To be or not to be: On system dynamics and the viability of mini-grids in rural electrification

One to two billion people are expected to receive electricity access in developing countries in the coming decades. Many of these people will live in rural areas in developing countries where the existing grid will not be able to reach. These people will therefore rely on off-grid technologies to gain electricity access. One off-grid technology that is expected to grow significant is mini-grids. In addition, the number of mini-grids in developing countries are expected to growth significantly. Furthermore, renewable energy sources are increasingly used in mini-grids, putting larger emphasises on dimensioning and management of the technical system. However, previous experiences with mini-grids in rural electrification have been mixed, and many systems have failed or been abandoned prematurely. The many interactions between technical, operational and social elements make it difficult to attribute the failures to specific causes. The main purpose of this thesis is to investigate why mini-grids in rural electrification fail. The investigation focuses on reliability of electricity and how it is impacted by and impacts operation of mini-grids, the technical system and the community. The investigation is made through the implementation of system dynamics and load assessment. Rural electrification consists of many actors with different goals, it concerns the behaviour of people and is affected by technology. As, such, formulating relevant problems in rural electrification is difficult. As shown in Paper II, qualitative system dynamics can aid the process of tackling this complexity and therefore also in formulating problems. Results from Paper IV show that initial dimensioning of mini-grids is important for long-term viability. However, the dimensioning is dependent on estimations of electricity usage or electricity usage in similar areas, which are often done through collection of data through interviews. As shown in Paper III, interview-based load profiles might not be an accurate estimation of measured load profiles. Thus, estimates from interview-based load profiles might provide misleading estimations resulting in non-optimal sizing. Results from Paper I show that long-term reliability in mini-grids is affected by operational practices and community behaviour. Even though poor reliability is associated with the failure of specific components in the technical system, they are subject to operational practices and are thus influenced by the overall functioning of a mini-grid. As such, long-term reliability in mini- grids needs to be considered from a system perspective

Tackling complexity and problem formulation in rural electrification through conceptual modelling in system dynamics

Mini-grids are considered important in order to improve access to electricity in developing countries. Their technical and organizational independence from the large national grids and their interactions with local social, economic, and environmental factors suggests that system dynamics is a useful method of analysis. However, the successful implementation of mini-grids in rural electrification has partly been prevented due to complexity issues, making problem formulation difficult. Most problem-solving methods, such as system dynamics, require well-defined problems. Previous work on the problem formulation process in system dynamics is limited. This work presents a conceptual framework for tackling complexity and uncertainties in rural electrification. The conceptual framework is general and draws on research in conceptual modelling and system dynamics. The focus is on the learning that can be achieved from a system description and how it can be used to tackle complexity by reducing uncertainties and improving knowledge

Estimating national and local low-voltage grid capacity for residential solar photovoltaic in Sweden, UK and Germany

The electric grid\u27s available capacity to accommodate solar photovoltaic on national scales is currently uncertain. This makes decisions about grid capacity expansion, which can be very costly for local grid operators, difficult to make. Yet, knowledge of national solar photovoltaic grid capacity is central in order to formulate realistic solar PV targets and strategies. We present a methodology based on publicly available data to estimate the grid\u27s hosting capacity of residential solar photovoltaic at both the national and local scale. The model is applied to Sweden, Germany and the UK and shows that low-voltage grid capacity for residential solar photovoltaic is very large, 33 (+5/-7) GW (Sweden), 248 (+5/-24) GW (Germany) and 63 (+1/-14) GW UK, and similar to current total generation capacity. Based on our estimations, we find that with the capacity of the present grid Sweden can supply 24%, Germany 60% and UK 21% of their current annual net electricity consumption from residential solar photovoltaic. In addition, we find that the grid-supported individual solar PV system sizes increase as population density decreases. Finally, our work highlights the importance of implementing sizing incentives for customers when installing their solar PV systems

Comparison of load profiles in a mini-grid: Assessment of performance metrics using measured and interview-based data

Mini-grids are seen as an important option for increasing access to electricity in non-electrified rural areas where grid-extension is unfeasible. Appropriately dimensioning and constructing mini-grids requires knowledge of electricity usage. There is currently a lack of measured load profiles from mini-grids and the most common method for estimating electricity usage is through appliance data collected via interviews. Thus, this paper compares and investigates the differences between measured daily load profiles and daily load profiles created from appliance data collected through interviews and how the two methods impact the dimensioning and operation of a mini-grid. This is done by comparing load profiles for an entire mini-grid, a household and SME customers with large loads. The paper reports differing results from the two methodologies. Generally, the results show that the interview-based load profiles fail to provide an accurate overall estimate. The calculated performance metrics for the two methods also shows large differences. The interview-based load profiles mainly fail to provide accurate estimates of energy and the energy related (capacity factor and load factor) performance metrics. Accordingly, the implications for mini-grid operators and developers could be significant. The interview-based load profiles indicate the mini-grid system to be considerably less technically and economically desirable than measurements show. Suggestions for how the interview process can be improved are presented

Generating low-voltage grid proxies in order to estimate grid capacity for residential end-use technologies: The case of residential solar PV

Due to data restrictions and power system complexity issues, it is difficult to estimate grid capacity for solar PV on regional or national scales. We here present a novel method for estimating low-voltage grid capacity for residential solar PV using publicly available data. High-resolution GIS data on demographics and dwelling dynamics is used to generate theoretical low-voltage grids. Simplified power system calculations are performed on the generated low-voltage grids to estimate residential solar PV capacity with a high temporal resolution. The method utilizes previous developments in reference network modelling and solar PV hosting capacity assessments. The method is demonstrated using datasets from Sweden, UK and Germany. Even though the method is designed to estimate residential solar PV grid capacity, the first block of the method can be utilized to estimate grid capacity or impacts from other residential end-use technologies, such as electric heating or electric vehicle charging. This method presents: • A method for estimating peak demand based on population density and dwelling type. • Generation of low-voltage grids based on peak demand. • Sizing of transformers and cables based on national low-voltage regulations and standards

Comparison and Analysis of GPS Measured Electric Vehicle Charging Demand: The Case of Western Sweden and Seattle

Electrification of transportation using electric vehicles has a large potential to reduce transport related emissions but could potentially cause issues in generation and distribution of electricity. This study uses GPS measured driving patterns from conventional gasoline and diesel cars in western Sweden and Seattle, United States, to estimate and analyze expected charging coincidence assuming these driving patterns were the same for electric vehicles. The results show that the electric vehicle charging power demand in western Sweden and Seattle is 50–183% higher compared to studies that were relying on national household travel surveys in Sweden and United States. The after-coincidence charging power demand from GPS measured driving behavior converges at 1.8\ua0kW or lower for Sweden and at 2.1\ua0kW or lower for the United States The results show that nominal charging power has the largest impact on after-coincidence charging power demand, followed by the vehicle’s electricity consumption and lastly the charging location. We also find that the reduction in charging demand, when charging is moved in time, is largest for few vehicles and reduces as the number of vehicles increase. Our results are important when analyzing the impact from large scale introduction of electric vehicles on electricity distribution and generation

Linking household and productive use of electricity with mini-grid dimensioning and operation

Off-grid systems, and mini-grids in particular, are expected to play a significant role in improving electricity access to one billion people until 2040. One of the major challenges for mini-grids is associated with their high costs, low financial viability and local development impact. Productive use of electricity can be an important driver of local development and impacts the total load in a mini-grid. By using a mixture of high-resolution (minutes) measurements and long-term data (years) on electricity expenditures and purchased electricity from a mini-grid in the Tanzanian highlands, we analyse the technical and economic impact from household and productive use of electricity, respectively. The high-resolution data is analysed using performance indicators and the long-term data using regression tools. We find that a mixture of household use and productive use of electricity provides both technical and economic benefits for the operator. In addition, we find that while productive use customers only represent 25% of the customers, they generate 44% of the operator\u27s income. Furthermore, productive use of electricity customers are also likely responsible for the peak demand in the mini-grid, which occurs during day time. Lastly, we find empirical evidence suggesting that expenditures and demand are unit elastic, which has implications on economic policies for supporting rural electrification

Substation Placement for Electric Road Systems

One option to avoid range issues for electrified heavy vehicles, and the large individual batteries for each such vehicle, is to construct electric road systems (ERS), where vehicles are supplied with electricity while driving. In this article, a model has been developed that calculates the cost for supplying an ERS with electricity from a regional grid to a road in the form of cables and substations, considering the power demand profile for heavy transport. The modeling accounts for electric losses and voltage drop in cables and transformers. We have used the model to exhaustively compute and compared the cost of different combinations of substation sizes and locations along the road, using a European highway in West Sweden as a case study. Our results show that the costs for building an electricity distribution system for an ERS vary only to a minor extent with the location of substations (10% difference between the cheapest cost and the average cost of all configurations). Furthermore, we have varied the peak and average power demand profile for the investigated highway to investigate the impact of a specific demand profile on the results. The results from this variation show that the sum of the peak power demand is the most important factor in system cost. Specifically, a 30% change in the peak power demand for the road has a significant impact on the electricity supply system cost. A reduction in the geographical variation of power demand along the road has no significant impact on the electricity distribution system cost as long as the aggregated peak power demand for all road segments is held constant. The results of the work are relevant as input to future work on comparing the cost–benefit of ERS with other alternatives when reducing CO2 from road traffic—in particular from heavy road traffic

Electricity access and rural development: Review of complex socio-economic dynamics and causal diagrams for more appropriate energy modelling

The causal relationships between electrification and development of poor, rural communities are complex and contextual. The existing literature focuses mainly on the impact of rural electrification and electricity use on local socio-economic development, while the reverse feedbacks of various social and economic changes on electricity demand and supply have not been fully characterized. Most electricity access impact assessments assume linear, one-way effects and linear growth in electricity demand. However, the projections rarely match the reality, creating challenges for rural utilities. From a modelling perspective, the lack of attention to dynamic complexities of the electricity-development nexus prevents the appropriate modelling of electricity demand over time and, hence, informed planning for and sizing of power plants. With the goal to improve modelling of the electricity-development nexus, we undertake a comprehensive review and extensive analysis of the peer-reviewed literature on electricity access and its impact on rural socio-economic development, and vice versa. We characterize and describe the nexus between electricity access and development through graphical casual diagrams that allow us to capture, visualise and discuss the complexity and feedback loops. Based on this, we suggest guidelines for developing appropriate models able to include and simulate such complexities. Our analysis confirms that electricity use is interconnected through complex casual relations with multiple dimensions of socio-economic development, viz. income generating activities, market production and revenues, household economy, local health and population, education, and habits and social networks. The casual diagrams can be seen as a first step of the conceptualization phase of model building, which aims at describing and understanding the structure of a system. The presence of multiple uncertain parameters and complex diffusion mechanisms that describe the complex system under analysis suggests that systems-dynamic simulations can allow modelling such complex and dynamic relations, as well as dealing with the high uncertainties at stake, especially when coupled with stochastic approaches

A System Dynamics Analysis of Cost-Recovery A Study of Rural Minigrid Utilities in Tanzania

Over one billion people live in poverty around the world. Access to modern energy sources such as electricity is considered important in social and economic development. A number of initiatives have been taken to improve the situation but one billion people still lack access to electricity around the world, most of whom live in rural and inaccessible areas.One proposed solution to improve electricity access in rural areas is minigrids based on renewable energy sources. Minigrids have been constructed in all parts of the world with various levels of success. A common challenge for the utility’s operating them has been to achieve the ability to cover their own expenses, leading to financial difficulties.Based on a systemic approach, this work investigates cost-recovery based on a dynamic understanding of the problem. By developing a system dynamics model the problem is analyzed conceptually through a causal loop diagram and mathematically through a stock and flow model. The stock and flow model is then used to investigate the effect different generation and distribution technologies have on cost-recovery.Through the application of the system dynamics model it is found that construction and planning time together with the cost per connection are both important factors for cost-recovery. When construction and planning times are too long, the utility is not able to handle changes in demand. With a reduced power availability, usage and number of users decrease, creating a negative loop driving down the income. Even though both construction and planning time and cost per connection are found to be important, the results implies that reducing connection cost can have a large impact on cost-recovery, given that the utility has the ability to handle changes in demand.The work also identifies a possible future area of research where system dynamics modeling is integrated with load modeling and assessments. This could reduce the issues of using a static relationship between electricity and power and thereby possibly yield new insights into the connection between electricity usage, generation source and cost-recovery