The mina concept
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- Bu səhifədəki naviqasiya:
- Keywords: renewable electricity, demand side management, domestic refrigerator 1. Introduction
- 2. The Unit Commitment Problem
- 3. Using RC, RRC and Smart Metering DSM technologies for balancing
- 4. Domestic refrigerators in operation
- 5. Test measures on the field of “The mina Concept”
- 6. Conclusion
- 7. References
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New chance for renewable electricity sources - managing cooling devices based on “The minA Concept”
2 Széchenyi István University/Department of Transportation Engineering, Győr, Hungary 3 Eötvös Loránd University of Sciences/Faculty of Informatics, Budapest, Hungary 4 University of Maribor/Faculty of logistics, Celje, Slovenia Abstract— Renewable electricity production has the promise to be able to provide the energy for our economies on a sustainable way. There is a strong need for “green logistics” solutions worldwide, as transportation requires “green fuels” (bio-fuels, green electricity and/or hydrogen, etc.), and the facilities alongside the supply chain (factories, warehouses) require green electricity sources. The availability of these renewable sources is not predictable, so the integration of renewable energy production into the load levelling control of the National Grid requires special solutions. There are some technically possible, but not financially feasible electricity storage options today, and we can also use some DSM (demand side management) methods we are presenting in our essay. Keywords: renewable electricity, demand side management, domestic refrigerator 1. Introduction Electricity-driven cooling is one of the most important consumer profiles – the world is using more and more electricity for these purposes (residential, industrial). The logistics industry has huge cooling energy demand as there are many storage locations and transport actions “from the field to the table”, and there are cooling needs to keep the products in fresh and good conditions during logistics activities. Cooling demand has year-by-year growing part in total electricity consumption, especially summer time. Industrial cooling is not changing as much during the year, but the electrical power need for the same cooling energy is increasing in this period, because ambient temperature is higher. There were many new air conditioner installations in residential areas and bureaus, offices, shopping centres in the previous decade, so the summer peak electricity demand reaches nearly the winter maximum (Földesi, Bódis, Bajor, 2012). “The minA Concept” is based on our wire-logistics approach: according to the real nature of the cooling demand through the supply chain it is possible to provide electricity infrastructure savings. Applying “The minA Concept” as demand side management technique in modifying the daily load profile of the electricity network can help system operators in shifting the supply system to a more sustainable state. In the actual phase of our research at Szabó-Szoba R&D Laboratory at Széchenyi University Győr we are focusing on the control of a domestic refrigerator to prove the feasibility of the concept. In our essay we present the test procedures and the results of the measures. 2. The Unit Commitment Problem The power and energy industry – in terms of economic importance and environmental impact – is one of the most important sectors in the world since nearly every aspect of industrial productivity and daily life are dependent on electricity. Renewable energy provides clean and sustainable approach to energy production, helps to ensure security of energy supply, and contributes to the meeting of the Kyoto Protocol objectives. From the customer side, availability of electrical energy is indispensable - the main function of traditional electricity supply is to serve the consumer demand with solidly available (security of supply) and satisfactory (quality of supply) electrical energy (with adequate frequency and voltage). For the system operator it requests the integration of different sources (the base-load, the regulated and the non-regulated power stations, the fluctuating renewable wind and photovoltaic energy and in the future vehicle-to-grid units) and switch to the optimal network topology, in accordance with changing demands – known as unit commitment problem (UC). (Földesi, Baricza, Kiss, Vas, Bajor, 2010). The new challenges in electricity supply, like de-regulation, distributed generation (co-, tri- or multi- generation) and electricity storage needs new theoretical approaches from the viewpoint of logistics. Decentralized electricity production and the introduction of variable, fluctuating (renewable) sources and transportation needs (electric vehicles) increase the difficulty of stabilizing the power network, mainly due to a supply-demand imbalance. It is therefore convenient to generate the energy, transmit it, convert it, and then store it if need be. Although there are various commercially available electrical energy storage systems, no single storage system meets all the requirements today. (Földesi, Baricza, Kiss, Vas, Bajor, 2010). Unit commitment with renewable electricity sources and electrical energy storage is more complex than typical UC of conventional generating units, as the number of variables is much higher than in typical UC problems, and both cost and emission should be minimized. From the measurements of the available renewable sources it can be clearly seen that the fluctuation of the solar and wind sources could not have been well predicted. For higher utilization of these sources there is a strong need for electricity storage solutions, or some new aspects of demand side management techniques, we are investigating. National electricity supply grids are constructed and re-engineered for the annual peak consumption. The results of overdesigning are high infrastructure construction and operation cost, also unutilized capacity in the same time. Our wire-logistics approach deals with demand side management and renewable electricity applications to smooth the daily electricity profiles. 3. Using RC, RRC and Smart Metering DSM technologies for balancing Some distribution system operators (DSOs) - among them all Hungarian DSOs - have installed extensive demand-side management (DSM) infrastructure in order to be able to perform peak-clipping and valley-filling of the daily load curves. These systems rely either on the traditional ripple control (RC) or radio ripple control (RRC) technology (Dán et. al, 2010). The Ripple Control system is a telegram based DSM system, where the carrier is the 50 Hz distribution network. In Hungary the application of the system has been started in 1975, basically for switching on and off boilers (electric storage water heaters) and high capacity storage space heaters. In the beginning of the 2000’s the controlled power was approx. 1500 MW, which is one fourth of the winter peak load. Applying RC system, hundred thousands of customers can be controlled from one place, as the sending device can be installed on any voltage level from LV to HV. The addressee can be either only one consumer, or a group of them. The simple structure of RC could incur some possible problems, which are disadvantageous:
Nowadays the RC system is used for the following purposes in Hungary:
The control is based on sending standardized telegrams. The task of the Sender Device is to generate the message with the proper power and voltage to reach all (including the furthest) controlled customers. There are some new demands that cannot be realized using the traditional RC system. In the beginning of 1990’s the Radio Ripple Control (RRC) has been started to realize. The novelty of RRC (compared with RC):
Several goals can be set when the DSM is in focus, like daily load curve shaping, load limitation at system breakdowns, or minimizing of balancing energy (i.e. the minimization of the deviation of the actual load from the schedule) There are many different aspects of simulation, like
It has been shown that the household customers can be incited with a dynamic tariff system in order to reschedule their electric devices. This will cause consumption redistribution from the peak load periods to the valley load period. However in case of system breakdown a fast (but smart) load shedding can only be achieved with direct DSM. Thus the possibility of direct load control is essential and should be exploited in Smart Meter systems. Another reason to apply direct load control is the need to avoid large gradient load changes observed when simulating customer response to tariff incentives. It has also been demonstrated that load curve shaping can be performed more effectively if direct load control is applied for boilers and deep freezers – compared to the case when only a tariff incentive is applied. A special load control program is necessary for air-conditioners. 4. Domestic refrigerators in operation Product temperature is a quality and safety determining factor. Some indications show that food is often stored in domestic refrigerators at temperatures that are too high. In refrigerators without ventilation, strong temperature heterogeneity is often observed, with warm zones (sanitary risk) and cold zones (freezing risk) due to very low air circulation. (Laguerre et al. 2007)
The most common way to control the cooling capacity in household refrigerators and freezers is by on-off control (cycling or intermittent operation). The compressor starts as a preset temperature in the refrigerated space is exceeded (cut-in temperature) and shuts down as a low temperature (cut-out temperature) is reached. (Björk and Palm, 2010) Since the compressor efficiency also declines as the ambient temperature rises, a refrigerator's electricity use is very sensitive to the ambient temperature. Modest changes in kitchen temperature will have surprisingly large impacts on refrigerator energy use. Electricity consumption varied from 1.25 to 2.6 kWh per day even though the temperature increased only 11 °C (from 17 to 28 °C). The correlation is so good that it suggests that variations in ambient temperature cause virtually all of the variations in energy consumption. Just like a house, a refrigerator will use less electricity if its thermostat is re-set to a higher (warmer) temperature. The energy consumption rose 26% from the warmest acceptable to the coldest possible settings, when all other test conditions were maintained at the DOE values (Meier, 1995). Room temperature varies due to seasons and the thermostat setting varies according to consumer behaviour. The temperatures of the surveyed refrigerators were: average 6.6 °C, minimum 0.9°C and maximum 11.4°C. The temperature of 26% of surveyed refrigerators is higher than 8°C, which is the regulatory temperature for stable foods in France. The difference between the temperature level during weekdays and weekends is not significant. There are other parameters influences the energy need: There are results with empty and loaded refrigerators, between various room temperature and humidity conditions, with different frequency and length of door openings, thermostat settings, and the introduction of warm food. It has been identified that the performance of household refrigerator depends strongly on temperature and air distribution inside the storage chamber (Yang et. al, 2010) 5. Test measures on the field of “The mina Concept” There are many new development pathways for having smart refrigerator – we can imagine one that is equipped to sense what products are being put into it, and may even be able to determine when a product needs to be replenished. The refrigerator may even be able to send alerts when the food reaches a point where it may be suspect. This alert may be displayed on the refrigerator’s screen or may be sent to a computer via e-mail. The smart refrigerator keeps track of what is in stock through a couple of different methods. The method chosen often depends on the technology available on the food package. Given the fact that the smart refrigerator is still largely in the experimental stages, the technology is still evolving (for example RFID systems for automatic recognition and tracking). There are widely available pure technical developments, like having better insulation or more efficient compressor unit, what consumes less electricity and performs better between part-load conditions, etc. Finally, we were not able to find any investment in the literature dealing with the daily consumption profile of the domestic refrigerator.
On this way, overdesigning the production, transmission and distribution system required to be able to provide the actual consumer demand moments-from-moments, according to our lifestyle.
When we wake up, maybe the first thing is turn the light on – this need is elementary. After, during breakfast preparation, we usually open the door of the fridge, generally more than 3 times, and for more than 2 minutes – and after closing the door, we can realize, that the compressor switched on (the temperature reached the thermostat settings). As can be clearly seen on the profile, this period has the highest kinetic challenge – any saving we can reach in this “morning upload and peak” window provides huge benefit (the operation on the traditional way is very expensive - without fulfilling the needs from storage, like hydropower – the national grid’s system operator have to start expensive additional power plants, etc). The main idea of “The minA Concept” is to shift this demand to another, GridfRiEENd (grid-friendly) period (Földesi, Hegyi, Bajor, 2011). Naturally, this type of demand side management technique can be acceptable, if the limitation not affects the quality of food in the refrigerator. Applying “The minA Concept” in a case of a simple domestic refrigerator we installed a brand-new Gorenje RF3184W type fridge in Szabó-Szoba R&D Laboratory. The purpose of the research is to investigate which type of “variable setpoint strategy” can be able to help in smoothing the daily electricity profile of households and shift the cooling demand from critical periods to non-critical intervals. In the actual phase of our investigation we are focusing on to substitute the conventional "thermostat-driven" control to a "microcontroller-driven, product temperature based" one to prove the feasibility of the concept. During the test procedure our Gorenje refrigerator is completed with a York-ISN microcontroller for monitoring system parameters, like 6 analogue inputs for temperature sensors and additional 2 digital inputs, like
The York ISN microcontroller drives the only digital output for starting the compressor. During thermostat-driven control strategy the microcontroller pass the incoming signal to the compressor with 10 seconds delay, during peak limitation and minA strategy there are other system parameters required to start cooling (time window enabled, temperature of the liquid reach a given level, etc). A laptop computer was connected to the microcontroller to manage the operations and log measurements in every minute.
In the first phase of the investigation we made the test to recognize the thermostat-driven switching points related to product temperature distribution with different manual settings. As a result we got the thermostat-driven temperature profile of different settings near a given load (in our further research we will test the impact of door openings and various loads). The cooling process has different gradient where we consider different product or air temperature values, according to different thermal inertia and heat capacity.
In the actual phase of investigations we demonstrate the effect of applying “The minA Concept” with “microcontroller-driven, product temperature based” control:
Based on “The minA Concept” it is possible to reduce the number of switching operations, what can extend the lifetime of the compressor unit and reduce the maintenance cost. Otherwise, in this case we have to accept wider tolerance in the temperature profile. Applying “The minA Concept” often request longer operation interval of the compressor unit for cooling the products in the normal space, but in the same time the freezer can be over-cooled.
Based on the results of the test we can offer a possible gridfriend development of household refrigerators: a balance valve between the freezer and the refrigerator On this way we can solve the buffering task in 2 steps:
6. Conclusion We considered the cooling demand (an electricity-driven service) of a domestic refrigerator in our wire-logistics as a special need what sometimes can be delayed – in „The minA Concept” we presents an economically and technically achievable, environmentally sustainable way of cooling unit operations. We introduced a new pathway in domestic refrigerator advancement based on our special wire-logistics approach – it is possible not just disable, but simple limit the operating conditions, or in the deep valley periods (before morning peak and uploading, etc) use pre-cooling. Limitation or disabling can be applicable in warehouses as well – the trucks with vegetables usually arrive in the morning, unloading takes time, while the doors are open – it is possible not to start the refrigerator units for cooling the street, etc. In the successful integration of renewable electricity sources it is possible to use demand side management control for matching renewable production and electricity-based cooling (RC, RCC, DSM)
From the electric system operator point of view the application of “The minA Concept”, as a tool has great promises (it is possible to use on the same way, like night charge boilers and electrical heaters) – there is no need for special infrastructure, the electric network can transmit the “limitation” or “disabled” signal itself, no additional infrastructure required, only a cheap receiver-transmitter electronics in the refrigerator. The question remain: will the producers be opened for this type of innovations, or people will buy the required electronic equipment for centralized minA-control? Which type of tariff system can support these changes? 7. References
Authors Eszter, György – BSc student in transportation engineering Széchenyi István University Member of the Szabó-Szoba R&D Laboratory
Eötvös Lóránd University Budapest Member of the Szabó-Szoba R&D Laboratory
Széchenyi István University Assistant Lecturer at the Department of Logistics and Forwarding Member of the “Szabó-Szoba” Student’s Innovation and Education Development Laboratory Péter, Földesi CSc – transportation engineer MSc Széchenyi István University Reader, Head of the Department of Logistics at Forwarding H-9026 Győr, Egyetem tér 1. HUNGARY E-mail: pbajor@sze.hu, Mobile: +36 30 63-73-270 Yüklə 63,05 Kb. Dostları ilə paylaş:
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