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ΤHE SCIENTIFIC ENERGY SAVING PROJECT OF SEMAN
IN GRANDE BRETAGNE HOTEL
Α. Hotel Grande Bretagne
“Eternal Elegance at the Heart of Europe's Historic Capital”
With breathtaking views of the fabled Acropolis, regal Syntagma Square and the Parliament, lush Lycabettus Hill or the original Olympic Stadium, the multi-awarded 5 star Hotel Grande Bretagne offers an unrivalled perspective of Athens' mythical history.
Situated right in the heart of the city, since 1874, the landmark hotel is within walking distance of exclusive shopping areas, museums and the business district.
The GB Roof Garden Restaurant & Bar, ideally located on the top floor of the hotel, serves the finest modern Greek cuisine and offers breathtaking views of the Acropolis. The Cellar stocks more than 3,000 bottles of the finest vintages, the perfect setting for an exquisite private wine tasting event.
Escape to the GB Spa Athens for a signature massage and beauty treatment or an indulgent respite in the Thermal Suite. Keep your workout routine on track at our Fitness Studio, operating 24/7 for hotel guests.
Picture 1: Hotel Grande Bretagne (exterior)
Picture 2: Hotel Grande Bretagne (interior)
The total installed electric power of Hotel Grande Bretagne comes up to 3,5 MW. The grid is in 50Hz and there are 2 Transformers that supply loads to 400V. The average annual cost of electricity is approximately 1.000.000 € in current prices.
Β. The scientific project of SEMAN SA
The scientific project for energy saving and current - voltage quality improvement has been concluded by SEMAN SA at May 2014.
In order to elaborate the scientific study for Hotel Grande Bretagne, the engineer’s staff of SEMAN SA performed measurements and recordings – of all the required electrical values – in each individual load of the installation such as main operationloads, as well as to utilities loads, such as chillers, compressor pumps, laundry, etc.
Picture 3: Laptops used for measurements and recordings
Measurements and recordings concerned the basic electric values (power, reactive power, voltage, current, frequency) as well as current & voltage harmonics (up to the 35th class) and transient phenomena.
Inside the Electric Power Grid of Hotel Grande Bretagne, transient phenomena occur not only from the disturbances catering from Public Power Distribution Network, but also from their own big electric loads (chillers, compressor pumps, laundry, etc.) that start and stop during the day.
Picture 4: Measurements have been performed also in the core of the electrical installation next to the loads
Moreover the engineers’ staff of SEMAN SA proceeded to the collection of all the essential data that had to do with lengths and cross-sections of cables, number of cables headed together in canals, nominal values of motors, power transformers and many others also necessary for elaborating the scientific study for the energy saving project.
Picture 5: Measurements with special power quality analyzers and laptops
Based on the above, the engineers of SEMAN SA were able to simulate the behavior of Hotel Grande Bretagne Electric Power Grid and detect all the problems that were causing bad quality of voltage and current, low electric loads and power transformers efficiency, harmonic resonances and multiple other energy losses. The simulations conducted are based on SEMAN’s know-how, which has been awarded by the university of Cambridge and USA institutes. More particularly, models based on the Finite Elements Method (FEM) in combination with load flow analysis were used to complete all the required simulations (more information concerning SEMAN’s simulation models can be found at the CD which has been delivered to you).
The analysis of measurements and recordings showed that considerable harmonic sources existed inside Hotel Grande Bretagne Electric Network, producing not only harmonic currents (in some cases THD-I% reached 70% of the load),
Picture 6: Harmonic currents recordings in the electric network
but also considerable voltage harmonics.
Picture 7: Voltage harmonics recordings in the electric network
Picture 8: Portable measurement devices
Moreover, a number of energy saving scenarios, for the specific Electrical Power Grid – all based on the know-how of SEMAN SA – carried out by the use of simulations and finally the scientific study concluded 13 specialized interventions (please refer to pictures 9, 10) that had been installed inside the Electric Power Network of Hotel Grande Bretagne.
The total installed power of the interventions for the voltage-current quality improvement and energy saving project was 562,5KVA.
The target of the installed customized interventions is to minimize the current-voltage harmonics and to improve the current-voltage quality of the electric installation of Hotel Grande Bretagne.
Current – Voltage Quality improvement will:
- maximize the total efficiency of the Electrical Installation,
- improve motors’ efficiencies, due to:
the minimization of the counterclockwise electromagnetic torques caused by harmonics and,
the reduction of voltage drops and the higher constant voltage to the motors.
- improve power transformers’ efficiencies by the reduction of their copper and iron losses,
- reduce the following thermal losses:
Thermal losses of supply.
Contiguity Effect Losses.
Skin Effect Losses.
Eddy Current Losses.
It should be mentioned that the design of interventions took into consideration not only the interaction with other electric loads of the network, but also the resonance frequencies of the electric power cables of the grid.
Picture 9: Low Voltage (LV) Variable Antiresonance Harmonic Filter
Picture 10: Reactor of the LV Variable Antiresonance Harmonic Filter
The customized interventions for voltage-current quality improvement are connected in parallel to the electric loads and lead to harmonics absorption and their important reduction inside the electric installation of the hotel. Furthermore, resonance frequencies that could lead to dangerous tuning are being cut off. PLC with special design from Seman’s engineers, based on the results of the scientific study, control the dynamic operation of each intervention according to the fluctuations of the electric load and ensure the cutting of all dangerous interactions between the loads.
Additional to their above characteristics, these customized interventions have the ability to compensate “useless” reactive currents that flow inside the electric power grid.
C. Results – Benefits
For the evaluation of the Power Quality Improvement and Saving Project in Hotel Grande Bretagne, measurements and recordings were taken place in two time periods in May 2014 and in September 2014 (four months later) with and without the interventions into operation. The measurements and recordings were realized in presence of Hotel Grande Bretagne staff of engineers and the results presented in Table 1.
Thereafter, a comparison of the Key Performance Indicator (KPI) index before and after the saving projects commissioning was made. In the case of Hotel Grande Bretagne, two KPI indices were used:
KPI and KPItemp
The above KPI indices illustrate the specific energy consumption (kWh/number of occupied rooms) and are calculated, for KPI, by the monthly energy consumption (kWh) divided by the monthly number of occupied rooms of the hotel and, for KPIltemp, by the monthly number of occupied rooms of the hotel and by the average monthly ambient temperature in the area of the hotel.
The comparison of the above indices, before and after the project implementation, gives us the results presented in Table 1.
Table 1. Synoptic Results of Power Quality Improvement and Saving Project accomplished for the Hotel Grande Bretagne
Value / ResultsGuaranteed saving according to the contract (%) / -7,6%
Average saving resulted from measurements (%)
(according also to the Reference Letter by Hotel Grande Bretagne) / -12,6%
Saving resulted from KPI (%)
(according also to the Reference Letter by Hotel Grande Bretagne) / -18,74%
Saving resulted from KPItemp (%)
(according also to the Reference Letter by Hotel Grande Bretagne) / -17,12%
Picture 11: Harmonic currents recordings in the electric network after Seman’s project
Picture 12: Voltage harmonics recordings in the electric network after Seman’s project
In addition, SEMAN’s scientific project inside the electrical installation Hotel Grande Bretagne in Athens, Greece, had some extra benefits, confirmed also by the recordings before and after the installation of the energy saving equipment and the ascertainments of Hotel Grande Bretagne responsible Managers.
These extra benefits are the following:
1. Reduction of current & voltage harmonics up to 80%.
2. Optimization of the voltage & current quality of the electrical power grid of the hotel.
3. Maximization of the efficiency ratio of the electric power grid, motors and power transformers.
4. Reduction of undesirable stopping of electrical equipment because of the reduction of sensitivity of load voltage supply to immersions of the voltage supplied by the electricity provider’s Power Distribution Network.
5. Increase of the reserve and capacity charge of the electrical installation.
6. Reduction of the maintenance cost concerning all the components of the electrical installation.