Usage of the Wind Energy for Heating of the Energy-Efficient Buildings : Analysis of Possibilities

The paper analyzes and compares the energy demand for heating purpose of new buildings with different energy perfomance rates. Article studies global renewable energy sources innovations, statistics and scientific and engineering experience to ensure the building’s thermal energy needs, produced by transforming wind energy. Distribution of the potential of one renewable source – wind energy – during the year is similar to the energy necessary for the building heating, thus production of the heating energy from mechanic energy of the wind is chosen for further scientific investigations. Wind power plant, generating 2 kW of heat power, installed as a heating source for the analysed individual house, can cover from 40 to 76% annual heat needs of the building, subject to its energy-efficiency class, respectively 1.5 kW – from 31 to 68%, 1 kW – from 22 to 53%.


Introduction
gas, electricity and oil, Lithuania paid about 2,3 bill.Eur per year, while the whole Lithuanian state budget amounted 5,2 bill.Eur.
Building heating in Lithuania consumes 23% of the total consumption of primary energy (Lietuvos šilumos tiekėjų asociacija, 2010).As the consumed part is significant, big attention is paid to the designing and construction of the new energy-efficient buildings.At the moment, STR 2.05.01:2013 "Designing of the Energy-Efficiency of the Buildings" approved in Lithuania shall determine the requirements for energy-efficiency classes of all new buildings.Class of the energy-efficiencybuilding evaluation, including many aspects: _ Thermal characteristics of the building partitions, _ Building tightness that is the characteristic of the construction work quality very often, _ Usage efficiency of the non-renewable (primary -oil, natural gas, coal, peat) and renewable (wind, solar, aerothermal, geothermal, hydrothermal and ocean energy, hydropower, biomass, landfill gas, sewage treatment plant gas and biogas) energy sources that is related to the systems installed in the building, their automatic adjustment and energy saving at the same time.
_ This article shall analyse the opportunities to produce a part or all necessary heating energy in the building using the renewable sources in more detail.Very often this topic is evaluated sceptically, because of the thinking that energy needs of the buildings are conditionally big, and potential of the renewable sources is small.Therefore, analysis of the heating needs and possibilities meeting them using wind energy should decrease scepticism and form further tasks at issue, in order to develop implementation of the alternative energy sources both, in the sense of quantity and quality.120 m 2 living house designed according to the principles of the energy-efficiency has been chosen for the analysis (Fig. 1).Building has two floors; transparent partitions (windows and doors) shall make 19% of the area of all vertical partitions, and 64% of them is oriented to the South.A few calculation variants have been made -when the building partitions meet requirements of the energyefficiency class "B", "A", "A+" and "A++".Designed heat needs for the building heating have been calculated by evaluating the heat losses through the building partitions, heat need for the building mechanic ventilation and losses due to the outside air infiltration.In addition, the inflows from the people, electric lighting system and home electric appliances and due to the solar radiation have been evaluated.

Methods
In order to meet the air quality conditions regulated by the hygiene standards, the calculations shall analyse the building that has the mechanic ventilation system installed, although, according to the valid construction technical regulations, such system is not obligatory to all variants of the energy-efficiency classes analysed.
It is considered that average temperature in the rooms is +20°C (during working days for 9 hours and during weekends for 6 hours per day -+18°C, and during working days for 15 hours and during weekends for 18 hours per day -+21°C).Calculations have been made according to the climatology data of Kaunas city.
Calculation has been made according to STR 2.09.04:2008 "Capacity of the building heating system.Heat need for heating".Results of the calculations shall be provided in the table 1-3.
In this case, losses due to the external door opening/closing have not been evaluated, although, there is no doubt that such losses are conditioned by the building exploitation.It is more rational applying the passive solutions for compensation of the heat losses through the door -hood without

Results
Table 1 Heat  automatic quantitative regulation, i.e., such system that will not react to the cooled air of the premises due to the opened door and will not increase the amount of heat supplied to the room.When the door is opened, hood temperature for the specific area shall decrease, but this does not condition the general comfort of the building residents significantly.
After comparison of the building heat losses through the partitions and losses due to the ventilation system, the tendency that when energy-efficiency of the building increases, the percent distribution changes and is almost equal to the buildings having the biggest energy-efficiency (A++ class) (6578kWh/5453kWh -55%/45%).Thus, we can make the implication that bigger attention will be paid to the development of the ventilation system equipment of the building and management and automation of such systems in the future.
Heat inflow to the building due to the solar radiation can be analysed in more detail, as this free heat shall make the biggest part of the internal inflows -65-77% (for the analysed building).In order to design energy-efficient buildings, special attention shall be paid to the selection of the window width and glass pack construction.There is a need to decide objectively, what window size and construction are the most rational, as the heat energy through the windows is lost and got due to the solar radiation.
Calculations that are used when increasing the window width in the facades oriented to the different world sides shall be provided in the tables 4-8 (decreasing area of the outside walls appropriately).Months of heating season (October-April) shall be chosen for the analysis, i.e., when the outside temperature is less or equal to +10°C and the internal building releases do not compensate the heat losses.When performing the calculation, difference of the heat transfer coefficient of the window U W and wall, coefficient of the skip of the aggregate solar energy g and coefficient F c allowed evaluating the effect of the solar protection means.
Detail analysis has revealed that in some cases the building project can be changed by increasing the window areas

Table 3
Heat inflow to the building from the people, lighting and home electric appliances Q ig , kWh Month For all energyefficiency classes in such facades, where the solar radiation intensity is the biggest.In the buildings that coefficients of the heat transfer of the walls and windows shall meet the standard values of A+ and A++ classes of the buildings, it is rational to maximally increase the area of the windows in the Southern facade, as the windows oriented to the South during heating season shall pass the heat energy to the rooms more due to the effect of the solar radiation, compared to the heat losses (numbers in green boxes indicate reasonable solution, in yellow -close to reasonable solution result).Southern facade of

Table 4
Part of heat losses through the windows covered by the heating system (+) and solar radiation (-) in the building of energy-efficiency class B, % (Uw -1.6, g -0.53, Fc -0.8) Aim of the calculations provided above -to optimise the architectural solutions of the building and to determine needs of the heating system (Fig. 2) for the energy-efficient buildings and rational capacity of the alternative heat source of such buildings.In addition, calculations shall allow checking, if the wind energy can guarantee the heat quantity (or its part) necessary for the building heating.

Calculations
performed shall indicate that average need of the moment energy for heating is from 5 kW (for typical family house of energy-efficiency class B) to approx. 2 kW (for typical family house of energy-efficiency class A++).In addition, due to variability of the wind energy (as any other alternative energy source), a possibility to produce only part of energy necessary for the building heating by transforming the wind energy shall be analysed, as in any case the source guaranteeing the appropriate heating energy supply should be installed in the building in parallel (biofuel, gas fuel boiler; unit of the centralized heating networks or electric heating system, using electric power from the centralized networks).If the wind power plant, generating 2 kW of heat power, is installed for the analysed case, it would be possible to cover from 40 to 76% annual heat needs of the building, subject to its energyefficiency class, respectively 1.5 kW -from 31 to 68%, 1 kW -from 22 to 53%.
Wind energy application for the building heating has been chosen due to a few reasons: 1 distribution of the wind energy potential during a year is closer to the heating needs of the building, compared to the solar radiation energy used widely -it is due to the fact that wind power is directly dependent on the wind velocity and air density (Adomavičius V., 2013)average wind velocity is bigger in winter than in summer in Lithuania (Adomavičius V., 2011) (Fig. 3) and density of the cold air is bigger than warm air; 3 during exploitation wind energy does not release pollution (f.e.like during combustion of biofuel) to the environment.Fig. 3 shall present average values of the wind speed (Galvonaitė A., 2013), they cannot be used when making implications on the wind energy potential in the specific land plot.For this purpose, annual measurements of the wind speed in the land plot should be performed (Marčiukaitis M., 2009).Theoretically, it is possible to model speeds of the wind in the specific land plot and surrounding territories, but network of the stations for the wind speed measurement is conditionally small (in Lithuania wind speed is being measured in 18 stations in the height of 10 m) and work extent of such modelling would be unjustified big.
In order to perform primary evaluation of the system "wind power plant -heat generator", the calculations have been performed; they have revealed that in case of average wind speed of 4 m/s (for example, it is the average annual wind speed in Lithuania), in order to generate 1 kW of heating energy, three-vane wind turbine with horizontal axis of diameter 8.22 m that power factor is cp=0.49shall be needed (Kytra S., 2006).
The analyzed living house, which is equipped with wind turbine of 1 kW power and which can manufactured from 3433 kWh (A + + energy efficiency class of the building) to 4241 kWh ("B" energy efficiency class of the building) thermal energy, protects the atmosphere of not throwing in the environment up to 856 kg of greenhouse CO 2 gas (as compared to natural gas combustion for heating), which is the CO 2 "footprint" equivalent to about 4000 km journey by car.CO2 treatment is relevant because it accounts for about 95% of the total greenhouse gas structure (Konstantinavičiūtė I., 2012).

Discussion
Principles of the heat production directly from the mechanic wind energy have been already described in the previous works of the engineers and scientists.In most cases equipment of such type is based on the usage of the volume hydraulic machines (pumps), where the kinetic energy of the wind wheel axis is transferred to the potential fluid energy, and due to the artificial obstacle and friction to it the fluid potential energy is transferred to the heat energy (Maegaard P., 2013).In 1960 V. V. Blasutta and J. F. Hedge ("Fluid pressure energy translating device", USA) and in 1981 -W.J. Grenier ("Fluid friction heater", USA) have described and patented the device of such type.In 1983 J. E. Knecht ("Wind driven heating system", USA) and in 1986 H. W. Haslach ("Wind turbine heat generating apparatus", USA) have patented devices of the analogous type that suggested using heat generated due to the fluid friction and have used the wind wheel as the source of the primary energy.We can state that such interest in the alternative energy in the eight-ninth decade of XX century could be conditioned by the world oil crisis of 1973, when big part of people has felt significant shortage of the fossil fuel.
In addition, input of the Danish scientists and technical enthusiasts to the development of the wind power plants producing heat can be noticed.Nowadays and in the eight decade of the last century Denmark was the leader in the area of the wind energy usage.In 1973 engineers S. S. Kofoed and R. Matzen from the Institute of the Agriculture Engineering (Taastrup, Denmark) has created, tested and developed the wind power plant "Mark" (version "Mark I" and "Mark II"), producing heat energy from the wind mechanic energy.Later, H. H. Ekner has created the wind power plant "Calorius" that has gained an attention from the scientists as well -capacity and noise level tests have been performed for the power plant of such construction and in 1993-2000 Danish company "Westrup" has installed and started 34 power plants "Calorius" (according to 2012 data, 17 of them are still used).Although a lot of scientists and engineers see a lot of benefits of the wind power plants producing heat, but power plants of such type has not been used widely in practice.We can make assumptions that there was a lack of subsidies from the national funds, provided to the production of the electricity from the wind energy.
In Lithuania possibilities to use the wind energy have been explored in more detail and various publications prepared in A. Stulginskis University (former University of Agriculture of Lithuania).Firstly, instalment of the equipment for using the wind energy has been topical in the localities distant from the centralized networks, thus the scientists of this university have paid bigger attention to this topic.In 2001 in the Institute of the Agriculture Engineering of the Lithuanian Agriculture University A. Gulbinas has prepared and defended doctor's dissertation on the topic "Investigation of the effective usage of the wind energy equipment in the agriculture".In addition, in 2011 A. Kavolynas has defended the doctor's dissertation in A. Stulginskis University on the topic "Solar and wind energy usage for meeting the heat needs of the buildings in the rural localities", however, in this work the author has paid more attention to the investigation of usage of the solar energy and its accumulation, and the topic of wind energy has been analysed according to the works of other authors.
A lot of international organizations work in the area of the wind energy usage -

Fig. 1
Fig. 1 Building visualizationupper: South Western façade; lower: North Eastern facade (source -www.haus.lt,project author -arch.A. Zaniauskas) Fig. 2 Average instantaneous thermal power demand for heating of the analysed buildingof different energy-efficiency classes during the year

Table 6
Global Wind Energy Council (GWEC) represents over 70 countries; European Wind Energy Association (EWEA), established in 1982 in Belgium and having 600 members from almost 60 countries; World Wind Energy Association (WWEA) -established in Germany and having 95 members.Lithuanian Wind Energy Association (LWEA), established in 2005, is the member of the international organizations as well.LWEA pays the biggest attention to the development of the electricity production in the wind power stations.