**4.2 Solar energy**

52 Renewable Energy – Trends and Applications

**Secondary residues**  Include material from: Processing wood Food and organic materials in

**Tertiary residues**  Include waste arising after consumption of biomass such as sewage, municipal/city solid waste, landfill gas etc.

concentrated form suck

**Remarks** 

1 Sawdust 100 More studies are required to establish actual value

4 Cattle, Pig dung - More studies are required to establish actual value

Estimated average annual production levels of wood fuel and its associates such as tannin

1 Forest residue 523 Initial estimation. Its value could be high.

**Remarks** 

3 Crop residue 212 Initial estimation. Expected to increase

5 Bagasse 57 Initial estimation. Expected to increase.

as

Potential of biomass sources (non-wood) in the country are given in Tables 7.

**Estimated Potential [MW]** 

**Estimated Potential [Mw]** 

2 Wattle residue 15 Initial estimation

2 Sisal Residue 500 Will increase in near future

 Sawmill bark Tree chips sawdust

**Primary residues**  Primary residues materials are usually from forestry, agricultural crops and animal rising. Primary residues can be categorized either as residues arising in concentrated form( dung from stalled livestock, harvested cereal straw, stalk, husk) or residues that must be gathered together (dung from grazing livestock, crop residues which are not harvested such as cotton and

maize stalks)

**S/No Renewable** 

Table 6. Types of Biomass Supply

**Energy Sources** 

 **TOTAL 869** 

residue are shown in Table 8.

**Renewable Energy Sources** 

 TOTAL 538 Table 8. Wood Biomass Resource

**S/N O.** 

Table 7. Non-Wood Biomass Resource

Solar radiation is the type of energy which is available at any location on earth. Solar energy in the country was assessed using the following criteria:


The maximum power density of sunlight on earth is approximately 1 kW/m2 irrespective of location of the area or country. Solar radiation per unit area during a period of time can be defined as energy density or insolation [Renewable Energy Project Handbook, 2004]. Solar radiation is measured in a horizontal plane; the annual insolation varies by a factor of 3 from roughly 800 kW/m2/ year in northern Scandinavia to a maximum of 2,500 kW/m2/year in some desert areas such as: Kalahari etc. Practical applications of solar energy the absolute value yearly insolation is less important than the difference in average monthly insolation values. However, the differences vary greatly from about 25 % close to the equator, to a factor of 10 [Renewable Energy Project Handbook, 2004] in the most northern and southern areas. The average power density of solar radiation is normally 100-300 W/m2 and the net plant conversion efficiencies are typically 10 % or less, hence, substantial areas are able to capture and convert significant amount of solar energy for energy generation. Tanzania is well situated near the equator; the country can capture and utilize solar energy in the purpose of rural electrification.

Solar energy presents great development in the country. Investigation conducted by Nzali et al [Nzali et al., 2001] suggested several areas in the country which can contribute to development of solar energy. Table 9 gives the insolation levels values in some areas of the country captured by the study. Solar photovoltaic energy is uniquely useful in rural not served by the National grid to provide basic services such as irrigation, refrigeration, communication and lighting. Solar energy is often more efficient than traditional sources such as kerosene. For lighting, a photovoltaic compact fluorescent light system is more efficient than kerosene lamp; used in rural areas to provide night lighting. Photovoltaic system also avoids the high costs and pollution problem of standard fossil-fuel power plant.

#### **4.3 Wind energy**

Wind is widely distributed energy source. Between 300N and 300S, air is heated at the equator rises and is replaced by cooler air coming from the South and the North. At the earth's surface, this means that cool winds blow towards the equator. Tanzania is situated near the equator; it is affected with the movement of the air movement as well as benefits from this prevailing condition.

The availability of wind varies for different regions and locations. It should be noted that mean wind speed may differ by as much as 25% from year to year. In some areas there are also significant seasonal differences. It has noted that in the country, there is a period when wind speeds are higher and some period wind speeds are low. Due to seasonal variations, the potential of wind for power generation can be significantly higher than the annual mean wind speed would indicate. Thus, not only the mean wind speed but also the wind speed frequency distribution, commonly described by a Weilbul distribution have to be taken into account in order to estimate accurately the amount of electricity to be generated. Wind speed varies with height, depending on surface rough ness and atmospheric conditions. Daily and hourly variations in the wind speed are also important for scheduling the operation of conventional power plant and adjusting their output to meet these variations.


Table 9. Mean monthly Daily Insolation totals in kWhm2/day for period of ten years [source A.H. Nzali 2001]

Wind resources can be exploited mainly in areas where wind power density is at least 400 W/m2at 30 metres above the ground. Continuing technical advances has opened up new areas to development, Because of the sensitivity of the potential of the value of the wind speed, the determination of specific sites for wind energy projects depends on accurate meteorological measurements, and sites measurements etc. Even in the best sites, the wind does not blow continuously. Thus, it can never achieve the 100% required for electricity generation. Wind energy potential in Tanzania, wind power densities are given in Table 10.

Wind farms for commercial plants appear promising at Makambako and Kititimo in Singida region as well as Mkumbara, Karatu and Mgagao. Areas along rift valleys, the southern high lands and along Lake Victoria are reported to have some possibilities of potential wind sites.

Over the years, wind energy resources in the country have been used for wind mill to pump water. Less was been done in electricity generation. However with the availability of policy and renewable energy promotion program, emphasize now is toward utilization of wind energy in electricity generation. Number of wind mills available in the country is given in Table 11 and a photo depicting a wind turbine in Itungi village in central Tanzania is shown in Figure 1. The wind turbine is used to generate electricity for water pump.

Fig. 1. Wind Turbine used to Generate Electricity for Water Pumping
