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Waste heat is heat generated in a process by way of fuel combustion or chemical reaction,which is then “dumped” into the environment and not reused for useful and economic purposes. The essential fact is not the amount of heat, but rather its “value”. The mechanism to recover the unused heat depends on the temperature of the waste heat gases and the economics involved. Large quantities of hot flue gases are generated from boilers, kilns, ovens and furnaces. If some of the waste heat could be recovered then a considerable amount of primary fuel could be saved. The energy lost in waste gases cannot be fully recovered. However, much of the heat could be recovered and adopting the following measures as outlined in this chapter can minimize losses. Heat Pumps
The majority of heat pumps work on the principle of the vapour compression cycle. In this cycle, the circulating substance is physically separated from the source (waste heat, with a temperature of Tin) and user (heat to be used in the process, Tout) streams, and is re-used in a cyclical fashion, therefore being called 'closed cycle'. In the heat pump, the following processes take place: § In the evaporator, the heat is extracted from the heat source to boil the circulating substance; § The compressor compresses the circulating substance, thereby raising its pressure and temperature. The low temperature vapor is compressed by a compressor, which requires external work. The work done on the vapor raises its pressure and temperature to a level where its energy becomes available for use. § The heat is delivered to the condenser; § The pressure of the circulating substance (working fluid) is reduced back to the evaporator condition in the throttling valve, where the cycle repeats. The heat pump was developed as a space heating system where low temperature energy from the ambient air, water, or earth is raised to heating system temperatures by doing compression work with an electric motor-driven compressor. The arrangement of a heat pump is shown in figure
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The heat pumps have the ability to upgrade heat to a value more than twice the energy consumed by the device. The potential for application of heat pumps is growing and a growing number of industries have been benefited by recovering low grade waste heat by upgrading it and using it in the main process stream. Heat pump applications are most promising when both the heating and cooling capabilities can be used in combination. One such example of this is a plastics factory where chilled water from a heat is used to cool injection-moulding machines, whilst the heat output from the heat pump is used to provide factory or office heating. Other examples of heat pump installation include product drying, maintaining dry atmosphere for storage and drying compressed air.
Principles of energy conservation:
- Maximum thermodynamic efficiency
- Maximum cost effectiveness Energy Conservation measures in industry:
- The selection and process should be such that it involves efficient use of energy. 2.The plant and equipment should be selected with special emphasis on reliability, maintainability and energy efficiency vis-à-vis quality and control of output. 3.The location of plant and equipment should be such that energy costs of transportation of raw materials and finished products are minimum. 4.The use of renewable sources of energy i.e. solar, wind, etc. should be encouraged to reduce the consumption of non-renewable source of energy i.e. electricity oil etc. 5.The regular cleaning, inspection, and lubrication should be adhered with a view to eliminate unreliability in production and have a proper quantity quality to output. 6.The production schedule and service should be planned and implemented with minimum use of resources i.e. labors, machine, materials etc. 7.Expensive purchase of raw material and stocking of finished products should be avoided. 8.The wastage in production and service must be kept at minimum. 9.all motors, cables, switches, gears etc. of the production machines should be adequately loaded. Overloading and under loading should be avoided.
- The latest maintenance techniques and tools should be used to prolong the life of machines like preventive maintenance, predictive maintenance etc. based on requirements.
- The lighting in and around the factory area should be as per the standard and with minimum requirements.
- Use of waste heat from the process of plants should be effectively used.
- The use of service facilities like air cooling, air conditioning, humidification, steam, water, compressed air etc. should be very efficiently and effectively used.
- The peak load of the electricity requirements should be kept as near the average load as possible to control the maximum demand i.e. to reduce loads factors.
- The power factor of the electrical load should be kept higher than 0.90 to 0.
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9 Evaluation of the present energy consumption. 10 Implementation of ECMs. 11 Monitoring of EC efforts.
EC: - It involves wastage of energy and adsorption of methods to conserve energy, without
affecting productivity & comforts, more energy efficient processes should be replaced by less
efficient processes.
Energy Conservation opportunities ECOs.
These are the avenues/ opportunities, which are open to implement energy conservation
activities.
Energy Audit:-
It is an official scientific study/ survey of energy consumption of a region/ organization/ process/
plant/ equipment aimed at the reduction of energy consumption and energy costs, without
affecting productivity and comforts and suggesting methods for energy conservation and
reduction in energy costs.
Steps involved in energy management.
1 Energy management as policy and commitment
2 Management commitment
3 Selection of the Energy Manager
Responsibilities of Energy Manager:-
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- Energy consumption monitoring
- Planing energy conservation
- Implementing energy conservation measures
- Organization of HRD programmes
- Achieve EC objectives. 4 Formulation of supply strategies and energy conservation plans 5 Awareness and Involvement. 6 Introduce suggestions, schemes and award schemes. 7 Appoint or select energy Audit Team or consultants. 8 To obtain report on EC measures. 9 To obtain technical assistant report (TA-report) Instructions in TA report
a) EC measures b) Do or Don’t c) Operation and maintenance instructions. d) Recommendation of a new technology. 10 Implementation of TA report and EC measures. 11 Implement E-optimized operation and maintenance practices. 12 Establish practice of monitoring energy consumption and effectiveness of ECM’s. 13 Recycling of scrap, waste material, etc. 14 To review and optimize new design of the plant and equipment and to allocate finds for retro fitting.
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Supply side
Power sector Electrical energy management
Generation of power- Thermal
(coal/gas,
Hydro, Nuclear)
Transmission (AC, high voltage interconnections, SCADA systems)
Utilization of energy (Plant, industry, managed by SCADA systems)
Fuel (Oil, natural gas, coal, fire-wood, chemicals etc)
Non commercial/ renewable energy
(a) Land biomass, solar, wind, geothermal, tidal etc. (b) human energy (labor) (c) Animal energy
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Note: Non-Commercial is the wood.
SCADA; - Supervisory control & Data Acquisition system
Energy Management EM:-
Supply side EM
Power sector- generation, transmission, interconnection EM & distribution,
Nuclear power
Non-Conventional /Renewable Energy
Oil & Gas
Coal
Chemical Energy Sector (future) e.g. Batteries, hydrogen gas, fuel cells, synthetic fuels.
Bio-energy sector (future) e.g. Ethanol, biodiesels, methanol
Global National Regional State District
Sector
City
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Energy Planning for each Sector
Exploration/ Extraction/ onversion
Processing/ by products/ Cleaning
Storage/ Transport/ Transmission
Distribution/ Supply
Data Collection
Determine the resources available
Strategies are formed Plan the entire energy routes
Determine the demand
Evaluation of trends
Evaluate the economic viability & fixing of tariff/ Rates
Formulate the long/ medium/ short term plan
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Organization Structure
Listing of essential activities
Grouping of activities – whether it is related to space heating, power, fuel,
Decision of responsibilities
Interfacing between the groups
Organization
Non- energy (They just consume energy & produce products)
Energy Intensive (which are using, as well as producing energy + products)
Non- Energy Organization Chart
Operation & maintenance manager with additional
Responsibilities of EM
Line Managers Delegation Interfacing
Plant Manager
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Terms:
Energy Management: EM: The EM is the practical science of techniques and dynamic processes of setting/objectives (task), planning, organizing, arranging materials/finance/human and other required resources, executing, supervising, monitoring, removing bottlenecks to achieve objectives and o set new objectives.
The energy management involves planning, directing, controlling the supply and consumption of energy to maximize the productivity and comforts and to minimize the energy costs, and to minimize the pollution, with consensus , judicious and effective use of energy.
3 steps of EM:
- Energy Audit
- Energy Conservation Measures (ECMs)
- Waste recycling
Steps of Energy Management:
- Strategies
- Administrative actions
- Policy
- Organizational changes
- Training and awareness program
- Association of working personals
- Energy Audit
- Energy Conservation Measures
- Evaluation of the present Energy Consumption
- Implementation of ECMs.
- Monitoring of EC efforts.
THE VALUE OF ENERGY MANAGEMENT
Business, industry and government organizations have all been under tremendous economic and environmental pressures in the last few years. Being economically competitive in the global marketplace and meeting increasing environmental standards to reduce air and water pollution have been the major driving factors in most of the recent operational cost and capital cost
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investment decisions for all organizations. Energy management has been an important tool to help organizations meet these critical objectives for their short term survival and long-term success. The problems that organizations face from both their individual and national perspectives include:
- Meeting more stringent environmental quality standards, primarily related to reducing global warming and reducing acid rain.
Energy management helps improve environmental quality. For example, the primary culprit in global warming is carbon dioxide, CO2. Equation 1.1, a balanced chemistry equation involving the combustion of methane (natural gas is mostly methane), shows that 2.75 pounds of carbon dioxide is produced for every pound of methane combusted. Thus, energy management, by reducing the combustion of methane can dramatically reduce the amount of carbon dioxide in the atmosphere and help reduce global warming. Commercial and industrial energy use accounts for about 45 percent of the carbon dioxide released from the burning of fossil fuels, and about 70 percent of the sulfur dioxide emissions from stationary sources.
CH 4 + 2 O 2 = CO 2 + 2 H 2 O
(12 + 41) +2(216) = (12 + 216) + 2(21 +16) (1.1)
Thus, 16 pounds of methane produces 44 pounds of carbon dioxide; or 2.75 pounds of carbon dioxide is produced for each pound of methane burned. Energy management reduces the load on power plants as fewer kilowatt hours of electricity are needed. If a plant burns coal or fuel oil, then a significant amount of acid rain is produced from the sulphur dioxide emitted by the power plant. Acid rain problems then are reduced through energy management, as are NOx problems. Less energy consumption means less petroleum field development and subsequent on-site pollution.
Less energy consumption means less thermal pollution at power plants and less cooling water discharge. Reduced cooling requirements or more efficient satisfaction of those needs means less CFC usage and reduced ozone depletion in the stratosphere. The list could go on almost indefinitely, but the bottom line is that energy management helps improve environmental quality.
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SOME SUGGESTED PRINCIPLES OF ENERGY MANAGEMENT
If energy productivity is an important opportunity for the nation as a whole, it is a necessity for the individual company. It represents a real chance for creative management to reduce that component of product cost that has risen the most since 1973. Those who have taken advantage of these opportunities have done so because of the clear intent and commitment of the top executive. Once that commitment is understood, managers at all levels of the organization can and do respond seriously to the opportunities at hand. Without that leadership, the best designed energy management programs produce few results. In addition, we would like to suggest four basic principles which, if adopted, may expand the effectiveness of existing energy management programs or provide the starting
point of new efforts. The first of these is to control the costs of the energy function or service provided, but not the Btu of energy. As most operating people have noticed, energy is just a means of providing some service or benefit. With the possible exception of feed stocks for petrochemical production, energy is not consumed directly. It is always
converted into some useful function. The existing data are not as complete as one would like, but they do indicate some surprises. In 1978, for instance, the aggregate industrial expenditure for energy was $55 billion. Thirty-five percent of that was spent for machine drive from electric motors, 29% for feedstocks, 27% for process heat, 7% for electrolytic functions, and 2% for space conditioning and light. As shown in Table 1.1, this is in blunt contrast to measuring these functions in Btu. Machine drive, for example, instead of 35% of the dollars, required only 12% of the Btu. In most organizations it will pay to be even more specific about the function provided. For instance, evaporation, distillation, drying, and reheat are all typical of the uses to which process heat is put. In some cases it has also been useful to break down the heat in terms of temperature so that the opportunities for matching the heat source to the work requirement can be utilized. In addition to energy costs, it is useful to measure the depreciation, maintenance, labor, and other operating costs involved in providing the conversion equipment necessary to deliver required services. These costs add as much as 50% to the fuel cost. It is the total cost of these functions that must be managed and controlled, not the Btu of energy. The large difference in cost of the various Btu of energy can make the commonly used Btu measure extremely misleading. In November 1979, the cost of 1 Btu of electricity was nine times that of 1 Btu of steam coal. Table 1.2 shows how these values and ratios compare in 2005.
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One of the most desirable and least reliable skills for an energy manager is to predict the future cost of energy. To the extent that energy costs escalate in price beyond the rate of general inflation, investment pay backs will be shortened, but of course the reverse is also
true. A quick glance at Table 1.2 shows the inconsistency in overall energy price changes over this period in time. Even the popular conception that energy prices always go up was not true for this period, when normalized to constant dollars. This volatility in energy pricing may account for some business decisions that appear overly conservative in establishing rate of return or payback period hurdles.
Availabilities also differ and the cost of maintaining fuel flexibility can affect the cost of the product. And as shown before, the average annual price increase of natural gas has been almost three times that of electricity. Therefore, an energy management system that controls Btu per unit of product may completely miss the effect of the changing economics and availabilities of energy alternatives and the major differences in usability of each fuel. Controlling the total cost of energy functions is much more closely attuned to one of the principal interests of the executives of an organization — controlling costs.
NOTE: The recommendation to control energy dollars and not Btus does not always apply. For example, tracking building energy use per year for comparison to prior years is best done with
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New equipment can be installed to reduce the cost of the function.
The starting point for reducing costs should be in achieving the minimum cost possible with the present equipment and processes. Installing management control systems can indicate what the lowest possible energy use is in a well-controlled situation. It is only at that point when a change in process or equipment configuration should be considered. An equipment change prior to actually minimizing the expenditure under the present system may lead to oversizing new equipment or replacing equipment for unnecessary functions.
The third principle is to control and meter only the main energy functions— the roughly 20% that make up 80% of the costs. As Peter Drucker pointed out some time ago, a few functions usually account for a majority of the costs. It is important to focus controls on those that represent the meaningful costs and aggregate the remaining items in a general category. Many manufacturing plants in the United States have only one meter, that leading from the gas main or electric main into the plant from the outside source. Regardless of the reasonableness of the standard cost established, the inability to measure actual consumption against that standard will render such a system useless. Submetering the main functions can provide the information not only to measure but to control costs in a short time interval. The cost of metering and submetering is usually incidental to the potential for realizing significant cost improvements in the main energy functions of a production system.
The fourth principle is to put the major effort of an energy management program into installing controls and achieving results. It is common to find general knowledge about how large amounts of energy could be saved in a plant. The missing ingredient is the discipline necessary to achieve these potential savings. Each step in saving energy needs to be monitored frequently enough by the manager or first-line supervisor to see noticeable changes. Logging of important fuel usage or behavioral observations are almost always necessary before any particular savings results can be realized. Therefore, it is critical that an energy director or committee have the authority from the chief executive to install controls, not just advise line management. Those energy managers who have achieved the largest cost reductions actually install systems and controls; they do not just provide good advice.
As suggested earlier, the overall potential for increasing energy productivity and reducing the cost of energy services is substantial. The 20% or so improvement in industrial energy productivity since 1972 is just the beginning. To quote the energy director of a large chemical company: “Long-term results will be much greater.” Although no one knows exactly how much we can improve productivity in practice, the American Physical
Society indicated in their 1974 energy conservation study that it is theoretically possible to achieve an eightfold improvement of the 1972 energy/production ratio.9 Most certainly, we are a
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long way from an economic saturation of the opportunities (see, e.g., Ref. 10). The common argument that not much can be done after a 15 or 20% improvement has been realized ought to be dismissed as baseless. Energy productivity provides an expanding opportunity, not a last resort.
Energy Conservation measures in boilers:
Effect of preheat air temp on fuel saving:
Energy conservation in Transportation: The manufacturing unit should be located near source of raw material to minimize the transportation of raw material which is usually more than finished products.
- Incase of agricultural products like cotton, fruits a primary processing may be done in the rural area, so that an intermediate product is only transported which is lesser height than the total produce.
- The service unit should be located near the consumer to reduce the unnecessary transportation cost.
- The proper quantity and packing of materials should be selected for economic transportation.
- The economic means transportation should be chosen from the various available means. i.e. ship, rail, truck, belt conveyor etc.
- The effective use of local resources in each area/zone should be encouraged with innovation rather than encouraging material consumption from large distances.
- Design the development and manufacturing of such transport vehicles which consume minimum fuel and lubricants.
- Design the development and manufacturing of such transport vehicles based on renewable source of energy.
- The operation of automobile should be so performed as to reduce the consumption of fuel and lubricants.
