The potential of combined heat and power generation, wind power generation and load management techniques for cost reduction in small electricity supply systems
An evaluation is made of the potential fuel and financial savings possible when a small, autonomous diesel system sized to meet the demands of an individual, domestic consumer is adapted to include: (1) combined heat and power (CUP) generation. (2) wind turbine generation. (3) direct load control. The potential of these three areas is investigated by means of time-step simulation modelling on a microcomputer. Models are used to evaluate performance and a Net Present Value analysis used to assess costs. A cost/benefit analysis then enables those areas, or combination of areas, that facilitate the greatest savings to be identified. The modelling work is supported by experience gained from the following: (1) field study of the Lundy Island wind/diesel system. (2) laboratory testing of a small diesel generator set. (3) study of a diesel based CUP unit. (4) study of a diesel based direct load control system. (5) statistical analysis of data obtained from the long-term monitoring of a large number of individual household's electricity consumption. Rather than consider the consumer's electrical demand in isolation, a more flexible approach is adopted, with consumer demand being regarded as the sum of primarily two components: a small, electricity demand for essential services and a large, reschedulable demand for heating/cooling. The results of the study indicate that: (1) operating a diesel set in a CUP mode is the best strategy for both financial and fuel savings. A simple retrofit enables overall conversion efficiencies to be increased from 25% to 60%, or greater, at little cost. (2) wind turbine generation in association with direct load control is a most effective combination. (3) A combination of both the above areas enables greatest overall financial savings, in favourable winds resulting in unit energy costs around 20% of those of diesel only operation.