THE SOLAR ABSORPTION COOLING IN BUILDING

Budownictwo o zoptymalizowanym potencjale energetycznym Danica KOŠIČANOVÁ, Pavol FEDORČÁK Technical University of Košice, Slovakia THE SOLAR ABSORPT...
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Budownictwo o zoptymalizowanym potencjale energetycznym

Danica KOŠIČANOVÁ, Pavol FEDORČÁK Technical University of Košice, Slovakia

THE SOLAR ABSORPTION COOLING IN BUILDING

This article deals with reducing electricity consumption for cooling and to the achievement, "buildings with nearly zero energy" in small buildings. To achieve such an idea, absorption equipment with capacity up to 5 kW is used. An experimental room - classroom in rectangular shape 6 x 7 m with capacity of 13 people, was used to evaluate the system. The absorption unit drive will provide vacuum solar collectors with flat 14 m² and electric energy that necessary will be delivered to the device covered with photovoltaic panels with an accumulation battery.

INTRODUCTION Increasing energy demands of the population and the resulting rapid depletion of non-renewable energy sources, leads us to find new ways to save energy. One of the areas with considerable impact on the energy consumption, are systems that provide thermal comfort in the building environment. This is mainly related to the use of air-conditioners, which have recently become a standard part of both small and large buildings. For the operation of these devices, the ideal form would be that these could make full use of renewable energy sources and thus consume the least electrical power. On this basis, by the functioning of the cooling system, the means would be the least burdened [1].

1. SOLAR COOLING Solar cooling is a technology that transfers heat from the sun into the refrigeration equipment (Fig. 1). In this process, the solar heat is collected and used to heat controlled cooling process, whose result is cold water or conditioned air for use in the building. Solar cooling is used the most in a commercial environment, but increasingly will be required in the home [2]. Solar cooling is a technology with a range of options that exist thanks to the availability of a series of elements that can be used to capture solar heat, heatdriven process of cooling and his delivering into the cooling system. From wider perspective, we know to divide solar cooling cycle into open and closed circuit system [3]. Solar cooling systems are composed of several key elements (phases) Figure 2.

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Fig. 1. Diagram of solar cooling

Fig. 2. Phase of the solar cooling system [2]

2. THE APPLICATION OF SOLAR ABSORPTION COOLING As the renewable source of energy is selected solar energy with its subsequent transformation into thermal energy through solar panels. On the other hand, are progressive systems of technology environment as the absorption device, which produces cold for cooling.

2.1. Current status On the research of progressive systems engineering environment and renewable source of energy was selected school building, in which the solar cooling will be installed. The building is situated in Košice, Vysokoškolská 4 Street, north part of the city. School is used for education and for research doing by students of Civil Engineering at the Technical University in Kosice (Fig. 3). The main entrance to the building is from the southeast side. It is a four-storey building. The first three floors are mostly private offices and classrooms. The last floor consists of studio rooms. Within the solar cooling the studio rooms are ideal, because in the summer months are very warm. For testing the function of solar cooling system, firstly we chose an experimental room, in which the solar cooling will be installed. This is a lecture room, located on the floors 3.NP. It's a corner room, where the one of the parts of the facade is oriented to the southeast and the second part of the facade is oriented to the northeast. The cladding U = 1.22 W/(m2 K), windows (old and wooden) are on both sides of the facade U = 2.8 W/(m2 K). The room is full from 8:00 am to 18:00, where 13 people are staying (Fig. 4).

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Fig. 3. School building

Fig. 4. Classroom surveyed plan

For the economic and energy comparison was selected the next room, from the perspective of current measurements of heat stress. This is the same ground plan room located right below the first selected lecture room. In this room the compressor cooling will be installed. In a term of application and transfer to the other shapes of rooms and buildings we were chosen rooms in a rectangular shape.

2.2. Description of the proposal state Because of simulation calculations we carry out a preliminary draft of solar system and also the absorption refrigeration unit in the selected experimental room. The results of these simulations are compared with measured and calculated values of electricity consumption for cooling the room. For the experimental room was designed solar system with 7 solar panels (Fig. 5). The solar panels will be placed on the roof towards the south side under an angle of 45°C. In a term of bigger efficiency the vacuum tube collectors will be used.

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Fig. 5. Vacuum collectors on a sloping roof

The absorption unit will be used in output of 5 kW (Fig. 6). It is a single-stage cooling unit consisting of four main sections: evaporator, compressor, condenser and expansion valve.

Fig. 6. Absorption chiller 5 kW

Fig. 7. Solar panel with battery

To achieve “building with nearly zero energy consumption“ we use the photovoltaic panels with an accumulation battery, which cover the electricity consumption of the absorption unit and fans which provide fresh air into the room (Fig. 7).

2.3. Simulation The solution of the solar simulation cooling system is primarily based on the actual spatial layout of the selected experimental room in which the system will be installed. As it was already mentioned, in the rooms there will be formed the thermo weight from 13 people, from lights, heat gains by convection, radiation from the sun and from the supply of the fresh air into the room. By this simulation, the room was assessed for 21 July, when it is assumed to be the highest heat load. In the room the simulations were done without ventilation - without the supply of the air and later on with the fresh air in the program Simulace 2008 and program Microsoft Excel.

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The solar absorption cooling in building

Figure 8 shows the heat load in the room during the day time, where one curve shows the heat load without the supply of fresh air, a second curve shows the heat load with the supply of fresh air after the students comes in the class. The graph (Fig. 9) shows the progress of need for the cool in the room during the day time, where one curve shows the cool need without the supply of the fresh air, a second curve shows the cool need with the fresh air after the students come in the class. Subsequently, I processed the comparison of prices and production CO2 (Fig. 10) with compressor and absorbenfacient cooling, where the need for the cool for the 21 July is the same as for a whole month.

Heat load in the room during the day 9000 8000

Heat load [W ]

7000 6000 Without treatment of fresh air

5000 4000

With the treatment of fresh air

3000 2000 1000 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Hours during the day [h]

Fig. 8. Heat load in the room during the day

The need to cool the room during the day 2000 1800

need for cooling [W ]

1600 1400 Without treatment of fresh air

1200 1000

With the treatment of fresh air

800 600 400 200 0 8

9

10

11

12

13

14

15

16

17

Cooling time [h]

Fig. 9. Need a cool room during the day

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Table 1. Comparison of compression and absorption chiller Compressor cooling COP

Absorption cooling

price for electricity

CO2

eur/kWh

kg/kWh

COP

price for electricity

CO2

eur/kWh

kg/kWh

3

32.1

99.1

0.6

5.8

17.8

3

44.4

136.9

0.6

8.0

24.6

Note: 1 kWh = 0.201 € - according to the price for electricity supply from VSE in Slovak Republic. Necessary electrical energy and production CO2 CO2

Price 140,0 120,0

CO2 [kg/kWh]

price [€]

100,0 80,0 60,0 40,0 20,0 0,0 Compressor cooling

1 44,4

Absorption cooling

8,0

2

3 136,9 24,6

Fig. 10. Electricity consumption and production CO2

CONCLUSION Today is the beginning of awareness of that solar energy can be converted into the heat and electricity energy by using of absorption unit in a small exercise. It deals with the possible use of unconventional sources of energy with their using for cooling rooms with achieving of thermal comfort for humans. It's a right pure clean energy, which production in small amounts burdens the environment in contrast with the compressor cooling. The absorption cooling in a small scale is a new technology; therefore it is not very prospering from the economic point of view. This work has directly connection with solved research projects: VEGA project 1/0079/10 “Intelligent buildings for administration and related in-

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door technology for use of renewable energy and project VEGA 1/07/48/11, „Theoretical and experimental analysis of engineering environment systems in relation to their pollution by the effective utilization of renewable resources”.

Acknowledgement This work was funded by project VEGA 1/0748/11 Theoretical and experimental analysis of building services and HVAC systems from the point of view of microbiological risk and regarding to effective use of renewable sources.

REFERENCES [1] European Parliament and the Council on 2010/31/EU 19th May 2010 the Energy Performance of Buildings Directive (recast). [2] Available on the internet: < http://www.ausscig.org/what_is_it.html [3] Available on the internet: < www.AdsorptionChillers.com>