School chooses renewable solution

schoolThe King Edward VII School in King’s Lynn, Norfolk became a specialist sports college in September 2000. The sports hall is a fundamental part of the school’s specialism but it had become difficult and costly to keep up with the heating requirement.

The heating was provided by two 100kW gas boilers which were over fifteen years old and had become unreliable and costly to maintain. In addition the energy consumption was excessive and led to high running costs.

As the client was keen to utilise renewable energy where possible, whilst still working within a budget, several options were considered including biomass boilers. However, air source heat pumps were chosen in favour of biomass due to the logistics of managing fuel deliveries and the on-site fuel storage required for a biomass system.

To provide a renewable and cost effective solution to reduce energy costs and carbon emissions the two 100kW gas boilers were replaced with a bivalent heating system.

The bivalent system comprised an air source heat pump acting as the primary heat source, supplemented by a single 100kW gas boiler. This provided the client with the perfect balance between the utilisation of renewable energy and affordability.

The Daikin Altherma Flex system was chosen for the heat pump as it offered the most economical answer to the provision of heating in the sports hall and would result in reduced carbon emissions. This was easy to incorporate with the existing heat emitter circuit and install within the available space.

The Flex system installed comprised of a single heat pump outdoor unit connected to three hydrobox modules to give a total heating output of 47kW. The modules were located in a plant room and are connected to the outdoor unit by small diameter refrigerant pipework.

As the existing heat emitters and low temperature hot water pipework in the sports hall were retained, a key requirement for the new heating system was to be able to produce a water flow temperature of 70?C. Although a challenge for most heat pumps, this was not a problem for the Altherma Flex system, due to its cascade refrigerant technology enabling it to provide water flow temperatures of up to 80?C maximum.

To maximise efficiency the heat pump includes weather compensation. This allows the heat pump to automatically vary the water flow temperature in line with the external temperature. So when the outside temperature drops the water temperature increases and vice versa. This helps to boost the overall efficiency of the system and to further reduce both running costs and carbon emissions.

In the bivalent system installed at the King Edward VII Sports Hall the Daikin Altherma Flex heat pump acts as the primary heat source and a new 100kW gas boiler acts as the supplementary heat source. A Daikin EKCCW sequence controller was installed to seamlessly manage the control of both the heat pump and the boiler.

The heat pump is expected to meet all the heating requirements down to an outdoor ambient temperature of 7?C. Once the temperature drops below this the sequence controller will run both the heat pump and boiler in parallel to meet the total heating load. It is estimated that for this project the heat pump will meet 70-75% of the annual heating demand with the remainder covered by the boiler.

The Daikin Altherma Flex system was installed by EOC Services, of Downham Market, Norfolk. Robert Hill, Technical Services Director at EOC commented: “As far as I am aware this is the first project of its kind in the UK so it was quite exciting to be involved in this. I am particularly proud to have been given the opportunity to work on this project as there were several design hurdles to overcome.

“Alterations were made to the existing pipework to accommodate all the new plant, a steel frame was designed to enable stacking of the Altherma indoor units, a buffer vessel was required to ensure that all of the circulation pumps were not fighting with each other. A plate heat exchanger was also required to separate the heat supply circuit which is pressurised from the open vented heat emitter circuit.”

The school’s Business Manager, Steward Bunting, said: “We chose the Daikin Altherma Flex system, after having gone to tender, as this provided us with the best value for money solution as well as decreasing our carbon emissions substantially.”

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