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)

Influence of coal properties on the performance of fixed-bed coal-burning braziers

Abstract: Informal fixed-bed coal-burning braziers are used extensively in low-income communities of South Africa for space-heating and cooking needs. An investigation was carried out on the effects of coal moisture content and coal quality on the thermal and emissions performance of domestic coal-burning braziers in three field-procured braziers (with three different air ventilation rates), using the bottom- lit updraft (BLUD) and top-lit updraft (TLUD) ignition methods. Results showed that an increase in coal moisture content (from 2.4 wt.% to 8.6 wt.%) led to 18% and 30% decreases in fire-power when using the TLUD and BLUD methods, respectively. The combustion efficiency increased by 25% with an increase in moisture content. Measured carbon monoxide (CO) emission factors increased with an increase in moisture content, while carbon dioxide (CO2) emission factors remained unchanged. The use of A-grade coal resulted in a 49% increase in PM emissions compared with D-grade coal at high ventilation rates, despite no statistically significant differences (p > 0.05) in CO and CO2 emission factors produced between coal grades

Influence of fire-ignition methods and stove ventilation rates on gaseous and particle emissions from residential coal braziers

Despite extensive electrification of low-income residential areas on the South African Highveld, extensive use is still made of wood and coal as domestic fuels, particularly for winter space heating. In informal settlements characterised by poverty and lacking electrification, coal is combusted in non-standardised, inefficient and polluting metal braziers, colloquially known as imbaulas. Copious emissions from domestic coal fires result in elevated household and ambient air pollution levels well above national air quality limits. Despite the severity of this pollution as a public health issue, emissions data from residential coal-burning braziers are still scarce. Consequently, there is a need to evaluate the emission characteristics of these devices. In this paper, we report on controlled combustion experiments carried out to investigate systematically influences of fire-ignition methods and stove ventilation rates on gaseous and condensed matter (smoke) emissions from informal residential coal combustion braziers. Two methods of stove ignition—conventional bottom-lit updraft (BLUD) and the top-lit updraft (TLUD) (colloquially known as the Basa njengo Magogo) were investigated. Emission factors (EFs) were found to be dependent on fire ignition method and stove ventilation rates. The top-lit ignition method reduces PM10/PM2.5 by 76% to 80% compared to the BLUD method. Carbon monoxide emissions do not change significantly with the ignition method. Pollutant emissions from normal combustion in high ventilation conditions were low compared to pollutants emitted when an oxygen deficient atmosphere was created under low ventilation conditions. High stove ventilation rates resulted in a 50% reduction in PM10/PM2.5 emissions compared to the low ventilation rates. Emissions of gaseous and particulate matter from incomplete combustion can be minimised by design optimisation of the braziers. Ideally, the emissions of condensed matter particles (which form the bulk of emitted particles in residential coal fires) can be reduced through good mixing of emitted gases and air, and by ensuring a long residence time in the high temperature oxygen rich post combustion zone, to allow for complete oxidation. This study is significant in that it presents the first systematic and comprehensive study of factors affecting emissions from coal braziers

Dissemination of free basic electricity in rural settlements

Abstract: This paper evaluates the implementation of the Free Basic Electricity (FBE) programme in the needy South African households. A total of 5 governmental sites were used to assess the implementation of the FBE program; while 165 households were surveyed from 2016-2017 to determine the dissemination and use of FBE. The desktop survey revealed that approximately 1.8 million poor South Africans have access to FBE. Furthermore, tariff relief sets at 50 kWh based on 2001 household energy survey was found to differ per implementing agency, ranging from 20 kWh - 100 kWh. However, no data was available regarding the total number of South African who are energy poor. The survey found that 18% of households are employed, while 82% is unemployed and mainly depend on social grants. Majority of the households cannot afford electricity for cooking and heating, consequently spend over 14% of their income on energy budget which include a mixture of clean and dirty fuels such as wood, coal and paraffin. A total of 15 (9%) households are beneficiaries of FBE; while 91% indicated that they do not know about the tariff relief. Findings from this study suggest the need for an improved public communication strategy, especially in rural areas. It can be recommended that the 50-kWh tariff relief be reviewed to qualify the current household energy needs. Furthermore, enhanced community engagement is recommended in rural settlements to improve clean energy adoption strategies, either energy efficiency or FBE utilization

The effectiveness of solar water heating geysers in South Africa : a review

Abstract : The heating of water for domestic purposes is an important component of human daily activities, especially during cold weather conditions. In South Africa, it is estimated that households spend an average of 40% of their electricity on domestic water heating alone. This alone threatens energy affordability and access due to the high cost of electricity. The South African government seeing that the majority of low-income households do not afford electricity, introduced solar water heating (SWH) geysers as a possible affordable energy alternative technology. The massive roll-out of the solar water geysers began in 2008 managed to install 443 486 SWH geysers. This desktop study is envisaged to evaluate the implementation of the strategy and ends by investigating the effectiveness of the SWH geysers on reducing household grid energy demand between 2009 and 2017. The results of this study will illustrate the effectiveness, failures, successes or future approaches evolving around this technology

The effectiveness of solar water heating geysers in South Africa : a review

Abstract: The heating of water for domestic purposes is an important component of human daily activities, especially during cold weather conditions. In South Africa, it is estimated that households spend an average of 40% of their electricity on domestic water heating alone. This alone threatens energy affordability and access due to the high cost of electricity. The South African government seeing that the majority of low-income households do not afford electricity, introduced solar water heating (SWH) geysers as a possible affordable energy alternative technology. The massive roll-out of the solar water geysers began in 2008 managed to install 443 486 SWH geysers. This desktop study is envisaged to evaluate the implementation of the strategy and ends by investigating the effectiveness of the SWH geysers on reducing household grid energy demand between 2009 and 2017. The results of this study will illustrate the effectiveness, failures, successes or future approaches evolving around this technology

Emission factors of domestic coal-burning braziers

We present experimental results of emission factors from a suite of domestic coal-burning braziers (lab fabricated and field collected) that span the possible range of real-world uses in the Highveld region of South Africa. The conventional bottom-lit updraft (BLUD) method and the top-lit updraft (TLUD) method were evaluated using coal particle sizes between 20 mm and 40 mm. Emission factors of CO2, CO and NOx were in the range of 98–102 g/MJ, 4.1–6.4 g/MJ and 75–195 mg/MJ, respectively. Particulate matter (PM2.5 and PM10) emissions were in the range 1.3–3.3 g/MJ for the BLUD method and 0.2–0.7 g/MJ for the TLUD method, for both field and lab-designed stoves. When employing the TLUD method, emission factors of PM2.5/PM10 reduced by up to 80% compared with those when using the BLUD method. Results showed the influence of ventilation rates on emission factors, which reduced by ~50% from low to high ventilation rates. For energy-specific emission rates, the combined (3-h) PM10 emission rates were in the range of 0.0028–0.0120 g/s, while the combined average CO emission rates were in the range of 0.20– 0.26 g/s, with CO2 emission rates in the range of 0.54–0.64 g/s. The reported emission factors from coal braziers provide the first comprehensive, systematic set of emission factors for this source category, and fill a major gap in previous efforts to conduct dispersion modelling of South African Highveld air quality. Significance:  The study provides the first comprehensive, systematic set of emission factors from coal braziers. The study fills a major gap in previous efforts to conduct dispersion modelling of South African Highveld air quality. Results have implications for stove design and lay the groundwork for improvements in the design of existing coal braziers. Results have implications for understanding the potential health impacts of condensed matter emissions from coal braziers