WHAT WOULD YOU DO IF YOU were the CEO of a company that guzzled embarrassing amounts
of fossil fuels and left a big, fat, carbon footprint? Change over gradually to alternatives such as solar, or wind, right? But data show that the actual per megawatt (MW) cost of these are usually higher than commonly believed.
Then, they are unreliable. In the windy belt of India—the west coast and Tamil Nadu—winds tend to be strongest at night and during the monsoons, while power usage is highest during summer afternoons.
Using some of the waste that your factories produce to create energy would then be a truly smart thing to do.
The good news is that a lot of the energy released as a result of industrial activity can be recycled to produce more energy. “Technology is now readily available to capture the waste heat to either produce power or steam, or route it back into the system, thereby cutting the need to buy energy,” says M.S. Unnikrishnan, managing director and CEO of Thermax, a manufacturer of equipment for such applications.
Bureau of Energy Efficiency (BEE) statistics show that eight industries—power (thermal), iron and steel, cement, fertilisers, textile, aluminium, pulp and paper, and chlor-alkali—account for over half the energy consumed by the country. But, according to conservative estimates, nearly a third of the energy used by these sectors turns into waste in the form of flue gases, steam, and radiation heat, among others.
In a typical thermal power plant, only 40% of the energy released by burning coal gets converted into electricity and the rest gets lost in the surroundings as waste heat. Similarly a blast furnace operates at a maximum efficiency of 60%, while a cement kiln converts just 45% to 50% of the calorific value of coal, according to estimates by Shirish Deshpande, director, Energetic Consulting, one of the country’s leading energy auditors. Energetic helps companies map their energy usage and come up with strategies and solutions to reduce it.
THE EARLY EXPERIMENTS have begun. Tata Power, for instance, operates two plants, at Haldia in West Bengal, and Jamshedpur in Jharkhand, that use waste gases from Tata Steel units to jointly generate 240 MW of electricity, enough to light up an average Indian district. The plant runs like any other thermal power unit and now accounts for nearly 8% of all Tata Power-installed capacity. Tata Steel and Tata Power have also signed an agreement for the construction of a 525 MW combined heat and power plant at Corus’s IJmuiden works in the Netherlands. Back home, Thermax recently bagged an order to construct a similar plant for Rashtriya Ispat Nigam’s Visakhapatnam steel plant with a name plate capacity of 120 MW. Again, JSW Steel generates 100 MW at its steel plant in Torangallu, Karnataka.
It’s easy science. Steel blast furnaces generate gases at high temperature with properties similar to natural gas that can be used to generate electricity. Super-heated gases are also released when coke (used in steel making) is made by heating coal at high temperatures. These gases can be fed into a steam boiler connected to a steam turbine to generate power. A recently commissioned 5 million tonne integrated steel plant at Sepetiba Bay, Brazil, supports a 480 MW combined cycle power plant.
Gases are also produced while making cement—limestone is cooked at an extremely high temperature, using coal, to produce clinker, a byproduct—which can be used to generate power. The technology was first pioneered by the Japanese, and is now common in Chinese cement plants.
In India, it was pioneered by Shree Cement. The Kolkata-headquartered cement major with a combined production capacity of 13.5 million tonnes uses flue gases from its kilns to produce 46 MW of power, nearly a third of its energy needs. The result: Shree Cement’s carbon dioxide emission per tonne of cement produced is down by nearly a third.
Its much larger peer, ACC, the country’s oldest and second-largest cement maker, is now adopting the same route to cut its energy usage and the overall carbon footprint. “Being part of the Holcim group, ACC has an aggressive internal target to cut energy usage and our carbon footprint. Waste heat recovery is one of the levers for us to achieve this and we have made it mandatory for all our new cement units,” says K.N. Rao, director, energy and environment, ACC.
According to him, waste heat recovery systems can generate up to 5 MW of power for every million tonne of cement produced, depending on where the factories are located. (The moisture content in limestone determines the amount of power generated; higher percentages lead to less power.) Rao estimates that India can easily generate 700 MW of power every year, given its annual cement production of 250 million tonnes last year.
ACC is trying other initiatives as well, such as burning municipal and industrial waste (often labelled collectively as alternative fuels). Today, 1% of ACC’s energy requirements are fulfilled by using such waste to power its kilns. In five years, that figure should rise to 5% and thereafter, eventually to 20%.
The company is also considering using hybrid systems to manage its energy requirements, a combination of a biomass-based power plant, solar concentrator, and waste heat recovery power system. “It is still at a conceptual stage but this combined with alternative fuels can drastically cut our carbon footprint,” says Rao. Today, ACC emits 546 kg of carbon dioxide for every tonne of cement produced; Rao is targeting to bring it down to 350 kg.
“Standalone solar or wind systems can’t meet our energy needs. But if we marry them with biomass-based thermal plants, they could potentially power thousands of villages without increasing India’s carbon footprint,” says Thermax’s Unnikrishnan. The company is currently running a pilot project at a small village near Pune to provide power through hybrid systems to 1,500 of its residents. The hope: If the technology is scalable, it could partially solve the energy needs of states such as Uttar Pradesh and Bihar, which generate loads of biomass (mainly agriculture residue) but don’t have access to fossil fuels such as coal and gas.
Some amount of evangelising is also being done by the likes of Pune’s Transparent Energy Systems, which manufactures waste heat recovery systems. “Though waste heat recovery systems cost two-and-half times more to install than conventional coal-fired systems, the pay back period can be as low as four years due to very low operating and maintenance costs and savings in energy purchases,” says S.S. Gharpure, Transparent’s vice president, marketing and business development.
Waste heat recovery systems accounted for 80% of Transparent’s revenue of Rs 85 crore (the rest comes from the company’s other business such as boilers, heaters, and absorption refrigeration plants) last year from just half of the company’s revenue three years ago.
Gharpure, however, feels the projects under implementation are, at best, a drop in the ocean compared to the potential. He argues that barring cement and a few projects in the iron and steel industry, there is not much interest from other energy-guzzling industries such as chlor-alkali, fertilisers, pulp and paper, and refineries. According to him, another problem is the use of dated technology, which makes it expensive and technologically challenging to install waste heat recovery systems. “It’s far easier and cheaper to put up a waste heat recovery system if it has been incorporated in the plant from the design stage itself,” he says.
Others, like ACC’s Rao, say that as more and more companies begin investing in these technologies, prices should fall, and make the investments viable for small players. “Before the Shree Cement project, waste heat recovery-based power plants used to cost Rs 14 crore per MW, now it's down to Rs 8 crore per MW.”
The huge T3 terminal at Delhi airport is cooled by eight 2,500 tonne airconditioning units. A typical 1.5 tonne machine consumes around 1.5 units of electricity for every hour of operation, and dumps roughly 11 kg of carbon dioxide every night. Little wonder then, that T3 adds over 400 tonnes of carbon dioxide to the atmosphere every day. The calculation is based on the fact that nearly 85% of India’s electricity comes from coal-fired plants, which emit nearly 900 g of carbon dioxide for every unit of power generated.
“In the next few years, airconditioning and cooling applications are expected to consume 35% to 40% of all electricity produced in India,” says Gaurang Pandya, managing director of Carrier India, a leading player in home and central airconditioning. A big chunk of this comes from cooling applications for factories and large companies. With power in short supply, and companies getting more conscious of their carbon footprint, airconditioning manufacturers are trying to come up with energy-efficient solutions.
The sector is witness to a big churn of ideas, with vendors such as Thermax pushing for absorption chillers that use steam generated from solar concentrators, which cut the dependence on grid power for central airconditioning by up to 100% depending on the location. In this technology, a heat source, such as steam from a solar concentrator, is used to drive the cooling system. Carrier is focussing on technologies such as variable drives, which reduce the speed of the fans and compressors according to the load conditions to get a 25% to 30% reduction in energy usage.
Then there are startups such as Pune-based Toro Green Tech India, which peddles technology based on a modified desert cooler that claims to cut energy consumption of ACs by up to 90% and can even run on batteries or solar power.
“According to us, the best use of solar energy is for cooling,” says Thermax’s Unnikrishnan, although, as he adds, the technology is still evolving and is expensive right now. This is an efficient technology for a tropical country like India, but the downside is its high capital cost, and bulky solar concentrators that eat up real estate.
