# Cumulative Energy Demand and Carbon Footprint of the Greenhouse Cultivation System
## 2 Materials and Methods  
A typical GH with a movable thermal screen is a facility with a variable envelope efficiency and a variable operating time, which acts as an additional cover (Figure 1). Based on measurement data, it was possible to determine the actual energy performance of a GH. Measurements were made in a self-contained GH, which is part of a larger GH facility. This GH facility is located in central Poland, in the town of Skierniewice. The territory of Poland is divided into five climatic zones. Skierniewice is in zone III, which covers more than 50% of the part of Poland. Zones I and II together cover 30% of the territory of Poland. The average annual outside temperatures in zones I, II and III are 7.6 \({}^{\circ}\)C, 7.9 \({}^{\circ}\)C and 7.7 \({}^{\circ}\)C, respectively. The average annual outside temperatures in zones IV and V are lower and amount to 6.9 \({}^{\circ}\)C and 5.5 \({}^{\circ}\)C, respectively. Therefore, production under cover in Poland is concentrated in zones I-III. Moreover, the analysed GH is fired with coal, which, in Poland, is still the most commonly used fuel in such facilities. The main limitation of the LCA method is the inability to directly compare the results, which are dependent on many factors, i.e., boundary conditions, production strategy and geographical location [30]. Since, in the present paper, different scenarios are analysed in the same facility, the disadvantage related to a geographical location is eliminated. The GH floor is intended for growing flowers in pots. The natural soil is covered with a 0.2 m layer of sand. It has thermal insulation made of 20 mm thick extruded polystyrene foam and 2 mm thick plastic fabric. The basic technical parameters of the analysed greenhouse are summarized in Table 1.  
Apart from the heat generated from coal combustion, auxiliary energy also needs to be taken into account. It sustains the operation of the heating systems, technical equipment of the GH and the source of heat. In the facility under study, electricity applies to:  
* The heating system to drive circulation pumps in a double way: the lower system located in between the plants, and the upper system consisting of heating pipes next to the side walls, at 2.5 m above the cultivation surface;
* The technical equipment of GH--to drive positioning motors of the thermal insulation screen and vent servos;
* The heat source to drive main circulation pumps of the heating system;  
Figure 1: GH under study: (**a**) A view of GH with thermal screen; (**b**) Main dimensions. * The heat source to power the boiler grate, induction draft fan, exhaust gas fan and the de-duster fan. In the existing facility, the heat source is a set of grate boilers for the combustion of fine coal with a lower heating value (LHV) of 21,000-23,000 kJ\(\cdot\)kg\({}^{-1}\). The boilers are equipped with dust removal devices with an efficiency of 85%, which reduces the number of solid particles carried in the flue gas. The basis for the analysis was the heat and electricity consumption tests carried out over the course of a full year with a 10-min interval between measurements. Such an interval between measurements gives a fairly accurate picture of the operation of the greenhouse's technical equipment, the variability of the outdoor weather conditions and indoor temperatures, as well as energy consumption. The total amount of data collected during the test period was 52,560 records. The relative error of the heat consumption measurement was 3.7%. The heat measurements were supplemented by recording additional parameters that make it possible to determine the operating time of electric drives used to maintain the operation of heating systems, vents, and the thermal screen in the GH. Additionally, the measurements were taken in the heat source, which is necessary to determine the operating time of individual boilers and heating system pumps. The measurements were carried out using two systems.