Evaluation of optimal power options for base transceiver stations of Mobile Telephone Networks Cameroon

Photovoltaic hybrid systems (PVHS) with 2 days of energy autonomy are shown to be optimal options for the supply of the daily energy demands of 33 base transceiver stations of MTN Cameroon. PVHS were computed for all sites using the technical data for a 150 Wp mono-crystalline module, the site specific hourly load data, the average monthly solar radiation and temperature. Hourly solar radiation data for all sites were downloaded using the solar resource module of HOMER and geographical coordinates of the selected sites. The 3-hourly temperature data available on a website maintained NASA was used to generate average monthly hourly temperatures needed in the calculation of the output of solar modules. The energy costs and breakeven grid distances for possible power options were computed using the Net Present Value Technique and financial data for selected power system components. The results with a PV module cost of 7.5 €/Wp, a remote diesel price of 1.12 €/l, a general inflation rate of 5% and a fuel escalation of 10% showed that the annual operational times of the diesel generator were in the range 3–356 h/year with renewable energy fractions in the range 0.89–1.00. However, only 22 PVHS had two parallel battery strings as stipulated in the request for proposal launched by MTN Cameroon in 2008. The PV array sizes evaluated for the 22 PVHS were found to be the range 2.4–10.8 kWp corresponding to daily energy demands in the range 7.31–31.79 kW h/d. The energy costs and breakeven grid distances determined were in the ranges 0.81–1.32 €/kW h and 10.75–32.00 km respectively.     

MODERGIS application: Integrated simulation platform to promote and develop renewable sustainable energy plans,Colombian case study

This research presents the MODERGIS Integrated Simulation's Platform as a tool to promote and develop renewable energy plans under sustainability criteria, in order to increment the participation of renewable technologies in the national “energy mix” and shows an application to Colombia as a case study. Potential zones of solar and wind energy and productive areas were determined for bio-energies, by means of a geographical information system which simulated energy scenarios influenced by climatic phenomena up to the year 2030. Results yield potentials of 26,600 MW in wind energy and 350,000 MW in solar energy. Bioenergy potentiates in a sustainable way of 366,310 km per biomass, 291,486 km in African palm, 9,667 km in sugar cane. These scenarios were simulated in a supply/demand with time horizons up until 2030, including an analysis of the effects on the energy systems of the El Niño Southern Oscillation atmospheric component (ENSO). Finally, in order to obtain an appropriate mix of renewable sources that could be introduced in the national energy mix, the Multi-Criteria Analysis method VIKOR was used, allowing to perform performing 5151 possible combinations of renewable projects; the optimal selection corresponds to 600 MW from wind power, 740 MW solar photovoltaic and 660 MW solar thermoelectric. Giving these results to the new scene allowed for incrementing the participation of renewable technologies up to a 0.23% in the current year and up to a 7% of the “energy mix” in the year 2030.     

Techno-economic evaluation of off-grid hybrid photovoltaic–diesel–battery power systems for rural electrification in Saudi Arabia—A way forward for sustainable development

The burning of depleting fossil fuels for power generation has detrimental impact on human life and climate. In view of this, renewable solar energy sources are being increasingly exploited to meet the energy needs. Moreover, solar photovoltaic (PV)–diesel hybrid system technology promises lot of opportunities in remote areas which are far from utility grid and are driven by diesel generators. Integration of PV systems with the diesel plants is being disseminated worldwide to reduce diesel fuel consumption and to minimize atmospheric pollution. The Kingdom of Saudi Arabia (K.S.A.) being endowed with high intensity of solar radiation, is a prospective candidate for deployment of PV systems. Also, K.S.A. has large number of remote scattered villages. The aim of this study is to analyze solar radiation data of Rafha, K.S.A., to assess the techno-economic feasibility of hybrid PV–diesel–battery power systems to meet the load requirements of a typical remote village Rawdhat Bin Habbas (RBH) with annual electrical energy demand of 15,943 MWh. Rafha is located near RBH. The monthly average daily global solar radiation ranges from 3.04 to 7.3 kWh/m². NREL's HOMER software has been used to perform the techno-economic evaluation. The simulation results indicate that for a hybrid system composed of 2.5 MWp capacity PV system together with 4.5 MW diesel system (three 1.5 MW units) and a battery storage of 1 h of autonomy (equivalent to 1 h of average load), the PV penetration is 27%. The cost of generating energy (COE, US$/kWh) from the above hybrid system has been found to be 0.170$/kWh (assuming diesel fuel price of 0.1$/l). The study exhibits that 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. Concurrently, emphasis has been placed on: un-met 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), COE of different hybrid systems, etc. The decrease in carbon emissions by using the above hybrid system is about 24% as compared to the diesel-only scenario.     

Assessment of renewable energy resources potential for electricity generation in Bangladesh

Renewable energy encompasses a broad range of energy resources. Bangladesh is known to have a good potential for renewable energy, but so far no systematic study has been done to quantify this potential for power generation. This paper estimates the potential of renewable energy resources for power generation in Bangladesh from the viewpoint of different promising available technologies. Estimation of the potential of solar energy in Bangladesh is done using a GIS-based GeoSpatial Toolkit (GsT), Hybrid System Optimization Model for Electric Renewables (HOMER) model and NASA Surface Meteorology and Solar Energy (SSE) solar radiation data. The potential of wind energy is estimated by developing a Bangladesh wind map using NASA SSE wind data and HOMER model. A review of country's biomass and hydro potential for electricity generation is presented. The technical potential of gird-connected solar PV is estimated at 50,174 MW. Assuming that 1000 h per year of full power is the feasible threshold for the exploitation of wind energy, the areas that satisfy this condition in the country would be sufficient for the installation of 4614 MW of wind power. The potential of biomass-based and small hydro power plants is estimated at 566 and 125 MW, respectively. The renewable energy resources cannot serve as alternative to conventional energy resources, yet they may serve to supplement the long-term energy needs of Bangladesh to a significant level.     

An experimental and numerical study of the gap effect on wind load on heliostat

The main handicap of the concentrating solar power technology is still the higher cost compared with the conventional coal power plant. Heliostat arrays cause about 40% of the costs of central receiver power plants. The cost reduction of heliostats is of crucial importance to central receiver power plants. The reduction of wind load on heliostats will decrease the structural requirement for heliostats, and then cut the cost of heliostats. In this paper, different gap sizes (0–40 mm) between the facets of the heliostats were studied experimentally and numerically. Both of the results showed that the wind load increases slightly with the increase of gap size (0–40 mm). The result of the numerical simulation shows the flow pattern through the gap resembles a jet flow which does not affect the static pressure on the windward surface but does decrease the static pressure on the leeward surface of the facets. Consequently it increases the total drag force on the heliostat. However, the absolute increment of the wind load is very small compared with the overall wind load on the heliostat structure. It is not necessary to take account of the gap size effects on the wind load during the design process of heliostat.     

Future of renewable energies in Iran

The activities in field of renewable energy in Iran are focused on scientific and research aspects, and research part is aimed at reduction of capital required for exploitation of related resources. The second step is to work research results into scientific dimension of this field for practical means, i.e. establishing electricity power plants. Due to recent advancements in wind energy, many investors in the country have become interested in investing in this type of energy. At the moment, projects assuming 130 MW of wind power plants are underway, of which, 25 MW is operational. Based on the planning in the 4th Socioeconomic and Cultural Development Plan (2005–2010), private sector is expected to have a share of at least 270 MW in renewable energies. However, it is the government's duty to take the first step for investment in biomass and solar power plants; private sector may then play its part once the infrastructures to this end are laid out. At the moment, a 250 kW plant is under construction in Shiraz and two more geothermal units with 5 and 50 MW capacities will follow. Moreover, two biomass and solar energy plants, standing at 10 and 17 MW, respectively, are of other upcoming projects. The project of Iran's renewable energy, aims to accelerate the sustainable development of wind energy through investment and removal of barriers. This preparatory project is funded by the global environment facility (GEF) and will provide for a number of international and national consultant missions and studies. Once the studies are concluded, a project to develop 25 MW of wind energy in the Manjil region of Gilan will be prepared. It will be consistent with the national development frameworks and objectives and form part of 100 MW of wind-powered energy, which is expected to be developed under the government's third 5-year national development plan (started 21 March 2000).     

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.     

Removal of non-CO2 greenhouse gases by large-scale atmospheric solar photocatalysis

Large-scale atmospheric removal of greenhouse gases (GHGs) including methane, nitrous oxide and ozone-depleting halocarbons could reduce global warming more quickly than atmospheric removal of CO₂. Photocatalysis of methane oxidizes it to CO₂, effectively reducing its global warming potential (GWP) by at least 90%. Nitrous oxide can be reduced to nitrogen and oxygen by photocatalysis; meanwhile halocarbons can be mineralized by red-ox photocatalytic reactions to acid halides and CO₂. Photocatalysis avoids the need for capture and sequestration of these atmospheric components. Here review an unusual hybrid device combining photocatalysis with carbon-free electricity with no-intermittency based on the solar updraft chimney. Then we review experimental evidence regarding photocatalytic transformations of non-CO₂ GHGs. We propose to combine TiO₂-photocatalysis with solar chimney power plants (SCPPs) to cleanse the atmosphere of non-CO₂ GHGs. Worldwide installation of 50,000 SCPPs, each of capacity 200 MW, would generate a cumulative 34 PWh of renewable electricity by 2050, taking into account construction time. These SCPPs equipped with photocatalyst would process 1 atmospheric volume each 14–16 years, reducing or stopping the atmospheric growth rate of the non-CO₂ GHGs and progressively reducing their atmospheric concentrations. Removal of methane, as compared to other GHGs, has enhanced efficacy in reducing radiative forcing because it liberates more _°OH radicals to accelerate the cleaning of the troposphere. The overall reduction in non-CO₂ GHG concentration would help to limit global temperature rise. By physically linking greenhouse gas removal to renewable electricity generation, the hybrid concept would avoid the moral hazard associated with most other climate engineering proposals.     

Year round test of a solar adsorption ice maker in Kunming,China

A solar adsorption ice maker with activated carbon–methanol adsorption pair was developed for a practical application. Its main features include utilization of a water cooled condenser and removing all valves in the refrigerant circuit except the one that is necessary for refrigerant charging. Year round performance tests of the solar ice maker were performed in Kunming, Yunnan Province, China. Test results show that the COP (coefficient of performance) of the solar ice maker is about 0.083–0.127, and its daily ice production varies within the range of 3.2–6.5 kg/m² under the climatic conditions of daily solar radiation on the surface of the adsorbent bed being about 15–23 MJ/m² and the daily average ambient temperature being within 7.7–21.1 °C. The suitable daily solar radiation under which the solar ice maker can run effectively in Kunming is above 16 MJ/m².     

GIS assessment of large CSP plant in Duqum,Oman

This paper discusses solar power prospects in Wilayat Duqum in Oman. First, the geographic and topographic information about the selected region is presented. The methodology of producing solar radiation map for Duqum using GIS tools is then presented. The results obtained show very high potential of solar radiation over Wilayat Duqum during the whole year. A slope analysis has allowed calculating the yearly electricity generation potential for different concentrated solar power (CSP) technologies such as the parabolic trough, parabolic dish, tower, and concentrated PV. Based on the development plan of the Duqum region, and the topologies of the land areas in the region, it is suggested that, for the CSP technologies requiring large amount of water for washing the mirrors, the selected area is a flat land (slope < 1%) located proximity to the sea (～2 km) inside a total industrial area of around 50 km², hence, allowing easy future expansion of the plant. It was proposed to start with a 100 MW power plant which is expected to consume about 2.4 km² of flat land for the parabolic trough CSP technology. The total calculated potential of yearly electricity generation would be about 2.3 TWh. If half of the selected land (0.5 × 50 km²) is reserved for future expansion of the plant, the total future capacity can attain 1 GW of electric power. The selected area can also accommodate in the future different types of CSP technologies as they mature with time.     

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.     

Estimating surface albedo over Saudi Arabia

Using ten years of solar radiation data, the surface albedo of twenty-four sites in the Kingdom of Saudi Arabia was calculated, and annual, seasonal, and geographical variations were investigated. The selected sites encompass a wide range of atmospheric conditions. The mean annual albedo values range from 0.15 to 0.54, and show high variability between different sites and even at individual sites. The differences between the maximum and minimum albedo range from 0.02 to 0.44. The average albedo over the entire kingdom is 0.31 ± 0.05. Seasonal investigations revealed that the lowest albedo values occurred during the summer and the highest in the winter. In examining the variations of the calculated albedo with the altitude, sites were divided into three groups: low altitude (0–500 m), middle altitude (500–1000 m), and high mountain sites (higher than 1000 m); the mean albedo values for each category are 0.32, 0.31, and 0.28, respectively. In studying the effects of latitude on albedo values, the sites were also divided into three groups: low latitudes (15–20), middle latitudes (20–25), and high latitudes (>25), for which the mean monthly albedo values are 0.25, 0.30, and 0.31, respectively.     

Viability of solar photovoltaics as an electricity generation source for Jordan

Viability of solar photovoltaics as an electricity generation source for Jordan was assessed utilizing a proposed 5 MW grid-connected solar photovoltaic power plant. Long-term (1994–2003) monthly average daily global solar radiation and sunshine duration data for 24 locations – distributed all over the country – were studied and analyzed to assess the distribution of radiation and sunshine duration over Jordan, and formed an input data for evaluation and analysis of the proposed plant's electricity production and economic feasibility. It was found that – depending on the geographical location – the global solar radiation on horizontal surface varied between 1.51 and 2.46 MWh/m²/year with an overall mean value of 2.01 MWh/m²/year for Jordan. The sunshine duration was found to vary – according to the location – between 8.47 and 9.68 h/day, with a mean value of 9.07 h/day and about 3311 sunshine hours annually for Jordan. The annual electricity production of the proposed plant varied depending on the location between 6.886 and 11.919 GWh/year, with a mean value of 9.46 GWh/year. The specific yield varied between 340.9 and 196.9 kWh/m², while the mean value was 270.59 kWh/m². Analysis of the annual electricity production of the plant, the specific yield, besides the economic indicators i.e., internal rate of return, simple payback period, years– to- positive cash flow, net present value, annual life cycle saving, benefit–cost ratio, and cost of energy – for all sites – showed that Tafila and Karak are the most suitable sites for the solar photovoltaic power plant's development and Wadi Yabis is the worst. The results also showed that an average of 7414.9 tons of greenhouse gases can be avoided annually utilizing the proposed plant for electricity generation at any part of Jordan.     

Calculation of bright roof-tops for solar PV applications in Dhaka Megacity,Bangladesh

Bangladesh has already been known as the country of power crisis. Although the country's electricity generation capacity is 4275 MW, around 3000–3500 MW of electricity can be generated against the demand of more than 5000 MW. The country's power is being generated mostly with conventional fuel (82% indigenous natural gas, 9% imported oil, 5% coal) and renewable sources (4% hydropower and solar). But recently a remarkable decline of the indigenous gas takes place, which rapidly aggravates electricity generation. Dhaka, the capital as well as prime city of the country with its nearly 14 million populations faces the worst situation due to the shortfall of electricity. Around 1000–1200 MW of electricity is supplied to Dhaka Megacity, while the existing demand is nearly 2000 MW. As a result frequent load shedding takes place and most of the service sectors in the city are interrupted, which has recently created immense dissatisfaction among the city-dwellers. Given the city's power crisis and geophysical situations, applications of either stand-alone or grid connected PV systems would be very effective and pragmatic for power supplement. The conservative calculation of bright roof-tops from the Quickbird Scene 2006 of Dhaka city indicates that the city offers 10.554 km² of bright roof-tops within the Dhaka City Corporation (DCC) ward area (134.282 km²). The application of stand-alone PV systems with 75 Wp solar modules can generate nearly 1000 MW of electrical power, which can substantially meet the city's power demand.     

Decentralized/stand-alone hybrid Wind–Diesel power systems to meet residential loads of hot coastal regions

In view of rising costs, pollution and fears of exhaustion of oil and coal, governments around the world are encouraging to seek energy from renewable/sustainable energy sources such as wind. The utilization of energy from wind (since the oil embargo of the 1970s) is being widely disseminated for displacement of fossil fuel produced energy and to reduce atmospheric degradation. A system that consists of a wind turbine and Diesel genset is called a Wind–Diesel power system.The literature indicates that the commercial/residential buildings in Saudi Arabia consume an estimated 10–40% of the total electric energy generated. In the present study, the hourly mean wind-speed data of the period 1986–1997 recorded at the solar radiation and meteorological station, Dhahran (26°32′N, 50°13′E in the Eastern Coastal Region of Saudi Arabia), has been analyzed to investigate the potential of utilizing hybrid (Wind–Diesel) energy conversion systems to meet the load requirements of a hundred typical two bedroom residential buildings (with annual electrical energy demand of 3512 MWh). The long term monthly average wind speeds for Dhahran range from 4.2 to 6.4 m/s. The hybrid systems considered in the present case study consist of different combinations/clusters of 150 kW commercial wind machines supplemented with battery storage and Diesel back-up. The deficit energy generated by the Diesel generator (for different battery capacities) and the number of operational hours of the Diesel system to meet a specific annual electrical energy demand of 3512 MWh have also been presented. The evaluation of the hybrid system shows that with seven 150 kW wind energy conversion system (WECS) and one day of battery storage, the Diesel back-up system has to provide 21.6% of the load demand. Furthermore, with three days of battery storage, the Diesel back-up system has to provide 17.5% of the load demand. However, in the absence of battery storage, about 37% of the load needs to be provided by the Diesel system. The study also places emphasis on the monthly average daily energy generation from different sizes (150 kW, 250 kW, 600 kW) of wind machines to identify the optimum wind machine size from the energy production point of view. It has been noted that for a given 6 MW wind farm size (for 50 m hub height), a cluster of forty 150 kW wind machines yields about 48% more energy as compared to a cluster of ten 600 kW wind machines.     

Thermal performance prediction of a solar hybrid gas turbine

The present work focuses on a modelling procedure to simulate the operation of a solar hybrid gas turbine. The method is applied to a power generation system including an heliostat field, a receiver and a 36 MW commercial gas turbine. Heat is provided by concentrated solar power and integrated by fossil fuel. A detailed modelling of the gas turbine (GT) is proposed to predict the performance of commercial GT models in actual operating conditions. Advanced software tools were combined together to predict design and off-design performance of the whole system: TRNSYS® was used to model the solar field and the receiver while the gas turbine simulation was performed by means of Thermoflex®. A detailed comparison between the solarized and the conventional gas turbine is reported, taking into account GT electric power, efficiency and shaft speed. All thermodynamic parameters such pressure ratio, air flow and fuel consumption were compared. The main advantage of solarization is the fossil fuel saving, but it is balanced by a relevant penalty in power output and efficiency.     

Hot air balloon engine

This paper describes a solar powered reciprocating engine based on the use of a tethered hot air balloon fuelled by hot air from a glazed collector. The basic theory of the balloon engine is derived and used to predict the performance of engines in the 10 kW to 1 MW range. The engine can operate over several thousand metres altitude with thermal efficiencies higher than 5%. The engine thermal efficiency compares favorably with the efficiency of other engines, such as solar updraft towers, that also utilize the atmospheric temperature gradient but are limited by technical constraints to operate over a much lower altitude range. The increased efficiency allows the use of smaller area glazed collectors. Preliminary cost estimates suggest a lower $/W installation cost than equivalent power output tower engines.     

Evaluation of choices for sustainable rural electrification in developing countries: A multicriteria approach

Rural electrification (RE) can be modelled as a multifactorial task connected to a large number of variables: decision makers need to choose the appropriate options by considering not only the techno-economic competitiveness but also socio-cultural dynamics and environmental consequences, making the task intricate. Many rural electrification projects have failed due to lack of attention to the issues beyond financial and technical dimensions. This paper presents a standardized approach for decision making concerning the extension of electricity services to rural areas. This approach first determines whether the supply provision should be grid expansion or off-grid on the basis of levelized cost of delivered electricity. If the grid expansion is found nonviable over off-grid options then a multicriteria decision aiding tool, SMAA-2 (Stochastic Multicriteria Acceptability Analysis), will evaluate off-grid technologies by aggregating 24 criteria values. While applying this approach, the delivered costs of electricity by the grid in remote areas within the 1–25 km distances vary in a range of 0.10–7.85 US$/kW h depending on the line lengths and load conditions. In the off-grid evaluation, the solar PV (photovoltaic) and biogas plants are found as the most preferable alternatives with 59% and 41% acceptability in their first rank, respectively.     

Situation and outlook of solar energy utilization in Tibet,China

The near-exponential rise in tourist numbers and accelerating economic growth have challenged Tibetan energy supply and threaten its peculiar environment and valuable ecosystem. Exploitation of pollution free solar power may medicate this demand for energy. Here we shall provide a review of solar power development in Tibet. This region has a near inexhaustible source of solar energy due to its average annual radiation intensity of 6000–8000 MJ/m², ranking it first in China and second after the Sahara worldwide. Currently, Tibet has 400 photovoltaic power stations with a total capacity of nearly 9 MW. In addition, 260,000 solar energy stoves, passive solar house heating covering 3 million square meters, and 400,000 m² of passive solar water heaters are currently in use in Tibet. Although Tibet places first in applying solar energy in China, solar energy faces big challenges from hydroelectric power and the absence of local know-how. The new power generation capacity in Tibet's “11th Five-Year (2006–2010)” Plan focuses primarily on hydropower, PV power stations being relegated to a secondary role as supplementary to hydropower. Here it will be argued that this emphasis is incorrect and that solar energy should take first place in Tibet's energy development, as it is crucial in striving for a balance between economic development, booming tourism, and environmental protection.