Ensuring a Healthy Power Supply

Paul Moore, managing director of standby power specialist, Dieselec Thistle, explains the business critical nature of standby power in a hospital setting and the specification criteria that should be considered to ensure that the installation meets the needs of the building and takes account of its surroundings.

The 21st century has been characterised by the green agenda and the drive towards lower carbon emissions and renewable energy. Globally we’ve made headway on this and, in the UK, political will and media awareness campaigns mean that we are more frugal with the energy we use, more critical of the energy we waste and more open to changes in the way we generate energy. Despite all of that, however, pressure on the National Grid has never been greater. We’re using more energy than ever before and, while the availability of sustainable energy is growing, it is by no means keeping pace with increases in demand.  The net result of all of this is that the risk of mains power outages is higher than it has ever been before. For hospitals, where the availability of a reliable power supply is not just business critical but could prove a matter of life and death, this is a very worrying risk indeed.

Of course, mains outages are nothing new: temporary faults, technical issues and bad weather can all affect the power supply.  However, as the risk of outages increases due to higher demands on the grid, and hospitals’ reliance on electrical equipment increases due to advances in medical technology, the need for standby power has never been greater. The good news is that advances in controls technology now means that hospitals can be switched to standby power systems almost instantly with the available load prioritised for the most critical services first. But designing such a system requires a high level of expertise and a collaborative process with the hospital that will factor in both its current and future energy requirements.


Reliable Supply

It is important, first of all, to understand the difference between a UPS (Uninterrupted Power Supply) and an SPS (Standby Power Supply) as the availability of a UPS system does not negate the need for a suitable SPS. Whereas a UPS system will ensure, as the name suggests, that there is no interruption to the power supply, preventing, for example, any loss of data because computers have crashed, it is a battery-based system providing limited power for a limited amount of time. In a hospital environment, therefore, a UPS system will not support the estate’s power requirements for a prolonged outage, for this the hospital will require an SPS system using diesel generators with sufficient output to maintain critical services until the mains power supply is back online.

In order to deliver this reliable power back up, the SPS system must include fuel storage provision as well as the generators themselves. There is a mandatory requirement for hospitals to store sufficient fuel on site to maintain 200 hours of fuel autonomy and this extends to the operation of the SPS generators. It is important to note that, due to changes in diesel formulation, which now usually includes a percentage of biofuels, fuel is prone to spoiling after a much shorter period of storage.  As a result, the fuel management strategy must not only consider the amount of fuel safely stored on site but also ensure that the available fuel remains fit for purpose at all times.


Location, Location, Location

Given the business critical need for both generators and fuel storage, one of the big design considerations for the SPS system is the location of the required kit.  The gen sets are not only bulky but heavy so need to be housed in a plant room or energy centre that is large and robust enough to take their weight.  The associated fuel is highly flammable so the location of the plant room or energy centre must also be factored into the design process and often means that the SPS infrastructure is located outside of the hospital campus or on the periphery of the estate.

Another clear consideration when deciding upon the location for the generators is the proximity of residential or commercial premises. When in operation, the generators are noisy and will cause a disturbance to close neighbours if noise attenuation is not installed to control noise levels. Of course, the SPS is available to provide power for emergency needs only and one would hope that it will not be required often; if at all.  However, as part of a thorough maintenance regime and due diligence strategy it will need to be tested on a regular basis so selecting a location where nuisance noise issues will not arise is preferable.  Clearly, the very nature of hospitals is that they are usually located in city or urban areas so an isolated location may not be possible.  As a result, the space, weight and cost of noise attenuation enclosures and silencers should be factored in to the specification.


Extra Safeguards

The power requirement specified for the SPS will vary depending on the size and nature of the hospital and it should also factor in any plans for future expansion or changes in services.  While it is possible to add gen sets into an existing system at a future date, this has implications in terms of the size and layout of the plant room or energy centre and will also involve modifications to the control system, so any future capacity required in the short to medium term should be factored in at the time of specification. For larger installations, where the SPS relies on multiple generators to provide the required load, additional capacity should be built into the system to ensure that sufficient load is available even if a generator should fail or be out of action for maintenance during an mains outage.

Indeed, it is not uncommon for a standby generator to be installed alongside the duty standby generator(s) as a double failsafe.  Dieselec Thistle has carried out many installations on this basis, including a recent SPS system at the new Victoria Hospital in Kirkcaldy, Fife.  Here, dual redundant starter motors and dual batteries were also included in the specification to provide as many assurances as possible that power would transfer smoothly to the SPS in the event of any mains failure. In hospitals, more than any other standby power application, the nature of the business critical need often underpins a belt and braces approach that leads to an ‘over-specified’ system in order to mitigate risk.


In Control

Probably the most complex area of the SPS system specification is the control system, which is required to ensure a smooth and rapid transition from mains supply to standby and to optimise and prioritise load sharing. This will be designed to meet the bespoke requirements of the hospital and here it is vital that the hospital’s management team works collaboratively with the standby power specialist to define the hospital’s requirements and prioritise the services that will require power soonest.

A pro-logic control system (PLC) can be custom-designed to trigger the switch-over to standby power and share the load effectively across the available standby generators. In this way, the hospital can be confident not only that critical services will be maintained but also that the standby generators will operate at optimum efficiency, maximising the available power. It’s important to remember that business critical services not only include life support machines, monitors and scanners but also lighting for both operating theatres and wards, nurse call systems and computing services.

At a current Dieselec Thistle project in Glasgow, for example, the design requirement was that ten standby generators would be available at full load, fully synchronised and connected to the hospital’s business critical electrical services within just 15 seconds.  To do this, each generator has been specified with its own control system and all 10 generator controls will be programmed to communicate with each other and with the central energy management system. The system will also be integrated with the hospital’s BMS which will alert the Engineering staff when the mains power fails and monitor the standby power installation for faults both during standby and activation.

This project is an exceptionally large installation but it does demonstrate the central role of the control system in the smooth running of the SPS. The challenges of correctly specifying the control systems not only include the controls for each individual generator but also the ability of multiple generators to synchronise and communicate effectively with other building controls. Indeed, Dieselec Thistle is often called upon to retrofit additional generators to existing SPS systems in order to increase capacity or replace old plant and this usually involves modifications to the control system to ensure effective synchronisation, integration with the BMS and load sharing optimisation.

The control system also plays a vital role in the regular testing of the standby generators required by HTM guidance. It ensures that the gen sets start and synchronise with the mains, close in parallel and ramp to the hospital load before opening the mains incomer and leaving the hospital in ‘island mode’ for the duration of the test.  When the load test command is reversed, power is synchronised back to the mains in the same process that the system would follow during a switch back to mains supply following and outage.

Tests & Maintenance

Routine testing of the SPS post-installation continues a testing process that begins in the factory where the diesel generators are custom-built to meet the exact requirements of the specification for an individual hospital.  Dieselec Thistle supplies FG Wilson generators, working closely with the company to ensure that the generator supplied meets the specification. Gen sets are usually factory witness tested before being shipped to site and mechanically and electrically installed along with the associated noise attenuation, fuel tanks fuel pumps and control systems.

These factory witness tests are vital as they not only ensure that the kit is in fully operational condition before it leaves the factory but they also provide an opportunity to identify any potential tweaks that may be needed to the SPS design. With any required changes carried out prior to installation, further testing is carried out as part of the commissioning process and these rigorous tests are fully documented as a reference point in case of any future maintenance or performance issues.

Once the system has been commissioned and is fully operational on site, a sustained maintenance programme is vital and this can be carried out in partnership between a specialist contractor and the hospital’s in-house maintenance team. The control system should be designed to identify any faults but the purpose of a maintenance programme is to address any potential issues before they arise. The maintenance regime should therefore include testing of the control system, mechanical upkeep of the generators and associated kit, and fuel management, including condition monitoring or the fuel itself and maintenance of fuel pumps.

Invisible Guardian Angel

Amongst all the state-of-the-art medical technology that goes into a hospital to diagnose conditions and save lives, the standby power system is not the most high profile or the sexiest area of specification……but it is equally vital. An important consideration for new build hospitals, it is equally crucial for existing hospitals where demographics, new treatment and diagnostic methods or upgrades to electrical services may have increased the power consumption over time, demanding a corresponding increase in the standby power capacity.

Whatever the requirement, this is one area of hospital design where ‘over-specification’ to provide additional safeguards is widely accepted. Most of those working in a hospital may never give the standby power system a second thought and hopefully, even if the mains supply should fail they still won’t have to worry about it because the generators will kick in smoothly and automatically to support the hospital’s energy needs.