Southern Africa is faced with the complex challenge of achieving sustainable economic development and food and energy security while protecting the environment. The region is currently experiencing an energy crisis, a result in part because of global increases in crude oil prices and limited generating capacity in some countries. We examined the potential of biofuels to address the aforesaid problems and their role in the agroecological and socioeconomic systems in the region, highlighting the challenges to be overcome before biofuels can become an integral part of the regional socioeconomic dynamics. Major hurdles to biofuels establishment include relatively poor awareness of the potential and opportunities presented by biofuels, technology challenges, food insecurity vulnerability associated with the use of grains such as maize as feedstocks, potential conflict in resource allocation between food and fuel crops, and good governance and its impact on stability of food supply. Resource allocation and the balance between the need for food security and fuel is discussed in the context of selection of a crop matrix that does not compromise food security or limit development of the biofuels sector. While the use of maize for ethanol might enhance producer prices, it may contribute to high food inflation and political unrest. Sweet sorghum on the other hand, presents an opportunity to provide food and bioethanol without compromising food security. Biofuels have great potential in southern Africa, but there is a need to establish and nurture the development of capacity, in the value chain from production to consumption, to realise the benefits of biofuels in the region.

As the energy consumption is increasing in an alarming rate and peoples and international communities are well aware of environmental protection, alternative (i.e., renewable and fuel cell based) distributed generation (DG) systems have attracted increased interest. Wind-based and photovoltaic- (PV-) based power generation are two of the most promising renewable energy technologies. Fuel cell (FC) systems also show great potential in DG applications due to their fast technological development and the merits they have, such as high efficiency, zero or low emissions (of pollutant gases), and flexible modular structure. In this work, the techno-economic feasibility study (using HOMER) of emission-free hybrid power system of solar, wind, and fuel cell power source unit for a given rural village in Ethiopia called Nifasso (latitude of 9°58′40″N and longitude of 39°50′3″E with an estimated population of 1059) that can meet the electricity demand in a sustainable manner has been studied. The main power for the hybrid system comes from the solar and wind energy while the fuel cell and rechargeable batteries are used as a secondary and primary energy back up units, respectively. We can say storage as primary and secondary based on the sequence of operation. Hence, when there is shortage, first the battery discharges to fulfill the load demand and if the battery reaches to its allowable minimum capacity, it will stop further discharging and the fuel cell will operate so as to convert the stored hydrogen into electricity. In the result, different feasible alternative solutions have been obtained with a narrow range of COE which are better than the previously studied PV-wind-Genset hybrid set ups.

It is known that there is a significant amount of thermal energy used for the sugar cane industry for the purpose of power production and for use in the sugar or ethanol processing in cane sugar industries. Likewise, it is understood that there are substantial amounts of waste heat that is not being recovered, in particular for traditional sugar mills. Regardless of this, energy conservation is given less consideration as compared to operational convenience due to the fact that sugar mills are self-sufficient in energy (heat and power). The identification of such potential heat loss areas (especially during transient conditions) suggests the sugar mills play a vital role in energy saving. In this study, a modified setup of the base case plant considered in part I of this paper is assessed for its energy potential and possible major heat losses during steady state and transient conditions where 2-h stoppage of the mill presses are considered to occur. For the modified setup, there are two major scenarios considered having two subscenarios each. The result of the assessment showed that the steady state assumption scenario of the modified plant (where bagasse drying is not considered) indicated a 20 % reduction in the losses considered which resulted in a 57 % power generation increase as compared to the steady state model of the base case plant. It is also possible to save excess bagasse by drying the bagasse for later use during unexpected stoppage. The carbon dioxide emission (amounting 29 t/day in case 2a of this study) that occurs during the use of fuel oil during such stoppages will thus be avoided. The simple economic analysis showed that it is only in case 2a where fuel oil cost is included in the operation cost that resulted in a negative NPV. Since the rest of the scenarios use bagasse as a fuel which is free, the NPV for all was positive. For the electricity price of 0.04 US $/kWh and discount rate of 15 %, the minimum payback period attained is about 3 years (case 1b) where the bagasse moisture content is 30 % whereas the maximum payback period is 6 years (case 1a) where there is no bagasse drying considered.

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