RENEWABLE ENERGIES IN NAMIBIADr. Klaus Dierks
FUTURE DEMAND FOR RENEWABLE ENERGIES
The world is becoming increasingly technology-driven. In its quest for conquering new frontiers of scientific knowledge, human kind is adopting tools that are technology- centric. In all this, energy is a key determinant.
Indeed, energy today plays a key role in deciding levels of development. Per capita consumption of energy is now seen as a measure of economic growth and social progress of individuals, societies and nations.
For equitable development of nations across the world, it is essential that access to and appropriate availability of energy sources should be guaranteed to all. However, with nearly half the world's population surviving on less than two US Dollars a day and a third on less than one US Dollar a day, access to and availability of energy sources continue to elude many a developing nation.
The situation is compounded by the fact that the majority of the rural population in developing nations, especially in Africa, is still dependent on traditional fuels. This at best meets basic human requirements, but does not improve the quality of lives of the poor and marginalised.
Therefore, to ensure equitable development within and among nations, we have to work towards equitable and sustainable access to and availability of appropriate energy sources, with a heavy claim on environmentally friendly renewable energies.
In the era of globalisation, attaining this should not be impossible. Indeed, globalisation offers immense possibilities of developed and developing nations working together in the energy sector to their mutual advantage. Developed countries have access to technology, financial resources and expertise while developing countries offer an expanding market for energy sources.
Economic liberalisation and globalisation have led to an increasing demand for energy - to run industry, to create infrastructure and to meet rising domestic requirements. This has further strengthened the case for partnership in the energy sector.
We in Namibia, determined to keep pace with the rest of the world and ensure rapid socio-economic development, have taken several significant steps in the energy sector. Extensive power sector reforms have been undertaken and a regulatory mechanism established to optimise the electricity sector, for fixing tariffs and ensuring quality supply. There is no cap on foreign direct investment in power generation.
We in Namibia set eyes on cleaner energies: According to Namibian environmental legislation which is enshrined in the Constitution of the Republic of Namibia (Art. 95), environmental considerations, especially the promotion of renewable energies, shall prevail in all energy projects.
For adequate. equitable and sustainable energy development, we have to focus on the agreed principles of collective endeavour as laid down in the Rio Declaration on Environment and Development, 1992. The first principle of the Declaration states: "Human beings are at the centre of concern for sustainable development". In this spirit it has to be concluded that the number one priority for the development of sustainable energy for all is to extend the access to commercial energy services to the two billion people who do not have it now. And, to the almost two billion people who, it is estimated, will come into this world in the next two decades. Renewable Energy Sources (RES) are environmental clean sources with additional economic and social benefits. A country like Namibia has abundant renewable energy sources like solar, wind, wave and biomass. By 2020 these resources could contribute up to 20% of the national electricity production. Within the next 10 years, technologies like wind, solar hydro and biomass could become economically viable without any subsidies.
Success in meeting the energy requirements for these four billion people over the next two decades should be regarded as the first test of sustainability of our collective global energy development efforts. This is an opportunity and a challenge - for developed and developing nations alike - to establish environmentally sustainable energy systems for the "Twenty-first Century".
The "Rio Declaration" further says: "All states and all people shall cooperate in the essential task of eradicating poverty as an indispensable requirement for sustainable development in order to decrease the disparities in standard of living and better meet the needs of the majority of the people of the world. The special situation and needs of developing countries, particularly the least developed and those most environmentally vulnerable, shall be given priority".
Any development agenda, whether global, national or corporate, therefore, should be framed in mind these principles that form, what can be described as the "global ethics" of development.
People-centred energy goals should be fundamental to energy business in the Twenty-first Century. This will call for comprehensive national, regional and global policy initiatives to encourage reform, augment infrastructure, upgrade technologies and introduce new technologies. Above all, they have to balance environment as well as development concerns of different economies in harmony with their unique economic and social as well as environmental requirements.
Energy concerns across the world are marked by a certain amount of variance in priorities. Developed nations are seized with environmental implications of energy concerns. On the other hand, developing nations are focussed on ensuring that their peoples have access to basic minimum tools for securing their livelihood, including access to appropriate energy supply. But, even developing nations cannot escape environmental concerns. Many people in developing countries are suffering from ecological stress. Even after a decade of declining poverty in many nations, 1,2 billion people lack access to clean water and hundreds of millions breathe unhealthy air. The sign of ecological decline ranges from deforestation and desertification to the extinctions of many animal species. Environmental degradation is worsening many natural disasters like earthquakes and floods. Population growth has led people to settle in flood prone valleys and unstable hillsides, where deforestation and climate change have increased the vulnerability of disasters like hurricanes. The arctic ice cap has already thinned by 42 percent and 27 percent of the world's coral reefs have been lost.
The choice is whether to move forward rapidly to build a sustainable economy or to risk allowing the expansion in human numbers, the increase in greenhouse gas emissions, and the loss of natural systems to undermine the economy. Also Namibia had to make this choice. Therefore, Namibia made renewable energies a case of high priority.
Before the industrial revolution, firewood and coal were the main sources of energy. As late as 1890 oil constituted a mere 2 % of the energy market. But as oil proved to be more favourable for heating and lighting, and many other industrial applications were implemented, fossil oils grew by a factor of 50 % from 1890 to 1910.
Many of the renewables like wind power, solar thermal energy, photovoltaics and energy from biomass follow the same growing development path as oil did more than a hundred years ago. Wind turbines have for instance gone through an annual cost reduction of about 10 % between 1980 and 1996. Unit cost for wind power is still higher than for many conventional sources of energy. This is mainly due to the unpredictable and variable nature of wind power production in general. Bur, for some applications the renewable energy technology is already competitive. Power production from biomass in the USA has gone through a similar development from 250 MW to approximately 9000 MW during the 1980s. This production capacity is expected to reach 25 GW in 2010.
During 1976-88 the production costs for photovoltaic panels were reduced by 15 % annually. They have followed a traditional cost development curve in which the costs are reduced by 20 % when production volume is doubled.
It is foreseen that in the near future, renewables will only cover niche applications, but as technology matures and costs are reduced they will increasingly compete with fossil and nuclear energy. The growing significance of renewable energy might be illustrated by reviewing strategies of large international petroleum companies. A common strategical change among many of the companies is that they tend to redefine their role from suppliers of fossil fuels only, towards a variety of energy sources in the market, renaming themselves as energy companies. British Petroleum is, for instance, involved in solar energy. The same applies to Shell Ltd. The "sustained growth" scenario is based on expectations related to the commercial development of the different sources of energy. The scenario reveals that natural gas will play an increasingly important role in the next 20 years. After 2025 renewables will contribute significantly due to technological development and cost reductions while at the same time depleting reserves lead to higher prices for oil and gas. Solar, wind and biomass are expected to increase market shares from 10 % in 2020 to possibly 50 % in 2050 (in the EU the target is 12 % renewable energies by 2010).
Oil, coal and gas will be the dominant energy sources still for many years. Among the greatest challenges will be to find other fuels for transport vehicles, cars, ships, aeroplanes etc. For the developing countries the Shell scenario means an increased consumption of 40 million barrels per day in 2020. This corresponds to 5 times the daily production of Saudi Arabia or 8 times the North Sea production. Shell expects unknown innovations in energy production. Among these "surprises" may be artificial photosynthesis or the use of heat from magma in "mother earths" interior. Nuclear fusion is not considered to be among these innovations.
In another scenario named "Dematerialisation" it is foreseen that more fundamental changes in society leads to reduced energy consumption. Extensive use of information technologies create less need to transport goods and people. Dramatically increased fuel efficient cars are examples of this "Dematerialisation" scenario.
The first windpower park (or even parks because three sites have been identified in the initial planning studies)(the first in sub-Saharan Africa) is under design in Namibia (10 MW to 20 MW for Lüderitz). The new Namibian Electricity Act, No. 2 of 2000, makes provision that the transmission operator (NamPower) is under obligation to take the windpower for a fixed tariff which has to be regulated by the Namibian "Electricity Control Board (ECB)". After implementation of the "Single Buyer" principle, the situation will, however, change. The Government of the Republic of Namibia has decided to make the state owned Namibian enterprise NamPower the "Single Buyer". The ECB, however, has still to regulate the tariff structures of the Single Buyer after the completion of the comprehensive Tariff Study which was commissioned by the ECB (completion of the tariff study is expected towards end of 2001).
Windpower is world wide the most advanced and commercially available of all renewable energies. Windpower is getting cheaper and more efficient through new technologies by the day and are a very logical solution for the Namibian energy market. Various studies reveal that the cost of windpowered electricity will further decrease from today's 4,7 US cents/kWh to a level below 3 US cents/kWh by 2013. This will make windpower competitive with all today's new generating technologies.
A wind turbine (Wind Energy Converter: WEC) converts a portion of the kinetic wind energy into electricity. Wind turbines may be grouped by the orientation of the shaft: horizontal axle - the most common - and vertical axle.
A horizontal axle turbine consists of tower, nacelle (machinery house) and turbine blades. The nacelle contains gearbox, generator, brakes, control system and turning motors. The nacelle orients itself according to the wind direction, either by means of electric motors or the wind itself.
Vertical axle wind turbines do not need to be orientated according to wind direction. Another advantage is that the machinery house is placed on the ground, which again reduces the cost of the tower, installation and maintenance. In spite of this, vertical axle turbines have not yet gained commercial success. This is due to the cyclic loads the blades experience as the turbine rotates, which in many cases have caused material fatigue. However, with the aid of technological development and economy of scale a niche may yet be found for this turbine design.
It is paramount for the cost effectiveness of the wind turbines to be located at sites with favourable wind climate. Since the majority of modern wind turbines are connected to a grid, most of the eclectricity produced can be utilised. It is therefore logical to exploit each good site in the most optimal way, in order to achieve a low cost per KWh produced, erecting wind turbines in groups, known as wind farms. This practice also reduces the cost of infrastructure such as civil infrastructure and grid connection. The ground covered by the turbines is of the order of 1 % of the total area of a wind farm, and therefore other activities may be combined with wind energy production.
The cost of a wind farm is dependent on the wind climate, by the investment cost and the interest rate. By the end of 1997 a total of 7 800 MW was world wide installed, approximately 4 800 MW in Europe (at the end of 1999 it was already more than 4 000 MW in Germany and Spain reaches the 2 000 MW by the end of the year 2000). With only a few large projects under development in the USA , this market seems to have stagnated, and developments in India have almost stopped completely. A large growth in commercialisation of MW-scale turbines seems to be taking place, and they are increasingly being used in of-shore projects. The White Book on renewable energy from the EU Commission estimates 40 000 MW of wind power in Europe by 2010 (with a reduction in energy costs from wind power of at least 30%).
In the last 15 years the specific investment per unit swept area has been halved. At the same time the performance and efficiency has increased significantly. These developments have reduced the cost of wind power to a level that is on the verge of being competitive with electricity from fossil fuels. In the future "green" taxation can improve the competitiveness of wind power as well as other renewables. Further cost reductions are anticipated by making improvements in the following areas:
- Development of tools for more accurate siting will increase the power production from the installed turbines;
- Better design methods may give advanced blades with better performance and longer life time;
- Development of lighter and more elastic constructions will reduce material costs;
- In most cases wind speed increases with the height above ground, and increased size of the turbine (now already up to 3 MW) therefore increases the power density;
- Optimisation of the power output calls for operation at variable speed, which is not compatible with a fixed frequency on the produced electricity. By means of advanced power electronics this obstacle will be overcome;
- Simplification of the design, i.e. gearfree designs, may reduce mechanical losses.
Price for wind power:
P = (r+m)C/Wf
r = annual equivalent interest rate
m = annual maintenance cost as fraction of the investment costs
C = Investment costs
(r+m)C = annual costs
h = 8760 hours per year
W = capacity (kW)
f = capacity factor, that is the fraction of the year, the wind turbine yields production at full capacity
h/wf = annual production
All forms of energy, including renewable energy, have some impact on the environment. Wind energy causes low frequency noise, and as a rule individual turbines should be placed 300 m from buildings. In the case of a wind farm this distance should be increased to 1 km. Advanced aerodynamic design is crucial for noise minimisation. Some people consider the silhouette of a wind turbine an asset to the landscape, others don't. Medieval windmills are now under monument protection, wind turbines will be maybe after 300 years.
New technological developments (Kvaerner ASA) have resulted in the development of large two-blade turbines and a 3 MW prototype. Other developments (ABB Kraft AS) have resulted in a solution found for static (too low voltage) or dynamic (transient voltage fall/flicker) in a low voltage distribution grid. Both are common problems, particularly if a windpower plant is planned on the outskirts of the distribution grid. Instead of costly grid reinforcement, the solution for the wind power plant under these conditions should be a diesel generator for periods of low windspeed, a converter with battery to control frequency and voltage, a load to spend surplus effect and a controller for the whole system.
Energy yield is measured in terms of kWh/m**2. A long shaft is compensation for the wind deviation aerodynamic torque which has to be balanced and softened by the main shaft torque. Flicker will be reduced by more units (for instance: 600 kW units in place of 1,3 MW units: a 66 kV line is better than 11 kV in order to accommodate an installed capacity of 20 MW).
New developments like ABB etc. have advantages and disadvantages. The 'No-gearbox-solution' is not according to the wind format. It requires new structures, bigger generators and DC generation with high cost of converters for AC. With higher power output (3 MW) you need higher structural costs: W**2 = Support /Structure**3. 750 kW turbines are optimised. Higher power turbines are beneficial where space is restricted, not in Namibia (also crane is a problem: 300 t): for 48 m (rotor speed: 24 rpm and max wind speed: 55 m/s and mean wind speed 8,5 m/s: Lüderitz: 7,5 m/s) blade diameter and total nacelle: 27 t mass!. The tower is structurally designed according to Ultimate Limit State (Theory of Plasticity) for a wind speed of 250 km/h (70 m/s). Nordex specifies: If you double capacity, the infrastructural costs will not double, but: stronger forces on structure mean more risk.
Also the problem of lightning resulted in new concepts for protection (not very relevant for Lüderitz). The wind blade tips are constructed from aluminium and connected to the hub with a metal wire, the first main bearing is pre-stressed for good contact between inner and outer shells and the lightning current is conducted directly from the base of the bearing to the tower.
A good relationship between demand and wind power production is essential and will ultimately leads to reduced transmission losses in the grid connection line.
Nordex: N43/600; N50/800; N60/1300; N80/2500 (80=diameter of blades; 2500 [kW].
Wind energy is the cheapest way to generate 'green' energy.
ABB has developed a new generator which will increase production from wind power stations and small hydropower stations. The efficiency has been increased by 20%, and the need for maintenance has been reduced by 50%. A new transmission technology has been developed and will greatly reduce the constraints with a varying frequency from wind farms etc.
ScanWind (a Norwegian company with technology resources from Kvaerner, Aker and ABB) has developed a 3 MW wind power station and the first is now sold to Vattenfall, Sweden. Another contract with the Nord Trondelag Utility (Norway) will be signed later 2000. The commission of the wind power station is expected at the end of this year. The latest technology development from Kvaerner, Aker and ABB has been put into this new type of wind power plant. The cost per KW has been cut by 25% compared to conventional types in the range of 600-1500 KW. The research was supported by the Research Council of Norway and NVE.
In pursuit of the global trend towards the supply of cleaner energy, which is a high priority of the Government of the Republic of Namibia, NamPower in conjunction with the Namibian Ministry of Mines and Energy and the Electricity Control Board (ECB) investigated the construction of a pilot wind park in the vicinity of Lüderitz. During the pilot phase, the wind park will generate between 3 and 10 MW and will be later expanded to as much as 20 MW. This project will also be a step towards achieving the goals of the Namibian White Paper on Energy Policy which aims at Namibia being able to produce 100 % of peak energy demands and 75 % of its energy total demands within its borders by the year 2010.
After careful analysis and the necessary investigations of obvious environmental impacts by an Environmental Investigation Assessment (EIA)(with investigated impacts on vegetation, landscape, birds and socio-economic considerations), it was decided that the Grosse Bucht near Lüderitz was the most acceptable location for the installation. The proposed construction site lies along a ridge top, and covers an area of approx. 2 km² with the centre of the area located approx. 10,5 km south-south-east of Lüderitz.
The initial project will comprise 5 to 6 Wind Energy Converters (WECs) with an output of approx. 3 MW. This will later be extended to a capacity of 10 MW. The WECs comprise towers 30 m high onto which the WECs are mounted driven by three bladed propellers of 40 m in diametre rotating at a speed of 25 rpm. The individual WECs will be spaced at approx. 50 to 60 m apart. If the pilot project is successful, the project will be expanded to as many as 32 WECs to generate as much as 20 MW.
NamPower will also build a 66 kV power line to connect the wind park to the national grid.
It can be expected that the first Namibian wind farm will be commissioned during 2002.
BACKGROUND: PHOTOVOLTAIC (SOLAR) RENEWABLE ENERGY
Namibia has one of the highest solar radiation regimes in the world. It is therefore logical to make use of the abundance of photovoltaic energy, and in fact this is done in the last forty years or so. Solar energy is increasingly used for off-grid electrification in the vast rural and until independence neglected areas in the country. The first two villages have been totally energised by solar power (with Indian donor assistance), namely Spitzkoppe village and Shianshuli in the Caprivi Region. With increasing efficiency and new photovoltaic technologies solar power will be continued to be used in Namibia.
The photovoltaic (PV) effect, that is, the physical phenomena transforming light directly to electrostatic energy, was first discovered by the French physicist Edmund Becquerel in 1839. He observed that illumination of two identical electrodes in a low-conductivity electrolyte gave rise to an electric voltage between them. When light is absorbed in a semi-conductor an electric voltage is created, and if an external circuit is connected to the semi-conductor the voltage will drive a current through the circuit. The absorbed energy has thus been converted to electricity. The ratio between generated electric energy and irradiated energy is the efficiency of the PV cell.
The first PV cells were made from selenium in the last century, and they had an efficiency of 1 - 2 %. Research in the 1920's and 30's laid the theoretical foundation for today's PV technology. Towards the end of the 1940's a new method, Czochralski-growth, was developed for producing mono-crystalline silicon of high purity. The space programmes in the 1950's and the development of the semi-conductor electronics industry were also important milestones in the development of PV technology.
1839: Becquerel discovers the photovoltaic effect.
1954: The first silicon photovoltaic cell is developed in Bell laboratories.
1958: The first satellite with photovoltaic power supply.
1966: CdS/Cu2O thin voltaic cell.
1974: The first amorphous silicon cell.
1983: the first photovoltaic installation above 1 MW.
1985: The first photovoltaic cell with more than 20 % efficiency.
1989: The first tandem cell with more than 30 % efficiency in concentrated sunlight.
Most PV cells are made from silicon. With the exception of oxygen, silicon is the most common material on earth. It is usually refined from quartz sand. However, a number of complicated processing stages are necessary in order to produce silicon of sufficient purity for use in PV cells.
Crystalline Photovoltaic Cells
Mono-crystalline PV cells are commercially available with efficiencies approaching 20 %. In the laboratory, silicon cells with efficiencies close to the theoretical limit, 29 %, have been demonstrated. An efficiency of 20 % might seem low compared to, for example, hydro-electric power with a nearly 100 % efficiency. However, efficiency is primarily a way for researchers and producers to compare different cells. For the consumer the ratio price/electricity output and suitability for the specific weather conditions at the site are important factors. The theoretical limit of 29 % is due to the physical properties of the solar radiation.
Most mono-crystalline PV cells are made from thin wafers that are sawn from solid ingots. Poly-crystalline cells are easier to make, and thus cheaper. As the efficiency of poly-crystalline cells is only marginally lower than that of mono-crystalline ones, poly-crystalline cells are of greater commercial interest.
The thickness of the silicon wafers is 0,3 - 0,5 mm. This gives adequate mechanical strength while providing sufficient thickness for complete absorption of the sunlight, which requires approximately 0,2 mm. However, the market for PV panels has increased to a level where pure silicon has become a scarcity factor. In this context it ought to be pointed out that thin film solar cells use only a fraction of the silicon a traditional cell uses.
The annual global sales of PV energy solutions are approaching 150 MW, passing the 200 MW mark this year (2000). Japan alone is targeting more than 4600 MW PV energy by the year 2010.
The most common materials used in PV cells are:
Mono-crystalline silicon (Si): 29 % (theoretical efficiency): modules: 100 cm**2:
efficiency: 15-18 %;
Multi-crystalline silicon (Si): 22 % (theoretical efficiency): modules: 100 cm**2: efficiency: 12-18 %;
Amorphous silicon (a-Si): 27 % (theoretical efficiency): modules: 1000 cm**2: efficiency: 5 - 8 %;
Gallium arsenide (GaAs): 31 % (theoretical efficiency);
Copper indiumseleinde (CIS): 27 %;
Cadmium telluride (CdTe): 31 %.
Batteries are an important part of solar systems. Only NiCd-type batteries are used.
Scan-Wafer, which owns the Subsidiary SOLENERGY AS is now the world's largest producer of silicium-wafers for solar cells. ScanWafers new capacity is 50 MW annually (12 million wafers annually), while the next on the list, the German company Bayer Solar produces 34 MW annually. Solenergy AS has together with Namibian (main shareholder) and South African business (minimum shareholding: 5-10%) counterparts (Northern Electricity) plans to put up an assembly plant for solar cells in Tsumeb, Namibia. Another subsidiary of ScanWafer will start production of solar cells in Narvik, Norway next year. The background for the increased production of silicium wafers is a dramatic expansion of the market in Europe, Japan and also Africa.
BACKGROUND: BIOMASS IN RENEWABLE ENERGIES
Also bioenergy has started its advent in Namibia. The first biogas plants (again with Indian donor assistance) are in operation.
Bioenergy is energy from the burning of biomass or a derivative of biomass. Biomass is based on all sorts of biological material: fuelwood, manure, agricultural waste. The derivatives include vegetable oil, ethanol and gas from anaerobic decomposition. The burning of waste can also be included in the term bioenergy. The most common use is directly as heat, but biomass may also be used to fuel engines or turbines to produce electricity.
The burning of biomass releases the same amount of CO2 into the atmosphere as the wood has bound when growing. Sustainable use of bioenergy does not give a net increase in release of the greenhouse gas CO2. Combustion of bio-fuels typically gives 20 - 40 % lower emissions of NOx than fossil fuels, and emissions of soot and particles from larger biofuelled heating plants are comparable to those from oil fuelled plants. Due to the low sulphur content of wood (0,05 %) the emissions of CO2 are insignificant.
Historically, bioenergy has been our most important energy source. It was therefore not a coincidence that the first engines constructed by Rudolf Diesel in 1893 were designed to run on vegetable oils. At that time, few if any, could imagine the impact that petroleum products would have on energy use in the 20th century.
Today bioenergy covers 15 % of the world's energy demand and is the most important energy source for half the world population. Bioenergy has a dominant position for the poorest people in the world, who are dependent on woodfuel for cooking and heating. However, cooking over an open fire makes use of only 5 % of the energy in firewood, and consequently the workload of collecting firewood may in many instances be reduced by introducing more efficient stove-technology.
Types and Sources of Biofuels
Remains from forestry and agriculture, such as deciduous trees, felling residues and thinnings result in un-refined biofuels, like fuelwood, chips, barks and straw. Prior to incineration, usually in larger boiler plants, the processing of the raw material is limited to drying and cutting into manageable sizes. The moisture content is the most important parameter deciding the calorific value of solid biofuels. Bioenergy can be generated by steam production, energy rich waste from other sources becomes also an energy resource. Such a plant can run on a variety of fuels: bark from woodroom, chips from discarded logs, waste paper and industrial waste. The fibre sludge from their own effluent treatment plant is pressed to a dry solid content of approximately 50 %, while the biogas from the same plant can be utilised. The boiler is of the fluidised bed type, with the dust removed by an electrostatic precipitator.
Instead of using unrefined firewood for private use, two-chamber furnaces for optimal combustion and energy output can be used. The heated air mixed with the smoke (secondary air) in the second chamber ensures all particles and gases such as CO will burn completely, leaving only clean ash. There is no catalyst that can be destroyed by using improper kinds of fuel, and little maintenance is needed. Modern design combined with easy installation and use, makes the furnaces well suited for family dwellings.
Another method is the use of low emission incinerators for the combustion of solid fuels. It has a silo which stores fuel to be used over several days. The base of the silo is V-shaped so that the fuel rests against two tilted fireproof base-walls. Preheated primary air is injected through a number of nozzles, and an intense combustion volume is created at each nozzle. the size of the base is 8 m**2 with a height of 5 - 10 m. The concept gives a high fuel tolerance and flexibility due to the top loading system. The incinerator accepts wood powder, straw, timber, paper and carton, even when mixed together.
Refined Solid Biofuels
The production of charcoal, briquettes, pellets and powder raises the fuel costs, but the advantages obtained usually outweigh this:
- high specific energy content, giving lower transport and storage costs;
- a homogenous fuel makes it easier to regulate the combustion process;
- the fuel is more stable during storage and less degradable over longer periods of time;
-the furnace, heat exchangers and gas treatment systems can be simpler and cheaper;
- oil burners can be converted to biofuels.
The moisture content is the most important parameter determining the calorific value of solid biofuels. as a rule-of-thumb the calorific value may be calculated according to the formula H=5,32-6,02*m/100 (kWh/kg) where m is the moisture content in %.
Charcoal is produced by a thermo-chemical process (pyrolysis) in which heat is used to drive off volatile material, and the primary products are: gas (light hydrocarbons, CO, CO2 and water vapour), oils (heavier hydrocarbons and tars) and charcoal. Charcoal burns very evenly with little smoke, and is used both for cooking in large parts of the world and as a reducing agent in the metallurgical industry.
If the biofuel is compressed to blocks with a diameter of less than 20 mm, the blocks are called pellets. Pellets are easier to handle than briquettes, but put more stringent requirements to the raw material. Pellets may be handled by similar techniques as fuel oil, and oil burners may be converted to pellet-firing by simple means. Conversion to bio-pellets may therefore be implemented as a short term measure for reducing CO2-emissions (combined free-standing stove for kerosene or pellets: the unit burns the fuels either separately or in combination, having two separate combustion chambers).
Wood-powder is produced by milling dry wood into particles smaller than 1 mm. In order to obtain good combustion characteristics a fraction of the powder should consist of particles smaller than 0,2 mm.
Liquid biofuels may substitute liquid fossil fuels. The transport sector is the most important market, but substitution of fuel oil in other sectors may also be of interest in certain circumstances. There are several different types of liquid biofuels: alcohols, vegetable and animal oils and esterified oils.
In agriculture, the food industry, sewage treatment and waste processing, wet organic biomass can be treated by anaerobic digestion. Several types of reactor concepts have been developed for anaerobic treatment of sewage sludge, manure and organic waste.
Anaerobic digestion of biomass is a microbial process where carbohydrates are broken down to CH4 and CO2. This is a process occurring naturally, but contained in a reactor the reaction products may be collected and used. Depending on the reaction conditions the methane share may vary from 40 to 70 %, with 50 % being normal. The calorific value of the gas is typically about 5 kW/m**2.
Land-filling sites are not only unpleasant and occupy space but they also emit the greenhouse gas methane. The gases are smelly and can self-ignite. The gas can either actively pumped or just piped from the bottom of the heap. The excess humidity in the gas is extracted, the gases are automatically analysed and then burned for heating purposes or to run machinery. The main advantages are the flexibility and environmental aspects: less emission of NOx and CO, burning of harmful methane.
Bioenergy from Waste
The increasing volume of waste from households and many industries has become an escalating environmental problem. Waste may be looked upon as an energy resource which together with traditional forms of recycling provides solutions to avoid large landfills.
By advanced control of the fuel feed and combustion, the concept allows for significantly lower emissions than conventional designs, over a wide range of thermal loads. due to the improved combustion process, only simple gas cleaning such as lime addition and textile filters is necessary. The combustion process can handle aluminium waste and waste containing ash, such as ooze or slime, and it can also run on 100 % plastic fuel.
Power Production based on Bioenergy
Biomass may be used in several ways to fuel power stations. Using much of the same technology as for coal it can be used to fuel steam power plants (Van Eck Power Station in Windhoek). Through gasification processes biomass can be used in gas turbines an consequently in combined cycle (gas and steam) plants and striling engines.
BACKGROUND: HYDRO POWER AND RENEWABLE ENERGIES
Demands, planning and management: environmental issues. There are three types of demands: planning, pre-investment phase, construction phase and operating constraints. The baseline data collection covers many fields: full EIA with monitoring and mitigation. Public hearings (very early information of public are very important: Owner (future operating company) should do this with avoidance of referee/player syndrom: ECB should lay down the condition of the process). Furthermore: Biodiversity research, planned public health program and socio-economic issues.
1. Erosion control, prevent deforestation;
2. Pollution control;
3. Socio-economic impact;
4. Land allocation and access plan;
5. Quarries/borrow pits, transmission line corridor;
6. Vegetation in dam area to be cut down in order to minimise "greenhouse" (Methane) effect;
7. Landscaping, site restoration;
8. Occupational health program;
9. Compensation and resettlement.
1. Riparian flow/downstream flow requirements;
2. Long-term monitoring;
3. Catchment management plan (sediment management);
4. Reservoir operation plan including sediment handling techniques;
5. Royalties/profit sharing with local communities.
Hydrology and water resources (water management, water rights, river hydraulics/flood control, agriculture and land use, vegetation, wildlife/tourism, fisheries and equatic ecology, social science, community participation, health education and disease control).
1. Baseline Data Collection;
2. Environmental Impact Study (EIA);
3. Social Impact Study including resettlement;
4. Environmental Management Planning;
5. Contractor's compliance including penalty clauses and monitoring;
6. Use of local experts.
BACKGROUND: THE KYOTO AGREEMENT 1997
# To reduce emission of "climate gases" (mainly CO2: but also Methane and others: altogether 6 gases) of 5% within 2008/2012, compared to the 1990 level;
# Each OECD member has had got a limit of emission, no limit for developing countries (problem areas: developing countries: India and China);
# Opens up for "Flexibility Mechanisms" in order to ensure cost effective reductions:
- International Trade Quotas;
- Joint Implementation;
- Clean Development Mechanism.
# Trade of Quotas: National and International Trade of Emissions is permitted;
# Joint Implementation (JI): Bilateral cooperation for emission reduction: reduction finds place in an OECD country;
# Clean Development Mechanism (CDM): As JI, but reduction finds place in a developing country: can be started as from 2000 for developing countries, but all the detail regulations are not set as yet: Progress at next conference (COP6) at fall of year 2000: Still uncertainty about ratification of agreement, mainly by USA;
# In order to qualify for "CDM-Status" by a OECD country, one has to fully document a reduction (For instance: to reduce CO2 emission in a coal fired station: prices can go up with US$ 5/t coal (cost of CO2 emission), but the real costs to bring down a coal fired power station down to Kyoto levels can be as high as 400 - 500%!
The Kyoto-Agreement supports new gas power stations: Combined Cycle Technology: newest technology:
1. One gas turbine (like an aircraft turbine) uses heat and pressure: thereafter 2. the heat will be used by a steam turbine: In Norway: secret full costs are 12-15 c/KWh (N$ cents), but in good years: hydro power for less than 2 c/KWh: It is very important to utilise gas at right optimised place (is very important in a regional context): high transport cost of gas = f (volume and distance), but losses are higher in electrical lines than in gas pipelines.
For Gas is not only the volume but the price level important: Gas export is cheap, electrical generation from gas doubles the price but with gas fired industries (Aluminium, paper bio-protein) prices can go up by 10 times.
June, 23rd 2001
Electricity Infrastructure in Namibia (Generation, Transmission and Distribution): Overview