WITH the dramatic rise in energy cost in recent years, energy conservation has become a dominant issue all over the globe. For countries dependent on imported energy, it is an even more important issue. Natural gas is the fuel of choice everywhere in the world, because of its cleanliness, ease of control and handling, and low sulphur content. For the same reasons, in the markets of Europe and North America, gas displaces fuel oil at prices above their thermal parity value. It is also a suitable raw material for the petrochemicals industry.
Bangladesh is relatively lucky as it has a reserve of natural gas of very high quality. However, its optimum use is essential, firstly for the fact that energy consumption is growing rapidly against a finite reserve and, secondly, because other types of energy sources like oil, hydroelectric, nuclear, wind or solar energy are virtually nonexistent, except for a limited capacity hydroelectric project at Kaptai. If energy is not conserved on an urgent basis, and an indiscriminate supply of gas is continued irrespective of efficiency of usage, the consequences are likely to be disastrous.
With progressive industrializa-
tion, consumption and demand are bound to go up rapidly. A time will come when gas supply will have to be strictly rationed, based on sectoral priority. Even now, the desirability of supplying/allocating gas to prospective big consumers like Tata has become a debatable issue.
There are two ways of addressing the forthcoming energy crunch:
• A knee-jerk reaction when the crisis unfolds.
• Planned pre-emptive measures adopted well ahead of such development.
Obviously, the latter would be a more desirable option. However, long term planning does not appear to be the forte of Bangladesh planners. The possible reasons could be:
• Indifference of politicians toward such issues.
• Absence of a planning culture.
• Dearth of expertsand expertise.
• Indifference toward the opinions of experts.
Lack of planning thus compels the parties concerned to react to the events unprepared. Aglaring example is the current power shortage. In this particular case, however, the fault did not lie with the planners -rather, the debacle was universally attributed to their political masters. If there was transparency and accountability in the decision-
making processes, this pathetic situation could have been averted. Asimilarsituation is inevitable in the gas sector if no efforts are made to:
• Improve the supply situation.
• Realistically predict different supply-demand scenarios.
• Put in place a practical policy framework to ensure optimum allocation/usage of scarce gas resources.
• Make decisions regarding priority sectors.
• Formulate and implement energy conservation regulations.
It is a matter of time when the government will have to be selective in supplying gas to more efficient thermal power projects. In extreme circumstances it may have to divert allocated gas from inefficient to more efficient thermal power projects for making optimal use of the limited indigenous resources.
The biggest sources of energy wastage are:
• Low efficiency power plants and conventional boilers.
• Inefficient utility power plants with conventional design having efficiency of around 30%.
• Large air-conditioned commercial premises consuming enormous energy without considering energy conservation codes and practices.
Current usage scenario
Currently, the major use of natural gas is for generating power. Natural gas of Bangladesh is of very high quality, having very low sulphur and high methane content. Consequently, it is desirable that the gas be used for high value added products like petrochemicals, fertilizer, steel, ceramic products etc., rather than generation of power.
However, in the absence of other sources of energy, gas had to be used for generation of power. It is likely that the thermal efficiency of the conventional power plants in Bangladesh is no higher than 35% -- far below that of modern power plants.
The most unsatisfactory use is the unmetered supply of natural
gas to the domestic consumers. This has resulted in unnecessary wastage of gas in many households, where the burner is kept lit in order to save a matchstick. Meters for domestic gas supply are used in other countries and, hence, it is high time to seriously consider their introduction here. This should not be an expensive proposition. Another reason for unsatisfactory use is the proliferation of small capacity gas generators having low thermal efficiencies.
Efficient modes of energy usage
In view of the seriousness of the issue, efforts have to be made to focus on the power plant efficiencies. Two of the most efficient processes of power generation are: Combined cycle power plants: Combined cycle power plants are those, which have both gas and steam turbines supplying power to the network. The cycle efficiency is thus improved by utilizing waste heat from exhaust gas. By combining the two cycles, both efficiency and power are increased. Generally, combined cycle power plants are 50% more efficient than conventional steam power stations and, hence, these have the potential of supplying power at reduced tariff.
Co-generation: Co-generation is the simultaneous generation and use of both electric and thermal energies from a single fuel source. In many industrial plants, energy transfer as heat, called "process heat," as well as electric power is needed. A balance between these two loads is an important factor in determining the cost of the total energy needs.
An ideal steam-turbine cogeneration plant utilizes high-availability steam to generate power, and low-availability steam leaving the turbine for process heat. As a result there is no waste energy and no need of condensers.
Recommended policy decisions
The following recommendations are made for consideration of the authorities towards establishing a policy framework in respect of optimal gas usage and energy conservation.
• It is imperative that, prior to supplying gas to a power project, the projected plant efficiency be vetted to ensure that it is above a certain mandated threshold (say 50%).
• A mandatory energy audit should
be introduced for both existing as well as future power plants. Should it be necessary, remedial measures through retrofitting and/or design alteration must be considered to enhance plant efficiencies.
• The requirement of high thermal efficiency should also be strictly applied to industrial powergener-ation. New gas connection may not be given to a bulk industrial user who does not opt for cogeneration, or a combined cycle power plant, for his industry.
• Supply of gas should be considered only when consumers have energy conservation measures in place.
• Gas companies should conduct energy audits to demonstrate to the industries that saving gas and reducing costs will create a winwin situation.
• Feasibility of introducing domestic meters should be considered on an urgent basis. It would have dual benefit, increased revenue and reduced gas consumption.
• Packaged gas turbine generators are to be preferred over gas engine configuration for efficient co-generation by independent users.
• Feasibility of using alternative energy sources will have to be explored to divert gas usage.
In the context of increased demand for a depleting resource, there is no alternative but to conserve energy through conservation as well as mandated/enforced enhancement of efficiency in power generation. Making use of what is normally waste exhaust heat through combined heat and power systems, co-generation efficiencies of 70% and above are attainable. That would yield most attractive economic returns on additional investment. Use of cogeneration plants in certain industries, like textile where process heat is also necessary, is very profitable.
Thus, there is no compelling excuse for not adopting more efficient systems which will enable the utilities to lower tariff, benefiting the customers, and increase the ratio of power availability versus powerdemand. Ahmadul Ameen is a former Planning Manager and Chief Engineer, Titas Gas and a retired Professor of Mechanical Engineering.