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Modernization in the heating system


The Hotel Meliá Castilla is considered one of the most beautiful hotels in Madrid. It combines classical style and modern amenities into an ambiance of quiet and relaxation, in the center of the Spanish capitol city. In order that the hotel, with its favorable location, remains successful in the future, the international Meliá Group constantly works to connect service and comfort with efficiency and sustainability. Recently, the Spanish system integrator ALTARE Energía completed a modernization program for the heating system, together with WAGO.

The more stars, the higher the bar, naturally, for dazzling guests with quality and service. Yet, which of these services brings higher operating costs along with it? The Meliá Castilla — directly adjacent to the urban Plaza Castilla — includes 903 rooms and twelve suites, offers an auditorium for more than 1000 visitors, as well as spaces for business meetings and celebrations. The energy appetite of the hotel, located in the financial quarter, is correspondingly high in times of high occupancy rates. At this point, the reader should be aware that these utility costs are the second highest annual expense for the hotel, after personnel expenditures.

When viewed another way, this statement means that the potential for optimization is great. The challenge of the modernization project consisted in ensuring first-class customer satisfaction with minimum energy consumption. It was thus about cutting costs, but the increase in energy efficiency was to have no negative impact in comfort. In the technical implementation, this balancing act led to the use of the WAGO-I/O-SYSTEM 750 with the EXEON software developed by the solution partner, ALTARE.

Scalable: Systems that Can Grow Together

As multifunctional software, EXEON supports the continuous improvement process within an energy management system and can be used for operating heating, ventilation, and air conditioning systems, and also control the lights. The program provides an user-friendly GUI (Graphic User Interface) and manages the WAGO-I/O-SYSTEM 750 control hardware on site using a simple but safe ETHERNET network (Modbus TCP). EXEON and WAGO can thereby provide a scalable solution, which can effortlessly grow to meet future demands due to its expandable functions.

ALTARE set their own goal, following a system analysis, to provide the customers with a deep insight as to which measures achieved the greatest positive effect on energy efficient operation during the project — without negatively impacting the comfort of the guests. The priority that modernizations of this type exhibit in the international hotel business is demonstrated by the International SAVE Project, launched by Meliá Hotels, to reduce the environmental effects of hospitality operations. In addition to the measures undertaken at Meliá Castilla, there are parallel efficiency projects in other countries.

Control: Boilers and Pumps Follow Consumption

The focus of the work in Madrid consisted in replacing the existing building management system with a modern, standardized, and flexibly usable solution — which is what led to the combination of EXEON and the WAGO-I/O-SYSTEM 750. Below the automation level, the replacement of the heating system, which ran on gas, with a new one, ensured substantial savings. Today, a new natural gas system provides a total output of 3.6 MW at an initially expected efficiency of 95 percent. This number was considered as rather ambitious, as the system includes six 600-kW boilers, whose operation has to be perfectly tuned with each other. A complication arose due to the size of the hotel: distances had to be overcome of more than 20 floors between the rooftop boilers and the central distribution point, located in the cellar in the existing system.

The project envisioned maintaining a constant temperature in the primary reservoir, even when secondary systems, like the fan convectors, heat circuits, or hot water regions in the guest rooms and public spaces signaled additional consumption. Based on WAGO’s libraries for building automation (BUILDING HVAC), multiple PID Controllers* were developed, which the system integrator could use to control the boiler output via temperature, along with pressure sensors installed to control the pump throughput. The result: optimized output of energy supply due to a tailored PID configuration with precise boiler and pump control.

Efficiency Linked to Comfort

How well the system worked in comparison with the old technology became amply clear on the first day after implementation — there were no significant reductions in comfort despite a ten degree reduction in supply temperature. The project team used the following operating months to implement additional optimizations, which allowed the efficiency to increase by an additional two percent, to 97 %. Thanks to the new control system, the hotel is currently well supplied using only 30 % of the heating output installed, which has resulted in correspondingly high savings in operating costs.

A longer lifecycle has increased together with the availability, because the system is almost never driven into the borderline range of its output. The current operating situation also makes abundantly clear how important it is to incorporate continuously learning systems within energy management systems. This is the only possibility for further optimization of systems during operation. The control algorithms implemented in the WAGO-I/O-SYSTEM create the foundation, for regulating the heating system output and throughput amounts corresponding to actual currently prevailing need.

Text: Jose Sierra, ALTARE and Alvaro Mallol, Dicomat/WAGO
Photo: WAGO