A healthy power supply
Scotland’s largest hospital complex at Foresterhill health campus in Aberdeen, supports the wellbeing of around half a million patients each year.
Today, Foresterhill Health Campus, jointly owned and occupied by the NHS and the University of Aberdeen, has established itself as one of the largest clinical campuses in Europe. A reliable, stable and efficient heat and power supply is critical to keeping Foresterhill operational around the clock, 365 days per year.
As Gary Mortimer, General Manager – Facilities and Estates at NHS Grampian explains: “80,000 people spend time on our wards during the course of a year, with more than 500,000 outpatient visits. Including visitors, close to a million people pass through our gates in a given year, and the site is packed with equipment focused on people’s health and care, including sophisticated diagnostic aids like MRI and PET scanners and imaging kit.
“A lot of power is needed to support such a constantly high level of activity, and our energy costs for the campus are in the order of £6 million a year.”
Capacity, cost-effectiveness and low environmental impact were uppermost among the selection criteria when deciding on the scope of supply for new power generation equipment. NHS Grampian also needed to ensure that the selected technology could easily meet future anticipated demand levels.
Rolls-Royce 501 gas turbine technology was selected as the heart of the power system. “The plant has to offer site resilience over the next 15-20 years to match planned expansion and modernisation. We have invested £110 million alone in the past 12 months, for example, commissioning a new nine-storey, 400-bed emergency care centre that co-locates Accident & Emergency, our ‘out of hours’ GP services, and the ‘NHS 24’ contact service. This co-location gives a single and flexible focus to emergency patient care. In collaboration with our university partners, we’ve also built a new dental hospital and education centre, and also completed the energy centre itself,” points out Gary Mortimer.
Foresterhill’s demand for power and heat certainly never reduces. With such a challenging mix of criteria and the need for sustainability, Gary Mortimer’s team engaged the Carbon Trust to assess an outline plan that included new plant with a biomass element. The scheme, which evolved over a couple of years, was well over the level of capital investment that required sign-off by NHS Grampian, NHS Scotland and the Scottish Government Health Directorate.
A combined heat and power (CHP) based solution was ultimately chosen for the new energy centre.
It cost £13.5 million and comprises a 5.2MW Centrax power generation unit incorporating Rolls-Royce 501-KB7 gas turbine technology.
Derived from the T56/501 family of aero engines that have flown well over 200 million hours, around the world the industrial variant of the 501 is acknowledged for its reliability and simple maintenance. The industrial 501 has itself accumulated over 110 million running hours in service with 500 energy customers in 53 countries. Other major hospitals in the UK that use Centrax generating plants powered by the Rolls-Royce 501 include, Dundee (2.6MW), Leeds (4.8MW) and Queen Elizabeth Hospital Birmingham (3.6MW).
At Foresterhill, the 501-powered Centrax package operates in combination with a waste heat boiler, augmented by the biomass boiler and two dual-fuel boilers to meet the huge heat and power requirements demanded by the site. The plant is configured to deliver ample inherent flexibility in order to ensure business continuity at all times. It is a heat-driven solution modelled on the coldest reasonably imaginable winter, from which peak requirements are calculated based on heat demand.
“We need a heat load to generate maximum electrical output,” explains Graham Mutch, who is Head of Maintenance at Foresterhill, “but during the summer we don’t need such a considerable amount of heat. The flexibility of the gas turbine is a clear advantage under these varying conditions.
“We achieve a good balance between gaining maximum efficiency out of current load while being able to meet projected loads well into the future, providing about 90 per cent of the power we need ourselves,” adds Graham.
The remainder is imported from the national grid, which could provide all electricity in the unlikely event of an unscheduled outage – and would be used during scheduled maintenance of the gas turbine package. Nothing is left to chance, and an additional failsafe comes in the shape of 21 generators strategically positioned in key locations, just in case power is lost in a particular zone.
While the plant’s operational regime precludes exporting power, the advantage of producing its own power and being largely independent of the grid is a £2 million annual saving in energy costs.
The 1.5MW biomass boiler, which burns woodchips, is only employed in the winter during periods of highest demand for heat when up to 12 tonnes of steam per hour is provided.
“The steam is very much the site’s life-blood,” stresses Gary Mortimer. “It is used for heating, ventilation, hot water, cooking and laundry, and for safety-critical services such as sterilisation.”
Plentiful steam is generated by three main boilers – two rated at 8.5MW and one at 6.5MW – which are dual-fuel, capable of running on natural gas or liquid fuels. This helps plant economics – as they use the cheapest fuel (usually gas) – but also guards against any supply interruptions the site’s facilities management have no control over. They can switch to liquid fuel at very short notice, with a week’s supply stored on site. Reliability, economic and capacity criteria are all comfortably accommodated by the new energy centre, and its environmental credentials are pretty impressive, too: so much so that Foresterhill’s energy centre was adjudged winner of the industrial category of the BREEAM (British Research Establishment Environmental Assessment Method) awards in 2012.