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.     

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.     

Multi-objective optimisation of renewable energy systems for pollution mitigation – a case study of Kavaratti Island,India

Islands represent a unique challenge in terms of electrical energy supply. A great deal of work has been carried out on this specific aspect of energy supply on different islands in the world. Unfortunately, due to island-specific energy usage profile, resources and different kinds of environmental conditions, a study of one island cannot be easily extended to other islands. The Lakshadweep group of islands in the Arabian Sea is one of the two major groups of islands in India having diesel generators (DGs) as the main source of electricity. Considering the remoteness of the island and the polluting nature of existing DGs, it is desirable to adopt a strategy to utilise the available potential of non-polluting renewable energy sources (RESs) for these ecologically sensitive islands. A multi-objective optimisation methodology is applied in Kavaratti Island, Lakshadweep, where various RESs exist and can be exploited to generate electrical energy and to mitigate environmental pollution. A specific mathematical model is developed with two objective functions, namely cost and environmental pollution that work reversibly. Application of the proposed mathematical tool leads to a Pareto set, satisfying the multiplicity of criteria, namely environmental pollution, energy demand, per-unit generation cost and resource constraints.     

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.     

The impact of sustainability criteria on the costs and potentials of bioenergy production – Applied for case studies in Brazil and Ukraine

The goal of this paper is to analyse the impact of the implementation of a certification system on the management system (costs) of and the availability of land (quantity) for bioenergy production. Twelve socio-economic areas of concern (food supply, child labour, (minimum) wages, employment, health care and education) and environmental areas of concern (soil erosion, depletion of fresh water resources, nutrient losses and soil nutrient depletion, pollution from chemicals and biodiversity) are included. Since there is no generally accepted definition of sustainability, a loose and strict set of criteria are defined. Short rotation coppice (SRC) production systems in Ukraine and South East Brazil in 2015 are taken as case studies. The results indicate that it seems feasible to produce biomass for energy purposes at reasonable cost levels and meeting strict sustainability criteria at the same time. The loose set of criteria has no impact on the costs of energy crop production, which are calculated to be 1.7 € GJ^?1 in Brazil and 2.1 € GJ^?1 in Ukraine. The strict set of criteria results in an increase of the costs of energy crop production by 42 % in Brazil and 14 % in Ukraine. In general, compliance with strict socio-economic criteria has a limited impact on the costs, because SRC is relatively labour extensive. Strict environmental criteria likely have a larger impact.     

H2RES,Energy planning tool for island energy systems – The case of the Island of Mljet

When it comes to the energy planning, computer programs like H₂RES are becoming valuable tools. H₂RES has been designed as support for simulation of different scenarios devised by RenewIsland methodology with specific purpose to increase integration of renewable sources and hydrogen into island energy systems. The model can use wind, solar, hydro, biomass, geothermal as renewable energy sources and fossil fuel blocks and grid connection with mainland as back up. The load in the model can be represented by hourly and deferrable electricity loads of the power system, by hourly heat load, by hydrogen load for transport and by water load depending on water consumption. The H₂RES model also has ability to integrate different storages into island energy system in order to increase the penetration of intermittent renewable energy sources or to achieve a 100% renewable island. Energy storages could vary from hydrogen loop (fuel cell, electrolyser and hydrogen storage) to reversible hydro or batteries for smaller energy systems. The H₂RES model was tested on the power system of the Island of Porto Santo – Madeira, the islands of Corvo, Graciosa, and Terrciera – Azores, Sal Island – Cape Verde, Portugal, the Island of Mljet, Croatia and on the energy system of the Malta. Beside energy planning of the islands, H₂RES model could be successfully applied for simulation of other energy systems like villages in mountain regions or for simulation of different individual energy producers or consumers.     

Optimization of hybrid – ground coupled and air source – heat pump systems in combination with thermal storage

Ground coupled heat pumps are attractive solutions for cooling and heating commercial buildings due to their high efficiency and their reduced environmental impact. Two possible ideas to improve the efficiency of these systems are decoupling energy generation from energy distribution and combining different HVAC systems. Based on these two ideas, we present several HVAC configurations which combine the following equipments: a ground coupled heat pump, an air to water heat pump and a thermal storage device. These HVAC configurations are linked to an office building in a cooling dominated area in order to evaluate in these conditions the total electrical consumption of each configuration to obtain which one satisfy the thermal demand more efficiently. The results of our simulations show that the electrical energy consumption obtained when the system employs a suitable configuration is of around the 60% compared with an HVAC system driven by an air to water heat pump and around the 82% compared with an HVAC system driven by a ground coupled heat pump.     

Combined heat and mass transfer analyses in solar distillation systems – The restrictive conditions and a validity range investigation

The present work aims at the investigation of the validity range and accuracy of earlier developed theories which have been proposed for the modeling of heat and mass transfer within confined spaces in solar distillation systems. The investigation which is based on the evaluation of agreement between theoretical results and an extensive body of earlier field and laboratory measurements covers a very wide range of operating conditions and allows a comparable validation of the earlier proposed theories. It also clearly defines the restrictions, limitations and the validity range in relationship to yield as well as to the operating temperature level, beyond which significant deviations between predictions from both the earlier Dunkle’s as well as more recent analogy models and measurements occur for practical solar stills.     

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.     

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%.     

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.     

Innovative optics for concentrating photovoltaic/thermal (CPVT) systems – the case of the PROTEAS Solar Polygeneration System

The aim of this work is to review the current status of photovoltaic (PV) power generation, focusing on concentrating PVs mainly as regards their typology, market and state-of-the-art feature. The incorporation of a heat recovery system can increase the overall efficiency by exploiting the waste heat. The proposed solution is a Solar Polygeneration System (PROTEAS System) for the simultaneous production of electricity, hot water and air-conditioning. The core of the PROTEAS System is the innovative set-up of total internal reflection reflectors made of plastic (primary optical system), with the potential to concentrate solar rays up to 5000 suns, while specially designed total internal reflection homogenisers (secondary optical system) later homogenise the radiation to 1000 suns. The engineering of the system is an ongoing task, while some of the subsystems have been successfully developed.     

Ceramics and ceramic matrix composites for heat exchangers in advanced thermal systems—A review

In air-conditioning and energy-recovery applications, heat exchangers are very important to the overall efficiency, cost, and size of the system. Current heat exchanger designs rely heavily on fin-and-tube or plate heat exchanger designs, often constructed using copper and aluminum. Recent developments in material science—in particular, advances in ceramics and ceramic matrix composites—open opportunities for new heat exchanger designs. Some research directed toward using these materials for heat exchangers in other applications has been reported; however, there has not been a comprehensive study of the use of these emerging materials in both conventional HVAC&R systems and emerging energy technologies. This review reports the current state-of-the-art of ceramic materials for use in a variety of heat transfer systems.     

Utilization of excess heat in the pulp and paper industry––a case study of technical and economic opportunities

Newly developed methods and tools based on pinch technology are used in a case study to investigate the potential and economy of using excess heat for pre-evaporation of chemo thermo mechanical pulp effluent and heat pumping in an integrated pulp and paper mill. The new tools give information about the system that traditional pinch tools such as the grand composite curve or the composite curves would not reveal. For example, the highest temperature levels possible where excess heat can be released are identified together with the amount of excess heat at each temperature level. The new curves are also able to provide information about where heaters and coolers are placed in an existing system. The matrix method has been used successfully in order to find an economically feasible heat exchanger network retrofit for the release of the excess heat found with the curves.The results of the case study show that a pre-evaporation plant can be integrated with the overall process with just a few modifications in the existing process. There are also opportunities for heat pumping in the system. Both projects have a pay-back period shorter than required for implementation.     

Heat extraction thermal response test in groundwater-filled borehole heat exchanger – Investigation of the borehole thermal resistance

In groundwater-filled borehole heat exchangers (BHEs) convective flow influences the heat transfer in the borehole. During heat extraction thermal response tests (TRTs) the effect of the changing convective flow is more dominant than during heat injection tests. Water is heaviest around 4 °C and when exceeding this temperature during the test, the convective flow is stopped and restarted in the opposite direction resulting in a higher borehole thermal resistance during that time. Just before 0 °C the convective flow is the largest resulting in a much lower borehole thermal resistance. Finally, during the freezing period phase change energy is released and material parameters change as water is transformed into ice, resulting in a slightly higher borehole resistance than at a borehole water temperature of 0 °C. The changes in borehole thermal resistance are too large for ordinary analysis methods of thermal response tests to work. Instead another method is introduced where the borehole thermal resistance is allowed to change between different time intervals. A simple 1D model of the borehole is used, which is matched to give a similar mean fluid temperature curve as the measured one while keeping the bedrock thermal conductivity constant during the whole test. This method is more time-consuming than ordinary TRT analyses but gives a good result in showing how the borehole thermal resistance changes. Also, a CFD-model with a section of a simplified borehole was used to further study the effect of convection and phase change while the temperature was decreased below freezing point. The test and the model show similar results with large variations in the borehole thermal resistance. If the knowledge of changing borehole thermal resistance was used together with a design program including the heat pump and its efficiency, a better BHE system design would be possible.     

The effect of residential solar photovoltaic systems on home value: A case study of Hawai‘i

An investment in solar photovoltaic (PV) is considered a home improvement, and should be reflected in home sales prices. However, uncertainty about PV policies and information asymmetries may result in an imperfect pass-through. Hawai‘i serves as an illustrative case study to assess the impact of PV on home prices because Hawai‘i has the highest number of PV installations per capita nationwide. Applying a hedonic pricing model using home resale and PV building permit data from 2000 to 2013 for Oʻahu, I find that the presence of PV adds on average 5.4% to the value of a home. The value of PV exceeds total average installed costs because many of Hawai‘i's electricity circuits have reached legal limits for PV installations and thus many neighborhoods could technically no longer install additional PV capacity. Therefore, the value of the system goes beyond its capital investment—on average, by $5000—to incorporate expected electricity savings.     

An assessment on the planning and construction of an island renewable energy system – A case study of Kinmen Island

During the last 50 years, Kinmen's economy has gone from military-based to increasingly tourism-based, Kinmen has been putting various constructions into action, and hence, the demand for electricity supply is getting higher relatively while the province is pushing various constructions. Nowadays, Kinmen County Government has made directions for future developments already and kept on promoting the sustainable development of Kinmen Island in order to make it a suitable place for living. According to the development blueprint, the future resident population will increase to around 150 ～ 200 thousand people so the relative electricity consumption in Kinmen Island will cause serious problems for Taipower in addition to large scale environmental pollution. The present study researches on both the limitation and independence of this particular island and presumes the electricity power supply will be provided through renewable energy sources, such as solar energy, wind energy, and tidal power generation and so on, whereby it will achieve the target of energy saving and carbon reduction successfully soon. Upon the construction process of the renewable energy sources, this study will simultaneously assess the eco-environment and social conditions on the island to evaluate the feasibility of existing renewable energy technologies which are more mature and determine the optimum renewable energy system that shall be constructed in the Kinmen region in the near future, in order to replace traditional energy sources. Meanwhile, it will assist the related energy industries to create an ultra-clean environment in Kinmen with self-developing power and enhance international competition forces so as to establish a positive international image of environmental protection by achieving a habitat with energy self-sufficiency, and ultimately the empirical model can be duplicated and promoted to other islands.     

What makes renewable energy successful in China? The case of the Shandong province solar water heater innovation system

The Chinese province of Shandong, and more particularly its cities Dezhou, Jinan and Rizhao, have established an international reputation of being hotbeds for solar water heating (SWH) technology development and dissemination. The article aims to unveil the evolution of this innovative environment by applying the Functions of Innovation Systems (FIS) approach to the Chinese province of Shandong. It examines the actors, institutions and policy instruments that shape Shandong's innovation system for SWH, the dominant drivers and barriers during the evolution of the TIS and also assesses the applicability of the IS approach to China. It appears that the presence of influential interest organizations and proactive support from local governments have acted as strong drivers for the emergence of Shandong's innovation system for SWHs. On the other hand, the lack of adequate personnel and an overreliance on government policies act as main barriers. With regard to the Chinese specificities potentially detracting from the relevance of applying IS theory to China, we did not find that the central government acted as an initiator of innovation nor that state-owned enterprises had dominant positions in the market. In this innovative industry the impetus for development came from the bottom up and from private corporations.