GRID CONNECTION IMPROVEMENT OF THE BIOGAS POWER PLANTS BY USING AN ADDITIONAL WIRELESS COMMUNICATION SYSTEM O. IONESCU, L. BULAREANUN, B. LAZAROAIA, H. ANDREI University "Valahia" of Targoviste Aleea Sinaia, 13, Targoviste, Dambovita, Romania E-mail: ionescu_o_ro @yahoo.com, bulareanulucian@yahoo.com, bogdan.lazaroaia@gmail.com, hr_andrei@yahoo.com Abstract. The new developments in the production of renewable energy brought significant challenges both to the producers and to the transportation and delivery electrical grid. Although for the wind and photovoltaic power plants there were developed comprehensive sets of regulations, for the electrical power generated based on biogas there it is still not covered by any specific regulation. The production of biogas through the biomass anaerobic fermentation could become a dangerous process if the electrical power is missing during the process start up, when the O2 and CH4 is in the ratio favorable for explosions. In this article is presented a wireless system developed as a redundant pathway for SCADA system used by the grid operator in order to connect /disconnect the producers of renewable energy during grid faults. The system was developed based on authors experience acquired during the implementation of Genesis Biotech cogeneration production plant based on biomass (corn silage) at Filipestii de Padure village, Romania. Figure 1. The current situation of biogas plants in Germany [4]. Keyword: cogeneration, biomass, wireless, grid connection. 1. INTRODUCTION The cogeneration power plants based on biogas are one of the main assets of a reliable distributed smart greed, providing the reserve of renewable, controllable produced electrical energy. In this regard should be mentioned that countries with advanced experience in production of renewable energy are well balancing the difficult to predict wind and photovoltaic energy sources with controllable biogas/biomass plants with goal of achieving a functional electric grid. As a relevant example Germany is Europe's biggest biogas producer [1], in 2015 there were 8,700 biogas plants operating throughout the country and the total installed electrical power capacity of these facilities was around 4000 MW [2] as presented in the Figure 1. The processes behind biogas production are quite simple consisting in biomass degradation by a group of anaerobic bacteria. There are several biogas plants configurations their design being adapted to the specific properties of the biomass used. For the Genesis Biotech Plant was chosen the design developed for corn silage as presented in Figure 2. Figure 2. Genesis Biotech cogeneration plant at Filipestii de Padure village [3]. The key behind the process fermentation is to provide an effective steering of the substrate into the digesters in order to avoid separation of the liquid phase and solid phase of substrate thus the apparition of floating lid which would stop the fermentation process. There are several key sequences during the fermentation start up process which could lead to disasters such as digester explosion or fermentation interrupts. If during these moments the electrical power is missing for long a period due to major faults of the grid and/or the intervention team of grid operator is not able to fix the grid fault then the control of the fermentation process could be lost. 2. CONNECTION TO THE GRID The solution provided by the grid operator for connecting Genesis Biotech cogeneration plant to grid is presented in Figure 3. 11
Scientific Bulletin of the Electrical Engineering Faculty Year 15 No.3 (31) ISSN 1843-6188 authorized by the operator could access and operate the connection point, and in addition, any operation conducted in the connection point should be supervised by the operator s Dispatcher. Consequently, the developed system shall provide a wireless method which would exclude the access of energy producer personnel into the connection point. Figure 3. The connection circuit for Genesis Biotech [4]. The connection point P.C. 6012 has the possibility of switching between two medium voltage (MV) lines Moreni 1 / Moreni 2, thus there it is a big advantage since this system is providing an alternate pathway of delivering the produced energy during the existing faults on one of the two lines. The only remaining problem is that whenever faults happen, the probability that the equipments of the GSM provider are not working consequently there it is a need for a technical team to access the connection point and to switch the lines. Although the grid operator needs a diesel power generator as a energy reserve energy supply what can be more expensive. A brief calculation was conducted as could be seen in the Table I in this regard and it was concluded that a 250 KVA generator shall be purchased in order to fulfill the needs of the plant. Table I. The list of consumers in the biogas plant Consumer Number Nominal power [kw] Digester 1, fast mixer 2 18.5 Digester 1, slow mixer 1 12.6 Post digester, fast mixer 1 18.5 Post digester, slow 1 12.6 mixer Storage tank, slow 4 18.5 mixer Feed stock feeder 1 37 Substrate pump 1 7.5 Fans 3 0.12 Condensate drainage 3 0.7 pump Spillage pump 1 1.9 Heater circuit pump 3 0.41 Auxiliaries 1 5 Mixing tank pump 1 3 Total 215 3. ARCHITECTURE OF PROPOSED COMMUNICATION SYSTEM In order to develop a communication system that could be accepted by the electrical grid operator FDEE Electrica Muntenia Nord it was establish from the beginning that any personnel excepting the one The provider of GSM radio link for the grid operator FDEE Electrica Muntenia Nord is Vodafone Romania; therefore the proposed parallel radio system shall insure the compatibility with other providers such as Orange, Cosmote, RomteleKom etc. Another request is to provide an alternate link through an independent high power system Wi-Fi or ZigBee (coverage around 23-50 Km). There are two different topologies of the networks to be established within connection point and grid operator dispatchers: a) A line type architecture consisting of ZigBee emitters-receivers pairs disposed on 20kV masts generating an independent chain between the dispatcher, connection points and the producer as presented in Figure 4; Figure 4 In line system for data transmission b) A radial structure consisting in direct links (GSM/GPRS) between the dispatcher, connection points and the producer as presented in Figure 5. Figure 5. Control system with radial architecture Taking into consideration that the differences related to hardware equipment are minimal and the implementation costs is quite low in comparison with the amount of money lost while an accident happens it is preferable to 12
use a parallel system including both presented architecture thus providing a more reliable system. The proposed system has the benefit that is adaptable and easily configurable according to the grid requirements being possible to integrate a large number of producers in real time. In order to avoid misunderstandings regarding the degree of intrusivity and the limits of settlement of the producer as against with the role of the dispatcher it was developed a logical diagram for the activities/events controlled by the proposed system and the operator dispatcher. This diagram is presented hereunder in Figure 8. The system to be developed could use for the dispatcher side an open platform based on GSM module SM 5100 B presented in Figure 6. Figure 6. SM 5100 M GPS/GPRS modem End user could configure its specific application based on SM 5100M modem through the development platform DSB 75 and after concept validation the module would be easily mass produced. A peculiar situation is foreseen for areas where the GSM/GPRS coverage is missing. In this situation a mix between the two systems ZigBee and GSM/GPRS could offer a reliable solution. The ZigBee emitters/receivers pairs would be installed on medium voltage masts from the power generation plant to the closest place were the GSM coverage is present and from there the GSM modem would provide the link with the electrical dispatcher. The data transmission sequence in the proposed system is presented in the following diagram, shown in Figure 7. Figure 8. Logical diagram for the controlled activities As presented in the previous diagram the producer does not have any access in the process of connecting/disconnecting the power plant to the grid, all the control capabilities are allowed to the operator dispatcher. If the remote control system does not work properly or if the GSM radio link is interrupted the dispatcher is relaying only on subordinate intervention team which has to deploy to the connection point and manually operate the switches. Depending on the situation this process could be fast if there are not serious problems with the grid or it would take days when storms are affecting the grid. 4. PRACTICAL DEVELOPMENT Figure 7. Data transmission sequence The previously presented architecture has a large degree of flexibility providing a platform which could be adapted for each project requirements. For the Genesis Biotech installed at Filipestii de Padure village we have developed the connection system presented in the block diagram in Figure 9. In black are presented the existing connections and in red the additional connection proposed. Due to the fact that the distance between the connection point and power plant is quite small it was decided to make the connection by wire and between the dispatcher and power plant / connection point by GSM. 13
Scientific Bulletin of the Electrical Engineering Faculty Year 15 No.3 (31) ISSN 1843-6188 Figure 9. Bloc diagram of the proposed connection system The modification inside of the connection point (PC) is minor and the schematics are presented in Figure 10. Figure 12. The prototype installation 5. CONCLUSIONS Figure 10. Schematic of modification inside PC In order to easily develop the prototype system it was decided to use a development board equipped with an ATMEL controller (ARDUINO UNO) [6] easily to be interfaced with GSM Modules. While for the dispatcher it was proposed the use of SM 5100 M GPS/GPRS modem for the connection point and power plant were chosen less expensive modules Quad band SIM900, shown in Figure 11. By using this system there could be received / transmitted data such as SMS messages between any computer / mobile phone and the ARDUINO board. Based on conducted analysis it could be foreseen that in the next period of time there it is a great potential for the development of cogeneration plants based on biogas. This is based on existing high potential in regard with the existing biomass in Romania as well as on the need for controlled sources of electrical power required to balance the development of photovoltaic and wind power plants. The SCADA DMS implemented within the grid operators facilities could not entirely support the needs of reliability required by the biomass production plants. There are dangerous situation which may occur in the process of start up of biogas plants such as: - Solid phase separation and generation of a lid which stop the fermentation (bacteria are dying). The expenses required for re-start the process are around 2000 Euro and furthermore the time that the plant is not operating may account for 300.000 EURO lost (10.000 EURO /dayx30days). - If the grid fault occurs when the report between O2 - CH 4 is equal at the molar level (some 12% methane in normal air) the danger of explosion is very high. The only method of increasing the reliability of the monitoring and control the biogas production plant is by providing the electrical power supply continuously. This issue depends mainly on the stability of the link between the dispatcher and the connection point. Providing a redundant radio channel is increasing the reliability of the system consequently is a viable solution. Figure 11. Quad band SIM900 for ARDUINO The installation of prototype [5] is presented in the Figure 12. The proposed system could undertake the specified function increasing the reliability of the link. This is proving the concepts that parallel redundant are characterized by an increasing reliability. The conducted tests were successful; the system was working in an independent mode by using the ORANGE GSM provider network. As a result of implementing this 14 12
system it was observed a reduction of faults solving time with 50%, consequently an increase of production time with 30 hours/month. 6. REFERENCES [1] *** http://www.european-biogas.org, "European Biogas Barometer" (PDF). EurObserv'ER. Retrieved 7 November 2015. [2] ***http://www.biogas.org/edcom / webfvb.nsf/ id/de_ Branchenzahlen/$file/15-11- 19_Biogasindustryfigures_2014-2015_english.pdf retrieved 20 December 2015 [3] O. Ionescu, C. Popescu. Technical design of the Genesiss Biotech cogeneration plant, 2010. [4] B. Lazaroaia, Technical design for connecting to the grid Genesis Biotech Filipestii de Padure cogeneration plant, 2010. [5] L. Bulareanu, Studies and realization of a system for biogas plant producing electrical energy to the SEN, Licence disertation, UPG Ploiesti 2015. [6] *** http://www.sainsmart.com/ sim900-gprs-gsmboard -quad-band-module-kit-for-arduino-highquality-new.html acessed december 2015 15