Netcare trials sub-cooling solutions for theatre complexes

Netcare trials sub-cooling solutions for theatre complexes

By Ilana Koegelenberg

When looking to reduce the cooling load of their power-hungry theatre HVAC equipment at Netcare Sunninghill and Netcare Krugersdorp hospitals, a pilot project using indirect evaporative cooling as an HVAC load reduction strategy was suggested.

It took almost two years for this project to get approved and underway. Its successful implementation was largely thanks to Peter Schilder, director at Cape Town-based Saftek Consulting, who did extensive research to prove the viability of this solution to Netcare.

Schilder first came across Seeley International’s Climate Wizard when he used it to cool a prominent Virgin Active club in Pretoria where the chiller simply could not keep up with the load. As he used to work in the health care industry for many years, he knew about the challenges hospitals faced in terms of thermal load of clinical areas. He got in touch with Johan Durand, Netcare’s environmental sustainability manager, to propose this as a possible solution.

Netcare Krugersdorp Hospital where one of the existing louvres was used to balance outside airflow. 
Image credit: Ilana Koegelenberg
At Krugersdorp, the Climate Wizards are ducted directly into the plant room via the existing fresh air louvre. 
Image credit: Ilana KoegelenbergInside the Netcare Krugersdorp Hospital plant room. 
Image credit: Ilana Koegelenberg
Image credit: Netcare

“On average, HVAC contributes to about 48% of our hospitals’ electricity consumption. That is why I am excited about this technology,” says Durand. It has the potential to save Netcare a lot — not only in energy savings, but also removing the need for expensive new plant room equipment. As the technology is easy to operate, it was appealing to simplify the often complex cooling systems found in health care settings.

The right solution

Although considered more efficient than mechanical refrigerant cooling, historically, the deployment of evaporative cooling in sensitive areas has been hampered by the negative effects of having high humidity present in the cooled air. This often leads to problems such as rust and high bacterial growth in the areas where such cooling us used.

However, Seeley International has developed an evaporative cooling system that resolves the classic humidity problem, yet retains the massive energy efficiency advantages of using such cooling. Their world-patented water-to-air heat-exchanger separates the air from where the evaporation process takes place. “This is known as indirect evaporative cooling and will change the way we condition air,” explained Schilder in his initial proposal to Netcare.

It has the potential to save Netcare a lot — not only in energy savings, but also by removing the need for expensive new plant room equipment.

“Not only does this technology save up to 80% in energy, it now becomes feasible to supply 100% fresh air to clinical areas such as theatres and ICUs as required by current South African National Standards (SANS),” explains Schilder. “Currently, most such areas are designed using the ASHRAE standard that allows for recirculating air. Using fresh air in these areas has significant comfort and clinical advantages but, up to now, has been prohibitively expensive to operate.”

Based on several site visits and simulations, Schilder proposed the installation of five CW-H15 Climate Wizard units in each of the main theatre air-conditioning plant rooms at Netcare Sunninghill and Netcare Krugersdorp hospitals to pre-condition ambient air.

Netcare00 7 inNetcare Sunninghill Hospital was selected for the first pilot study.
Image credit: Seeley International

“These units not only reduce the load on the existing central chilled water plant, they also reduce the theatre and ICU air handling unit (AHU) maintenance as the plant room is supplied with filtered cool air,” Schilder explains.

This solution also proved viable from the point of view that it could be implemented without intruding into the clinical area of the theatre’s clean air set-up. The new units simply pre-cool the existing plant rooms.

They are using 100% of the capacity of the Climate Wizard, while the existing chiller plant will only switch on to do the top-up if required when the outside ambient temperature gets too high.

Choosing the sites

Netcare Sunninghill Hospital was chosen as all the theatre AHUs are housed in a well-insulated plant room that would make measurement and verification (M&V) of the project fairly easy.

Due to space constraints, the Climate Wizards at Netcare Krugersdorp Hospital had to be placed on platforms. 
Image credit: Ilana KoegelenbergInside the Netcare Sunninghill Hospital plant room. 
Image credit: Seeley InternationalAt Krugersdorp, the controllers were placed outside. 
Image credit: Ilana KoegelenbergThe five units installed at Netcare Krugersdorp Hospital. 
Image credit: Ilana Koegelenberg

Netcare Krugersdorp Hospital was selected as the second pilot site for the same reasons. However, the theatre AHUs were already equipped with economy-cycle temperature and humidity control.

Two site visits were made to each site: the initial visits were to survey the sites and to ensure that the Climate Wizard units could be installed cost effectively. The second was by a professional team, which included the Seeley International engineering consultant from their factory in Adelaide, Australia.

Fresh air and cooling data of the AHUs were obtained from Apache (the OEM of the AHUs) to determine the fresh air requirement accurately.

The performance of the Climate Wizard units was then modelled based on real climate data. Based on the outcome of the modelling, a proposal was submitted to Netcare for consideration.

Calculating performance

Schilder tested the manufacturer’s claimed output specifications by calculating the performance using real hour-by-hour weather data and fundamental thermodynamic formulae.

He calculated that this modification would have a simple return on capital employed (RoCE) of less than two years based on current utility prices. The performance of Climate Wizards at both facilities was simulated using Microsoft Excel. The input to the model was actual hour-by-hour meteorological data for 2015 from weather stations closest to the respective facilities, the number of theatre AHUs, actual water and electricity prices of 2015/16 as published by the City of Johannesburg, and a refrigerant plant system coefficient of performance (COP) of 2.8.

Each site is equipped with plant monitoring so the team could see exactly how much the demand of the chiller has changed and the exact effect of the Climate Wizards.

Plant room set-up

The Krugersdorp HVAC plant room comprises multiple AHUs, one for each of the theatre suites, as well as other areas associated with a theatre complex such as pre-operative, recovery, and the central sterilising department (CSSD). Over and above the theatre plant, the hospital’s central fresh air supply and ICU AHUs were also located here.

At Sunninghill, the plant room is equipped with the same theatre plant; however, the vacuum and compressor plant that is located in a dedicated plant room next door also benefitted from the positive filtered pressurisation that the Climate Wizards provided.

Five Climate Wizard units were installed on the roof of the theatre complex at Netcare Sunninghill Hospital. 
Image credit: Seeley International The five Climate Wizards at Netcare Sunninghill Hospital were installed by Crown Technologies. 
Image credit: Seeley InternationalSunninghill installation in progress. 
Image credit: Saftek

In both cases, the plant room equipment is almost three decades old, but with Netcare’s preventive maintenance systems in place, it has been maintained to operate close to original design output.

Both Climate Wizard indirect evaporative cooling installations were placed outside on the roof and ducted into the plant room. Each system pressurises the plant room using five CW-H15 units, with each unit delivering 1 200ℓ of fresh air per second.

The air is also filtered. This will result in a positively pressurised, cleaner plant room and less dust in the theatre AHUs.

“It is remarkable that at Johannesburg design conditions of 32°C DB / 18°C WB, fresh air is supplied at 16°C using no more than 1.8kW of power per unit,” comments Schilder. The installation does in no way influence the design or operation of the current air-conditioning equipment. The only effect is that the fresh air drawn in by the existing AHUs is substantially cooler, resulting in less cooling from the central chiller water plant. The air is also filtered. This will result in a positively pressurised, cleaner plant room and less dust in the theatre AHUs.

While the AHUs at Sunninghill have fixed fresh air dampers, those at Krugersdorp had been upgraded to include an economy cycle. Outside temperature is sensed and fresh air louvres are opened up to take advantage of cool outside air if cooling is required. After the Climate Wizard units were installed, the units could take advantage of cool air permanently, even if outside temperatures soared to well above 40°C. Once temperatures exceed 45°C, the Climate Wizards really perform well with COP exceeding manufacturer’s ratings.

Netcare00 11 inNeil Britz of Crown Technologies (left) with Hennie Verster of Seeley International at the Sunninghill installation.
Image credit: Seeley International

If the outside temperature is below 22°C, the variable speed drive (VSD) of the Climate Wizard ramps down and stops. The AHU then draws from the outside air. The moment it hits 22°C outside, the VSD speeds up, pressurising the plant room. Initially, the controllers were placed inside the plant room, but it was found that far better control could be achieved by moving the controllers outside to control based on ambient temperature.

Savings and benefits

The financial feasibility was based on thermal efficiency alone and does not take into account any of the other benefits like savings on maintenance and extended useful life of equipment.

It is anticipated that minimal maintenance will be required as the units are self-draining. Cleaning the Climate Wizard filters will drastically reduce the cleaning interval of the theatre AHU filters. The overall effect will be that less man-hours will be required to clean filters.

For example, at Sunninghill, there are eight AHUs, each with up to 12 filters. The Climate Wizard only has four filters per unit. This drastically reduces the number of filters that need cleaning.

Another added benefit that wasn’t even factored into the return on investment is the fact that thanks to these units, the fresh air intake will be much higher than required under ASHRAE standards for theatres. This is bound to improve the working conditions and the general comfort and well-being of staff working in the theatres.

Installation

Both Sunninghill and Krugersdorp units were installed in September 2017. With careful planning and off-site manufacturing of many of the components, installation took just over a week for each site.

On the Netcare Sunninghill Hospital project, Crown Technologies did the installation, while the Netcare Krugersdorp Hospital installation was handled by Environmental Installation Services (EIS).

The Krugersdorp installation was quite a feat as the units had to be rigged rather high up and the roads around the hospital had to be closed off for this process. This was not the only challenge. The space that was originally allocated for the units was used for the solar PV installation so the team had to build platforms above the plant to house the units.

But it all came together in the end and things have been running very well since.

The system has an expected lifespan of about 15 to 20 years.

Possible DPSImage credit: Netcare

Future plans

Netcare is looking at adding an extra Climate Wizard unit at Krugersdorp to augment the cooling capacity of an existing chiller due to growing cooling demand, saving on CAPEX required for this replacement.

If Netcare is happy with the outcome of the pilot project, the potential exists that pre-cooling of plant rooms may be considered at the group’s other hospitals in future.

The system could also possibly be integrated with other ‘green’ initiatives such as grey water harvesting, which will make it even more cost effective and efficient.

List of professionals

 Owner    Netcare Group 
 Consulting engineer  Mechanical   Saftek Consulting 
 Contractors  HVACR    Crown Technologies 
   Environmental Installation Services (EIS)
 Product suppliers  Climate Wizard   Seeley International 
 Ducting    In-house by EIS and Crown

Click below to read the March 2018 issue of RACA Journal

RACA MARC 2018

06 Jun 2018
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07 Jun 2018
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FRIGAIR Expo 2018 - Day2
08 Jun 2018
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