Cogeneration could be the answer to our energy woes

For engineers, improving the efficiency of their processes is a major challenge, but also an opportunity to improve their outcomes while consuming the same or a lower amount of resources.

With the current focus on climate change and the high cost of electricity in Australia, maximising the efficiency of energy generation is a major opportunity, and for Dr Jacob Klimstra, Senior Energy and Engine Specialist for Jacob Klimstra Consultancy, a no-brainer.

Dr Klimstra was in Sydney to speak at the 2012 Australian Institute of Energy National Conference, and present a Cogeneration and Trigeneration Professional Development Course organised by the Chemical and Biomolecular Engineering Foundation of the University of Sydney.

Hailing from the Netherlands, Dr Klimstra has long been a proponent of cogeneration systems, which are typically engines that generate electricity, as well as heat and other by-products which may be captured and utilised, maximising the output from the fuel.

In traditional fossil-fuelled power generation, the efficiency is typically 35 to 37 percent, with about two-thirds of the primary energy converted to produce electricity being lost as heat. Transmission losses are responsible for nine percent of the losses from net generation.

Cogeneration systems, according to Dr Klimstra, aim to make use of the heat created as a by-product of burning fuels for electrical generation.

This energy is harvested and utilised in processes, such that it is no longer wasted. With plants in more remote areas, cogeneration systems can either be used as the primary source of electrical and heat energy, or as a backup in case the grid fails.

Useful by-products

Regions with a local distributed network of cogeneration plants, would also benefit from reduced reduce transmission losses, and boosted reliability.

Dr Klimstra utilises the exergy model to explain the relative value of different forms of energy, and why, even with processes that only require one form of energy, it is always a good idea to have cogeneration in place.

"You can always turn almost 100 percent of electricity into motive power for driving electric motors, for creating light, running electronics, and if you want to turn it into heat, you can have very high temperatures," he explained.

"With electrical heating, you can create temperatures of maybe 3000 degrees Celsius even. You can't do that with a gas burner. The exegetic value of electricity is very high, which is why the price of electricity is also higher than that of heat.

"Given the high exergetic and monetary value of electricity, it makes financial sense to create electricity, even if the application only calls for heat.

"If you just burn the gas, you create heat. If you use the gas in a cogeneration plant, you get the high value energy, which is electricity, and a low value energy, which is the heat, available as a by-product," Dr Klimstra said.

Of course, the reverse is also true: where only electricity is needed, harvesting the heat and using it in processes helps boost overall efficiency.

Ambient temperatures

Heat has a variety of applications in industry, be it for drying foods or curing of materials. Where higher temperatures are needed, the relatively low level of heat from cogeneration plants can still be fed into the process to raise ambient temperatures, reducing the amount of electricity needed to achieve the target temperature, and achieving close to 100 percent utilisation of the energy locked in the fuel. 

Heat can also be fed into absorption chillers to provide cooling, if that is what is required. "This is a lot better than having a big coal-fired power plant and throwing all the heat away and running at an efficiency of 35 percent. That's a waste of energy," said Dr Klimstra.

Dr Jacob Klimstra is Senior Energy and Engine Specialist, Jacob Klimstra Consultancy, The Netherlands.Dr Klimstra (pictured on the left) also pointed out that cogeneration systems are flexible, and other by-products of the generation process, not just forms of energy, can be used as desired.

Carbon dioxide from the engine, for example, can be harvested and used to boost plant growth in agricultural applications.

"The principle behind this is that everywhere where you need heat, be it for a chiller or for somewhere else, you should try to put a cogeneration plant," he concluded. "Even if you don't need electricity, just put the electricity in the grid."

According to Dr Klimstra, the prime movers for cogeneration are things like reciprocating engines and combined cycle turbines.

Combined cycle turbines are an assembly of heat engines which work off a single source of heat to reduce energy loss. In additional to a gas turbine and boiler, heat is turned into steam, and used to drive a steam turbine.

Gas-fired reciprocating engines can utilise exhaust heat, turning it into steam in order to produce electricity through a steam turbine.

When Dr Klimstra and his team started working on cogeneration, they used small gas engines from a Fiat. Rated at 15 kW, they had an electrical efficiency of 25 percent.

Improvements in engine technology have seen efficiencies for single cycle engines boosted to 49 percent, and turbochargers further improve performance.

"Relatively, the engines have become cheaper," Dr Klimstra told PACE. "For the last decade, the prices of these installations have not gone up. You don't even have to correct for inflation. The price level has stayed about constant because of improved production processes and higher output from the same engine block."

But while the equipment can be as simple and as complicated as the application demands, the specific expertise needed for the installation, commissioning and upkeep of cogeneration systems is something Australia lacks – and something Dr Klimstra hoped to address with the Cogeneration and Trigeneration Professional Development Course.

According to him, dedicated knowhow is needed from the installation stages: cogeneration plants, while being based on engines, are still fairly high-tech. With design, an energy engineering background is needed. Maintenance and operation requires the relevant mechanical qualifications, which already exist in Australia.

"With cogeneration, you have to know about lubrication, electrical system, safety systems, maintenance, and material properties," he explained. "It's a multi-disciplinary object, and you have to train people. So you need a group of dedicated people who know what they're talking about."

"If you want to install it into a process plant for instance, then you have to look at the ins and outs, like what is the heat demand, the temperature level of the heat, what is your electricity mark, do they coincide, do you need a heat buffer for temporarily storing the heat produced, because heat and electricity coincide¬these things have to be analysed."

Sydney Water's Malabar Cogen Plant turns waste methane gas into electricity to help power wastewater treatment plants. [Image courtesy of Sydney Water.]

Sydney Water's Malabar Cogen Plant turns waste methane gas into electricity to help power wastewater treatment plants. [Image courtesy of Sydney Water.]

In the 1980s, as the Netherlands was starting to embrace cogeneration, Dr Klimstra and his team organised a small group of well-trained engineers who went to industries and explained the technology, and also helped with tuning of installations.

This ultimately resulted in a mass take-up of cogeneration. Today, in the Netherlands, 35 percent of all electricity is produced with co-generation. In Denmark, this figure is over 40 percent.

According to Dr Klimstra, given the entire point of cogeneration is in efficiency and optimisation, the commissioning stage is the most important part of implementation, thus requiring the most specialist expertise.
"For commissioning, you need a multi-disciplinary engineer who knows about electricity, heat and emissions," Dr Klimstra said.

He suggested having small groups of experts who can commission installations, utilising the right equipment for measuring emissions, stability of the installation, performance, and efficiency, in order to yield optimum performance from the investment.

Future technologies

Dr Klimstra has high hopes about the future role of cogeneration in an ever-evolving energy landscape. However, he is not so optimistic about the application of newer technologies.

While there is a lot of potential for fuel cells to be implemented in cogeneration plants, Dr Klimstra says they are too sensitive to environmental variables to be of very much use in cogeneration plants, which are often used in harsh environments.

As part of a supervisory committee of a research institute in the Netherlands, Dr Klimstra has been privy to research into fuel cells over the past 25 years, having seen test results for the use of various types, including phosphoric acid fuel cells, molten carbonate fuel cells, and solid oxide fuel cells.

"Fuel cells are too complicated," Dr Klimstra said. "They are sensitive to minor components in the gas like sulphur. When a truck passes with a little bit of sulphur in the diesel and it comes out of the exhaust, and the air is fed into fuel cell, the fuel cell deteriorates."

However, the hardy nature of some cogeneration installations means many other technologies and fuel sources are compatible with such systems.

Application flexibility

Systems integrating a dual-fuel reciprocating engine, for example, can run on natural gas, bio-gas, diesel and bio-diesel, providing application flexibility.

For developing countries, for example, with areas which do not have access to power lines, such cogeneration systems provide a way forward. They can initially run off diesel in order to provide electricity and heating.

As the economy grows and infrastructure is introduced, the system can then be converted to use gas, allowing it to run cheaper and cleaner.

With the simple nature of engines making cogeneration systems effectively fuel-agnostic, cogeneration systems can exploit newer generations of energy sources, such as bio-gases, and fuels converted from waste.

The Netherlands, for example, is running a project to collect municipal waste, and convert it into synthetic gas. The gas can then be made into a liquid fuel and used to run engines in cogeneration plants.

"Some of the heat will be used for treating the waste, but you also produce electricity for the grid," explained Dr Klimstra. "So the amount of waste is substantially reduced, and you make sustainable energy from it."

Photovoltaic systems

Cogeneration systems also have a role to play with other renewable energy sources. According to Dr Klimstra, a distributed network of cogeneration plants could be a solution to current limitations of photovoltaic systems, namely, that they do not generate electricity at night.

"With cogeneration systems locally, you have an excellent way to provide backup power," he said. "The systems are fast, and require relatively low investment. It can run on biogases, so if you have sewage treatment systems, you can use the biogases from there to run the cogeneration system."

"The future will be a kind of integrated system, solar PV, wind power, available hydropower, geothermal power, and at the same time, cogeneration power as backup for these renewables."

Cogeneration could also contribute to the current trends towards decentralised energy generation, which Dr Klimstra says would contribute to supply reliability.

For example, an industrial park could have a cogeneration installation in every facility, each of which feeds excess electricity into the grid.

Such a configuration means every factory has its own backup power even if the main grid fails, with the added advantage of having a stable source of power from the network of other plants if its local unit fails.

Government role

Dr Klimstra hopes the government will help in laying down the regulatory foundations which will encourage the use of cogeneration plants. "Compared to what you have in Europe, Australia has just a minimal amount of these cogeneration installations," he said.

"The government should acknowledge that cogeneration is one of the best ways of saving energy. If you want to reduce your ecological footprint to comply with the rules of the rest of the world, then cogeneration is the best solution."

Having a robust feed-in tariff scheme, for example, would encourage plants to install their own cogeneration plant for faster return on investment.

Other possible moves would include the establishment of standards around the safety, emissions and performance of cogeneration plants, and establishing training and certification programs for professionals specialising in these systems.

For Dr Klimstra, the case for cogeneration is a simple one: continue throwing energy away in the form of inefficiency, or make full use of every drop of fuel. That, he says, is one of the biggest opportunities for Australia's industries today.

[Dr Jacob Klimstra is Senior Energy and Engine Specialist, Jacob Klimstra Consultancy, The Netherlands.]

[More information: The University of Sydney]

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