Gruppo AB

COGENERATION HELP DESK

Cogeneration is an "enlightened" business choice that looks at the future with a strategic approach between efficiency and sustainability.

Send your questions to AB

That is why we have decided to open the "Cogeneration Help Desk" to answer your plant management and technical-application questions. Do you want to know about the evolution of cogeneration technology? Do you want to find out which system might be ideal for your needs? Do you want to assess case histories in your sector? Write to us at our e-mail address. We will reply as soon as possible and the most interesting questions will be published on this page.

FREQUENTLY ASKED QUESTIONS [click on the question to read the answer]

• What is the actual saving I can get from cogeneration in industrial applications?

• What are the authorisation requirements for a natural gas cogeneration plant?

• What incentives are there for a fossil fuel (natural gas) cogeneration plant?

• Does a cogeneration plant require regular servicing?

• What is an anaerobic fermentation system for the production of electrical and thermal energy essentially composed of?

• What incentives are there for biomass plants?

• What agricultural biomasses guarantee the best performance of an anaerobic digestion plant? How much surface area do I need to dedicate to biomass cultivation in order to feed a 1 MW cogeneration plant?

• I am an energy manager of a company with two production units, one in the north and one in the south of Italy. If I install a cogeneration plant at the first production unit with an electrical energy production exceeding my specific requirements, can I use this excess to meet the requirements of the other production unit?

• Is all natural gas intended for cogeneration tax-exempt? Is it necessary to install a dedicated meter?

• My company's production process requires the use of cold water at 6-7°. For other stages a cooling temperature with values close to 0° are required. Is it possible to achieve these temperatures with trigeneration?

• My company has a dynamic painting tunnel that operates at 140°C and the air is continuously heated by means of steam and then expelled without thermal recovery. How could I use the water of a cogeneration plant?

• My company works 2 shifts and uses a lot of throwaway steam. Can I think about a turbine system?

What is the actual saving I can get from cogeneration in industrial applications?
A maximum percentage value may be quantified at around 30% and the pay-back on your investment may be hypothesized in 2 to 4 years. These performance values depend on three variable principles: the size of the plant, the actual thermal recovery and the annual hours of operation. Choosing your technological partner is hence determining for the success of the project. A feasibility study, product excellence and an efficient maintenance service are the basic ingredients of energy efficiency and hence saving.
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What are the authorisation requirements for a natural gas cogeneration plant?
- PROVINCE: You require single authorisation for plant construction and operation; this may take approximately 6-8 months from application.
– POWER GRID You can stipulate an agreement with ENEL to connect your electrical energy production plant to the power grid; this may take approximately 2-3 months.
- VVFF (fire brigade): the plant project needs to be approved and the fire prevention certificates (CPI) issued by the fire brigade.
– UTF (Technical finance office): you need to apply for a license to produce and sell electricity; this must be done during machine installation and before plant testing..
- DIA (Declaration of activity start): you need to obtain building permissions and licenses.
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What incentives are there for a fossil fuel (natural gas) cogeneration plant?
Energy Efficiency Certificates (EEC), also known as "White Certificates", are an incentive to install efficient technologies and systems. A certificate corresponds to saving an equivalent ton of petroleum. They consist of bonds that can be bought and subsequently sold and their value is in relation to the market trend. They are issued by GME (electricity market operator) following verification of the energy saving achieved, for example, by installing a cogeneration module with an endothermic engine instead of the conventional electrical energy (Italian electrical park) and thermal energy production systems. The white certificates are issued for three types of saving: 1. Electrical energy; 2. Natural gas; 3. Other fuels.
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Does a cogeneration plant require regular servicing?
The service issue is very imporant in the choice of a cogeneration plant. We can give you a concrete example of a plant installed at a company that works 3 shifts on weekdays only for 11 months a year. Imagine how many kilometres a vehicle would do if it had to drive continuously at 60 km/h, 5 days a week for 48 weeks: it would be to the tune of 345,600 km/year. From this you can understand that maintenance is determining in the choice of a supplier, especially considering that every machine stop means lost profit. At the current energy costs and given a plant that produces 1000 kW, you can hypothesize an average saving of almost € 1500/day – this gives you an idea of what the cost of a machine stop means in terms of lost profit!
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What is an anaerobic fermentation system for the production of electrical and thermal energy essentially composed of?
This system is made up of two main parts: one for fermentation and production of biogas consisting of one or more fermenters, and the other for transformation of the biogas into energy: the cogeneration system. Biogas is a mixture of gases composed mainly of natural gas, carbon dioxide and other minor components obtained through anaerobic fermentation of the biomass introduced in the digesters. The biogas is then appropriately treated in order to make it suitable to feed the endothermic engine of the cogeneration plant. The cogeneration phase produces electrical and thermal energy, the former intended to be sold to the power grid at the established rate, and the latter is mainly used to maintain the digesters where fermentation occurs at a suitable temperature and/or to condition buildings or stables through appropriate remote heating systems.
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What incentives are there for biomass plants?
Anaerobic digestion plants fed with vegetable biomass enjoy incentives through the sale of the electrical energy they produce essentially with two alternative methods: - all-inclusive rate: compensation for the electrical energy produced by the plant at an all-inclusive rate of € 0.28/kWh produced and sold to the national power grid according to the bill of law "Development" 1141 (approved on 1 July 2009) – by means of green certificates: adding to the benefit of the electrical energy produced and sold at normal market prices, you get the benefit deriving from the sale on the market of the green certificates obtained. For plants with an electric power below 1 MW, the choice between the two methods is at the discretion of the self-producer, while above 1 MW, the only rate permitted is that of the sale of electrical energy on the market plus the green certificates. The eco-incentives allow amortizing a bio-cogeneration plant in a particularly short time to then start earning significant profits from a really effective investment both business-wise and for safeguarding the environment.
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What agricultural biomasses guarantee the best performance of an anaerobic digestion plant? How much surface area do I need to dedicate to biomass cultivation in order to feed a 1 MW cogeneration plant?
It is important to mention that biogas can be produced from co-digestion of zootechnic waste (pigs, cattle, poultry, etc.) with energy cultures (maize, sorghum, etc.) and/or organic waste. Using organic substances for biogas production also allows fair use of waste products and by-products. Silage maize and sorghum are the energy cultures that guarantee the best yield in terms of biogas. Should these cultures be processed according to the classic monoculture cultivation method, you would need about 300 hectares to feed a 1 MW plant. If you do not have that much cultivatable soil available, you might consider, if possible, two cultures, for example silage maize and triticale. If in addition to special cultures you have different organic substances, dairy industry by-products, vegetable processing waste, etc. available, you need to outline a scenario that takes into account the properties of each single product available, its storage and the period of availability of the various products.
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I am an energy manager of a company with two production units, one in the north and one in the south of Italy. If I install a cogeneration plant at the first production unit with an electrical energy production exceeding my specific requirements, can I use this excess to meet the requirements of the other production unit?
Considering the difficulty of managing the "excess" electrical energy of the site where the cogeneration plant would be installed and given the fact that the energy vectored to the other production unit would involve various expenses, such as the transport, dispatch and metering, as well as the system costs, and that drawing electrical energy must necessarily coincide with injection into the power grid, it would be more cost-effective to make an agreement with a trader or sell it to the GSE (Energy Service Operator) who is obliged to collect the excess energy from "virtuous" CHPs (Combined Heat and Power) at defined rates.
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Is all natural gas intended for cogeneration tax-exempt? Is it necessary to install a dedicated meter?
No, not all natural gas is tax-exempt. In order to assess the quantity of gas not subject to tax, the UTF (Technical Finance Office) reads the electrical energy meter positioned at the terminals of the alternator, calculating the consumption of 0.25 m3/kWh. Essentially, the efficiency of the system is rewarded.
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My company's production process requires the use of cold water at 6-7°. For other stages a cooling temperature with values close to 0° are required. Is it possible to achieve these temperatures with trigeneration?
For the 7° thermal stage, it is possible by using a lithium bromide absorber; in the second case, an ammonia absorber might be hypothesized, however, this should be analysed in detail considering the complexity and the application costs. Other types of absorbers that can reach intermediate temperatures between 7° and 0°C are appearing on the market, these technologies should however be more closely examined.
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My company has a dynamic painting tunnel that operates at 140°C and the air is continuously heated by means of steam and then expelled without thermal recovery. How could I use the water of a cogeneration plant?
As it is always renewal air taken in from the outside without thermal recovery, you could think about simply pre-heating the air from room temperature to the maximum degree reachable in proportion to the quantity of air using an air/water heating element. The steam the plant produces through the exhaust flue gas would integrate/replace that produced by current boilers.
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My company works 2 shifts and uses a lot of throwaway steam. Can I think about a turbine system?
Even if a gas turbine produces a considerable amount of steam, I don't think it suitable in your case, as working two shifts (+- 15 h/day) is unsuited to a cogeneration plant with turbogas. A turbine is suitable for a continuous working cycle, and starting and stopping it is not good and would moreover considerably shorten the maintenance intervals. In your situation, having to turn off the system every day, I think a system with endothermic engine would be more suitable, which is less sensitive to being turned on and off. However, using a system with an engine, you should very carefully assess whether the hot water produced by the system can be used in your facility. Seeing that you use a lot of throwaway steam, you might assess the possibility of preheating the replenishment water for the steam boilers with the low-temperature energy produced by the engine. For other possible uses of the water, we would need to examine your production cycle in detail.
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