Chilled water-based cooling systems are commonly used to maintain consistency in room temperatures throughout the hotel and sometimes offer guests the comfort of personal settings. They represent a large initial capital outlay, require a designated floor space and if not managed properly, can expose the hotel to high electricity and maintenance costs. They still offer greater benefits over air cooled packaged units that rely on air ducts to transfer cooled air to a designated point. Water is a more efficient energy conductor and requires less piping space than an air duct system. In addition, water based chillers offer better energy efficiency, a higher degree of overall temperature control (flexibility) and a longer life span.
It is important to match chilller plant size and piping network to the required amount of temperature control. Too small and the system is overwork, too large and the system wastes capacity. Significant energy savings can result if chiller selection, sizing and staging acknowledge the dynamic nature of chiller efficiency dependencies, including the building load and heat rejection temperatures. A key factor is variable speed chiller plants that offer flexibility to adapt to changing hotel conditions and seasonal changes.
Retrofitting or upgrading existing chiller plants is also a viable option. Results of up to 60% energy reduction costs have been recorded if the correct configuration, control and maintenance have been implemented. Retrofitting involves replacing existing operational controls with a broader networked control strategy. There are a number of feature/products add-on components available that offer the hotel owner/manager automated control that optimizes the chiller operation under all loading conditions. In addition there is new methodology for making sure the plant operates at commissioned levels for the life of the system.
It is worth making the changes now as Government has already introduced chiller efficiency requirements through the SANS 204/2011 brief (South African National Standard). This standard specifies the design requirements for energy efficiency in buildings and of services in buildings with natural environmental control and artificial ventilation or air conditioning systems.
What you need to know:
- Chillers are responsible for a large percentage of the total electricity consumption of a building
- Usually designed to last more than 20 years
- Selecting the right design and layout and matching it to the anticipated operating conditions is critical for overall efficiency
- Efficient components like the chiller itself, pumps, fans, pipes and motors should all be selected for stand-alone as well as systemic efficiency
- Commissioning is essential to optimal performance – a rigorous commissioning process that tests the plant function under all modes of operation ensures optimal performance
- To enhance chiller efficiency , deploy high-efficiency lighting, day lighting, appropriate glazing and insulation to compliment the overall systems operation
- Modular chiller plants are available at a lower cost but need to be custom automated to suite hotel conditions and chiller requirements
- Sensor activators such as key slots, door sensors or movement sensors can serve to economise the system by only supplying air-conditioning when rooms are occupied
- Avoid customised room setting options where possible
- If you are located on the coast, systems are available whereby desalinated sea water can be used to feed your chiller plant
- In terms of the new SANS 204 regulations, cooling and heating equipment shall have efficiencies in accordance with ASHRAE 90.1. (American Society of Heating, Refrigerating and Air Conditioning Engineers)