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An Analysis on Energy Balance Scenarios in Rwanda using Energy Systems Model: The Case of Converting Peat to Briquette, DME and Electricity

초록/요약

Rwanda energy balance is predominantly composed by biomass. About 85% of overall primary energy is based on biomass, 11% from petroleum products and 4% from hydro. Only about 16% of all households have access to electricity and the cost of electricity is also very high at about US$0.22 per kWh compared to the average retail tariff of the rest of the region, which is around US$0.10-0.12 per kWh. The per capita electricity consumption is also very low in the region at 30 kWh compared to neighboring countries including Uganda (66 kWh), Tanzania (85 kWh) and Kenya (140 kWh). Biomass is entirely generated from wood; which has created the disappearance of trees in some region of the country. The biggest concern of deforestation is the charcoal demand for cooking. For longtime, the population growth has negatively impacted on the amount of forest covering the country. It is reported that about 99% of households use wood fuel for cooking and mostly people in urban areas prefer to use charcoal as a cleaner fuel than firewood; they also find the utilization of imported petroleum products, such as kerosene and LPG (liquefied petroleum gas), to be comparatively much more expensive. National and international transportation is dominated by roads motor transportation. Petroleum products such as gasoline and diesel are the only fuels used in transportation. They are transported from Mombasa in Kenya via pipeline to Eldoret in Kenya, then by trucks over a long distance to Kigali and distributed in other region of the country. In addition to high inland transport costs from Mombasa, it is reported that oil imports are subject to various duties and taxes and, on average, the retail prices of petroleum products are about 100% higher than acquisition costs at the main supply sources. Motor transportation consumes approximately 75% of the country’s imported petroleum and the remaining 25% are used for electricity generation. For longtime, Rwanda has also depended on hydropower – whose limited capacity relied on a dilapidated network with technical and commercial losses. It is reported that the lack of investment in maintenance of the existing hydropower sector, around 30% of electricity supply has been lost; either in generation or transmission and distribution. Consequently, the electricity demand and supply have become unbalanced; which pushed the government to request the private sector to supply electricity generated from oil thermal power. According to the reports, the shifting to oil thermal power has increased electricity tariffs by over 100%. With belief that, generally, the persistent low-level access to modern energy is attributed to lack of investment in the energy sector; accordingly, the investment in the domestic energy resources use was analyzed for electricity supply security, for alternative energy to reduce wood fuel and petroleum products usage. Peat was identified as main available resource to be converted to fuel through related technology to be used at primary level, along with existing energy technologies. Peat is a widely available resource in Rwanda, although, it has not been utilized at large scale as a fuel. The reports indicate potential peat reserves that amount to 155 millions of tons of dry peat, distributed over an area of about 50,000 ha and equivalent to 500 MW electrical powers supply during 30 years. Peat is known to play an important role in energy production for some countries, such as Finland, Ireland, Sweden, Russia, and various areas of the former Soviet Union. The peat to energy technology utilization was evaluated through four objectives. The first objective was to analyze the chemical components of peat and the produced peat briquette. The cooking performance was also tested along with the greenhouse gas emissions opportunity. The techno-economic was also evaluated to analyze its commercialization. The second objective was basically the techno-economic evaluation of DME and its related environmental impacts. Three major challenges were identified in the Rwanda energy systems, such as electricity demands being nearly equal to the available capacity, costly expenses associated with oil thermal plants, and insufficient investment finances. In this context, the modeling Rwanda energy systems evaluated whether peat would be a good fuel candidate to solve the above challenges the country is facing; it was the third objective in this thesis. The fourth objective related to providing the relevant information in terms of projected cost of generating energy for electricity supply, cooking fuel and motor fuel. The new fuel chains such as peat briquette and DME technologies were evaluated along with the electricity supply technologies to generate the overall energy systems of Rwanda. The Model for Analysis of Energy Demand (MAED) was interlinked with the Model for Energy Supply System Alternatives and their General Environmental Impacts (MESSAGE) to form MAED-MESSAGE. Therefore, MAED-MESSAGE was used through the definition of different energy technologies and its related levels. During a study period that spanned the years of 2013-2045, scenarios involving population and average GDP growth rates, and energy intensity were used for modeling the future energy demand and supply. Charcoal consumption was identified as a main cause of cutting trees. The investigation of economic viability was assessed from raw-peat production to briquetting technologies. The briquettes were made by naturally dried of peat from Bisika, Bahimba, Ndongozi and Nyirabirande bogs, through a rotary pulverizer and a briquette press; they were carbonized into furnace at 450oC to reduce its health effects. The burning rate of peat briquettes made varied from 0.178 kg/hour to 0.222 kg/hour. Ash content varying between 3 and 7.2 % was also observed. The total NPV of US$17.2 million proved investment viability under an 8.3% discount rate; at the same time, the IRR is 19.29%, and the DPP period is between five and six years. Peat briquette proved to reduce the monthly expenses for household to about 30 %. As an alternative to diesel, a techno-economic analysis method was also employed to investigate the economic attractiveness of DME. A DME project of 25 years lifetime proved commercially viable with a net present value of US$16.2 million and an internal rate of return of 14.63%. DME reported to be a good alternative candidate, with a price level of 40% as low, to diesel. The optimization of future energy supply using MAED-MESSAGE reported the important role of peat to energy technology to increase energy supply security. The supply of electricity security margin was observed to be between 32% and 51%, even when oil thermal power was to phase out. Generally, peat-to-power technology was costly competitive compared to the electricity utility price in Rwanda and the region. However, Peat to power technology was identified to be a significant source of CO2 emissions, same as methane gas to power technology. The emission trends increased during the study period as peat power plant planned capacity was fully commissioned. The LCOE of peat to power technology was at US$71.5/MWh including the carbon emission cost, which did not affect its competitiveness of peat to power technology. The emissions opportunity was found on peat briquettes utilization as cooking fuel. Peat briquettes utilization could save 0.05 % of CO2 and more than 99% of CH4 emissions, compared to charcoal emissions. However, unless the CCS technology is applied, the peat-to-DME production showed no potential to offer an alternative to diesel fuel due to its high CO2 emissions. With the CCS application, the GHG emissions could be increased from 74.8gCO2-e/MJ to 78.6gCO2-e/MJ or 9% as high for LHV and reduced from 74.8gCO2-e/MJ to 67.4gCO2-e/MJ or 6% as low for HHV compared to the existing diesel fuel used in motor transport. Because of insufficient potential peat resource volume, the technology of peat to power, peat to briquette, and peat to DME scenarios could not be implemented the same time. It even seemed practically impossible to implement the DME investment along with briquette investment scenarios, because DME investment itself showed to almost deplete the peat resource at the end of study period. Therefore, it would be optional decision for implementing any of these technology scenarios. However, peat to electricity technology could be implemented with DME in combine technology or peat-to-electricity along with peat to briquette.

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목차

Chapter 1. Introduction
1.1 Background
1.2 Overview of Rwanda energy resources
1.2.1 Energy demand and supply
1.2.2 Potential for energy supply
1.2.3 Peat-to-energy in Rwanda
1.3 Research objectives
1.4 Research approach
1.5 Outline of the study
Chapter 2. Literature review
2.1 Energy systems modeling
2.1.1 Bottom-Up energy system models
2.1.2 Top-down energy system models
2.1.3 General aspect of energy system models
2.2 Peat to energy technology
2.2.1 Use of peat as fuel in the world
2.2.2 Peat conversion technology
2.2.2.1 Peat to synthetic fuels
2.2.2.2 Peat to electricity
2.2.2.3 Peat to briquette
2.2.3 Emissions from peat to energy technologies
2.2.3.1 Emissions from peat mining and harvesting
2.2.3.2 Emissions from peat combustion
2.2.3.3 Emissions from briquette
2.2.3.1 Emissions from DME
Chapter 3. Methodology
3.1 Methods of techno-economic analysis
3.2 Modeling framework
3.2.1 MESSAGE model
3.2.1.1 MESSAGE components
3.2.1.2 Data input and model structure
3.2.1.3 Database management
3.2.1.4 Optimization of the model and the results
3.2.1.5 Distribution of investments
3.2.1.6 Own-price elasticities of demand
3.2.1.7 Supply elasticities
3.2.2 MAED model
3.2.2.1 MAED model features
3.2.2.2 Energy demand characteristics in MAED
3.3 Theory and calculations
3.3.1 Cost analysis for fuel chains
3.3.1.1 Raw peat mining and harvesting
3.3.1.2 Peat briquetting process
3.3.1.3 Cost analysis for Dimethyl ether production
3.3.2 Modeling assumptions
3.3.2.1 Electricity demand scenarios
3.3.2.2 Motor fuel demand scenarios
3.3.2.3 Cooking fuel demand scenarios
3.3.3 Greenhouse gas emissions estimation
3.3.3.1 Calculation for emissions from peat mining and harvesting
3.3.3.2 Calculation for emissions from peat combustion
3.3.3.3 Emissions from cooking fuel
3.3.3.4 Calculation for emissions from motor fuel
3.3.4 Modeling Rwanda energy system
3.3.4.1 Economic features
Chapter 4. Results and Discussion
4.1 Techno-economic analysis of fuel chains
4.1.1 Raw-peat production cost analysis
4.1.2 Peat briquette manufacturing
4.1.2.1 Sensitivity analysis of the impact of major inputs on NPV
4.1.2.2 Peat briquettes market viability and implications
4.1.2.3 Assessment of greenhouse gas emissions from peat briquette
4.1.3 Techno-economic analysis of DME
4.1.3.1 Economic analysis
4.1.3.2 Economic assessment of DME usage
4.1.3.3 Sensitivity analysis of DME price level
4.1.3.4 Assessment of greenhouse gas emissions from DME
4.2 Peat to electricity technology and implications
4.2.1 Predicted electricity demand versus potential supply
4.2.2 Cost analysis of electricity generation
4.2.3 Sensitivity Analysis
4.2.4 Forecasted CO2 emissions from energy technologies
4.3 Peat briquette technology and implications
4.3.1 Peat briquette supply scenario
4.3.2 Levelized cost of energy for cooking fuel
4.3.3 Peat briquettes market viability and its impact
4.3.4 Availability of peat resource for briquette production
4.3.5 Greenhouse emissions trends
4.4 Peat to DME technology and implications
4.4.1 Motor fuel demand scenarios
4.4.2 DME supply scenarios
4.4.3 Levelized cost of energy for motor fuel
4.4.4 Viability assessment
4.4.5 Opportunities for greenhouse gas emissions reduction
Chapter 5. Summary and conclusions
5.1 Summary of findings
5.1.1 Techno-economic analysis of fuel chains
5.1.2 Peat to electricity technology and implications
5.1.3 Peat briquette technology and implications
5.1.4 Peat to DME technology and implications
5.2 Conclusion and policy implications
References

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