A multi-objective optimisation approach to water management

The management of river basins is complex especially when decisions about environmental flows are considered in addition to those concerning urban and agricultural water demand. The solution to these complex decision problems requires the use of mathematical techniques that are formulated to take into account conflicting objectives. Many optimization models exist for water management systems but there is a knowledge gap in linking bio-economic objectives with the optimum use of all water resources under conflicting demands. The efficient operation and management of a network of nodes comprising storages, canals, river reaches and irrigation districts under environmental flow constraints is challenging. Minimization of risks associated with agricultural production requires accounting for uncertainty involved with climate, environmental policy and markets. Markets and economic criteria determine what crops farmers would like to grow with subsequent effect on water resources and the environment. Due to conflicts between multiple goal requirements and the competing water demands of different sectors, a multi-criteria decision-making (MCDM) framework was developed to analyze production targets under physical, biological, economic and environmental constraints. This approach is described by analyzing the conflicts that may arise between profitability, variable costs of production and pumping of groundwater for a hypothetical irrigation area.     

Water Appropriation Systems for Adapting to Water Shortages in Iraq

Climate variability and population growth have intensified the search internationally for measures to adapt to fluctuations in water supplies. An example can be found in the lower part of the transboundary Tigris‐Euphrates Basin where water shortages in 2008‐2009 resulted in high economic costs to irrigation farmers. Losses to irrigators in the lower basin have made a compelling case to identify flexible methods to adapt to water shortage. Few published studies have systematically examined ways to enhance the flexibility of water appropriation systems to adapt to water shortage. This article addresses an ongoing challenge in water governance by examining how profitability at both the farm and basin levels is affected by various water appropriation systems. Four water appropriation systems are compared for impacts on farm income under each of three water supply scenarios. Results show that a (1) proportional sharing of water shortages among provinces and (2) unrestricted water trading rank as the top two appropriation systems. The shadow price of water for irrigation rises from zero at a full water supply level to US$93/1,000 m³ when supply falls to 20% of full levels. Similar methods could be used to analyze challenges facing the design or implementation of water appropriation systems in the world's irrigated regions.     

Real‐Time Analysis of Energy Generation of a Photovoltaic System Installed in the City of Lajeado,Rio Grande do Sul

Considering successive and costly increases in electricity rates, this article evaluates the generation of electricity from a photovoltaic system using solar energy, a renewable source. The solar photovoltaic system is installed at UNIVATES University Center, a public university in the state of Rio Grande do Sul, Brazil, and it is also connected to the electrical grid. Data related to the climatic conditions of the location, such as incident solar radiation, rainfall, and mean temperature, were obtained during the system's evaluation period and used along with bibliographic research on similar systems installed in southern Brazil. Our study quantified the energy produced over one calendar year (2014) and related it to the climatic variables and the conversion efficiency achieved by the system's photovoltaic modules. Our results show that there is both a strong relationship between the production of energy and climatic conditions and that the city, Lajeado, and the Brazilian state of Rio Grande do Sul, have good potential to supply energy using photovoltaic systems connected to the electrical grid. The horizontal global solar radiation average obtained in the study location was 4.14 kilowatts per square meter per day (kWh/m²/day), and the average monthly production of energy reached 243.93 kWh/m²/month, with a total of 2,927.10 kWh produced in 2014, achieving a monthly average conversion efficiency of 11.07%. This conversion efficiency is close to the value of 12.6% obtained in 2013 in a similar study of the same solar photovoltaic system conducted over a shorter time period.     

A multi-criteria framework to assess the sustainability of renewable energy development in the Alps

A multi-criteria analysis (MCA) was implemented to assess the best solutions for enhancing the production of renewable energy in the Alps. A set of criteria were selected based on the impacts of four renewable energy sources (forest biomass, hydropower, ground solar photovoltaic and wind power) on the three spheres of sustainability (environmental, social and economic). Three different scenarios are presented, each with a different set of weights for the criteria: the first scenario considers equally all three aspects of sustainability; the second scenario foresees an environmentally-oriented perspective, while the third scenario is more focused on the socio-economic aspects related to the development of renewable energy. Results show that forest biomass and hydropower seem to be the most viable solutions for enhancing the share of renewable energy in the Alps. Ground solar photovoltaic and wind power, on the other hand, seem to be less attractive alternatives due to their high impacts on land use.     

Health and safety implications of alternative energy technologies. II. Solar

No energy technology is risk free when all aspects of its utilization are taken into account. Every energy technology has some attendant direct and indirect health and safety concerns. Solar technologies examined in this paper are wind, ocean thermal energy gradients, passive, photovoltaic, satellite power systems, low- and high-temperature collectors, and central power stations, as well as tidal power. For many of these technologies, insufficient historical data are available from which to assess the health risks and environmental impacts. However, their similarities to other projects make certain predictions possible. For example, anticipated problems in worker safety in constructing ocean thermal energy conversion systems will be similar to those associated with other large-scale construction projects, like deep-sea oil drilling platforms. Occupational hazards associated with photovoltaic plant operation would be those associated with normal electricity generation, although for workers involved in the actual production of photovoltaic materials, there is some concern for the toxic effects of the materials used, including silicon, cadmium, and gallium arsenide.Satellite power systems have several unique risks. These include the effects of long-term space travel for construction workers, effects on the ozone layer and the attendant risk of skin cancer in the general public, and the as-yet-undetermined effects of long-term, low-level microwave exposure. Hazards may arise from three sources in solar heating and cooling systems: water contamination from corrosion inhibitors, heat transfer fluids, and bactericides; collector over-heating, fires, and out-gassing and handling and disposal of system fluids and wastes. Similar concerns exist for solar thermal power systems. Even passive solar systems may increase indoor exposure levels to various air pollutants and toxic substances, eitherdirectly from the solar system itself or indirectly by trapping released pollutants from furnishings, building materials, and indoor combustion.Operated by Union Carbide Corporation under contract W-7405-eng-26 for the U.S. Department of Energy.     

Are Investments in Groundwater Irrigation Profitable? A Case of Rice Farms from South India1

Varghese, Shalet Korattukudy, Jeroen Buysse, Aymen Frija, Stijn Speelman, and Guido Van Huylenbroeck, 2012. Are Investments in Groundwater Irrigation Profitable? A Case of Rice Farms from South India. Journal of the American Water Resources Association (JAWRA) 1‐15. DOI: 10.1111/j.1752‐1688.2012.00690.x Abstract: This article examines the profitability of cultivating double rice under bore well irrigation, given the cumulative interference of and reduced life span of wells, and thus increases the cost of groundwater extraction and use. The overexploitation of groundwater is a common stock problem and the cultivation of water intensive crops, such as rice, further exacerbates the overdraft of groundwater. Under these circumstances, we quantify the marginal benefit of irrigation investments in rice farming by estimating the probability of having a double rice crop as a function of the investment made in wells. Using this information, we explore profit maximization behavior of farms with a mathematical programming model to derive individual economic optima of irrigation costs. The results demonstrate that the ongoing overexploitation of groundwater, and its use to cultivate an economically inefficient crop, such as rice, has resulted in low profitability at farm level. A sensitivity analysis found that even when the investment in irrigation wells is reduced by 70%, small farms are still not economically efficient, thereby confirming the Tragedy of the Commons. Raising awareness amongst farmers with regard to the economics of irrigation would facilitate the participatory implementation of control mechanisms to regulate groundwater extraction.     

Economic dispatch of power system containing wind power and photovoltaic considering carbon trading and spare capacity variation

The drying up of the fossil energy sources and the damage from unchecked carbon emissions demand the development of low carbon economy, which promotes the development of new energy sources, such as wind power and photovoltaic. However, the direct connections of wind/photovoltaic power into power grid bring great impacts on power systems, thus affecting the security and stability of power system operations, which challenges the power system dispatching. In despite of many methods for power system dispatch, lack of the models, for power system containing wind power and photovoltaic considering carbon trading and spare capacity variation (PSCWPCCTSCV), restricts the further optimal operations of power systems. This paper studies the economic dispatch modeling problem of power system containing wind power and photovoltaic, establishes the model of economic dispatch of PSCWPCCTSCV. On this basis, adaptive immune genetic algorithm is applied to conduct the economic operation optimization, which can provide the optimal carbon trading price and the optimal power distribution coefficient. Finally, simulations based on the newly proposed models are made to illustrate the economic dispatch of PSCWPCCTSCV. The results show that optimization with the proposed model can not only weaken the volatility of the new energy effectively, but also reduce carbon emissions and reduce power generation costs.     

“林光互补”:库布其沙漠治理的探索

从单一的工程措施到复合生态治理是沙漠治理的必然趋势。为探寻沙漠复合生态治理的可行性方案，探究复合生态治理的实践过程和综合效益。通过对库布其沙漠“林光互补”的实践，进行案例研究。发现“林光互补”复合生态治理，以在沙漠地区建设光伏板的方式，将太阳能转换为电能，利用光伏板下降温增湿的优点，发展板下种植，实现经济效益的同时，减少了风沙对发电设备的影响，促进了当地生态的修复。“林光互补”的复合生态治理将经济发展与生态修复互构，促进沙漠地区的良性运行。同时还应考虑生态与人类生活的关系问题，实现沙漠治理的可持续发展。     

RESIDUAL POWER AND ECONOMIC FEASIBILITY OF A SOLAR POWERED IRRIGATION SYSTEM1

ABSTRACT: The problem of nonmatching irrigation and solar power production seasons creates the problem of what to do with the surplus power. The economic law of opportunity cost dictates that substitution for currently commercially purchased power is the best use for this power. This law also allows for new power using enterprises that satisfy specific criteria to be used on the farm before sale of the residual to a local public utility can be considered. Economic and Financial Evaluation of the solar powered irrigation system show that the price of commercially purchased power must reach 9.5 cents per Kwh before the system is feasible under the ideal assumption of complete use of the residual power to substitute for commercially purchased power.     

ENGINEERING ECONOMIC ANALYSES OF ARTIFICIAL RECHARGE IN THE COLUMBIA BASIN PROJECT,WASHINGTON1

ABSTRACT: Appraisal-level, engineering economic analyses for two types of irrigation systems are compared: (1) a surface-water irrigation system, and (2) a ground-water recharge irrigation system. An artificial recharge irrigation system is an economically viable alternative to surface-distributed irrigation in a conjunctive irrigation plan if electric power rates remain sufficiently low. As electric rates increase, this viability generally decreases until it becomes completely unattractive at rates of about 0.012 dollars per kilowatt hour.     

ECONOMIC IMPACTS OF THE LIMITED IRRIGATION-DRYLANI) (LID) FURROW IRRIGATION SYSTEM'

ABSTRACT: Changes in cropping patterns, water use, and profitability of producing sorghum with the LID (Limited Irrigation-Dryland) furrow irrigation system were compared with conventional irrigation practices. A recursive linear programming model was used to assess the economic impacts over a ten-year period. The analysis of various water resource situations in the High Plains of Texas indicated the LID system increased irrigated sorghum acreage over conventional practices. Although less irrigated and dryland wheat was generally produced, present value of returns increased from about $18 per acre to $50 per acre. Water use was slightly higher in most situations when using the LID system.     

Economic and financial analysis on rainwater harvesting for agricultural irrigation in the rural areas of Beijing

Since 2006, around 600 rainwater harvesting systems have been constructed for agricultural irrigation in Beijing. The financial and economic implications of using these systems are discussed less. It is important to understand the effectiveness of the investments spent on the rainwater harvesting systems. The paper aims to analyze economic and financial performance of the constructed rainwater harvesting systems in rural areas of Beijing through the method of cost benefit analysis. The economic analysis focuses on determining the contribution of rainwater harvesting systems to the development of society, carried out from the point of view of government. The financial analysis allows comparison of the financial implications of using groundwater with using rainwater for agricultural irrigation from the point of view of individual participant, namely the local farmers. The results show that the rainwater harvesting systems are economically feasible. This means rainwater harvesting have positive effects for society. However, the financial feasibility of rainwater harvesting systems depends on the charge for groundwater and on the size of the rainwater harvesting systems. If groundwater is not charged, the rainwater harvesting systems are not financially feasible. If groundwater is charged at 2 Yuan/m³, only large size systems are financially feasible while small and middle sizes systems are not financially feasible. Under these circumstances, only large systems can run smoothly, while farmers may not use the small and medium-size systems.     

Comparisons and critical assessment of global and diffuse solar irradiation estimation methodologies

Defining better methodologies of accurate predictions of the amount of monthly mean daily global and diffuse solar irradiation exposed is of utmost importance in order to determine the potential for utilizing the solar energy. This study compares and discusses the main methodologies, databases, and software that are used in estimating the solar irradiation to be used for the short- and long-term performances and feasibilities of solar energy systems, especially photovoltaic power plants in Turkey, and addresses the best one to be used to make the most accurate estimations. The comparisons are carried out between the recent methodologies developed by the authors, some models taken from the related literature that are concluded to be better, a widely used database, namely Meteonorm, and a widely used software, namely EU PVGIS. The reference data to develop the methodologies and to make comparison are provided from the State Meteorological Service of Turkey, which is the responsible body in Turkey to make measurements of solar irradiation. The comparisons are based on monthly mean daily values of global and diffuse solar irradiation and are carried out by statistical errors: mean bias error and root mean square error. The results showed that the methodology developed by the authors has shown better performances in estimating the monthly mean daily global and diffuse solar irradiation amount for Turkey.     

VALUATION OF IMPROVED IRRIGATION EFFICIENCY FROM AN EXHAUSTIBLE GROUNDWATER SOURCE1

This paper presents estimates made via a recursive linear programming model of the net benefits of improving irrigation application efficiency from an exhaustible groundwater source. Net benefits were derived for different application efficiency levels under furrow, sprinkler, and LEPA irrigation systems. In addition, net benefit estimates were obtained for the transition across irrigation systems. Solutions from the model indicate that low crop prices have a differential impact on net benefits across irrigation application efficiencies and irrigation systems. Also, the more limited groundwater situations consistently reduce the economic incentive to adopt improved irrigation application techniques across all irrigation systems.     

Analysis of a solar photovoltaic-assisted absorption refrigeration system for domestic air conditioning

Theoretical model of a solar photovoltaic integrated water-Lithium bromide absorption system is presented for domestic air conditioning. Surplus electrical energy from photovoltaic modules is used for charging the battery, which is utilized during the periods of zero or insufficient solar radiation. Minimum solar area required for each month is calculated and October is identified as the month requiring the highest area of photovoltaic arrays for a constant cooling load of 3.5 kW. The integrated system is found to be capable of sufficient amount of surplus electrical energy generation during both summer and winter months, with a daily excess of about 815 Ah of electrical energy on average over a complete calendar year. Designed system is found to be economically viable, having an energy payback period of 2.7 years.     

LCA-Based Economic Benefit Analysis for Building Integrated Photovoltaic (BIPV) Façades: A Case Study in Taiwan

Solar energy is one of the major sources of alternative and green energies that humanity need now and will continue to need in the future. There are now a large number of R&D activities on solar power generation facilities and equipment around the world. Located in a subtropical region, Taiwan is rich in solar energy resources; therefore, how to effectively use and store solar energy is a research topic of great interest to Taiwan. The main purpose of this study explores the economic benefits of building-integrated photovoltaics (BIPV) facilities and equipment by analyzing the net present values (NPV) and payback period of the BIPV façade of a shopping mall in Taiwan over its lifecycle. The NPV and payback period analysis results both indicate that the BIPV façade in the case study reaches its breakeven point within 10 years of payback period and 16 years of NPV during a life cycle of 20 years. By showing BIPV investments can bring an acceptable range of benefits profits, this study hopes to provide references for promoting the photovoltaic (PV) industry.     

SUPPLEMENTAL IRRIGATION OF HORTICULTURAL CROPS IN THE HUMID REGION1

ABSTRACT: A computer model was developed in order to establish a yield predictive relationship and to estimate the water requirements for supplemental irrigation of horticultural crops in the humid region. Alternative distribution systems were developed and designed using the results from the computer model and Wood's (1980) pipe network algorithm. The capital, operational, and maintenance costs of the distribution and recommended on-farm irrigation systems were determined and used to evaluate the economic feasibility of the alternative designs. Results show that the concentration of irrigated area along the distribution system, the length of the distribution system, and cropping system all have an important effect on the economic feasibility of supplemental irrigation in Wayne County, Kentucky.     

Comparative study on performances of a heat-pipe PV/T system and a heat-pipe solar water heating system

The heat-pipe solar water heating (HP-SWH) system and the heat-pipe photovoltaic/thermal (HP-PV/T) system are two practical solar systems, both of which use heat pipes to transfer heat. By selecting appropriate working fluid of the heat-pipes, these systems can be used in the cold region without being frozen. However, performances of these two solar systems are different because the HP-PV/T system can simultaneously provide electricity and heat, whereas the HP-SWH system provides heat only. In order to understand these two systems, this work presents a mathematical model for each system to study their one-day and annual performances. One-day simulation results showed that the HP-SWH system obtained more thermal energy and total energy than the HP-PV/T system while the HP-PV/T system achieved higher exergy efficiency than the HP-SWH system. Annual simulation results indicated that the HP-SWH system can heat the water to the available temperature (45°C) solely by solar energy for more than 121 days per year in typical climate regions of China, Hong Kong, Lhasa, and Beijing, while the HP-PV/T system can only work for not more than 102 days. The HP-PV/T system, however, can provide an additional electricity output of 73.019 kWh/m², 129.472 kWh/m², and 90.309 kWh/m² per unit collector area in the three regions, respectively.     

The Economics of Small Photovoltaic Systems for Village Energy Supply

After several years of experimentation and demonstration, photovoltaic (PV) power is now firmly established for certain applications where reliable power is required in remote locations. The technology has recently matured to the point where PV is now an appropriate, cost-effective technology for village use. This paper reviews experience and presents economic comparisons between photovoltaic and conventional power systems. It is concluded that PV is cost-effective for individual home lighting and small loads such as radios, when compared with kerosene lamps and batteries. For mutiple uses PV is cost-effective compared with diesel generators for daily electricity demands up to around 20 kWh, depending on local conditions.     

Modeling urban solar energy with high spatiotemporal resolution: A case study in Toronto,Canada

This research presents a method to determine the maximum potential for the capturing of solar radiation on the rooftop of buildings in an urban environment. This involves the modeling of solar energy potential and comparison to historical building energy demand profiles through the use of 3-D solar simulation software tools and geographic information systems (GIS). The objective is to accurately identify the amount of surface area that is suitable for solar photovoltaic (PV) installations and to estimate the hourly PV electricity generation potential of existing building rooftops in an urban environment. This study demonstrates a viable approach for modeling urban solar energy and offers valuable information for electricity distributors, policy makers, and urban energy planners to facilitate the substantial design of a green built environment. The developed methodology is comprised of three main sections: (1) determination of suitable rooftop area, (2) determination of the amount of incident solar radiation available per rooftop, and (3) estimation of hourly solar PV electricity generation potential. A case study was performed using this method for Ryerson University, located in Toronto, Canada. It was found that solar PV could supply up to 19% of the study area’s electricity demands during peak consumption hours. The potential benefits of solar PV was also estimated based upon hourly greenhouse gas emission intensity factors as well as Time-of-Use (TOU) savings through the Ontario Feed-in-Tariff (FIT) program, which allows for better representation of the positive impacts of solar technologies.