Enabling the transition to electric cooking in rural Nepali micro hydropower mini-grids

  • William P M Clements

Student thesis: Doctoral ThesisDoctor of Philosophy (PhD)

Abstract

Globally, 2.6 billion people lack access to clean cooking fuels and technologies, 1.8 billion of whom now have access to electricity. Indoor air pollution from biomass cooking accounts for the premature deaths of almost 4 million people every year. Electric cooking has the potential to improve quality of life, reducing health impacts and firewood collection requirements, thus freeing up time for other activities. In Nepal there are 3,300 communities with micro hydropower (MHP) plants which provide reasonably constant renewable power of 10-100 kW to community members, but much of the generated energy is wasted and tariffs are often low, leading to low plant financial sustainability. Electric cooking could increase the usage of MHP generation and thereby increase plant income but, with electric cookers often drawing 1-2 kW, and in communities with hundreds or thousands of residents connected to the mini-grid, all wanting to cook at the same time, the feasibility of widespread adoption of electric cooking is limited.
Electricity as a primary cooking fuel is an unexplored prospect in MHP communities, with only rice cookers and electric kettles prevalent, while the introduction of electric cooking in similar contexts has failed to take the cultural nature of cooking into account by neglecting to capture data on cooking practices or provide sufficient training. In this thesis, the transition to electric cooking in rural Nepali MHP communities is investigated from social and technical viewpoints, collecting data and insights on how to enable community members to integrate electric cookers into their daily practices as much as possible, and evaluating solutions to increase the potential adoption of electric cooking.
Two electric cooking studies trialling induction cookers were conducted, using cooking diaries and MHP electrical system data collection, finding that induction cookers are well received and compatible with most Nepali dishes, but that a total switch to electric cooking is unrealistic, with some fuel stacking inevitable, while cooking was found to coincide with peak community activity, limiting induction cooking scalability to only 10-15 households. An electric pressure cooker (EPC) trial study was conducted to understand the potential of efficient cooking devices and demand-side management measures to increase electric cooking scalability. EPCs were appreciated by participants but generally used only for rice, although 6 kW load peaks for 30 EPCs compared to 8 kW peaks for 15 induction cookers showed increased scalability for lower EPC usage levels. Demand-side management measures reduced peak loads by 10-20 kW through industrial load scheduling agreements and household electricity demand reduction, chosen for implementation due to their simplicity, requiring no extra hardware or control software. The three cooking trial studies contributed datasets of cooking practices, electric cooking energy consumption, MHP electricity demand and generation, and electric cooking load profiles and their contributions to peak community loads.
A techno-economic model of a case study MHP community was created and used to show that a tariff system based on electricity consumption could increase community income from NPR 50,000 to NPR 200,000, while electric cooking would contribute almost NPR 10,000 with only 56 households with electric cookers in the community. Uninformed tariff setting and low generated energy utilisation often leads to insufficient income generation in MHP communities, while previous work has not captured the detailed electricity demand data necessary to construct a model which can estimate electricity usage, resulting income, household payments, electric cooking costs, and contributions of key end uses such as electric cookers and industrial machines to the community load profile. The model was tested by comparison against an adjusted version based on lower detail input data, finding that the detailed data collection conducted was necessary to generate load profiles which adhere closely to measured data and therefore create a useful model.
This thesis contributes the techno-economic model, which can be used to determine equitable and profitable tariff structures for community contexts, simulate demand-side management measures, and inform load planning decisions, including evaluation of the scalability of electric cooking. The model can now be adapted to other similar communities and contexts based on limited input data such as typical daily electricity demand patterns, numbers of households and productive end uses and typical appliances owned, and typical usage patterns for industrial machines.
Even with efficient cooking devices and demand-side management measures in place, widespread adoption of electric cooking is unfeasible without energy storage. A model of an MHP mini-grid integrating centralised and distributed battery energy storage systems using reverse droop control was created, as proof of concept. Electronic load controller frequency setpoint adjustment enabled full battery charging and discharging. A power flows model and household battery sizing model were conceived. Central battery capacities of 135 kWh and 201 kWh were calculated for high usage of 400 induction cookers and 800 EPCs respectively, representing approximate scalability limits without oversizing. Household battery capacities of 1.6 kWh and 0.96 kWh were calculated for enabling high induction cooker and EPC usage, with the corresponding scalability of off-peak charging calculated at 134 and 224 HH batteries respectively. This thesis contributes simplified battery storage sizing models for MHP mini-grid integration.
The techno-economic model showed that all solutions would enable increased electric cooking and improve MHP financial sustainability, with the scalability of high usage EPCs compared to induction cookers calculated at 60 and 40 respectively, confirming that EPCs are more scalable, although induction cookers were deemed more versatile and convenient by cooking trial study participants. However, widespread adoption of electric cookers would require expensive battery storage systems, with payback periods of at least three years, comparable to battery lifetimes, reducing feasibility. The models contributed by this thesis can be used to estimate battery storage system requirements for supporting electric cooking adoption, based on realistic electric cooking modelling validated against measured data, and can evaluate the scalability and economic viability of introducing electric cooking in MHP communities and other contexts, with and without battery storage. This thesis supports Nepali government targets on increasing electric cooking adoption to 25% of households by 2030 and increasing per capita energy consumption by contributing models which can be adapted and used by organisations such as the Alternative Energy Promotion Centre for improving MHP community financial sustainability and enabling electric cooking load planning.
Date of Award6 Dec 2022
Original languageEnglish
Awarding Institution
  • University of Bristol
SupervisorSam Williamson (Supervisor) & Paul W Harper (Supervisor)

Keywords

  • electric cooking
  • micro-hydropower
  • mini-grid
  • Nepal
  • techno-economic modelling

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