5 Industrial Cooling Schemes: Cut Cooling Power Use Up to 10 Times

This practical guide is for chief engineers, energy managers, operations teams and designers at plants with a constant cooling load: recirculating water systems, equipment cooling, process cooling. I took one task, 1,000 kW of cooling, and worked it through five schemes for the climate of Cherepovets, Russia. The electricity bill differs 10 times between them. The difference is not the chiller brand but the heat rejection scheme itself and how much mechanical cooling the site really needs. The PDF is in Russian; the key points are below in English.

What is inside the guide?

• Design basis: 1,000 kW, chilled water at +12/+7 °C, Cherepovets, round-the-clock operation, RUB 7 per kWh.

• Scheme 1. Packaged air-cooled chiller.

• Scheme 2. Chiller with integrated free cooling (cooling with outdoor air while the compressor is off).

• Scheme 3. Screw chiller with an open wet cooling tower.

• Scheme 4. Absorption chiller on waste steam.

• Scheme 5. Wet cooling tower without a chiller.

• A summary table: installed and average electrical load, CAPEX, OPEX, water use.

• Three questions that pick the scheme for your site.

• A glossary: COP, CAPEX, OPEX, absorption chiller, water treatment, waste heat, wet bulb.

Key takeaways

One method for all five schemes. 1,000 kW of cooling at +12/+7 °C in Cherepovets: winter design temperature about −32 °C and summer wet bulb about +20 °C per SP 131.13330 (Russian building climatology code). Round-the-clock operation at an average load of 0.7, which is about 6,130 equivalent full-load hours a year. The figures are design estimates: for a specific site they are refined by the heat balance, the actual load profile and local tariffs.

The packaged chiller is the baseline. COP about 3.0: every kilowatt of cooling takes about 0.33 kW of electricity. 333 kW of electrical load, CAPEX about RUB 13 million, OPEX about RUB 14.5 million a year. It fits small sites, places short of water and backup duty. For a constant 1,000 kW load it is the most expensive option to run.

Free cooling halves the bill, not the connected load. In Cherepovets full free cooling is available for about 4,000 hours a year and partial free cooling for another 2,500 or so. Annual COP rises to about 6.1 and OPEX falls to RUB 7.1 million. But installed load stays at about 340 kW, because the compressors are still needed for summer. The plus: the savings come without water or water treatment.

A cooling tower gives the same effect all year round. Water from an open cooling tower cools the chiller condenser, giving a COP of about 6.0 in frost and in heat alike, about 190 kW of installed load and OPEX of about RUB 7.3 million. The price: make-up water of about 2 m³/h, mandatory water treatment, Legionella control under SanPiN (Russian sanitary rules) and freeze protection in winter.

An absorption chiller on waste steam makes cooling from heat. If the site has waste steam (a combined heat and power plant, exhaust heat from furnaces), electricity is needed almost only for pumps: about 60 kW installed, an electrical COP of about 20, OPEX about RUB 2.4 million a year. CAPEX is 2 to 3 times that of a packaged chiller. The machine rejects about 2.4 times more heat than the cooling it produces, so the cooling tower must be larger, and start-up takes about 30 minutes. For steel plants with surplus steam it is one of the strongest options.

If the process does not need +7 °C, it does not need a chiller. An open cooling tower cools water by evaporation; in Cherepovets in summer that is about +24 to +25 °C. The rule: if the process setpoint is no lower than the wet bulb temperature plus 3 to 5 °C, a cooling tower alone is enough. About 30 kW against 333 kW for the packaged chiller is eleven times less electricity for the same task. CAPEX about RUB 3 to 4 million, OPEX about RUB 1.5 million a year.

The less refrigeration machine, the lower the bill. The pattern runs through the whole table: both annual consumption and the load you must connect to the grid go down.

Who is it for?

• Chief engineers and energy managers at plants with a constant cooling load.

• Operations teams looking for ways to cut the electricity bill.

• Designers at concept stage, while the scheme can still be changed.

• Plants that are hitting a grid connection limit or have surplus waste steam.

FAQ

How do I know which scheme suits my site?

Answer three questions. What water temperature does the process really need? If it is no lower than the wet bulb plus 3 to 5 °C, you may not need a chiller at all (scheme 5). Is there waste heat on site, such as steam or hot water? Then evaluate an absorption chiller (scheme 4). Do you have water and a team to run water treatment? If not, use free cooling without water (scheme 2).

Why does free cooling not reduce the connected load?

In winter the compressors barely run, so average consumption halves, from 333 to about 165 kW. In summer the compressors carry the load again, so you still have to connect about 340 kW. If you are up against a power limit, look at a cooling tower or an absorption chiller.

Where does "up to 10 times" come from?

From comparing the two extreme schemes on the same task: a wet cooling tower without a chiller draws about 30 kW on average, a packaged chiller 333 kW. That is eleven times less electricity.

Related articles

• How to cut industrial cooling costs: 8 measures with the numbers

• Chiller free cooling: when the compressor stops and what it saves

• What is an absorption chiller? How it works, when it beats a chiller

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