Analysis of annual energy consumption by a warehouse building

. This analysis was carried out to present the distribution of energy demand for air heating, air cooling and technology equipment for a warehouse through the year. The supplied energy is used to maintain the assumed temperatures in the rooms and for the needs of technology. During the work, the calculation model of the building was prepared and imported into the calculation program. The simulation was based on the planned building parameters (partitions structure, dimensions, technology) taken from the architectural executive design. Several versions of the structure of the construction and technical equipment have been analyzed. The obtained results show differences in the formation of energy demand and indoor room conditions.


Introduction
This article presents the results of calculations of the possibility of obtaining the "zero energy" effect by an exemplary warehouse building. This effect will be obtained using innovative technical and construction solutions limiting the energy demand of building. By increasing the use of elements that acquire renewable energy, it will be possible to achieve the "plusenergetic" conditions of the building [1,6,9,10]. The analysis was based on: 1. Execution of heat and cool balance and electricity consumed by the building. building about 155 m. In the lower part inside air temperature is 20-28°C, in higher part the inside air temperature 5-28°C. In simplest version, ventilation was based on natural ventilation. In version with the mechanical ventilation air flow was determined based on the number of air change rates, which was assumed as 25% of the total building volume. The air flow is therefore 26500 m 3 /h. The supply air to the lower part can be taken directly from the outside (and can be further treated in AHU) or it can be previously passed through the ground heat exchanger (and pre-treated can be directed to the AHU). According to the assumptions, pretreated air is supplied to the lower part by the ventilation system. Depending on the period, the air is either removed directly outside (summer periods) or is further directed to the higher part (winter, autumn and spring periods). It is also planned to use in the lower part additional air-conditioning systems. For the higher part a separate ventilation system is planned. In summer periods, when the entire air stream from the lower part is removed directly to the outside, a total air stream is prepared and treated in the AHU -26500 m 3 /h. In other periods (winter, autumn, spring), when the air stream from the lower part is directed to the higher part, in the AHU for the higher part, the difference between the supply and exhaust air stream 15000 m 3 /h, is prepared and treated -the exhaust air stream remains constant 26500 m 3 /h. In addition, for the higher part, additional devices are envisaged, such as air conditioning units and destratificators, whose task will be to shed warmer air from the space under the roof to lower zones (due to rising and accumulating masses at elevated temperature) and leveling the air temperature.  The influence of temperature of stored products on indoor air temperature was not taken into account. In assumptions, it was not much different from the internal air temperature.
However, in fact, the additional mass would better stabilize the internal conditions.
For the purposes of model analysis, the building was divided into 2 m wide horizontal zone. The lower part of building consisted of 5 zones, the higher consisted of 12 zones. The calculations take into account the building accumulation and possibility of energy transfer between the zones.
For the analysis, the following assumptions were made: -work on three shifts -according to the information from the Investor, 30 working people at the same time, -heat gains from people were taken at 100 W/person, -according to the information from the Investor, the installed electrical power 70 kW in the lower part and 100 kW in the higher part (80% coefficient of simultaneity). -40% of heat gains from installed electric power, 90% heat gains from lighting, -for the higher part no heat gains from lighting installed, no heat gains from the people, -for the lower part 30% of heat gains from installed electric power and lighting, 70% heat gains from technology and heat gains from 30 people, -all internal heat gains were determined based on the area of calculation zones, Examples of the Variants of the developed building simulation models: 1.
The output model No.1partitions very good thermal-insulated, heat tranfer coefficient U = 0.1 W/m 2 K. In all computational areas natural ventilation. 2.
The output model No.2 -partitions very good thermal-insulated, heat tranfer coefficient U = 0.1 W/m 2 K. Mechanical ventilation system (supply-exhaust) with ground heat exchangerair supply to the lower part, exhaust from the higher part. 3.
The output model No.3 -partitions very good thermal-insulated, heat tranfer coefficient U = 0.1 W/m 2 K. Mechanical ventilation system (supply-exhaust) with heat recovery from the higher partair supply to the lower part, exhaust from the higher part. High efficiency ground heat exchangers. Extended air supply-exhaust system in the lower and higher parts.

Results of calculation and analysis
The results of simulation model of the analyzed building, are presented below. The simulation was carried out on the actual parameters of the building (transparent, opaque walls, geometry) and was taken from the architectural executive design.
The table presents a comparison of heat gains depending on the position relative to the world sides. The building is heated using internal heat gains (technology, lighting). By turning the building towards the world sides, a slight impact of the energy demand was observed.
The numbers on the horizontal axis represent the day of the year and the time of the day (e.g. January 1 to January 1, 01:00). The series numbers indicate the horizontal zone number measured from the bottom of the room. The zones have a thickness of 2 m. The line without markers in the diagrams indicates the outside air temperature values.
On the figures below some results are shown for the days with minimum and maximum outside temperature (16 th of February and 7 th of June).  Using mechanical ventilation and ground heat exchangers, there is a need to reheat the lower zones (it is calculated). The upper zones (roofs) also requires a slight heating [3,5,8].     Internal heat gains allow to mantain the assumed minimum temperature without heating up.

Non-insulated building
In this system it is planned to supply air into the lower zones above the floor and exhaust from the upper zones. In the winter period the exhaust air will be transferred to the lower zones. Additionally, the air will be supplied into the warehouse by the AHU with the use of ground heat exchangers [4]. The amount of heat supplied is sufficient that, with the participation of internal heat gains, there is no need to heat up the warehouse [1,7].     The building required only to heat the lower part in the winter season. Heat gains from operating indoor devices and lighting in the lower part were taken into account in the calculations. An additional element limiting the heating demand of the higher part is the difference in maintained air temperatures in the rooms in both parts. In the higher part higher temperatures were obtained than the lowest acceptable for the room.
In addition can be shown how the inside temperatures were shaped in model No. 3 in winter and in the summer. Interesting is that in winter in higher part of the building the higher temperatures were got than the lowest admissible for this space without additional heating energy.
With a more extensive microclimate shaping system, more room temperature stability was obtained in the rooms.   For the summer period, due to good insulation, the operation of ground heat exchangers and building accumulation, there is also no need to sub-cool the rooms [4,7].