Economic comparison methods for different hotel HVAC system options (air-cooled vs water-cooled, centrifugal vs screw chillers)
I am Tony Zhao, an HVAC cost control specialist. The scheme comparison and selection of hotel air-conditioning systems is a core part of MEP engineering cost control, directly affecting the project's initial investment, operational energy consumption and long-term O&M costs. According to Article 8.1.1 of the Code for Design of Heating Ventilation and Air Conditioning of Civil Buildings GB 50736-2012, the selection of air-conditioning systems should comprehensively consider building function, scale, climate conditions and energy supply. Based on my years of experience in high-end hotel projects, the economic comparison and selection of different schemes (air-cooled vs water-cooled, centrifugal vs screw chillers) requires quantitative analysis from four dimensions: initial investment, operating costs, full life-cycle cost and maintenance convenience.
**I. Comparison and Selection Method for Air-Cooled vs Water-Cooled Systems**
1. **Initial investment analysis**: Air-cooled systems (e.g., air-cooled heat pumps) do not require cooling towers, cooling water pumps or cooling water piping; the cost per unit is about 800-1200 yuan/kW (cooling capacity), whereas water-cooled systems (e.g., water-cooled screw chillers) require additional cooling towers, pumps and water treatment equipment, with a comprehensive initial investment of about 1200-1800 yuan/kW. For example, for a five-star hotel (building area 40,000 m², cooling load 4000 kW), the initial investment for the air-cooled scheme is about 4.8 million yuan and that for the water-cooled scheme about 6 million yuan, with the air-cooled scheme saving about 20%.
2. **Operating cost comparison**: Water-cooled systems generally have a higher energy efficiency ratio (EER) (water-cooled screw chillers EER ≥5.0, air-cooled heat pumps EER ≈3.0-3.5). Calculated on the basis of 3000 annual operating hours and an electricity price of 0.8 yuan/kWh, the annual electricity cost of the water-cooled scheme is about 1.92 million yuan and that of the air-cooled scheme about 3.2 million yuan, with the water-cooled scheme saving 1.28 million yuan per year. Note, however, that water-cooled systems require consideration of cooling tower make-up water and water treatment costs (about 5-8 yuan/m²·year).
3. **Full life-cycle cost (LCC)**: Calculated over 20 years, the total cost of the air-cooled scheme = initial investment 4.8 million yuan + O&M costs (electricity + maintenance, about 3.4 million yuan/year × 20 years) = 72.8 million yuan; the water-cooled scheme = initial investment 6 million yuan + O&M costs (about 2 million yuan/year × 20 years) = 46 million yuan. The LCC of the water-cooled scheme is about 37% lower.
4. **Applicable scenarios**: Air-cooled is suitable for water-scarce, dry-climate regions (e.g., the Northwest) or small hotels (<10,000 m²); water-cooled is suitable for large hotels (>20,000 m²) or hot and humid regions.
**II. Comparison and Selection Method for Centrifugal vs Screw Chillers**
1. **Capacity and efficiency**: Centrifugal chillers are suitable for large cooling capacities (>1000 kW), with a full-load COP of up to 6.0-7.0 and excellent part-load performance (IPLV ≥8.5); screw chillers are suitable for small and medium cooling capacities (200-1000 kW), with a full-load COP of about 4.5-5.5 and an IPLV of about 7.0. With reference to the Minimum Allowable Values of Energy Efficiency and Energy Efficiency Grades for Water Chillers GB 19577-2015, a Grade 1 energy-efficiency centrifugal chiller saves 15-20% energy compared with a screw chiller.
2. **Initial investment**: The cost per centrifugal chiller is about 1500-2500 yuan/kW, and that of a screw chiller about 1000-1500 yuan/kW. Taking a cooling load of 3000 kW as an example, the initial investment for the centrifugal scheme (2 × 1500 kW) is about 4.5 million yuan and that for the screw scheme (3 × 1000 kW) about 3.75 million yuan, with the screw scheme saving about 17%.
3. **Operating cost**: Assuming 3000 annual operating hours, the annual power consumption of the centrifugal chillers is about 1.5 million kWh (at COP 6.0) and that of the screw chillers about 2 million kWh (at COP 4.5); at an electricity price of 0.8 yuan/kWh, the centrifugal chillers save 400,000 yuan per year.
4. **Maintenance cost**: Centrifugal chillers have a complex structure, with annual maintenance costs of about 30,000-50,000 yuan/unit, versus about 20,000-30,000 yuan/unit for screw chillers; however, the service life of centrifugal chillers (25-30 years) is longer than that of screw chillers (15-20 years).
5. **Case**: For a resort hotel (cooling load 5000 kW), 2 centrifugal chillers were selected (initial investment 7.5 million yuan) versus 5 screw chillers (initial investment 6.25 million yuan). After 10 years of operation, the total cost of the centrifugal scheme (including initial investment + electricity + maintenance) is about 16.5 million yuan and that of the screw scheme about 19.5 million yuan, with the centrifugal scheme saving 3 million yuan.
**III. Comprehensive Comparison and Selection Process**
1. **Load calculation**: Based on the peak load and part-load characteristics of the hotel's functional zones (guest rooms, restaurants, banquet halls), use DeST or EnergyPlus to simulate the annual load distribution.
2. **Scheme combination**: A "centrifugal + screw" combination is recommended; for example, a large hotel uses centrifugal chillers for the base load (70% load) and screw chillers for peak shaving (30% load), achieving a balance between initial investment and operating costs.
3. **Economic indicators**: Calculate net present value (NPV), internal rate of return (IRR) and payback period. For example, the water-cooled centrifugal scheme has an initial investment 1.2 million yuan higher than the air-cooled scheme but saves 1.28 million yuan in annual operating costs, with a static payback period of <1 year, showing significant economic benefits.
**Summary**: For the comparison and selection of hotel air-conditioning systems, priority should be given to water-cooled centrifugal chillers (large projects) or a "centrifugal + screw" combination (medium-sized projects), whose full life-cycle cost advantages are obvious. However, the climate, water resource conditions and electricity price fluctuations at the project location must be taken into account. The above are reference opinions. The actual situation of the project still needs to be further comprehensively evaluated and implemented in combination with specific operating conditions, site conditions and other factors.