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Monday, 04 May 2015 08:11

How to Manage Heat in Greenhouses

Direct combustion

One of the dispensing systems using CO2 combustion gases are hot air generators with direct combustion (combustion gases remain inside the greenhouse). The generators are low power (50-100 kW thermal) and they are distributed along the greenhouse surface according to CO2 production or as heat required.

For this purpose, the burner hot air generator has a separate combustion chamber with the possibility of using outdoor air as standard combustion avoiding problems arising from an atmosphere vitiated by an excess of CO2 when they are used as heating system.

How to distribute the heat?

Gas and heat obtained are distributed in the greenhouse with the help of a fan with an adequate airflow and dart range, providing a good distribution of heat and CO2.

Central heating

When the heating of the greenhouse install a system with a single generator (central heating system), this can be operated during the day period with the dual purpose of:

  • Cover the demand for CO2 day period
  • And heating during the night

How to distribute and store the heat in a greenhouse?

To store heat is required a insulated accumulation tank of sufficient capacity to store the generated heat production due to the demand for heat and CO2.

To use and distribute gases it requires a recovery heat system sensible and latent of these gases (condenser) so its distribution and dosage will be possible in a network constructed with plastic materials, typically PVC and LDPE, with the help of a centrifugal fan medium pressure (300 mm.ca).

Internal Combustion

Cogeneration systems used in greenhouses to obtain electricity for artificial lighting installation or for disposal in the electric network, use internal combustion engines with natural gas.

Heat and combustion gases obtained are exploited by management and conditioning as an energy source and as a source of heating dioxide.

How to manage Heating?

This is similar to the management of central heating systems with the differents characteristics of each one. When natural gas is burned in gas engines, approximately 0.2 kg of CO2 is produced per kWh of energy input.

This CO2 is present in the engine exhaust gas in a concentration of about 5 to 6% by volume. Escapes require purification using special catalytic converters (SCR and oxidation catalytic converters).

They are also cooled by a heat exchanger to about 55 ° C, and they are supplied in the greenhouse by a network built with plastic materials with the aid of a centrifugal fan. A device constant measurement of carbon monoxide and ethylene gas ensures maximum safety for people and the culture.