CASE STUDY

Taihape Hospital

  • 99% reduction in carbon emissions
  • 4 x ÖkoFEN 64kW modules
  • Output 256kW to 19kW, or 100% to 7%

 

Replacement for coal boilers with pellet boilers to reduce carbon emmisions.

The new pellet boiler system at Taihape Hospital was designed by Apricus Eco for Te Whatu Ora to ensure minimal disturbance or modification to the existing heating and hot water system. This meant that the remaining coal boilers could continue to operate undisturbed whilst the new system was installed and commissioned.

Continuity of operation is of extreme importance for a health service provider and parts of the previous coal boiler system were working adequately. This continuity was achieved by removing the second, defunct boiler, reusing the chimney connected to that boiler for the new pellet boilers and arranging the new system in the available space in the main plant room, all whilst leaving the other coal boiler undisturbed.

The boiler components in the new system are two ÖkoFEN PES112 boilers, which are made up of four 64kW modules, as a balanced duty cascade. The boilers are connected to the existing heating system through a small buffer to provide hydraulic separation from the existing LTHW system and a point for temperature control of the new boiler system. The system will circulate LTHW from the buffer to the existing heating manifold and domestic hot water calorifiers in the remote plant room. One of the existing flues has been reused for the new boilers. Two pumps, one duty one standby, have been installed in the plant room for guaranteed operation.

This modular cascaded design allows for a peak output of 256kW which meets the needs of the hospital. It also allows for greater resilience and redundancy with four independently operating boiler modules of 64kW. Each of these individual boilers can have maintenance undertaken separately, eliminating the need for any significant reduction in heat delivery during maintenance periods. Programmed as a balanced duty cascade, all boilers experience equal annual running hours which means even wear & tear over their lifetime.

The turn-down modulation range of a cascade boiler system is significantly improved compared to larger boilers, whilst maintaining the same level of efficiency at 93%. This system has a wide power output range of 256kW to 19kW, or 100% to 7%. The modulation range of the cascade ensures that the varying heat load is precisely fulfilled whilst burning the minimum amount of fuel. This careful control of fuel consumption ensures economic and efficient operation with the lowest possible running costs throughout the boiler’s lifespan.  Each boiler has a dedicated pump for primary circulation to the buffer tank adding in further redundancy and resilience in the system.

A single, smart controller manages the entire system
, this same single controller can have more boiler modules added to the system if there is a significant increase in the heat load of the building with new developments. These controls are easily accessed and managed in the plant room on the boiler and are also available online via a secure web portal and smartphone app. There are no charges for the online control system and an unlimited number of users can have access to the system via a secure portal.

The pellet fuel for the boiler system is contained in two ÖkoFEN Flexilo 8 tonne pellet stores, giving a total storage capacity of 16 tonnes or 81.6 MWh of heat energy. The pellet fuel is automatically drawn from the Flexilo bags via a vacuum system. The system has two fuel stores and two separate fuel feed systems, providing further resilience in the operation of the system. Should a blockage, fault or maintainance occur continued operation is guaranteed. The ÖkoFEN Flexilo pellet stores have significant design and construction features are unqiue in their innovation and technical merits. Pellets are delivered by blower trucks with deliveries likely to less than once per month in winter.

Emergency Situations

In the event of a power cut with an immediate, unintentional plant shutdown there is no negative impact on the ÖkoFEN pellet boilers status and once power is restored the boilers will restart automatically without any need for intervention or servicing. The boilers will continue to operate as usual under any power condition once supplied with 230V electricity, either from a generator or mains power. The boilers’ ECC combustion system is completely gas sealed and has multiple layers of automatic, passive burnback and overtemperature protections, many of them patented and unique to ÖkoFEN.

These ECC features combine to provide multilayer, failsafe burnback protection regardless of interruptions to the power. The design of these systems means there is no downtime to reset errors or fix components in the case of a power cut, however short or extended. The online monitoring system will send out an automatic email if there is an interruption to the boiler’s internet connection for more than 1 hour, providing another layer of alert to any issues at the site.

Planning for the Future

The other benefit of a modular cascade of boilers is its ability to adapt to building or structure changes without any reprogramming required. With the new pellet boiler system operational, the coal boiler can be removed and the second chimney retained. This second chimney will remain in place with adequate room beside it for use by additional pellet boilers if the load of the hospital increases in future and more heating capacity is required.