Cogeneration of Bagasse

Cogeneration of bagasse is one of the most attractive and successful energy projects that have already been demonstrated in many sugarcane producing countries such as Mauritius, Reunion Island, India and Brazil. Combined heat and power from sugarcane in the form of power generation offers renewable energy options that promote sustainable development, take advantage of domestic resources, increase profitability and competitiveness in the industry, and cost-effectively address climate mitigation and other environmental goals.

According to World Alliance for Decentralized Energy (WADE) report on Bagasse Cogeneration, bagasse-based cogeneration could deliver up to 25% of current power demand requirements in the world’s main cane producing countries. The overall potential share in the world’s major developing country producers exceeds 7%. There is abundant opportunity for the wider use of bagasse-based cogeneration in sugarcane-producing countries. It is especially great in the world’s main cane producing countries like Brazil, India, Thailand, Pakistan, Mexico, Cuba, Colombia, Philippines and Vietnam. Yet this potential remains by and large unexploited.

Using bagasse to generate power represents an opportunity to generate significant revenue through the sale of electricity and carbon credits. Additionally, cogeneration of heat and power allows sugar producers to meet their internal energy requirements and drastically reduce their operational costs, in many cases by as much as 25%. Burning bagasse also removes a waste product through its use as a feedstock for the electrical generators and steam turbines.

Most sugarcane mills around the globe have achieved energy self-sufficiency for the manufacture of raw sugar and can also generate a small amount of exportable electricity. However, using traditional equipment such as low-pressure boilers and counter-pressure turbo alternators, the level and reliability of electricity production is not sufficient to change the energy balance and attract interest for export to the electric power grid.

On the other hand, revamping the boiler house of sugar mills with high pressure boilers and condensing extraction steam turbine can substantially increase the level of exportable electricity. This experience has been witnessed in Mauritius, where, following major changes in the processing configurations, the exportable electricity from its sugar factory increased from around 30-40 kWh to around 100–140 kWh per ton cane crushed. In Brazil, the world’s largest cane producer, most of the sugar mills are upgrading their boiler configurations to 42 bars or even higher pressure of up to 67 bars.

Technology Options

The prime technology for sugar mill cogeneration is the conventional steam-Rankine cycle design for conversion of fuel into electricity. A combination of stored and fresh bagasse is usually fed to a specially designed furnace to generate steam in a boiler at typical pressures and temperatures of usually more than 40 bars and 440°C respectively. The high pressure steam is then expanded either in a back pressure or single extraction back pressure or single extraction condensing or double extraction cum condensing type turbo generator operating at similar inlet steam conditions.

Due to high pressure and temperature, as well as extraction and condensing modes of the turbine, higher quantum of power gets generated in the turbine–generator set, over and above the power required for sugar process, other by-products, and cogeneration plant auxiliaries. The excess power generated in the turbine generator set is then stepped up to extra high voltage of 66/110/220 kV, depending on the nearby substation configuration and fed into the nearby utility grid. As the sugar industry operates seasonally, the boilers are normally designed for multi-fuel operations, so as to utilize mill bagasse, procured Bagasse/biomass, coal and fossil fuel, so as to ensure year round operation of the power plant for export to the grid.

Latest Trends

Modern power plants use higher pressures, up to 87 bars or more. The higher pressure normally generates more power with the same quantity of Bagasse or biomass fuel. Thus, a higher pressure and temperature configuration is a key in increasing exportable surplus electricity.

In general, 67 bars pressure and 495°C temperature configurations for sugar mill cogeneration plants are well-established in many sugar mills in India. Extra high pressure at 87 bars and 510°C, configuration comparable to those in Mauritius, is the current trend and there are about several projects commissioned and operating in India and Brazil. The average increase of power export from 40 bars to 60 bars to 80 bars stages is usually in the range of 7-10%.

A promising alternative to steam turbines are gas turbines fuelled by gas produced by thermochemical conversion of biomass. The exhaust is used to raise steam in heat recovery systems used in any of the following ways: heating process needs in a cogeneration system, for injecting back into gas turbine to raise power output and efficiency in a steam-injected gas turbine cycle (STIG) or expanding through a steam turbine to boost power output and efficiency in a gas turbine/steam turbine combined cycle (GTCC). Gas turbines, unlike steam turbines, are characterized by lower unit capital costs at modest scale, and the most efficient cycles are considerably more efficient than comparably sized steam turbines.

Clean Energy Investment Forecast for 2016

renewables-investment-trendsGlobal interest in clean energy technologies reached new heights last year and 2016 promises to be another record-breaker. The year 2015 witnessed installation of more than 121 GW of renewable power plants, a remarkable increase of 30% when compared to 2014. With oil and gas prices tumbling out to unprecedented levels, 2016 should be a landmark year for all clean energy technologies. As per industry trends, solar power is expected to be the fastest-growing renewable power generation technology in 2016, closely followed by wind energy. Among investment hotspots, Asia, Africa and the Middle East will be closely watched this year.

Investment Forecast for 2016

Clean energy is rapidly becoming a part of mainstream investment portfolios all over the world. In 2016, a greater attention will be focused on renewable energy, mainly on account of the Paris Framework and attractive tax credits for clean energy investments in several countries, especially USA.

Infact, the increasing viability of clean energy is emerging as a game-changer for large-scale investors. The falling prices of renewable power (almost 10% per year for solar), coupled with slump in crude oil prices, is pulling global investors away from fossil fuel industry. At the 2016 UN Investor Summit on Climate Risk, former US vice president Al Gore said, “If this curve continues, then its price is going to fall “significantly below the price of electricity from burning any kind of fossil fuel in a few short years”.

There has been an astonishing growth in renewable generation in recent years. “A dozen years ago, the best predictors in the world told us that the solar energy market would grow by 2010 at the incredible rate of 1 GW per year,” said Gore. “By the time 2010 came around, they exceeded that by 17 times over. Last year, it was exceeded by 58 times over. This year, it’s on track to be exceeded by 68 times over. That’s an exponential curve.”

China will continue to dominate solar as well as wind energy sectors

China will continue to dominate solar as well as wind energy sectors

As per industry forecasts, China will continue its dominance of world PV market, followed closely by the US and Japan. Infact, USA is anticipated to overtake Japan as the second largest solar market this year. India, which is developing a highly ambitious solar program, will be a dark horse for cleantech investors. The top solar companies to watch include First Solar, Suntech, Canadian Solar, Trina Solar, Yingli Solar, Sharp Solar and Jinko Solar.

Morocco has swiftly become a role model for the entire MENA. The government’s target of 2GW of solar and 2GW of wind power by 2020 is progressing smoothly. As for solar, the 160MW Noor-1 CSP is already commissioned while Noor-2 and Noor-3 are expected to add a combined 350MW in 2017.

China will continue to lead the global wind energy market in 2016, and is on course to achieve its target of 200 GW of installed wind capacity by 2020. Other countries of interest in the wind sector will be Canada, Mexico, Brazil and South Africa. The major wind turbine manufacturers to watch are Siemens, Vestas, Goldwind, Gamesa and GE.

Conclusion

To sum up, the rapid growth of global renewable energy sector in the past few years is the strongest signal yet for investors and corporations to take the plunge towards green energy and low-carbon growth. As the UN chief Ban Ki-moon famously said, “It marks the beginning of the end of growth built solely on fossil fuel consumption. The once unthinkable has now become unstoppable.”