Our main partner isthe Netherlandish company Victron Energy, which isfamous for its reliable inverters, chargers and other professional equipment.Webuild . Contact online >>
Our main partner isthe Netherlandish company Victron Energy, which isfamous for its reliable inverters, chargers and other professional equipment.Webuild ...
Atthe beginning of2021, the owner ofahouse under construction near Sofia addressedus toinstall asolar power plant onthe roof. Animportant criterion was uninterrupted power supply.
Inthe process ofnegotiations, westopped onahybrid system that can work both inparallel with the external grid and autonomously. The customer approved the design with the location ofphotovoltaic (PV) modules onall roof slopes.
Inmost cases, our clients avoid compromises and choose equipment ofthe highest level. Therefore, weused the time-tested solar modules from the Japanese company Sharp Solar. During installation, the customer had the pleasure towatch the process from abird’s height and kindly shared photos.
Atthe same time, our experience shows that ingloomy weather all the slopes ofthe roof «work» similarly, therefore, ifthere isasufficient budget, donot neglect the northeastern and northwestern slopes. Insunny weather, the use ofvarious roof slopes allows getting more uniform generation throughout the day from sunrise tosunset.
Apart from its direct purpose— converting solar energy into electrical— photovoltaic modules onthe roof ofthe house give their owners two pleasant bonuses: inhot weather, they significantly reduce the heating ofthe space under the roof, and during the rain they notedly minimize noise.
Photovoltaic modules produce direct current, and ineveryday life, asarule, alternating isrequired: 1-phased or3-phased. Inon-grid solar power plants (without batteries), the modules are connected tothe grid-tie PVinverter, which converts direct current into alternating. Inoff-grid and hybrid systems (with batteries), the modules are usually connected tosolar charge controllers orhybridPV inverters. Inour case, weconnected the solar modules tofive charge controllers and one grid-tie inverter.
For effective operation ofthe power plant, weused the charge controllers SmartSolar from the Netherland company Victron Energy. They lower the voltage obtained from the solar modules tothe level that isnecessary for the batteries, proportionally increasing the charging current. Battery inverters are responsible for converting direct current into alternating insuch systems.
Three charge controllers— MPPT 250/85. The first number inthe name ofthe modification means the maximum allowable voltage atthe input (from the solar modules)— nomore than 250volts. The second number shows the maximum possible current atthe output (tothe battery)— upto85amperes, which atthe voltage ofthe battery, 55volts, provides acharging power ofabout 4.7 kW.
Toeach ofthose controller weconnected 12modules (blue inthe scheme), grouping them into 3strings of4modules. Solar modules ineach string are connected sequentially, which increases the total voltage ofastring. Between themselves, they are connected inparallel, which increases current strength. For the effective operation ofthe modules, all strings connected inparallel should bethe same and beinidentical conditions (azimuth, angle ofinclination, illumination, temperature).
Six modules weconnected toacharge controller MPPT 150/45 (also blue inthe scheme, 3strings with 2modules each) and another 16— tothe newest controller MPPT RS 450/100 (green inthe scheme). This was the first example RS 450/100, installed inBulgaria. The higher permissible voltage atthe input ofthis controller made itpossible tocombine sequentially eight modules ineach string. Inaddition, wewere able toplace two strings ondifferent roof slopes, since the modification RS 450/100 has two independent MPPT (Maximum Power Point Tracking).
The other 36modules (red inthe scheme) weconnected toa3-phased on-grid PVinverter Fronius Symo (Austria) with power of15 kW. Such acombination ofcharge controllers and angrid-tie inverter increases the overall efficiency ofthe hybrid system and deserves aseparate article.
Asusual, weused the special «solar» cables and connectors ofthe highest quality bythe company Stäubli (Switzerland) and mounting elements byAerocompact (Austria).
Wefixed each module atsix points, which issomewhat redundant (usually four isenough), but gradually becomes atrend inthe installation oflarge modules indifficult climatic conditions.
Inthe technical room, weplaced aventilated cabinet with solar charge controllers and amonitoring system, bidirectional battery inverters Victron Energy MultiPlus-II (one for each phase) and a3-phase on-grid PVinverter Fronius.
The full power ofeach battery inverter is5 kV·A (about 4 kWactive power depending onthe type ofload). This means that inoff-grid mode they can give together upto12 kW, while converting direct current from the solar modules and batteries into alternating. During daytime the on-grid PVinverter Fronius ishelping the battery inverters Victron, adding upto15 kW, depending onthe illumination ofthe solar modules.
Here, anattentive reader may object, since the grid-tie PVinverter iscalled «grid-tie», because itworks only inparallel with the external grid and cannot work autonomously. Yes, inaclassic on-grid PVsystem, the inverter really cannot work without agrid, but inour case itispart ofthe Victron hybrid power plant, and battery inverters form the grid forit. This type ofsystem iscalled «Micro Grid».
Itturns out that inoff-grid mode, theAC power ofthe entire system (output power atthe alternating current side) will belimited to12kilowatts inthe dark time ofthe day, with the possibility ofits increase to27kilowatts inaclear sunny noon. Inthe presence ofanexternal grid (hybrid mode) there isnosuch restrictiom, since every battery inverter, additionally toits own power, can transmit upto50amperes from the grid, and this means that the totalAC power ofthe system, even inthe dark time ofthe day, will beabout 40kilowatts, which ismore than enough for the given object.
The risk ofoverloading the system occurs only with alarge consumption inthe house incombination with anemergency shutdown ofthe external grid. Insuch cases, inorder toprevent the overload ofinverters oraquick discharge ofbatteries, all consumers are usually divided into two groups: critical and nonritical. For example, inanaccident with the grid, water heaters and sauna can beautomatically turned off.
Wealso installed three lithium iron phosphate BYD batteries LVL with acapacity of15.36 kW·h each. This type ofbattery isthe safest onthe market atthe moment. The total stock ofenergy inthe batteries isabout 46 kW·h. Based onour recommendation, the customer also purchased two backup solar modules and stores them inthe technical room «just incase».
Weinstalled aVictron Energy touch display onthe door ofthe equipment cabinet, which allows you tolocally monitor the power plant and change settings. The Victron monitoring system also allows doing this remotely via the Internet using the free VRM Portal.
Afew months after the system was put into operation, the owner ofthis beautiful and energy-efficient home sentus new photos with already green lawns. According tohim, the power plant works very well, significantly reducing electricity bills and providing uninterrupted power tothe entire house.
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