Text written in Basque and translated automatically by Elia without any subsequent editing. SEE ORIGINAL

Renewable energies in greenhouses

The greenhouses serve to store the heat of the sun and warm the environment. At Neiker-Tecnalia, they are studying alternative systems for heating greenhouses, systems based on renewable energies (biomass and solar radiation).

The greenhouses serve to store the heat of the sun and warm the environment. But if you want to maintain production throughout the year, the heat of the sun is not enough; plants need heating systems.

Until now, gas-oil boilers have been used on farms to maintain the temperature of vegetables, but the high price of oil has led to a loss of profitability. At Neiker-Tecnalia, they are studying alternative systems for heating greenhouses, based on renewable energies: biomass and solar radiation. We're

at Neiker's residence in Derio. In these greenhouses, they grow tomatoes of the Jack and Goloso varieties, which are recognized by the Eusko Label brand. The tomatoes are kept constantly at a temperature of 21 degrees. The light of the sun is not enough. These greenhouses are heated.

MIKEL ANZA; NEIKER-TECNALIA: These plants need to be heated if we want to produce them all year round; if we want to have tomatoes and peppers all year round. On the other hand, since the origin of these plants is in Central America, they require a lot of temperature to grow, and if we keep some minimum temperatures, both during the day and at night, we achieve a greater production, more homogeneous and of better quality. The heating systems

in the greenhouses are automatic; they are equipped with sensors and thermostats to control the temperature. However, heating such a large space requires a high energy expenditure.

MIKEL ANZA; NEIKER-TECNALIA: Normally, the air has always been heated, but keep in mind that in greenhouses the volume of air is very large, so to heat this whole volume, the expense is quite high. We’re trying to heat the roots, and that’s what we do with low-temperature water, both from the biomass boiler and from thermodynamic plates. We heat the roots, because we know that this way we have the opportunity to reduce the temperature of the air considerably, especially at night, without any damage to production or

quality. Here we see the two water transport systems. On the one hand, the high temperature water coming from the biomass boiler at 80 degrees in these iron pipes. Here, on the other hand, in these wrinkled pipes, the low-temperature water coming from the thermodynamic plates is transported at 45 degrees, and this is how we manage to heat the

entire root system. Diesel boilers commonly used on farms are no longer profitable. In addition, they release greenhouse gases. That’s why Mikel and his team are studying alternative energy sources.

MIKEL ANZA; NEIKER-TECNALIA: What we have behind us here are thermodynamic solar panels. With this system, combined with a heat pump, we will get water at a low temperature, around 40-45

degrees. When the gas exits the compressor it is frozen and enters this way through these circuits. With this, we achieve the following: as the volume of the gas increases, its pressure drops and the temperature is restored in this system. It is enough that the temperature is five degrees below zero; the system works very well.

The system is very efficient. We produce 3 or 4 kW of each kilowatt we consume in the form of heat, hot water. Heating

the roots of tomatoes reduces energy expenditure, but it is not enough. The radiant floor installed in the greenhouse needs much warmer water. Neiker's biomass boiler has been installed. The fuel he uses is pellet, compressed wood extracted from sawmill waste.

MIKEL ANZA; NEIKER-TECNALIA: Of course, when we burn that, we emit CO2 into the atmosphere. But if we take into account the entire process cycle, the net balance tends to zero. In fact, trees, when grown, assimilate CO2 and, compared to diesel, it is a renewable fuel.

What we have here is a cyclone. Centrifuge the smoke coming out of the boiler and collect all the particles down here. That’s how we make all the smoke that comes out into the atmosphere clean.

This biomass boiler has a heating capacity of 450 kW/hour. There are smaller ones, for use in homes, there are also larger ones... But this has been the most powerful biomass boiler ever installed to heat greenhouses. Its efficiency is 90%.

Note that the heating capacity of the pellet is 5 kilowatt-hours. One kilogram of diesel (1.17 litres) has a capacity of 10 kilowatt-hours, which is double, but there is a significant change in the price. In fact, a kilogram of pellets costs 20 cents, and diesel, as we all know, costs almost one euro.

This year’s crop is the first to grow by combining these two heating systems. Neiker’s researchers not only study the profitability of energy sources, but also the quality of tomatoes. The aim is to achieve the best possible product at the lowest cost and in a way that is as environmentally sustainable as possible.