SOLAR THERMAL SYSTEM USED AT A SPORTS FACILITY BACHELOR’S DEGREE THESIS Study program: Industrial Design Brașov 2017 INTRODUCTION AND AIMS Renewable… [308692]

Esanu Laura Cristina

SOLAR THERMAL SYSTEM USED AT A SPORTS FACILITY

BACHELOR'S DEGREE THESIS

Study program:

Industrial Design

Brașov

2017

INTRODUCTION AND AIMS

Renewable energy comes from natural resources which are constantly renewed in relatively short intervals of time. [anonimizat] (coal, oil, natural gas). [anonimizat], [anonimizat], [anonimizat] – [anonimizat] a process of globally significant investments to emphasize the renewable energy resources.

Solar energy is the most abundant of all energy resources. [anonimizat]. [anonimizat]. [anonimizat] a [anonimizat].

Today’s [anonimizat] a [anonimizat], [anonimizat], [anonimizat].

The thesis proposes the study of solar thermal systems that can be used at a sports facility.

http://isb.pub.ro/docs/Energii_regenerabile.pdf

Part 1

Chapter 1

Sports facility introduction

Definition of a sport facility

Through “sports facility” [anonimizat], together with the ancillary rooms required and provided with the adequate workout and sports equipment.

Classification of sports facilities

Classification is essential to the understanding of the structure of the object and its validity relation to the urban planning and architectural design.

By the nature of their construction that is limited by the operating possibilities in relation with the different seasons we can distinguish two large groups:

Outdoor facilities: stadiums, sports fields;

Indoor facilities: gyms, [anonimizat].

[anonimizat]. They can be: stadiums, ski slopes or sports fields. Indoor sports facilities allow the practice of sports throughout the year in all weather conditions. [anonimizat]: [anonimizat], [anonimizat].

Also, [anonimizat]:

Simple sport grounds: the practice of one sport;

Complex sports centre: for practicing various sporting activities.

[anonimizat] a [anonimizat]. But, [anonimizat]. The size or capacity of a facility is closely related to the usage it is put to.

Choosing the construction land

When choosing the land to build a sport edifice it must first be taken into account the nature and configuration of the soil.

It is recommended that the soil has a high degree of porosity. This ensures good air permeability and oxygen penetration in the soil, which helps soil mineralization and self-purification. A wet soil (marshes), with low porosity is polluted and unhealthy, and can

contain hundreds of millions of microbes, including those pathogens (B. tetanus B. anthraxes). [7] Since athletes have frequent and hard contact with the ground, they can be in danger of contacting these diseases. When choosing instead the construction site for open type sports facilities, it is necessary to be carried out a chemical-bacteriological analysis of the soil.

The land should be sunny, dry, and have a sufficient slope to assure a good storm water drainage to avoid standing rain water, and the first layer of water should be at least 2m depth. Areas used in the past as dumps, cemeteries are to be avoided. [7]

It is recommended that the sport facility be placed near a flowing water source such that it can be used to sprinkle the fields, cleaning or in case of fire. Water for drinking, hygiene use or swimming pools will be used rom the local potable water outlet.

Once the land is chosen further aspects must be followed [8]:

Stadiums: the playing surface must be smooth, lawn, with as few bumps and foreign bodies on it and with a security area that surrounds the playing surface of at least 1 meter from the side-lines.

Athletics tracks: less and less on clay, modern tracks are covered with synthetic material that provides better flexibility and easier maintenance. They must be provided with delimiting borders that do not exceed the track level.

Jumping pits: filled with fine sand, without foreign bodies, or elastic synthetic material to ease as good as possible the movement.

If the sports complex will be built in a residential area, it is important to determine to what extent it corresponds to the existing buildings: according to the number of floors, architectural appearance, degree of sanitation, the placement, orientation to the cardinal points, the predominant direction and winds character, presence of green areas. The distance between the apartments and public buildings is determined based on insolation and lighting calculations in line with the standards set out in NRC 2.07.01-89 "Urban. Systematization and construction of urban and rural settlements ".[7]

Orientation of the sport fields

The time of day (early morning or late afternoon) as well as the time of year (winter or summer) has a bearing on optimum orientation.

The orientation will be done based on the nature of the construction meaning if it’s an indoor or outdoor playing area. If the playing ground is indoor it will be oriented such that it will have natural light as much time as possible and if its outdoor such that the light does not disturb in any way the activities carried on the grounds. It is generally recommended that playing areas are orientated approximately in a north-south direction to minimize the effect of a setting sun on players. The best common orientation is 15° east of north.[9][10]

However, with more sports being played under lights, this may be less of a concern.

Limits of good orientation where a uniform direction for all facilities can be arranged [10]:

athletics, basketball, bowls, croquet, handball, lacrosse, netball, tennis ─ between 20° west of north and 35° east of north

football: soccer, five-a-side, Australian rules, Gaelic, rugby league, rugby union ─ between 20° west of north and 45° east of north

hockey, polo, polocrosse ─ between 45° west of north and 45° east of north

baseball, cricket, softball ─ between 45° west of north and 35° east of north

Prevailing winds also have to be taken into account. In athletics, the potential problems caused by strong winds are worse than the inconvenience caused by the setting sun. Athletes approaching the finish line should not have to contend with strong winds. Pole vaulters should not be exposed to crosswinds or strong opposing headwinds. The discus is best thrown into a headwind.

In outdoor diving pools, springboards and platforms should face south.

In shooting sports and archery, outdoor ranges should be constructed so that the sun is behind the shooter as much as possible. [11]

Lawn bowling greens must be located away from tall buildings and trees that may cast shadows over the bowling surface, thereby affecting turf performance. This is not relevant for synthetic surfaces. [11]

Cricket pitches must run approximately north/south to minimize the risk of batsmen or bowlers facing a low sun. The pitch axis must point in a direction between 55° and 325° on the compass. [10]

Tennis courts must be oriented with play along an approximate north/south axis.

Microclimate

Heating, ventilation and air conditioning are a vital component to achieve comfortable conditions for the building users. In the case of a sports facilities, the aim should be conditions to enhance user performance. It is recommended a temperature of 15.5-20 degrees Celsius for court sports but a temperature of 15.5-18.3 degrees Celsius for squash sports. In each case, it is recommended a relative humidity of 60% or less and 8-12 air exchanges per hour for enclosed courts. For different type of activates American College of Sports medicine recommends a temperature between 20 to 22 degrees Celsius in the fitness floor area. [9]

Chapter 2

SOLAR THERMAL SYSTEMS

2.1 Thermal energy. Definition and energy sources

Thermal energy is the total kinetic energy that a system possesses. Thermal energy is an important component of the internal energy of such system. [12] Heat is the flow of thermal energy and can be defined as energy in transit due to differences in temperature between two systems. [12]

Thermal and electric energy can be obtained through different types of energy sources. They can be divided in two categories:

Renewable energy sources: are energy supplies that can be renewed, or replenished by natural processes in a reasonable amount of time (in years or a human-life span), once it has been used. Renewable energy is generated from natural sources and include solar energy, the surrounding temperature, the kinetic energy from water or wind-power, the energy content of bio-mass, the energy content from ocean waves and tides, the temperatures of ocean water levels and the energy of the Earth magma and can be generated again and again when needed. [13]

Non-renewable energy sources: are energy supplies that are generated from sources that are available on the earth in limited quantity that will run out or will not be replenished in our lifetimes—or even in many, many lifetimes. Non-renewable sources exist in the form of fossil fuels, natural gas, oil and coal. [14]

Because traditional non-renewable sources are running out fast the attention of the world is focused on renewable energy sources and ways to increase energy efficiency. The ideal scenario is a future were people use cheap and environmental friendly energy sources.

2.2 Solar thermal energy

2.2.1 Solar energy

The sun is probably the most important source of renewable energy available today. [15] It radiates energy uniformly in all directions in the form of electromagnetic waves. When absorbed by a body, it increases its temperature. It provides the energy needed to sustain life in our solar system. It is a clean inexhaustible, abundantly and universally available renewable energy. [16]

The potential of solar energy is enormous: at any moment, the sun emits about 3.86 x 1026 watts of energy. Most of that energy goes off into space, but about 1.74 x 1017 watts strikes the earth. If there are no clouds in the way, then one square meter of the earth will receive about one kilowatt. Even if only 0.1% of this energy could be converted at an efficiency of only 10% it would be four times the world’s total generating capacity of about 3 000 GW. Looking at it another way, the total annual solar radiation falling on the earth is more than 7 500 times the world’s total annual primary energy consumption of 450 EJ. [17] This validates the fact that the sun is the most plentiful source of energy on the entire globe and that it could one day be the most reliant source of energy.

Solar energy can be converted into:

thermal energy- through solar thermal technology, where heat from the sun is used to heating up water or air or to make steam.

electricity- through photovoltaic cells, which directly converts daylight radiation into electricity.

2.2.2 Solar thermal systems

The solar thermal system collects the thermal energy in solar radiation and uses it at high or low temperatures. Low-temperature applications include water and room heating for commercial and residential buildings. High-temperature applications concentrates the suns heat energy to produce steam for driving electrical generators. Concentrating solar power technology has the ability to store thermal energy from the sunlight and deliver electric power during dark or peak-demand periods. [19]

In other words, solar thermal technologies exploit solar energy that can be used for water heating, space heating, space cooling and power generating as well.

Solar water heating

The most common use for solar thermal technology is for domestic water heating. The residential demand for heat can at least partially be covered with a solar water heater, which is a combination of a solar collector array, an energy transfer system and a storage tank. [20]

A solar water heater is a renewable energy technology that heats cold water using the sun’s energy. The main components of any solar water heating system are one or more collectors to capture the sun's energy and a well-insulated storage tank. In north hemisphere, solar collectors are mounted on the south side of a roof where they can capture most sunlight. These collect the heat from the sun and uses it to heat up water which is stored in a tank. The hot water is piped to faucets when tap water is used.

The most common domestic types of solar water heaters are evacuated tube collectors, glazed flat plate collectors and unglazed plastic collectors used mainly to heat swimming pools.

Solar Space Heating

A solar space heating system can either be active, passive or a combination of both. [25]

A passive solar home is designed and positioned in such a way as to take optimal advantage of the solar energy that reaches the home. For example, large south-facing windows, and materials with high thermal mass that absorbs warmth during the day and release the warmth at night when it is needed most.

Homes with active solar energy systems for space heating use mechanical equipment such as collectors combined with pumps, fans, and blowers to help with the transfer and distribution of heat throughout the house.

Solar Space Cooling

The heat from a solar collector can also be used to cool a building by using solar absorption or adsorption coolers. Solar heat is an energy source. Solar absorption/adsorption coolers use a similar approach with home air conditioners, combined with some very complex chemistry tricks, to create cool air from solar energy. [21][27]

Solar Thermal Power Plants

The common basic principle of solar thermal power plants is to use the sun’s energy to generate electricity on an industrial scale. By using giant parabolic mirrors, sunlight is concentrated on an absorber tube through witch a heat-transfer fluid flows. The fluid is heated at very high temperatures and it is then circulated through pipes so it can transfer its heat to water to produce steam. The steam is converted into mechanical energy in a turbine, which powers a generator to produce electricity. [29]

Fig 1.4 Solaben Solar Power Station facility Spain [30]

2.3 Solar water heating systems

2.3.1 Classification of solar water heating systems

We can classify solar water heating systems by several criteria:

By the fluid heated in the collector. When the fluid used in the application is the same that is heated in the collector it is called a direct or open loop. In opposite, when the fluid heated in the collector goes to a heat exchanger to heat up the utility fluid, it is called an indirect or closed loop. [20] A closed loop system uses some kind of a special fluid with anti-freeze properties that has a much lower freezing point than water, yet readily absorbs and releases heat. [31]

By the circulation system of the fluid we can distinguish:

Natural systems- no pumps are required;

Active or forced-circulation systems- electric pumps, valves and controllers move the water between the collectors and the storage tank

Natural Solar Water Heating Systems

The Natural solar heating system do not use any pumps and relies on natural convection to circulate the water through the collectors. Though natural solar water heating systems cost less than active systems they are less efficient and can overheat or freeze.

They can be divided into two basic types [32]:

Integral Collector Storage

Integral Collector Storage systems, also called a “batch” or “breadbox” water heater, combine a solar collector and water storage tank into one single unit. [33]

Thermosiphon

The Thermosiphon system takes advantage of natural convection and gravity. Hot water rises as cold water sinks because gravity pulls down the relatively heavier cold water molecules. Since warm water rises and cool water falls in convection, the storage tank should always be placed above the solar collectors.

Active Solar Water Heating Systems

Active systems use electrically driven pumps and valves to force the fluid to circulate from the collector to the storage tank and the rest of the circuit.

There are three types of active solar water heating systems [36]:

Direct circulation systems

Antifreeze indirect-circulation systems

Drainback indirect-circulation systems

The drainback system use pumps to transport water through the collectors. When the system is not in use, the pump switches off and the water drains from the collectors by gravity into the drainback vessel, eliminating the risk of freezing in cold climates.

Chapter 3

Identification and description of the main components of a thermal solar system

The solar collector is the most expensive and most critical component of a solar thermal system. Besides the collector, a solar thermal system also consists of other system components. Essential are a liquid or gaseous heat transfer medium and pipes to transport the heat transfer medium. Normally, a heat store with none, one or several heat exchangers plus, for certain designs, pumps with a drive to maintain the heat carrier cycle, sensors and control instruments are required. [39]

3.1 Solar collectors

3.1.1 Definition

Solar power has low density per unit area (1 kW/m2 to 0.1 kW/m2). Hence, it is to be collected by covering large ground area by solar thermal collectors. Solar thermal collectors essentially form the first unit in a solar thermal system. It absorbs solar energy, converts it into heat and then transfers it heat transport fluid. The heat transport fluid delivers this heat to thermal storage tank/boiler/heat exchanger, etc. to be utilized in the subsequent stages of the system. [16]

3.1.2 Classification

Solar collectors can be classified into [40]:

stationary (or non-concentrating);

concentrating systems.

The main difference between them is the way they collect solar radiation. The stationary collectors absorb beam as well as diffused radiation as it is received on the collector, while for concentrating-type solar collectors solar radiation is converged from a large area using optical means and they mainly make use of the beam radiation component (plus very little diffuse component coming directly over the absorber).

A classification of various solar collectors is done in Fig. 3.1.

3.1.3 Flat-plate collectors

Flat-plate collectors can be designed for applications requiring energy delivery at moderate temperatures. They use both beam and diffuse solar radiation, do not require tracking of the sun, and require little maintenance. They are mechanically simpler than concentrating collectors and have a long lifetime. The major applications of these units are in solar water heating, building heating, air conditioning, and industrial process heat.

The typical flat-plate collector has the following main components [41] [42]:

Glazing cover which may be one or more sheets of glass or a radiation-transmitting plastic film or sheet that transmits radiation to the absorber, but prevents radiative and convective heat loss from the surface.

Tubes, fins, passages or channels which carry the water, air or other fluid from the inlet to the outlet.

The absorber plate with tubes, fins or passages attached to it. The plate is usually metallic (copper, aluminium, steel or ceramic) and painted flat black or electroplated with a selective absorber, although a wide variety of other materials can be used, particularly with air heaters.

Insulation covering sides and back of the collector to reduce the heat losses.

Container or casing to enclose the other components and protect them from dust and moisture.

The transparent cover and the insulation may be omitted for low temperature rise applications, such as heating for swimming pools.

3.1.3.1 Glazing materials

The purpose of glazing or transparent cover is to transmit the shorter wavelength solar radiation but block the longer wavelength radiation, from the absorber plate, and to reduce the heat loss by convection from the top of the absorber plate.

Glass is the most common used material to glaze solar collectors [43]. Glass material has highly desirable property of transmitting as much as 90% of the incoming short-wave radiation, while virtually none of the long wave radiation emitted by the absorber plate can escape outwards by transmission. [44] Glass with low iron content has a relatively high transmittance for solar radiation (0.85-0.90 at normal incidence) [45] [46] Transparent plastics, such as polycarbonates and acrylics are also used as glazing for flat plate collectors, but because most usable varieties also have transmission bands in the middle of the thermal radiation spectrum, their longwave transmittance can be as high as 0.40.[45][47]

To minimize the upward heat loss from the collector, more than one transparent glazing can be used. However, with the increase of the number of the cover plates, transmittance is decreased.

3.1.3.2 Absorbers

The purpose of the absorber is to absorb as much of the irradiation passing through the glazing as possible, reemit as little as possible, and allow efficient transfer of heat to a working fluid. The absorber plate material should have high thermal conductivity, adequate tensile and compressive strength, and good corrosion resistance [48]. Copper is generally preferred because of its high thermal conductivity and high corrosion resistance. Other suitable materials used for absorber plates include copper, aluminium, stainless steel, galvanized steel, plastics, and rubbers. [47]

In order to increase the absorption of solar radiation and to reduce the emission from the absorber, the metallic absorber surfaces are painted or coated with flat black paint or some selective coating. A selective coating has high absorptivity in the solar wavelength range (0.3 to 3.0 μm). [47]

3.1.4 Evacuated-Tube Collectors

Another type of solar collector used in solar thermal systems consists of rows of glass tubes connected to a common header at the top. Inside each tube is a vacuum (hence the name evacuated tubes) that acts as an insulator reducing convection and conduction heat loss therefore making the collector more efficient than flat-plate collectors, especially in colder climates with low level diffuse sunlight. [49]

There are two types of evacuated tube collectors [51]:

Direct flow – the heat transfer fluid is circulated through copper tubes attached to a absorber plate mounted inside the evacuated tube.

Heat pipes – uses a heat pipe attached to the absorber plate. The heat pipe transfers the heating energy to the condensing section of the heat pipe where the collector fluid is warmed. This takes place in the header where the evacuated tubes are connected.

The most common evacuated tube is a direct flow collector consisting of two glass tubes fused together. Within the vacuum is located between the inner and outer glass. The solar absorbing coating is sputtered onto the outside of the inner glass tube. A heat conductor/transfer sheet is located inside the inner glass tube that conducts the heat to the manifolds. [52] The vacuum tube collector can be paired up with a parabolic reflector located behind each tube to enhance performance. The solar radiation that passes through each tube will be reflected to the underside of the cylindrical absorber in the collector tubes. [49]

3.1.5 Concentrating Collectors

These collectors use mirrors or Fresnel lenses to concentrate sunlight onto a small area to produce high temperatures. Such high temperatures are needed for industrial uses and for making steam in electrical power generation. Because they use only direct-beam sunlight, parabolic-trough systems require tracking systems in order to obtain the optimal benefit. These collector systems require large areas for installation, so they are usually ground mounted. [51]

3.2 Storage tank

Beside the collectors, the storage tank is the second essential component of solar thermal systems, since solar energy is a time-dependent energy resource. The solar tank stores the solar-heated water until it is needed. [56]

The main types of cylinders for domestic water production are:

a) Simple tank (Fig 3.8 a)

b) Single Coil Cylinder (Fig 3.8 b)

c) Twin Coil Cylinder (Fig 3.8 c)

Storage tanks can be classified according to various criteria [58]:

Application

Positioning: Vertical or horizontal type

Stratification device: with or without

Material: stainless steel, vitrified steel, copper or others

Internally or externally heat exchanger

3.3 Pump station

Solar pump stations are used on the solar loop of a solar thermal system to circulate the heat transfer fluid through the array. They are also used to control the temperature in the solar storage tank.

The main components of a pump station are:

Circulating pump – in solar thermal systems with forced circulation a pump is required to move the heat transfer fluid through the piping circuit [59];

Thermometer – in solar thermal systems for hot water production, they are meant to indicate the flow and return temperatures from the solar circuit [60];

Pressure gauge – provides a visual indication of system pressure [59];

Volumetric flowmeter – helps in measuring the heat-transfer fluid’s flow rate [59];

Over pressure' safety relief valve – ensures that the system pressure limit isn’t exceeded, and protects the piping and components from extreme overheating or loss of circulation [59].

Valves – devices with adjustment and control functions in the circuit [61].

3.4 Solar controller

The solar controller is an electronic device that decides when there is sufficient solar energy available in the collectors that

justifies running the pump to transport to the solar storage. To do this, the controller compares the collector temperature using the collector sensor and the temperature in the lower area of the storage tank (tank sensor). [63]

3.5 Expansion Tank

The expansion tank is a safety device that prevents pressure increases due to thermal expansion of the solar fluid, ensuring that the maximum operating pressure is never reached. In closed loop systems, expansion tanks are critical elements and must be appropriately sized for the system to operate properly. For expansion tanks, the acceptance volume must be sufficient to accommodate expansion of the heat transfer fluid when the solar loop goes into stagnation. [65]

Part 2

Chapter 4

Case study – Dimensioning of a solar thermal system at a sport facility

In this chapter, we will dimension a solar thermal system for hot water for a sport facility. The case study will be conducted on a sports facility located in Brasov, Romania.

4.1 Solar potential in Romania

In the spring session of the European Council of 9 March 2007, the European Union adopted a new policy on renewable energy and set the objective of increasing the share of renewable energy in total energy consumption by up to 20% (later increased by Directive 2009/28 / CE to 24%) until the year 2020, as part of the so-called 20/20/20, as subsequently amended by Directive 2009/28 / CE. Hence, as a member of the European Union, Romania has the obligation to support and promote renewable energies in order to achieve this objective. [67]

Romania has an average of 210 sunny days a year and annual solar flux ranging from 1,000 kWh/m2 /year to 1,300 kWh/m2/ year, placing it among countries with notable solar potential. Of this, around 600-800 kWh / m2 / year is 100% useable. [68]

4.2 General presentation of the sport facility

Brasov is located in the central part of the Country. It is surrounded by the Southern Carpathians and is part of the Transylvania region.

The sport facility chosen for the case study is Tennis Arena Club located on Grivitei 1W Street in Brasov. Tennis Arena has 9 clay courts: 3 in the main hall, 3 in an inflatable sports dome and 3 outside. Therefore, the sport base has 6 useable tennis courts no matter the weather or the season.

The main hall has a surface of 2000 m2. The ceiling is made out of wood and the curved roof is made of metal sheets fastened with screws on wood. Beside the 3 tennis courts the main hall is equipped with desk reception, 2 locker rooms and 3 gym rooms for ballet, aerobic and boxing classes. Each locker room include 3 showers and 2 washrooms.

4.3 System Design

Preliminary studies are carried out before designing the water supply system for domestic hot water. They are aimed at estimating the potential interest of the future installation in relation to the domestic hot water demand (quantity and regularity on during the year) as well as the existence of technical or architectural constraints by:

– dimensioning of the installation taking into account the different constraints;

– cost estimation;

– estimation of provisional savings. [71]

4.3.1 Estimating the hot water demand

To estimate the hot water demand, a rough calculation regarding the number of athletes and the hot water consumption in an average week was carried.

The Tennis Arena schedule is:

7-24 from Monday to Friday- 17 working hours

9-20 in the Weekend- 11 working hours

To approximate the average number of persons in an hour several factors have been taken into account: the fact that tennis can be played in two and four persons; good and bad weather days; full and slow days (when either all the courts are full or all are empty).

We came with a rough average number of 11 people per hour.

17×11=187- average number of persons/day from Monday to Friday

11×11=121- average number of persons/day in the Weekend

(187×5+121×2)/7=168- average number of persons/ day

We assume that from the total number of persons per day 60% of them shower at the facility:

168×0.6=101 persons

For every shower, an athlete uses 25 litters of hot water at a 60°C [72] so the total hot water demand is:

101×25=2525 litters per day

4.3.2 Local solar radiation

By studying the Global Horizontal Irradiation map for Romania, Brasov has a Global Horizontal Irradiation between 1100-1300 kWh/m2 having a medium solar potential.

By using “NASA Surface meteorology and Solar Energy” we obtain further meteorological data related to solar radiation for Brasov.

NASA Surface meteorology and Solar Energy is a renewable energy resource web site that displays various information (solar radiation, wind speed, atmospheric pressure, air temperature and humidity) for photovoltaic and renewable energy system design needs.

The database includes:

over 200 satellite-derived meteorology and solar energy parameters

monthly averaged from 22 years of data

data tables for a particular location

4.3.3 Site assessment

It is essential to make a site assessment before designing a thermal system to be able to avoid planning errors. This gives a designer an opportunity to see the basic conditions and limiting factors of the site.

The site assessment concerning Tennis Arena Building was carried out on the date of May 6th, 2017. Suitability for installation, building orientation, available area for installation, far and near shading objects and possible mounting options were investigated during this assessment.

The façade of the main building is oriented to south. There are no near large buildings, trees or other obstacles that can cause shading on our system installation.

Usually the roof of a building seems the most normal place for installing collectors because of space optimization. This way unused space can be put to work.

Unfortunately, the Tennis Arena roof is not ideal for our installation because:

The roof is not ideally oriented to south and because of the orientation and height of the building it will resulting in energy losses;

A possible reinforcement of the roof will be required to withstand the weight of the collectors;

Possible angle restriction because of snow in the winter.

Therefore, the system will be mounted on a nearby area on the ground.

The mounting location is on the left of the building, near the locker room, so heat losses will be reduced.

4.3.4 Collector orientation

Optimization of a collector orientation is an important process in order to collect as much irradiance as possible on the surface of the collector. To be able to this, collector inclination angle (β) and azimuth angle (γ) should be optimized.

The collector field should be directed towards south (γ=0°) in northern hemisphere in order to collect maximum available irradiation on the plane.

Optimum inclination angle is determined according to the application of the system. In this study, the inclination angle is chosen for annual year-round water heating. Optimal tilt angles are lower for hot water production and swimming pool warming because of the highest height of the sun during the summer. For hot water, the inclination angle is chosen between 15°-45° [72]

The general rule of thumb to determine the optimal inclination angle is taking latitude equal to inclination angle. [74] However, from the NASA Surface meteorology and Solar Energy we see that the annual irradiance is higher in Brasov at a tilt of 30° than 45°. This differentiation results from the fact that for the locations with larger latitudes, the difference between winter and summer irradiation increases.

For our study, the orientation will be done at γ=0° and β=30°.

4.3.5 Calculation of the number of collectors and the size of the storage tank

First of all, in designing a solar thermal system the designer must appreciate what kind of collector is better suited in the installation by taking in account orientation, placement restrictions, yearly solar radiation and cost.

For domestic hot water, there are two types: flat-plate and evacuated tube collectors. Both types of collectors have advantages and disadvantages. For our system, we will use flat-plate collectors because we are designing only for hot water, they cost less and because the mounting is on the ground we are not restricted as in a roof mounting.

It is determined that we will need a total of 20 flat plate collectors with an aperture surface of 35m2. The number of collectors is determined for a daily consumption of 2500 l in a region with solar radiation between 1200-1400 kWh/m2 (Brasov radiation) by consulting the chart in in Solar System Design Catalog. [71]

The size of the solar tank is calculated by intersection of the vertical line (the correct value of the need) with the corresponding line curve (see fig. 4.5):

– Curve for high variability in weekly consumption

– Curve for low variability in weekly consumption

More regular weekly consumption profiles can be better "damped" by means of a larger size solar tank.

By consulting the chart, for 2500 l/day of water needed for high variability in weekly consumption, the storage tank needs to have a capacity of 3000 l.

4.3.6 Hydraulic sizing of the installation

4.3.6.1 Total solar system flow rate

Our system works in a normal “flow”, meaning that the recommended flow rate of the heat transfer fluid, is between 40 and 60 l / h per m² of the collector area at a flow rate equal to or less than 1 m / s.

4.3.6.2 Collector Array

Depending on the location and the concept of the installation, the collectors can be connected in series or in parallel. Series connection guarantee uniform flows but the pressure drop is likely to be prohibitive, especially in large arrays. Whenever collectors are put in series, the pressure drop should be checked. The parallel arrangement is favourable from a pressure drop point of view, but it requires more piping and larger pipe dimensions due to larger flow rates. [76]

The most manufacturers recommend only 5 to 6 collectors to be connected in the parallel arrangement. In the serial arrangement, the maldistribution problems do not occur, but a high number of collectors in the array will, however, entail too high pressure drop. [76] To avoid any flow difference in the collector fields, it is important that the number of collectors in series / row is the same.

For our case study with 20 flat-plate collectors, we came with the following arrangements:

When choosing the collector array, we must think of pressure losses but also in terms of space. In that manner, we will also take into account the fact that when installing several rows of collectors in series behind each other, suitable clearance to prevent shading must be maintained. To determine the clearance, we require the angle of the sun at midday on the 21.12, the shortest day of the year. In Brasov, this angle is 20.87°. [77] [78]

The resulting clearance between rows is calculated as follows [77]:

z = Collector row clearance

h = Collector height

α = Collector angle of inclination

β = Angle of the sun

For Brasov with a collector of 2 m height, angled at 30°:

z=2*2,177=4.35 m

The centre dimension z of the collector rows must be at least 4.35 m.

By taking into account the fact that we have to leave between each row a clearance of 4.35 m we will use the two-array connection because it better fits our space.

A final overall scheme for our water heating system is represented in Fig 4.8.

4.3.6.3 Sizing of the collector circulation pump and the pipe diameters

When sizing the pump, the pressure drop calculation must not be carried after choosing the pipes, but rather simultaneously because, depending on the calculation result there may be needed modifications in the pipe dimensions.

To choose a proper pump we will require two things: pump head and flow rate. The head represents how high the pump can lift a column of water and the flow by how much fluid (gallons or litters) a pump can push at a given head. [79]

The following rough procedure to cover closed loop systems assumes a 50-50 water glycol antifreeze mix for a temperature of 60°.

Our system with 20 flat-plate with 35 m2 absorber area, and a required specific flow rate of 40 l/(h · m2) has a throughput of 1400 l/h or 23.3 l/min. [77]

We will multiply the collector flow rates by 1.15 to account for its lower heat transfer capability, because antifreeze increases viscosity and pipe friction losses, and also the antifreeze has a lower heat capacity, so more antifreeze mix must be circulated to transfer the same amount of heat out of the collector. [80]

Target Flow Rate=23.3* 1.15=26.7l/min

Because there is no static head (the fluid is circulated back to the same level) we will only calculate the dynamic head. In this step, we will estimate pipe sizes, and then calculate the total pressure drop through the system for: 1) the collectors, 2) the supply and return pipes and the fittings in these pipes, and 3) any valves or other pressure drop causing components.

We will calculate friction loss for 10 m of pipes. Because friction loss calculations are complicated we will use SF Pressure Drop 8.0 a software that calculates pressure drops of flowing liquids and gases in pipes (laminar and turbulent flow) [].

By consulting Fig 4.10 for a flow rate of 25 l/min we will use DN 32 copper pipes. Also, we will have: 2x Tee, 2x Circular bend and 4x check valve. The flow medium is a mixture of 50% water and 50% glycol.

Collectors (even those connected in parallel in one array) contribute significantly to pressure losses and, therefore, it is extremely important not to be neglected. The collector manufacturer must provide pressure loss curves with at least two reference flows. [72]

For the sake of our calculation we will use a chart from a flat plate manufacturer. For a flow of 0.068m3/h there is a pressure loss of 1.8mbar/ solar collector.

By adding all the pressure losses, from the pipe, fittings and collectors we obtain 0.205 bar.

0.205 bar = 2.09 meters head

Because we don’t want a pump that just barely have enough head, we can oversize it a bit and choose a pump with 2.5-3 m pump head with a flow of 26.7 l/m. To determine which pumps might meet those criteria pump curves are used.

4.3.6.4 Sizing the expansion vessel

In closed loop systems, the expansion vessel must be appropriately sized for the system to operate properly. For expansion tanks, the acceptance volume must be sufficient to accommodate expansion of the heat transfer fluid when the solar loop goes into stagnation. For closed loop solar systems, the expansion tank must be acceptable for use with propylene glycol or other heat transfer fluid used in the collector loop.

In our sizing, we used the table below (Fig 4.12) to select the coefficient for a 50% glycol mix at the temperature of 130°.Further we used an online excel sheet where we introduce our parameters. The result is that the volume of the expansion vessel is 295 l, so next available to market would be an expansion vessel of 300 l.

3.4 Collector mounting

3.4.2 Frame

A frame should stabilize and maintain the solar collector. Therefore, planning the frame is one very important part of the installation of the solar panel. We will model a frame for two collectors. The frame can be used modularly to obtain different combinations.

Part 3

Techno-Economic Feasibility Analysis

A Techno-Economic analysis will be conducted to provide us with information regarding cost and the amortization period and also to prove the practicability of the project.

Chapter 5

This economic analysis is designed according to the technical framework described in Part 2-Chapter 4. Many of the required inputs were satisfied using data from Chapter 4 but the actual equipment considered for use will be chosen in this chapter.

5.1 Input data

Technical project

1.Project theme

Water heating for Tenis Arena sport facility for a number of 100 persons/day

2.Hot water demand

2500 l/day hot water at 60°C→107.5 kWh/day []

3.Availability of solar energy

4.Solar thermal system

Closed loop forced circulation system

35m2 absorption collector area.

20 Flat-plate collectors

3000 l storage tank

5.2 Selecting the main system components

5.2.1 Flat-plate collector

Ariston Kairos CF 2.0

Absorber with highly selective treatment to titanium oxides (95% absorption reflection 5%)

44 mm toughened hail-proof anti-reflective glass

Hydraulic circuit with copper pipes

Harp geometry and ultrasound welding

Designed and sized in systems with forced circulation

Can be inclined between 30° and 60°

Test report according to EN 12975

Aperture surface m2 – 1,82

Absorbent surface m2 – 1,74

η0 – 0,738

5.2.2 Storage tank

ELBI- BF1-3000 with extractable Heat exchanger

5.2.3 Pumping Station

Two-line solar station DN20 TACOSOL ZR-HE

5.2.4 Controller

STECA 301 PWM controller

5.2.5 Expansion vessel

VAS DE EXPANSIUNE VAREM, DIN OTEL, CILINDRIC, VERTICAL, 6 BAR, 100L

5.2.6 Auxiliary energy source

The auxiliary energy source works when there is not enough solar radiation to cover the energy demand for hot water.

Usual solutions:

-heat pump

-electric heater

-gas heater

5.3 Techno-Economic Analysis

5.3.1 Costs

Costs are divided between:

Initial investment cost

Operating cost

Maintenance cost

The initial investment cost consists of the total value of the initial equipment or other supplementary components needed for the solar thermal system.

Regulated rates for household customers who have not exercised their eligibility established by The National Energy Regulatory Authority valid from 1 July 2017 according to Order no. 175/2015 (published in MO No 481 / 26.06.2017) []

5.3.2 Annual energy covered by solar and auxiliary source

Kairos CF 2.0 (η=70%)

The monthly energy requirement for domestic hot water preparation

EM = ED x N [kWh / month]

ED = 107.5 kWh / day (daily energy requirement for domestic hot water), N = no. of days in the month

The monthly thermal energy obtained through the conversion of solar energy

ETM = SCST x ESD x N x η [kWh / month], SCST=35 m2 (collector area),

ESD = solar energy available daily, η = 70% (conversion efficiency)

Amortization period of the solar thermal system

CII = Costs with initial investment, EA = annual energy requirement for DHW,

E = ETM monthly thermal energy obtained by converting solar energy

ES = energy saving

EEE = savings due to non-use of electricity energy

CEE = costs of auxiliary energy for the use of electricity

AEE = depreciation of the CST system taking reference price of electricity

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