Electricity Supply Solutions for an Educational Center in Tanzania

The aim of this study was to investigate electricity supply solutions for an educationalcenter that is being built in Chonyonyo Tanzania. Off-grid power generation solutions andfurther optimization possibilities were studied for the case.The study was done for Engineers Without Borders in Sweden. Who are working withMavuno Project on the educational center. The school is set to start operating in year 2015with 40 girl students in the beginning. The educational center will help to improve genderequality by offering high quality education in a safe environment for girls in rural area.It is important for the system to be economically and environmentally sustainable. Thearea has great potential for photovoltaic power generation. Thus PV was considered as theprimary power generation and a diesel generator as a reliable backup. The system sizeoptimization was done with HOMER. For the simulations HOMER required componentdata, weather data and load data. Common components were chose with standardproperties, the loads were based on load estimations from year 2011 and the weather datawas acquired from NASA database. The system size optimization result for this base casewas a system with 26 kW PW; 5.5 kW diesel generator, 15 kW converter and 112 T-105batteries. The initial cost of the system was 55 875 €, the total net present cost 92 121 €and the levelized cost of electricity 0.264 €/kWh.In addition three optimization possibilities were studied. First it was studied how thesystem should be designed and how it would affect the system size to have night loads(security lights) use DC and could the system then be extended in blocks. As a result it wasfound out that the system size could be decreased as the inverter losses would be avoided.Also the system extension in blocks was found to be possible. The second study was aboutinverter stacking where multiple inverters can work as one unit. This type of connectionallows only the required number of inverters to run while shutting down the excess ones.This would allow the converter-unit to run with higher efficiency and lower powerconsumption could be achieved. In future with higher loads the system could be easilyextendable by connecting more inverters either in parallel or series depending on what isneeded. Multiple inverters would also offer higher reliability than using one centralizedinverter. The third study examined how the choice of location for a centralized powergeneration affects the cable sizing for the system. As a result it was found that centralizedpower generation should be located close to high loads in order to avoid long runs of thickcables. Future loads should also be considered when choosing the location. For theeducational center the potential locations for centralized power generation were found outto be close to the school buildings and close to the dormitories.

Elbesparing med pelletkaminer och solvärme i direktelvärmda småhus

The aim of this study was to investigate how electricallyheated houses can be converted to using wood pellet and solarheating. There are a large number of wood pellet stoves on themarket. Many stoves have a water jacket, which gives anopportunity to distribute the heat to domestic hot water and aradiator heating system. Three typical Swedish houses with electric resistanceheating have been studied. Fourteen different system conceptsusing wood pellet stoves and solar heating systems have beenevaluated. The systems and the houses have been simulated indetail using TRNSYS. The houses have been divided in up to 10different zones and heat transfer by air circulation throughdoorways and open doors have been simulated. The pellet stoveswere simulated using a recently developed TRNSYS component,which models the start- and stop phases, emissions and thedynamic behaviour of the stoves. The model also calculates theCO-emissions. Simulations were made with one stove without awater jacket and two stoves with different fractions of thegenerated heat distributed in the water circuit. Simulations show that the electricity savings using a pelletstove are greatly affected by the house plan, the systemchoice, if the internal doors are open or closed and thedesired level of comfort. Installing a stove with awater-jacket connected to a radiator system and a hot waterstorage has the advantage that heat can be transferred todomestic hot water and be distributed to other rooms. Suchsystems lead to greater electricity savings, especially inhouses having a traditional layout. It was found that not allrooms needed radiators and that it was more effective in mostcases t use a stove with a higher fraction of the heatdistributed by the water circuit. The economic investigation shows that installing a woodpellet stove without a water jacket gives the lowest totalenergy- and capital costs in the house with an open plan (fortoday's energy prices and the simulated comfort criteria). Inthe houses with a traditional layout a pellet stove givesslightly higher costs than the reference house having onlyelectrical resistance heating due to the fact that less heatingcan be replaced. The concepts including stoves with a waterjacket all give higher costs than the reference system, but theconcept closest to be economical is a system with a bufferstore, a stove with a high fraction of the heat distributed bythe water circuit, a new water radiator heating system and asolar collector. Losses from stoves can be divided into: flue gas lossesincluding leakage air flow when the stove is not in operation;losses during start and stop phases; and losses due to a highair factor. An increased efficiency of the stoves is importantboth from a private economical point of view, but also from theperspective that there can be a lack of bio fuel in the nearfuture also in Sweden. From this point of view it is alsoimportant to utilize as much solar heat as possible. Theutilization of solar heat is low in the simulated systems,depending on the lack of space for a large buffer store. The simulations have shown that the annual efficiency ismuch lower that the nominal efficiency at full power. Thesimulations have also shown that changing the control principlefor the stove can improve efficiency and reduce theCO-emissions. Today's most common control principle for stovesis the on/off control, which results in many starts and stopsand thereby high CO-emissions. A more advanced control varyingthe heating rate from maximum to minimum to keep a constantroom temperature reduces the number of starts and stops andthereby the emissions. Also the efficiency can be higher withsuch a control, and the room temperature will be kept at a moreconstant temperature providing a higher comfort.

Combined solar and pellet heating systems for single-family houses : How to achieve decreased electricity usage, increased system efficiency and increased solar gains

In Sweden, there are about 0.5 million single-family houses that are heated by electricity alone, and rising electricity costs force the conversion to other heating sources such as heat pumps and wood pellet heating systems. Pellet heating systems for single-family houses are currently a strongly growing market. Future lack of wood fuels is possible even in Sweden, and combining wood pellet heating with solar heating will help to save the bio-fuel resources. The objectives of this thesis are to investigate how the electrically heated single-family houses can be converted to pellet and solar heating systems, and how the annual efficiency and solar gains can be increased in such systems. The possible reduction of CO-emissions by combining pellet heating with solar heating has also been investigated. Systems with pellet stoves (both with and without a water jacket), pellet boilers and solar heating have been simulated. Different system concepts have been compared in order to investigate the most promising solutions. Modifications in system design and control strategies have been carried out in order to increase the system efficiency and the solar gains. Possibilities for increasing the solar gains have been limited to investigation of DHW-units for hot water production and the use of hot water for heating of dishwashers and washing machines via a heat exchanger instead of electricity (heat-fed appliances). Computer models of pellet stoves, boilers, DHW-units and heat-fed appliances have been developed and the parameters for the models have been identified from measurements on real components. The conformity between the models and the measurements has been checked. The systems with wood pellet stoves have been simulated in three different multi-zone buildings, simulated in detail with heat distribution through door openings between the zones. For the other simulations, either a single-zone house model or a load file has been used. Simulations were carried out for Stockholm, Sweden, but for the simulations with heat-fed machines also for Miami, USA. The foremost result of this thesis is the increased understanding of the dynamic operation of combined pellet and solar heating systems for single-family houses. The results show that electricity savings and annual system efficiency is strongly affected by the system design and the control strategy. Large reductions in pellet consumption are possible by combining pellet boilers with solar heating (a reduction larger than the solar gains if the system is properly designed). In addition, large reductions in carbon monoxide emissions are possible. To achieve these reductions it is required that the hot water production and the connection of the radiator circuit is moved to a well insulated, solar heated buffer store so that the boiler can be turned off during the periods when the solar collectors cover the heating demand. The amount of electricity replaced using systems with pellet stoves is very dependant on the house plan, the system design, if internal doors are open or closed and the comfort requirements. Proper system design and control strategies are crucial to obtain high electricity savings and high comfort with pellet stove systems. The investigated technologies for increasing the solar gains (DHW-units and heat-fed appliances) significantly increase the solar gains, but for the heat-fed appliances the market introduction is difficult due to the limited financial savings and the need for a new heat distribution system. The applications closest to market introduction could be for communal laundries and for use in sunny climates where the dominating part of the heat can be covered by solar heating. The DHW-unit is economical but competes with the internal finned-tube heat exchanger which is the totally dominating technology for hot water preparation in solar combisystems for single-family houses.

Pricing and competition in the Swedish retail market for electricity

Sweden, together with Norway, Finland and Denmark, have created a multi-national electricity market called NordPool. In this market, producers and retailers of electricity can buy and sell electricity, and the retailers then offers this electricity to end consumers such as households and industries. Previous studies have shown that pricing at the NordPool market is functioning quite well, but no other study has to my knowledge studied if pricing in the retail market to consumers in Sweden is well functioning. If the market is well functioning, with competition and low transaction costs when changing electricity retailer, we would expect that a homogeneous good such as electricity would be sold at the approximately same price, and that price changes would be highly correlated, in this market. Thus, the aim of this study is to test whether the price of Vattenfall, the largest energy firm in the Swedish market, is highly correlated to the price of other firms in the Swedish retail market for electricity. Descriptive statistics indicate that the price offered by Vattenfall is quite similar to the price of other firms in the market. In addition, regression analysis show that the correlation between the price of Vattenfall and other firms is as high as 0.98.

On equilibrium prices in continuous time

We combine general equilibrium theory and théorie générale of stochastic processes to derive structural results about equilibrium state prices.

Produtividade agregada brasileira (1970-2000): declínio robusto e fraca recuperação

This study explores the productivity performance of the Brazilian economy between 1970 and 1998. We assess how much of the TFP downfall can be explained by some departures from the standard procedure. We incorporate to the standard measure utilization of capacity, changes in the workweek of capital, services of capital from electricity consumption, relative prices distortions, human capital, and investment in specific technology. We conclude that the downfall in productivity is quite robust to those specifications. The only case that presents a marked difference from the standard TFP measure occurs when relative prices of capital are corrected. The implications of this finding are a topic for future research.

Relations between regulation, competition policy and consumer protection in telecommunications, electricity and water supply

The purpose of this article is to discuss the relations between regulation, competition policy and consumer protection these relations in three key sectors of Brazil’s infrastructure: telecommunications, electricity and water supply. A study of the literature points to two general principles. First, the need for consumer protection depends on the “degree of sovereignty” enjoyed by consumers, defined in terms of the cost of consumer organization, consumers’ ability to evaluate services, and the level of competition in each sector. Second, the less sovereignty consumers enjoy the more consumer protection institutions are involved with regulation agencies. The evidence for the Brazilian case apparently corroborates these points. In addition, it is important to stress that consumer complaints in regulated sectors seem to have increased more intensely than in others. The article is divided into three sections. Section 1 presents theoretical elements and aspects of the relations between regulation, competition policy and consumer protection evidenced by international experience. Section 2 analyzes the Brazilian experience and in particular the available statistics on consumer complaints about telecommunications, electricity and water supply, submitted to Fundação Procon-SP during the nineties. The last section points to possible configurations of the institutional relations between competition policy, regulation and consumer protection, showing how the existing configuration of these areas in the three infrastructure sectors discussed confirms that the theoretical framework proposed has reasonable predictive power.

Evolução do conforto doméstico no estado de S. Paulo, 1980-2002: análise quantitativa

É nítida e rápida a popularização da maioria dos bens duráveis de consumo no Estado de São Paulo, nos últimos vinte anos. Colaboram para isso a universalização da oferta domiciliar de eletricidade, água encanada, esgotos, e a tendência ao barateamento dos bens. Entre outros efeitos, tal popularização deteriora a eficácia das escalas de classificação sócio- econômica baseadas na posse de itens de conforto doméstico, suscitando freqüentes revisões e discórdias no interior da comunidade de marketing. Este estudo sistematiza estatísticas sobre situação domiciliar e posse de itens de conforto doméstico no Estado de S. Paulo, e mostra como isso afeta o consumo material e cultural. Finalmente, aponta que é chegada a hora de se usar mais e melhor variáveis como educação, profissão, qualidade do domicílio, tal como se faz em países desenvolvidos, para o entendimento mais pleno das mudanças que implantam no Brasil a moderna sociedade de consumo.

Essays on international prices and the subjacent market structure

Esta tese utiliza a informação contida em preços internacionais para identificar parâmetros de modelos de comércio sob competição imperfeita, desta forma permitindo inferência sobre o comportamento das exportações, sobre os ganhos de troca da abertura comercial e sobre a variedade de bens produzidos domesticamente. Em primeiro lugar, investigamos o repasse cambial, no longo prazo, para os preços praticados por exportadores brasileiros. O foco no longo prazo permite controlar os efeitos da rigidez de preço no curto prazo, de maneira que o repasse incompleto evidencie competição imperfeita com preços flexíveis. Em segundo lugar, calculamos os ganhos de troca de novas variedades de bens importados baseando-nos em estimativas para as elasticidades de substituição desagregadas. Finalmente, qualificamos a ênfase da literatura de comércio em ganhos de eficiência no lugar de ganhos de variedade, demonstrando que a variedade de bens produzidos domesticamente se amplia após aberturas comerciais desde que as firmas tenham uma margem de decisão em bens intermediários ou na qualificação da mão de obra.

Forecasting electricity demand using generalized long memory

This paper studies the electricity hourly load demand in the area covered by a utility situated in the southeast of Brazil. We propose a stochastic model which employs generalized long memory (by means of Gegenbauer processes) to model the seasonal behavior of the load. The model is proposed for sectional data, that is, each hour’s load is studied separately as a single series. This approach avoids modeling the intricate intra-day pattern (load profile) displayed by the load, which varies throughout days of the week and seasons. The forecasting performance of the model is compared with a SARIMA benchmark using the years of 1999 and 2000 as the out-of-sample. The model clearly outperforms the benchmark. We conclude for general long memory in the series.

Forecasting electricity load demand: analysis of the 2001 rationing period in Brazil

This paper studies the electricity load demand behavior during the 2001 rationing period, which was implemented because of the Brazilian energetic crisis. The hourly data refers to a utility situated in the southeast of the country. We use the model proposed by Soares and Souza (2003), making use of generalized long memory to model the seasonal behavior of the load. The rationing period is shown to have imposed a structural break in the series, decreasing the load at about 20%. Even so, the forecast accuracy is decreased only marginally, and the forecasts rapidly readapt to the new situation. The forecast errors from this model also permit verifying the public response to pieces of information released regarding the crisis.

Reinsurance in Brazil: what happened to prices?

Neste estudo investigamos a mudança no Brasil de um mercado fechado monopolista de resseguros para um mercado aberto. O foco tem sido sobre os prêmios, como a queda nos preços foi um dos benefícios mais antecipados da nova estrutura do mercado. Para comparar os preços de resseguro entre mercados o Índice Combinado foi usado. Ao comparar o Brasil ao Resto do Mundo, Índices Combinados significativamente menores foram observados para 2001 - 2007. No período 2008 - 2010, após a abertura, parece ter sido uma convergência dos Índices Combinados com os níveis no mundo. Confirma que os preços de resseguro eram altos no passado, e que ocorreu uma queda nos preços desde a abertura. No entanto estas conclusões devem ser tratados com alguma precaução uma vez que apenas 2,5 anos de experiência está disponível desde a abertura do mercado e outros fatores podem ter influenciado a evolução dos preços observados.