Ground Source Heat Pump in Heating System with Electronics Monitoring

Ground Source Heat Pump in Heating System

with Electronics Monitoring

NEAM U Ovidiu

, RO CA Marcel

, BENDEA Codru a

, CODREAN Marius

1

University of Oradea, Romania

Department of Electronics and Telecommunications, Faculty of Electrical Engineering and Information Technology, 410087 Oradea, University Street 1, ROMANIA, E-mail: oneamtu@uoradea.ro

2

University of Oradea, Romania Department of Energy Engineering

Faculty of Energy Engineering ,

410087 Oradea, University Street 1, ROMANIA, E-mail: mrosca@uoradea.ro

Abstract –The monitoring system is implemented for a ground coupled heat pump in heating/ system. The borehole heat exchangers – which are 150 m long - are filled with a mixture of water and ethilene glycol called brine. Metering and monitoring energy consumption is achieved for: heat pump, circulation pumps, additional electrical heating, hot air ventilation systems, control systems with sensors: analog and smart sensors. Instantaneous values are stored in a local computer.

Keywords: FPGA; ground energy; smart sensors; controller.

I. INTRODUCTION

A modern building integrates a thermal heating in winter. This may be done through pipes mounted on walls. An electric resistance is used only as compensatory measure in extreme cold conditions. The heating system uses energy from the ground. It has a vertical closed-loop called borehole heat exchanger, placed into the ground to a depth of 150 m. It consists of a U-tub of high density polyethylene pipe. A circulation pump is used to circulate the brine that transfers the heat from the ground to the heat pump evaporator. The on/offs of the circulation pump is done only under certain conditions imposed by the controls.

The electricity consumption is monitored for: - the compressor of the heat pumps – where heat is transfered from the ground circuit to thermal buffer circuit;

- Circulation pumps;

- Additional electrical heating used in extremely low temperatures - heating resistors;

- Hot air ventilation;

- Control systems with analog sensors and smart sensors. Electronic monitoring system is to improve control algorithms and tuning of the control system for circuit

assembly to ensure optimum thermal comfort of the a building. It is evident tendency to reduce costs through more efficient electrical and electronic equipment.

II. ADVANCED HARDWARE SOLUTIONS

For this purpose we used an FPGA cRIO NI latest generation product. The monitoring system has a central unit that are compounded electronic boards for measuring quantities from analog and digital sensors. There are classic analog sensors for temperature, humidity, light radiation. The digital sensors are utilized for the present thermal agent in heating circuits.

Fig. 1. FPGA cRIO NI with power suppy and electronic boards

The system is equipped with apparatus Fig.1. for measuring heat and electrical power. They are smart sensors with their metering systems, display and communication. Measured data is transmitted through cRIO serial interface.

Monitoring software is developed in LabView NI cRIO system and communicates with a computer. The NI cRIO-9074 integrated system [5] combines a real-time processor and a reconfigurable field-programmable gate array FPGA within the same chassis for embedded machine control and monitoring applications. It integrates a 400 _____________________________________________________________________________________________________________

MHz industrial real-time and has eight slots for NI C Series I/O modules.

System for heating integrates: communications (LAN, Web), intelligent sensors, analog expansion boards applied, digital boards for electric drives and electronics.

Fig. 1. Power suppy for Electronics Ground Heating System

All information is taken from the heating system, including heat pumps. Strategies are provided for control algorithms depending on features. External environment, climate, soil temperature, outside temperature parameters are useful in the optimization of environmental control in buildings and in substantial savings to the costs was heated in winter and cooling in summer.

A. Power supply and metering

Fig. 3. Power suppy metering and common bus for serial data transfer

There are two three-phase circuits Fig.1. for power supply: one compressor "a2" and one for electric resistance heating. Switch S3 is controlled by the heat pump through a controlled depending on the ambient temperature conditions of the building.

The power supply [2] is measured by way of measuring transformers: T1, T2, T3. They are connected to the electricity meters.

There are several meters under the functional integration of FPGA system.

B. Communication electronic devices with the cRIO The National Instruments cRIO has a serial interface RS 232, but electronic devices for metering electric energy and thermal energy are equipped with electronic interface for the serial, RS 485.

Fig. 4. Communication electronic devices with the cRIO

The solution for the adaptation of data transmitted to the cRIO, is to use a data converter RS-485/232. This creates a common bus for serial data transfer with NI cRIO system. It use 3-wire shielded without + Vdc supply.

C. Temperature measurement

The National Instruments cRIO is supplemented with circuit boards expansion. One of these NI - 9217 is dedicated for analog quantities Fig. 4, from the sensor.

They are direct analog measurements. In the cRIO system, analog quantities are introduced in Analog/Digital converters. Data are the result of the analog measurement. Later this data will be dynamic evolution measurements. _____________________________________________________________________________________________________________

Fig. 5. Communication electronic devices with the cRIO NI.

It use two thermal linear sensors for ambient temperatures. Their names are determined by the location allocated: inside and outside. Remaining channels are available in NI-9217 board for various optional sensors.

Fig. 6. Indoor and Outdoor Temperatures in dynamic evolution measurements

Thermal energy meters are designed for measuring of thermal heat energy in heating and cooling systems. The electronic unit has connectors for temperature sensors and performs the calculation and integration of volume and temperature difference.

Flow sensors works electronicaly. The measuring method is based on Faraday’s magnetic induction, where the water movement induces a voltage across the electrodes. Is used at high precision measuring of flow.

The flow sensor’s temperature operating range covers from -10 °C to +120 °C.

Fig. 7. Thermal energy meter

The thermal energy meter is calculated according to European standard EN 1434, which simplified can be summed up as follows:

(1)

V = the water volume

is the mean k = enthalpy (the water heat coefficient).

Fig. 8. In and Out Temperatures in External Circuit Temperature.

Temperature evolution can be seen in Fig. 8. for external circuit pipes installed in the ground. For the internal circuit of the walls of the building heating, temperature evolution shown in Fig. 9.

The heating is performed at the University of Oradea. Evolution of temperatures, in this paper, is followed for one spring day. Environmental factors, imposed control algorithms, that have been transferred to soft.

A first program configures the sensor parameters. Unique identifiers are assigned for the smart sensors so that they communicate to the system cRIO NI.

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Fig. 9. In and Out Temperatures in Internal Circuit Temperature.

Fig. 10 External Pump Electrical Power.

Fig. 11. Heat Pump Electrical Power. in dynamic evolution measurements.

Heat Pump is equipped with its own electronic controller. Electronic control is PID Proportional Integral Derivative. It is implemented in software.

Fig. 12. External Circuit Thermal Power. in dynamic evolution measurements.

Electrical power consumption of the circulation pump Fig.10. or heat pump consumption Fig.11, is much smaller than the Thermal Power Fig.12. obtained from the ground.

III. CONCLUSIONS

Heating system. was created under the project FP7 groundmed. The consortium GROUNDMED are 24 research partners from 14 European countries and manufacturing.

The system provides heating of a building. It is a unique implementation at the University of Oradea. Some electronic and thermal modules were used to increase the reliability and accuracy of measurement. We solved. the compatibility of the data transfer. There are sensors and smart appliances that communicate with the local PC.

Developed software is created in LabView. The objectives are focused on the electronic structure of the management of interactive sensors and ac power operation. The system has safety subroutines and a very good reliability. It works in real-time for electronics devices, measurements and Ground Heating with Electronics Monitoring.

A high level software has functional predefined bloks for fields of interest; industrial electronics is a possibility. Considerations regarding the practical implementation of the proposed solution and some experimental results are also given.

REFERENCES

[1] Agelidis, Olimpo Anaya, Olimpo Anaya-Lara, T. J. E. Miller, Power Electronic Control in Electrical Systems, Newnes, Oxford, 2002.

[2] Bikash Pal, Balarko Chaudhuri, Robust control in power systems, Spinger, 2005.

[3] B. K. Bose. Power electronics and variable frequency drives, Ed. by IEEE, New York, 1997.

[4] William Shepherd, Li Zhang Crowther, Li Zhang, Power Converter Circuits, CRC Press, New York, 2004.

[5] * * *, ni.com, Real-Time NI CompactRIO, 2013.

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