Engine-based CHP

contributes to Germany’s power transition

A Bavarian utility has installed a cogeneration system based on gas-fuelled engines from GE Jenbacher to supply energy to its district heating scheme. The system is expected to contribute to Germany’s Energiewende programme, and similar schemes could be important to Europe’s energy security. Steve Hodgson looks over the data.

The J920 largest gas engine, the J920 FleXtra Credit: GE

The largest gas engine yet developed by GE Jenbacher, the 9.5 MW J920 FleXtra, has taken its place in the upgraded municipal cogeneration facility that feeds the district heating system in the city of Rosenheim, Germany.

The new engine generator sits beside four existing Jenbacher engines ” three 3.35 MW J620 engines and a 4.4 MW two-stage turbocharged J624 unit ” plus an existing waste incineration plant.

Stadtwerke Rosenheim’s integrated cogen facility now has an electricity generating capacity of 36 MW and a heat generation capacity of 44 MW. It meets about 40% of the electricity needs and 20% of the heating requirements of the city ” which has more than 61,000 inhabitants, and lies 450 metres above sea level in the upper-Bavarian Alpine foothills.

This impressive installation will help meet Germany’s goal to increase power from CHP from today’s 15% to 25% of the country’s power supply by 2020, as part of its larger energy transition (Energiewende) strategy. Germany is already the largest single market for CHP in Europe, accounting for more than 20% of the electricity from cogeneration across the EU-27, but it will need many more new CHP plants to meet the 25% target that was set last year in a new CHP law.

Speaking at the start-up of the expansion of the Stadtwerke Rosenheim plant, the Bavarian minister of state for Environment and Health, Dr. Marcel Huber, stressed the role of local government bodies: ‘The energy transition plan, Energiewende, can be achieved only if there is a cooperative effort, including contributions by municipal providers’.

‘Investments in innovative, modern power plants create an important foundation for the successful execution of our energy transition plan,’ he added

As part of Energiewende, Germany plans to close all nuclear power plants by 2022. To replace the massive amount of low-carbon baseload electricity from the nuclear power plants, the transition plan calls for increasing use of natural gas and renewable energy, and greater use of energy efficiency technologies. GE is also keen for Rosenheim to act as a demonstration of the role of distributed energy, to promote energy security across Europe.

Technology, both flexible, and efficient

The Rosenheim project’s centrepiece is GE’s largest and newest Jenbacher gas engine, the 9.5 MW J920 FleXtra, which GE calls a flexible power solution. It combines innovation with power and efficiency to help customers address their local energy security priorities, while achieving improved environmental performance.

GE expects to make the engine available in 60 Hz regions of the world in 2014.

The CHP system provides electricity and thermal power (hot water) for local residents and industrial customers. It has a lower-carbon footprint than conventional power plants and boilers, and will assist Germany’s effort to reduce greenhouse gas emissions by 40% by 2020. The engine’s fast start-up aids Stadtwerke Rosenheim’s operational flexibility, to overcome the challenges of intermittency caused by adding wind and solar energy supplies to the electricity grid.

The J920 FleXtra has the highest electrical efficiency in the 10 MW class of gas engines, of 48.7%, and about 90% efficiency in cogeneration mode, depending on heat utilization, says GE. Its two-stage turbocharging design will also help Stadtwerke Rosenheim to meet Germany’s goal to improve its energy productivity ” related to prime energy usage ” by 2.1% annually.

‘Our flexible J920 technology offers both high efficiency and reliability levels, which makes it the ideal large gas engine distributed power solution for industrial and grid stabilisation applications, while also minimising the customer’s carbon footprint,’ said Karl Wetzlmayer, general manager of Gas Engines for Power Generation, GE Power & Water.

GE applied more than 50 years of power generation experience to the development of its newest Jenbacher engine, and more than half a million engineering hours were devoted to its design, analysis, testing and verification.

The arrival of the new engine at Rosenheim was important for all involved: ‘GE and Stadtwerke Rosenheim have shared almost a decade of gas engine innovation and cooperation, making the utility an ideal associate to showcase the J920 FleXtra,’ Wetzlmayer added.

J920 FleXtra engine

Operating a J920 FleXtra at 48.7% electrical efficiency provides the capacity to produce more than 76 GWh of electricity per year, says GE. It also avoids the consumption of more than 6.4 million kWh of natural gas per year (at a gas price of €0.034 (US$0.044)per kWh.), and the emission of approximately 1500 tonnes of CO2 per year ” which is equivalent to the annual emissions of about 800 cars on European roads.

In cogeneration mode, the J920 FleXtra offers an overall efficiency of up to 90%, compared with the separate production of heat and electricity by a natural gas-fired boiler and delivery of electricity on the EU grid. Key performance data are shown in Table 1.

Two views of the J920 FleXtra gas engine installed at Stadtwerke Rosenheim Credit: GE

GE explains that the J920 FleXtra gas engine is designed for a variety of multiple-engine power plant solutions ” which range from remote on-site power supply to cogeneration or CHP.

In the latter case, use is made of jacket water heat and heat from oil and mixture coolers, combined with heat from the gas engine exhaust. The best total efficiency is achieved when the heating water circle has a return water temperature of 70à‚°C and a hot water temperature of 90à‚°C.

The J920 FleXtra’s two-stage turbocharging technology enables a total efficiency for providing power and heat up to 90% ” which, according to the company, is more than 3% better than that of a single-stage turbocharging gas engine. And since about 80% of the operating costs for gas-fired power plants go on fuel, this efficiency advantage represents a significant saving.

Germany is leading the way in Europe towards transforming its energy system ” not only in replacing nuclear power with renewables, but also in incorporating more inherently efficient generating technologies, and introducing more small-to-medium-scale distributed generation.

CHP is a key technology here ” it always has been ” but it is looking likely that Germany’s Energiewende will be effective in ramping- up the development of CHP in that country, and will demonstrate a way forward for others as well.

Steve Hodgson is COSPP’s contributing editor.

The gas engine prime mover for on-site generation

The two main types of prime mover used for cogeneration schemes are gas turbines and gas engines, although fuel cells have also entered the picture in recent years. However, one major difference between cogeneration and other energy plants, dictated by their production of heat as well as power, is that most cogeneration schemes are custom-designed, even at quite small plant sizes. So it is not easy to generalise about plant design ” they are all slightly different.

Nevertheless, generalising a little, gas turbines are highly suitable for larger-scale plants ” the type that serve industrial sites. They also provide more exhaust heat, which is useful where a large amount of industrial process heat is required. For smaller cogeneration plants, more often used to serve buildings, the reciprocating engine is the prime mover of choice. This is because of its greater flexibility in terms of starts-ups and cycling, and because it is more thermally efficient.

Gas, diesel and dual fuel reciprocating engines can all be used in cogeneration plant, but gas engines are usually preferred because they have considerably lower exhaust emissions and work well with CHP applications, utilizing the fuel highly efficiently. Gas engines also produce very little in the way of particulates.

Reciprocating engines are highly successful in small-to-medium-sized CHP installations, where the prime movers might typically be, say, 3-10 MW machines. More power is obtainable using several engines, and an array of engines also adds operational flexibility and valuable redundancy.

Reciprocating engines tend generally not to be designed expressly for cogeneration application, which requires lots of heat in the exhaust. Therefore, a chosen engine (gas, diesel or dual fuel), will be optimized for the application. This is comparatively easy to achieve by programming control parameters or through fuel/air system changes, so that a little thermal efficiency is sacrificed to obtain more exhaust heat.

The lean-burn gas reciprocating engine is ideal for making best use of natural gas. Such engines have been increasingly seen in Europe and elsewhere as being ideal for distributed power generation, which requires clean, reliable power for long ” sometimes intermittent ” periods of operation, at lowest cost. Other applications include standby power for critical loads and cogeneration systems.

GE takes gas engine CHP to Nigerian drug facility

In the past few weeks, GE has announced two more CHP plants based on a series of gas engines ” to serve a rather different application: a pharmaceutical factory in Nigeria.

The company is to supply three of its 4 MW Jenbacher J624 gas engines and one of its 2 MW J612 units to power a new factory that will produce billions of syringes and intravenous drug products needed each year to fight malaria across the African continent.

Clarke Energy, GE’s distributor of Jenbacher gas engines in Nigeria, will install the 14 MW cogeneration plant at the factory on behalf of Nigeria-based Integrated Medical Industries Ltd (IMIL), and it is due to go into production in 2014.

Reliable power supplies are essential for smooth operation of the factory, since power interruptions can damage batches of syringes. Demand for electricity in Nigeria is high, and the national grid has a challenge ahead in trying to meeting this demand. The on-site cogeneration facility, however, will rely on the country’s own growing gas distribution network to ensure it has a reliable fuel supply.

IMIL also selected the Jenbacher gas engines to take advantage of natural gas prices, which are lower than those of diesel fuel, and the additional capital expenditure is expected to be paid off in 12 to 18 months, according to GE. The power plant will be installed within the manufacturing facility, and will operate in island mode, to provide reliable on-site electrical power and heat.

The Jenbacher J624 units will offer an electrical efficiency of 43.1%. In addition, the engines’ exhaust will be passed into a steam generator to produce steam in a boiler.

The J624 Jenbacher engine ” three such engines will help to power a pharmaceuticals factory in Nigeria

GE is scheduled to deliver the J624 and J612 units in the third quarter of this year. Clarke Energy is serving as the single point of contact from initial sale, project management, engineering, installation through to commissioning, and long-term maintenance of the power plant.

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