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    The Bowen Group, one of Ireland's biggest construction groups has announced a strategic move into the biomass energy sector. It is planning a €25 million investment over the next five years to fund up to 100 projects that will create electricity from biomass. Its ambition is to install up to 135 megawatts of biomass-fuelled heat from local forestry sources, which is equal to 50 million litres or about €25m worth of imported oil. Irish Examiner - September 16, 2007.

    According to Dr Niphon Poapongsakorn, dean of Economics at Thammasat University in Thailand, cassava-based ethanol is competitive when oil is above $40 per barrel. Thailand is the world's largest producer and exporter of cassava for industrial use. Bangkok Post - September 14, 2007.

    German biogas and biodiesel developer BKN BioKraftstoff Nord AG has generated gross proceeds totaling €5.5 million as part of its capital increase from authorized capital. Ad Hoc News - September 13, 2007.

    NewGen Technologies, Inc. announced that it and Titan Global Holdings, Inc. completed a definitive Biofuels Supply Agreement which will become effective upon Titan’s acquisition of Appalachian Oil Company. Given APPCO’s current distribution of over 225 million gallons of fuel products per year, the initial expected ethanol supply to APPCO should exceed 1 million gallons a month. Charlotte dBusinessNews - September 13, 2007.

    Oil prices reach record highs as the U.S. Energy Information Agency releases a report that showed crude oil inventories fell by more than seven million barrels last week. The rise comes despite a decision by the international oil cartel, OPEC, to raise its output quota by 500,000 barrels. Reuters - September 12, 2007.

    OPEC decided today to increase the volume of crude supplied to the market by Member Countries (excluding Angola and Iraq) by 500,000 b/d, effective 1 November 2007. The decision comes after oil reached near record-highs and after Saudi Aramco announced that last year's crude oil production declined by 1.7 percent, while exports declined by 3.1 percent. OPEC - September 11, 2007.

    GreenField Ethanol and Monsanto Canada launch the 'Gro-ethanol' program which invites Ontario's farmers to grow corn seed containing Monsanto traits, specifically for the ethanol market. The corn hybrids eligible for the program include Monsanto traits that produce higher yielding corn for ethanol production. MarketWire - September 11, 2007.

    Ethanol Statistics, a new industry information resource, reports that U.S. petroleum refiners Citgo and Valero are the top 2 ethanol importing companies in the United States in the first 6 months of 2007. Overall imports were up 7.64% compared to the same period in 2006, from 193,620 gallons to 208,404 gallons. Chevron imported 43% less, whereas Noble and ConocoPhilips' imports were up 255% and 372% respectively. Data are reported in 'The United States Ethanol Market 2007’, which also provides a breakdown of U.S. ethanol production costs and a detailed analysis of U.S. consumption and production. Ethanol Statistics - September 10, 2007.

    The government of British Columbia launches a $100,000 study into the production of biogas, heat, power and clean water from household waste streams. Raw sewage water can be cleaned by microbial fuel cells that deliver electricity as they clean the water; other technologies include classic anaerobic fermentation. Canada.com - September 10, 2007.

    Saudi Aramco in its Annual Review 2006 said that last year the company's crude oil production declined by 1.7 percent, while exports declined by 3.1 percent, compared with the previous year. Crude oil production in 2006 averaged 8.9 million barrels of oil a day (b/d) and exports 6.9 million b/d. Saudi Aramco - September 9, 2007.

    Chinese packaging manufacturer Livan Biodegradable Product Co. Ltd. will build plants in Alsozsolca and Edeleny in eastern Hungary at a combined cost of €18 million by 2009, the Hungarian economics ministry says. The plants, which will employ 800 people, are planned to produce initially 50, 000 metric tons a year of environmentally-friendly packaging material, and double that amount by a later date. Livan will use corn to manufacture biodegradable packaging boxes with similar properties to petroleum-based plastic boxes used in the food industry. Dow Jones Newswires - September 7, 2007.

    South Korea aims to raise biodiesel content in domestic diesel to 3 percent from the current 0.5 percent by 2012, Seoul's energy ministry said today. The government was initially set last year to impose a mandatory 5 percent blend, in line with the level targeted by the European Union by 2010, but the country's powerful refining lobby opposed the move, forcing it to push back the target, according to market sources. Reuters - September 7, 2007.

    Virent Energy Systems, Inc. announced today that it has closed a US$21 million second round of venture financing. Investor interest in Virent was driven in large part by the Company’s continued development of its innovative BioForming process beyond its traditional hydrogen and fuel gas applications and toward the production of bio-based gasoline, diesel, and jet fuels. Virent Energy Systems - September 6, 2007.

    The U.S. National Ethanol Vehicle Coalition (NEVC) announces that 31 models of motor vehicles will be offered in the U.S. with an E85 capable engine in 2008. Chrysler, Ford, General Motors, Nissan and Mercedes Benz will all offer flexible fuel vehicles (FFVs) in the coming year. The NEVC expects 750,000 such FFVs will be produced in 2008. National Ethanol Vehicle Coalition - September 5, 2007.

    GreenHunter BioFuels, Inc., has begun commercial operations with the start-up of a 1,500 barrel per day methanol distillation system. Methanol is an alcohol used to transesterify vegetable oils into biodiesel. The methanol production facility is a key element of GreenHunter's 105 million gallon per year biodiesel refinery, the largest in the U.S., slated for initial operations during the first quarter of 2008. PRNewswire - September 5, 2007.

    GreenHunter BioFuels, Inc., has begun commercial operations with the start-up of a 1,500 barrel per day methanol distillation system. Methanol is an alcohol used to transesterify vegetable oils into biodiesel. The methanol production facility is a key element of GreenHunter's 105 million gallon per year biodiesel refinery, the largest in the U.S., slated for initial operations during the first quarter of 2008. PRNewswire - September 5, 2007.

    Spanish renewables group Abengoa released its results for the first half of 2007 financial year in which its consolidated sales were €1,393.6 million, which is a 27.9 percent increase on the previous year. Earnings after tax were €54.9 million, an 18.6 percent increase on the previous year's figure of 46.3 million euro. Abengoa is active in the bioenergy, solar and environmental services sector. Abengoa - September 4, 2007.

    Canadian hydro power developer Run of River Power Inc. has reached an agreement to buy privately owned Western Biomass Power Corp. in a $2.2 million share swap deal that could help finance development of new green sources of electricity in British Columbia. The Canadian Press - September 4, 2007.

    As of Sept. 1, a biodiesel blending mandate has come into force in the Czech Republic, requiring diesel suppliers to mix 2 per cent biodiesel into the fuel. The same rule will be obligatory for gasoline starting next year. In 2009 the biofuel ratio will grow to 3.5 percent in gasoline and 4.5 percent in diesel oil. CBW - September 3, 2007.

    Budapest's first biofuel station opens on Monday near the Pesterzsébet (District XX) Tesco hypermarket. This is the third station selling the E85 fuel containing bioethanol in Hungary, as two other stations are encouraging eco-friendly driving in Bábolna and Győr. Caboodle - September 3, 2007.

    Canadian forest products company Tembec announced that it has completed the acquisition of the assets of Chapleau Cogeneration Limited located in Chapleau, Ontario. The transaction includes a biomass fired boiler and steam turbine with an installed capacity of 7.2 megawatts. Consideration for the assets consists of a series of future annual payments to 2022, with a present value of approximately $1 million. Tembec - September 1, 2007.

    Innovative internet and cable/satellite channel CurrentTV is producing a documentary on Brazil's biofuel revolution. Biopact collegues and friends Marcelo Coelho (EthanolBrasil Blog), Henrique Oliveira (Ethablog) and Marcelo Alioti (E-Machine) provided consulting on the technical, economic, environmental and social aspects of Brazil's energy transformation. ProCana - August 31, 2007.

    Oil major BP Plc and Associated British Foods Plc won competition clearance from the European Commission on to build a plant to make transport fuel from wheat in Hull, northeast England. U.S. chemical company DuPont is also involved. Reuters UK - August 31, 2007.

    The government of the Indian state of Orissa announced its policy for biofuel production which includes a slew of incentives as well as measures to promote the establishment of energy plantations. The state aims to bring 600,000 hectares of barren and fallow land under Jatropha and Karanj. At least 2 million hectares degraded land are available in the State. The new policy's other objectives are to provide a platform for investors and entrepreneurs, market linkages and quality control measures. Newindpress - August 29, 2007.

    Brazil's state-run oil company Petrobras said today it expects to reach large scale cellulosic ethanol production in 2015, with the first plant entering operations as early as 2011. Lignocellulosic biomass is the most abundant biological material on the planet, making up the bulk of the structure of wood and plants. In a first phase, Petrobras intends to use bagasse as a feedstock. Reuters / MacauHub- August 29, 2007.

    Seattle based Propel Biofuels, is announcing a $4.75 million first round of capital from @Ventures and Nth Power. The money will be used to help Propel set up and manage biodiesel fueling stations. BusinessWire - August 29, 2007.

    BioEnergy International, a science and technology company committed to developing biorefineries to produce fuels and specialty chemicals from renewable resources, announced today the closing of a major US$61.6 million investment that will provide funding for the Company’s three strategic initiatives: generating secure cash flow from its conventional ethanol platform, product diversification through the introduction of novel biocatalysts for the manufacture of green chemicals and biopolymers and the integration of its cellulose technology. BusinessWire - August 28, 2007.

    German company Verbio Vereinigte BioEnergie, the biggest biofuels producer in Europe, says it is considering plans to invest up to €100/US$136.5 million in a biofuel production facility in Bulgaria. The company wants the new facility to be located close to a port and Bulgaria's city of Varna on the Black Sea is one of the options under consideration. If Verbio goes through with the plan, it would produce both biodiesel and bioethanol, making Bulgaria a major source of biofuels in southeastern Europe. Verbi currently produces around 700,000 tonnes of biofuels per year. Sofia News Agency - August 27, 2007.

    Czech brown-coal-fired power plant Elektrárna Tisová (ETI), a unit of the energy producer ČEZ, could co-fire up to 40,000 tons of biomass this year, the biggest amount in the company’s history, said Martin Sobotka, ČEZ spokesman for West Bohemia. ETI burned more than 19,000 tons of biomass in the first half of 2007. The company’s plan reckoned with biomass consumption of up to 35,000 tons a year. Czech Business Weekly - August 27, 2007.

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Monday, August 20, 2007

Engineers develop compact biomass powered CHP plant based on Stirling engines

A consortium of European research organisations has achieved an engineering breakthrough by developing a compact, highly efficient combined heat-and-power (CHP) plant based on stirling engines and fueled by biomass. Until now there were no biomass CHP technologies available in the power range below 100 kWel. The engineers succeeded in optimizing and scaling down the technology to a power range of 35 kWel and a 70 kWel.

The small scale plants are hyper-efficient with an overall system efficiency ranging between 85 and 93%. Because the CHP units are so compact, they can replace existing but far less efficient traditional hot-water boilers. Alternatively they can operate in decentralised and autonomous energy systems in off-grid places, particularly in the developing world. Given that it is fueled by renewable and carbon-neutral solid biomass, the system is one of the cleanest energy concepts available.

The technology was developed within the scope of a research, development and demonstration cooperation project jointly carried out by the Technical University of Denmark, Bios Bioenergiesysteme, Mawera Holzfeuerungsanlagen and the Austrian Bioenergy Centre. Two pilot plants have been tested extensively with promising results: the smallest of the two pilot plants, the 35 kWel unit (image, click to enlarge), was tested for more than 10,000 hours, whereas the 70 kWel system has been operated for approximately 3,000 hours.

The following table shows relevant technical data and efficiencies of the CHP technology based on the 35 kWel- and the 70 kWel-Stirling engines:

The technology should become available on the market over the next few years.

The small-scale CHP unit works on the basis of an advanced furnace, equipped with underfeed stoker technology where the biofuel is burned. In the combustion chamber the flue gas reaches temperatures of approximately 1,300 °C. Heat is then transferred to the Stirling hot heat exchanger and the temperature of the flue gas is reduced to about 800 °C at a heat exchanger outlet. Subsequently, the flue gas passes through an air preheater and an economiser mounted downstream the hot heat exchanger (schematic, click to enlarge).

Integrating, scaling and optimising the system in such a way that it can be fueled by biomass, a fuel with particular properties, presented many challenges and required several innovations:
:: :: :: :: :: :: :: :: :: ::

An efficient engine
The core of the system is based on the Stirling engine. Such engines are based on a closed cycle, where the working gas is alternately compressed in a cold cylinder volume and expanded in a hot cylinder volume. The advantage of the Stirling engine in comparison to internal combustion engines is that the heat is not supplied to the cycle by combustion of the fuel inside the cylinder, but transferred from the outside through a heat exchanger in the same way as in a steam boiler. Consequently, the combustion system for a Stirling engine can be based on proven furnace technology, thus reducing combustion related problems.

The heat input from fuel combustion is transferred to the working gas through a hot heat exchanger at high temperatures. The heat that is not converted into work on the shaft is rejected to the cooling water in a cold heat exchanger.

The Stirling engine developed at the Technical University of Denmark uses Helium as working gas and is designed as a hermetically sealed unit. The use of Helium is very efficient in the context of the electric efficiency of the engine, but the researchers found that the utilisation of this low molecular weight gas made it difficult to design a piston rod seal, which keeps the working gas inside the cylinder and prevents the lubrication oil from entering the cylinder.

Many solutions have been tested, but it is still a delicate component in the engine. An attractive option was to bypass the problem by designing the engine as a hermetically sealed unit with the generator incorporated in the pressurised crankcase, just like the electric motor in a hermetically sealed compressor for refrigeration. This way, only static seals are necessary and the only connections from the inside to the outside of the hermetically sealed crankcase are the cable connections between the generator and the grid.

The challenges presented by the utilization of biomass fuels in connection with a Stirling engine were concentrated on transferring the heat from the combustion of the fuel into the working gas. The temperature must be high in order to obtain an acceptable specific power output and efficiency, and the heat exchanger must be designed so that problems with fouling are minimised.

Because of the high temperatures in the combustion chamber and the risk of fouling, it is not possible to utilise a Stirling engine designed for natural gas, as narrow passages in the Stirling heat exchanger are blocked after less than an hour of operation with biomass fuels. The risk of fouling in biomass combustion processes is mainly due to aerosol formation and condensation of ash vapours when the flue gas gets cooled. Bios Bioenergiesysteme GmbH developed a programme calculating the heat transfer from the flue gas to the internal working gas. Based on this development comprehensive design studies were performed and the performance of the Stirling heat exchanger was improved and optimised.

The image above (click to enlarge) shows an energy flow sheet of the CHP plant based on a 35 kWel Stirling engine. The electric plant efficiency amounts to approximately 12% and the overall plant efficiency to about 85 to 92%. The thermal heat output is normally in the range of around 230 kW and the fuel capacity (based on net calorific value) amounts to 300 kW.

Furthermore, the Bios Bioenergiesysteme developed and designed an automatic cleaning system for the Stirling heat exchanger which was subsequently optimised during plant operation. The system comprises a pressurised air tank and air nozzles at each heat exchanger panel. The nozzles are equipped with magnetic valves. The valves are opened at regular intervals (only one valve at a time, all other valves remain closed) and the air is blown into the heat exchanger sector and cleans the tubes from ash deposits. The ash is then entrained with the flue gas and subsequently collected in the fly-ash precipitators.

In order to obtain a high overall electric efficiency of the CHP plant, the temperature in the hot heat exchanger and consequently the temperature of the flue gas should be as high as possible. Therefore, it is necessary to preheat the combustion air with the flue gas leaving the hot heat exchanger by means of an air preheater. Typically the temperature of the combustion air is raised to 500 °C – 600 °C, resulting in very high temperatures in the combustion chamber. This can cause ash slagging and fouling problems in biomass combustion systems and in the hot heat exchanger.

Consequently, the design of the furnace and its adaptation to the special requirements of a CHP plant with a 35 kWel Stirling engine was an important and difficult task. The plant should operate at a high temperature level to gain a high electric efficiency from the Stirling engine but temperature peeks in the furnace should be impeded in order to reduce ash slagging and fouling. The plant is designed for temperature levels in the furnace of about 1,300 °C (the typical flue gas temperatures in conventional biomass furnaces are in the range of approx. 1,000 °C).

An appropriate combustion system was developed and optimised using CFD simulations which have been performed by Bios Bioenergiesysteme. The results achieved showed that it is a very important task to optimise the design of the furnace geometry, of the secondary air nozzles and the nozzles for flue gas recirculation in order to reduce temperature peaks in the furnace as well as CO emissions. In addition, the CFD simulations performed improved an equal distribution of the flue gas flow into the different sections of the hot gas heat exchanger and thus ensured an equal heat transfer to the cylinders of the Stirling engines.

Figure 2 (click to enlarge) shows the geometry of the furnace with conventional nozzle design and placement. The secondary air nozzles are placed at the inlet of the secondary combustion chamber. The results of the CFD simulations performed for this geometry show that the flue gas burn out in the secondary combustion chamber is not efficient (see Figure 4). The CO emissions at outlet according to CFD simulations are about 100 mg/Nm3 (dry flue gas, 13 vol% O2).

Figure 3 shows a furnace geometry with optimised nozzle design and placement. The secondary air nozzles are arranged horizontally in the transition zone between primary and secondary combustion chamber. With this configuration the combustion air is efficiently mixed with the flue gas and a swirl flow is established in the secondary combustion chamber. Consequently, the resulting CO emissions are low. Figure 5 shows the contours of CO in mg/Nm3 calculated for the geometry with optimised air nozzles. For the optimised geometry, CFD simulations predict CO emission of approx. 15 mg/Nm3 (dry flue gas, 13 vol% O2). The results demonstrate that an efficient turbulent flow enhances the combustion process and reduces CO emissions, which stresses the relevance of an optimisation of the combustion system supported by CFD analyses.

The image above (click to enlarge) shows the 35 kWel pilot plant. The furnace of the CHP plant is equipped with underfeed stoker technology. The Stirling engine is mounted in a horizontal position downstream of the secondary combustion chamber for convenient maintenance. The air pre-heater and the economiser are placed on top of the furnace in order to achieve a compact design of the plant. To remove fly ash particles from the hot gas heat exchanger, a pneumatic and fully automatic cleaning system was developed and installed.

Friedrich Biedermann, Henrik Carlsen, Martin Schöch, Ingwald Obernberger, "Operating experiences with a small-scale CHP pilot plant based on a 35kWel hermetic four cylinder stirling engine for biomass fuels" [*.pdf].


Jesper Noes said...

The information in this article is a few years old. The technology is now commercially available. The biomass boiler plants discussed in this text are sold through Mawera in Austria. The engines are produced by a newly created Danish company "Stirling Danmark Aps" who also offers turn key plants based on gasification of wood chips and the 35 kW engine. Please see Stirling.dk for more information.

Jesper Noes, Stirling Danmark Aps

11:00 PM  

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