How can a hospital cut the energy use of its gas plants?

Match output to demand

Under HTM 02-01 (2026), the NHS England guidance, all medical air plant designs should consider variable speed drive (VSD) compressors, and a single dual-purpose plant supplying both surgical and medical air with VSDs is described as the most sustainable and efficient solution, which should be specified. Plant efficiency is expressed as free air delivered to the pipeline per kWh, with a minimum of 5 m³/kWh at both 100% and 10% of design flow, and power at zero flow should be less than 1% of the power at 100% design flow. For vacuum plant, the guidance asks for a vessel sized to minimise stop/start cycles, a cut-out point on the pump's performance curve chosen for the same reason, and an evaluation of pump types, sizes and quantities to improve sustainability; VSD pumps should be considered for all anaesthetic gas scavenging (AGSS) systems. Sites that are not open 24/7 should base medical gas demand on their working hours only.

A 2004 US Department of Energy tip sheet on compressed air notes that compressors running at part load are generally less efficient than at full load, and advises developing a pressure and demand profile before investing in additional controls.

Keep pressure as low as the system allows

The ULTRAOX datasheet (2022) states that every 1 bar increase in compressor pressure adds 7% to total electricity consumption, and the ULTRASEC dryer datasheet puts the extra power at about 7% of the installed motor power per bar. PATH and CHAI (2021) note that PSA energy consumption increases for higher service pressures and when cylinder filling is required. Among its tips for the rational use of oxygen, WHO's Foundations of medical oxygen systems (2023) advises monitoring and, when possible, reducing the working pressure of the pipeline network.

Find and fix leaks

A 2004 US Department of Energy tip sheet on industrial compressed air says leaks often waste as much as 20 to 30% of a compressor's output and that leakage rates increase with higher system pressure. It adds that fixing leaks once is not enough, recommends a leak prevention programme, and says compressor run time must then be reduced to match the lower demand. Methods for finding leaks in a hospital pipeline are on how to detect leaks in a medical gas network.

Do not over-specify oxygen purity

A Global Fund briefing note (3 April 2024) says that a plant specified at 95 ± 1% needs larger equipment than one at 93 ± 3% to deliver the same flow, with higher operating expenses from the increased power consumption. For reference, PATH and CHAI put a conventional PSA plant at approximately 1.2 kWh per Nm³ produced at 65 psig, depending on system efficiency and oxygen service pressure.

What the Ultra Controlo datasheets state

• ULTRAOX plants start and stop oxygen production automatically in response to demand from the oxygen distribution system (ULTRAOX datasheet 2022, p. 6).
• The variable speed ULTRASCREW compressor gives up to 35% energy savings (ULTRASCREW datasheet).
• At variable speed, the ULTRAVAC CLP claw vacuum pump can reduce energy costs by around 40% (ULTRAVAC CLP datasheet).
• An ULTRAOX enrolled in the UltraGreen programme runs on 100% renewable electricity, and Ultra Controlo states a 35% gain in energy efficiency compared with benchmark PSA installations.