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Home , Autonomous building, Energy neutral design

Towards an autonomous dwelling How to create a more constant to limit storage demand

Patricia Knaap Student nr.: 4011015 e-mail: [email protected]

Delft University of Technology Faculty of Architectural – Studio 12

May 2014

ABSTRACT of these sources for generating results in This paper is a summary of the research that has heavy pollution. Many new dwellings are all- been conducted on energy and the electric so that gas is not required anymore for possibilities to produce the electricity from heating and cooking, but this results in a higher renewable sources on a small scale in such a way electricity demand. that the dependency of the grid or electricity Although sources can provide a storage demand is reduced. significant amount of electricity in a much more It shortly describes the current situation of energy sustainable way, the largest part of electricity still consumption, the energy demand of a Dutch free comes from natural resources. A reason why standing dwelling and how this demand can be renewable energy is not used very much yet is reduced by smart architectural design choices. because there is not a continuous production. The main focus in this paper is how electricity can Where natural resources are available at any be produced by a dwelling by using renewable time, the availability of renewable energy sources resources and how this can be done as efficient is variable and therefore it results in peak as possible to limit the need for electricity storage. productions of electricity. This means that there is Therefore the electricity production with PV cells a bigger mismatch between electricity production and wind turbines is researched. For PV cells and consumption with electricity produced from calculations have been made to compare the renewable sources than from natural resources electricity production and storage demand for which has to be solved by storing electricity. different orientations and slopes. Wind energy is Storage of electricity is very difficult and has very researched for its possibility to provide electricity low efficiencies. This is the reason why currently when PV cells are not sufficient in order to limit an exchange of electricity is established between electricity storage even more. At last, electricity producing and the national combinations of , wind energy and grid. But when all buildings become all- required storage capacity are compared. electric there will be enormous peaks in energy production and consumption which are not Key-words: , electricity production, occurring simultaneously and cannot be solved all-electric, renewable electricity, electricity storage, with electricity exchange and storage. optimizing solar energy production, wind energy, The objective of this paper is to seek for a way to energy autonomous create a more stable energy supply in order to reduce the dependency of the grid, for an energy 1. INTRODUCTION neutral dwelling throughout the year by making sustainably is becoming more and more optimal use of the environment and its climate important since natural resources such as , oil and by integrating and are depleting rapidly and the use technologies in architecture.

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This paper will first quickly describe the current is divided more or less equal throughout the year situation of energy consumption and the energy and only depends on the demand of the user. demand of a Dutch dwelling, followed by possible (www.gaslicht.com) architectural to reduce the energy demand. After that, possibilities to produce electricity on a small scale will be described as as ways to store this electricity. Lastly, we will investigate how we can optimize the electricity production to the consumption in order to limit electricity storage.

2. CURRENT SITUATION Figure 2: Energy use of households, 1990-2012 The total energy consumption of the (www.compendiumvoordeleefomgeving.nl) has been increasing in the period between 1990 and 2012. In 2012 the consumption increased The electricity production in The Netherlands in with 0,7% compared to 2011. This was mainly 2012 was for 53 per cent a result of burning gas. the result of a 6% increase of energy consumption Electricity can also be provided by burning coal. of households due to the cold winter which In 2012, 81 per cent of the electricity production resulted in more heating and therefore a higher came from fossil . This is a reduction 12 per energy demand. cent compared to 1998 when over 90 per cent of (www.compendiumvoordeleefomgeving.nl) the electricity was produced with fossil fuels. (Wezel & Kloots)

Figure 1: Energy use per sector (www.compendiumvoordeleefomgeving.nl)

ENERGY USE IN DWELLINGS Dutch dwellings require both thermal and . is used for heating, warm tap water and cooking. Electrical Figure 3: Electricity production divided per source energy is used for lighting, ventilation, cooling (Wezel & Kloots) and electrical appliances. The electricity production from renewable sources The most commonly used energy source for increases slowly. The share of renewable providing heating is gas. How much gas is electricity production in 1998 was 2,5 per cent of consumed mainly depends on the weather the total and increased to 12 per cent in 2012. conditions of autumn and winter since this (Wezel & Kloots) determines the heating demand. When it is colder The most important sources for renewable energy than average, there is a higher heating demand are wind energy (18,4% of which 15,5% on which means an increase of the gas consumption. shore), burning in waste burning plants Gas is also used for providing warm tap water (15,5%), biofuels for transport (14,1%), wood and for cooking. The amount of gas used for this burning in dwellings (13,1%) and burning

2 biomass in electricity plants (11,6%). This counts used in the winter months; October to April. for over 70 per cent of the energy consumption (Essent, 2014) However, the exact distribution of from renewable resources. Solar energy ( and gas used for heating over the year depends on electricity) is only 2% of the energy consumption the weather. Since the outside temperature is one from renewable resources. (CBS, 2013, pp. 17, of the most important factors in the demand for 18) heating of a dwelling, degree-days can be used to determine the average course of heating demand The following graph shows the electricity and gas throughout one year. consumption of Dutch households since 2000.

There is a significant decrease of gas DEGREE-DAYS consumption which is mainly the result of a Degree-days look at the difference between the smaller heating demand due to high-efficiency outside temperature and a reference temperature. heating systems and better insulation of dwellings. This reference temperature is set at the (EnergieNederland, p. 55) temperature where no heating is required, usually 18 degrees Celsius. The following graph shows how the degree-days are distributed over the one year. (TUDelft, 2011, pp. 49, 50)

Figure 4: Average consumption of electricity and gas for Dutch households (EnergieNederland, p. 56)

The electricity consumption has increased from 1988 until 2008 as a result of the introduction of electrical appliances such as the refrigerator and Figure 5: Degree days, based on average temperatures dish washer. Because of a decreasing amount of in the Netherlands. persons per household, the improved efficiency of (TUDelft, 2011, p. 50) appliances and a stop in the growth of the penetration rate of electrical appliances, the The graph of the degree-days is used to electricity consumption stabilised after 2008. determine the average course of gas use for However, an increase of electricity consumption is heating throughout one year as can be seen in occurring again as a result of the increasing total figure 6. The surface under the heating curve amount of households and their growing represents the total gas use for one year, in this electricity use. (EnergieNederland, p. 55) case 1.711 m3. In the Netherlands, a family of four person uses 3. ENERGY DEMAND on average 4.580 kWh electricity per year. This is A four person Dutch household, living in a free practically evenly distributed over one year. standing dwelling uses on average is 2.220 m3 In the graph, the amounts of gas and electricity gas per year. Almost 20 per cent (444 m3) of this have been converted into mega joules in order to is used for warm tap water in the kitchen and compare the required energy. bathroom. 65 m3 of the total gas use is used for cooking and the remaining 1.711 m3 is used for heating. (www.milieucentraal.nl) From the gas used for heating, approximately 85 per cent is

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small windows in the north façade (the cold side), only for natural day lighting purposes. On the south façade, bigger windows are made but with an overhang which blocks the high sun in summer and allows the low sun in winter to enter the building and give natural heating. Other design options which are less often used but can also influence the energy use of a dwelling is the shape of the building. The smaller the façade surface is compared to the floor plan, Figure 6: Energy consumption of a free standing the smaller the surface of through dwelling (based on own calculations with numbers the façade is. Also the spatial organisation of a mentioned above) dwelling influences the energy use. By looking at

the time and amount of heating demand of rooms 4. ENERGY REDUCTION and adjusting this to the orientation, the energy A first step in limiting the electricity storage or use for heating can be limited. In the Netherlands exchange with the grid is to reduce the energy the north side is the cold side of the building due demand of a dwelling so that in general less to very little solar so by placing rooms energy is required. Reducing the energy demand with a low heating demand or rooms which can be done by already making smart design produce heat such as the kitchen or bathroom on choices. Passive are very good examples the north side less heating is required than when of dwellings which have been designed in such a for example a living room is placed there. Rooms way that only a very small amount of energy is with a heating demand in the morning can best required. The main focus in passive building be placed on the east side of the building while design is to limit the heat transfer through the rooms with a heating demand in the afternoon façade. Therefore the materialisation and can better be placed on the west due to the detailing of the façade are very important design position of the sun and therefore the natural aspects. In order to limit the heat transfer through heating effect. In summer however, sun shading is the façade, the walls have to be very well necessary to prevent overheating of the building. insulated. In most passive houses the outside walls Passive houses mostly use natural ventilation, are made of a timber framework with a thick sometimes with mechanical suction so that heat insulation package and covered with either wood recovery is possible. This is an active solution or stone on the outside. The detailing has to be which makes it possible to use for air tight so that there is no unwanted air flow heating up water or air so that less artificial between inside and outside. heating is necessary. In general, windows are less insulating than a Very often a with low temperature closed façade. This would be a reason to make heating is applied to supply the remaining heating as little windows as possible in a . demand. How this works and what its effect is will However, natural day lighting and a view to the be discussed later in this paper. outside are very important so there has to be (Lengen, 2008) (www.actiefbouwen.eu; found a balance between the amount of day light www.frankearchitekten.nl; www.invent.nl; access and heat loss through windows. On the www.studionoa.eu) other hand, especially in winter solar radiation through windows can give natural heating and 5. ALL-ELECTRIC therefore result in less artificial heating. In summer Passive design strategies can result in less energy it can give too much solar gain and therefore it consumption but there will always be an energy should be blocked. A possible solution for this, demand remaining. In order to limit the use of often used in passive houses is to make very few fossil fuels, new dwellings are designed as all-

4 electric buildings. This means that they do not uses solar radiation to heat up water. However require gas anymore but they use electricity for since there is not always enough solar radiation providing both electrical and thermal energy. due to weather conditions, using a solar collector will not always be sufficient. Providing conventional heating with electricity requires a lot of power because the water of these EFFECT OF A HEAT PUMP heating systems has to be 80-90 degrees Celsius In order to determine the effect of a heat pump in order to achieve the desired . on the energy demand, we can make a Therefore, in new all-electric buildings the aim is calculation with the coefficient of performance to apply low-temperature heating. For this, the (COP). water has to be heated to only 25-55 degrees The average gas use for heating in a free Celsius and therefore requires much less standing dwelling is 1.711 m3 (54.153 MJ). The electricity. (www.milieucentraal.nl) average COP for heating with heat pumps is 4,5 A lower water temperature is only possible if there which means that 42.119 MJ can come from the is a larger surface to provide heating. Therefore stored heat in the ground and only 12.034 MJ floor or wall heating is used instead of has to be provided by the power grid or the own conventional radiators. An extra advantage is that electricity production. the heat is more evenly divided over the so For warm tap water, 444 m3 of gas is used that the room temperature can even be 2 degrees (14.053 MJ). Because the water temperature for lower than with heating while achieving tap water has to be higher than for heating, the the same of comfort. (www.milieucentraal.nl) efficiency of the heat pump is in this case lower. A heat pump or collective heating is usually used Therefore for warm tap water, an average COP of to provide warm water for low-temperature 3 is used. This means that 9.368 MJ can be taken heating. A heat pump stores the excessive heat from stored heat in the ground and 4.684 MJ has from summer in ground layers which can be to be provided by the grid. In total over one year, pumped up in winter to provide heating. In winter, this means that the required electricity from the the “waste” product of the is cold grid for warm tap water and heating can be water, which can be stored in ground layers so reduced from 68.206 MJ to 16.718 MJ by that in summer this can be used for cooling. applying a heat pump. A heat pump reduces the (www.energieverdieners.nl) It is important that the electricity demand significantly, but the installation heat and cold source are in balance. Since the itself also requires electricity, approximately 1500 two sources charge and discharge each other a kWh (5.400 MJ), which is added to the total misbalance results in exhaustion of one source electricity use. (www.warmtepomp-info.nl) which means the system cannot properly anymore. (www.geveke-klimaattechniek.nl)

The lower the water temperature has to be, the higher the efficiency of the heat pump is and thus the less energy it requires. With an electric heat pump the water temperature should stay below 35 degrees Celsius to make it an efficient system. In addition to that it is also important that the building is well insulated so that heat loss through the façade is limited. (www.milieucentraal.nl) Figure 7: Electricity consumption of an all-electric free For providing warm tap water, electrical standing dwelling (based on own calculations) are most often used. It is also possible to provide warm tap water by using a solar collector which

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6. SOLAR ENERGY building integrated photo voltaic (BIPV). It makes In order to not use any fossil fuels anymore for it possible to integrate the PV cells in the building providing electricity to dwellings, the electricity and thereby save building materials. BIPV’s can should be produced from renewable sources such be made in different colours and transparencies as wind, water or sun and not from burning gas and can be integrated in different types of glass. or coal. (www.solarcompany.be) When producing this electricity by the dwelling itself, we are looking at small scale applications with the highest possible yield in order to make the system sufficient. For small scale electricity production, only wind and sun are sources which can provide sufficient amounts of electricity to make the application feasible. For wind energy, small scale wind turbines can be applied. For solar energy, PV cells and solar collectors are available.

Figure 9: Building integrated photovoltaic (www.sapa- PHOTOVOLTAIC PANEL TYPES solar.com) There are three main types of PV panels available for commercial use; polycrystalline panels, Thin-film PV cells have already been used for a monocrystalline panels and thin-film panels. long time in small devices such as calculators, but are relatively new in large scale projects such buildings. The thin-film PV cells have a lower efficiency than mono- and polycrystalline PV cells. A big advantage however is that they can much

better convert indirect solar radiation into Figure 8: Different types of PV cells Left: monocrystalline PV cell, middle: polycrystalline PV electricity. Therefore they are very suitable in cell, right: old polycrystalline PV cell temperate climates and for positions which are (www.allesoverzonnepanelen.nl) not optimally radiated, such as the west and east orientation and steep tilted or flat surfaces. Monocrystalline PV panels have a higher Another advantage of thin-film PV cells is that the efficiency than polycrystalline panels and they are efficiency stays high when the ambient more sensitive for direct sunlight. Therefore they temperature is high. (www.passiefhuisbouwer.nl) are very suitable for south oriented small roofs. In general, PV cells can produce the most Polycrystalline panels however are more sensitive electricity when the ambient temperature is 25 for diffuse light. Therefore they are more suitable degrees. Higher or lower temperatures result in in moderate climates where there are relatively a lower efficiencies. For crystalline panels this is - lot of clouds and therefore a lot of diffuse light. 0,5% per degree, for thin-film panels only -0,2%. Also polycrystalline panels are a little bit cheaper (www.solartown.com) and therefore often applied on bigger roofs. Also, thin-film PV cells are approximately 30% (www.allesoverzonnepanelen.nl) The efficiency of cheaper than crystalline PV cells. both the monocrystalline and polychrystalline PV In the Netherlands, thin-film PV panels can yield panels decreases when the ambient temperature approximately 7 per cent more electricity per is high or when there is not much solar radiation. installed power (in Watt peak) than crystalline (zonneenergie.eu) panels. This is a result of the higher efficiency with indirect light and in high temperatures. Nowadays it is also possible to integrate mono- (www.passiefhuisbouwer.nl) or polycrystalline PV cells in glass. This is called

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an extra addition at the end. When applying PV cells, nowadays the most important thing is to produce as much electricity as possible in one year. In the Netherlands the most optimal placement of PV cells therefore is south oriented and with a 35 degree angle. In this position the highest intensity of the sun is most optimally caught by the PV cells, thereby producing the most electricity compared to other orientations and angles. (www.passiefhuisbouwer.nl) Figure 10: Thin-film PV cells(www.ge-energy.com) The highest production peak will in this case

occur around 12 am-1 pm. Before and after this A new technology in the field of thin-film PV moment the intensity of the sun is lower and thus panels is the CIGS panel. This stands for Copper- less electricity is produced. Placing PV cells on indium-gallium-selenite. These panels have a other orientations or with another angle will result higher efficiency than the standard thin-film in a lower annual yield since the total solar panels and also have a good performance with radiation in these positions is lower. diffuse light. A disadvantage is that these panels The problem with placing the PV cells on the are still very expensive. south orientation is that the highest electricity (www.allesoverzonnepanelen.nl) production occurs at the time of the day when The choice of which PV system fits best in a there is only a small electricity demand. The building design depends on many factors such as highest electricity demand occurs in the late the surface which can be used, the amount of afternoon and evening, when very little to no radiation the surface will receive, the temperatures electricity can be produced with south oriented PV which will be reached, the desired yield and the cells. This results in a lot of electricity exchange aesthetics. Therefore in every building design a with the national power grid or a high demand for comparison of pros and cons per system should electricity storage in order to guarantee a be made to find the best solution for that constant electricity supply. particular design. (www.allesoverzonnepanelen.nl)

CURRENT APPLICATION OF PV CELLS Currently PV cells are mostly applied on existing buildings or in the last phase of a new-build design. This means that in most cases, the PV cells are not part of the building design process but are

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SOLAR IRRADIATION VERSUS ORIENTATION Figure 12 shows the total amount of solar irradiation for one representative day of each month on the façade of four different orientations and on a horizontal surface.

Figure 14: Path of the sun during one day in relation to orientation (own image)

ENERGY STORAGE ENERGY NEUTRAL VS. ENERGY AUTONOMOUS Besides becoming all-electric, also energy neutral building design is becoming more important when aiming to save fossil fuels. Energy neutral means that in a time period of one year, the amount of energy which is produced is equal to the amount of energy which is consumed. With an energy Figure 12: Solar irradiation per orientation, 15th day of neutral design, the balance between energy the month (Linden, 2005) production by the dwelling itself and consumption over one year is zero, but it is still possible to have There are two factors which are important to an exchange with the national power grid. At notice when looking at this graph. Firstly the moments when there is a surplus of electricity angle of the sun towards the earth. In summer the production it can be provided to the grid, whereas angle is very high so the more horizontal the at moments of a shortage, electricity can be taken surface, the higher the intensity of the solar from the grid. (AgentschapNL, 2012) irradiation which strikes the surface. In winter A measure for the energy efficiency of a building however, the angle between the sun and the earth is the energy performance coefficient (EPC). The is very small which means that the more vertical lower this value is, the more energy efficient the the surface, the higher the intensity of the solar building is. A negative EPC value means that over irradiation which strikes the surface. one year the total production of electricity is higher than the consumption. (www.rockwool.nl) The difference between energy neutral and energy autonomous is that with an energy autonomous

Figure 13: Angle of the sun and the best possible slope design, there is no exchange with the grid so it is of the roof/facade (own image) completely self-sufficient. The energy which is produced but not used directly will have to be The second factor is the time of the year versus stored somewhere in the building to provide the orientation. In summer a day has many sun energy at times when the consumption is higher hours which means that the overall solar than the production. (AgentschapNL, 2012) irradiation in these months is higher. In these months the highest intensities are reached on a Currently there are no real autonomous dwellings horizontal surface and the east and west facade. in the Netherlands yet because of the problem of In winter there are very few sun hours, which electricity storage. There are some dwellings means that the overall solar irradiation is already designed according to the passive or much lower and the highest intensity will be energy neutral design methods which can reached on the south façade. disconnect from the grid once there is a good storage solution. Compared to passive or energy

8 neutral building , the autonomous building one week. These are lithium-ion batteries which designs have more PV panels and solar collectors have a storage capacity for approximately one to make sure that they provide enough electricity week. One lithium-ion battery can store only a and thermal energy for the entire year. small amount of electricity. Therefore for home storage, many batteries are combined into a When a dwelling produces its own electricity with module. Several modules can be connected to for example PV cells or a windmill, often there will each other to provide the required storage be a misbalance between supply and demand of capacity. (tweakers.net) (Panasonic) electricity. Figure 15 shows besides the electricity consumption also the electricity production of PV cells at that day. Because the electricity is only produced at specific moments of the day and in different quantities it does not match with the peak load of the electricity use.

Figure 16: Panasonic home system (Panasonic)

Figure 15: Electricity production and consumption on a typical summer day in Germany (family of 4 persons) (SMA)

The mismatch between electricity production and consumption asks for a storage solution in order to always be able to provide electricity. The excess Figure 17: Panasonic smart energy storage system electricity can then be stored for moments when (Panasonic) the production is not sufficient. However, storage of electricity is very difficult. Therefore mostly an When looking at the production and consumption electricity exchange is established with the of electricity over time, there are several ways to (national) power grid. This means that when there apply electricity storage. The options which will be is an overproduction of electricity, it is supplied to explored now are all 100% energy autonomous. the power grid so that other buildings can use it. When there is a shortage of the own production, YEAR-STORAGE electricity will be taken from the power grid. By The first option is to look at the yearly production placing a special meter in the meter cupboard, it and consumption. In this case the complete is possible to measure the amount of electricity overproduction of summer months has to be taken from and supplied to the grid. (Consuwijzer) stored in order to be able to provide the electricity shortage in the winter months. Since storage Even though electricity exchange with the grid is means that the electricity is converted into another the most common “storage” method, it is possible form of energy, there are losses, approximately to use small electricity storage devices for a 10% per conversion. When producing the dwelling. The most suitable solution is a battery. electricity with PV cells, the surface of the PV cells There are batteries available for household use should be big enough to produce 120% of the which can provide enough electricity storage for electricity consumption so that electricity losses

9 due to storage are taken into account. Figure 18 WEEK-STORAGE and 19 show a comparison of an all-electric Another option for electricity storage is to look at dwelling with and without a heat pump and the the week consumption and production of difference in required surface of PV cells and electricity. required electricity storage. In the graph, the In this case the week with the highest consumption surface under the production line (blue) has to be and smallest production determines the maximal 1,2 times the surface under de consumption line required storage capacity. In the Netherlands, this (orange). Further on in this paper the comparison is the last week of December. Also for this a will be extended with electricity produced on comparison has been made for an all-electric differently positioned surfaces and conclusions will dwelling with and without a heat pump and the be drawn from this. difference in required surface of PV cells and required electricity storage. In this case we assume that the consumption and production of electricity are not occurring simultaneously, therefore the result is the maximum required storage capacity. In a real situation it will always be less because a part of the consumption and production will occur at the same time. The required surface of PV is much larger than when looking at storage for the entire year because when there is only very little solar irradiation in winter, it still has to supply the complete electricity Electricity shortage 30838 MJ demand of that week whereas with the year- Electricity production (to be stored) 37606 MJ situation, stored electricity is used in these 2 Surface PV cells (S 45˚) 148 m situations. In the graph, the line of the production Amount of batteries (100kWh) 105 (blue) always has to be at least 20% above the Figure 18: Electricity consumption [without heat pump] consumption line (orange). and production with PV cells [south oriented] (own image)

Electricity consumption 2728 MJ Electricity production (to be stored) 3273 MJ

Surface PV cells (S 45˚) 883 m2 Electricity shortage 10886 MJ Amount of batteries (6,8kWh) 134 Electricity production (to be stored) 13182MJ Amount of batteries (100kWh) 10 Surface PV cells (S 45˚) 68 m2 Figure 20: Electricity consumption [without heat pump] Amount of batteries (100kWh) 37 and production with PV cells [south oriented] (own Figure 19: Electricity consumption [with heat pump] image) and production with PV cells [south oriented] (own image)

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The electricity consumption of a household in one year is known; 40.671MJ. Together with the total annual electricity production for a particular orientation and slope, the required surface of PV cells is calculated.

annual required electricity surface production PV cells MJ/m2 m2 horizontal 540 76 Electricity consumption 1018 MJ South 45˚ 632 65 Electricity production (to be stored) 1224 MJ South 90˚ 466 88 2 Surface PV cells (S 45˚) 330 m South-East|South-West 45˚ 599 68 Amount of batteries (6,8kWh) 50 East|West 45˚ 480 85 Amount of batteries (100kWh) 4 East|West 90˚ 340 120 Figure 21: Electricity consumption [with heat pump] Figure 23: Required surface of PV-cells to meet the and production with PV cells [south oriented] (own electricity demand image) The results of the calculations have been put in OPTIMISATION graphs (see figure 24 and appendix 3). When In order to limit the dependency of the power grid looking at the graphs, we can define three zones. or limit the demand for electricity storage, The first zone is where the production and electricity should be produced as much at the consumption of electricity are occurring time of demand as possible. For this, several simultaneously. The larger this surface is, the calculations have been made on electricity better because then there is no storage required. production for different orientations and slopes. The second zone is when there is an Based on measurements of the global irradiation overproduction of electricity with PV cells. The on 2 days a month, the distribution of global third zone is the shortage of electricity production irradiation throughout one year is determined. compared to the consumption at that moment. In From this, the electricity production of PV cells can order to be energy neutral, the surface of the be calculated by using the efficiency of the PV overproduction should be the same as from the cells (for this calculation an efficiency of 15% is electricity shortage. For energy autonomous, the used). This results in a graph of the electricity surface of the overproduction should be 120% of production for one year for different orientations the electricity shortage so that conversion losses and slopes. Also the total electricity production for due to storage are included. one year can be derived from this calculation.

Figure 24: Electricity consumption and production (own Figure 22: Electricity production (W/m2) per year for image) different orientations and slopes(based on measurements of the KNMI) (Velds, pp. 115-117)

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In order to compare the results of different annual electricity consumption including the electricity positions of PV cells, we look at the required losses of storage. However, PV cells on a south surface, the amount of electricity which has to be oriented façade (90˚) requires a little bit larger surface stored and thus how many batteries are needed but then less storage is needed because more electricity is produced at the same time as the electricity and how many weeks of the year storage is consumption. necessary. Another factor which is included is the For the second calculation, the surface for all costs. For a PV system, a price of €200,-/m2 is orientations and slopes was the same in order to used which is for the PV panel including mounting compare the required storage and position of PV cells. and wiring. (Saman) Here the 45˚ south oriented PV cells are most optimal The prices given for lithium-ion batteries are very when looking at the smallest amount of storage different per source, among other reasons required, so in this case the electricity production and because the prices change very quickly in time. consumption occur most simultaneously. However, From several sources an assumption has been there is a very large overproduction which is not used / not necessary. The south façade requires one battery made. For the calculation a price of €500,-/kWh more, but then there is already much less unused is used. (www.evsroll.com; www.forbes.com; overproduction. www.powertechsystems.eu) In order to not use yearly storage a PV surface (south 45˚) of 330 m2 is required. Then only storage is From the calculations, the conclusion can be drawn required for the misbalance of electricity production that when looking at the annual electricity production, and consumption during the day. In this case however PV cells south oriented with a slope of 45 degrees there will also be a large overproduction during require the smallest total surface in order to fulfil the summer which will not be used by the dwelling itself.

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7. WIND ENERGY VISIONAIR WIND TUBRINE For domestic use, small wind turbines are This vertical axis has a height of 5,2 available. They use the same working principles meter and a width of 3,2 meter. The swept area is as large wind turbines but the maximum height of 16,6 square meter. With a wind speed higher the turbine is 15 meters. This directly results in a than 4 m/s it can generate electricity. When the much lower electricity production since the wind speed is 5,5 m/s it can reach an annual dimensions of the turbine are much smaller and electricity production of 3600 kWh. (UGE) This the wind speed is much lower at this position. wind turbine costs approximately €20.000,- Small wind turbines are available as both (ultrasolarandwind.com) horizontal and vertical axis turbines. The produced electricity can be stored in internal batteries and then converted to usable alternating current. It is also possible to connect the turbine with the national power grid and exchange electricity. In the built environment, horizontal axis turbines should be as free standing as possible in order to catch as much wind as possible and to reach the Figure 28: VisionAir wind turbine; power output (kW) highest possible efficiency. Vertical axis turbines plotted against the wind speed (m/s) (UGE) however can use a wind tunnel effect created by buildings to reach a higher efficiency of electricity ENERGY BALL production. (Yanovshtchinsky, Huijbers, & The energy ball is a ball shaped wind turbine Dobbelsteen, 2012, p. 236) which has several advantages compared to a traditional wind turbine. Because of the aerodynamic design of the ball, a higher DONQI URBAN WIND MILL efficiency can be achieved for generating From a wind speed of 2,9 m/s this horizontal electricity per air flowing surface. wind turbine can generate electricity. It has a Other advantages are the turbine does not width of 1,5 meter and a swept area of 1,77 produce any noise such as a standard wind square meter. With a wind speed of 5,5 m/s it turbine and they have a more aesthetic shape and can reach an annual electricity production of appearance, therefore making them fit better in a 2300 kWh. (donQi) The price for this type of built environment. The wind turbine can be windmill is approximately €4.000,- excluding connected to the electricity grid or function off- installation costs (approx. €800,-). (donQi) grid to charge batteries.

There are two types of energy ball wind turbines available; the V100 and the V200. The V200 is bigger and generates as a result of this much more power. It has 5 rotor blades and a diameter of almost 2 meter. The ball is placed at a height between 12 and 15 meter. The highest power can be generated at a wind speed of 19 m/s and is approximately 2250 Watt. Positioned in an open

Figure 27: DonQi wind mill; power output (kW) plotted field at a height of 15 meter, the V200 energy against the wind speed (m/s) (donQi) ball can on average generate 1750 kWh when (www.1010global.org) the average wind speed is 7 m/s. (home- energy.com)

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The energy ball V200 costs approximately V stands for the wind speed and A is the surface €6000,- excluding installation costs. 2 of the rotor (A = ⁄ * π *d ) (www.treehugger.com) The formula shows that doubling the diameter of the wind turbine will result in a 4 times bigger electricity production. The effect of a higher wind speed is even bigger; doubling the wind speed results in an 8 times bigger electricity production. (www.windenergie-nieuws.nl)

Using this formula, a rough estimation of the electricity production during one year has been made with the information of the donQi wind mill Figure 29: Energy ball; power output (kW) plotted (5,5 m/s gives an annual electricity production of against the wind speed (m/s) 2300 kWh) and the average wind speed per (www.allsmallwindturbines.com) month in Vlissingen. The annual electricity

production is then approximately 3522 kWh ELECTRICITY PRODUCTION WITH WIND TURBINE (12.679 MJ). An approximate maximum electricity Wind is a very variable phenomena. Not only in production for the winter months can be set on its speed, but also in when it is available. In the 300 MJ/week. Netherlands, along the coastline there is always more wind than more inlands. So there is a higher electricity production possible.

Figure 31: Estimated electricity production of the donQi wind mill throughout a year for the location Vlissingen Figure 30: Average wind speed for Vlissingen and (own image) Eindhoven (own graph, based on long term measurements from (www.knmi.nl)) Since the wind speed in winter months is higher In order to calculate the yearly electricity than in summer months and this influences the production of a wind turbine, the following electricity production to the third power, a lot formula can be used: more electricity will be produced in winter than in E = C * V3 * A summer.

E stands for the average year production in kWh. However, when looking at wind energy, it is C is a yield factor (or Beurskensfactor). The higher important to look more specifically at the the average wind speed, the lower the C value is. availability of wind because in order to produce Also the quality of the wind turbine influences this electricity with a wind turbine the wind speed must value. In the Netherlands, a C value of 2,8 is be high enough and in order make this constant, used along the coastline and 4,0 for inland the wind speed should not fluctuate too much. locations. Calculations for average locations can When looking at the behaviour of wind for each use a C of 3,7. month of the year, it can be seen that almost every month, around 90% of the days a wind

14 speed of 4 Beaufort is reached (5,5-7,9 m/s). 8. COMBINING SOLAR ENERGY, However, the amount of days the wind speed is WIND ENERGY AND STORAGE even higher, depends on the season. In order to come to a conclusion of this research, firstly combinations will be made of the different calculations made during this research to seek for a best possible solution of electricity production and storage. All these combinations are 100% electricity autonomous and look at one individual dwelling. (see figure 33) The variables in the combinations are the surface and position of PV cells, the required year-storage and the estimated price of the complete system. Also the electricity production with wind has been added to find out how much less storage is then Figure 32: Number of days that a wind speed is required. Hereby only the winter situation of wind exceeded (own graph, based on long term energy has been taken into account which means measurements in Vlissingen from (www.knmi.nl)) that in summer there will be a larger ratio of

unneeded electricity production. When looking at Concluding from this, it can be said that often all the variables, the most optimal combination is wind energy can supply (part) of the electricity 68 square meter 45˚ south oriented PV cells, one demand. However, how much depends on the wind mill and 15 year-storage batteries. weather conditions and the location. Since the production depends on many different variables and therefore varies often in time, there will always be storage required. In order to determine how much this exactly is more extensive Figure 33: Combining solar energy, wind energy and calculations should be made. storage (own image)

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CONCLUSION speed and availability and thus how much The objective of this paper was to seek for a way electricity can be produced. However, in general to create a more stable energy supply in order to higher wind speeds are achieved in winter months reduce the dependency of the grid, for an energy which means that then more electricity can be neutral dwelling throughout the year by making produced. Therefore it is very smart to combine optimal use of the environment and its climate wind energy and solar energy when striving for an and by integrating sustainable energy autonomous dwelling. Wind energy can reduce technologies in architecture. the required year-storage. However, as a result of The first step in order to achieve this is to limit the the variability of wind energy, it could result in energy demand by passive design solutions. more day/week-storage to buffer the misbalance Applying good insulation, a smart spatial of electricity consumption and production on the organisation, well thought-out positioning of short term. windows, natural ventilation and passive heating When also including the financial aspect, the can all result in a much lower energy demand. most optimal combination to become electricity The second step is to use waste streams of the autonomous found in this research is 68 square building. A heat pump and heat & cold storage meter 45˚ south oriented PV cells, one wind mill allows waste heat and -cold to be stored and and 15 year-storage batteries. However, more used again, therefore resulting in less electricity extended calculations (which includes e.g. the demand to provide heating or cooling. The type of PV cells and a more precise wind energy remaining electricity demand has to be fulfilled by production) are necessary to find out if even better renewable energy sources. On a small scale, combinations are possible. solar- and wind energy are the most profitable sources. PV cells on a south oriented surface with RECOMMENDATIONS a slope of 45 degrees produces the most Many parts of this research topic have not been electricity. Compared to other orientations and completely explored yet because of the limited slopes also less storage is required in this research time and could therefore be researched situation. A negative aspect in this situation further. For example the effect of different PV however is that there is a large overproduction in panel types on the electricity production, or the summer so the production is not very evenly precise distribution of wind energy throughout one divided over the year. Applying another type of PV year. cells such as a thin film PV cell which can produce However, a very valuable part to further more electricity when there is less irradiation investigate is the possibility to combine different could make the electricity production more evenly functioned buildings in a small electricity grid so distributed throughout the year. This is because that less storage is required but also the compared to e.g. polycrystalline panes they can overproduction of electricity can be limited by produce more electricity in in winter months. This exchanging the electricity. By looking at a slightly can also result in a smaller required surface to larger scale, such as a neighbourhood or district, meet the electricity demand. also other alternative storage solutions can be For wind energy it is much more complicated to compared to battery storage such as pumped determine the electricity production throughout a hydro, cells or hydrogen storage year because many variables influence the wind fuel cells.

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APPENDIX 1

19

APPENDIX 2 ENLARGED GRAPHS

Figure 5: Degree days, based on average temperatures in the Netherlands.

Figure 6: Energy consumption of a free standing dwelling

Figure 7: Electricity consumption of an all-electric free standing dwelling (based on own calculations)

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Figure 12: Solar irradiation per orientation, 15th day of the month (Linden, 2005)

Fig 18: Electricity consumption [without heat pump] and production [south oriented]

Fig 19: Electricity consumption [with heat pump] and production with PV cells [south oriented] (own image)

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Fig 20: Electricity consumption [without heat pump] and production with PV cells [south oriented] (own image)

Figure 21: Electricity consumption [with heat pump] and production with PV cells [south oriented] (own image)

Figure 22: Electricity production (W/m2) per year for different orientations and slopes(based on measurements of the KNMI) (Velds, pp. 115-117)

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Figure 30: Average wind speed for Vlissingen and Eindhoven (own graph, based on long term measurements from (www.knmi.nl))

Figure 31: Estimated electricity production of the donQi wind mill throughout a year for the location Vlissingen (own image)

Figure 32: Number of days that a wind speed is exceeded (own graph, based on long term measurements in Vlissingen from (www.knmi.nl))

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APPENDIX 3 ELECTRICITY CONSUMPTI ON VS. PRODUCTION WITH PV

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