ITIS. MAJORANA MARTINA FRANCA (ITALY) COMENIUS PROJECT 2012-2013 Meeting Somonino (Poland) - 10-12 April 2013 Plus Energy House Teachers: A. Entringer V. Colucci A. Laddomada Students : Gianluca Di Giuseppe, Luca Calianno, Antonio Castronuovo, Ivan Cecere, Giuseppe Minardi
PHOTOVOLTAIC PROJECT
TECHNICAL REPORT ILLUSTRATIVE A photovoltaic system converts solar energy directly into electricity. It is composed essentially of modules, inverter, batteries, charge controller, energy meters, cables and panels. The modules are made up of cells in semiconductor material, the most widely used of which is the crystalline silicon. They represent the active part of the system because they convert the solar radiation into electricity. The inverter converts the direct current DC generated by the modules in the current AC; The batteries in stand-alone installations are used to store electrical energy for the night and for days without sun
The charge controllers have the function of regulating the electric voltage of the panels to the voltage of the batteries. The energy meters are used to measure the amount of energy produced and energy consumed. The electric panels and cables are used for protecting the system, to link its components and to connect the PV system to your home network and the public network in the grid-connected systems.
They may be of the type stand alone and grid connected. A stand alone system is not connected to the public electric grid and stores in battery storage the energy that is not consumed. A grid connected system is connected to the public electric grid and the energy that is not consumed is introduced into the network.
The advantages of photovoltaic systems can be summarized as: absence of any type of pollutant emissions; saving of fossil fuels; plant reliability because there are no moving parts; costs of operating and maintenance costs to a minimum; modularity of the system (to increase the power of the system it is sufficient to increase the number of modules). The annual electricity production of a PV system depends on several factors: solar radiation incidence on the installation site; orientation and inclination of the modules; presence / absence of shading; technical performance of the system components (modules, inverters and other equipment). In Italy the values of manufacturability annual maximum for PV systems from 1 kwp of power are the following: northern regions from 1000 to 1100 kwh / year; central regions from 1200 to 1300 kwh / year; southern regions from 1400 to 1500 kwh / year. measured under standard conditions (temperature of 25 C - radiation of 1,000 W/m²).
The design of a photovoltaic system is divided into the following phases: - Preliminary operations and inspections calculation of user requirements to be served; determination of the annual solar resource; dimensioning and verification of the generator; sizing of storage systems; sizing of the inverter; Project of the other constituents of the system and the interactions with other systems Estimation of user requirements The photovoltaic system must always be dimensioned according to the type of user and its consumption. The require energy is calculated taking into account the power of each device and operating time in hours per week (see attached table). Generally, the data they are more interesting in the design of the PV system include the level of total load in the average days per month (kwh / day) and per annual (kwh / year).
Estimated output energy The EPV annual producible power of the photovoltaic system is given by the following analytical expression: Epv = η pv * H * Apv η pv is the overall efficiency of photovoltaic conversion; Apv is the area occupied by all the modules that make up the generator, in m2; H is annual incident solar radiation on the module surface, expressed in kwh/m2. For the values of H is necessary to use the climatic data relating to the position in which is located on the system. The amount of energy produced varies with the angles of inclination and orientation of the surface of improvement of the individual modules, in addition to the eventual artificial shading. The overall efficiency of the photovoltaic conversion ηpv depends on the efficiency of photovoltaic system components (cabling, inverters, etc.), overheating of the panels, by reflection phenomena of the incident radiation, on the formation of deposits of powders on the panels and, finally, on the efficiency η of the single module. Currently, the technology of crystalline silicon modules, it can be assumed that the overall efficiency of photovoltaic conversion ηpv different between 0.09 and 0.17; It is possible to write: EPV = 0.14 * H * Apv (kwh / annual).
Sizing of a photovoltaic system "stand alone" The design of these systems must be carried out with extreme precision and calculations must be reported to the minimum solar radiation during the winter months. Batteries must provide at least three days of energy independence. They must be satisfied with the following equation: Epv Ec being: Epv average daily energy produced by the generator in kwh / day in December Ec the energy required by the system in kwh / day; The energy Ec request is calculated in turn by multiplying electricity actually consumed every day by the user (Eu) by the overall efficiency of the plant. Ec = Eu / (ηb * ηc ηrc *) = (Ec > Eu) being: ηb the efficiency of charging and discharging of the battery (about 0.90); ηc the performance of circuits (approximately 0.90); ηrc the efficiency of the charge controller (approximately 0.85).
So that it is approximately: Ec = 1.40 * Eu Ultimately must be satisfied the following equation: 0.14 * Apv Hmin = 1.40 * Eu and from this formula you calculates then the minimum total area of the panels Apv = (1.40 * Eu) / (0.14 * Hmin) The stand-alone installations are used only in the absence of public electricity grid and are less convenient than the of grid-connected: -They have a much higher cost due to the presence of the batteries. -The batteries require constant maintenance and have a limited duration, at the end of their life cycle, there is the problem of their disposal because they are toxic waste. -The systems must be designed taking into account the solar radiation in the winter months.
Sizing of a photovoltaic system grid connected When the PV system is connected to the utility grid, it is no longer the only source of energy, but it becomes an integrative system and a source of income. The system can so be freely dimensioned on the basis of economic, energy and environmental issues. The "grid-connected" is undoubtedly the best solution for photovoltaics, as it is characterized by a lower cost for the absence of accumulation systems and greater flexibility of use. The energy produced during the day can be used directly and the excess energy is not lost but is fed into the network available to other users,, while at night it is drawing power from the public grid. The difference between the energy produced and consumed is measured by special meters and tariffed and can be a source of income. In the same area Apv the grid-connected system produces much more energy useful because the calculation of the energy produced is done according to the average annual solar radiation and not to the minimun radiation; 0.14*Apv* Hmed annual = 1.10 * Eu
SIZING OF PHOTOVOLTAIC SYSTEM PLUS ENERGY HOUSE As agreed at the meeting in Budapest 5-6-7 December 2012, our working group has been tasked with designing the PV system and the wastewater treatment plant of the Plus Energy House designed by students from Germany and the Netherlands. It is a small house of 24 sqm. The roof is tilted at 25 degrees, is south facing and has an area of about 41 square meters. The photovoltaic panels will be placed on the roof tiles with special anchoring structure. The inverter, charge controller, the connection boxes and any batteries will be placed in the room under the roof, which is accessed through a trap door in the ceiling. Counters and protection panels will instead be on the ground floor. Phases of the project First, we searched on the Internet (http://re.jrc.ec.europa.eu/pvgis/) values of solar radiation for each location of the partner schools. The design calculations were carried out considering the photovoltaic system both in the stand-alone and the grid connected type, so to compare the results.
The calculations were repeated considering the location of the house in all seven European sites of the partner schools. The project was carried out in th following stages: 1 - Calculation of the energy needs of the house (Table 10). 2 - Calculation of the surface of the roof and choice from the catalogue of the photovoltaic panel to install; 3 - Drawing on the roof of the panels so as to use the entire available surface. From this operation we obtained the total number of panels to be placed equal to n. 24. 4 Calculation of the amount of energy produced by a stand-alone system 5 - Calculation of the amount of energy produced in a grid-connected system 6 - Design of electrical circuits 7 - Architectural drawings of the house with the PV system on the roof. 8 - Choise of the components taking into account the project data (see technical information). 9 - Estimated expenditure. 10 - Collection of all the projects in a slide show.
CALCULATION OF ANNUAL SAVING OF CARBON DIOXIDE We know that to produce 1 kwh of electricity, a power with fossil fuels in the atmosphere introduces approximately 0.65 kg of carbon dioxide. Therefore our photovoltaic system will generate savings of carbon dioxide per year (RCO2) equal to: 1. For the stand-alone system: RCO2 = 0.65 x (Ec) = 0.65 x 3196 kwh per year = RCO2 = 2.077 kg Where 3,196 kwh per year is the total annual energy needs of our house (Ec) 2. For the grid-connected system: RCO2 = 0.65 x (EPV) = 0.65 x 8303 kwh per year = RCO2 = 5.397 Kg Where EPV is the total energy produced in a year by the PV plant in Martina Franca (see table).
CONCLUSIONS As appears from calculations, you clearly notice that between the two types of photovoltaic systems, on equal total surface of the panels installed, no doubt the grid connected system is preferable for the following reasons: 1. It costs less. 2. It has less maintenance costs (no batteries) 3. There is no waste of energy produced because what is not consumed by the owner is sold to others. 4. Therefore it is also a source of income. 5. It allows to save additional annual amount of Co2.
SEWAGE TREATMENT PLANT PROJECT
The Phyto - Transpiration system
Phyto-Transpiration The PHYTO-TRANSPIRATION system completely eliminates waste waters in: houses villas, country houses, small centres. The depurating system is based on the evapotranspirating power of evergreen plants, that absorb and make the sewage evaporate using mineral salts produced by the active vegetable soil (phyto-depuration); thanks to it the waters coming from the house can be completely absorbed by the roots of a group of plants without creating any nasty smell or danger of polluting the environment.
This depurating system is obtained by setting those plants down a biological Imhoff tank or a system with active muds for a total oxidation, where it s not possible to throw depurated waste waters because of laking sewers. The system is modular, so it can be easily enlarged if necessary.
The system can be realized with basin in fibreglass, polietilen or reinforced concrete. The phyto-transpiration system is made of a number of components opportunely set under the ground around the house and these are: An Imhoff tank, or a biological depurator, one or more absorbent beds and two little sumps, one for inspections and the other to raise and to recycle the water. The setting is extremely simple and can be easily, done by any plumber or mason who, ofter having dug the right holes, hare only to link the components with PVC pipes.
Imhoff Tank The Imhoff tank are realized in fibre-glass or polietilen they are resistant, light-weighted, perfectly impermeable, this allow to make them ready to use easily and quickly; they don t require any upkeep, and they garantee an unlimited duration with complete absence of leakages, corrosions, infiltrations, etc Biological Imhoff tank are built up in order to make the entering sewage remain in the sedimentation section 4-6 hours, to avoid putrefaction cases; the digestion section must have a volume of 100/110 inhabitants.
It consists of an upper chamber in which sedimentation takes place, from which collected solids slide down inclined bottom slopes to an entrance into a lower chamber in which the sludge is collected and digested. The two chambers are otherwise unconnected, with sewage flowing only through the upper sedimentation chamber and no flow of sewage in the lower digestion chamber. The lower chamber requires separate biogas vents and pipes for the removal of digested sludge, typically after 6-9 months of digestion. The Imhoff tank is in effect a two-story septic tank and retains the septic tank's simplicity while eliminating many of its drawbacks, which largely result from the mixing of fresh sewage and septic sludge in the same chamber.
Imhoff tanks are being superseded in sewage treatment by plain sedimentation tanks using mechanical methods for continuously collecting the sludge, which is moved to separate digestion tanks. This arrangement permits both improved sedimentation results and better temperature control in the digestion process, leading to a more rapid and complete digestion of the sludge. A test for settleable solids in water, wastewater and stormwater uses an Imhoff cone, with or without stopcock. The volume of solids is measured after a specified time period at the bottom of a one-liter cone using graduated markings.
Subirrigation System The Subirrigation is a particular system of application of the waste water in the ground, consisting in the introduction of the waste water, through suitable pipes, directly under the surface of the ground if it is absorbed and gradually assimilated and degraded biologically with those powerful and complex natural mechanisms.
THANKS FOR YOUR ATTENTION