Fuel switching reduces consumption and cost
FOLLOWING the three Eskom power emergencies since November, load shedding has been implemented. This, however, is adversely impacting on South Africa’s economy and the living conditions of the people. While the construction of the new capacity has been racked by delays, other short- to medium-term solutions to the crisis are of vital importance.
Energy efficiency and demand side management programmes, concerning the broad categories of conservation, load management, fuel switching, strategic load growth and self-generation, have been proven to be an effective way to deal with energy shortage problems by delivering the same service while consuming less energy.
Eskom has implemented many such initiatives in the past decade aiming to bridge the gap between electricity demand and supply.
Results have achieved a verified demand savings of more than 4 000 megawatts – the amount of power Eskom needs to save for its stage 3 load shedding. This, with an investment of R15 billion over 10 years, less than a 10th of the projected investment of Medupi whose full capacity is designed at about 4 800MW.
If Eskom hadn’t introduced such pro- grammes, South Africa would have suffered from load shedding much earlier.
In the past, the focuses of these Eskom initiatives were, however, mainly conservation and load management. Fuel switching and self-generation have barely been explored.
Under the current circumstances, energy efficiency and demand side management programmes are still and should always be an option.
Solar water heating, a renewable programme started in 2008, aimed to switch fuel away from electricity, promoting the uptake of a million units by this year. This programme, however, was not able to achieve that target.
About half the world’s energy demand is heat demand. South Africa is no different. According to Eskom, 40 percent of electricity consumed in the residential sector is used for water heating; the other 31 percent is used by kitchenware, including ovens, stoves and hotplates. A source from Japan estimated the South African industrial heat demand was sitting at about 70 percent of the industrial sector energy consumption. In terms of demand, the residential sector takes 14 105MW of Eskom’s output; the other sectors, an aggregated 25 160MW in 2013.
If the heat demand was supplied by sources other than electricity, a staggering 7 052MW from the residential sector and 19 060MW from the whole nation could be saved. This is more than four times the demand for Eskom’s stage 3 load shedding.
Assume that if only the heat demand for water heating in the residential sector was supplied by natural gas or coal gas, 5 642MW of the demand from the utility grid could be substituted, which would allow Eskom to meet the power demand without load shedding.
Currently, heat demand in South Africa is largely supplied by electricity.
However, conversion efficiency from coal to electricity and then to heat is much lower than direct conversion from coal/gas to heat.
Eskom’s power plants have a marginal 35 percent efficiency, while that of a conversion directly from coal or gas to heat can easily reach over 70 percent.
The coal gasification plants are able to reach conversion efficiencies from coal to heat about 75 percent and from coal to gas, then to electricity to heat about 50 percent efficiency – by far the most efficient technology.
While the capital cost of coal/gas/electricity technology such as the integrated gasification combined cycle is about 25 percent higher than the traditional coal-fired power plants, the semi-combustion process of the coal gasification to satisfy heat demand is quite affordable, less than half of Eskom’s current benchmark for these side initiatives of R5m/MW. The operational cost is about a third of a conventional power plant. Coupled with the large coal reserve in South Africa, clean coal gasification technology is a very attractive option to promote efficient use of its coal to generate heat.
Self-generation is another way to solve South Africa’s electricity crisis in the short to medium term. Using photovoltaics, wind turbines, co-generation systems and gas-fired turbines to supply part or the entire customer’s needs (heat/power) provides a convenient way to reduce demand from the grid and consequently alleviate grid pressure and reduce transmission losses. Co-generation systems installed in industrial plants that produce high temperature waste heat and captive power plants using biomass or gases are good examples of self-generation.
Energy efficiency and demand side management programmes are still the best option to adopt to alleviate the current crises. Let’s now focus more on fuel switching to satisfy the heat demand and self-generation.