finite energy capacity for smoothing electricity generation from wind and solar power

This paper describes a novel method of modelling an energy store used to match the power output from a wind turbine and a solar PV array to a varying electrical load. The model estimates the fraction of time that an energy store spends full or empty. It can also estimate the power curtailed when the store is full and the unsatisfied demand when the store is empty. The new modelling method has been validated against time–stepping methods and shows generally good agreement over a wide range of store power ratings, store efficiencies, wind turbine capacities and solar PV capacities.Example results are presented for a system with 1 MW of wind power capacity, 2 MW of photovoltaic capacity, an energy store of 75% efficiency and a range of loads from 0 to 3 MW average.     

Three-dimensional thermal modeling of a photovoltaic module under varying conditions

Photovoltaic technology provides the direct method to convert solar energy into electricity. Modeling and simulation plays a very important role in the development of PV devices as well as in the design of PV systems. The objective of the current work was to develop a novel thermal model to simulate the thermal performance of PV modules with and without cooling. The model was sequentially coupled with a radiation model and an electrical model to calculate the electrical performance of the PV panels. Using the developed model, various studies were performed to evaluate the electrical and thermal performance of the module under different environmental and operating conditions with and without cooling. Results show that the performance of the PV panel with cooling had very little influence of increasing absorbed radiation (200–1000 W/m²) at a constant ambient temperature (25 °C) and increasing ambient temperature (0–50 °C) at an absorbed radiation of 800 W/m². For the same variation in conditions, the performance of the panel without any cooling reduced significantly.     

Energy analysis of batteries in photovoltaic systems. Part II: Energy return factors and overall battery efficiencies

Energy return factors and overall energy efficiencies are calculated for a stand-alone photovoltaic (PV)-battery system. Eight battery technologies are evaluated: lithium-ion (nickel), sodium–sulphur, nickel–cadmium, nickel–metal hydride, lead-acid, vanadium-redox, zinc–bromine and polysulphide–bromide. With a battery energy storage capacity three times higher than the daily energy output, the energy return factor for the PV-battery system ranges from 2.2 to 10 in our reference case. For a PV-battery system with a service life of 30 yr, this corresponds to energy payback times between 2.5 and 13 yr. The energy payback time is 1.8–3.3 yr for the PV array and 0.72–10 yr for the battery, showing the energy related significance of batteries and the large variation between different technologies. In extreme cases, energy return factors below one occur, implying no net energy output. The overall battery efficiency, including not only direct energy losses during operation but also energy requirements for production and transport of the charger, the battery and the inverter, is 0.41–0.80. For some batteries, the overall battery efficiency is significantly lower than the direct efficiency of the charger, the battery and the inverter (0.50–0.85). The ranking order of batteries in terms of energy efficiency, the relative importance of different battery parameters and the optimal system design and operation (e.g. the use of air conditioning) are, in many cases, dependent on the characterisation of the energy background system and on which type of energy efficiency measure is used (energy return factor or overall battery efficiency).     

Performance analysis of a novel hydrogen production system incorporated with hybrid solar collector and phase change material

In this technical article, a novel experimental setup is designed and proposed to produce a hydrogen by using solar energy. This system comprises a hybrid or photovoltaic Thermal (PVT) solar collector, Hoffman's voltameter, heat exchanger unit and Phase Change Material (PCM). The effect of PCM and mass flow rate of water on the hybrid solar collector efficiency and hydrogen yield rate is studied. This experimental results clearly showed that by adding the thermal collector with water, decreases PV module temperature by 20.5% compared with conventional PV module. Based on the measured values, at 12.00 and 0.011 kg/s mass flow rate, about 33.8% of thermal efficiency is obtained for water based hybrid solar collector. Similarly, by adding Paraffin PCM to the water based thermal collector, the maximum electrical efficiency of 9.1% is achieved. From this study, the average value of 17.12% and 18.61% hydrogen yield rate is attained for PVT/water and PVT/water with PCM systems respectively.     

非晶硅太阳能光伏/光热空气集热器性能对比实验研究

文章设计了新型非晶硅太阳能PV/T空气集热器,该空气集热器能够解决传统太阳能PV/T热水器在高温波动情况下,晶硅电池热应力大的问题,同时避免了冬季管道发生霜冻的现象。文章通过实验对比,分析了非晶硅太阳能PV/T空气集热器、单独非晶硅光伏电池和传统太阳能空气集热器的能量效率和[火用]效率的差异。分析结果表明:非晶硅太阳能PV/T空气集热器的平均热效率为45.70%,比传统太阳能空气集热器的平均热效率降低了约25.88%;当空气质量流量增大至0.048 kg/s时,非晶硅太阳能PV/T空气集热器中的非晶硅光伏电池的平均电效率高于单独非晶硅光伏电池,它们的平均电效率分别为4.70%,4.54%;非晶硅太阳能PV/T空气集热器的总[火用]效率高于传统太阳能空气集热器的热[火用]效率和单独非晶硅光伏电池的电[火用]效率,非晶硅太阳能PV/T空气集热器总[火用]效率最大值为7.14%。文章的分析结果为非晶硅太阳能PV/T空气集热器的推广提供了参考。     

Analysis of off-grid hybrid wind turbine/solar PV water pumping systems

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/m². 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.     

Industrial application of PV/T solar energy systems

Hybrid photovoltaic/thermal (PV/T) systems consist of PV modules and heat extraction units mounted together. These systems can simultaneously provide electrical and thermal energy, thus achieving a higher energy conversion rate of the absorbed solar radiation than plain photovoltaics. Industries show high demand of energy for both heat and electricity and the hybrid PV/T systems could be used in order to meet this requirement. In this paper the application aspects in the industry of PV/T systems with water heat extraction is presented. The systems are analyzed with TRNSYS program for three locations Nicosia, Athens and Madison that are located at different latitudes. The system comprises 300 m² of hybrid PV/T collectors producing both electricity and thermal energy and a 10 m³ water storage tank. The work includes the study of an industrial process heat system operated at two load supply temperatures of 60 °C and 80 °C. The results show that the electrical production of the system, employing polycrystalline solar cells, is more than the amorphous ones but the solar thermal contribution is slightly lower. A non-hybrid PV system produces about 25% more electrical energy but the present system covers also, depending on the location, a large percentage of the thermal energy requirement of the industry considered. The economic viability of the systems is proven, as positive life cycle savings are obtained in the case of hybrid systems and the savings are increased for higher load temperature applications. Additionally, although amorphous silicon panels are much less efficient than the polycrystalline ones, better economic figures are obtained due to their lower initial cost, i.e., they have better cost/benefit ratio.     

Technical and economic assessment of grid-independent hybrid photovoltaic–diesel–battery power systems for commercial loads in desert environments

Solar photovoltaic (PV) hybrid system technology is a hot topic for R&D since it promises lot of challenges and opportunities for developed and developing countries. The Kingdom of Saudi Arabia (KSA) being endowed with fairly high degree of solar radiation is a potential candidate for deployment of PV systems for power generation. Literature indicates that commercial/residential buildings in KSA consume an estimated 10–45% of the total electric energy generated. In the present study, solar radiation data of Dhahran (East-Coast, KSA) have been analyzed to assess the techno-economic viability of utilizing hybrid PV–diesel–battery power systems to meet the load requirements of a typical commercial building (with annual electrical energy demand of 620,000 kW h). The monthly average daily solar global radiation ranges from 3.61 to 7.96 kW h/m². NREL's HOMER software has been used to carry out the techno-economic viability. The simulation results indicate that for a hybrid system comprising of 80 kWp PV system together with 175 kW diesel system and a battery storage of 3 h of autonomy (equivalent to 3 h of average load), the PV penetration is 26%. The cost of generating energy (COE, US$/kW h) from the above hybrid system has been found to be 0.149 $/kW h (assuming diesel fuel price of 0.1 $/L). The study exhibits that for a given hybrid configuration, the operational hours of diesel generators decrease with increase in PV capacity. The investigation also examines the effect of PV/battery penetration on COE, operational hours of diesel gensets for a given hybrid system. Emphasis has also been placed on unmet load, excess electricity generation, percentage fuel savings and reduction in carbon emissions (for different scenarios such as PV–diesel without storage, PV–diesel with storage, as compared to diesel-only situation), cost of PV–diesel–battery systems, COE of different hybrid systems, etc.     

A sensitivity study of a hybrid photovoltaic/thermal water-heating system with natural circulation

A flat-box aluminum-alloy photovoltaic and water-heating system designed for natural circulation was constructed. The hybrid photovoltaic/thermal (PV/T) collector was an integration of single-crystalline silicon cells into a solar thermal collector. The product was able to generate electricity and hot water simultaneously. Outdoor tests on an improved prototype were conducted in a moderate climate zone. Then dynamic simulation runs, using a validated numerical model, were performed. These included sensitivity tests with variations of the system water mass, PV cell covering factor, and front glazing transmissivity. The test results showed that the characteristic daily primary-energy saving could reach up to 65% for this system with a PV cell covering factor 0.63 and front glazing transmissivity of 0.83, when the hot water load per unit heat-collecting area exceeded 80 kg/m². The simulated results indicated that the higher the PV cell covering factor and the glazing transmissivity, the better the overall system performance. The effects were quantified.     

Energy metrics of photovoltaic/thermal and earth air heat exchanger integrated greenhouse for different climatic conditions of India

In this paper, a study is carried out to evaluate the annual thermal and exergy performance of a photovoltaic/thermal (PV/T) and earth air heat exchanger (EAHE) system, integrated with a greenhouse, located at IIT Delhi, India, for different climatic conditions of Srinagar, Mumbai, Jodhpur, New Delhi and Bangalore. A comparison is made of various energy metrics, such as energy payback time (EPBT), electricity production factor (EPF) and life cycle conversion efficiency (LCCE) of the system by considering four weather conditions (a–d type) for five climatic zones. The embodied energy and annual energy outputs have been used for evaluation of the energy metrics. The annual overall thermal energy, annual electrical energy savings and annual exergy was found to be best for the climatic condition of Jodhpur at 29,156.8 kWh, 1185 kWh and 1366.4 kWh, respectively when compared with other weather stations covered in the study, due to higher solar intensity I and sunshine hours, and is lowest for Srinagar station. The results also showed that energy payback time for Jodhpur station is lowest at 16.7 years and highest for Srinagar station at 21.6 years. Electricity production factor (EPF) is highest for Jodhpur, i.e. 2.04 and Life cycle conversion efficiency (LCCE) is highest for Srinagar station. It is also observed that LCCE increases with increase in life cycle.     

Numerical analysis and optimization of a spectrum splitting concentration photovoltaic–thermoelectric hybrid system

This paper presents the numerical modeling and optimization of a spectrum splitting photovoltaic–thermoelectric (PV–TE) hybrid system. In this work, a simulation model is established in consideration of solar concentration levels and several heat dissipation rates. Exemplarily, the performance of a hybrid system composed of a GaAs solar cell and a skutterudites CoSb₃ solar thermoelectric generator (TEG) is simulated. Analysis under different conditions has been carried out to evaluate the electrical and thermal performance of the hybrid system. Results show that the cutoff-wavelength of the GaAs–CoSb₃ hybrid system is mainly determined by the band gap of solar cell, when the solar concentration ratio is ranged between 550 to 770 and heat transfer coefficient h = 3000–4500 W/m² K, the hybrid system has good electrical performance and low operating temperatures. Based on the analysis of the GaAs–CoSb₃ hybrid system, guidelines for the PV–TE system design are proposed. It is also compared with a PV-only system working under the same cooling condition; results show that the PV–TE hybrid system is more suitable for working under high concentrations.     

Performance enhancement of conventional combined cycle power plant by inlet air cooling,inter-cooling and LNG cold energy utilization

This paper has proposed an integrated advanced thermal power system to improve the performance of the conventional combined cycle power plant. Both inlet air cooling and inter-cooling are utilized within the proposed system to limit the decrease of the air mass flow contained in the given volume flow as well as reduce the compression power required. The latent heat of spent steam from a steam turbine and the heat extracted from the air during the compression process are used to heat liquefied natural gas (LNG) and generate electrical energy. The conventional combined cycle and the proposed power system are simulated using the commercial process simulation package IPSEpro. A parametric analysis has been performed for the proposed power system to evaluate the effects of several key factors on the performance. The results show that the net electrical efficiency and the overall work output of the proposed combined cycle can be increased by 2.8% and 76.8 MW above those of the conventional combined cycle while delivering 75.8 kg s^?1 of natural gas and saving 0.9 MW of electrical power by removing the need for sea water pumps used hitherto. Compared with the conventional combined cycle, the proposed power system performance has little sensitivity to ambient temperature changes and shows good off-design performance.     

An experimental study on using natural vaporization for cooling of a photovoltaic solar cell

This study attempts to investigate a new way for cooling PV cell using natural vapor as coolant. The performance of solar cell was examined on simulated sunlight. The natural vapor encountered backside of PV cell vertically in various distribution and different mass flow rates. Also, the effect of natural vapor temperature in cooling performance was analyzed. Results indicated that the temperature of PV cell drops significantly with increasing natural vapor mass flow rate. In detail, the PV cell temperature decreased about 7 to 16 °C when flow rate reaches 1.6 to 5 gr min^− 1. It causes increasing electrical efficiency about 12.12% to 22.9%. The best performance of PV cell can be achieved at high natural vapor flow rate, low natural vapor temperature and the obtained optimum distribution condition.     

Feasibility of pico-hydro and photovoltaic hybrid power systems for remote villages in Cameroon

Pico-hydro (pH) and photovoltaic (PV) hybrid systems incorporating a biogas generator have been simulated for remote villages in Cameroon using a load of 73 kWh/day and 8.3 kWp. Renewable energy systems were simulated using HOMER, the load profile of a hostel in Cameroon, the solar insolation of Garoua and the flow of river Mungo. For a 40% increase in the cost of imported power system components, the cost of energy was found to be either 0.352 €/kWh for a 5 kW pico-hydro generator with 72 kWh storage or 0.396 €/kWh for a 3 kWp photovoltaic generator with 36 kWh storage. These energy costs were obtained with a biomass resource cost of 25 €/tonne. The pH and PV hybrid systems both required the parallel operation of a 3.3 kW battery inverter with a 10 kW biogas generator. The pH/biogas/battery systems simulated for villages located in the south of Cameroon with a flow rate of at least 92 l/s produced lower energy costs than PV/biogas/battery systems simulated for villages in the north of Cameroon with an insolation level of at least 5.55 kWh/m²/day. For a single-wire grid extension cost of 5000 €/km, operation and maintenance costs of 125 €/yr/km and a grid power price of 0.1 €/kWh, the breakeven grid extension distances were found to be 12.9 km for pH/biogas/battery systems and 15.2 km for PV/biogas/battery systems respectively. Investments in biogas based renewable energy systems could thus be considered in the National Energy Action Plan of Cameroon for the supply of energy to key sectors involved in poverty alleviation.