ENERGY EFFICIENCY ELEMENTS IN HOMES ELECTRIC HEATING Nicolae VASILE Universitatea VALAHIA din Târgovişte, B-dul. Carol I 2, 130024, Târgovişte; nvasile54@gmail.com ICPE SA Bucureşti 3, Spl. Unirii 313, 030138, Bucureşti; nvasile@icpe.ro Alexandru-Gabriel GURGU Universitatea VALAHIA din Târgovişte, B-dul. Carol I 2, 130024, Târgovişte; gurgu_gabriel@yahoo.com Abstract. In this geopolitical and economic crisis, when we reconfiguring a new balance between holders of primary resources and technology we have a more current problem, the increasingly ideea the use of electricity to heat homes that is very clear. Although, due to the successive conversions, the price of electric energy is higher than the various forms of primary energy, it can get a cheaper heating service through various technical and economic methods taken by the beneficiaries of this services and / or energy suppliers. This paper presents several such methods and also practical results of the monitoring of demonstration projects in recent winters, in the specific climate in Bucharest. 1 Introduction The evolution of international energy mix targets the research to the renewable, especially wind and solar. The sources based on nuclear energy and energy obtained from waterfalls continues to grow. All these four forms of energy that attract investors specially lately come to increase the supply of electricity on the market in competition with traditional oil and gas supply. Bidders of oil and gas have different problems to exploit reserves that are in decline, of existence of military or political conflicts in the main production areas and with the excessive environmental pollution stages of production, transport and use. Electricity bidders have problems caused by the technical impossibilities. This form of energy must be consumed at the same time in that is produced. There are consumers that ensure constant consumption during the working day but there are problems with consumption in the night and weekend periods. Applications that can be used to balance day and night uses are electric cars that use energy to charge the batteries in the night time and electric heating of homes, which also involve consumption mainly nocturnal. For these reasons electricity suppliers are eager to offer different tariffs for day and night, making an interesting choice of a service based on electrical heating. 2 Technical constructive foundations Classical forms of heating, the district heating based on water and its circulation through pipes placed in the wall or outside wall (Fig. 1), lead an energy loss greater than the loss by the Joule effect in the current-carrying electrical conductors.
a) b) Fig 1: The placement of hot water pipes. a) outside wall, b) inside wall a) b) Fig 2: The placement of the heat sources. a) radiator placed near the wall; b) convector placed near the wall. When we talk about radiators or convector we do not have an indifference about the placement within the room since according to their position, a quantity of heat a larger or smaller, will transfer to the walls, which do not contribute to the thermal comfort of the room. The interest in terms of energy efficiency is that the entire amount of heat shall warms the bodies inside the living room, directly, for radiators, or indirectly through air movement, for convectors. In the case of the convectors or radiators based on hot water, we have the only way to place them near walls, due to inconveniences of rigid connection pipes through which the water circulation. (Fig 2). It is improper to use of flexible hoses, because, in such situations, we have a risk of failure or breacking. It is observed (Fig. 3) that an important part of the thermal spectrum falls near the wall which means a significant loss of heat. a)
Fig 3: The radiator's heat spectrum when it is placed near the wall: a) without sill, b) with sill If convectors are placed near the wall (Fig. 4a), we have a heat loss that is lesser than the case of radiator (Fig. 3a), because the additional circulation that brings heat from the wall and bring it into the useful space. In the case when there is a ledge above the heated body, for radiators (Fig. 3b) and respectively for converter (Fig. 4b), then the share of heat loss is even greater due to the negative effect brought by the windowsill, which unnecessarily increases the thermal spectrum. In case of the heated bodies freely in the rooms, (Fig 5) the case of convectors is more advantageous because the air fall brought by the forced circulation provided by the two sides of the convector. This option is provided only for practical electric convectors for theirs flexibility of their connections. 3 Theoretical and experimental results The numerical analysis of thermal spectra and structures set and also from the experimental results measured over several winters is found in the following comparative data: - Placing hot water pipes inside walls introduce a heat loss of about 23%, placing them outside a loss of about 7% and the power cord lose only about 0.2% of the energy transported; - The place of heaters near the wall leads to a heat loss of about 27% for radiators, is about 18% for convectors; a)
b) Fig 4: The thermal spectrum when we place convectors near the wall : a) without sill, b) with sill Existence of sills above the radiator introduces a further loss of about 14% to about 9% for radiators and convectors. Since these losses are multiplied successively, resulting an increased heat loss for bodies with water as heating agent placed near walls with 78%, for the radiators and pipes embedded in the walls, with sill, and with 65% for convectors in same conditions. If pipes are placed on the outside, the values are around 54% and 44%. If there is no sill, these values are reduced by 14% to 9% for convertors.since the gas price is currently only of 74% less than the price of electricity tariff differential night, there is a gross approximation of the costs of heating values for the two forms of heating. For electric version an additional advantage is the flexibility of setting that provides programming of the heating intervals only when it is necessary. Existence of usual intakes program is equivalent to a further saving of about 10% which makes it more attractive this option. a) b) Fig 5: Thermal spectrum cases: a) radiator placed on the wall; b) converter placed on the wall
The experimental results obtained in the conditions given in Table 1, are presented in Table 2. Table 1 The conditions under which the experimental data were obtained. Table 1 The conditions under which the experimental data were obtained. Heating modes: Configuration 1: Winter 2006-2007 - Air Conditioning: October, November, March, April. - Electric panel heater for home: December, January, February. - Rate undifferentiated day and night. Configuration 2: Winter 2007-2008 - Air Conditioning: October, November, March, April. - Electric panel heater for home: December, January, February. Day-night-differentiated tariffs. Configuration 3: Winter 2008 to 2009 - Ceramic heaters: October, November, March, April. - Electric panel heater for home: December, January, February. - Rate differentiate day and night. Configuration 4: Winter 2009 to 2010 - Ceramic heaters all winter. Technical data for house Ground floor: Living room with kitchen included - 30 sqm; Shower - 4mp. Floor: Bedroom 1-22 m; Bedroom 2-12 m; Bathroom - 9 m; Halls - 7 m. Attic: - 50 sqm. Scale: - 24 sqm. Technical Basement: - 16 sqm. Total: -174 sqm. The building is insulated on the outside 3cm thick extruded polystyrene. - Rate differentiate day and night. Configuration 5: Winter 2010 to 2011 - Ceramic heaters all winter. - Rate differentiate day and night. - Thermally insulated attic
4. Conclusions The theoretical evaluations and the experimental results show that electrical heating is an option that should be taken into seriously consideration in the current economic and ecological context. Future developments are expected to emphasize the arguments in favor of this type of heating. Acknowledgments The paper was supported within: - POSDRU Project 16 122, 2009-2011, entitled " Încurajarea antreprenoriatului pentru iniţierea de afaceri în domeniul Inginerie Electrică ; - POSDRU Project 77 497, PREDEX, 2010-2013, entitled "Pregătire doctorală de excelenţă pentru societatea cunoaşterii References [1] N. Vasile, F. M. Stan. Piaţa produselor şi tehnologiilor electrice, Editura Bibliotheca, Târgovişte, 2012 [2] N. Vasile, F.Tudorache, S. Făsui, M. Guteş. Energia-Probleme actuale, Raport de veghe Tehnologică, Editura Electra, Bucureşti, 2007 [3] A. G. Gurgu, N. Vasile. Energy Efficiency in Heating our Homes and the Future of the Electric Heaters", Electronica, Electrotehnica Automantica (EEA), ISSN 1582-5175, Nr. 3/ 2011; [4] W. Patterson. Electricitatea o industrie în schimbare, Editura AGIR şi Editura Academiei Române, Bucureşti, 2000. [5] D. Enescu, E.O. Vîrjoghe, O. Nedelcu. Numerical simulation of thermal field distribution in the cross section of a cylindrical. The scientific Bulletin of the Electrical Engineering Faculty, Targoviste, 2011 [6] R. Siegel, J. Hotwell. Thermal radiation heat trensfer. National Aeronautics and Space Administration, Washington, 1971. [8] M. Modest. Radiative heat trensfer. U.S.A. Academic Press, San Diego, California, 2003 [9] H. J. Lienhard IV, H. J. Lienhard V. A heat transfer textbook, Philogiston Press, Cambrige U.S.A, 2002 [10] G, Palani, K.Y. Kim. Joule heating and viscous dissipation effects on MHD flow plast a semiinfinite inclined plate with variable surface temperature,journal of Engineering Thermophysics, 2011 [11] T. Sameshima, Y. Kaneko, N.Andoh. Rapid joule heating of metal films used to crystallize silicon films, Applied Physics A Materials Science & Processing, 2002