by Daniel Kerr, August 2023
Technical sustainability is one of the critical components contributing to the success of mini-grids for electrification in developing countries. Regardless of electricity source, size of grid or other sustainability factors, technical sustainability impacts the ability of the mini-grid to service the needs of the connected customers, businesses and organisations. Focusing specifically on Sub-Saharan Africa, the SIGMA project has recently released a review of technical sustainability of mini-grids, and assessed the factors that contribute to mini-grids being technically sustainable, as well as the non-technical factors that impact technical sustainability.
Elements of Mini-Grid Technical Sustainability. Image: authors
Mini-Grid System Design
Decisions made at the design stage can impact the sustainability of a mini-grid project throughout its lifetime. This can also be described at path-dependency: making the right decisions early on in terms of fuel source, network topology, monitoring equipment and installers can set a mini-grid on a sustainable course for years to come, or conversely, introduce significant issues in the operational phase should these factors not be considered. Sizing of plants and demand estimation have come up consistently in the literature as issues affecting the technical sustainability of mini-grids. Oversized generating plants create demand/supply mismatches and operational issues (Almeshqab and Ustun 2019, Schnitzer et al. 2014), whereas undersizing of plants can lead to accelerated degradation of generation infrastructure (Arnaiz et al 2018). Imported systems being used over locally-designed systems can introduce additional challenges, and a lack of local expertise can lead to unsustainable decisions being made, such as in Drinkwaard et al. (2010) where inappropriate turbines for local conditions were installed in mini-hydro plant. Demand estimation is also a problem over the lifetime of the project: data on demand growth in mini-grids is challenging to come by, due to unpredictable factors such as population growth and migration. Tariff structures can also affect demand growth: low tariffs can promote inefficient consumption, leading to plants reaching capacity quicker than expected (Ulsrud et al, 2019). Smart systems can go some way to managing these issues operationally, but need to be planned for at the design stage: Shakya et al (2019) report a case in Bhutan where a mini-hydro system was prevented from overloading at peak times using a colour-coded grid health system. However, as Fowlie et al observed, “Even the smartest technology can be ineffective if it requires human intervention and the incentives of the agents are not perfectly aligned with system success” (Fowlie, et al., 2018, p13). Non-technical factors at the design stage can also have an effect on technical sustainability: Lillo et al (2015) describes a case in Peru where the communities were not consulted prior to the installation of DC mini-grids, and DC appliances were extremely hard to find in that rural region, leading to significant user dissatisfaction, and a corresponding drop in willingness-to-pay and utilisation. Finally, construction quality is vital in the design and implementation phase. The literature has a wide variety of examples where poor-quality installations led to equipment failures in operation; where contractors for installations were inexperienced and local capacity was limited, and where weak regulatory frameworks allow for the prioritisation of the number of installations over the quality and durability of installations (Derks and Romijn 2019, Arnaiz et al 2018).
Mini-Grid Operations and Maintenance
Sustainable operations of mini-grids is a critical factor to overall technical sustainability for mini-grid systems. Maintenance challenges, and how well these are overcome, also contribute to the overall reliability, adequacy and affordability of electricity supply in mini-grids. In terms of system availability, supply predictability and duration of supply are common measures of technical sustainability in the literature. Making sure that the design specifications of the system are met with a consistently-available level of supply is critical in ensuring the satisfaction of the connected consumers. Reliability is another factor affecting consumer satisfaction with the supply of electricity from mini-grids, as well as the sustainability of the system from a technical perspective: supply interruptions, from various causes, hinder the ability of systems to deliver electricity services. System adequacy, that is the ability for the system to meet peak and average demands, can be a root cause of other issues such as voltage excursions and interruptions that impact technical sustainability. If systems are not sufficient to meet the demand of the connected consumers, then failures will be more common. Arnaiz et al (2018), Shyu (2013) and Ngowi et al (2019) all highlight issues with supply adequacy affecting the performance of mini-grids. The importance of regular maintenance on mini-grid components is also highlighted in the literature, as well as the challenges of conducting this maintenance. Well-maintained systems are reliable systems, and Valer et al (2017) notes that reductions in failures through better servicing leads to cost savings overall. However, maintenance itself can be a challenge: a lack of trained local technicians, a lack of in-country supply chains for spare parts or repairs, and short-term maintenance contracting have all been identified in the literature as factors affecting the ability to maintain mini-grid systems well.
The SIGMA Framework for Technical Sustainability
The final part of this review on technical sustainability led us to assess the existing frameworks for determining the technical sustainability of a mini-grid, and what indicators have been used for assessing this. There have been a number of attempts made to quantify technical sustainability and create assessment frameworks for analysing the technical sustainability of mini-grids, with the World Bank/ESMAP Multi-Tier Framework (MTF) being one of the more famous examples (ESMAP, 2015), and has been applied widely since 2015. Katre & Tozzi (2018) took the MTF a step further, and disaggregated technical sustainability into different services, proposing service levels for each of these to constitute a technically sustainable system. It is clear from our review that there is no consensus regarding the indicator-based analysis of technical sustainability of mini-grids or energy access projects. Studies have not always considered the data requirements for such evaluations, and challenges with quantitative data limit the replicability of assessment frameworks as well. This has led us to propose a new framework for assessing the technical sustainability of mini-grids. The ability of existing indicators to measure technical sustainability is not always clear. For example, the comparison of consumption with the regional average used in Rahmann et al. (2016) or the prescriptive thresholds for different tiers used in the MTF framework are difficult to justify. Second, data availability limits the application of very data intensive frameworks. A framework that can provide a reasonable picture of the technical sustainability need not be too complex or impose too many demands on data. Third, the framework must consider long-term perspectives and respect renewability and future demand growth. Fourth, the framework should be easy to use and interpret, and should allow comparison across different mini-grids at a specific time and at different points in time. The SIGMA Framework uses five equally-weighted indicators and nine data inputs to produce a comparable, relative score for technical sustainability for mini-grids in Sub-Saharan Africa. The framework and indicators are laid out below:
SIGMA Framework for Technical Sustainability. Source: Authors
|Measures||Indicators||Weight||Base (=1)||Standard (=3)||High (=5)|
|Adequacy||Ability to meet demand now||60%||Barely meeting the demand||Meeting most of the time||Always meeting the demand|
|Reserve margin||40%||0-5% margin||10-20% margin||25% margin|
|Availability||Duration||50%||Only for limited or restricted time||Available during specified hours||On demand (anytime)|
|Peak capacity||50%||Basic lighting and phone charging||Supply to support commonly used appliances||Supply to support aspirational needs|
|Reliability||Average number of interruptions||40%||<1 per week||<1 per month||<2 per year|
|Average duration of interruption||60%||<10 % of time||<5% of the time||<1% of time|
|Renewability||% of renewable supply||100%||<50%||50-80%||80-100%|
|Quality||Average number of voltage excursions||50%||<10 per day||<5 per day||<1 per day|
|Frequency variations||50%||+/- 2Hz||+/- 1 Hz||+/- 0.5 Hz|
Scoring system for the SIGMA Framework. Source: Authors
The final score for a mini-grid in this framework will be out of 25, but for ease of appreciation, this should be multiplied by 4 to be a score out of 100. Mini-grids scoring 20 will be considered as poorly sustainable, those between 20 and 60 are moderately sustainable and those with scores above 60 will be considered as sustainable. Conclusions The technical sustainability of mini-grids in Sub-Saharan Africa is affected by a wide variety of factors, some inherent to the technical design and construction projects, and some inherent to the operation of mini-grid projects. Technical sustainability impacts other forms of sustainability within mini-grid projects as well, while non-technical factors, particularly economic and social factors, can impact the ability of a mini-grid project to be technically sustainable. In the operational phase, maintaining the supply of the mini-grid is critical to the technical sustainability of the system, which includes maintaining the availability of supply, the adequacy of supply, and the reliability of supply. These factors all feed into consumer satisfaction, which is maintained if the system can keep up with both the demands of the users (both domestic and commercial) at the time of installation, and the aspirational demands of users both current and potential into the future.
If you’re interested in reading the full article, our working paper “On The Technical Sustainability Of Mini-Grids In Developing Countries: A Comprehensive Review Of Literature” is available from the Resources -> Working Papers section of our website.
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