Category Archives: EuroSun2008-4

Impact of Domestic Solar Water Heating on an Energy Audit of a Residence in Malta

R. N. Farrugia1, C. Yousif1* and M. Villameriel Tejedor2

1 Institute for Energy Technology, University of Malta, Triq il-Barrakki, Marsaxlokk, MXK 1531, Malta 2 E. T.S. Ingenieros Industriales, Universidad de Valladolid, Paseo del Cauce, s/n 47005 Valladolid, Spain.

Corresponding Author, charles. yousif@um. edu. mt

Abstract

This paper describes the outcome of an energy audit that was carried out in a Maltese residence. Monitoring included all major electric appliances, artificial lighting, solar water heating, and indoor micro-climate conditions. Results showed that almost 40% of the electricity bill was attributed to the back-up heating element within the solar water heating system. Furthermore, a freezer and a fridge-freezer were found to operate continuously without stopping and were responsible for about 20% of the electricity bill. Appliances left in stand-by mode accounted for 10% of the bill. Only 13% of the light fixtures were energy efficient bulbs. Conclusions were that energy use at home was not only dependent on the efficiency of the appliances, but also on the lifestyle of their users, on their background knowledge of energy saving and on the level of their environmental awareness.

Keywords: solar water heating, energy audit, domestic, appliances.

1. Introduction

During the past 15 years, electricity consumption in Malta has been on the increase in spite of higher fuel prices, with maximum summer demand exceeding that of winter as of the year 2001 [1] . Moreover the gap between summer and winter electricity consumption is on the increase. Figure 1 shows electricity generation for four different years, where it is clear that the increase in electricity demand is also across all months and in all years and not for the summer period alone. Since 2001, the domestic sector has become the major consumer of electricity with a share of 36% (Year 2006), followed by the commercial sector at 32% and the industrial sector at 30%. The remaining 2% is attributed to street lighting [2] . Hence, it becomes increasingly important to explore ways and means of improving end-use energy efficiency in homes; bearing in mind the fact that this sector is also a major contributor to peak loads.

The home identified in this case study was situated in the locality of Swieqi, which may be described as an urban area with a high density of upmarket buildings. This project was initiated after the homeowner showed an interest to invest in renewable energy (RE) systems. Initial investigations identified high energy consumption rates — a situation that required redressing prior to the installation of any RE technologies. The dwelling consisted of a duplex — with a top floor apartment leading up to a penthouse. The apartment followed a fairly open plan design and comprised of a main living area with kitchen, laundry room / pantry, study and bedrooms. The penthouse consisted primarily of a lounge, conservatory, summer kitchen and patios.

Research Center Jablonna

D. Chwieduk1*, E. Kossecka1 and P. Murza-Mucha2

1 IPPT PAN Inst. of Fundamental Technological Research PAN, Swietokrzyska 21, 00049 Warsaw; Poland
2 GRAFFITI, ul. Boremlowska 30 A, Warsaw, Poland
* dchwied@ippt. gov. pl

Abstract

The Polish Academy of Sciences has undertaken an initiative to develop the programme on fostering research and application of renewable energy in the country. The core of the programme is to design and construct the Research Center Jablonna that will consist of the Intelligent Energy Building and complex of laboratories. The architectural concept of the 3 storey IEB building has been developed with regard to active and passive application of

solar energy. The shape of the building assures maximum gains of solar energy per year when it is necessary and shading of the interior of the building when it is required. Calculations of solar energy availability have been performed. Shading elements are included, apart from traditional devices as blinds, and building elements as overhangs, the PV modules are to be applied and natural green environment. All “south” rooms at the first floor are seminar and lecture rooms, the “north” rooms are technical — monitoring rooms. Keywords: Solar energy availability, solar architecture, innovative technologies.

1. Introduction

The Polish Academy of Sciences is the owner of different properties all over the country including estates and lands. One of them is a land of 600 000 m2 located at the north east side of Warsaw at Jablonna region. The Polish Academy of Sciences has undertaken an initiative to develop the programme on promotion the renewable energy application with focus on fostering research on innovative energy technologies. The main part of this programme is to develop project “Research Center Jablonna — Energy conversion and renewable energy” including construction of buildings of the Centre on selected part of the land.

The Division of Eco-Buildings of the Institute of Fundamental Technological Research at Polish Academy of Sciences takes part in the national project “Research Center Jablonna — Energy conversion and renewable energy”. This project is realised by the EkoEnergia Scientific Network that constitutes several institutes of the Polish Academy Sciences, leading national academic and applied research institutions in field of energy. The Institute of Fundamental Technological Research participates in the task “Elaboration of a concept of the Research Center and the base for its construction”. The important aim of this task has been to elaborate the architectural and technical concept of the Energy Center with focus on the Intelligent Eco-Building — IEB (shown in the middle of Fig.1) that is to have a function of the conference — training center and the hotel building as well and will be equipped with BMS — Building Management System and will demonstrate the innovative energy systems supplied by renewable energy and modern energy saving building construction technologies with respect to minimum of embodied energy.

image299

Fig. 1. The architectural concept of the Intelligent Eco-Building and laboratory buildings in Jablonna [3].

Total land area of the Research Center is 21.400 m2. There will be the IEB building (total area of 2000 m2, in the center of the Fig.1), connected to swimming pool (total area of 1100 m2, left to the IEB building), two laboratory buildings: one of Integrated Techniques of Solar Energy and Energy Storage (at the front left side of the Fig.1, total area about 1000 m2), the other of Micro­cogeneration and Ecological Boilers technologies (at the back right side of the Fig.1, total area about 900 m2), outdoor renewable energy testing field (between the Intelligent Eco-Building and Solar Laboratory) and Meteorological Station (at the south east part of the land). Just in the neighborhood (to the west) the Center of Innovative Technologies is planned to be constructed with total land area of 28.500 m2.

Analysis of energy supply strategies in housing retrofit

S. Herkel1*, F. Kagerer1, B. Kaufmann2 and J. Reiss3

1 Fraunhofer ISE, Freiburg, Germany
2 Passivhaus-Institut, Darmstadt, Germany
1 Fraunhofer IBP, Stuttgart, Germany
* Corresponding Author, sebastian. herkel@ise. fraunhofer. de

Abstract

1. Within the framework of the International Energy Agency’s (IEA) "Solar Heating and Cooling" implementing agreement, the working group "Advanced Housing Renovation with Solar and Conservation" Task 37 was set up with the goal of describing renovation standards that are possible today, looking into and discussing new developments and implementation strategies at an international level. The focus is on joint national and international renovation projects in residential buildings whose energy consumption for heat and cold supply (space heating, hot water, auxiliary systems, and ventilation) was to be reduced by a factor of four below the national standard. Monitoring results show a good agreement of measured energy consumption with the expected reduction of energy consumption by a factor of sometimes more than five. Solar and other renewable based energy supply systems enables a net zero energy approach even in building renovation.

2. Keywords: IEA SHC Task 37, Monitoring, Renovation, Energy supply, CHP

Simulation results and consideration

To give one example, Table 1 shows the areal seasonal average natural room temperature of each room in the un-air-conditioning case. From Table 1, for various areas in each room the decrease rate of natural temperature in perspiration mode to non-perspiration becomes bigger as the specific sense temperature lowers. As an example, from Table 1, the maximum temperature decrease at the sense temperature 20 °С becomes 1.1 °C(E/U) in Sapporo, 1.3 °С (E/U, Children) in Tokyo, 1.6 °С (E/U) in Osaka and 1.5 °С (E/U, Children) in Naha. Table 2 shows the decrease rate of sensible heat load (energy-saving rate) due to autonomous perspiration = 1 — (heat load in perspiration mode / heat load in non-perspiration mode). The energy-saving rate by autonomous perspiration also becomes bigger as the sense temperature lowers. It is 72.3 (sense temperature of 20 °C)-24.4%(sense temperature of 40 °С) in Sapporo, 30.6-11.4% in Tokyo, 31.2-12.9% in Osaka, and 24.2-10.0% in Naha, especially bigger in Sapporo.

Table 1 Average natural room temperature (°С) Table 2 Energy saving rate (%) due to autonomous

Подпись: CITY SPECIFIC SENSE TEMPERATURE CQ JUNE-SEPT. (%) JULY- AUGUST (%) SAPPORO 20 73.9 72.3 25 65.6 64.4 30 49.2 48.2 35 38.1 36.9 40 24.7 24.4 TOKYO 20 30.6 25 28.0 30 20.4 35 14.6 40 11.4 OSAKA 20 31.2 25 28.5 30 21.9 35 15.7 40 12.9 MAY-OCT.(%) NAHA 20 21.8 24.2 25 21.0 22.7 30 17.1 18.0 35 11.6 12.5 40 9.6 10.0

in each perspiration mode for various areas perspiration for various areas

ROOM

MODE

SAPPORO

TOKYO

OSAKA

NAHA

LD

SPECIFIC SENSE TEMPERATURE

( °С)

20 °С

24.0

27.2

28.3

29.9

25 °С

24.3

27.4

28.5

30.0

30 °С

24.5

27.7

28.7

30.2

35 °С

24.6

27.8

29.0

30.5

40 °С

24.8

27.9

29.1

30.6

NON PERSPIRE

24.9

28.3

29.5

31.0

BATHROOM

KITCHEN

SPECIFIC SENSE TEMPERATURE

( °С)

20 °С

24.3

27.5

28.6

30.1

25 °С

24.5

27.7

28.8

30.2

30 °С

24.8

28.0

29.1

30.5

35 °С

24.9

28.2

29.4

30.8

40 °С

25.1

28.3

29.5

31.0

NON PERSPIRE

25.3

28.7

30.1

31.5

ENTRANCE

UTILITY

SPECIFIC SENSE TEMPERATURE

( °С)

20 °С

23.2

26.5

27.6

29.0

25 °С

23.4

26.7

27.8

29.1

30 °С

23.7

27.1

28.2

29.5

35 °С

23.9

27.3

28.5

29.8

40 °С

24.1

27.4

28.6

29.9

NON PERSPIRE

24.3

27.8

29.2

30.5

MASTER

SPECIFIC SENSE TEMPERATURE

( °С)

20 °С

22.9

26.3

27.3

28.8

25 °С

23.1

26.5

27.6

28.9

30 °С

23.4

26.8

27.9

29.2

35 °С

23.5

27.0

28.2

29.5

40 °С

23.7

27.1

28.3

29.6

NON PERSPIRE

23.9

27.5

28.8

30.2

CHILDREN

SPECIFIC SENSE TEMPERATURE

( °С)

20 °С

23.2

26.5

27.6

29.0

25 °С

23.4

26.7

27.8

29.2

30 °С

23.7

27.1

28.2

29.5

35 °С

23.8

27.3

28.4

29.8

40 °С

24.0

27.4

28.6

29.9

NON PERSPIRE

24.2

27.8

29.1

30.5

Nu correlations for the air gap and the rear glass

The average convection heat transfer coefficients are derived from the Nusselt numbers (Nu ). In laminar free convection flows the Nu is obtained through different correlations: in the case of symmetric uniform heat fluxes the correlation of Roshenow with c=1.15 [14] is used, in the case of asymmetric uniform heat fluxes the new correlations obtained in this research (equations 1 and 2.) are used for hot and cold walls. In turbulent free convection flows, in the case of wide channels, the correlation of Churchill [5] is used. In forced convection flows, a distinction between developing and fully developed flows is made. In case of laminar developing flows, the correlations of Bejan [2] and Kays [10] are used. In case of laminar fully developed flows, the Nu are constants. In case of turbulent developing flows, a correlation obtained by Saelens [15] is used. Concerning to the turbulent developed flows, the equations of Kays [10] are also valid.

In the case when the rear glass is formed by multiple glass layers, the equations and correlations obtained for air cavities will be used.

Tested windows

Any coating used on the external surface of a window needs to be a hard coating that can resist the wear this surface is exposed to. For this reason hard oxides or nitrides should be used, and for the low emissivity coating fluorine doped tin oxide was used; a coating readily available on the market. The hydrophilic coating tested with respect to external condensation was a titanium oxide coating which is also already available on the market [9]. It is marketed for its “self cleaning” properties, however, and so far not for its effect on external condensation. Two test windows were prepared which consisted of triple glazed IG units with silver based soft low-e coatings on surfaces 3 and 5. For one of the two windows the outer pane was ordinary uncoated float glass and for the other one the outer pane was a hydrophilic coating on the external surface. This coating does not change the surface emissivity of the external surface and the U-value was identical for both windows and with argon filling the centre of glass U-value was 0.65 W/m2K. Both windows had warm edge spacers, although this had no effect on the formation of condensation in the middle of the window.

3.2. Experimental details

The test was conducted during the period September to December 2007, and the condensation was monitored in terms of its occurrence rather than number of hours. No detection equipment was used as was the case for the tests in the test box. A reason for this was the cost together with the fact that the windows were used in an ordinary family house. The condensation rate was thus recorded as “number of times condensation occurred” rather than as “number of hours”. It turned out that the formed condensation could look quite different from one time to another and a subjective division was made between “full” condensation and “moderate” condensation. Full condensation means that the amount was sufficient to completely obstruct the view across the whole window, while moderate condensation means that the condensation was visible, but more like haze or just at the lower part of the window, not covering the whole surface. Although most of the occasions with condensation were detected early morning, there were also some days when condensation was noted in the afternoon or evening, defined as “daytime” condensation. On several occasions during the second half of the tested period it was also noted that the surface temperature was low enough for the condensed water to freeze on the window surfaces. Since the visual appearance of the condensation layers is the important parameter, the occurrence was recorded by pictures taken with an ordinary camera.

The Research Approach

Once built, the Solar House will be used as research stand; the building (materials, structure, design) represents a set of un-changeable variables, while the hybrid thermal system management, for thermal comfort is subject of monitoring and optimization.

The steps to be followed are thus:

• Climatic data acquisition and refining;

• Energy input/output data acquisition and analysis, for the three systems: solar-thermal, heating pump and PV;

Thermal energy calculation, emphasizing the contribution of the renewables:

Подпись:+ EHP +) = Egas

By careful management of the solar-thermal and heating pump outputs the energy used from the back-up source has to be minimized towards zero.

If not feasible, for extreme winter temperatures (below -25oC) than the re-design of the solar-thermal system and of the heating pump must be considered focusing on the optimal ratio between the two heating sources.

• Electrical energy calculation: AEtotal = Eused — Ereceived = Eused — Epv

The Solar House will host the research laboratories with rather large energy consumers. Thus, regarding the power consumption, the data will give answers to the best use of the renewable energy in the field climatic conditions.

The use of power control management systems in reducing the global energy consumption represents a further development step.

The initial sizing, based on software use, of the solar-thermal and heating pump systems considered all the materials and design data. The research must also give answers to the questions related to the use of modelling software: the degree of reliability of the simulated data vs. the concrete measurements and the consequences at technical, functional and financial levels, when adapting the design to concrete climatic data.

2. Conclusion

The integrated use of solar-thermal, heating pump and solar PV systems can support the low energy building concept, for residences with an adequate architecture. The paper presents the application of this concept in the Solar House in the Centre Product Design for Sustainable Development, Transilvania University of Brasov. The Solar House acts as a research stand and allows design optimisation. The research opens opportunities for various combinations of the three renewable energy systems, according to the beneficiaries needs and adapted to specific climatic conditions.

References

[1] EU Parliament and Council, Directive COM(2008) 30 final.

[2] D. J. Treffers, et al., Energy Policy, 33 (2005) 1723 — 1743.

[3] B. de Meester, et. al, Building and Environment, (2008), doi:10.1016/j. buildenv.2008.01.004

[4] Baden, S., et. al Proceedings of 2006 ACEEE Summer Study on Energy Efficiency in Buildings, American Council for an Energy Efficient Economy, Washington DC, August 2006

[5] W. W. Clark, Larry Eisenberg, Utilities Policy, (2008), doi:10.1016/j. jup.2008.01.009

[6] V. Badescu, B. Sicre, Energy and Buildings, 35 (2008) 1085-1096

[7] Y. Wang, et al., Applied Energy, 83 (2006), 989 — 1003

[8] X. Xu, S. Van Dessel, Building and Environment, 43 (2008), 1785 — 1791

[9] F. Cuadros, et al., Energy and Buildings, 39 (2007), 96-104

[10] G. A. Florides, et al., Energy, 25(2000), 915-937

[11] I. Visa, A. Duta, Bulletin of the Transilvania University of Brasov, BRAMAT Proceedings (2007), CD

[12] I. Visa, et al. Proceedings of the 22nd European Photovoltaic Solar Energy Conference, Milano, (2007), CD

Ventilation and passive cooling

2.1. Day/night storage systems

As an alternative or in conjunction with direct night ventilation, we will consider two types of passive cooling systems based on thermal storage of the meteorological day/night oscillation that is carried by ventilation (fig. 2):

• The so-called air-soil heat exchanger, in which the air passes through an array of pipes buried under or next to the building, for the meteorological day/night oscillation to be dampened by charge/discharge in the soil. The daily heat wave propagation extends on approximately 15-20 cm around the pipes, so that latter can be arranged in a compact geometry, with inter-axial distance of approximately 50 cm, immediately under the building, and if necessary in multi­layer.

In the case of our study, we choose pipes with 12 cm diameter, for a specific flow of 100 m3/h per pipe (2.5 m/s). With such a configuration 10 m of pipes make it possible to reduce the

day/night amplitude to 41%, and 20 m of pipe to 17% (exponential damping), for a phase-shift which remains lower than an hour.

• The thermal phase-shifting device, in which the storage material is homogeneously distributed within the ventilating duct, in order to increase the heat-transfer surface and to decrease the penetration distance to thermal mass. Providing a homogeneous airflow and a good convective exchange, it then becomes possible to delay the day/night oscillation almost without dampening, for the night cooling peak to be available in the middle of the day.

In the case of our study we choose a storage material consisting of 13/16 mm diameter PVC tubes that are filled with water, piled up perpendicular to the airflow, with a 2 mm spacing between tubes. With a duct cross-section of 50 x 50 cm subject to a specific flow of 100 m3/h (0.39 m/s average interstitial velocity between tubes), the system enables an 8 h phase-shift with

1.6 m length, respectively a 12 h phase-shift with 2.4 m (linear phase-shifting), for a residual amplitude higher than 80%. This system hence not only differs from the buried pipes in terms of thermal behavior, but also in terms of an almost 10 times inferior storage volume.

First of these systems was subject of several case studies and theoretical analysis [2, 3], whereas second arises from a theoretical work that gave rise to recent lab developments [5]. They have both been object of theoretical developments, in particular in term of well validated analytical models [4, 5], which are used in this study.