San Francisco's Orchard Garden Hotel was San Francisco's first hotel to implement a cardkey system to control lights and HVAC systems in guestrooms. Monitored data from four rooms in the hotel showed a reduction in heating and cooling energy of 45% during the peak cooling season (See Figure 1). Computer simulations based on monitored occupancy levels in the hotel estimate a savings of 32% of annual heating and cooling costs. Modeled across five different climate zones, the average savings were 26%.
Figure 1. Energy use for one month in four rooms with and without guestroom controls
Figure 2. A cardkey receptacle
The cardkey system is explained to guests when they check into the hotel. After a guest enters a room using their cardkey, they place the card in a special receptacle near the entrance. Inserting the card into the receptacle signals the guestroom controls to turn the system components onto occupied mode. That signal will bring the thermostat setting back to the desired temperature during occupancy and permit lights, televisions, and other equipment to turn on.
When exiting the room, the guest takes the key with them, automatically "turning off" the entire room once the key is removed from the receptacle. Had the occupant failed to turn off the television, for instance, it would then be shut down. At least one outlet is excluded from the system so that guests can charge laptops, cell phones, and other battery-powered devices while they are out of the room.
Guest feedback of the system at the Orchard Garden Hotel has been mostly positive. Stefan Muhle, general manager, believes that "while most international guests find it commonplace, those who are new to the technology have become quite fond of it." Mr. Muhle says that instructions given upon check-in make the guests comfortable using the system and "make the guests feel positive about saving energy."
The hotel industry is fertile ground for saving energy. Guestroom energy uses account for 40%-80% of total hotel energy costs, and those rooms are unoccupied much of the time. Nationwide estimates for guestroom energy expenses suggest that 80% is for heating and cooling, the remaining 20% is for plug loads and lighting. (1)
Typical hotel HVAC systems are designed to maintain a guestroom at a fixed temperature both day and night. In many hotels - whether the guests are business or leisure travelers - the rooms are frequently unoccupied for much of the day. During those times, it will save hotels money to setback the thermostat or completely turn off the heating and cooling. Guestroom control systems accomplish just that.
Further, a significant portion of hotel rooms remain "unrented" at any given time. PKF consulting reports an average 77% rental rate for hotels in Northern California and the Central Valley. For hotels that leave HVAC systems in guestrooms running all the time, this vacancy rate offers another significant opportunity to save energy with guestroom control systems.
Guestroom control systems can be installed in new and existing hotels, with the biggest opportunity for energy savings in the substantial stock of existing hotels. Hard-wired systems will be cost-effective only for new construction or major renovations. Wireless systems are available that are well suited for retrofit installations in existing hotels.
Guestroom control systems can be configured to:
- Manage either fan coil units or self-contained through-the-wall air conditioning units (PTAC units).
- Draw the curtains once a guest leaves the room to reduce solar gains through the window. This can significantly increase savings.
- Setback the thermostat when a window or patio door has been left open.
The primary benefit of guestroom control systems is that they reduce energy use for the hotel. By either setting back the thermostat or shutting the HVAC unit off when the room is unoccupied, they reduce cooling and heating energy use. Some systems can also control lighting and receptacle loads. Not all lights and outlets are controlled, since some need to remain on to power clocks, telephones, and devices plugged in by guests.
A second benefit is that occupancy controls reduce peak demand. Hotel rooms are frequently unoccupied during afternoon hours when electricity demand is highest. By reducing peak loads, there is an opportunity to downsize central cooling systems for new installations in large hotels or during system replacements. Utility demand charges are also reduced.
Figure 3. Monitored Guestroom Occupancy. Monitored occupancy data from two hotels shows that occupancy is very low during the afternoon hours when electricity demand is typically highest
Some guestroom control systems can be integrated with energy management systems, which offer centralized control of room comfort. One advantage of centralized control is that the system can apply a wider temperature setback when a room is unrented since it does not need to be ready to return to a target occupancy temperature on as short of notice. The wider temperature setback in turn results in greater energy savings. The centralized control also permits the implementation of building-wide demand management strategies when desired.
Some products offer additional features such as displaying occupancy status to housekeeping staff so that they do not disturb a guest. While such features do not have direct energy benefits, they may lead to a more pleasant stay for guests. Drapes that close automatically when a room is unoccupied will also minimize fading of upholstery and decorations, adding to their useful life. A system recently introduced into the marketplace provides control of room temperature, lighting, and a "do not disturb" sign through the television remote.
One concern with the cardkey system is that guests may insert a second or spare key into the slot when leaving the room to minimize their inconvenience, thus defeating the controls. Cardkey systems are more prevalent in Europe and Asia and guests there have a positive perception of the controls. A recent guest survey for a hotel with the cardkey system showed that the vast majority of the guests felt positively about the system and did not consider it to be an inconvenience. While many noticed a change in room temperature upon returning to the room, most found it to be acceptable.
The occupancy sensor systems have an advantage over the cardkey systems in that they do not require guest interaction. However, there is a concern that guests unfamiliar with the occupancy sensors may mistake them for cameras or other monitoring devices that compromise their privacy. Some occupancy sensors are integrated into the thermostat to minimize this perception. Other occupancy sensors are available that are designed to look like smoke detectors to minimize guest concerns.
1. "Technology: Energy management systems save hoteliers money" Whitford, M., Hotel & Motel Management Dec 1998.
2. "Card-Key Based Guestroom Controls Evaluation Report", PG&E, 2007 and "Occupancy Based Guestroom Controls Evaluation Report", PG&E, 2007. The report cites previous studies by ACEEE, Lau and Muhle in estimating savings and payback period.
California utilities offer outstanding educational opportunities that focus on the design, construction and operation of energy efficient buildings. Listed here are a few of the many upcoming classes and events; for complete schedules, visit each utility's website.
Efficient Air Conditioning and Energy Management Systems
This course will cover specific efficiency features of small-tomedium- size air conditioning systems, shed some light on the SEER and EER rating methods, and explore air conditioning unit replacement economics. Offered in San Diego on January 14, 2010.
Facility staff and management professionals will learn about current energy efficient technologies used in commercial and industrial businesses. Topics include lighting, chilled water systems, electric motors, drives, energy management systems, HVAC, and distributed energy resources. Attendees will learn how to save money by implementing basic technology changes. Offered in Tulare on February 4, 2010 and in Irwindale on January 12 and 13, 2010.
Basic Programmable Logic Controllers: Energy Efficiency Applications
Management, operations, and maintenance professionals will learn the basics of how Programmable Logic Controllers (PLCs) operate in an industrial process and how they can be used for energy efficient applications. Participants will develop a basic understanding of Programmable Logic Controllers terminology, how the hardware components are used, and the basics of relay ladder logic. Offered in Irwindale on March 16, 2010.
Energy Management Systems
This one-day seminar presents a review of common HVAC system configurations, the fundamentals of how energy management systems (EMS) are constructed and how they work, an overview of communication networks, and how EMS are able to maximize energy-use savings. It focuses on how to maximize savings using the most current technology in HVAC control methods. In addition, the seminar presents a practical, systematic approach for identifying, designing, and planning the implementation of an energy management control system. This seminar is recommended for those who have some understanding of HVAC systems and desire to know more about saving on operating costs with an EMS. Offered in San Diego on February 9, 2010.
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