Self-sufficiency Index Research Articles

A Low-Voltage DC Backbone with Aggregated RES and BESS: Benefits Compared to a Traditional Low-Voltage AC System

The increasing penetration of PV into the distribution grid leads to congestion, causing detrimental power quality issues. Moreover, the multiple small photovoltaic (PV) systems and battery energy storage systems (BESSs) result in increasing conversion losses. A low-voltage DC (LVDC) backbone to interconnect these assets would decrease the conversion losses and is a promising solution for a more optimal integration of PV systems. The multiple small PV systems can be replaced by shared assets with large common PV installations and a large BESS. Sharing renewable energy and aggregation are activities that are stimulated by the European Commission and lead to a substantial benefit in terms of self-consumption index (SCI) and self-sufficiency index (SSI). In this study, the benefit of an LVDC backbone is investigated compared to using a low-voltage AC (LVAC) system. It is found that the cable losses increase by 0.9 percent points and the conversion losses decrease by 12 percent points compared to the traditional low-voltage AC (LVAC) system. The SCI increases by 2 percent points and the SSI increases by 6 percent points compared to using an LVAC system with shared meter. It is shown that an LVDC backbone is only beneficial with a PV penetration level of 65% and that the BESS can be reduced by 22% for the same SSI.

Photovoltaic Self-Consumption in Industrial Cooling and Refrigeration

The industrial sector has a great opportunity to reduce its energy costs through distributed generation. In this sense, the potential of photovoltaic self-consumption systems in the industrial cooling and refrigeration sector is shown. Two industries with photovoltaic self-consumption installations are shown and the electricity consumption profile of this type of industry which has a remarkable basal electricity consumption during daytime is analyzed. The matching between consumption and photovoltaic generation profiles is provided through the self-consumption and self-sufficiency curves considering different reporting periods (monthly and annual). Moreover, a new index is presented: self-sufficiency index for sunshine hours, φSS,SH. This index evaluates the performance of the photovoltaic self-consumption system when facing the consumption only during sunshine hours. This index may complement the self-sufficiency index and may improve the analysis of this type of systems in the industrial sector. Self-consumption indices of 90% may be provided. Moreover, self-sufficiency indices for total (24 h) and for sunshine hours of 25% and 50%, respectively, for industry A, and 26% and 45% for industry B have been obtained. During daytime, half the load consumption in this type of industry may be covered by photovoltaics while achieving high levels of use of the photovoltaic energy generated.

A new tool to analysing photovoltaic self-consumption systems with batteries

Most of the studies that can be found in the literature for analysing self-consumption systems with storage focus on global self-consumption and self-sufficiency indices and it may be very difficult to define the role of the array power and battery. In this sense, a new approach to analysing this type of systems is provided where direct and battery self-sufficiency and self-consumption indices are defined. The latter represent the direct photovoltaic self-consumed energy and the one provided by the battery. New direct and battery ZEB points are also presented. Furthermore, this type of system is generally analysed using complex 3D plots. Therefore, a new and intuitive 2D contour tool is provided: the iso self-consumption curves. The new approach has been applied to three households located in Spain. Results show that it may be reached a global self-sufficiency of 50% considering array powers and rated capacities below 3.5 kWp and 1 kWh, respectively, where direct and battery self-sufficiency indices may reach 40% and 10%, respectively. This new method together with the graphical tool may help not only to analyse this type of system but to properly size the array power and the rated capacity from either an energetic or profitability approach.

Optimization of a PV-Wind Hybrid Power Supply Structure with Electrochemical Storage Intended for Supplying a Load with Known Characteristics

An important aspect of the off-grid utilization of hybrid generation systems is the integration of energy storage facilities into their structures, which allows for improved power supply reliability. However, this results in a significant increase in the cost of such systems. Therefore, it is justified to use optimization resulting in the minimization of the selected economic indicator taking into account the most important technical constraints. For this reason, this work proposes an algorithm to optimize the structure of a hybrid off-grid power distribution system (with electrochemical energy storage), designed to supply a load with known daily energy demand. The authors recommend genetic algorithm utilization as well as a modified criterion for evaluating the quality of solutions based on the Levelized Cost of Energy (LCOE) index. Several technical and economic analyses were presented, including unit costs, power distribution of the wind and solar sections, nominal battery capacity, SSSI index (System Self-Sufficiency Index), etc. The model of the system includes durability of the elements which have a significant impact on the periodic battery replacement. The tests were carried out for two types of loads and two types of electrochemical batteries (NMC—Lithium Nickel Manganese Cobalt Oxide; and PbO2—Lead-Acid Battery), taking into account the forecast of an increased lifetime of NMC type batteries and decreasing their price within five years. The proposed synthesis method of photovoltaic-wind (PV-wind) hybrid off-line systems leads to limiting the energy capacity of electrochemical storages. Based on the analyses, the authors proposed recommended methods to improve (reduce) the value of the criterion index (LCOE) for PV-wind off-grid systems while maintaining the assumed level of power supply reliability.

GENERACIÓN DISTRIBUIDA Y AUTOCONSUMO FOTOVOLTAICO. POTENCIAL ENERGÉTICO PARA LAS INDUSTRIAS DE LAS ALMAZARAS EN ESPAÑA

The industrial sector faces a new paradigm of energy offshoring, where distributed generation can play a leading role in reducing energy costs in industries, as well as in its C02 emissions. This work shows the potential that photovoltaic self-consumption systems can present to face part of the consumption in the industries of the agri-food sector, specifically the oil mills. The electrical consumption of this type of industry for an oil mill is analyzed, as well as the level of coupling between the actual consumption profiles and the estimated photovoltaic generation profiles for a given range of powers of the photovoltaic generator. The analysis method is easily extrapolated to any mill located in Spain. Likewise, and given that this type of industry has a very characteristic consumption profile, the results obtained are easily transferable to other oil mills. For the mill analyzed, and from an annual perspective, a level of use of the generated photovoltaic energy of 75% with a self-sufficiency index of 20% has been estimated, highlighting the great potential of this technology, as an energy option in this type of industry, as well as in any other that presents a consumption with little variability.

Benefit Evaluation of PV Orientation for Individual Residential Consumers

Photovoltaic (PV) installations located in the northern hemisphere must be oriented to the south in order to obtain maximal annual yield. This is mainly driven by the remuneration mechanisms which incentivize maximal energy production to a certain extent. Nowadays, such support mechanisms are declining or even phased out in many countries. Hence, self-consuming the produced energy is getting more viable. In order to match better the load demand pattern, the azimuth angle of a PV installation could be changed or oriented towards multiple directions. This article investigates the benefits of PV installations facing other directions than the south. Therefore, the Hay & Davies transposition model has been used to calculate the in-plane irradiance, as it is found in the literature to be the most accurate for non-south faced PV installations. In order to determine the benefit, a large dataset of real measured consumption profiles has been used and then divided according to their annual consumption. Large consumers with an oversized east/west-oriented PV installation especially take advantage. The self-sufficiency index (SSI) is found to increase with almost 0.94 percent points, while the self-consumption index (SCI) increases with 6.46 percent points. The peak reduction is assessed by calculating the annual moving average of the month peaks. It is found that this moving average month peak reduction is marginal. Lastly, the reduction in storage capacity is found to be not that significant, although in terms of battery utilization it is found that the number of discharge cycles is reduced with 6%.

Estimation of Engel curves for household expenditure on dry bean and processed bean in Mexico

Dry bean is the leading source of low-cost plant-based proteins in Mexico. However, in the years following the liberalization of the economy, Mexico experienced the erosion of a self-sufficiency index for this commodity. Impending changes in the international markets for proteins compel us to reevaluate the role of dry bean for Mexico’s food security. In the present paper we set out to analyze the last link of the marketing chain in Mexico’s dry bean market: the consumer. Using data on household expenditure for 2018, the relationship between income and expenditure on dry bean as well as on processed bean is ascertained by means of the Working-Leser Engel Curve equations system. Due to the presence of zero-expenditure households in the sample, we followed the two-step Heckit procedure for the possible selection bias. The results suggest that the budget share for dry bean and for processed bean drops as income increases. The corrected conditional elasticity for dry bean is −0.1056. For processed bean, the elasticity is −0.2286. The negative sign indicates that both commodities are inferior goods.

Impacts of Array Orientation and Tilt Angles for Photovoltaic Self-Sufficiency and Self-Consumption Indices in Olive Mills in Spain

Olive mills are extensive in the Mediterranean Basin, and Spain constitutes approximately 45% of global production. The industrial sector faces a new energetic paradigm where distributed generation provided by small renewable energy sources may reduce the dependence from fossil energy sources as well as avoid energy distribution losses. Photovoltaic self-consumption systems can play an important role in confronting this challenge due to their modularity and their decreasing cost. Most of self-sufficiency energy studies are focused on building sector and discussions about the idiosyncrasy of industrial load profiles, and their matching capability with photovoltaic generation profiles can be scarcely found. This work analyzes the potential of photovoltaic self-consumption systems as a function of the array power, array tilt, and orientation angles to face the electric consumption in olive mills. Different recording intervals and reporting periods are considered. Results show that a self-sufficiency index of 40% may be achieved on olive harvest basis. Moreover, due to the load profile particularities, percentage error lower than 1.6% has been found when considering a recording interval of 60 min when matching the olive load consumption and photovoltaic generation profiles. Chosen array tilt and orientation angles may be key parameters to maximize the self-sufficiency index.

Has “Grain for Green” threaten food security on the Loess Plateau of China?

ABSTRACT There is debating over the question of whether the large-scale ‘Grain for Green’ program on the Loess Plateau of China threatens regional food security. Self-sufficiency index and cropland pressure index were used to assess food security on the Loess Plateau after the implementation of revegetation program. The results showed that the ‘Grain for Green’ program initially had a considerable impact on regional food security, where grain yield fell from 1999 to 2001, resulting in a lower grain self-sufficiency and increased farmland stress. Subsequently, grain yield in this region increased due to the elevated agricultural material input and increased construction of terraces and check dams. The grain self-sufficiency index would have increased to 96.55% if there were improvements to the agricultural conditions, such as fertilization and irrigation, which would have resulted in an increase in the crop yield per unit of 20%. However, the grain self-sufficiency increased to 105.25% via the construction of terraces and check dams. Thus, the government should further expand the ‘Grain for Green’ program in coordination with improvements to the agricultural production conditions and the construction of terraces and check dams on the Loess Plateau.

A new approach based on economic profitability to sizing the photovoltaic generator in self-consumption systems without storage

A proper assessment of the cost-competitiveness and profitability of self-consumption systems is crucial to promoting the transition from grid-dependent to energy self-sufficient buildings. Most of the approaches found in the literature may not take into account economic parameters such as taxes, depreciation and the cost of financing, which have a significant effect on the economic profitability of an investment. Moreover, they only focus on discrete array powers and relatively high recording intervals when estimating the self-consumed energy. In order to manage the aforementioned challenges, a new method will be developed to size the PV generator in a PV self-consumption system which provides the NPV curve together with the self-consumption and self-sufficiency indices for a wide range of array powers which suits residential self-consumption systems. Two scenarios will be considered depending on whether the generated surplus electricity is wasted or it is remunerated from the grid operator. Results show that not only the chosen scenario but the electricity tariff may be key parameters when optimizing NPV. Furthermore, the impact of the recording interval may be significant when estimating NPV. Percentage errors of 11.4% and 33.6% may be reached when considering a recording interval of 15 and 60 min, respectively.

The Impact of Employment Self-Sufficiency Measures on Commuting Time: Case Study of Perth, Australia

The level of commuting in cities is an important indicator of the efficiency of urban spatial structure. Recent research has come out in support of land use policies that promote balancing the number of employment opportunities and residents in local geographical units to reduce excess commuting. This study explores three employment self-sufficiency indices: job-worker balance (JWB), employment self-sufficiency (ESS) and employment self-containment (ESC), as measures for reducing the level of commuting. Using the case of Perth, Western Australia, we perform a trip-based evaluation of these three variables and investigate their effect on commuting time through statistical correlation. The results reveal that JWB, ESS and ESC levels are relatively poor across the metropolitan region. Higher ESS correlates with lower inflow travel time, but better JWB and higher ESC do not necessarily lead to shorter travel times. The findings of this study suggest that policies solely relying on these measures may not be effective in reducing commuting times. ESS and ESC do not account for the component of the trip outside the zone, which can misrepresent the level of commuting in an area. Incorporating travel time in these measures can complement their reliability, and better represent overall commuting levels within an urban structure.

Coordination of optimal sizing of energy storage systems and production buffer stocks in a net zero energy factory

Green smart factories will be one of the key elements of the future smart grids. They will play an active role in managing the volatility of power generated by renewable energy sources (RES). In order to do that, the green smart factories must set up energy management systems to control the production processes according to both the on-site power generation by RES and external signals sent by the system operators. The aim of the study is to size energy storage systems and production buffer stocks as the flexibility options, allowing the highest integration of power generated by volatile energy within a manufacturing system. The concept of the net zero energy factory is considered. Algorithms for coordinating the flexibility options optimally have been developed. These algorithms are based on mixed-integer linear programming and aim to maximize the matching between RES power generation and flexible demand. A case study is used to verify the framework results. Key performance indices, such as the system self-sufficiency index and the system self-consumption index have been considered for evaluating the solutions developed. Finally, sensitivity analysis has been performed to assess the robustness of the solutions found.

INCOME POTENTIAL OF RURAL COMMUNES OF WIELKOPOLSKA PROVINCE IN 2005-2016

The aim of the study was to assess the income potential of rural communes and to compare it to other administrative types in Wielkopolska province in 2005-2016, with particular emphasis on the Metropolitan Area of Poznań (POM). The research drew on data from the Central Statistical Office (Local Data Bank) and found income potential of rural communes of the province to be the lowest of all types of communes, with low values of own income per capita and financial self-sufficiency index. On the other hand, POM rural communes had higher own income potential compared to rural communes outside of POM or to other types of communes inside POM. The analyzed period saw increased shares of PIT revenues in the budgets of rural and urban-rural communes, which by 2016 were the most important source of own income in all groups of surveyed communes.

Assessment of the potential enhancement of rural food security in Mexico using decision tree land use classification on medium resolution satellite imagery

Because of its renewed importance in international agendas, food security in sub-tropical countries has been the object of studies at different scales, although the spatial components of food security are still largely undocumented. Among other aspects, food security can be assessed using a food selfsufficiency index. We propose a spatial representation of this assessment in the densely populated rural area of the Huasteca Poblana, Mexico, where there is a known tendency towards the loss of selfsufficiency of basic grains. The main agricultural systems in this area are the traditional milpa (a multicrop practice with maize as the main basic crop) system, coffee plantations and grazing land for bovine livestock. We estimate a potential additional milpa - based maize production by smallholders identifying the presence of extensive coffee and pasture systems in the production data of the agricultural census. The surface of extensive coffee plantations and pasture land were estimated using the detailed coffee agricultural census data, and a decision tree combining unsupervised and supervised spectral classification techniques of medium scale (Landsat) satellite imagery. We find that 30% of the territory would benefit more than 50% increment in food security and 13% could theoretically become maize self-sufficient from the conversion of extensive systems to the traditional multicrop milpa system.

Analyzing Determinant Components on East Java Rice Surplus Contribution Using Dynamical System Approach

The Ministry of Agriculture has proclaimed rice as a main food commodity, beside corn, soybeans, meat and sugar. In order to achieve the target of the Ministry of Agriculture, East Java provincial government has stipulated a policy, focusing on rice surplus of 5 million tons in 2014. This attempt is to reach the surplus number through a wide selection of technological innovations (determinant component) that increases the productivity of rice (New Superior Variety/VUB, Site Specific Nutrient Management/SSNM, Integreted Crop Management/ PTT, Jarwo/double row planting system, balanced fertilization, SOP harvest / postharvest), as well as an increase in Planting Index/IP by improving irrigation and food diversification program. By using a dynamical system approach (modeling), it can be measured the contribution of each determinant components in achieving surplus / rice self-sufficiency through simulation. The results of the simulation, it was known that the East Java’s rice surplus will continue to decline from 1,806,282 tons (2014) with 170% self-sufficiency index, fell to 1.706.771 tons (2017) and would be 1.367.901 tons (2025). This condition is due to the increasing number of population, agricultural area continues to shrink and productivity is relatively fixed. Index sufficiency / surplus will increase if there is an interference of educational policy to implement a massive exceed of VUB, SSNM, PTT, Jarwo, balanced fertilization, SOP harvest / post-harvest, IP increasing and the succession of diversification in East Java. A surplus of 4.7 million tons of rice in 2014 within East Java can be achieved by implementing massive educational policy movement of PTT and VUB (100% of the area), the application of SOP harvest / post-harvest to reach at least 50% of the area of paddy and controlling OPT strictly. The highest self-sufficiency index (281%) and a surplus of 5.22 million tons will be achieved in case of an interference in implementing policy of PTT jarwo (100% of the area) and an IP increasing amounted to 1.0 (additional areas that can be irrigated, 33.000 ha). Sustainable rice surplus would be achieved in case of an attempt to make food diversification program completely successful, strengthen family planning programs and strictly guard the Regulation No. 5/2012 on the minimum acreage of paddy fields that must be maintained.

Ecological foodprint of Iran

ABSTRACTFood production, consumption, ecological footprint of foodstuffs (foodprint), biocapacity, and ecological deficit of Iran for the period of 1991–2013 were evaluated and the trend toward the year 2025 was estimated. Total food production and consumption for 2012–2013 were 89.5 and 94.5 million tons with a self-sufficiency coefficient of 0.87. The ecological footprint for the country is 2.8 global hectare (Gha) and foodprint is 0.88 Gha per person with an increase of 3.3 and 2.9% per year up, respectively, to the year 2025, reaching values of 3.34 and 1.05 Gha per person. Biocapacity of the country is estimated as 0.82 Gha per person with an ecological deficit of 0.9 Gha with a predicted value of 2.5 Gha for the year 2025. The balance between consumption and national food production as well as foodprint was analyzed under 4 scenarios differing in the amount of consumption of meat and dairy products. In all scenarios with increasing consumption of animal products, the unbalanced relation of consumption–production was intensified and resulted in a decreased self-sufficiency index and increased foodprint. Results also showed that enhancement of input use efficiency (water and nitrogen) by 20% higher than current values could lead to improvement of agricultural self-sufficiency and considerable reduction of foodprint in all future scenarios.

Analysis of the basic strategic crops of Mexico through the Food Self-Sufficiency Index, 2011-2020

El presente estudio tiene por objetivo calcular el Índice de Autosuficiencia Alimentaria (IAA) para un conjunto de nueve de los cultivos estratégicos básicos señalados por la Secretaría de Agricultura y Desarrollo Rural del Gobierno de México, siendo los seleccionados el arroz, la avena, el cacao, el café, el frijol, la manzana, la soya, el sorgo y el trigo, para el periodo 2011-2020. El IAA ayuda a medir el estado y evolución de la capacidad nacional para satisfacer el abasto interno de un determinado bien. Valores bajos del IAA indican que el abasto de dicho producto es altamente dependiente de las condiciones que imperen en los mercados internacionales del mismo. Para el caso mexicano, los valores más bajos del IAA se encontraron en la soya, el arroz y la avena. Los productos que mostraron las condiciones más favorables fueron el café, el frijol, la manzana y el sorgo.

Application of Bayesian spatial smoothing models to assess agricultural self-sufficiency

With the rising oil prices, climate change, and the ever increasing burden of nutrition-related disease, food security is of growing research interest in academic disciplines spanning agronomy to epidemiology to urban planning. Some governments have developed progressive policies encouraging individuals to consume locally produced foods in order to support local economies, improve agricultural sustainability and community access to food, and to plan and prepare for adverse environmental impacts on food security. However, fundamental methods are lacking for conducting research on food security across these various disciplines. In this article, we first present a method to measure agricultural self-sufficiency, which we refer to as our self-sufficiency index (SSI) for the province of British Columbia, Canada. We then present a Bayesian autoregressive framework utilizing readily available agricultural data to develop predictive smoothing models for the SSI. We find that regional capital investment in agriculture and cropland acreage is the strong predictor of SSI. To accommodate spatial variability, we compare linear regression models with spatially correlated errors to less traditional spatially varying coefficient models, and find that the former class results in better model fit. The smoothed maps suggest that relatively strong self-sufficiency exists only in subset clusters in the Okanagan, Peace River, and lower mainland regions. In spite of policy to promote local food, the existing local agricultural system is insufficient to support a large-scale shift to local diets. Our approach to estimating neighborhood-based self-sufficiency with a predictive model can be extended for use in other regions where limited data are available to directly assess local agriculture and benefit from explicit consideration of spatial structure in the local food system.

Information Transparency and Agency Costs in the Microfinance Industry

The microfinance sector is an important ingredient in the process of global integration of the financial markets. The rapid development of the microfinance sector in many developing countries motivated prominent donors to develop systems for standardised and comparable reporting of financial and social performance. This effort has yielded substantial results in terms of promoting transparency, reducing information asymmetries and mitigating agency conflicts in an industry vulnerable to such problems. The article discusses these problems and the steps initiated by the industry to overcome them. We also point to conflicts of interests that may persist because the information platform and the indicators that are being reported are managed and selected by the industry itself. In particular, we use a common indicator of performance, the Operational Self-Sufficiency Index, to highlight the tendency of selected indicators to overstate performance and understate subsidies and costs.

The dynamics of farm milk price formation in Brazil

Dairy is a highly relevant segment of the Brazilian agribusiness economy. However, this segment has changed significantly after deregulation Thus, it is worthwhile to know what the changes are in the spatial integration of the market and in milk price formation at the farm level after deregulation. The methodology is a modification of Gonzalez-Rivera & Helfand (2001), which is compounded in extension of the market, pattern of integration, and degree of integration. The extension of the market is determined through the measure of self-sufficiency index, unit root test, and Johansen test. The last one is focused on the searching for a common trend between the time series. The pattern of interdependence is studied using the Directed Acyclic Graph (DAG). Lastly, the degree of integration is measured by the impulse response functions derived from the Bernanke decomposition. As a result, we found that the milk market in Brazil is composed by Goiás, Mato Grosso, Mato Grosso do Sul, Minas Gerais, Paraná, Rio de Janeiro, Rio Grande do Sul, Santa Catarina, and São Paulo. We also discovered that these markets have small speed of adjustment to shocks and there is no leader in milk price formation.