In collaboration with researchers of the Institute of Agricultural Research and Training (IFAPA), the group has developed several projects in relation with:
- Use of solar energy in greenhouses.
- Optimisation of irrigation in greenhouses.
- Modeling, control and optimisation of fotobioreactors.
The centre of the installation is an experimental greenhouse of 1900 m2 located in the IFAPA centre next to the University of Almería (Almería, Spain). The greenhouse is divided into two sectors of equal size and is equipped with a multitude of systems that allow a great deal of control over the growing conditions. It has a ventilation system consisting of 13 motors (90 W), six of which are destined for the zenithal windows and the rest for the lateral bands. It also has an LED lighting system consisting of four LED PAR radiation lamps with a power of 300 W each and a dehumidification machine with an electrical consumption of 11.2 kW. For thermal conditioning, the experimental greenhouse is equipped with six 26.1 kW air heaters with an air flow rate of 1990 m3/h and a power of 26.1 kW, which allow for the homogeneous distribution of heat or cold inside the greenhouse. These fan heaters are connected to a thermal conditioning system (see Figure 1) consisting of a 60 kW reversible heat pump with a thermal power and a COP of 4, a 160 kW biomass boiler mainly fuelled by pellets and a 4000 litre buffer tank. The experimental greenhouse also has a CO2 injection system by means of a distribution dripper with emitters every 0.25 m that are installed in PVC pipes placed along the greenhouse surface. The CO2 injection system consists of a pure CO2 tank of 6190 litres and an active carbon tank that stores the CO2 from the combustion in the hip and injects it into the greenhouse by means of a 5.5 kW blower. Both the thermal conditioning system and the CO2 reuse and injection system have a control system that manages all the variables of the system for automatic and efficient operation.
The experimental greenhouse is also equipped with a humidification system using 40 and 16 mm PVC pipes for air and water respectively and 125 0.8 mm nebulisers located every 1.6 m over the entire surface of the greenhouse. This system is equipped with a 7.5 HP air compressor and a 1.5 kW electric pump. On the other hand, to satisfy the water and nutrient demands, the greenhouse has a fertigation system, by means of a dripper located every 0.25 m, with a consumption of 5 m3/h at 3 bar pressure, which has two conductivity sensors and two water content sensors connected to an irrigation controller. The CO2 injection system, as well as the humidification and fertigation systems, can act individually in each of the two sectors of the greenhouse or in both at the same time.
Two distillation systems (see Figure 2) are available to supply the greenhouse’s water demands. The first of these is a reverse osmosis (RO) unit with a consumption of 3 kWh/m3, fed directly from a 100 m3 seawater tank and capable of generating 11 m3 of osmotised water per day. The osmotised water is stored in a 100 m3 tank and is used in both the thermal conditioning system and the fertigation system described above. An auxiliary well water tank is available to supply these systems in case osmotised water is not available. On the other hand, the RO unit generates 22 m3/h of brine which is stored in a 50 m3 tank and used to feed the second distillation system. This is a membrane distillation (MD) unit capable of generating 6 m3/day of distilled water. This water is stored in a reservoir and used to feed the humidification system described above. The MD unit requires a continuous heat source provided by a solar thermal generation system (see Figure 3) consisting of 30 plates. Auxiliarily, a biomass boiler similar to the one described above is available to meet the thermal demands of the MD unit in case the solar thermal system is not operational.
To ensure the electricity supply of the installation, there is a photovoltaic generation installation (see Figure 3) consisting of two units of 18 photovoltaic panel modules with an electricity generation capacity of 16.2 kW, two hybrid inverters and two batteries with a capacity to store 44.2 kWh.
In order to monitor system variables and weather conditions inside and outside the greenhouse, there are six indoor measuring stations to measure temperature, relative humidity, ambient pressure, leaf humidity, solar radiation, PAR radiation and CO2 concentration; or even soil variables such as volumetric content, conductivity and soil temperature. There are also two outdoor weather stations that measure external variables such as precipitation, wind speed and direction, inclination or occurrence of lightning.