Increasing the efficiency of Off-grid (Autonomous) Photovoltaic Systems and maximizing the utilization of solar energy by controlling the electrical equipment in the autonomous controlled environment.
Solar renewable energy systems are becoming part of everyday life.
Development of various technologies has allowed the creation of sufficiently powerful and reliable power generation systems to meet the needs of an individual house or cottage, without being connected to the electrical grid.
Off-grid photovoltaic Stand Alone (Autonomous) Electric Systems are designed for independent power supply of individual residences. Such systems create a separate standalone electricity supply network with compliant standard 230V AC 50 Hz and can usually provide consumers with a range of capacities from 10 to 10,000 Watts. Off-grid Photovoltaic System converts sunlight into electricity and store it in batteries for later use.
Practical aspects of Off-Grid PV Systems operation are predefined with objectified reasons of the following character:
- Sunlight is available during a limited time during the day, and in addition can be obscured,
- Solar Panels can generate a finite amount of energy,
- Timetable of energy consumption does not always match the energy production timetable,
- Battery's charge is finite because batteries have finite capacity.
The points above also describe the disadvantages of such electricity supply model.
The ideal case of energy utilization, generated from solar panels, is when the energy is consumed by maximum during its generation phase and provide a steady charge of batteries for future minimum use. The general concept when the energy produced during the day in stored in the batteries and then primarily used during evening and night hours does not only put a big strain on batteries, but also is not an efficient way of the energy utilization.
The thing is that not all the energy produced can be store in the batteries. In addition, the process of charge and discharge is known for major energy loses. We believe that the efficiency of such standard scheme cannot exceed 70% of the solar panel production potential.
Furthermore, if the batteries are fully charged, but the sunlight is still available, the solar panel energy production potential is not utilized anymore, because is it being completely discarded.
For example, in situation where there is no one at home during the daylight and timely use of energy production by the panel is not happening, these losses are happening systematically. The thing is, when the batteries are reaching their maximum charge capacity, the charger begins to limit the supply of the energy from panels to the batteries.
Modern charges are getting even better and more effective.
Newest and the best models are actively interacting with solar panels with Maximum Power Point Trackers technology. Such as Steca MPPT Solar Charge Controller MPPT 6000.
The question how not to lose this energy and use all possibilities of such equipment is being solved by engineers of Rosstek Limited/Laboratories.
The company Rosstek Limited has developed world's first distribution system of electrical energy for an individual stand alone residential house equipped with Off-grid Photovoltaic System.
The company Rosstek Limited specializing in development and installation of renewable energy sources projects, has large experience working with Off-Grid Photovoltaic Systems, and understands the subject well. Rosstek Limited engineers have questioned how to fully utilize the energy of the sun without human interaction or supervision and to pump the efficiency of Off-Grid Photovoltaic Systems to its maximum potential, closing to 95-97%.
As a result of years of work, a project of electricity distribution system for Off-Grid Photovoltaic System was developed in individual residential house based on “Smart Home” idea.
In cooperation with engineers from Rockwell Automation the necessary equipment was selected based on Allen-Bradley PLC technology and the control system for the distribution of electrical energy was built for a residential house powered by Off-grid Photovoltaic System.
The system's operation control principle is based on calculations of energy flows and the need of battery charge.
Providing a full battery charge, the controller directs the available free energy for utilization by household consumers.
At the same time maximum use of energy produced from the sun by solar panels is used while the batteries are not being discharged.
Lowering the strain on batteries means extending their life time span and their reliability. Long life and health of batteries are very essential during Off-Grid Photovoltaic System exploitation.
At this time for the operation of Off-Grid Photovoltaic System specially developed gel batteries with solid electrolyte (dryfit technology) are being used; their virtually do not require maintenance. For example Sonnenschein SOLAR batteries made by GNB Industrial Power – A division of Exide Technologies.
Sonnenschein SOLAR batteries are specially designed for small to medium performance requirements in leisure and consumer applications.
Good results were obtained when using HOPPECKE OPzV solar.power batteries.
Such batteries are not cheap, that is why their part in complete system's cost is significantly high. The subject of life time extension and stability of operation of such batteries is very relevant.
Methods of use of the available energy may vary, depending on the house equipment and environment is it set in. In winter time the energy may be directed to heating the water, operation of central heating system, such as underfloor heating and other. In summer, the energy may be directed to the functioning of Air-Conditioners, swilling pool water pumps and other.
Capabilities of the control system are broad and only limited by imagination.
Everything from a simple ability to light the house internal or external lights at a specific time, to a complex ability of launching pre-programmed household equipment at specific time (and interval, or based on energy excess and other factors).
After the development of the project, practical adaptation of the system took shape.
Experimental installation was constructed by company Rosstek Limited in year 2014 and launched in trial operation on a separate cottage equipped with Off-grid Photovoltaic System and specially adapted to “Smart Control System” by Rosstek Limited.
Electrical equipment used in the system, chargers and inverters, is manufactured by German firm Steca Elektronik GmbH, a leading manufacturer of components for Off-grid photovoltaic systems and chargers for the batteries.
Batteries used in the system were the rechargeable batteries Sonnenschein SOLAR batteries manufactured based on dryfit Gel – VRLA technology.
Control system is designed constructed/made based on components from Rockwell Automation and programmable logic controller from Allen-Bradley, use of PLC software by Rockwell Automation and utilization of MODBUS protocols is implemented.
The system allows the direct immediate control of house energy consumption in all circuits seamlessly for the user and additionally provides the user with current information on a built-in monitor. The information is provided with both digitally verbal and graphical visualizations. The system constantly takes measurements of energy flows and system operations and stores the information data into databases for future references and analysis.
The system is calculating the energy production from solar panels and energy consumption in user-defined household circuits.
The system provides priority battery charging, power supply of all user-defined circuits and devices in the house, such as lights, fridges, TVs, computers and kitchen appliances.
Control of house climate control systems and secondary equipment reside in Automatic Mode. During the winter the Underfloor system was used, based on infrared thin film technology by CalorIQue.
CalorIQue technology, developed globally for alternative renewable energy sources and efficient use of energy, was incarnated in flexible film electric radiant heating, which maximizes the efficiency of the conductive properties of the elements carbon.
Periodically occurring excess energy channeled additionally for heating the hot water tank of 500 liters. Also, the controller controls the operation of the swimming pool pump.
Users is always able to go to manual control of any object/circuit/device and can either turn it OFF or ON manually forcibly.
The interface of data transfer to personal computer or any mobile device is also developed, with the ability to view any information regarding the currept operations of the system.
As a result of the pilot operation the system showed very high effectiveness of usage of generated energy by solar panels and practically reached the required margin on 97%.
This resulted in higher amounts of energy provided for the house without increasing the potential productivity or equipment of the Off-Grid Photovoltaic System.
In this way the cost of produced energy got lowered and the return of financial investment in the installtion of Off-Grid Photovoltaic System rose.
In addition to improving technical indicators, we have improved consumer qualities of the whole house and increased comfort for the people living in the house.
The consumers are greatly reliefed from concerns regarding the control of their household equipment and they need not to worry about constant observation of energy availability.
Now the owners can easily go on vacation or urgent matters, leaving their house in the hands of the controller, which will see to comply with pre-set conditions of proper house maintaining and precise utilization of energy.
Rosstek Ltd.