What are the main advantages of a combined production of heat and power? What kind of role may cogeneration play in a continuous change of the energy industry?

Solar or wind energy are getting cheaper and cheaper and there is no doubt that their share in the energy mix will be continuously growing. The increase of their variable production will bring longer intervals during which these sources will cover total electricity consumption, however, in the meantime, there will be longer or shorter intervals during which their production will not be sufficient.

Compensation sources will have to be able to start quickly, regulate the output flexibly and also stop completely, even several times during a day. For this purpose, standard gas piston engines are wee suited, they can burn different types of fuel – biogas, biomethane, natural gas, LPG and synthetic methane in the future, too. Engines of the sizes from just a few kilowatts to 10-12 megawatts and an electrical efficiency close to 50%, in the case of the bigger ones, are available nowadays.

However, it is necessary to use the fuel as efficiently as possible, which means to use the waste heat for production of useful heat. Within our geographical conditions, when the annual heat consumption is approximately twice as high as the electricity consumption and the maximum consumption values are coincident both in the winter season, the cogeneration, i.e. the combined production of heat and power (CHP), a traditional way of heat and power supply, is also a very convenient way for securing both power and heat in the future.

We should not forget about biomass cogeneration either, but that is a slightly different topic.

Where is the space for development and construction of new CHP units in the Czech Republic? How could the further development of cogeneration be supported in the Czech Republic instead of industrial and municipal heating plants for example?

CHP is divided into several categories according to the size of the electrical output: microcogeneration (up to 50 kW), small cogeneration (up to 1MW), medium cogeneration (up to 5 MW) and large cogeneration (more than 5 MW). In the last years, thanks to a continuous support, the sector of small and medium gas cogeneration has been developing, those CHP units are typically installed in district heating in smaller towns or companies. Currently, there is around 300 MW in operation and the number is increased by 30 MW annually. A CHP unit, which replaces natural gas boilers in boiler rooms within a local heating plant can save 20 to 40 % of primary fuel and 20 to 60 % of carbon dioxide emissions compared to a separate production of power and heat (higher values for extrusion of coal-fired condense power production, lower values compared to steam-gas cycle power production).

However, there will also be opportunities for gas cogeneration based on gas engines within big district heatings, where an optimization, respectively a decentralization of those system structures will be happening. ČEPS, in their assessment of production adequacy until 2030, assumes that around 150 MW of gas cogenerations of 5 to 10 MW size in small heating plants using for the time being black and brown coal will be created, which shall, under the pressure of stricter and stricter emission limits, be switching one by one to natural gas, alternatively, according to local conditions, to biomass or other fuels.

The field of individual heating is another topic. According to ČHMÚ, an individual heating based on solid fuels produces half of particulate matter emissions (PM 2.5) and 97 % of carcinogenic benzopyrene. The microcogeneration in the size of units of kilowatts has to so far deal with a low efficiency and high investment costs. However, the microcogeneration can be one of the solutions of this situation in the coming years.

We estimate that there could be up to 1000 MW total of cogenerations based on gas engines in operation by 2030. In spite of the fact that those are small sources from the perspective of the large-scale power industry, those locally placed sources will be an advantage in the energy system which is to be more and more decentralized. Moreover, by connecting more CHP units into one virtual, centrally managed source, they could be also used for management of the transmission system.

What tools can be used to support installation of new CHP units?

The current prices of electricity would not pay for any investments into economic and ecological technologies. Therefore, CHP needs some subsidy, too. In the Czech Republic similarly to for example Germany, CHP-based power generation is subsidized in the form of an operational subsidy, by a so called annual green bonus.  A methodology for the bonus calculation and optional operating modes (max. 3000 or 4400 h annually) are a good motivation to operate cogeneration in peak power prices and by this means, the cogeneration contributes to the mains stabilization. CHP units are very often equipped with a heat accumulator so that they can better respond to different demands for power and heat supply.

The Ministry of Industry are currently preparing an amending act regarding subsidized sources which brings two key novelties. In accordance with the European legislation requirements, an operational subsidy of CHP-based power generation above 1 MW will be tendered in auctions and it will be possible to ask for a subsidy for modernized sources, too.

So we hope that the lawmakers and public servants are able to approve the law and subsequent regulations in such a form and timeframe that the construction and operation of CHP units can continue without any interruption and the unfortunate situation from the past years, when the Energy Regulatory Office stopped paying the subsidies due to the act on subsidized sources not having been approved, and for a long time it was not clear how this all would end up, does not recur.

Is the gas cogeneration competing in the market with the traditional heating plants? Could a CHP unit be an option in the case when the district heating is gradually transformed, for example because of a decline of coal-fired heating plants?

Combined heat and power production are basically a part of all district heating systems. However, in many locations, it will be necessary to restructure or decentralize the district heating substantially and gradually start using more ecological fuels rather than coal, in order to maintain the district heating. It would be a mistake to let an uncontrollable disintegration of heating networks happen since they will not be used one-way only for the heat transport from a heating plant to a user but more and more for an integration of all sources of renewable and waste heat available within a specific area: heat from solar systems, industry waste heat, waste heat from air conditioning units, heat from big heat pumps using heat from the earth, water or perhaps sewage network.

The district heating, by using accumulation abilities of heating network and high-capacity accumulators, can react to a current electricity market situation in a flexible way and substantially contribute to the stability of the electrification grid. Moreover, it enables multi-source solutions (combustion of waste, biomass, natural gas, big heating pumps, etc.) rather than individual ones, which permits reacting to current availability and prices of fuels.

The district heating is unique in a way of interconnecting electrification, heating and in the case of natural gas combustion also gas systems into one integrated complex and considering the development of the energy sector, the district heating will become one of the key parts of the energy system. In particular from the perspective of an effective use of primary energy sources, flexibility and stabilization of electrification system and a very important role will be to ensure energy security of particularly cities and agglomerations, for example in the case of a huge blackout.

There has been an interesting development of the cogeneration in Germany where gas engines are used more and more instead of steam-gas cycles which were common in the past. The heating plant in Kiel is currently under construction, where there will be twenty gas engines of 10 MW output installed, and similar sources are being built also in other cities (Dresden, Stuttgart) which already have big heat accumulators and electric boilers as a standard.

What are the advantages of gas engines compared to standard steam-gas cycles?

The Gas engines have two key parameters which are substantially better. They can go very quickly from zero to 100 % within two to five minutes compared to tens of minutes in the steam-gas case. Another advantage is a wide scope of regulation practically ranging from zero to 100 % and in case of gradual switching off a number of engines connected in parallel, also an ability to keep a high efficiency within the full range. Steam-gas can usually work within the range of 30 to 100 %. These are the characteristics which make cogeneration with gas engines a suitable solution of a flexible backup to renewable energy sources.

Is there anything else in Germany that the domestic energy sector can get inspired by?

There is almost one fifth of electricity generated by cogeneration in Germany, while we are at 12 to 13 %. So, under similar conditions, there is for sure a potential for development of CHP here.

Also, the fuel structure in CHP-based power generation in Germany is worth mentioning: 55 % of electricity is from natural gas, 30 % from biomass or biogas, 15 % from coal. Here it is over 50 % from coal, 30 % from biomass or biogas and 20 % from natural gas. It is to be expected that coal and gas will gradually switch their positions here, too.

In your view, the future lies in the natural gas cogeneration. What do you think of fears about dependence on import of this fuel? Are there any alternatives to Russian natural gas?

The safety of energy supplies is a very important aspect of discussions about the Czech energy policy. It would not be wise to depend on one type of energy only, that is why we speak about a balanced energy mix. There is a big discussion about the Nordstream 2 pipeline, however, there are also 23 LNG terminals and further 19 under preparation in Europe. The global LNG market keeps growing and is more and more diversified, projects focused on liquefaction of gas are also being prepared in Russia. So, I cannot imagine that any “closing of tap” would happen. However, we should realize that only 5 % of electricity is generated from natural gas here. A fear about dependence on this fuel from the perspective of power generation is therefore not justified.

One of the options how to keep surplus of electricity from renewable sources is hydrogen or synthetic methane generation. Synthetic methane generation is too expensive so far, but a mixing of hydrogen (up to ca 10 %) into the gas network is being realistically considered. Thus, the standard natural gas will be gradually turning “green” and the gas infrastructure as well as the technologies for power and heat generation from gas will continue to be useful.

Combined production of heat and power can be also carried out by biogas plants or by combustion of solid biomass. However, the development of these types of renewable sources has stopped in the Czech Republic in the last few years. What would contribute to strengthening the interest in new installations?

For the biogas plant cogeneration, the heat consumption, which is always lower than its production, in particular in the summer months, is a limit. Some operators offer heat to residents of surrounding municipalities, other ones build different drying rooms where they try to make a use of the heat. Methane production and its pushing into the gas pipeline network is a technical solution of this problem. It can be then used for heat production in a more convenient place. The size is the limit for the combustion of the solid biomass. The power production does not pay in the case of a relatively small heat consumption (up to 100 thousand GJ a year), it is much cheaper to just burn the biomass and generate heat only. Personally, I do not like that but the rules are set by the economy.

How are the Czech CHP units doing within the world’s competition? How do they manage to beat competitors’ products?

They are doing well. There is TEDOM a.s. based in the Czech Republic which have been producing and delivering CHP units based on gas engines for 27 years and have delivered more than 4 thousand CHP units to different markets all over the world during that time. TEDOM acquired a German company called SCHNELL in 2016, one of the most important suppliers of biogas CHP units and TEDOM together with SCHNELL currently belong to the biggest and the most renowned suppliers of the CHP units.

The current CHP units are based on the use of piston engines. However, the further development can be also focused on the use of fuel cells, ORC systems or Stirling engine. Which of these technologies is in your view the most promising one?

The most widespread technology for decentralized combined production of heat and power with outputs of up to 10 to 20 MW are still the piston combustion engines. Their biggest advantage is the fact that they are developed for a use within the automotive industry and thus are produced in large volumes. Therefore, they are relatively cheap and technically reliable and their both spare parts and maintenance are available. Moreover, their efficiency is high. The piston combustion engines, despite being despised by many people, are still playing and, in my point of view, will be playing an important role in the decentralized power and heat generation from gas just from the above-mentioned reasons. We have developed also other types of engines at TEDOM, for example the Stirling engine. In fact, it has finished due to the project economy. We have not been able to fully dissolve the development costs in the engine price because it would become unsaleable.

TEDOM, a Czech company, carried out a project of connecting CHP unit with energy from rooftop photovoltaics and batteries last year which works in an island mode within a part of the company’s premises. Could a similar project become a trend in the industrial energy sector in the future?

TEDOM have been running an integrated energy system within their premises since 2016 which provides the premises with the supply of electricity, heat and cooling. The primary power production in the combined power source is done in a renewable source – photovoltaics. The differences between the production diagram from a renewable source and the power consumption diagram are covered by accumulation of power in batteries on daily basis. A long-term shortage of power production in a renewable source is covered by CHP unit production. The operation of the CHP unit is used in particular in the winter, that is in the season when there is a low production from the photovoltaic source and a sufficient demand for heat for an effective operation of cogeneration at the same time. An appropriate sizing of resources and accumulation of power and heat creates an ideal solution for providing a high level of usability of a renewable source without overflows of the energy into the distribution system, an effective use of primary energy of gas fuel and a minimization of demands for consumption from the distribution system. After a few months of testing and tuning of parameters, we operate the system in an island mode.

The island mode is in particular suitable in such locations where the achievable power input from the distribution systems is not sufficient or the connection is problematic. Return on investment of the island system operation without any operational support for cogeneration-based power production is over 10 years under the current conditions and it could be even less in the future, but I do not think this should be a common trend.

However, this project helps us to show that it can work. The “small” technologies have been developing quickly and will enable higher and higher level of independence on the electricity mains. Even the small sources can contribute to the stabilization of system by connection to the network. That is why the state authorities should not be pushing those prosumers out of the system, for example by unnecessarily strict requirements for restriction of overflows into the mains or by a wrong set-up of a tariff system.

What kind of novelties in cogeneration could bring a change of energy sector into a more flexible system, which the EU’s package of energy measures in the form of different virtual solutions and aggregators is aiming for?

The gas cogenerations have not had the opportunities to show all their abilities so far. That is why I welcome the regulation on electricity market which will gradually unify all the rules in the individual member countries and remove the barriers which for the time being prevent the small and virtual sources in the Czech Republic from offering support services. I would like to use this interview as an opportunity to invite the readers for the 11th year of the Cogeneration Days 2018 conference which is held on the 23rd to 24th October 2018 in Čestlice. There will be presentations about overall development of the Czech and European energy sectors particularly with regard to approving of individual parts of the winter package as well as about specific topics related to cogeneration – an amending act regarding subsidized energy sources, subsidy auctions, modernization. During the panel discussion, we will then speak about the topic I have mentioned before, that is when and under which conditions the small and virtual sources will be allowed to provide support services.

Josef Jeleček, chairman of COGEN Czech, a.s. association

He graduated from the Faculty of Mechanical Engineering at the Brno University of Technology (VUT), the Department of Thermal and Nuclear Machines, in 1984. He started his career as a development specialist focused on design of combustion turbines, later on worked as a secondary circuit operator at the Dukovany Nuclear Power Station. In 1991, he founded TEDOM where he acts as the CEO and the Chairman of the Board. Since 2002, he is the Chairman of COGEN Czech, the association for combined production of heat and power.

COGEN Czech is the association of legal entities and natural persons whose activities are related to the production and operation of cogeneration technologies, their design, sale and consultancy in the area of combined production of heat and power. The aim of the association is a support of combined production of heat and power, creation of more favourable legal and economic conditions for its development, representation and promoting of interests of producers and users of cogeneration technologies and dissemination of information about economic and ecological benefits of cogeneration.