Protocols for thermal and emissions performance testing of domestic fuels and stoves

M.Phil.The combustion of fuels in poorly designed cookstoves is a major anthropogenic source of atmospheric emissions with severe environmental and health implications. It is widely acknowledged that these challenges are best addressed with the development and dissemination of clean cookstoves. Widely used stove testing protocols (UCB Water Boiling Test and variants) are often single task-based and not representative of real-world uses or likely combinations of the manner in which fuels, stoves and pots may be used. The hypothesis of this study is that a stove testing procedure that provides for testing of stove/fuel/pot combinations, in a sequence of heterogeneous tests, provides a better representation of thermal performance and emissions than existing protocols based on prescribed fuels and fuel loads, and single tasks. The study aimed to develop and evaluate a set of testing protocols for determining thermal efficiency and emissions performance of domestic fuels and cooking devices to satisfy the rigorous performance specifications expected for claims under the Clean Development Mechanism (CDM) carbon trading market. The Heterogeneous stove Testing Protocol (HTP) was developed and documented as a complete set of standard operating procedures (SOPs), using a template derived from the Desert Research Institute (DRI), Reno, Nevada, and used for performance evaluation of fuel/stove combinations. The effect of pot size on the performance of two paraffin wick stoves and a pressurised paraffin stove was assessed and was found not to be a major factor, which affected thermal efficiency only at the high power setting. Power setting was found to influence the thermal efficiency and combustion performance of all stoves tested, indicating the need for assessment of the devices across the full range of power settings (where feasible). The HTP was also employed in characterising the combustion performance of coal stoves, using three different ignition methods, giving qualitative and quantitative results. Compared to the bottom-lit up-draft (BLUD) ignition method, the Basa njengo Magogo, also referred to as the top-lit up draft (TLUD) method, proved to be a better method of coal fires ignition, in terms of reduced CO:CO2 ratio and less smoke generation than in conventional braziers. The bottom-lit down-draft (BLDD) ignition method, incorporated in the SeTAR prototype coal stove, was found to be effective in fuel utilisation and improved combustion efficiency compared to the TLUD and BLUD methods, with CO:CO2 emission factors below 1% for 230 minutes. A number of parameters employed by the Water Boiling Test (WBT) were examined and compared with the HTP (e.g. turn-down ratio; simmer process; hot-start phase; use of standardised fuels and test pots). The HTP was found to provide more representative performance data over a wide range of use scenarios, the equivalent of providing performance curves rather than the minimum and maximum performance points provided by the WBT. The findings of this study have shown that the Heterogeneous stove Testing Protocol is consistent, robust, and transportable; making it a valuable tool for stove design improvements, and for the assessment of stoves under voluntary and compulsory carbon markets

Analysis of household energy uses in Mubuga informal settlement, Gitega, Burundi

Abstract: This paper presents an analysis of household energy uses in an informal settlement in Mubuga, Gitega, Burundi. At the time of the survey, the informal settlement was not connected to the main electricity grid. A survey of 100 households was conducted and data were collected through structured and open interviews. Of the interviewed households, 84 percent indicated that they used fuelwood as a primary energy source for cooking. About 94 percent used charcoal for commercial (barbecuing/grilling meat) purposes and 22 percent used it for domestic cooking. For lighting, kerosene accounted for 55 percent followed by candles (36%) and rechargeable lanterns (10%). Households in Mubuga used multiple fuels to meet their basic energy needs. It is therefore recommended that intervention models that advocate for the use of multiple fuels should be promoted in the area, as it allows households to choose freely energy sources from a suite of options

Heterogeneous stove testing methods for the evaluation of domestic solid-fuel cookstoves

Abstract: More rigorous and detailed test procedures are desirable to determine the effect of various design modifications on the performance of fuel/cookstove combinations, and to optimize their performance. This research paper investigated the effect of a novel heterogeneous testing method to evaluate the performance of domestic solid fuel/cookstove combinations. The water-heating test (WHT) and the ‘hood’ method were used as the basis of the tests with additional variants of fuel load, power setting and method of ignition. The experimental cookstoves included a typical brazier (Imbaula), a new type Mozambique ceramic cookstove, the baseline Mozambique metal cookstove, and the bottom-lit down-drafting (BLDD) coal cookstove. Results showed that a heterogeneous testing method provides more representative performance data over a wide range of usage scenarios, the equivalent of providing performance curves rather than the minimum and maximum performance points provided by single tasked based methods. This novel heterogeneous testing method generates robust and diagnostic results with which to compare fuel/cookstove technologies. Cookstove designers and programme managers who wish to improve the design of existing and new cookstoves, and to promote efficient fuel/cookstove technologies based on sound laboratory tests can use the principles explored in this study

Size distribution of nano particles from residential fixed-bed coal combustion

Abstract: Particle size distribution (PSD) from domestic coal combustion is an important parameter as it affects air quality, climate modelling, and health. There is limited information in the literature on particle size distribution from residential fixed-bed coal combustion processes. This study aimed to investigate the influence of coal combustion phases (ignition, flaming, and coking) on PSD of fine and ultrafine particles. Fine particle emissions from combustion of D-grade type coal (Ø 40 – 60 mm), in a lab-fabricated coal brazier (imbaula), were monitored using a NanoScan Scanning Mobility Particle Sizer (SMPS). Experiments were carried out using the reduced smoke top-lit updraft method, colloquially known as the Basa njengo Magogo (BnM) method. Particles from the top-lit updraft (TLUD) showed an ultrafine geometric mean diameter centred at approximately 110 nm for the ignition phase, 55 nm for the pyrolysis/ flaming phase, and 33 nm for the transition phase. The particle mode diameter rapidly increased during the ignition phase (145 nm) and gradually decreased during the flaming phase (35 nm) and the transition phase (31 nm)

Public participation in technological innovation : the case of the Tshulu stove development programme

Abstract: The design of products for developing communities often excludes the end-users in the decision making process. The study aims to investigate public participation and engagement in the design and development of the Tshulu woodstove. Results of this research point to the need for improved communication between citizens and technical experts, as well as for narrowing the gap between the designer and the user by encouraging meaningful engagement and inclusion. Bottom-up approaches ensure sustained participation of the public, in turn increasing a sense of ownership in the product. These results have implications for energy policy and improved cookstove programmes for developing communities

Design and performance evaluation of wood-burning cookstoves for low-income households in South Africa

Abstract: Many cookstove programmes implemented around the world aimed to reduce fuel consumption and pollutant emissions through the dissemination and adoption of improved cookstoves. A study was carried out for the design of wood-burning cookstoves for low-income households in South Africa by employing user-centred design and co-design/cocreation approaches. Six designed variants of the biomass stove were constructed. Water-heating and emissions tests, using black wattle wood, were conducted to evaluate them for thermal and emissions performance. The large hopper stove with two secondary air inlets ranked highest, with best performance regarding thermal and emissions parameters. It outperformed the small hopper stove in time to boil, heat flux and firepower, although the latter had higher thermal efficiency values..

A comprehensive review on small-scale combustion technologies in Southern Africa, what is known, done and emergent knowledge gaps?

Abstract: This is a review paper written with the intention to shed light on continued reliance on high polluting energy sources in the Southern Africa. Tn developing countries the use oflow cost fuels including coal, wood, pellets, charcoal and cow dung remains an obstacle in ensuring the right to clean air. Tn this study, several stove to fuel combustion technologies researches, were reviewed for similarities/ commonalities and differences. The review highlights on critical health and environmental effects associated with burning of solid fuels using inefficient cookstoves. The review deepens the understanding on various clean energy interventions and policy formulation in several countries within the Southern Africa Development Communities (SADC) region. Studies indicated the development of stove alone will not be enough in enhancing or reducing air pollution, but emphasis shall be put on stove to fuel combination. Findings also suggest a lack of clear or practical policy intervention to restore household indoor air quality, while single policy intervention proven inadequate in many studies. In sub-Saharan region, policy intervention focuses on energy switch thus from traditional solid fuels to modern energy resources namely electricity and liquid petroleum gas (LPG). This approach is not feasible given the difficulties in electricity generation and supply system, housing infrastructure and cost implication. Tn conclusion, policies which support energy stacking present a viable solution to improved indoor air quality

Emissions of tar balls from domestic coal burning braziers

Abstract: On the central-plateau of the South African Highveld, domestic coal combustion is associated with the release of carbonaceous aerosols often produced as dendritic carbonaceous particles and tar balls. However, very few studies have been conducted to validate this contribution. Combustion of coal in low-income settlements is done using self-constructed devices (predominantly braziers) known as imbaulas. Combustion characteristics in these devices are influenced by fire ignition methods. The most common ignition method in South African Highveld areas is the bottom-lit updraft (BLUD) relative to the less favoured Top lit-updraft (TLUD) ignition technique. Aerosols samples were collected using Nucleopore filters combustion phases (ignition and pyrolysis). The JSM 5800LV SEM at the University of Pretoria and the Vega3 LM at the University of Johannesburg were used to observe particle morphologies from coal-burning fires. Both instruments were equipped with energy dispersive spectroscopy (EDS), which provides the possibility to analyse particle chemical compositions. Tar balls were identified in both ignition methods (BLUD and TLUD) and in pyrolysis (stage I and II). When sampling close to the fires (at ignition and pyrolysis stage I), the filter material rapidly clogged and a continuous layer of liquid/ tarry substance coalesced and covered the entire filter membrane, with some pores completely closed. At the 5 m exit point, micrographs showed distinct particles morphologies, including giant spherical organic particles that had condensed as the exhaust stream cooled. Perfectly spherical giant tar balls were observed in ageing smoke from smouldering combustion conditions typical of poorly ventilated BLUD fires. The spherical tar ball particles were found as individual spherical particles and as aggregates forming diffusion accretion chains. It is hypothesised that spherical organic particles may have been formed by the ejection of liquid tar droplets (pyrolysis stage I products of coal burning) from the pores of the burning coal, followed by rapid thermal transformation upon passing through the flame or glow zone of the fire

The potential and prospects of improved cookstoves (ICS) in Zimbabwe

In Zimbabwe, alternatives to grid electricity are being sought in the light of limited electricity supply and under-performance of major electricity generation plants following the economic meltdown affecting the country since the mid-1990s, triggered by the Economic Structural Adjustment Programme (ESAP), and more recently due to political instability. Extensive black-outs routinely up to 12 hours per day and even for several days are common in some areas. Consequently, the majority of households continue to rely substantially on wood fuel to meet their basic daily energy needs. Yet the provision of modern energy services and technologies to these households does not seem to be a priority for national energy policy makers. Although improved cookstoves (ICS) are in greater use in rural areas than urban settlements of Zimbabwe, their potential remains largely unexploited. This research aims to highlight the marked potential and current prospects of improved cookstoves in rural and urban communities of Zimbabwe. Ultimately, this research will better inform policy makers, government, academia and the public about cookstove technologies with reduced fuel use, reduced energy costs, and user friendly capacity to improve health in rural and urban communities

Assessment of free basic electricity and use of pre-paid meters in South Africa

In 2000, the African National Congress (ANC) through its election manifesto, made promises to provide free basic services to all poor South Africans. This was later quantified as 6 000 litres of water and 50 kWh of free basic electricity (FBE) monthly per household. Regarding the issuance of FBE, qualifying residents were registered and had to agree to a pre-paid meter being installed. It is argued that the quantity of free basic electricity provided to poor households is inadequate to meet basic needs and improvement of the quality of life. Conversely, there has been resistance to installation and use of pre-paid electricity meters, especially in townships around Johannesburg. Although prepayment systems have been proposed as innovative solutions to the problem of non-payment and affordability in utility services, the use of such mechanisms is still controversial. This paper reviews and assesses free basic electricity and the use of pre-paid electricity meters in South Africa. It also contributes to the on-going debate on FBE and prepayment systems. Recommendations are given on creating viable and stable institutions to curb uncertainties in the provision of electricity services, and methods for identifying changes in aggregate welfare resulting in the adoption of pre-paid electricity meters. Information from this article can be useful for policy-making purposes in other developing countries facing resistance in marketing, dissemination and installation of pre-paid meters