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Energy efficiency: room for improvement

Advances in control software will have a significant impact on hotel air conditioning, both in energy efficiency and in customer experience, says Samsung’s Mark Edinburgh

Optimising the efficiency of hotel air conditioning is a complex operation, with heating and cooling loads affected by seasonal fluctuations in guest numbers, the weather, and managers looking for maximum cost-effectiveness throughout the business - not to mention each room needing to have local control by the guest.

But now new software developments from Samsung are helping to produce five-star efficiency - and provide hotels with a free customer service boost.

Standard air conditioned rooms require filtration through the indoor units helps to keep both the air and the room cleaner, with simple wall-mounted control panels enabling the guest to raise or lower the temperature by a few degrees, within limits programmed into the hotel’s main controller.

Many hotels have cut back on energy use with guest room management systems, where the door card keys can also activate the air conditioning, as well as the lights - which means the indoor units run only when guests are in their rooms and the overall load on the air conditioning system is minimised when demand is low.

But Samsung is now introducing a concept into Europe that goes one better, integrating its system software directly to the hotel’s reservations system. For regular visitors it means that their preferred temperature levels can be preset to bring their rooms to the desired temperature in time for their expected check-in. For other guests, a standard temperature is programmed to be achieved just ahead of their expected arrival times, improving customer experience and avoiding unnecessary energy use.

Such efficiencies will undoubtedly improve the cost effectiveness of air conditioning systems. If guests’ preferences and expected arrival times are known in advance, the system load can be automatically assessed and the units powered up in the most economical way to avoid any sudden - and often expensive - peaks in demand.

It is already to possible to isolate a number of rooms during an off season or for building maintenance. The same flexibility of system design and control means that in the event of a partial system failure, not all rooms are affected.

Samsung’s electronics engineers have already created Homevita - an integrated digital home control system - along with web-based tools which enable facilities managers to manage individual units and systems across multiple sites. The combination of these now means that hotels can offer a more personalised service (and use facilities more costeffectively) while a hotel group’s facilities manager could in theory manage the air conditioning in scores of locations around the world.

But without stating the obvious, while there are similarities in the design of many hotels, especially the chains, there is no single right answer for air conditioning system design. For example, the solutions for a 200-bedroom establishment on two floors may differ from those for the same number of rooms, but on five floors. This is because of potential issues of pipe run lengths and height differences between indoor and outdoor units. Design of the outdoor installation may be affected by limited roof space on a high-rise building, or awkward siting of a ground level system for a low building.

Typically, a hotel room needs an indoor unit delivering approximately 2.2 kW of cooling and 2.5kW of heating to achieve fast changes in temperature when necessary, and then maintain desired levels quietly and efficiently.

Many hotels tend to have both front and rear rooms, and there’s often an even split between naturally warm and cool as a result. For the UK climate, a three-pipe
heat recovery air conditioning system is virtually a pre-requisite for cost-efficiency. For significant parts of the year, surplus heat from warm south-facing rooms provides free energy to counteract the chill in north-facing rooms.

Samsung’s DVM Plus III VRF system provides heat recovery systems which allow simultaneous heating and cooling, and have the same general specifications as the two-pipe heat pump versions for heating or cooling.

Taking a notional 200-room hotel with 2.2 kW indoor units as an example (and ignoring any air conditioning requirement in public areas), it would require a total system capacity of 440 kW (or 400kW after allowing for 110 per cent connectability). This could be delivered in a number of ways, but a likely specification might be to arrange the indoor units in four groups of 50, each requiring at least a 27 kW outdoor unit, delivering 100.8 kW. Samsung’s five basic outdoor models can be combined variously to produce capacities up to an industry-leading 48 kW. Indoor units are available from 2.2 kW to 14 kW and up to 64 can be connected to a single system of appropriate capacity.

The systems could be co-located or one or more systems could be roof mounted with the others in ground level locations. DVM Plus III claims a small footprint, with a 48 kW requiring just 3.67 sq m of installation space,.

The DVM Plus III is based on digital scroll compressor technology, which gives stepless variation in capacity across the range and full efficiency from 100 per cent load down to 10 per cent - and theoretically even down to 1 per cent. This performance contrasts with other VRF-type systems which cannot deliver efficiency below 30 per cent load, and as a result are more expensive to operate during low-demand cycles.

We believe that such digital technology is marketleading, but that its value to the customer can be far greater when combined with complementary solutions, such as the hotel software, so our engineers continue to work towards new permutations.

Mark Edinburgh is technical sales manager for Samsung

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