Energy Consumption Optimalization
Weather forecast based control
When creating a control strategy, information on weather conditions during today or the next day are very helpful. It will help to compensate the heating system time delay. RcWare Weather, a service that acquires the weather forecast data, is able to bring these values into the control system. There are 12 values computed at the server level: wind speed and direction, minimum and maximum temperatures, precipitations, air humidity, air pressure, cloud covering, etc. All values are forecasted in a mathematical model for any location in Europe*) with additional extension to other regions as an option. The variables adhering to one licence are then bound to the geographical coordinates which were entered when the licence was ordered.
Each variable carries the information on how many hours in advance it should be computed; time periods from 1 to 48 hours are used. It is also possible to declare more variables in the system, which forecast one value with different times, such as outside temperature changes within the next hour and/or within 6 hours. The most utilized value is temperature 2 meters above ground, e.g. for heating curve optimization which prevents overheating (if outside temperature rise is expected, the heating water temperature is controlled to a lower forward temperature in advance, so that the energy is not wasted in the system), or for cooling accumulation control strategy.
Predictive control of technologies
A MPC (Model-based Predictive Controller) uses weather forecast and mathematical model of the controlled building to minimize the planned energy consumption while keeping the required indoor comfort level. Thanks to high performance of today’s technologies, it is possible to compile a model of the building, then calculate the trends of indoor temperatures based on measurings of indoor and outside temperatures together with other values, such as solar irradiation and wind speed. The computations take place at remote servers; only the setpoints are communicated to the PLC, such as hot water temperature setpoint.
Predictive control has been tested in cooperation by companies Energocentrum Plus s.r.o. and Feramat Cybernetics s.r.o. at the Czech Technical University campus buildings, using SoftPLC control software, where heat consumption savings achieved 26 %. A similar MPC project was executed in Hasselt, Belgium, in the Hollandsch Huys building.
The load shedding controller limits the 15 minutes electrical energy consumption so that the agreed limit is not exceeded. Unlike commonly used systems, it is able to monitor the operation of currently active groups over contact inputs or a communication bus. Non-operating groups will then be skipped. All actual values and parameters are accessible over a LCD display, communication bus, SCADA, or web interface: they can be changed dynamically. The web pages also show last 15 minutes consumption, and consumption trend in time.
The controller is freely programmable. The application software may be adapted according to the requirements of a particular installation. It is possible to set maximum off times, minimum on times, and other parameters of 8 groups. The complete load shedding system is easy to integrate into a building control system or 3rd party programs, e.g. SCADA or ERP system.
Thanks to its open system, Domat offers many possibilities how to read values from energy meters: from interfaces with web access over a freely programmable DDC process station to data acquisition into powerful databases with open interface for 3rd party applications, such as invoicing and cost allocation systems. The process station may perform other functionalities, like peak shaving in district heating networks. All commonplace meters with M-Bus or Modbus interface are supported, and for the system it is no problem to integrate heat meters together with water, gas and electricity meters and thus provide a complete overview of energy consumption in a building or technology – regardless if current values, or historical data.
We always select the solution which fits the task best. For hundreds of small-scale technologies (heating stations, retail shops), a small communicator with Internet communication is often used. At larger projects, like blocks of flats and office buildings, a process station with 4 ports for up to 1000 metering devices is a more suitable solution. Again, the process station may perform precalculations if necessary, which may decrease the amount of necessary meters, or provide more detailed consumption data. Together with energy data, information about operation of technologies may be recorded, so that the energy manager is able to evaluate the situation and optimize the configuration of machinery and other technologies.
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