A simulation-based evaluation of the benefits and barriers to interconnected solar home systems in East Africa

This paper outlines the relative advantages and disadvantages of interconnecting Solar Home Systems (SHSs) to form micro-grids. Real world remote monitoring data from a number of SHSs operated by BBOXX in Rwanda is analyzed and it is shown that significant demand diversity and differing patterns of energy use exist in SHSs. Significant variation in daily demand, is demonstrated for identical SHSs from 0-10 Wh/day up to 110 Wh/day. Around 65% of generated energy is currently unused and could be utilised to connect new customers and increase the demand of existing customers if systems were interconnected

Using smart power management control to maximize energy utilization and reliability within a microgrid of interconnected solar home systems

Over the past 20 years, off-grid solar home systems (SHS), comprised of solar panels, batteries, a charge controller and loads, have proved the most popular and immediate solution increasing energy access, mainly through rural electrification, across the Global South. Although deployed in significant numbers, issues remain with SHS cost, reliability, utilization and sustainability. Interconnection of SHS to form a microgrid of connected prosumers and consumers may offer a solution that, by employing smart management of the power distribution amongst connected households, has the potential to ‘unlock’ latent generation and storage capacity and so improve reliability and security of supply, reduce the system cost per head, and ultimately the levelized cost of energy supplied. These factors combine to improve the overall sustainability, efficiency and flexibility of SHS technology. This paper presents the functionality of a Smart Power Management (SPM) that seeks to distribute power across prosumers/consumers connected to a microgrid of interconnected SHS, to maximise the utilisation of available generation and storage across the system and so improve the reliability and affordability of the energy supplied. The SPM is applied and appraised using a simulation involving representative generation and demand profiles for a village with a high penetration of SHS technology. The power management methodology utilizes algorithms applied to manage power flows between customers. The simulated results demonstrate significant improvements in reliability of supply within the microgrid during low generation season

Impact of new electric cooking appliances on the low voltage distribution network and off-grid solar microgrids

Over three billion people around the world rely on biomass as their primary source of cooking fuel, a practise which is particularly prevalent across countries in Sub-Saharan Africa, Developing Asia, and Latin America. Cooking with biomass has significant negative health impacts, due to the toxic fumes produced which are estimated to cause over four million premature deaths annually. In addition, it negatively impacts the environment, through contributing to deforestation and climate change, which is exacerbated by increasing demand for biomass due to rapid population growth in these regions. Women and girls are disproportionately affected by these impacts as they are often responsible for cooking and the collection of cooking fuels. Increased adoption of electricity as a replacement for biomass as a source of cooking energy is one potential solution to reduce these negative environmental and social impacts. The studies presented in this report identify the main technical challenges associated with accommodating electric cooking on microgrids and low voltage (LV) distribution networks in sub-Saharan Africa. Evidence and experience has shown that the adoption of electric cooking appliances can already be supported by some networks without the need for any upgrades in the system. This is primarily within networks which have been overdesigned relative to existing electrical demand and as a result, sufficient headroom to adopt clean electric cooking appliances exists. Simultaneously, where system designs more closely match baseload (non-cooking) characteristics, limitations may occur when supporting the addition of electric cooking loads. Identifying these limitations has been the subject of investigations in this report. The technical analysis was primarily supported by models developed in OpenDSS. Load flows, voltage profiles and transformer/power inverter requirements were modelled to investigate the performance of representative LV and microgrid network topologies before and after the introduction of loads from different sized electric cooking devices. This research was conducted as a part of the MECS (Modern Energy Cooking Solution) consortium

Bottom-up electrification introducing new smart grids architecture : concept based on feasibility studies conducted in Rwanda

Over the past eight years, off-grid systems, in the form of stand-alone solar home systems (SHSs), have proved the most popular and immediate solution for increasing energy access in rural areas across the Global South. Although deployed in significant numbers, issues remain with the cost, reliability, utilization, sustainability and scalability of these off-grid systems to provide higher-tiered energy access. Interconnection of existing stand-alone solar home systems (SHSs) can form a microgrid of interconnected prosumers (i.e., households owning SHS capable of producing and consuming power) and consumers (i.e., households without an SHS, and only capable of consuming power). This paper focuses on the role of a smart energy management (SEM) platform in the interconnection of off-grid systems and making bottom-up electrification scalable, and how it can improve the overall sustainability, efficiency and flexibility of off-grid technology. An interconnected SHS microgrid has the potential to unlock latent generation and storage capacity, and so effectively promote connected customers to higher tiers of energy access. This approach can therefore extend the range of products currently used by people located in the remote areas of developing countries to include higher-power devices such as refrigerators, TVs and potentially, electric cookers. This paper shows the results of field studies in the Northern Province of Rwanda within off-grid villages where people mainly rely on SHSs as a source of electricity. These field studies have informed further simulation-based studies that define the principal requirements for the operation of a smart energy management platform for the interconnection of SHSs to form a community microgrid

An overview of the technical challenges facing the deployment of electric cooking on hybrid PV/diesel mini-grid in rural Tanzania – A case study simulation

This paper lays out a methodology that could be used by mini-grid developers to assess the design readiness and future design requirement to accommodate electric cooking (eCook). While mini-grids in developing countries continue to grow in popularity, typically their designs are not yet sufficiently developed to accommodate large power appliances. Moving towards clean cooking using electricity will cause technical risks for mini-grids in terms of voltage drop, voltage unbalances and capacity shortage. In this paper, these parameters are studied on a mini-grid network modeled in OpenDSS/MATLAB as a simulation platform, where the selected mini-grid topology is hub and spoke. Two network studies are considered, the first investigates the limitations of the mini-grid in terms of the generation capacity available to supply the demand for different levels of eCook penetration, while the second focuses on the network constraints for different eCook penetrations. In general, the results show that voltage drop and voltage imbalance issues can be reasonably and affordably addressed by using cables of a larger cross-sectional area. The main issue prohibiting higher penetrations of eCook centre on generation capacity requirements, which led to a techno-economic analysis being conducted to assess future mini-grid sizes as well as targeting economic and environmental objectives and meeting the overall demand on a generically representative mini-grid in a rural region in East Africa. The discussion section in this paper highlights the main barriers to the accommodation of eCook on rural mini-grids and presents suggestions for future work that addresses new design specifications for the next generation of eCook mini-grids

A field trial of off-grid SHS interconnection in Rwanda's Northern Province

Solar Home Systems (SHSs) have become a popular means of electrification for millions of people living in rural regions of developing countries with no access to the national grid. As the electrical demand grows, however, there are economic and technical challenges that exist in scaling-up SHSs. At present, up to 70% of the energy generated by SHSs is surplus and effectively goes to waste, due to high solar resource peaks aligning with low demand periods and restricted storage capacity. Interconnecting existing SHSs to form ‘DC village’ microgrids, comprised of distributed photovoltaic generation and battery storage, enables communities to unlock this surplus energy for more productive uses. This may be to service small businesses with higher energy demand than can be provided by a typical SHS (e.g. to shops or barbers), or to allow domestic consumers to connect higher powered appliances. Meanwhile, people without their own SHS can also connect to the system introducing basic lighting and phone charging for lower capital costs than those with SHSs. This paper presents the results of a field trial conducted in Murambi Village, in the Northern Province of Rwanda, which involved the interconnection of seven households with their own SHS and one with no previous access to electricity. An innovative smart controller developed by the authors to facilitate SHS interconnection was deployed across this village. Using a mix of survey and focus group methods, the paper examines how people experienced the interconnected SHS system; the opportunities and benefits (social, economic) this presented; how the system enabled the use of new (higher power) appliances and new practices by trialing a novel shared refrigeration unit; and the potential of SHS interconnection in the broader context of the 'bottom-up electrification' paradigm

Modelling the costs and benefits of modern energy cooking services-methods and case studies

Globally, 2.8 billion people still cook with biomass, resulting in health, environmental, and social challenges; electric cooking is a key option for a transition to modern energy cooking services. However, electric cooking is assumed to be too expensive, grids can be unreliable and the connection capacity of mini-grids and solar home systems is widely assumed to be insufficient. Developments in higher performance and lower cost batteries and solar photovoltaics can help, but they raise questions of affordability and environmental impacts. The range of issues is wide, and existing studies do not capture them coherently. A new suite of models is outlined that represents the technical, economic, human, and environmental benefits and impacts of delivering electric cooking services, with a life-cycle perspective. This paper represents the first time this diverse range of approaches has been brought together. The paper illustrates their use through combined application to case studies for transitions of households from traditional fuels to electric cooking: for urban grid-connected households in Zambia; for mini-grid connected households in Tanzania; and for off-grid households in Kenya. The results show that electric cooking can be cost-effective, and they demonstrate overall reductions in human and ecological impacts but point out potential impact ‘hotspots’. The network analysis shows that electric cooking can be accommodated to a significant extent on existing grids, due partly to diversity effects in the nature and timing of cooking practice