Sizing and modelling of photovoltaic water pumping system

With the decline in price of the photovoltaics (PVs) their use as a power source for water pumping is the most attractive solution instead of using diesel generators or electric motors driven by a grid system. In this paper, a method to design a PV pumping system is presented and discussed, which is then used to calculate the required size of the PV for an existing farm. Furthermore, the amount of carbon dioxide emissions saved by the use of PV water pumping system instead of using diesel-fuelled generators or electrical motor connected to the grid network is calculated. In addition, an experimental set-up is developed for the PV water pumping system using both DC and AC motors with batteries. The experimental tests are used to validate the developed MATLAB model. This research work demonstrates that using the PV water pumping system is not only improving the living conditions in rural areas but it is also protecting the environment and can be a cost-effective application in remote locations.     

Techno-economic analysis and modelling of a remote photovoltaic water pumping system in the desert of Tunisia

For estimating the performance of a photovoltaic (PV) water pumping system without battery storage, a simple algorithm has been developed. This simulation program uses the hourly global solar radiation, the hourly ambient temperature and the hourly wind speed as the input, moreover the characteristics of region (latitude, longitude, ground albedo) and characteristics of PV water pumping system (orientation, inclination, nominal PV module efficiency, NOCT, PV array area, PV temperature coefficient, miscellaneous power conditioning losses, miscellaneous PV array losses, temperature of reference, moto-pump efficiency and inverter efficiency). This work allows evaluating the economic interest of a remote PV water pumping systems in the desert of Southern Tunisia, which will have to satisfy an average daily volume of 45 m³ throughout the year compared to another very widespread energy system in the area, the diesel genset (DG), by using the method of the life-cycle cost (LCC). The cost per m³ of water was calculated for this system. It is found that the LCC for PV system is 0.500 TND/m³ and the LCC DG is 0.837 TND/m³. The present study indicates economic viability of PV water pumping systems in the desert of Tunisia.     

Rural area power supply in Nigeria: A cost comparison of the photovoltaic, diesel/gasoline generator and grid utility options

A large proportion of the population of Nigeria reside in the rural communities. In this work, the financial costs of providing centralized (photovoltaic) PV generating system of various capacities—to satisfy different load requirements—in a remote village in Nigeria is compared with the cost of grid extension over a distance of 1.8 km. Comparison is also made with the centralised diesel generator power supply option. In addition, the costs of decentralised PV home systems are compared with those of decentralised gasoline generator systems. For all the systems, the initial capital costs and the life cycle costs over a 20-year life cycle are reported. Sensitivity analysis was performed using variations in module costs, diesel fuel prices and grid extension distance. The results suggest that PV has a remarkable potential as a cost-effective option for low-power electrical energy supply to the rural communities in the country.     

Experience with a surface floating PV pumping system: A case study in Khartoum

In a country like Sudan, where the power grid extension is limited to a small area, and fuel shortages and road inaccessibility cause major problems in providing the basic energy needs to rural areas, small scale PV systems could be a comparable application against diesel driven units. One of the main needs is water pumping for drinking, as well as irrigation purposes, so PV power pumping systems could be one of the solutions to the growing energy demand in rural areas. Such systems should ensure high reliability and low/no maintenance cost, otherwise they cannot compete with conventional systems, even in the long term. Therefore, the investigation of the field behaviour of new products is essential to characterize such designs under prevailing conditions. In this paper, a surface floating PV pumping system's performance and its technical feasibility under Khartoum's climatic conditions are investigated. Technical problems encountered with the operation of this system are clearly defined, and suggestions for design modification are advanced.     

太阳能光伏水泵和照明综合应用系统

本文介绍光伏水泵和照明综合应用系统,以及光伏水泵系统的发展情况。利用太阳能光伏水泵系统解决无电地区农牧民人蓄饮水、农田灌溉问题是一条经济可行的途径。光伏水泵系统具有广阔的推广应用前景。     

Optimum design of a photovoltaic powered pumping system

Photovoltaic (PV) powered pumping systems are relatively simple and reliable, hence they are applied worldwide. Two conventional techniques are curently in use; the first is the directly coupled technique where a PV array is directly coupled to a d.c. motor-pump group, and the second is the battery buffered PV pumping system where a battery is connected across the array to feed the d.c. motor driving a pump. Recently, a third system is proposed to make use of the advantages of the previously mentioned conventional systems. It is the switched mode PV powered pumping system.

The switched mode PV powered pumping system couples the pumping system to the PV array directly when the storage battery is fully charged as explained in Ref. [5]. The objective of such a system is the maximum utilization of available solar radiation to minimize the cost per pumped cubic meter from a given water depth. For a given location, four main parameters affect the design of this system; (1) d.c. motor-pump group parameters, (2) PV array size, (3) battery storage size and (4) water storage tank size. The system designer has to determine the previously mentioned four parameters so that the minimum cost per pumped cubic meter is achieved. It is found that some factors are more effective in reducing the cost than others. The PV array size is the predominant factor, while the battery storage and water tank sizes have relatively less effect. The system installation cost is considered in the detailed economic analysis discussed in this work.     

Performance of submersible PV solar pumping systems under conditions in the Sudan

Water pumping for domestic use and irrigation purposes can be considered as one of the basic needs in the rural areas of Sudan. For the favourable solar radiation conditions in the country (6 kW h/m²/day), solar water pumping may be a competitive application against diesel-driven pumps for remote areas.Three SP4–8 Grundfos submersible pumps, installed at three different locations in the country, were evaluated. Two of these pumps were driven by M-51 Arco Solar modules, while the third was driven by M-53 Arco Solar modules. For each of these pumps, solar radiation in the plane of the PV array, ambient temperature, PV array voltage and current, water discharge and water delivery pressure were monitored using a data logger.Grundfos solar pumps used in the Sudan have proven in most cases to be reliable. However, their performance was 10–25% less than predicted by the manufacturer's literature. In general the product of the daily water demand (m³ per day) and the total pumping head (m) should not exceed 750 m⁴ for sites with good solar radiation.     

Optimizing rainwater harvesting systems as an innovative approach to saving energy in hilly communities

Rapid urbanization is increasing the amount of hilly communities around many large cities; therefore, saving water pumping energy deserves significant priority. This work proposes optimized rooftop rainwater harvesting systems (RRWHSs) and provides an energy-saving approach for hilly communities. The most cost-effective rainwater tank volumes for different dwelling types are calculated using marginal analysis. The case study at Hua-Chan Community in northern Taiwan indicates that the optimum rainwater tank volumes range from 5 m³ to 10 m³ according to the type of dwelling. The results also reveal that rainwater harvesting becomes economically feasible when both energy and water savings are addressed together. Furthermore, the cost of unit energy saving from RRWHSs is lower than that from solar PV systems. Hence, RRWHSs provide not only water savings, but also as an alternative renewable energy-saving approach to address the water–energy dilemma caused by the ever-growing hilly communities.     

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.     

Economic viability of photovoltaic water pumping systems

A comparison of the economic viability of photovoltaic and diesel water pumping systems is presented for system sizes in the range 2.8 kW_p to 15 kW_p. Actual performance data from installed systems are employed for the base case. Sensitivity analysis is carried out to generalize results for other locations and conditions. The effect of system oversizing due to mismatch of water supply and demand patterns on the economic viability of PV water pumping system is illustrated based on real data and three-year operational experience of eight installations. Investment prospects in PV water pumping applications for different selling price scenarios of water have been investigated.     

Potential improvement to a citric wastewater treatment plant using bio-hydrogen and a hybrid energy system

Treatment of highly concentrated organic wastewater is characterized as cost-consuming. The conventional technology uses the anaerobic-anoxic-oxic process (A²/O), which does not produce hydrogen. There is potential for energy saving using hydrogen utilization associated with wastewater treatment because hydrogen can be produced from organic wastewater using anaerobic fermentation. A 50 m³ pilot bio-reactor for hydrogen production was constructed in Shandong Province, China in 2006 but to date the hydrogen produced has not been utilized. In this work, a technical-economic model based on hydrogen utilization is presented and analyzed to estimate the potential improvement to a citric wastewater plant. The model assesses the size, capital cost, annual cost, system efficiency and electricity cost under different configurations. In a stand-alone situation, the power production from hydrogen is not sufficient for the required load, thus a photovoltaic array (PV) is employed as the power supply. The simulated results show that the combination of solar and bio-hydrogen has a much higher cost compared with the A²/O process. When the grid is connected, the system cost achieved is 0.238 US$ t⁻¹ wastewater, which is lower than 0.257 US$ t⁻¹ by the A²/O process. The results reveal that a simulated improvement by using bio-hydrogen and a FC system is effective and feasible for the citric wastewater plant, even when compared to the current cost of the A²/O process. In addition, lead acid and vanadium flow batteries were compared for energy storage service. The results show that a vanadium battery has lower cost and higher efficiency due to its long lifespan and energy efficiency. Additionally, the cost distribution of components shows that the PV dominates the cost in the stand-alone situation, while the bio-reactor is the main cost component in the parallel grid.     

The Oxford Solar House

This paper presents preliminary results from the first nine months of monitoring the Oxford Solar House (OSH) which was built, in particular, to evaluate the potential for photovoltaics to contribute cost effectively to domestic energy supply in the UK. The house was built in a south facing site with good solar access. It has a 4kW PV system integrated into the roof structure and a 5m² solar thermal domestic hot water pre-heat. The house was designed to require a minimum of energy for heating, cooling and lighting, therefore optimizing the significance of the contribution of the solar electric supply. The performance of the PV system is presented, as well as an analysis of the whole design strategy to minimize energy loads.     

Off-grid hybrid renewable energy system with hydrogen storage for South African rural community health clinic

Most inhabitants of rural communities in Africa lack access to clean and reliable electricity. This has deprived the rural dwellers access to modern healthcare delivery. In this paper, an off-grid renewable energy system consisting of solar PV and wind turbine with hydrogen storage scheme has been explored to meet the electrical energy demands of a health clinic. The health clinic proposed is a group II with 10 beds located in a typical village in South Africa. First, the wind and solar energy resources of the village were analysed. Thereafter, the microgrid architecture that would meet the energy demand of the clinic (18.67 kWh/day) was determined. Some of the key results reveal that the average annual wind speed at 60 m anemometer height and solar irradiation of the village are 7.9 m/s and 4.779 kWh/m²/day, respectively. The required architecture for the clinic composes of 40 kW solar PV system, 3 numbers of 10 kW wind turbines, 8.6 kW fuel cell, 25 kW electrolyser and 40 kg hydrogen tank capacity. The capital cost of the microgrid was found to be $177,600 with a net present cost of $206,323. The levelised cost of energy of the system was determined to be 2.34 $/kWh. The project has a breakeven grid extension distance of 8.81 km. Since this distance is less than the nearest grid extension distance of 21.35 km, it is established that the proposed renewable energy microgrid with a hydrogen storage system is a viable option for the rural community health clinic.     

Performance evaluation of a.c. and d.c. direct coupled photovoltaic water pumping systems

Photovoltaic (PV) water pumping systems have been widely tested and assessed in Indonesia because of the deficiency of potable water in remote areas. Several different PV water pumping systems, such as a.c./d.c. with/without battery and various pumps, have been tested in the field. Further study, evaluation and classification of optimized PV water pumping systems is needed. Three of those pumping systems were installed in Sumba Island in 1983, in three adjacent villages with similar climate and environment conditions. Two of the installations had a.c. direct coupled systems and the other had d.c. The a.c. systems used a 3.65 kW_p PV generator each and the d.c. system used 5.76 kW_p. After comparing the performance data of both systems, it can be concluded that the a.c. system performs better and needs less maintenance on the pump. In May 1987, as a result of this evaluation, the 5.76 kW_p d.c. system was replaced by an a.c. one, and its capacity was increased to 9.22 kW_p. Meanwhile, the 3.65 kW_p a.c. system was increased to 3.88 kW_p.     

Techno-economic feasibility of photovoltaic,wind, diesel and hybrid electrification systems for off-grid rural electrification in Colombia

Electrification to rural and remote areas with limited or no access to grid connection is one of the most challenging issues in developing countries like Colombia. Due to the recent concerns about the global climatic change and diminishing fuel prices, searching for reliable, environmental friendly and renewable energy sources to satisfy the rising electrical energy demand has become vital. This study aims at analyzing the application of photovoltaic (PV) panels, wind turbines and diesel generators in a stand-alone hybrid power generation system for rural electrification in three off-grid villages in Colombia with different climatic characteristics. The areas have been selected according to the “Colombia’s development plan 2011–2030 for non-conventional sources of energy”. First, different combinations of wind turbine, PV, and diesel generator are modeled and optimized to determine the most energy-efficient and cost-effective configuration for each location. HOMER software has been used to perform a techno-economic feasibility of the proposed hybrid systems, taking into account net present cost, initial capital cost, and cost of energy as economic indicators.     

Design optimization of grid-connected PV-Hydrogen for energy prosumers considering sector-coupling paradigm: Case study of a university building in Algeria

Integrating sector coupling technologies into Hydrogen (H₂) based hybrid renewable energy systems (HRES) is becoming a promising way to create energy prosumers, despite the very little research work being done in this largely unexplored field. In this paper, a sector coupling strategy (building and transportation) is developed and applied to a grid-connected PV/battery/H₂ HRES, to maximise self-sufficiency for a University campus and to produce power and H₂ for driving electric tram in Ouargla, Algeria. A multi-objective size optimization problem is solved as a single objective problem using the ε-constraint method, in which the cost of energy (COE) is defined as the main objective function to be minimized, while both loss of power supply probability (LPSP) and non-renewable usage (NRU) are defined as constraints. Particle swarm optimization and HOMER software are then employed for simulation and optimization purposes. Prior to the two scenarios investigated, a sensitivity study is performed to determine the effects of H₂ demand by tram and NRU on the techno-economic feasibility of the proposed system, followed by a new reliability factor introduced in the optimization, namely loss of H₂ supply probability (LHSP). The results of the first scenario show that by setting NRU^max = 100%, the system without H₂ provides the best solution with COE of 0.016 $/kWh that reaches grid parity and has 13% NRU. However, by setting NRU^max = 1% in the second scenario, an optimized configuration consisting of grid/PV/Electrolyzer/Fuel cell/Storage tank is obtained, which has 0% NRU and COE of 0.1 $/kWh. In the second scenario, it is also observed that an increased number of trams (i.e. increased H₂ demands) causes a significant reduction in LHSP, COE, NRU and CO₂ emissions. It is thus concluded that the grid/PV combination is the optimal choice for the studied system when considering economic aspects. However, taking into account the growing requirements of future energy systems, grid-connected PV with H₂ will be the best solution.     

Assessment and evaluation of PV based decentralized rural electrification: An overview

The challenges of providing electricity to rural households are manifold. Ever increasing demand–supply gap, crumbling electricity transmission and distribution infrastructure, high cost of delivered electricity are a few of these. Use of renewable energy technologies for meeting basic energy needs of rural communities has been promoted by the Governments world over for many decades. Photovoltaic (PV) technology is one of the first among several renewable energy technologies that was adopted globally as well as in India for meeting basic electricity needs of rural areas that are not connected to the grid. This paper attempts at reviewing and analyzing PV literature pertaining to decentralized rural electrification into two main categories—(1) experiences from rural electrification and technology demonstration programmes covering barriers and challenges in marketing and dissemination; institutional and financing approaches; and productive and economic applications, (2) techno-economic aspects including system design methodologies and approaches; performance evaluation and monitoring; techno-economic comparison of various systems; and environmental implications and life cycle analysis. The paper discusses the emerging trends in its concluding remarks.     

Electrification using solar photovoltaic systems in Nepal

Historically, the rural population of Nepal has been meeting their energy needs from traditional sources like fuel wood and other biomass resources. Only about 44% of the total population has access to grid electricity. Because of country’s rough and mountainous topography, high cost of grid extension, and low and scattered population density, constructing some big power plants (e.g. large hydropower) can not meet the electricity needs of all people, especially those living in rural areas. Distributed generation of electricity, using environment friendly solar photovoltaic (PV) systems, might be one of the reliable alternatives for urban as well as rural electrification. This article begins with a general overview of energy resources in Nepal. Present status and perspectives of solar PV sector have also been discussed. Benefit cost and breakeven analyses of solar PV systems in Nepalese urban areas have been carried out. The breakeven year has been calculated between 2027 and 2036 for PV systems with system life time between 40 and 25 years, respectively. It has been concluded that the solar PV systems are not the economic solutions for grid connected urban areas in Nepal. On the other hand, this article concludes that the rural electrification projects should not be decided on the basis of mere monetary benefits, rather many social aspects should be considered, and in this case, there are not convincing alternatives to solar PV systems for electrification in many rural villages in Nepal.     

Direct coupling of an electrolyser to a solar PV system for generating hydrogen

Hydrogen as an energy currency, carrier and storage medium may be a key component of the solution to problems of global warming, poor air quality and dwindling reserves of liquid hydrocarbon fuels. Hydrogen is a flexible storage medium and can be generated by the electrolysis of water. It is particularly advantageous if an electrolyser may be simply and efficiently coupled to a source of renewable electrical energy. This paper examines direct coupling of a polymer electrolyte membrane (PEM) electrolyser to a matched solar photovoltaic (PV) source for hydrogen generation and storage. Such direct coupling with minimum interfacing electronics would lead to substantial cost reduction and thereby enhance the economic viability of solar-hydrogen systems. The electrolyser is designed for fail-safe operation with multiple levels of safety and operational redundancy. A control system in the electrolyser unit provides for disconnection when required and for auto-start in the morning and auto shut-down at night, simultaneously addressing the goals of minimum energy loss and maximum safety. The PV system is a 2.4 kW array (20.4 m² total area) comprising 30, 12 V, 80 W, Solarex polycrystalline modules in a series–parallel configuration. The integrated system has been operated for approximately 60 days over a 4-month period from September 2007 to January 2008 with many periods of unattended operation for multiple days, experiencing weather ranging from hot and sunny (above 40 °C) to cool and cloudy. The principle and practicality of direct coupling of a suitably matched PV array and PEM electrolyser have been successfully demonstrated. Details of electrolyser operation coupled to a PV array along with modelling work to match current–voltage characteristics of the electrolyser and PV system are described.     

Hydrokinetic power generation for rural electricity supply: Case of South Africa

This study investigates the possibility of using and developing hydrokinetic power to supply reliable, affordable and sustainable electricity to rural, remote and isolated loads in rural South Africa where reasonable water resource is available. Simulations are performed using the Hybrid Optimization Model for Electric Renewable (HOMER) and the results are compared to those from other supply options such as standalone Photovoltaic system (PV), wind, diesel generator (DG) and grid extension. Finally the paper points out some major challenges that are facing the development of this technology in South Africa.