|Ecologically Sound Energy Planning Strategies for Sustainable Development (Indian Institute of Sciences)|
Currently, energy planning in our country is not an integrated activity. Since there are many energy sources and end uses, there are many organisations and agencies that deal with different aspects of energy. The plans for electricity, coal, oil and fuelwood are done by respective organisations mainly based on the projection of energy demand. The primary goal of this approach is to go in for energy supply expansions on the assumption that there is a correlation between energy use and gross domestic product. With this approach energy becomes an end in itself, and the focus shifts on meeting increased energy consumption through energy supply expansion alone. This supply and demand based planning approach for each individual energy form has resulted in problems like more losses, more conversions and low efficiencies. This is evident from the disappearance of forests, village wood lots, roadside trees, construction of giant hydro electric dams, fossil fuel based power plants and controversial nuclear plants. This conflict between the energy demand and environmental quality goals can be solved by having an integrated approach to the problem of energy planning with a view to minimise consumption of non renewable resources of energy and maximise efficiency of energy usage and harnessing of renewable sources of energy in an ecologically sound way. Another aspect that has to be considered in the planning process is that of matching energy resources and end uses. Because of convenience, current usage of high quality energy such as electricity used for low quality activities like bath water heating is to be discouraged. Hence, strategies for integrated energy planning should include a) Improvements in efficiencies of end use devices and/or conversion equipments, b) optimising energy source - enduse matching, c) organised approach towards optimal use of renewable resources, d) proper exploitation of biomass energy resources and e) discourage use of depletable resources (by penalising).
Our earlier studies shows that there is vast scope for energy conservation in energy sectors. Highlights of some of our earlier studies are
1) Domestic sector in rural areas shows that there is scope for saving of 42% in the quantity of fuelwood used by switching over from traditional stoves to improved stoves (Ramachandra 1994, Ramachandra 1992, Subramanian et al 1983, and Subramanian 1984).
2) Study of energy efficiencies of end use devices in an Electro metallurgical industries (Ramachandra and Subramanian 1992) have shown that the efficiency of welding sets is about 14%, Furnace 10.4%, Diesel generators 36.5%, Electro plating process 36.5%. This shows possible saving in industries sector by switching over to transformer-rectifier welding sets with micro processor based numeric controller from conventional motor generator welding sets. Motors and drives consume a large percentage of the electrical energy used in the industrial sector. High efficiency motors (85.5 - 95% efficiency) currently available in the market are now competitive with the conventional type of motors, considering the cost of motor losses.
3) Energy analyses carried out for food processing sector revealed that most of industries are utilising less than 50% of installed production capacity (Ramachandra and Subramanian 1993). Low power factor when motor is under loaded, leads to inefficiency. It is estimated that 23 to 38% energy could be saved at improved efficiency due to full utilisation of installed production capacity.
4) usage of solar water heater, for bathing water heating could bring down electricity consumption in urban area and fuelwood consumption in rural areas.
5) harnessing hydel potential in ecologically sound way by means of mini/micro/small and hydro+thermal (as against major dams) potential in hilly districts. It is estimated that about 2250 million units per year could be generated in Bedthi and Aghnashini river catchment alone in Uttara Kannada district
6) harnessing solar energy in coastal regions. Our estimate shows that in coastal taluks like Kumta, Karwar, Honnavar, Bhatkal in Uttara Kannada District of Karnataka state that there is potential of 5.5 kwh/m2 (based on mean daily insolation).
7) Our study of energy utilisation in Industries sector shows that, about 27.72% energy could be saved in Industries sector. Which means about 1541 million units of electricity could be saved ( as per electricity statistics Industries sector in Karnataka has consumed about 5560 million units during 1991-92). This saved electricity is equivalent to electricity output of 300 MW installed capacity of generating stations. Environmental problems associated with mega projects, the increasing demand of states/ country and resource depletion make it increasingly imperative that our planners divert their attention towards improving efficiency in all sectors. This illustrates that, there is ample scope to conserve energy in industries sector.
The advanced technologies discussed below promise significant reductions in energy use, implementing these may be less costlier compared to generating electricity through supply expansions taking into consideration environmental costs associated with new installations.
(i) Proper maintenance of electric motors in textile industries brings down energy consumption considerably; about 3% of power consumption can be saved by improved maintenance. This also reduced repairs as shown by the fact that burnout of motors varies in frequency from one in three months / 10,000 spindles to 8 - 20 in three months / 10,000 spindles. The increase is 8 - 20 fold in the second case. Similarly burnout frequency varies from 1 - 7 to 60 for six months for 25,000 spindles.
(ii) Waste heat recovery in boilers can reduce energy use by about 10%. It is shown that the payback period is a few months.
(iii) Use of polyester cotton tapes etc. in textile mills will reduce consumption by about 10%.
(iv) Replacement of old boilers with high efficiency boilers and introduction of turbines and generators can reduce total energy requirements by more than 20 - 30%.
(v) Spindle speed is an important factor in energy consumption in textile industries. Proper speed can reduce energy use. In the survey the energy consumption varies from 60% to 165% (with the base of 100 chosen for one mill). This shows that proper speeds can reduce consumption.
(vi) Advanced processes in the steel industry are mostly major process changes that could revolutionalise the Iron and Steel sector (Carlsmith et al 1990). The plassmelt method involves smelting partially reduced iron powder with pulverised coal by using heat supplied by a plasma system. ore to powder steel making could reduce the energy consumed by 40 percent. Direct steel making could double or triple production rates compared to the blast furnace and offer a 30% reduction in energy savings. The energy required to produce steel from scrap is less than one-half that required to produce steel from raw materials. However scrap contain residual elements that have adverse effects on the properties of the steel. The electric arc furnace is well established technology and because of its increasing market share, improvements such as scrap pre heating, DC arc furnace, induction melting, heat and dust recovery and ladle refining are to be researched.
(vii) Conventional chemical pulping in the paper industry is dominated by the very energy intensive kraft process. The energy required to recycle paper is about one-half that required by the kraft process. Desired improvements in the recycle process concentrate on improving the process to remove color and filler. Improvements in the paper making process focus on improved process control, process physics, and improved materials. These improvements would have a substantial effect on decreasing energy consumption. Bio pulping, chemical pulping with fermentation, and ethanol organosol pulping are the most recent promising advanced processes involve integration of at least one fermentation process with a conventional pulping process.
(viii) Carbothermic reduction of Aluminum ore or alumina has the potential for substantial energy savings. Aluminum trichloride electrolysis allows for more production per unit cell volume. The permanent anode design would decrease the frequency of anode replacements and the wetted cathode might enable a reduction in the distance between the electrodes associated with a high voltage loss without a loss in current efficiency.
(ix) Catalysts are used in many industries to produce chemical reactions at a lower pressure and temperature, thereby using less efficiency. Better understanding of the basic mechanisms of catalysts may lead to new classes of catalysts. These could be beneficial in the areas of one-step conversion of methane to methanol, photocatalytic reduction of water, combustion enhancement, and pollution control (Fulkerson et al 1989).
(x) Recovery and reuse of waste heat offers significant opportunities for energy conservation. The development of cost effective heat exchanger and thermal storage units is needed for the recovery of high temperature reject heat. The development of high lift heat pumps could greatly enhance the utility of low grade waste heat.
(xi) Cogeneration is the simultaneous production of process heat and electric power. Providing moderate or low temperature heat as a by product of the work from a heat engine is much more efficient than providing heat directly by burning fuel. Most typical Cogeneration industry converts only 10 to 15% of the energy into electricity (Williams 1978). Intercooled Steam injected gas turbine - a new technology is being developed which incorporates a modern aircraft engine and can accommodate variable amounts of steam returned to the turbine combustor and therefore has a flexible electricity-heat ratio (Ross 1989). Steam not returned to the turbine is used for process heat. With a full steam injection, 40% of the energy can be converted into electricity.
(xii) Variable speed controls for motors are currently available for application on existing and new equipment to adjust the speed control so that the motor and driven equipment can match the requirement of the process. Motors account for about 55% of the electric energy consumed in Karnataka State. The potential for conserving energy by applying high temperature superconductors in place of conventional conductors in industrial motors is very large. The advantages include reduce volume and mass, higher power density, enhanced performance and improved operating efficiency.
(xiii) Industrial separation processes involving separation of the components in a mixture are highly energy intensive. Advancement of alternative processes such as membrane separation, solvent extraction, critical fluid extraction and advanced drying concepts are less energy intensive. This could be beneficial to applications like black liquor concentration in the paper and pulp industry, hot food processing waste water concentration, dilute soluble food process stream concentration and drying of products such as textiles and paper (Dale 1991).