To increase share of renewable in energy mix and to increase decentralized nature of the energy system, Yogyakarta needs to improve energy technology applications that utilize a variety of local renewable energy resources. In this spirit, this paper describes examples that demonstrate challenges in the application of small-scale renewable energy installations based on bio-energy, hydropower and small-scale photovoltaics system in Yogyakarta. Discussion was focused on the challenges of benefit sustainability in utilizing renewable energy technologies. The study was conducted on three biodig2ester systems based on cattle waste: two systems utilizing waste from tofu small industry and a system using human faeces. From socio-cultural point of view, the study showed tendency of willingness of local community to use biogas instead of fossil-based energy and indication of the willingness of local community to run and maintain existing biodigester systems. However, there was still lack of proper operation and maintenance standard. The study showed that three cattle manure-based biodigester could reach 91%, 78% and 85% of theoretical level respectively. Two biodigester systems based on tofu industry waste achieved 72.78% and 0%, respectively, while the human faeces biodigester reached level of 95.6%. Furthermore, it was shown that six biodigester systems studied were unable to meet economic feasibility criteria. Study was also conducted on a micro-hydro power plant built in Van Der Wick irrigation channel. The power plant was of 11 kW installed capacity. The study was focused on debris being blocked by trash rack and its influence on the power plant's performance. The result showed that the debris accumulation could lead to blockage of the trash rack that could, in turn, decrease water discharge flowing into intake of the power plant. In one observation during the study, the power plant even stopped working in less than four hours due to total trash rack blockage. Meanwhile, another set of detail study was also conducted on 20 of 60 solar home systems (SHSs) which were in operation for two years. They were distributed and installed by the government of Yogyakarta to districts of the province as a grant. The SHSs are of 50 Wp and are designed to power three lights. The study showed that all SHS under study could, in average, only achieve 68.05% of designed performance level. Besides, the problems in solar panels, wiring, inverter and light ballast were also found. The last one occurred in 50% of SHSs under study. Principle of the holistic framework of the technology diffusion and the supporting network should be implemented to keep benefit of small scale renewable energy infrastructures in Yogyakarta sustain. It needs comprehensive and long term program touching both technological and non-technological aspects. (C) 2013 The Authors. Published by Elsevier B.V.
