Estimating the global solar radiation for solar energy projects – Egypt case study

The main objective of this paper is to determine the best models for estimating the global solar radiation (GSR) on a horizontal surface over Egypt. A model selection criterion is used to determine the best model for each site. A general two-stage method is developed. In the first stage, 40 popular empirical models are evaluated for a specific set of sites in Egypt. In the second stage, Egypt is divided into a set of regions each of which is described by the best found GSR model. The determined regions and regional models are based on the results of the first stage and determined based on the determined best model for the sites contained in a specific region. The results show that the solar radiation over the whole lands of Egypt can be characterised by two models: the Iranna and Bapat 10P GOB 1 and the K?l?c and Ozturk.     

Study on optimal configuration of the grid-connected wind–solar–battery hybrid power system

The capacity allocation of each energy unit in the grid-connected wind–solar–battery hybrid power system is a significant segment in system design. In this paper, taking power grid dispatching into account, the research priorities are as follows: (1) We establish the mathematic models of each energy unit in the hybrid power system. (2) Based on dispatching of the power grid, energy surplus rate, system energy volatility and total cost, we establish the evaluation system for the wind–solar–battery power system and use a number of different devices as the constraint condition. (3) Based on an improved Genetic algorithm, we put forward a multi-objective optimisation algorithm to solve the optimal configuration problem in the hybrid power system, so we can achieve the high efficiency and economy of the grid-connected hybrid power system. The simulation result shows that the grid-connected wind–solar–battery hybrid power system has a higher comprehensive performance; the method of optimal configuration in this paper is useful and reasonable.     

Feasibility analysis of solar photovoltaic array cladding on commercial towers in Doha,Qatar – a case study

Building-integrated photovoltaic (BIPV) technology has become a major area of research due to environ-mental concerns. This article studies the feasibility of cladding high-rise towers in Doha with solar photovoltaic modules. Specifically, the case of the Qatar Financial Centre (QFC) is discussed. The major aim of the work is to evaluate the technical feasibility, economic impact and environmental effects of using photovoltaic panels on commercial towers in Qatar. Experimental data on solar irradiance and the effect of shading on the QFC Tower are presented. Numerical calculations are done using solar pathfinder software. The studies show that, although there is a significant amount of saving in CO₂ emission by using BIPV on towers in Doha, the payback period is still very long due to the cheaper cost of grid electricity in Qatar and poor conversion efficiency of PV panels. The complete system layout is presented and viable solutions are investigated.     

Thermo-hydrodynamic aspect analysis of flows in solar chimney power plants—A case study

The purpose of the work presented in this study is related to heat transfer and airflow modelling analysis in solar chimneys, according to some dominant parameters. A typical case of application is given in this study. It consists in analyzing a natural laminar convective heat transfer problem taking place in a chimney. Heat transfer and fluid dynamic aspects of the airflow, through an axis symmetric system in a dimensionless form, with well defined boundary conditions is thus examined. Results are related to the temperature distribution and the velocity field in the chimney and in the collector, determined by solving the energy equation, and the Navier–Stokes equations, using finite volume method. The numerical code based on this modelling is validated through the Vahl Davis benchmark solution for natural convection and to other authors for other cases.     

Assess the potential of solar irrigation systems for sustaining pasture lands in arid regions – A case study in Northwestern China

The combined impact of global climate change and increasing human activities has led to the severe deterioration of grasslands in China. Using the solar irrigation systems is an effective way for sustaining pasture lands in arid regions. A solar irrigation system is the device that uses the solar cell from the sun’s radiation to generate electricity for driving the pump. And photovoltaic pump consists of an array of photovoltaic cells and pumps water from a well or reservoir for irrigation. Although ecologists and organizations constantly work and find ways to conserve grasslands through irrigation systems that use solar energy, issues on water resources are not yet thoroughly discussed. This paper takes into account the main factors in the study of water resources, including precipitation and groundwater, to analyze the feasibility of using a photovoltaic (PV) pumping irrigation. The appropriate area for such a PV pumping irrigation in Qinghai Province is also presented. The results show that the grasslands appropriate for PV pumping cover about 8.145 million ha, accounting for 22.3% of the grasslands in the entire province. Finally, the problems and countermeasures of PV pumping irrigation, including the impact on regional water balance, groundwater level and highland permafrost, are also considered.     

Impact of the German nuclear phase-out on Europe's electricity generation—A comprehensive study

The combination of the ambitious German greenhouse gas reduction goals in the power sector and the nuclear phase-out raises many questions concerning the operational security of the German electricity generation system. This paper focusses on the technical feasibility (electricity generation and transmission) and CO₂-impact of the German nuclear phase-out on the short term (2012–2022).A detailed electricity generation simulation model is employed, including the German transmission grid and its international connections. A range of different conventional and renewable energy sources (RES) scenarios is considered. Results are presented for the change in generation mix, on the flows on the transmission network and on operational reliability issues.The scenario analysis shows that nuclear generation will be replaced mainly by coal- and lignite-based generation. This increases the CO₂-intensity of the German electricity sector. Furthermore, the results indicate that the German electricity export will decrease and under certain circumstances, the system becomes infeasible. Keeping some nuclear power plants online, would mitigate these effects. The amount of electricity generated from RES is shown to be the main driver for grid congestion.     

Optimal placement of PMUs for the smart grid implementation in Indian power grid—A case study

Efficient utilization of energy resources is essential for a developing country like India. The concept of smart grid (SG) can provide a highly reliable power system with optimized utilization of available resources. The present Indian power grid requires revolutionary changes to meet the growing demands and to make the grid smarter and reliable. One of the important requirements for SG is the instantaneous monitoring of the voltage, current and power flows at all buses in the grid. The traditional monitoring system cannot satisfy this requirement since they are based on nonlinear power flow equations. Synchro-phasor-measurement devices like phasor measurement units (PMUs) can measure the phasor values of voltages at installed buses. Consequently, the currents passing through all branches connected to that bus can be computed. Since the voltage phasor values at the neighboring buses of a bus containing the PMU can be estimated using Ohm’s law, it is redundant to install PMUs at all the buses in a power grid for its complete observability. This paper proposes the optimal geographical locations for the PMUs in southern region Indian power grid for the implementation of SG, using Integer Linear Programming. The proposed optimal geographical locations for PMU placement can be a stepping stone for the implementation of SG in India.     

Application of Sayigh “Universal Formula” for global solar radiation estimation in the Niger Delta region of Nigeria

In recent years, renewable energy utilisation in various applications has increased significantly. Applications involving solar thermal energy include air and water heating whilst solar photovoltaic systems have been installed to provide electricity for households in urban and rural areas of the developing economies. The solar radiation data are not easily available for many countries and is therefore estimated most of the times. In this work is presented the results of evaluating the Sayighr “Universal formula” for estimating the global solar radiation in the Niger Delta region of Nigeria with Umudike (longitude 7.33°E, latitude 5.29°N) as a case study. The levels of the global solar radiation which ranged from 1.99 kWh to 6.75 kWh, computed with the method are in agreement with those of earlier authors indicating that the method can be used for reproducing signatures of global solar radiation in the region when actual measurements are not available.     

Modeling the impact of integrating solar thermal systems and heat pumps for domestic hot water in electric systems – The case study of Corvo Island

The use of solar thermal systems with electricity backup and heat pumps as hot water suppliers in residential buildings seems to be a very promising way to increase energy efficiency. Nevertheless, the massive adoption of such solutions in small networks (neighborhood, village) may induce problems in the electric grid management. This study explores the impact of such systems in small electric grids, using an hourly electricity backup load model. To test and validate the model, we used the island of Corvo (Azores), a small isolated community where it is being implemented a project of electrification of domestic hot water systems (DHW). We consider different load scenarios to manage the backup of DHW systems and analyze its consequences on the peak load and overall energy demand. For Corvo, for the best case where the backup is limited and distributed along off-peak hours, we observed an increase of 24% in the peak load and 7.5% in the annual energy demand. Critical values of peak load are found in winter, when daily solar irradiation is lower than 2000 Wh/m²/day. We conclude that the solar thermal systems are responsible for most of the peak load increase, but since they have the flexibility to adjust the electric backup hours due to the thermal storage capacity, the use of these systems can minimize the impact on the grid. Heat pumps on the other hand, albeit being more efficient in terms electric backup, are less flexible to contribute to the grid management as they operate continuously.     

Design and evaluation of passive concentrator and reflector systems for bifacial solar panel on a highly cloudy region – A case study in Malaysia

Photovoltaic (PV) systems are the most promising renewable energy source in Malaysia because it is a tropical country receiving a huge amount of solar irradiation every year. However, Malaysia is surrounded by South China Sea and Malacca Straits. The vapour from the sea water with the blow of seasonal winds causes a large amount of clouds passing over the country, hence creating the variation in the direct and diffused sunlight throughout a day. The performance of the concentrators and reflectors for bifacial solar cells under the variation of direct and diffused sunlight has not been studied thoroughly. Therefore, several concentrators and reflectors have been designed, constructed and placed under a specially designed bifacial solar panel. The setup of each concentrator and reflector is as follows; scattering particles (scatterers) sprinkled across the plane mirror under the solar panel, an array of adjustable small plane mirrors placed underneath the solar panel, and long triangular prisms in between solar cells with a plane mirror underneath. Another solar panel is constructed and placed on top of the plane mirror as a reference. Each setup of the concentrators or reflectors is evaluated by measuring the power output of the tested and the reference panels together throughout a day under the sun. Empirical approaches are developed to compensate for uncontrollable factors including solar cell manufacturing mismatch and unequal degradation between the tested and the reference solar panels. A few potentially working static concentrator and reflector systems are identified based on the experimental results. An assessment is carried out to show the economic viability of the proposed setups with respect to that of the mono-crystalline solar cells.     

An experimental investigation on the effect of pH variation of MWCNT–H2O nanofluid on the efficiency of a flat-plate solar collector

The effect of pH variation of MWCNT–H₂O nanofluid on the efficiency of a flat-plate solar collector was investigated experimentally. The experiments were carried out using 0.2 wt.% MWCNT with various pH values, 3.5, 6.5, and 9.5, and Triton X-100 as additive. The procedure of ASHRAE standard was used for testing the thermal performance of flat-plate solar collector. Results show that by increasing or decreasing the pH values with respect to the pH of isoelectric point, the positive effect of nanofluid on the efficiency of solar collector is increased.     

High-temperature effects of the surrounding rocks around the combustion space area in SMFM-CRIP — A case study in China

Although the industrial experiments “strip mining-face mining” gasifier retreat control gas injection underground gasification process (SMFM-CRIP) have been completed, the existing issues of its rock movement and control become a critical bottleneck restricting large-scale production and application. Moreover, in the SMFM-CRIP process, the essential question of studying the rock movement is to master the high-temperature effect of the surrounding rock around the underground burned area. In view of the lack of research on this fundamental problem, this paper used the indoor experiments, theoretical analysis, and numerical simulation to research high-temperature effect of the surrounding rock around the combustion space area in SMFM-CRIP. The conclusions are as follows: (1) SMFM-CRIP can sufficiently extract the components of carbon in coal and the solid waste such as ash left in the goaf to realize green mining. (2) In the SMFM-CRIP experimental area, the scopes of temperature influence have limits on the mechanical properties of overlying strata on both sides of the coal wall of combustion space area. (3) The temperature influence in the SMFM-CRIP experimental area on the roof, both sides of the coal wall, and the floor of the combustion space area did not exceed 16.7, 8.7, and 13.6 m, respectively. These results provide important data and guidance for the future design of SMFM-CRIP’s large-scale production.     

Economic evaluation of hybrid renewable energy systems for rural electrification in Iran—A case study

The Binalood region in Iran enjoys an average wind speed of 6.82 m/s at 40 m elevation and an average daily solar radiation of 4.79 kWh/m²/day. Within this perspective, a remote rural village in Binalood region, called Sheikh Abolhassan, can readily be expected to have more than enough potential for its load demand to be supplied with a stand-alone hybrid renewable energy system. Yet the local state-run electrical service provider extended the utility grid to the village in 2006 to boost the already present diesel generator. This study aims, firstly, to explore how economical it would have been to keep supplying the electricity of the village by the diesel generator and add renewable energy generators to increase the renewable fraction of the system. On a second stage, we tried to investigate how renewable energy sources (RESs) can still be added to the current utility grid power supply in Sheikh Abolhassan to achieve a more economical and environmentally friendly system. The software HOMER is used in this study to evaluate the feasibility of various hybrid diesel-RES and grid-RES energy systems. Findings indicated that the addition of renewable power generators to the system both before and after the grid extension could and still can result in a more economical power system, which is obviously cleaner and more climate-benign.     

Effects of economies of scale and experience on the costs of energy-efficient technologies – case study of electric motors in Germany

Increasing energy efficiency is discussed as an effective way to protect the climate, even though this is frequently associated with additional (investment) costs when compared to standard technologies. However, the investment costs of emerging energy-efficient technologies can be reduced by economies of scale and experience curve effects. This also brings about higher market penetration by lowering market barriers. Experience curves have already been analyzed in detail for renewable energy technologies, but are not as well documented for energy-efficient technologies despite their significance for energy and climate policy decisions. This work provides empirical evidence for effects of economies of scale and experience on the costs of energy-efficient electric motors. We apply a new methodology to the estimation of learning effects that is particularly promising for energy-efficient technologies where the very low data availability did not allow calculations of learning rates so far. Energy-efficient electric motors are a highly relevant energy technology that is responsible for about 55% of German electricity consumption. The analysis consists of three main steps. First, the calculation of composite price indices based on gross value added statistics for Germany which show the changes in cost components of electric motors over the period 1995 to 2006; second, an estimation of the corresponding learning rate which is, in a third step, compared with learning rates observed for other energy-efficient technologies in a literature review. Due to restrictions of data availability, it was not possible to calculate a learning rate for the differential costs of energy-efficient motors compared to standard motors. Still, we estimated a learning rate of 9% for “Eff2” motors in a period when they penetrated the market and replaced the less efficient “Eff3” motors. Furthermore, we showed the contribution of different effects to these cost reductions, like a reduction of material use per motor produced by 15% and an improvement of labor productivity of 43%.     

Users and disusers of box solar cookers in urban India—: Implications for solar cooking projects

The purpose of this study is to understand the reasons behind the continued use or disuse of solar cookers, and to outline the implications from the results of this study for future solar cooker projects. Twenty-eight families in three urban sites in Gujarat, India who have a solar cooker have been interviewed. Their experience with solar cookers and solar cooking is studied. Direct discussions with families who have practical experience with solar cooking, brings forth significant practical issues. The study shows that many disusers of solar cookers do not have a suitable place for their solar cookers. Other disusers could not adjust their daily routines with what solar cooking requires, and some disused their solar cookers because they were not interested in using them. Both objective factors and aspects of practical interest have been shown to be important issues for understanding the conditions of prospective users and the shaping of the projects and the relevant technologies. It is concluded that project developers should consider the potential users as an important partner in project development processes. For example project developers can by close dialogue with them, uncover and define practical parameters which have important bearing on higher usability of solar cookers.     

The value chain of green hydrogen for fuel cell buses – A case study for the Rhine-Main area in Germany

As an immanent necessity to reduce global greenhouse gas emissions, the energy transition poses a major challenge for the next 30 years, as it includes a cross-sectoral increase of fluctuating renewable energy production, grid extension to meet regional electricity supply and demand as well as an increase of energy storage capacity. Within the power-to-gas concept, hydrogen is considered as one of the most promising solutions.The paper presents a scenario-based bottom-up approach to analyse the hydrogen supply chain to substitute diesel with fuel cell buses in the Rhine-Main area in central Germany for the year 2025. The analysis is based on field data derived from the 6 MW power-to-gas plant “Energiepark Mainz” and the bus demonstration project “H₂-Bus Rhein-Main”. The system is modelled to run simulations on varying demand scenarios. The outcome is minimised hydrogen production costs derived from the optimal scheduling of a power-to-gas plant in terms of the demand. The assessment includes the energy procurement for hydrogen production, different hydrogen delivery options and spatial analysis of potential power-to-gas locations.     

Electricity markets for energy,flexibility and availability — Impact of capacity mechanisms on the remuneration of generation technologies

Increased shares of Renewable Energy Sources (RES) to fulfill ambitious European policy targets, mothballing or decommissioning of existing units, and absent investments lead to concerns about the system and market adequacy. To restore market adequacy, capacity mechanisms (CMs) are widely discussed and implemented in various types. They are intended to provide sufficient and clearly perceivable long-term price signals for available capacity. As integral part of the market, CMs interact with the other markets. Markets like day-ahead markets are used to trade energy. Imbalance markets or reserve requirements are examples for markets for flexibility. Among others, green certificates are in place to value emission-neutral injection from RES. Resulting altered prices and shifting remuneration have effects on all generation technologies. CMs may affect participating technologies by imposing a capacity demand. A resulting change in the generation mix may also have an impact on non-participating technologies. Two gaps can be identified in the discussion and modeling of CMs in the literature. First, proposed game-theoretic equilibrium models fall short in representing the distinctive features of different types of CMs. Second, most models incorporating CMs found in the literature only focus on the interaction with the energy-based market. Valid assessments of CM need to consider the interaction of remuneration for available capacity and flexibility, and the indirect interaction with the remuneration for emission-neutral RES. Two formulations of a game-theoretic market equilibrium model are proposed which represent specific CMs with its distinctive features, in particular a market-wide centralized capacity market (cCM) and targeted strategic reserves (SRs). Moreover, the equilibrium models explicitly combine the CMs with markets for flexibility and indirect with remuneration for RES. We contribute to the discussion of CMs by quantifying the interactions and shifting shares of remuneration. Based on the interaction between CMs and remuneration for emission-neutral injection, the effect of CMs on non-participating RES is described. We conclude based on the case study results that targeted mechanisms, like SRs, implemented with the single purpose of ensuring availability introduce large inefficiencies in the system by missing on the interaction between availability and flexibility. In contrast, a market-wide cCM provides a beneficial outcome for all technologies. At the same time, it yields a sufficient high reserve margin at lowest cost. It provides clear signals for the different values of energy-output, flexibility, availability and emission-neutral injection.     

Prospects of “solar” hydrogen for desert development in the Arab world

In this paper, the Arab world is surveyed initially for the availability of new and renewable energy sources (NRES) including solar energy. A classification is made based on the level of development and on the energy balance of each Arab country. The target is to utilize these NRES for hydrogen production and hence for desert development claiming more arable land. The emphasis is on using solar energy.Hydrogen will be harnessed along the following avenues: (a) to provide energy for land development, (b) to provide energy for pumping and irrigation, (c) to produce fresh water, (d) to produce fertilizers based on ammonia as a starting raw material. Case studies are presented for Egypt and Saudi Arabia.     

Direct solar thermal splitting of water and on-site separation of the products—II. Experimental feasibility study

The development of a process of hydrogen production by solar thermal water splitting (HSTWS) presents a formidable technological task. The process has, however, great potential from the thermodynamic point of view and, when combined with fuel cell technology, it can lead to efficient conversion of solar energy to power. In the process under development at the Weizmann Institute of Science, water vapor is partially dissociated in a solar reactor at temperatures approaching 2500 K. Hydrogen is separated from the hot mixture of water splitting products by gas diffusion through a porous ceramic membrane.The paper describes the problems encountered during the development of the HSTWS process. The following topics are discussed in some detail: (a) achievement of very high solar hydrogen reactor temperatures by secondary concentration of solar energy; (b) materials problems encountered in the manufacture of the solar reactor; (c) development of special porous ceramic membranes that resist clogging by sintering at very high temperatures.