Cool customer

The NHS is changing. Once upon a time it would not have been known for pouring its funds into ground-breaking projects with a view to long-term savings. If the price was right with the initial installation, you had yourself one happy customer, right?

Wrong. Or at least, wrong where the new Kings Mill Hospital is concerned. Skanska is approaching the final stages of an installation that is setting a benchmark for the way NHS hospitals are cooled.

Carbon cut-out

Mansfield’s newest infirmary will use a powerful ground-source system to create an impressive 5.4 MW of air conditioning. The technology, which consists of a network of heat exchangers submerged in the Kings Mill Reservoir nearby, will cut carbon emissions by at least three-quarters. The heat exchange is more efficient than that offered by conventional gas, oil and biofuel heating and other renewable-energy technologies.

Furthermore, the renewable system can also provide 5 MW of supplementary heating to the gas-fired boiler when air conditioning demands are low.

Geothermal International, a Coventry-based company that specialises in the field, was chosen by Skanska as a partner to develop and deliver the scheme.

“New hospitals tend to be PFI-funded, so for the past 10 years or so some have been looking more at longer-term models when financing this type of development,” says Karl Drage, operations director for Geothermal.

The system, which has taken a year to design and six months to install, is set to reduce running costs by thousands of pounds per year.

However, the 50-year financial model that is being employed on the PFI contract makes it difficult to predict the payback period.

“Nobody has really said, ‘OK, it would have cost us this much to install a normal system – this is the payback.’ They’ve built it into the 50-year running model of the hospital,” explains Drage.

Extra trade-offs

On similar geothermic projects, Drage says costs can be recouped in between two to eight years.

“The initial cost is probably a little higher than that of a traditional system,” he admits. “There are so many factors to take into consideration, though. Of course, there are elements of building work that a normal system might not have, such as pipes going under the road and out into the lake.

New hospitals tend to be PFI-funded, so for the past 10 years some have been looking at longer-term models when financing this type of development

“But you have to bear in mind the extra trade-offs. For example, with it being heating and cooling, we’re only using half as much kit as usual.

“Also, because we don’t need traditional fan coils, the cooling element is all in the basement or on the ground level, so there are no structural steels in the building.

“With a normal system, you’d need to install it on the top floor, there would be fan coils involved and you’d need twice as much space. So there are a lot of savings there that should be taken into account.”

Skanska is a partner in the PFI scheme, and is leasing the building back to the NHS for a 50-year period. The maintenance package is integral to the project.

Currently, Geothermal is waiting to see if it wins part of the maintenance package from Skanska. The two firms have worked together on numerous projects and have become strategic partners in geothermal operations.

The majority of Geothermal’s business consists of providing around 1 MW of cooling to London offices, universities and schools.

“The system is highly suitable for buildings of every size,” assures Drage. “The important thing is to ensure the m&e installation is integral to the building design from the early stages. The payback will then be larger, as you can maximise the efficiency of the building, such as getting your solar gains right.”

So, how does the lake loop technology work? Heat exchangers are connected via pipes to the hospital and heat pumps extract or reject heat from the reservoir to provide either cooling or heating.

Closed loop

When the water flows back through the heat exchanger plates, the temperature imbalance is partly restored by the reservoir without contamination, as the system uses a closed loop, with no reservoir water used directly.

For every kilowatt of energy used, 4-7 kW are produced, reducing both CO2 emissions and energy bills. The life expectancy of the heat pumps will also far exceed that of traditional plant.

Design teams consulted extensively with the Council and Friends of Kings Mill Reservoir, a local preservation group, to reassure members that the environmental impact of the system would be extremely low, and in some cases would benefit the ecology of the body of water.

One thing doesn’t seem to sit right when it comes to the company’s geothermic lake loops, however. If the technique is used in buildings as densely packed together as London office blocks, where are all the essential lakes and reservoirs? Is it only possible to choose structures that are set to be built within close proximity of this type of water supply?

You have to bear in mind the extra trade-offs. With it being heating and cooling, we’re only using half as much kit as usual

“In the city, we drill boreholes and we put a closed loop in, which is similar to the Kings Mill system, but instead of heat transferring into the lake, we transfer into the ground beneath the building,” explains Drage.

“We put these closed loops into structural piles, and every new building in London has a large number of structural piles.

“Or we can do an open loop, which is where we take water out of the aquifer, exchange heat with it and then transfer it back into the aquifer. And, of course, London sits on an enormous aquifer.”

Ground-source technology has been widely available in both the US and northern Europe for a surprisingly long time, with encouraging results.

Dabbled with ground-source

“Scandinavia has been using it for more than 50 years, and the US, where most of our technology has its roots, for the past 30 years. In the UK, it has only really started to come to the fore in the past 10 to 15 years. It has been available for a while in the UK, and people have dabbled with it, but it has only come to the fore in the past 10 years. And it’s only now that we’re seeing large systems like the Kings Mill Hospital.”

Drage believes we are a considerable step behind other countries, for a number of reasons.

In Sweden, for example, around three homes in 10 have ground-source systems, the reason being that the country does not have a gas grid. Homes are powered purely by electricity.

“If you install a ground-source heat pump over there, you’re immediately saving on your fuel bills by 75%. But in the UK we have a very good gas grid, and you would need to have a COP [coefficient of performance] of more than three on today’s gas prices for it to pay back. And of course, we all know what gas prices have done over the past 10 years.

“Compounded with that, in Scandinavia or the US, if you phone up a drilling company and say, ‘I’d like to drill some boreholes in my back garden,’ they know exactly what they’re going to find, whereas the geology in the UK is the most varied in the world.

“That increases installation costs. It’s only recently that oil prices have really driven the change.”

Last but not least, Drage presents us with the old adage that most within the m&e business should readily concur with.

“Old habits die hard, and I think there’s reluctance in industry to take on new things. That’s the case with everything.”