Uvod – Introduction
Ovo je tekst koji smo objavili na blog stranicama tvrtke Victron energy, našeg partnera u području opreme za fotonaponske sustave. Stoga ovaj tekst ne prevodimo već ga donosimo u cijelosti na engleskom kako je objavljen. Vjerujemo da to neće biti prepreka čitanju!
We are aware of the introduction of so-called Nearly Zero Energy Buildings, through concepts like passive houses, green buildings, sustainable buildings or solar houses. The Heat that is not lost does not have to be actively supplied to the house. This is the key principle of the Passive House Standard and is achieved mostly by using a well-insulated building envelope, sun shining through the windows, and a ventilation system in which internal heat together with heat from sources such as people and appliances is recovered from the extracted air. The low remaining energy demand can be met by using renewable energy sources. Concerning the remaining electrical energy supply to the house, we must control house consumption from mains! Today photovoltaics and battery storage technology enable that.
But we are all aware that presenting power electronic products and their features is not a quite simple task, even if we have experienced and educated customer or planer in front of us! But how to present it to students in ages 15 to 20, before they enter universities and colleges? We are deeply convinced that this age is the last minute for young people to wake up intrinsic interest in the field of renewables. Shall we use the component to system or system to component approach (down to top or top to down) lecturing? We decided with students to go top-down strategy. Schrack Technik uses Victron Energy Storage System as the right story for that approach!
Schrack Technik „top-down“ story:
It is clear to every student that it will be optimal that house can cover its needs and in addition to produce energy for our electrical cars too! After making a good building envelope, exchange of windows, introducing heat recovering from intern air, what could we do further?
Today we are using mains as the only energy source. The sun energy is at our disposal as a cost-free alternative energy source, but let us do more. Let us do it as a dominant energy source and mains as a reserve source. How much today’s house energy consumption could be covered with solar energy is related only to technical equipment dimensioning. In the picture below is the whole system. The house owner should set mains house consumption. Then actual consumption from mains is measured. Based on the difference between set and actual consumption the consumption controller will pass the energy (either directly from the Sun or stored from the battery) to house loads. So long there is enough energy from Sun or stored in the battery, house consumption from the mains will be held on the set point. Once there is no Sun or there is no more energy stored in the battery, the house will be supplied from mains as we are used today. Do you think this is enough simple story acceptable for students?
What are possible ways of converting sun energy into electrical and how to control energy flow?
To achieve the house consumption stay on set point, a student must get an idea of devices and possible energy flows within those devices. In the picture below both the devices and the possible energy flows are shown. Here we will not explain more deeply the picture, anyone who is reading this blog is familiar with those devices and basic operation principles. Of course for students, there should be added „some words“ more!
Educational Energy Storage System based on Victron ESS
For the first set up Schrack Technik decided to prepare a „minimal“ configuration based on Victron ESS which will enable demonstration of power electronic components, energy flows, and strategy for control house consumption from mains. Because of simplicity, it was decided not to apply a grid inverter for the first model set up, but it can be applied anytime – the model housing is managed in this way too. Also, a single-phase-based ESS is built instead of a full three-phase ESS. For education, single-phase ESS is enough to show the strategy of house mains consumption control!
Model set up
Schrack Technik model set up is arranged as the mobile one. That simply means that housing has wheels, so this model can be driven from classroom to classroom. In the classroom should exist 5 pole mains wall connection (L1, L2, L3, N, PE – full TN-C-S connection) to connect mobile set up on mains. This model emulates also a typical house with its own house loads connections. Loads could be connected to all phases and to Multiplus II output. This setup can demonstrate the way of operation without mains too. Photovoltaic modules can be connected to the system, but instead of them, a power supply (voltage source with current limitation) can be used too. This is of importance because during the lecture it may be cloudy and PV modules could be too weak to start to produce electrical energy. But for lecturing with a power source one can get sun PV modules simulation anytime! Devices are hanged on all three sides of the housing, the fourth side is foreseen for the grid inverter option. Battery monitor, Color control, and digital Multi control are situated on transparent elevating top table enabling to have insight view to backside wiring.
Electrical set up schemes
In the next two pictures, there is a detailed scheme of setup: power part and communication part. What is here non so typical is the battery monitor and color control supply connection. The supply of these devices is connected after the main battery switch. So when the LFP batteries are switched off no current is drained from them. This is for safety reasons because models are mobile and they will not be permanently connected on mains. If most of the time model will not be switched on mains, then the LFP battery should be switched off from any load. What is inside:
– Multiplus II 24/3000
– Smart solar MPPT 150/100 VE.Can
– Color Control GX
– Energy meter EM 24
– 2 x LiFePO4 Batteries 12,8 V/100 Ah smart
– VE.Bus BMS
– BMV 712 Smart
– 2 Lynx power in
– Digital multi Control
– together with all necessary fuses, switches, protections, cables, and covers
Schrack Technik d.o.o. donated three schools in 2020. with such mobile educational ESS. For 2021. they plan to supply the next three schools. All the teachers involved are introduced so they can exchange experience, working materials, and ideas for practical exercises. Schrack Technik did start lecture to teachers and now it is their turn to promote house consumption control to their students. All teachers get administrator access to their installations on the VRM portal. Schrack Technik believes that a lot of students will accept and remember the idea of mains house consumption control. They will learn how simple it can be commissioned and inspected on the VRM portal and how useful is to control house consumption from mains. Playing with such a simple system will encourage young future installers to make them free of any fear from PV installation!
High school Konjščina
High school Konjščina is a vocational school, founded 70 years ago as a mining school, in Krapina-Zagorje County, in the small town of Konjščina with about 1000 inhabitants. The school is currently attended by 270 students. In the field of electrical engineering they educate students for three professions:
-technician for electrical machines with applied computing (4 years),
-general electrician and car electrician (3 years).
Four committed young teachers are realizing electrotechnical subjects: Ivana Smetiško, Dalibor Smetiško, Mario Varga, Milan Havoić. They invest do-it-yourself work in the continuous improvement of the teaching process to enable their students to acquire the latest knowledge and skills in the field of electrical engineering. They already have a well-equipped classroom for teaching electrical drives and two electrical laboratories for exercises in various electrical installation types. A donated mobile educational photovoltaic energy storage system will be used in teaching renewables. On Victron equipment, they will organize exercises like Photovoltaic system wiring, Measurement, and analysis of basic parameters of a photovoltaic system, Management and adjustment of photovoltaic systems, Connecting the photovoltaic system to the electrical grid, Functional testing of a photovoltaic system, Application of photovoltaic system in SmartHome installations – creating a model of a complete energy independent house with the use of “open source” technology (Arduino, Raspberry Pi, VidiX)… Currently again with a help of Schrack Technik d.o.o. they are building the new “Schrack electrical laboratory” with the wish to be the local center of competence for renewables.
Electro-mechanical vocational school Zagreb
Electro-mechanical vocational school founded in 1960 has today more than 600 students organized in 30 classes. Students are educated in two fields in 3 or 4 years programs:
- Electrical engineering: electrician, electromechanical;
- Mechanical engineering: automechatronic, car mechanic.
Students have weekly alternating theoretical and practical lectures. They acquire practical knowledge and skills in laboratories for exercises in electrical supplies, specialized workshops for mechanical items such as the Ford and Renault practicum for car mechanic/electric, and richly equipped workshops for electrical installations and electromechanics.
There are three enthusiastic teachers Damir Čolig, Ratko Harausek, and Mladen Klobučar lecturing renewables. Schrack Technik already helped them in a student project of one old van VW T3 Caravella transformation to be a mobile self-powered stand with a solar system. The vehicle is in use for school advertising events like World skills competition Croatia and Craft fairs. The donated mobile educational photovoltaic energy storage system will enrich their workshop for Electrical Installation for 3rd-year students. Up to now the renewable energy sources is lecturing for 6 theoretical lessons and several laboratory exercises. With the new mobile system, they will expand their both practical and theoretical lessons to more than 24 practical and theoretical lessons with completely new topics around the Victron energy storage system.
Technical school Daruvar
Technical School Daruvar, as a trade school, continues trade education tradition in city Daruvar from 1887. The current formation of the Technical school is dated 1992. They offer 4-year programs for technicians for electronics, mechatronics, road traffic, and computer science. Shorter 3-year programs are for: mechanic, installer of heating and air conditioning, electro installer, and CNC operator. There are also programs for special educational needs students too.
The school has 474 students organized in 30 different classes. Besides regular and practical education, there are multiple extra-curricular activities in the school. Last year their students get No 1 position in the Robo2020 international competition, and this year they get No 2 position in the same competition.
Renewables are lectured mainly by Mario Havranek and he will use donated mobile educational photovoltaic energy storage system in his lectures. He believes that this setup will help to better understand solar energy meaning in the Nearly Zero Energy Buildings transition. With this donation Technical school Daruvar will enable students studying for technicians for mechatronics and electro installers to finish on up to date equipment their laboratory exercises in Renewable energy sources subject.
Brochure – a gift for everyone – Photovoltaic systems with examples from praxis
Al three schools get a cost-free Schrack Technik brochure: Photovoltaic systems with examples from praxis. This brochure has 416 pages (is written in Croatian!), is based mainly on Victron power electronic products supplemented with Schrack Technik energy distribution products, and is cost-free available from any having interest. In the last 5 years, 3000 pcs of this brochure were distributed.
The most interesting articles from the brochure are on Schrack Technik web site too: https://www.schrack.hr/know-how/alternativni-izvori/
Technically refined articles are on Schrack training center: https://www.schracktrainingcenter.com/wiki-schrack-training-center/
In December 2020 Schrack Technik had Student Info day with an online lecture about the model set up described above for more than 15 schools and 250 attendees: https://www.schrack.hr/vama-na-usluzi/schrack-info-dani/info-dani-2020
Tekst priredio: [email protected]