Global analysis of the techno-economic potential of renewable energy hybrid systems on small islands

Globally, small islands below 100,000 inhabitants represent a large number of diesel based mini-grids. With volatile fossil fuel costs which are most likely to increase in the long-run and competitive renewable energy technologies the introduction of such sustainable power generation system seems a viable and environmental friendly option. Nevertheless the implementation of renewable energies on small islands is quite low based on high transaction costs and missing knowledge according to the market potential.Our work provides a global overview on the small island landscape showing the respective population, economic activity, energy demand, and fuel costs for almost 1800 islands with approximately 20 million inhabitants currently supplied by 15 GW of diesel plants. Based on these parameters a detailed techno-economic assessment of the potential integration of solar PV, wind power, and battery storage into the power supply system was performed for each island. The focus on solar and wind was set due to the lack of data on hydro and geothermal potential for a global island study. It revealed that almost 7.5 GW of photovoltaic and 14 GW of wind power could be economically installed and operated on these islands reducing the GHG-emissions and fuel consumption by approximately 50%. In total numbers more than 20 million tons of GHG emissions can be reduced by avoiding the burning of 7.8 billion liters of diesel per year. Cost savings of around 9 USDct/kWh occur on average by implementing these capacities combined with 5.8 GWh of battery storage. This detailed techno-economic evaluation of renewable energies enables policy makers and investors to facilitate the implementation of clean energy supply systems on small islands. To accelerate the implementation of this enormous potential we give specific policy recommendations such as the introduction of proper regulations.     

Optimizing a microgrid photovoltaic-fuel cell energy system at the highest renewable fraction

The current research examined the usage of fuel cells as an energy storage unit to increase renewable energy self-consumption in microgrid energy system applications. The studied model is comprised of photovoltaic modules and a fuel cell that serves as the energy storage unit. The study was conducted in 2020, utilizing real-time weather and electrical load data with a one-minute temporal resolution. The daily average energy consumption for the analyzed household was 10.1 kWh, with a peak power output of 5.3 kW, and the yearly energy consumption was 3755 kWh. The investigated photovoltaic system has a capacity of 2.7 kWp (6 modules at 0.45 kWp/module), and the fuel cell capacity is in the range of 0–3 kW in order to obtain optimal integration with the photovoltaic system to get maximum renewable energy fraction utilization. The findings indicate that using fuel cells powered by hydrogen generated by renewable energy systems can significantly increase self-consumption and self-sufficiency. The annual results showed that the use of 2.5 kW fuel cells can increase renewable fraction utilization from 0.622 to 0.918 with a 2.5 kW fuel cell, and energy self-consumption can reach 3338.2 kWh/year, an increase of 98.4%, and energy self-sufficiency can reach 3218.8 kWh/year, an increase of 94.41%. The results obtained demonstrate that the proposed photovoltaic fuel cell energy system provides a viable option to run semi-autonomous or fully autonomous applications in a self-sustaining medium at a percentage of 95%. Furthermore, the economic aspect is analysed for the optimal system configuration.     

Optimization of diesel engine performances for a hybrid wind–diesel system with compressed air energy storage

Electricity supply in remote areas around the world is mostly guaranteed by diesel generators. This relatively inefficient and expensive method is responsible for 1.2 million tons of greenhouse gas (GHG) emission in Canada annually. Some low- and high-penetration wind-diesel hybrid systems (WDS) have been experimented in order to reduce the diesel consumption. We explore the re-engineering of current diesel power plants with the introduction of high-penetration wind systems together with compressed air energy storage (CAES). This is a viable alternative to major the overall percentage of renewable energy and reduce the cost of electricity. In this paper, we present the operative principle of this hybrid system, its economic benefits and advantages and we finally propose a numerical model of each of its components. Moreover, we are demonstrating the energy efficiency of the system, particularly in terms of the increase of the engine performance and the reduction of its fuel consumption illustrated and supported by a village in northern Quebec.     

Analysis of the wind energy market in Denmark and future interactions with an emerging hydrogen market

The transition from fossil fuels to renewable energy sources is critical to reduce future emissions and mitigate the consequences hereof. Yet, the expansion of renewable energy, especially the highly fluctuating production of wind energy, poses economic challenges to the existing energy system in Denmark. This paper investigates the economic feasibility of integrating a 250 kW, 500 kW, 750 kW and 1 MW water electrolysis system in the existing Danish energy market to exploit excessive off- and onshore wind energy for hydrogen production used as fuel for transportation purposes. In 2018, Danish wind turbines produced excess energy during 1238 h, which poses a capacity constraint as the electrolysis systems are limited to only produce hydrogen for 14% of the total available annual hours. This paper concludes that the net present value of each investment is negative as the fixed and variable production costs exceeds the generated revenues and it is therefore not economical feasible to invest in an electrolysis system with the purpose of only operating whenever excess off- and onshore wind energy is available.     

Performance of single‐ and double‐effect operable mechanical vapor recompression desalination system adaptable to variable wind energy

This paper deals with the development and operation of a mechanical vapor recompression (MVR) desalination system with improved energy efficiency in harnessing wind energy, which is non‐dispatchable. Its design, construction, and operation details are presented in this paper. Especially, the main focus of developing the system was on the operation of the system in conjunction with variable loads of new and renewable power sources, in particular, varying wind power. That is, the present work has been carried out to assess the feasibility of its operation in light of capacity modulation to match the power generated under various wind speeds. Optimal operation modes of the system were studied, in which single‐ and double‐effect operations were analyzed for their improvement in energy efficiency. The compression ratio of the proposed MVR system was 1.55 at an inverter speed of 55 Hz, which agreed well with its design value. Operation of the main heat exchanger remained stable within the limits of its operable range, although the temperature differences in the main heat exchanger did not remain constant because of the pressure variations in the evaporator. The daily freshwater yield was between 28 and 51 tons. The power consumption per ton of freshwater produced was about 43 kW for a single effect and about 23 kW for a double effect, which is about twice as efficient.     

Triple hybrid system coupling fuel cell with wind turbine and thermal solar system

One of the most challenging issues in the domain of renewable energy is the instability of produced power. To put it another way, renewable resources such as solar energy cannot provide continuous energy supply because they rely on natural phenomena that vary randomly. That said, to cover the potential lack of energy that may occur, hybrid renewable energy system can be adopted. In other terms, instead of using single renewable energy source, two different sources can be utilized in order to optimize the output power all over the year. Furthermore, complementary energy system is needed along with renewable sources, to store energy and insure the supply during shortage period. With this in mind, a Green-Green energy system can be constructed by using green storage system such as Fuel Cell to be coupled with the renewable sources. In the light of green-green energy concept, the present paper examines a triple wind-solar-fuel cell combination in the aim of overcoming the energy shortage that occurs during several months of the year. A case study on the region of Dahr Al-Baidar in Lebanon is conducted to present the advantage of the proposed system. Results show that combining wind energy system with thermal solar system allows overcoming the low power produced by solar thermal system especially in winter. For illustration 16 kW are produced by wind turbine during the month of January, by contrast the thermal solar system provides 2 kW during the same period. Nevertheless, in June thermal solar offers 17 kW and wind turbine produces 11 kW.     

Evaluation of electricity generation and energy cost of wind energy conversion systems (WECSs) in Central Turkey

The negative effects of non-renewable fossil fuels have forced scientists to draw attention to clean energy sources which are both environmentally more suitable and renewable. Although Turkey enjoys fairly high wind energy potential, an investigation and exploitation of this source is still below the desired level. In this study which is a preliminary study on wind energy cost in Central Anatolian-Turkey, the wind energy production using time-series approach and the economic evaluation of various wind energy conversion systems (WECSs) enjoying the 2.5, 5, 10, 20, 30, 50, 100 and 150 kW rated power size using the levelised cost of electricity (LCOE) method for the seven different locations in Central Turkey were estimated. In addition, effects of escalation ratio of operation and maintenance cost and annual mean speed on LCOE are taken into account. The wind speed data for a period between 2000 and 2006 years were taken from Turkish State Meteorological Service (TSMS). According to the result of the calculations, it is shown that the WECS of capacity 150 kW produce the energy output 120,978 kWh per year in the Case-A (Pinarbasi) for hub height 30 m and also the LCOE varies in the range of 0.29–30.0 $/kWh for all WECS considered.     

The feasibility of renewable energies at an off-grid community in Canada

Three renewable energy technologies (RETs) were analyzed for their feasibility for a small off-grid research facility dependent on diesel for power and propane for heat. Presently, the electrical load for this facility is 115 kW but a demand side management (DSM) energy audit revealed that 15–20% reduction was possible. Downsizing RETs and diesel engines by 15 kW to 100 kW reduces capital costs by $27 000 for biomass, $49 500 for wind and $136 500 for solar.The RET Screen International 4.0^® model compared the economical and environmental costs of generating 100 kW of electricity for three RETs compared to the current diesel engine (0 cost) and a replacement ($160/kW) diesel equipment. At all costs from $0.80 to $2.00/l, biomass combined heat and power (CHP) was the most competitive. At $0.80 per liter, biomass’ payback period was 4.1 years with a capital cost of $1800/kW compared to wind's 6.1 years due to its higher initial cost of $3300/kW and solar's 13.5 years due to its high initial cost of $9100/kW. A biomass system would reduce annual energy costs by $63 729 per year, and mitigate GHG emissions by over 98% to 10 t CO₂ from 507 t CO₂. Diesel price increases to $1.20 or $2.00/l will decrease the payback period in years dramatically to 1.8 and 0.9 for CHP, 3.6 and 1.8 for wind, and 6.7 and 3.2 years for solar, respectively.     

Pre-feasibility study of stand-alone hybrid energy systems for applications in Newfoundland

A potential solution for stand-alone power generation is to use a hybrid energy system in parallel with some hydrogen energy storage. In this paper, a pre-feasibility study of using hybrid energy systems with hydrogen as an energy carrier for applications in Newfoundland, Canada is explained. Various renewable and non-renewable energy sources, energy storage methods and their applicability in terms of cost and performance are discussed. HOMER is used as a sizing and optimization tool. Sensitivity analysis with wind speed data, solar radiation level, diesel price and fuel cell cost was done. A remote house having an energy consumption of 25 kW h/d with a 4.73 kW peak power demand was considered as the stand-alone load. It was found that, a wind–diesel–battery hybrid system is the most suitable solution at present. However, with a reduction of fuel cell cost to 15% of its current value, a wind–fuel cell system would become a superior choice. Validity of such projection and economics against conventional power sources were identified. Sizing, performance and various cost indices were also analyzed in this paper.     

Size optimization of a hybrid photovoltaic/fuel cell grid connected power system including hydrogen storage

This paper describes the size optimization of a hybrid photovoltaic/fuel cell grid linked power system including hydrogen storage. The overall objective is the optimal sizing of a hybrid power system to satisfy the load demand of a university laboratory with an unreliable grid, with low energy cost and minimal carbon emissions. The aim is to shift from grid linked diesel power system to a clean and sustainable energy system. The optimum design architecture was established by adopting the energy-balance methods of HOMER (hybrid optimization model for electric renewables). Analysis of hourly simulations was performed to decide the optimal size, cost and performance of the hybrid system, using 22-years monthly averaged solar radiation data collected for Ambrose Alli University, Ekpoma (Lat. 6°44.3ʹN, Long. 6°4.8ʹE). The results showed that a hybrid system comprising 54.7 kW photovoltaic array, 7 kW fuel cell system, 14 kW power inverter and 3 kW electrolyzer with 8 kg hydrogen storage tank can sustainably augment the erratic grid with a very high renewable fraction of 96.7% at $0.0418/kWh. When compared with the conventional usage of grid/diesel generator system; energy cost saving of more than 88% and a return on investment of 41.3% with present worth of $308,965 can be derived in less than 3 years. The application of the optimally sized hybrid system would possibly help mitigate the rural-to-urban drift and resolve the electricity problems hindering the economic growth in Nigeria. Moreover, the hybrid system can alleviate CO₂ emissions from other power generation sources to make the environment cleaner and more eco-friendly.     

Rural electrification of a remote island by renewable energy sources

India has a large number of remote small villages and islands that lack in the electricity, and probability of connecting them with the high voltage gridlines in the near future is very poor due to financial and technical constraints. The main electrical load in these villages is domestic. In this paper a study has been presented for sustainable development of renewable energy sources to fulfill the energy demands of a remote island having a cluster of five villages. The total potential of electricity from these resources is estimated to be equivalent to 3530 kWh/day whereas demand is only 2310 kWh/day with an installed capacity of 450 kW, which is sufficient to replace the existing power generation system dominated by diesel operated system.     

Renewable energy systems based on hydrogen for remote applications

An integrated renewable energy (RE) system for powering remote communication stations and based on hydrogen is described. The system is based on the production of hydrogen by electrolysis whereby the electricity is generated by a 10 kW wind turbine (WT) and 1 kW photovoltaic (PV) array. When available, the excess power from the RE sources is used to produce and store hydrogen. When not enough energy is produced from the RE sources, the electricity is then regenerated from the stored hydrogen via a 5 kW proton exchange membrane fuel cell system. Overview results on the performances of the WT, PV, and fuel cells system are presented.     

Feasibility study of hybrid retrofits to an isolated off-grid diesel power plant

The green sources of energy are being encouraged to reduce the environmental pollution and combat the global warming of the planet. A target of 12% usage of wind energy only has been agreed by the UNO country members to achieve by 2020. So, the power of the wind is being used to generate electricity both as grid connected and isolated wind-diesel hybrid power plants. This paper performed a pre-feasibility of wind penetration into an existing diesel plant of a village in north eastern part of Saudi Arabia. For simulation purpose, wind speed data from a near by airport and the load data from the village have been used. The hybrid system design tool HOMER has been used to perform the feasibility study. In the present scenario, for wind speed less than 6.0 m/s the, the existing diesel power plant is the only feasible solution over the range of fuel prices used in the simulation. The wind diesel hybrid system becomes feasible at a wind speed of 6.0 m/s or more and a fuel price of 0.1 $/L or more. If the carbon tax is taken into consideration and subsidy is abolished then it is expected that the hybrid system become feasible. The maximum annual capacity shortage did not have any effect on the cost of energy which may be accounted for larger sizes of wind machines and diesel generators. It is recommended that the wind data must be collected at the village at three different heights using a wind mast of 40 m for a minimum of one complete year and then the hybrid system must be re-designed.     

The utility of energy storage to improve the economics of wind–diesel power plants in Canada

Wind energy systems have been considered for Canada's remote communities in order to reduce their costs and dependence on diesel fuel to generate electricity. Given the high capital costs, low-penetration wind–diesel systems have been typically found not to be economic. High-penetration wind–diesel systems have the benefit of increased economies of scale, and displacing significant amounts of diesel fuel, but have the disadvantage of not being able to capture all of the electricity that is generated when the wind turbines operate at rated capacity.Two representative models of typical remote Canadian communities were created using HOMER, an NREL micro-power simulator to model how a generic energy storage system could help improve the economics of a high-penetration wind–diesel system. Key variables that affect the optimum system are average annual wind speed, cost of diesel fuel, installed cost of storage and a storage systems overall efficiency. At an avoided cost of diesel fuel of 0.30 $Cdn/kWh and current installed costs, wind generators are suitable in remote Canadian communities only when an average annual wind speed of at least 6.0 m/s is present. Wind energy storage systems become viable to consider when average annual wind speeds approach 7.0 m/s, if the installed cost of the storage system is less than 1000 $Cdn/kW and it is capable of achieving at least a 75% overall energy conversion efficiency. In such cases, energy storage system can enable an additional 50% of electricity from wind turbines to be delivered.     

Optimal configuration of power generating systems in isolated island with renewable energy

In isolated islands, usually diesel generators supply electric power. However, there are problems, e.g., a lack of fossil fuel, environmental pollution etc. So, isolated island, e.g. Miyako island, installs renewable energy power production plants. However, renewable energy power production plants are very costly. This paper presents an optimal configuration of power system in isolated island installing renewable energy power production plants. The generating system consists of diesel generators, wind turbine generators, PV system and batteries. Using the proposed method, operation cost can be reduced about 10% in comparison with diesel generators only from simulation results.     

Renewable energy resources as an alternative to modify the load curve in Northern Cyprus

The average annual increase in electricity consumption and peak demand in Northern Cyprus (N. Cyprus) during the past 20 years have been 7.1 and 5.5%, respectively. In recent years, the demand for electricity has been stretched to its limits in winter. This raised the question of whether renewable energy resources could be utilized to reduce the level of peak demand. Indeed, Cyprus being a Mediterranean island, enjoys an abundance of solar energy, and preliminary studies showed that a considerable potential of wind energy is also available. Utilization of renewable energy for space heating, water heating, pumping and power generation would increase electrical reserve margins, raise system load factor, improve load following capabilities, and reduce the need for capacity expansion. Currently, solar water heating which leads to a saving of at least 72 GWh energy per annum and a significant reduction in CO₂ emission has been extensively used in N. Cyprus. In N. Cyprus, despite the availability of renewable energy resources constructing renewable base-load, electrical power stations has not been found feasible. However, constructing such systems is recommended for two reasons: firstly, as a supplement to saving fuel and secondly, expanding capacity. In this context, the economic analysis for both solar and wind energy systems, has shown a reasonable internal rate of return (IRR). Although, the IRR is higher for wind energy systems, the availability of wind is limited to a few locations and therefore energy distribution is required.     

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.     

Optimisation of solar-hydrogen power system for household applications

A numerical method was developed for optimising solar–hydrogen energy system to supply renewable energy for typical household connected with the grid. The considered case study involved household located in Diyala Governorate, Iraq. The solar–hydrogen energy system was designed to meet the desired electrical load and increase the renewable energy fraction using optimum fuel cell capacity. The simulation process was conducted by MATLAB based on the experimental data for electrical load, solar radiation and ambient temperature at a 1-min time-step resolution. Results demonstrated that the optimum fuel cell capacity was approximately 2.25 kW at 1.8 kW photovoltaic power system based on the average of the daily energy consumption of 6.8 kWh. The yearly renewable energy fraction increased from 31.82% to 95.82% due to the integration of the photovoltaic system with a 2.25 kW fuel cell used as a robust energy storage unit. In addition, the energy supply, which is the economic aspect for the optimum system, levelised electricity cost by approximately $0.195/kWh. The obtained results showed that the proposed numerical analysis methodology offers a distinctive property that can be used effectively to optimise hybrid renewable energy systems.     

A mobile off-grid platform powered with photovoltaic/wind/battery/fuel cell hybrid power systems

Cross utilization of photovoltaic/wind/battery/fuel cell hybrid-power-system has been demonstrated to power an off-grid mobile living space. This concept shows that different renewable energy sources can be used simultaneously to power off-grid applications together with battery and hydrogen energy storage options. Photovoltaic (PV) and wind energy are used as primary sources and a fuel cell is used as backup power. A total of 2.7 kW energy production (wind and PV panels) along with 1.2 kW fuel cell power is supported with 17.2 kWh battery and 15 kWh hydrogen storage capacities. Supply/demand scenarios are prepared based on wind and solar data for Istanbul. Primary energy sources supply load and charge batteries. When there is energy excess, it is used to electrolyse water for hydrogen production, which in turn can either be used to power fuel cells or burnt as fuel by the hydrogen cooker. Power-to-gas and gas-to-power schemes are effectively utilized and shown in this study. Power demand by the installed equipment is supplied by batteries if no renewable energy is available. If there is high demand beyond battery capacity, fuel cell supplies energy in parallel. Automatic and manual controllable hydraulic systems are designed and installed to increase the photovoltaic efficiency by vertical axis control, to lift up & down wind turbine and to prevent vibrations on vehicle. Automatic control, data acquisition, monitoring, telemetry hardware and software are established. In order to increase public awareness of renewable energy sources and its applications, system has been demonstrated in various exhibitions, conferences, energy forums, universities, governmental and nongovernmental organizations in Turkey, Austria, United Arab Emirates and Romania.     

Economic analysis and optimal design of hydrogen/diesel backup system to improve energy hubs providing the demands of sport complexes

Energy crisis has led the communities around the world to use energy hubs. These energy hubs usually consist of photovoltics, wind turbines and batteries. Diesel generators are usually used in these systems as backup system. In this research, for the first time, an attempt is made to replace the traditional diesel only backup system with hydrogen only system and combined hydrogen and diesel backup system in hybrid photovoltaic and wind turbine energy systems. After introducing the available energy modeling tools and methods, explaining over advantages and disadvantages of each one, HOMER software was selected for this research. The simulations of this research show that using the traditional diesel generator as the backup system of the energy hub, creates a low cost system with the net present cost (NPC) of 2.5 M$ but also produces the highest amount carbon emission which is equal to 686 tons/year. The results of this study also indicate the hybrid renewable energy system which is supported by the hydrogen only backup system has the highest net present cost (NPC) and initial capital cost but reduces the maximum amount of carbon. The calculated NPC and carbon production of the energy hub using hydrogen only backup system are equal to 4.39 M$ and 55,205, respectively. On the other hand, the combined hydrogen/diesel backup system has reduced NPC compared with the hydrogen only backup system. The CO₂ production of this system is also lower than the diesel only backup system. The calculations indicate that the NPC and CO₂ production of the combined backup system are 3.53 M$ and 511,695 kg/yr. By comparing advantages and disadvantages of all 3 scenarios, the micro grid which uses the combined diesel/hydrogen backup system is selected as the most optimal system. The sensitivity analysis of the selected system shows that fluctuations of inflation rate along with the fluctuations of both fuel cells and electrolyzers capital cost do not affect the net present cost (NPC) considerably. On the other hand, fluctuations of capital cost of the main components like wind turbines affect the NPC much more than the others. If the inflation rate drops from 15% to 14% and wind turbine capital cost multiplier reduces from 1 to 0.8, the NPC value will drop by the value of 300,000 $.