Cogeneration for greenhouse complexes: maximum heat recovery
Volodymyr Kononchuk — 08.09.2026
EN
Volodymyr Kononchuk — 08.09.2026
A greenhouse complex is one of the few facilities where heat from a cogeneration plant can be utilised almost entirely. In winter, it is used for heating, soil and air heating, whilst the electricity is used for lighting, ventilation, irrigation and automation.
In a properly designed system, treated exhaust gases can serve as a source of CO₂ for plants. This is precisely why cogeneration for greenhouses can simultaneously reduce energy costs, increase self-sufficiency and boost crop yields.
Cogeneration works best where there is a simultaneous and stable demand for electricity and heat. A greenhouse complex meets this condition better than most other facilities.
That is why the CHP unit for a greenhouse complex is selected primarily on the basis of the actual heat and electricity consumption profile. It is important to take into account not only the area of the greenhouses, but also the crop, the type of covering, the use of supplementary lighting, the ventilation regime and seasonal peak loads.
A cogeneration plant generates electricity by burning gas or biogas, whilst the heat from the engine and exhaust gases is not lost but is recovered via heat exchangers and used to meet the consumer’s needs. Pro-Energy’s documentation for cogeneration systems states a total efficiency of 80–90 per cent, as a single energy source is used to produce two useful outputs simultaneously — electricity and heat.
This is particularly important for greenhouse farming: heat that might be difficult to utilise fully at another facility has a clear use here.
A greenhouse consumes two resources simultaneously and continuously:
The heat-to-electricity ratio in a greenhouse is usually between 3:1 and 5:1. This is almost the ideal profile for a combined heat and power plant, which generates both types of energy simultaneously in roughly equal proportions (1 kW of heat per 1 kW of electricity).
Unlike industrial plants, where in summer there is often nowhere to put the heat generated by the central heating system, a greenhouse is able to utilise as much of the heat produced as possible — even in the off-season, it is used for soil heating or in reserve circuits. Add to this:
When gas is burnt in a CHP engine, CO₂ is produced — the very same gas that plants absorb during photosynthesis. Increasing the CO₂ concentration in a greenhouse from the natural level of 400 ppm to 800–1,000 ppm directly accelerates growth and increases crop yields by 20–30 per cent. In other words, cogeneration in a greenhouse produces not two, but in fact three products simultaneously: electricity, heat and plant fertiliser.
Heating a greenhouse using cogeneration can be organised using air, water or combined systems. The choice depends on the greenhouse design, temperature conditions and the number of heating circuits. The key objective during the design phase is to maximise its use within the greenhouse complex’s operational cycle.
The simplest option looks like this:
Heaters warm the air, which is then distributed throughout the room. This setup may be suitable for polytunnels and facilities where a simple heat distribution system is important.
Its advantage is that it is fairly straightforward to integrate. Its disadvantage is that it offers less flexibility than a water-based system, particularly if the greenhouse complex has several zones with different temperature regimes.
In this case, heat from the CHP unit is transferred via a heat exchanger to the water circuit:
Hot water can be used in various circuits for:
The water circuit makes it possible to divide the greenhouse complex into zones and supply heat to them according to actual demand.
A combined system, in which heat is distributed amongst several consumers, offers the greatest potential.
For example:
In this configuration, different temperature settings can be used for different circuits. This helps to avoid a situation where the heat generator produces heat but has nowhere to send it.
It is the correct integration of the waste-to-energy system that determines how close the project will come to maximising the use of thermal energy.
A thermal buffer is required to balance the load. The CHP unit can operate at optimum capacity, whilst excess heat is temporarily stored in the buffer tank.
This is particularly important for operating modes where heat consumption varies throughout the day. For example, during the day, some of the heat may be drawn off by the heating system, whilst during periods of lower demand, thermal energy is stored and used later.
The buffer tank capacity should not be determined using a one-size-fits-all formula. It depends on the capacity of the central heating unit, the consumption profile, the volume of the heating circuits and the system control strategy.
A properly designed system enables the use of CO₂ from CHP as an additional resource for plants in the greenhouse. At the same time, the exhaust gases are not fed directly into the greenhouse: they undergo purification, cooling and quality control before entering the growing area.
The general reasoning is as follows:
Exhaust gases pass through a purification system. The project must monitor the concentrations of hazardous components, in particular nitrogen oxides and carbon monoxide. Once treated, the gas can be fed into the greenhouse via a pipework system.
Perforated pipes laid out in the growing area are used to ensure an even distribution of CO₂.
The supply of CO₂ is synchronised with periods of active photosynthesis — usually during daylight hours or when supplementary lighting is in operation. If vents are open or ventilation is intense, some of the CO₂ is lost, so the system must take into account the ventilation regime and the microclimate of the greenhouse. The optimum operating concentration is 800–1000 ppm.
| Culture | Increase in yield |
| Tomatoes | +20–30% |
| Cucumbers | +25–35% |
| Greens | +15–25% |
| Flowers | +10–20 per cent and better quality |
The capacity of a gas-fired boiler is determined by two main parameters: electrical and thermal load.
The thermal load depends on:
The approximate figure for winter in Ukraine is 150–250 W/m². For example, a greenhouse with an area of 1 hectare has a floor area of 10,000 m². If we assume a load of 200 W/m², we get:
10,000 × 200 W = 2 MW thermal load.
This does not mean that a 2 MW cogeneration unit must necessarily be installed in the greenhouse. Cogeneration involves the simultaneous production of electricity, and the heat balance must correspond to the actual consumption schedule.
Supplementary lighting, where provided, adds 50–100 W/m². Ventilation, irrigation and automation account for a further 10–20 W/m². In practice, this means:
A combined heat and power (CHP) plant generates both electricity and useful heat simultaneously; therefore, its capacity is determined by the actual load profile for both types of load. In a typical gas-fired CHP plant, the ratio of electrical to thermal output is close to 1:1, although the specific values depend on the model and operating mode of the equipment.
In general, the capacity of a greenhouse heating system is determined by a simultaneous analysis of the hourly electrical and useful heat loads. The area of the greenhouse or the percentage of the winter heat peak cannot, in themselves, serve as selection criteria. It is necessary to take into account the consumption profile over a 24 hours and throughout the year, the need for supplementary lighting, temperature regimes, the heating system, the ability to store heat and the availability of a backup source.
At the same time, taking peak loads into account is important for reducing operational and business risks. During periods of peak consumption, part of the demand can be met by a gas boiler or another backup heat source, whilst it is advisable to operate the CHP plant primarily in a stable base-load mode. This approach makes it possible to avoid oversizing the CHP plant’s capacity and to improve its operational efficiency.
A 3-hectare (30,000 m²) greenhouse: requires 6 MW of heat in winter and approximately 1 MW in summer; the electrical load, excluding supplementary lighting, is 300 kW. The limiting factor here is electricity, so the CHP unit is selected to produce 300 kW of electricity and, accordingly, 300 kW of heat, covering only 5–30 per cent of the heat load — the remainder is provided by the boiler. An alternative option is to install a 1 MW CHP unit and sell the surplus electricity generated to the grid.
The figures given below are guidelines for preliminary planning, not a final design selection.
| Greenhouse area | Power of the CHP | Note |
| 1 hectare | 200–500 kW | Without backlighting |
| 1 hectare | 500–1,000 kW | With backlighting |
| 3 hectares | 500–1,500 kW | A typical complex |
| 5 hectares | 1,000–2,000 kW | Cascade 2–3 of CHP |
| 10 hectares | 2,000–4,000 kW | A large complex |
Note: this table shows examples of possible ranges — do not use it to select equipment.
For large greenhouses, a cascade of several units often offers greater flexibility than a single high-capacity machine. If the load decreases, some of the units can be switched off, whilst the rest can be left running at optimal efficiency.
The main potential lies in savings on greenhouse heating and a reduction in the amount of electricity purchased from the grid. The CHP plant uses gas to generate both electricity and heat simultaneously, so the fuel’s energy is utilised much more fully than in a system with a separate boiler and the purchase of electricity.
Let’s take, for example, a greenhouse complex covering an area of 3 hectares, growing tomatoes and equipped with a 500 kW power unit.
The model incorporates:
The total estimated effect amounts to €210,000 per year. Under this model, the simple payback period is:
€563,000 / €210,000 ≈ 2.7 years.
This is an indicative calculation scenario. The stated cost of the CHP unit is for guidance only and includes delivery and commissioning, but excludes VAT. The actual payback period will depend on the price of gas, electricity tariffs, the operating regime of the gasification unit, CAPEX and OPEX, the number of operating hours, and the actual economic benefit derived from the use of CO₂. Before making an investment decision, these parameters must be calculated for the specific greenhouse complex.
You can find out more about other applications of the technology and the economics of cogeneration projects in the article “Cogeneration for small and medium-sized businesses”.
If a greenhouse complex has access to its own or a local supply of raw materials, cogeneration using biogas and biomethane can reduce dependence on purchased natural gas and create added value from organic waste.
Using the farm’s own biogas enables electricity and heat to be generated directly on site, whilst the digestate produced after anaerobic digestion can be used as an organic fertiliser, provided its composition and quality meet the farm’s requirements.
The economic viability of such a system depends on the cost of producing biogas, the cost and availability of raw materials, the operating costs of the biogas plant, and the actual volume of electricity and heat consumed.
Potential sources may include:
The biogas plant produces biogas, which is burned by the CHP unit, supplying the greenhouse with heat, electricity and CO₂. The digestate from the biogas plant is returned to the greenhouse as fertiliser — creating a closed-loop system with no external fuel costs.
Cogeneration is not simply a piece of equipment that can be installed next to a greenhouse. The economic outcome is determined by the entire integration system.
The unit can be housed in a separate building or in a containerised configuration. It is important to bear in mind:
The shorter the heating pipes between the central heating plant and the greenhouse complex, the fewer the potential heat losses and the simpler the hydraulic layout.
The main circuit transfers heat to the greenhouse heating system, whilst the emergency circuit comprises mandatory dry cooling towers for dissipating excess heat during the warmer months. The buffer tank capacity is calculated at 5–20 m³ per 1 MW of installed capacity.
A catalytic neutraliser costs €10,000–30,000, CO₂ distribution pipework costs €5,000–15,000 per hectare, and the automated supply control system costs €5,000–10,000.
If there is nowhere to channel the heat, one of the key benefits of cogeneration is lost. This is particularly critical for a greenhouse, as the seasonal and hourly heat balance must be determined in advance.
During sudden changes in load, the CHP may not operate at its optimum. The buffer capacity helps to smooth out these fluctuations.
In summer or during periods of low thermal load, the system must be able to dissipate excess heat. Otherwise, the operation of the CHP unit will have to be restricted.
CO₂ does not act on its own. If the greenhouse is ventilated, the gas escapes. If there is insufficient light or the plant is unable to utilise the additional CO₂, the expected effect will be less pronounced.
A greenhouse is one of the most logical facilities for cogeneration, as it requires both electricity and a significant amount of heat. A CHP plant for a greenhouse complex can generate its own electricity, use the heat for heating, and if the system is properly designed, provide an additional source of CO₂.
It is easier to work out which system and capacity are best suited to your specific facility by looking at examples — take a look at Pro-Energy’s completed cogeneration projects for various sectors.
A greenhouse is one of the most logical facilities for cogeneration, as it requires both electricity and a significant amount of heat. A cogeneration unit can provide its own power, use the heat for heating, and – if the system is properly designed – provide an additional source of CO₂.
The estimated figures of 200–500 kW per hectare without supplementary lighting and 500–1,000 kW with supplementary lighting should be used for preliminary assessment only. The actual power output is determined by the energy profile of the complex.
Would you like to find out whether cogeneration would be a worthwhile investment for your greenhouse complex? Contact Pro-Energy for advice. We will assess the greenhouse area, the crops grown, the electricity and heat consumption patterns, and the available fuel, and select the optimal cogeneration unit configuration.
Approximately 200–500 kW per hectare without supplementary lighting, and 500–1,000 kW with supplementary lighting. The exact calculation depends on the type of covering, the crop, the climate and the operating conditions.
Increasing the CO₂ concentration from 400 to 800–1,000 ppm boosts yields by 20–30 per cent for tomatoes and cucumbers. This requires a catalytic neutraliser and a CO₂ distribution system.
2–3 years — the fastest of any sector. This is achieved through 100 per cent heat recovery and the additional benefit of CO₂.
Yes, that is the best option. Sources of biogas: plant waste from the greenhouse, a neighbouring farm, and food production. The digestate is used as fertiliser. The result is complete energy self-sufficiency.
That is usually the case. The central heating system covers 50–70 per cent of the heat load (the base load), whilst the boiler handles peak loads and periods of severe cold. This is the optimal setup in terms of reliability and cost-effectiveness.
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