Die ontwikkeling en toepassing van 'n koste-gebaseerde elektrisiteitstariefstruktuur vir 'n groot industriële verbruiker

Abstract

As in many developing countries, electricity is a vital engine for growth, development and prosperity in South Africa. However, the current electricity supply industry (ESI) in South Africa is at a critical crossroads, and urgent restructuring of the distribution industry is necessary to ensure the long-term viability of the ESI. Sasol Synthetic Fuels (SSF), being a large industrial user and co-generator of electricity, must position itself in this fast changing environment to ensure a smooth transition without price shocks to the future dispensation. The purpose of this research project was to develop and implement a customised, cost-based electricity tariff structure for SSF. The tariff structure must be such that the real time marginal cost of electricity is proportional to the Eskom marginal generation cost in order to provide the correct pricing signals for purposes of optimisation. A number of possible future models for the South African ESI are discussed, as well as tariff structures resulting from the models. An electricity wholesale market with decentralised regional distributors is postulated as the most probable future model, and a unique tariff structure is developed that will position SSF well for such a scenario. The Sasol tariff consists of a take-or-pay contracted base load, equivalent to the typical bilateral financial hedging contracts in electricity markets, as well as time-of-use energy rates for additional purchases. The energy rates are equivalent to pool prices in a liberated industry. No demand charges are applicable. The SSF process is analysed from an electricity consumption perspective, and a demand side management initiative is developed, focussing on the operation of the boilers, own generators and oxygen units. It is shown that the most optimal operation of these units according to the new tariff structure will result in savings in electricity costs to the amount of about R1 million per month, or 2,5% of the SSF electricity account. This potential saving is used to economically justify the establishment of a centralised energy control centre. In conclusion the contribution of tariff changes to the profitability of SSF is evaluated. A unit cost comparison shows that significant improvements were made, and apart from the cost savings the new tariff structure enabled SSF to maintain higher production throughputs during steam shortages.