News

India - Energy efficiency

Issued at 2010-11-03



Energy efficiency in India, why and how

 

Some practical measures that can be adopted by foundries to improve the bottom line are given here by foundry consultant R Gopal based on a presentation he made at the 58th Indian Foundry Congress, Ahmendabad, (February 2010).

 

The Indian energy scene

Energy is the single most important factor in India’s race to economic superpower status and in 2010-11 alone the country is expected to face a shortage of 12.6% – its energy requirement is estimated at 8,40,544 million units with peak demand at 1,18,794 Megawatts; availability is 7,62,115 million units and 1,03,816 Megawatts respectively. It is estimated that by 2030 India will be the third largest energy consumer after China and USA.

The foundry industry is energy intensive and has an important role to play from an environmental point of view whilst seeking to develop and play an important role in the nation’s continued economic development.

There are a number of barriers to energy efficiency:

  • Lack of awareness, education and training
  • Economic and market distortions
  • Lack of standardisation and labelling on equipment and devices
  • Lack of financing
  • Lack of effective coordination
  • Complacency – a feeling that everything possible has been done
  • A mistaken feeling that energy monitoring and energy reduction equipment is expensive

India’s energy intensity per unit of GDP is 3.7 times that of Japan, 1.4 times that of Asia and 1.5 times of that USA. This is indicative of a high wastage of energy but at the same time a very high energy saving potential. There are also many instances of power shortages in the country running at a peak of 13% with an average of 8%.

India is the second most populous country in the world and is growing at an annual rate of 2%; it currently has very low per capita energy consumption - 600kWh compared with 1300 kWh in China and 14000 kWh in the USA. It is also the sixth largest energy consumer in the world and is experiencing an average GDP growth rate of 7% per annum.

At the same time it has an installed capacity of 1,50,323 MW, just 3% of the world’s capacity, and coal still accounts for more than 50% of fuel for power generation (89% of fuel required for India’s power generation is locally available).

 

 

India has plentiful wind, sun, rainfall and talent but is poor in hydrocarbons. Thus it is rich in resources which can fuel a clean future and should take a lead in green energy technologies for its villages.

There is an average power shortage of 8% between demand and supply and 13% in peak power demand. This situation is likely to continue even into 2015.

Added to this, roughly 35% is calculated to be the accounted plus unaccounted transmission losses.

The demand for energy is growing manifold and the energy sources are becoming scarce and more costly so the efficient use of energy and its conservation is, therefore, a must.  

Indian Government plans for energy

 

The Indian government has plans to reduce energy consumption by 5% (nearly 10,000 MW) by 2012 and has set an electricity energy policy (in 2005) with the following objectives:

  • Access to electricity to all households
  • Availability of power to fully meet demand
  • Supply of reliable and quality power
  • Emphasis on use of non-conventional energy sources

It also has an Energy Vision as follows:

  • Coal to remain mainstay of future energy needs
  • Nuclear power generation to be maximised
  • Emphasis on renewable sources of energy including hydro
  • Full development of hydro potential by 2025
  • 15% savings to be achieved by energy conservation by 2012
  • Provide electricity to all households in next five years
  • Shift to more efficient fuels (LPG etc.) for cooking for all households in next 10-15 years

There is now a ‘national mission’ for enhanced energy efficiency. This mission will enable Rs75,000 of energy efficiency measures and will help save, by 2015, 5% of the annual energy consumption. In addition, the partial risk guarantee facility guarantees loans to energy efficient measures and a venture capital fund will support investments in the manufacture of energy efficiency products.

 

Renewable energy sources

India has a vast potential for renewable energy sources, especially in areas such as solar power, biomass and wind power. The current installed capacity of renewable energy – solar, biomass and wind - is less than 5% of India’s total installed generation capacity. Due to the mounting demand for energy and increasing population, switching from non renewable fossil fuels to other energy sources is not an option but a necessity and there is a great scope for enhancing it to 15% by 2012.

The options to be considered follow:

 

Biomass

Biomass is a renewable energy, unlike natural resources. It is linked closely with rural economies and units with up to 100 kW per generating capacity are ideal for local energy requirements in rural areas.

But there is a problem: Why would a rural person show interest when energy is available free from the grid?

Estimated potential 22000 MW

 

Wind energy

India currently enjoys fourth position in the world in installed wind energy but projects are based mainly on fiscal benefits, many plants are not operating and there is a low average load factor. However the estimated potential is 40,000MW gross and 15,000MW is feasible.

 

Solar energy

In 1931 Thomas Alva Edison said: “I’d put my money on the sun and solar energy. What a source of power! I hope we don’t have to wait till oil and coal run out before we tackle that.”

Solar energy offers great potential in India since there is a high solar incidence in the country (there are about 300 clear sunny days in a year in most parts of India and the daily average solar energy incident over India varies from 4 to 7 kWh/m2). A piece of square land 55 km2 each in the Thar Desert could generate enough electricity to equal the entire power generation in the country today. But existing solar harvesting technologies are expensive and cannot compete with fossil fuels on cost: solar power is Rs15/kWh compared with coal based at Rs.3/kWh and liquid fuel at Rs8/kWh

There is now Governmental support in the form of subsidies and with a national solar mission to envisage a capacity addition of around 107,000 MW by 2015.  Technological developments are promising cheaper solutions for solar energy capture.

 

Energy efficiency – how to achieve improvements?

Many companies now have a quality policy and an environment policy, but how many have an energy policy?

It is essential that there is a company-wide energy policy driven through an energy committee, and its implementation needs to be monitored and reviewed regularly. Energy management programmes are required and need to be implemented and there needs to be top management commitment so that energy and its reduction remains a board level agenda item.

 

Some practical steps for improving energy efficiency in foundries

Here are some initial questions for consideration by all foundries:

1.                Have we undertaken an assessment of energy efficiency?

2.                Can we benefit from implementing an energy monitoring program to manage energy use?

3.                Can we optimise the efficiency of our metal melting and holding processes?

4.                Can we optimise the efficiency of the ancillary services in the operation?

5.                Can we benefit from investing in energy control systems to shut down equipment when not in use?

6.                Can we develop greater staff awareness of energy efficiency and run an effective ‘switch-off’ program?

7.                Can we improve the ladles and refractory materials used in the furnaces?

8.                Can we recover energy from any sources for reuse elsewhere in the foundry?

9.                Can we benefit from investing in energy efficient equipment and up-grading old equipment (e.g. lighting, ladle        preheating, sand reclamation, furnaces etc)?

The main areas for energy usage are listed below and then considered in turn.

 

  • Compressed air usage
  • Operational controls for energy saving and economy
  • Better recovery in terms of input (reduce waste)
  • Energy efficient processes
  • Waste heat recovery
  • Energy monitoring and audit

 

Compressed air

Air is free but compressed air is not! Compressed air can be considered colourless gold in the industry.

Leakage is a major cause of energy wastage. A 3 mm hole will result in a 26 cfm leak and a financial loss of Rs1,93,000 (£2,624.56).

Steps recommended to arrest leakage:

  • Listen for leaks during idle periods
  • Conduct leak test at least once a fortnight and record quantum of leaks area visible.
  • Optimize nozzle size (Where different types of machines are used requiring nozzles for blowing air, it is prudent to use different nozzle sizes depending on the machine size and air required).

Other considerations:

  • Operating at 120 psg when 100 psg is sufficient consumes 10% more energy.
  • Segregate H.P and L.P compressed air – the compressor power consumption is directly proportional to the operating pressure. There is potential to save energy by segregating the high pressure and low pressure compressed air lines.
  • Create an awareness program by displaying posters on leakage.
  • Appoint a service person who is responsible for attending to all the leaks and ensure zero leak of compressed air at any given point of time.

By following the above advice a foundry, on a conservative basis, can achieve an energy saving of 30%.

Installation of a variable frequency drive, the compressor need not operate in load / un-load condition:

  • Saves the un-load power consumption.
  • After installing the VFD it is possible to maintain a pressure band of 7.6 -7.7 kg/cm2. Power consumption of the compressor, which is operating constantly at a particular pressure (with VFD control) comes down by around 5% and is completely avoided during un-load.

 

Operational controls for energy saving and economy

Keep tapping temperatures as low as possible. Conduction and radiation losses of a one tonne high-frequency furnace 500 Hz and 900kW at a tapping temperature of 1500°C are 50 kW and 35 kW respectively. These losses can be reduced by approximately 10 kW by having a tapping temperature of 1400°C. To keep the tapping temperature lower, optimise inoculation, reduce ladle travelling distance, preheat the ladle and cover it during metal transfer. It is good practice to display the tapping temperature.

Keep the furnace cover closed as far as possible. Radiation loss from the molten metal surface is proportional to the fourth power of temperature. Thus the heat loss at a temperature of around 1500°C comes to 60-70 kW/m2.

 

Hold the molten metal at as low a temperature as possible and for the shortest time. Molten metal should be held, when required, at a low temperature, or turn off the power supply. The rated power should be turned on to heat up again, any chemical analysis of molten metal, preliminary furnace tests and temperature measurements should be performed quickly, and preparatory operations should be performed so that there are no delays from mis-matching with mould assembly or waiting for the crane.

 

Covering the ladle always reduces heat losses. One small foundry was able to save 3 units per melt which equated to 60 units/day and 1500 units/month. At Rs5/-unit (£0.07p), the annual saving was Rs1,25,000 (£1,701.33).

 

Better recovery in terms of input (reduce waste)

How many tonnes of metal do we melt for each tonne of usable castings? In the worst case, for every tonne of casting produced for sale, up to two tonnes of metal are melted. Consider the major areas of loss (e.g. melt losses, spilt metal, pigged metal, runners and risers, reject castings, or grinding losses). Can metal losses be reduced by minimising metal spills, or reducing over or under pours through precision pouring techniques? There are often opportunities to redesign, optimise or change the casting process used to increase the metal yield and to work with customers to redesign the casting to reduce its weight or improve its casting characteristics? Can the gating system be redesigned - gating systems (i.e. runners, risers and sprues) are often larger than necessary and wall thicknesses are sometimes over-specified to compensate for porosity and other metal quality problems. Redesign can reduce machining allowances to reduce grinding losses or even eliminate some fettling operations from the foundry?

Excess metal melted means more energy used in melting and holding the metal, increased capital costs for unnecessary metal handling capacity, increased fettling costs, unnecessary metal collection and sorting time, increased maintenance of equipment, lost time that could be used for value adding activities and customer relations issues. These all affect the bottom line.

Raw material selection and control is also significant since sand or rust in scrap reacts with the furnace refractory to form slags. If slags are formed to about 1% during melting of 3 tonnes of iron, the power loss at 1500°C is about 10kWh/t.

In addition the raw material charged should be as dense as possible to improve melting efficiency.

 

Energy efficient processes – some suggestions

  • Operate the furnace at its constant rated power. The maximum capacity of the furnace can be attained and power consumption rate can be reduced
  • Install an automatic power factor controller (APFC) .The APFC relay will automatically control the switching of the capacitor.
  • Cooling towers - change blades from aluminium to FRP. Consider the case of a cooling tower with aluminium blades. The load of the cooling tower under working condition is 32kW. With FRP blades which are lighter than aluminium, the load now is 25kW. The energy saving is 32–25kW = 7 kW @ 16 hours/day = 112 kW.
  • Introduce a low wattage compressor – in a foundry with very minor machining facility the provision of a low,15 kW compressor (compared with a 55 kW compressor), was sufficient to run the entire foundry and machine-shop resulted in a saving of approximately 30 units saved whenever the small compressor alone was sufficient.
  • Cooling tower – installed auto controller reduces the running time of the cooling tower. Saving 3 hours/day. 7.5 kW x 0.8 pf x 3 hrs = 15 units/day.  Annual savings = Rs23,400 (£318.21).
  • Replacement of partially loaded motors with smaller capacity motors - identify the motors that are found to operate in an under-loaded condition even when the load on these motors was enhanced to the maximum.  These motors may be replaced with smaller, appropriate capacity motors for better energy efficiency. With the number of motors running all over the foundry, this offers considerable savings.
  • Use of natural light through the use of transparent roofing sheets - 170 W x 12 fittings x 8 hours = 15.4 u/day.  Annual savings = Rs24,050 (£327.05).
  • Replacement of high-speed diesel (HSD) fired burners with furnace oil fired burners. 50% of the additional cost incurred in HSD firing can be saved.
  • Replace conventional copper ballast with HF electronic ballast. A power consumption of 15kW/tube can come down to 2 kW/tube.
  • Replace filament indication lamps in control panels with LED lamps. Filament lamps consume 9-14 watts per lamp whereas the LED lamps are 0.5 watt
  • Replace conventional motors with energy efficient motors
  • Use 36 watt slim tubes instead of 40 watt conventional fluorescent tubes. CFL bulbs preferred.
  • Increase emissivity of heat treatment furnaces by coating the hot face.

 

Waste heat recovery

This relates to the recovery of the maximum energy that is otherwise being wasted in thermal operations. Waste heat recuperators installed to tap the sensible heat from the flue gas coming out of the furnaces, evaporating cooling systems in reheating furnaces and other high temperature installations of a plant are all examples of the drive to recover and reuse a part of the energy that would have gone waste. A hot blast cupola which uses the sensible heat of the exhaust gases to heat the incoming air blast is a good example.

 

Energy efficient process – case study

The foundry had an idle mains frequency induction furnace which was earlier being used for melting cast iron. This furnace was changed over to alumina lining and used for aluminium swarf melting. The original furnace shell had a capacity of 600kg Al and was powered by 460kW. The crucible was changed to 1100 kg with the same power pack. Al swarf melting is now being carried out using 12 heats per day consuming 725 units/tonne of Al. These improvements brought down the unit consumption from 1170 units per tonne of Al to 725 units per tonne of Al. 

 

Energy monitoring and audit

The following are all recommendations for all foundries:

  • Installation of proper metering and data collection of all major power consuming equipment and operating parameters.
  • Formation of energy conservation committee to study specific energy consumption and sustain the same.
  • Energy audit by an independent authority.
  • Facts and figures collected on energy and production to be displayed to create an awareness.
  • Learn from others who have implemented energy saving measures.

 

Conclusion

In conclusion many of the methods that have been identified here are indicative and it should be noted that practices will vary from foundry to foundry depending on the alloy, the process, the weight of the castings, volume, application, mechanisation, type of equipments and a host of other factors.

However, it should be noted that all foundries can identify areas where energy efficiencies can be achieved and these will help from an environmental point of view which is of course laudable, but also with the bottom line and profitability. What is important is the will to conserve energy.

 

The World Foundry Organization’s Energy Commission organises a broad range of events under the chairmanship of Vijay Saha, these included a presentation at the 8th International Manufacturing Research Conference at Durham Universitylast month and a proposed Euro-Asia Energy Conservation Symposium to be held in the early part of 2011. For more information contact the WFO general secretary Andrew Turner on Tel: +44 (0) 121 601 6976, email: andrew@thewfo.com  web: www.thewfo.com


Source: Foundry Trade Journal



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