title: Botswana electricity sector planning and CO₂ emissions reduction through solar PV in office buildings

authors: Mukwaso, Simasiku Titus

abstract: Coal is the most abundant energy resource in Botswana, with a total reserve of about 212 billion tones. Currently 600 MW of electricity is generated from coal and 160 MW is generated from imported diesel fuel. With rising electricity demand in the future it is planned that the extra generation will come from coal, however there is mounting pressure to reduce CO₂ emissions during electricity generation. The main challenge Botswana is facing, from an electricity generation point of view, is to find alternate and economic clean energy technologies for electricity generation in order to reduce CO₂ emissions. With little natural renewable energy resources other than the sun, the most obvious alternative to coal generation is solar generation. Botswana is blessed with about 21MJ/m² /day of average solar radiation with over 3200 hours of sunshine per year.

In order to reduce emissions Botswana has set targets of 15 percent and 25 percent electricity generation from renewables (most likely solar) by 2025 and 2030 respectively, as well as replacing planned coal generation expansion with Coal Bed Methane (CBM) in future. Furthermore, the government is also considering using Carbon Capture Storage (CCS) to reducing CO₂ emissions from coal generation, as an alternative to widespread solar.

With these thoughts in mind this study investigates; (1) generation options for reducing CO₂ emission in the electricity sector of Botswana through to 2030, (2) the economic feasibility of using solar PV in Botswana office buildings, and (3) the amount of CO₂ emissions reduction that can be achieved if the solar PV generation was rolled out to many office buildings in Botswana, both commercial and government buildings.

From the electricity sector planning study compared to business as usual, a 44.6 percent CO₂ emission reduction in Botswana is possible through uptake of 25 percent solar PV and replacing diesel with CBM. With additional application of CCS to coal, emissions can be reduced further to 82.1 percent. However, the additional 37.5 percent emissions reduction relies heavily on CCS a developing technology with high system costs.

From the solar PV study, two DC solar PV systems were determined to be the most economical system with Net Present Costs (NPC) of US$ 1,840,105.75 and US$ 473,394.53, compared to two AC solar PV systems with NPC of US$ 2,068,279.31 and US$ 587,673.24. The levelized costs for DC solar PV system without inverter and batteries is 0.47 US$/kWh which is 14.9% less than the AC solar PV system with inverter without batteries at 0.54 US$/kWh. Similarly, the DC solar PV system with batteries is 1.82 US$/kWh, 3.8% lower as compared to levelized costs for AC solar PV system with batteries and inverter at 1.89 US$/kWh.

Lastly, it is estimated that between 12 percent and 39 percent CO₂ emissions reduction is possible in Botswana by rolling out installation of DC solar PV systems in 11564 commercial and government office buildings throughout Botswana.

text: Botswana electricity sector planning and CO₂ emissions reduction through solar PV in office buildings Coal is the most abundant energy resource in Botswana, with a total reserve of about 212 billion tones. Currently 600 MW of electricity is generated from coal and 160 MW is generated from imported diesel fuel. With rising electricity demand in the future it is planned that the extra generation will come from coal, however there is mounting pressure to reduce CO₂ emissions during electricity generation. The main challenge Botswana is facing, from an electricity generation point of view, is to find alternate and economic clean energy technologies for electricity generation in order to reduce CO₂ emissions. With little natural renewable energy resources other than the sun, the most obvious alternative to coal generation is solar generation. Botswana is blessed with about 21MJ/m² /day of average solar radiation with over 3200 hours of sunshine per year.

In order to reduce emissions Botswana has set targets of 15 percent and 25 percent electricity generation from renewables (most likely solar) by 2025 and 2030 respectively, as well as replacing planned coal generation expansion with Coal Bed Methane (CBM) in future. Furthermore, the government is also considering using Carbon Capture Storage (CCS) to reducing CO₂ emissions from coal generation, as an alternative to widespread solar.

With these thoughts in mind this study investigates; (1) generation options for reducing CO₂ emission in the electricity sector of Botswana through to 2030, (2) the economic feasibility of using solar PV in Botswana office buildings, and (3) the amount of CO₂ emissions reduction that can be achieved if the solar PV generation was rolled out to many office buildings in Botswana, both commercial and government buildings.

From the electricity sector planning study compared to business as usual, a 44.6 percent CO₂ emission reduction in Botswana is possible through uptake of 25 percent solar PV and replacing diesel with CBM. With additional application of CCS to coal, emissions can be reduced further to 82.1 percent. However, the additional 37.5 percent emissions reduction relies heavily on CCS a developing technology with high system costs.

From the solar PV study, two DC solar PV systems were determined to be the most economical system with Net Present Costs (NPC) of US$ 1,840,105.75 and US$ 473,394.53, compared to two AC solar PV systems with NPC of US$ 2,068,279.31 and US$ 587,673.24. The levelized costs for DC solar PV system without inverter and batteries is 0.47 US$/kWh which is 14.9% less than the AC solar PV system with inverter without batteries at 0.54 US$/kWh. Similarly, the DC solar PV system with batteries is 1.82 US$/kWh, 3.8% lower as compared to levelized costs for AC solar PV system with batteries and inverter at 1.89 US$/kWh.

Lastly, it is estimated that between 12 percent and 39 percent CO₂ emissions reduction is possible in Botswana by rolling out installation of DC solar PV systems in 11564 commercial and government office buildings throughout Botswana.

year: 2017

title: Littoral sediment budget and beach morphodynamics, Pukehina Beach to Matata, Bay of Plenty

authors: Phizacklea, David Jonathan Dominic

subjects: coast changes

abstract: The Pukehina-Matata coastal sector is one of the least studied parts of the Bay of Plenty coastline. Currently this section of coast is in a stable, tending towards erosive, condition, with historical erosion of 0-0.2 m/year.
Sediment mineralogy reflects the high input of quartzo-feldspathic material into the beach-dune-nearshore system. For the Otamarakau-Matata sector much of the sediment is provided from fluvial sources, predominantly the Waitahanui, Pikowai, and Herepuru streams, although the total stream input in this area is only 3,000 to 7,000 m³ per year. The sources of beach sand from Town Point to Otamarakau includes some erosion of catchment material, supplemented by littoral drift, erosion of submarine rock outcrops in the Town Point-Otamarakau region, and possible onshore reworking of pre-Holocene sediments.
The greywacke gravels present within the littoral system, especially between Rodgers Road and Pukehina, are relict deposits, which are presently active within the beach-dune-nearshore system due to the small volume transfers of sandy sediments. Their original source, is suggested as from marine erosion of Castlecliffian sediments, such as exposed in the coastal cliffs at Matata.
Net littoral drift is suggested as bi-directional from a centre-point near Otamarakau, to both the north-east along Pukehina Spit, and to the south-west towards Matata. Some counter-drift occurs between the Tarawera River mouth and Matata, and along the tip of Pukehina Spit, with nourishment of this area by the Waihi estuary.
Nearshore sedimentary-morphodynamic units show that the nearshore and inner-shelf at Town Point, and from southern Pukehina Beach to Otamarakau, is characterised by the presence of numerous rock outcrops, which are responsible for the coarse sands and relatively higher carbonate abundances in this area.
Sediment volumes within the beach-nearshore system, and alongshore transfers between sectors of the coast are small, with annual net littoral drift estimated as 15,000 m³ at Matata. Diabathic processes are considered to dominate, with the limit of significant onshore-offshore sediment transport no more than 12 m, and a parabathic limit of less than 6 m.
The net change in sediment volume for the entire beach system within the Pukehina-Matata coastal sector between 1989 and 1993, produced a calculated deficit of sediment of 90,570 m³. In comparison a longer-term change, between 1978 and 1993, showed a sediment surplus of 218, 560 m³. Over the Pukehina-Matata coastal sector these volume changes are reasonably small and their variability reflects both the dynamic nature, and the delicate state of equilibrium, of the beach-dune-nearshore system. The derived littoral sediment budget shows that in order to balance the inputs and outputs within the system approximately 27,400 m³ of annual onshore
sediment transport must occur. Current sand extraction at Otamarakau has resulted in a decline in the beach sediment volumes between Otamarakau and Pikowai, with this sector in a sediment deficit. Although natural processes mask the true impacts, the increased sand extraction rate of 36,000 m³ per year is liable to further deplete the beach-dunenearshore system. However, in the short-term these effects are unlikely to be immediately noticeable.

text: Littoral sediment budget and beach morphodynamics, Pukehina Beach to Matata, Bay of Plenty The Pukehina-Matata coastal sector is one of the least studied parts of the Bay of Plenty coastline. Currently this section of coast is in a stable, tending towards erosive, condition, with historical erosion of 0-0.2 m/year.
Sediment mineralogy reflects the high input of quartzo-feldspathic material into the beach-dune-nearshore system. For the Otamarakau-Matata sector much of the sediment is provided from fluvial sources, predominantly the Waitahanui, Pikowai, and Herepuru streams, although the total stream input in this area is only 3,000 to 7,000 m³ per year. The sources of beach sand from Town Point to Otamarakau includes some erosion of catchment material, supplemented by littoral drift, erosion of submarine rock outcrops in the Town Point-Otamarakau region, and possible onshore reworking of pre-Holocene sediments.
The greywacke gravels present within the littoral system, especially between Rodgers Road and Pukehina, are relict deposits, which are presently active within the beach-dune-nearshore system due to the small volume transfers of sandy sediments. Their original source, is suggested as from marine erosion of Castlecliffian sediments, such as exposed in the coastal cliffs at Matata.
Net littoral drift is suggested as bi-directional from a centre-point near Otamarakau, to both the north-east along Pukehina Spit, and to the south-west towards Matata. Some counter-drift occurs between the Tarawera River mouth and Matata, and along the tip of Pukehina Spit, with nourishment of this area by the Waihi estuary.
Nearshore sedimentary-morphodynamic units show that the nearshore and inner-shelf at Town Point, and from southern Pukehina Beach to Otamarakau, is characterised by the presence of numerous rock outcrops, which are responsible for the coarse sands and relatively higher carbonate abundances in this area.
Sediment volumes within the beach-nearshore system, and alongshore transfers between sectors of the coast are small, with annual net littoral drift estimated as 15,000 m³ at Matata. Diabathic processes are considered to dominate, with the limit of significant onshore-offshore sediment transport no more than 12 m, and a parabathic limit of less than 6 m.
The net change in sediment volume for the entire beach system within the Pukehina-Matata coastal sector between 1989 and 1993, produced a calculated deficit of sediment of 90,570 m³. In comparison a longer-term change, between 1978 and 1993, showed a sediment surplus of 218, 560 m³. Over the Pukehina-Matata coastal sector these volume changes are reasonably small and their variability reflects both the dynamic nature, and the delicate state of equilibrium, of the beach-dune-nearshore system. The derived littoral sediment budget shows that in order to balance the inputs and outputs within the system approximately 27,400 m³ of annual onshore
sediment transport must occur. Current sand extraction at Otamarakau has resulted in a decline in the beach sediment volumes between Otamarakau and Pikowai, with this sector in a sediment deficit. Although natural processes mask the true impacts, the increased sand extraction rate of 36,000 m³ per year is liable to further deplete the beach-dunenearshore system. However, in the short-term these effects are unlikely to be immediately noticeable.

year: 1993

title: Low copper levels measured in the aortic wall of New Zealand patients with non-syndromic ascending thoracic aortic aneurysm

authors: El-Gamel, Adam

subjects: Ascending aortic aneurysm

abstract: OBJECTIVES: Studies in animals have shown causal relationships between copper (Cu) deficiency and the development of thoracic aortic aneurysms (TAAs) [1, 2]. Cu deficiency is widespread in New Zealand (NZ) soils; the high soil pH from the use of lime fertilizers reduces the bioavailability of Cu for grazing animals and growing plants; this, in turn, reduces Cu availability in the NZ human food chain. Our study is a pilot study to explore associations between Cu and TAA. We measured Cu levels in aneurysmal aortic tissues in patients undergoing Bentall procedures and non-aneurysmal aortic tissue from coronary artery bypass graft patients. METHODS: Aortic samples were collected from 2 groups of patients during elective open-heart surgery over 4 months between November 2017 and February 2018. The groups were a TAA group, patients with non-syndromic aortic aneurysm and without the bicuspid aortic valve or known infectious or inflammatory condition (ANEURYSM; n = 13), and a control coronary artery bypass graft group (CONTROL; n = 44). Standardized digested dry tissue weighed samples were analysed from both groups. Tissue extraction of trace elements was carried out using HCl-H2O2 digestion and a highly sensitive analytical technique, inductively coupled plasma mass spectrometry-used to measure elemental concentrations. RESULTS: Cu concentration (mean ± SD) was significantly lower in ANEURYSM (3.34 ± 0.16 µg/g) when compared to the CONTROL group tissues (4.33 ± 0.20 µg/g) (dry weight; mean ± SD; Student's t-test, P < 0.05). Over 46% of the Aneurysm patients were Maori and live in a geographically Cu-deficient NZ territory. CONCLUSIONS: Cu deficiency may play a role in the development or progression of non-syndromic ascending aortic aneurysms in NZ. Maori patients are more at risk as they commonly live in rural NZ, dependent on locally grown nutritional sources. Further studies are required to confirm this exciting finding and to establish cause and effect relationship.

text: Low copper levels measured in the aortic wall of New Zealand patients with non-syndromic ascending thoracic aortic aneurysm OBJECTIVES: Studies in animals have shown causal relationships between copper (Cu) deficiency and the development of thoracic aortic aneurysms (TAAs) [1, 2]. Cu deficiency is widespread in New Zealand (NZ) soils; the high soil pH from the use of lime fertilizers reduces the bioavailability of Cu for grazing animals and growing plants; this, in turn, reduces Cu availability in the NZ human food chain. Our study is a pilot study to explore associations between Cu and TAA. We measured Cu levels in aneurysmal aortic tissues in patients undergoing Bentall procedures and non-aneurysmal aortic tissue from coronary artery bypass graft patients. METHODS: Aortic samples were collected from 2 groups of patients during elective open-heart surgery over 4 months between November 2017 and February 2018. The groups were a TAA group, patients with non-syndromic aortic aneurysm and without the bicuspid aortic valve or known infectious or inflammatory condition (ANEURYSM; n = 13), and a control coronary artery bypass graft group (CONTROL; n = 44). Standardized digested dry tissue weighed samples were analysed from both groups. Tissue extraction of trace elements was carried out using HCl-H2O2 digestion and a highly sensitive analytical technique, inductively coupled plasma mass spectrometry-used to measure elemental concentrations. RESULTS: Cu concentration (mean ± SD) was significantly lower in ANEURYSM (3.34 ± 0.16 µg/g) when compared to the CONTROL group tissues (4.33 ± 0.20 µg/g) (dry weight; mean ± SD; Student's t-test, P < 0.05). Over 46% of the Aneurysm patients were Maori and live in a geographically Cu-deficient NZ territory. CONCLUSIONS: Cu deficiency may play a role in the development or progression of non-syndromic ascending aortic aneurysms in NZ. Maori patients are more at risk as they commonly live in rural NZ, dependent on locally grown nutritional sources. Further studies are required to confirm this exciting finding and to establish cause and effect relationship.

year: 2022-09-09