• Energy Research

In rural Nepal, micro-hydropower plant mini-grids provide renewable electricity to thousands of communities but the plants often have poor financial sustainability. Widespread uptake of electric cooking in such communities is currently not feasible due to high peak loads and limited capacity. In this paper, we develop a Remote-Areas Multi-Energy Systems Load Profiles (RAMP)-based stochastic techno-economic model for evaluating the economic viability of off-grid communities and improving their financial sustainability by introducing new appliances, productive end uses, and demand-side management measures. The model can be used to understand community electricity demand, assess economic status, determine equitable and profitable tariff structures, and plan new connections including electric cooking promotion or new industrial machines. Detailed electric cooking load modelling functionality was developed to represent Nepali cooking practices, scalable to approximate widespread uptake of electric cooking, and adaptable to other cookers and contexts. The model showed that a payment structure based on electricity consumption rather than a flat tariff could increase the income of a case study community in Eastern Nepal by 400%, although increased monthly payments for certain households from NPR 110 (USD 0.93) to NPR 500–1100 (USD 4.22–9.29) could present difficulty. However, households could reduce their electricity consumption and a more equitable tariff structure could be chosen while preserving plant profitability. The number of industrial machines such as mills could be doubled and up to 40 households provided with electric cookers if demand-side management measures were introduced.

Abstract Turgo turbines are reported to be reliable, robust and able to operate efficiently over a range of flow rates. They are typically used in medium- to high-head applications. In this paper, the operation of a single-jet Turgo turbine outside of this typical application domain is investigated, at low heads of 3.5 m down to 1 m, a typical head range available for remote communities. A 2D quasi-steady-state mathematical model with low computational requirements is developed, to arrive at a base-line design. Experimental results from this base-line design show the model to predict torque within 5% at the peak power point across the investigated head range. The model requires no calibration and is therefore suitable for rapid performance estimation of first designs. As the head decreases and the jet diameter increases, 3D effects become more significant, reducing the accuracy of the model. Therefore, the model is used to identify important parameters for a further experimental study: Here, these parameters are varied from the base-line design to provide the sensitivity of the efficiency to each parameter. This study improves the turbine’s performance by 5% relative the base-line design to 91% peak jet-to-mechanical power efficiency at 3.5 m head, and at 1.0 m head provides a 20% improvement in the efficiency to 87%.

Abstract There is a paucity of data on energy access in refugee camps and limited analysis regarding the viability of modern energy technologies such as solar home systems in these contexts. This paper addresses these by presenting an overview of the household and small enterprise electricity access situation in Kigeme, Nyabiheke and Gihembe camps in Rwanda and through the application of a Political, Economic, Social, Technological, Legal and Environmental (PESTLE) analysis to assess the barriers influencing solar home system provision. Most households and small enterprises currently have limited or no access to electricity and there is significant unmet demand for energy services such as mobile phone charging, lighting, and entertainment in the camps. The analysis suggests that solar home systems can meet these energy needs and identifies important factors in ensuring projects are successful. Projects should be informed by the needs and priorities of end-users and should be aligned with national policies, such as achieving Tier 2 energy access, to garner political support. Where possible, local market systems should be nurtured to normalise paying for energy products and to avoid free distribution. This can support private sector engagement and result in longer system lifetimes through improved maintenance. Energy literacy programmes can also improve awareness of solar home systems and their benefits compared to traditional sources of energy. These findings can inform practitioners on the supporting policy/financial frameworks, design requirements and implementation measures needed to maximise the benefits of future solar home system projects and help achieve electrification targets.

In the Global South, pico- and micro-hydropower turbines are often made by local workshops. Despite several advantageous features, e.g., a high power density and capacity to handle silt, there is no commonly available Turgo turbine design appropriate for local manufacture. Technological developments including the internet, CAD, and additive manufacturing increase the opportunity to precisely transfer designs around the world. Consequently, design improvements can be shared digitally and used by manufacturers in their local context. In this paper, a rationalised CFD approach was used to guide simple design changes that improve the efficiency of a Turgo turbine blade. The typical manufacturing capacity of the micro-hydropower industry in Nepal was used to rationalise the variation of potential design changes. Using the geometry and operational parameters from an existing design as a benchmark, a two-blade, homogenous, multiphase model was developed and run using the commercial code ANSYS CFX. Initially, it was identified that the jet aim position had a significant effect on the efficiency. A design of experiments’ approach and subsequent analysis of numerical and visual results were used to make design changes that resulted in an improvement in efficiency from 69% to 81%. The design changes maintained the simple profile of the blade, ensuring that the resulting design was appropriate for manufacture in a local workshop.

Abstract Turbine types suit specific ranges of head, flow rate and shaft speed and are usually categorised by specific speed. In the pico range, under 5 kW, the requirements are often different to that of larger scale turbines and qualitative requirements become more influential in selection. Pico hydro turbines can be applied beyond these conventional application domains, for example at reduced heads, by using non-traditional components such as low speed generators. This paper describes a method to select which turbine architecture is most appropriate for a low-head pico hydro specification using quantitative and qualitative analyses of 13 turbine system architectures found in the literature. Quantitative and qualitative selection criteria are determined from the particular requirements of the end user. The individual scores from this analysis are weighted based on the perceived relative importance of each of the criteria against the original specification and selects a turbine variant based on the total weighted score. This methodology is applied to an example of a remote site, low head and variable flow requirement, leading to the selection of a propeller turbine variant or single-jet Turgo turbine for this specification.

This paper proposes a methodology for “design for localisation” that addresses the challenge of designing a product for local manufacture and use, whilst considering the production process availability and the context of the local geographic area. The methodology is derived from a case study of the development of a propeller turbine in Nepal. In the case study, the initial challenge was the absence of a low head turbine that could be manufactured, used and repaired in Nepal. A potential solution from previous academic work was identified however its intended operating environment differed considerably. Through identification of the specific local requirements, the design priorities for individual sub-systems in the new context were developed. Using three examples, design changes driven by improving the ease of manufacture and applicability to the local context are explained. Multiple phases of field and laboratory-based testing were used to validate, adapt and improve the design and its method for implementation. The experiences of the case study lead to three rules for design for localisation using an identified potential solution for a local problem: firstly, to derive local product requirements; secondly to develop solutions appropriate for local manufacturing; and finally, to conduct field-testing phases to ensure the product is suitable for its intended application.

The majority of off-grid pico-hydropower systems use a single turbine and generator, connected directly to an AC network resulting in clusters of isolated, power-limited, single failure-prone networks. The use of inverters has been previously proposed in order to decouple the turbine’s rotational speed from the network frequency in these remote microgrids. This facilitates the use of multiple generators and the creation of expandable, reliable networks with redundancy. This paper presents an inverter controller for this situation, and addresses a combination of challenges that is specific to expandable pico-hydropower networks in geographically dispersed remote communities. Multiple variable-head turbines are connected to a network, whose individual local hydraulic heads vary due to flow changes over the seasons, and the network has no single generator that dominates and no master controller, but instead identical independent controllers that do not communicate. The controller presented here uses an output voltage and frequency droop controller, with inner synchronous reference frame control loops for the fundamental voltage and current. The control coefficients are automatically adjusted to the available local hydraulic head. Simulation and experimental results show that the power is shared amongst generators, proportionally to the locally available power, in steady and dynamic situations. Harmonic compensation loops are proposed: these reduce the output total harmonic distortion (THD) of a single inverter from 9.53% to 1.45% for a non-linear load. Geographically distributed operation in resistive networks is investigated, and the results show that the controller achieves plug-and-play capability for remote off-grid networks with multiple and different pico-hydropower generators.