Wood fuels are a major source of energy in the developing world whose sustainability is diminishing in forest cover and production increases in demand due to rising population. Alternative environmentally friendly accessible sources of energy for households are therefore a necessity. These include faecal matter, forest and agricultural residues that are convertible into briquettes. There source will depend on availability, impact on environment, renewability and energy content. The benefit of briquettes arises from near equal mass balance of carbon dioxide demand by photosynthesis in the atmosphere to the amount released during combustion. Briquetting thus need designed agglomeration machines and understanding of the engineering properties. The parameters density and shape have effect on combustion and performance characteristics hence should be determined. The research thus focused on spherical, triangular and cylindrical shapes and densities of 600 kg/m 3 , 700 kg/m 3 and 800 kg/m 3 on ignition and burning time. Carbonization of faecal matter and sawdust with binders was the activities. There was significant difference on ignition time on shapes and densities and none on burning times with shapes and binders. The average ignition time ranged from 2.7 to 3.7minutes irrespective of shapes and binders. The average burning time ranged from 18 to 26 minutes for molasses and starch bonded cylindrical briquettes. The spherical briquettes had the least ignition time of 2.7 minutes. Packing ratio, evenly distributed air spaces, higher volatile matter in binder, porosity due density advantaged the spherical briquettes.

Forced convection grain dryers are more efficient and achieve greater drying rates than natural convection dryers. However, it is necessary to dry an appropriate grain layer thickness in such a dryer for the drying process to occur efficiently and at an appropriate rate. A well sized fan is also essential if the drying process is to proceed effectively. An oversize fan will be unnecessarily expensive to buy and operate due to high fan power, while an undersized one will not be able to supply adequate air flow. The solar collector must be properly sized if it is to heat the air to the required temperature. All these factors need to be addressed during the design of a grain dryer. Lengthy and expensive trial and error processes can be avoided by applying simulation in the design process. This study developed an experimental grain dryer, addressing the above mentioned issues in the process. Simulation of air flow within an initial model of the dryer was done and the results used to size the fan and drying cabinet. The solar collector was also sized. The experimental grain dryer developed consisted of a drying cabinet of dimensions 0.5 m x 0.5 m x 1.0 m and was equipped with a 0.039 kW centrifugal fan. The solar collector area was of dimensions 1.2 m x 1.8 m.

An investigation on the effect of total solids on biogas production was done using a laboratory scale batch reactor of 0.15 m 3 capacity. The feedstock was dung from dairy cows managed under a free-range system. Experiments were done on a substrate having total solids of 6%, 7%, 8%, 9%, and 10% at a constant temperature of 35°C; and the mean biogas production was 0.249, 0.304, 0.487, 0.287, and 0.244 m 3 of biogas per m 3 of digester volume per day (m 3 /m 3 d), respectively. It was concluded that the highest average biogas production of 0.487 m 3 /m 3 d is attained at total solids of 8%.

The effects of varying distances on wireless signal propagation in indoor and outdoor built sites is presented in this paper. In indoor and outdoor built sites the major RF signal attenuation is due to multi-path interference, signal loss (fading), and non-line of sight signal blockage. A number of mobile communication systems is currently and frequently being used in indoor environments based on IEEE 802.11b standards which is on 2.4GHz frequency ISM band at the rate of 11Mbps. To determine the effects of varying distances on signal strength at 2.457 GHz, a Spykee spy Wi-Fi robot was used as the transmitter and laptop installed with a Wi-Fi card and Spykee console software to control the robot was used as the receiver. Results showed that the signal attenuation levels increased as distances increased.

Most biogas plants’ poor performance may be attributed to inadequate stirring strategy. The study evaluated the effect of stirring intervals on biogas production from cow dung and maize silage mixture (at mixed ratio 3:1) digested in a 0.15m3 laboratory digester at 30℃. SIEMENS LOGO PLC and ATV12HU15M2 Drive automatically controlled the stirring of 100 rpm for 3minutes at intervals of 1hour, 2hours, 6hours and 12hours with no stirring as control. The stirring intervals showed a significant effect on biogas production (P≤0.05) with 6hours and 12hours increased biogas by 3.11% and 1.48%, and the methane increase of 8.77% and 1.75%, respectively. The 2hours and 1hour reduced biogas by 26.5% and 39.35%, and methane decreased by 3.52% and 15.79%, respectively compared to control (implying that the frequent stirring is not good for biogas). The stirring interval of 6hours is thus recommended for 0.15m3 laboratory batch reactor of cow dung and maize silage.