Exploring alternative avenuesof maximising power supply

FE Team | Published: December 12, 2011 00:00:00 | Updated: February 01, 2018 00:00:00

SA Mansoor With the spiralling international price of hydrocarbon fuels and our ever-increasing demand for electricity, the harnessing of alternative energy sources and power conservation brooks no delay for the nation. Shortage of power has been a persistent problem all over Bangladesh, more so in Dhaka. In Bangladesh, the gap between demand and availability of power is increasing every year. The trend is similar for greater Dhaka city, in fact it is possibly more precarious than in other areas of the country. This write-up presents cost-effective and viable options for reducing this demand to availability gap of electricity. Apart from harnessing alternative options for power, ways and means possible for rationalising the demand scenario through better and more efficient utilisation of power and energy in the national perspective is presented. Looking at capacity building, normal power plants with switchgears, substations and interconnections represents a large capital outlay (mostly foreign exchange) and time. Setting up a green-field power station from start to full-load operation of say 50mw-100mw could take up to 10 years given our modus operandi and lack of ready foreign exchange. It has to go through various stages both within the government hierarchy and subsequently with donor or lending agencies like ADB or World Bank. All these bureaucratic process probably takes, if not more, at least the same time as physical execution of the project. In the short term, there are at least two proven and viable options, which could easily supply between 80mw-100mw of additional electricity for the greater Dhaka region. In one case, the investment will be only in electrical and electronic paralleling and load management equipment with already available gas or diesel fuel-based source of power. The other option requires no fuel, only capital investment for plant and machinery to convert gas transmission pressure energy to power and the usual electrical set up as in the earlier case. These investments compared to a new power plant will need far lesser financial input at one time because of its modular concept. The gestation period is less, as there will be a large number of small units interconnected to modules, to run parallel to the local utility distribution. Once firmed up, a two or at most three-year time frame should be quite realistic. One of the short-term options described earlier, which does not require any capital investment in terms of electromechanical plant and equipment, presents a viable source of available but untapped potentially surplus installed power capacity in Bangladesh. Captive-generating units operated by many industrial and commercial customers for back-up or prime power, represents a significant untapped resource for addressing the generation and transmission capacity constraints. In the context of our chronic power shortage, aggregation and dispatching of power from customer-owned generators for system load reduction and capacity relief is a positive outlook. Back-up generator dispatch programmes have been successfully run by a number of electric utilities in many states in the US. Independent operators there have actively pursued and successfully implemented may such programmes in recent years. Application of such programmes can help in formulating a plan for developing "virtual" power stations, made up of small individual generating sets that could be grouped together and be as large in capacity as a stand-alone commercial power plant. These aggregated system resources can be dispatched on demand using centralised aggregation setup that utilises the technical capability of the Internet and wireless communication technologies already available in Bangladesh. Through informal surveys based on location and capacity of captive generators installed in and around Dhaka city; there is an availability of about 2000mw of electricity from the industrial sector and similarly over 200mw from commercial sector. In the industrial sector, around 30 per cent of the capacity is gas-based and the balance diesel-based. In the commercial sector, over 80 per cent of the capacity is diesel-based. Interestingly, over 50 per cent of the industrial and 80 per cent of the commercial installed capacity of the generators do not operate between 7:00pm to 7:00am, a period when maximum demand for power (7:00pm to 11:00pm) in and around Dhaka. Furthermore, over 30 per cent of the industrial and 70 per cent of the commercial power is available throughout the day for utilisation as capacity relief. Based on these data, we could have at least 90mw (conservatively estimated) of power from the already installed captive-generation capacity in an around Dhaka to meet the local power shortfall. Tapping power from the generator sets of private owners is an interesting option, suitable to block-building of power systems, based on fund availability. It provides a quick tapping of extra power at times of need. Also the gestation period is low, probably not more than two years at the most, depending on the location and distance from the distribution sub-station. An added advantage is that we can progressively build-up capacity, in blocks of say 20mw-50mw or as suitable at a time, till the full potential is tapped, without interruption during building of one block or group by the other and without high financial burden at one time. Another potential and untapped source of power is the availability from the energy of high gas transmission pressure when reduced to low distribution pressure for commercial and industrial use. Depending on the pressure ratio and flow quantity, the system can generate power from the high gas transmission pressure without needing any combustion fuel, required for a normal generator. The set-up is very similar to a steam engine or steam turbine where high pressure steam provides power with low pressure steam as exhaust which is condensed and sent back to the boiler or used in the industrial process, if needed. This set-up requires the installation of an expansion engine or turbine as a parallel path to the gas pressure regulation station of our gas transmission system. It would be ideal to set up these units alongside the gas regulating station and the power so recovered sent to nearby large consumers or fed to the electrical distribution network. The best approach could be joint ventures set-up between the gas companies and private entrepreneurs who can possibly use most of the power in their industry without burning any gas for the power produced. Power from the gas pressure will to some extent reduce the demand for electricity and provide much needed capacity relief, as well as reduce the demand for hydrocarbon fuel to that extent. This, in fact, gives a double advantage; both adding power and conserving hydrocarbon fuel resources. This practice has been in use in some European countries and the US for quite some time, wherever high pressure gas is let down to low pressure for supply to consumers. It is in our interest that we take up this additional power generation options. Not only will it reduce gas consumption but it will ease power demand to that extent, and conserve fuel. One simply wonders why while we are crying for power, we have never thought of utilising this fuel-free source of power, so easily available? Among all the alternative options, this source of fuel-free power is the most logical. It will keep growing as our gas transmission increases and more pressure reducing stations are installed. One wonders why these ideas have not been applied to our power scenario as an easier and effective solution to meet the gap between power demand and supply. This scribe feels that probably our power authorities have a mindset of large and larger power plants only. There is no attention given to these alternative options, which, on the contrary, should have attracted higher priority for our power-starved and cash-strapped country. Developed countries adopt these routes as additional peak power sources as a normal option. For us, unfortunately, we have not even pragmatically looked at these promising simple solutions. Looking at other alternative power generation sources, four options are possible in Bangladesh. Of these, two options need fairly high investment. One is the solar cell route, and the other is power from municipal waste. Solar cell has made at least a start thanks to the initiative of Rahim Afroz, a renowned battery maker. But the high cost of solar cell and the associated batteries is the drawback. The disadvantage is the limitation of power only during daylight hours and that too in a cloud or rain free environment. A further requirement is cheap storage batteries, as without battery backup, solar power cannot be a realistic and usable option. The government may even provide cash subsidy or long-term loan at very low interest rates to encourage setting up of household solar cells in rural areas. NGOs and other international agencies can, in collaboration with our manufacturers, provide these for rural households and markets to improve the quality of life of our underprivileged rural population. This is an area, which should be investigated and followed up in detail, even as an alternative parallel option to rural power supply. Solar cell will ease the user's burden in terms of power tariff and spread the coverage of households using electricity instead of expensive kerosene as a lighting source. If authorities can get together and adopt this as a priority programme, it will succeed within a short span of time given determination and positive leadership. Also to reduce national financial burden, it could be implemented region by region over a number of years. If the use of solar power and solar cookers are taken up together as serious energy options for the nation and backed with financial support from NGOs and banks for the rural people in Bangladesh, the face of our villages can be changed within the next five to ten years. All we need is commitment and enthusiasm, for this idea to take root like various micro-credit and other development programmes which are playing a worthwhile role in uplifting the rural society and enhancing their quality of life. The other option is using municipal waste for power generation. This is an urban solution applicable to large cities like Dhaka, Chittagong, Khulna, Sylhet and Rajshahi, among others. I wonder why, apart from few scattered news here and there, nothing definite about such a project has come up. As a start, the government or Dhaka City Corporation in partnership with the private sector and foreign sources where such expertise is available, at least can go for even one such small power plant in Dhaka. We could then learn as we go along, and gradually increase coverage to other cities. For this type of power source, the fuel cost should be quite reasonable and it could be a source of employment for the poor; particularly in the collection, sorting and processing of municipal waste. This source of power from comparatively cheap and naturally available fuel needs determined efforts by the government as the catalyst to see the light of the day. One wonders what is stopping our Dhaka city fathers from going for the proposal already in their hand. It seems to be crawling if not stopped cold on their desks? Could the power-starved people be told why this is happening? Another potential source could be wind power which has much higher availability compared to solar power and will need lesser battery backup. Both these power sources have the inherent drawback of non-continuous power supply. Also the investment cost per kilowatt for wind turbine is one of the highest. However, it could be realistically tried out in the Chittagong Hill Tract area given its small pockets of load centre at areas remote from each other in a difficult terrain. Mobilisation of household and commercial UPS systems as power sources has been deliberately not discussed as these are very fragmented in Bangladesh. Also sustainability is limited to a few hours depending on battery backup capacity. But this source too has been utilised in dispatch programmes elsewhere particularly in the US, thanks to wireless and Internet-based load transfer and management programmes, and better quality and larger capacity of their UPS with adequate battery backup. The various options outlined above will help us not only in meeting the power generation shortfall, but also lower the demand for natural gas and oil which is imported either as crude or refined oil. It is important that we conserve our finite hydrocarbon energy sources. The writer is a retired engineer and can be reached at email: sam@dhakacom.com