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Solar energy has a great potential to give cheap and abundant energy to rural areas of the world, but is the technology ready to be implemented today? This stydy looked at the possibilities to introduce more renewable energy into the local hand-made paper production in Bangladesh. Specifically the potential of solar heated vacuum tubes filled with water as a heat carrier. This type of solar thermal collectors are cheap to produce, relatively efficient at converting both direct and diffuse solar energy into usable energy, and have a very simple construction that do not require a lot of training to handle. The study showed that the collector could convert about 70 % of the energy from the sun into usable energy in the form of hot water circulated in the system. On average in Bangladesh the 5 m2 collector used is expected to have an output of about 25.6 MJ per day (yearly average) and about 4.8 MJ was needed to evaporate 1 kg of water from the drying papers (including the system losses). This can be compared with the old system that used about 8 MJ per kg water evaporated. Finally the study includes a step by step guide into how to build a system like this by locally available material. The only parts that were imported were some measurement equipment and parts of the collector that was not yet available through local distributors. The pump was also not produced in Bangladesh, but a similar pump could be bought by local companies that import this type of equipment.

Drying is an energy intensive process. The conventional heat-based drying methods often produce changes in the physico-chemical properties of products. A newly developed electrohydrodynamic (EHD) drying technique may be much less destructive to these heat-sensitive materials. This thesis presents comparative analyses of product deterioration in EHD-dried whey proteins, using electrophoresis, differential scanning calorimetry (DSC), and color measurements. Gel electrophoresis showed the disappearance of bands and reduction in band intensities depending upon the temperature of the oven in which the whey protein was dried. The thermograms of the differential scanning calorimeter varied considerably as the temperature of oven-drier increased. EHD, air-drying, and their combination showed no significant change in the electrophoretograms and thermograms compared with the native protein. Color measurements also indicated no significant change in color of EHD-dried whey protein whereas oven-drying produced darker colors from the original. These results allowed us to conclude that physico-chemical properties of whey protein remained intact after drying with EHD.

Microwave power is seen as a promising alternative to conventional methods for drying freshly harvested grains to safe storage moisture levels. In an attempt to elaborate a continuous flow microwave dryer, the optimum operating characteristics of a prototype microwave antenna were investigated during a low power microwave drying simulation with corn at three different moisture content levels (15%, 23% and 30% w.b.). The antenna consisted of a slotted waveguide with the orientation and width of the slots being the main points of investigation. / The optimum angle of the slots with respect to the direction of propagation of the travelling wave was found to be in the neighbourhood of 55° at all moisture contents. Slots 13 mm wide gave better results than the 6 mm ones which are often suggested in literature.

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