Mitsubishi enables low energy heating and cooling

Business Solutions Partner with Mitsubishi Electric, J and B Hopkins, has used its headquarters in Concorde Way to show a highly energy efficient way of controlling the temperature within buildings.

The design and build company has just released details of the system which uses low temperature heating and high temperature cooling.

J and B Hopkins is using its to demonstrate that this approach can be replicated in almost any commercial building.

Hopkins and team have been innovative in installing underfloor heating on both floors and have also included ceiling panels with embedded pipe work to allow for cooling or heating via the ceiling.

The combination of underfloor pipe and over-ceiling systems radiates heat from both the floor and the ceiling during the heating season, or in the summer cooling season, creating an artificial thermal mass that is typically kept at between 16-19C.

This enables the building to benefit from what Hopkins calls the 'Cathedral Effect'; heat from the occupants and electrical equipment is absorbed by the cooler ceiling and floor.

The floor systems typically need longer periods to create a constant thermal temperature as opposed to the ceilings where there is generally an instant reaction from the temperatures introduced through the pipework in both heating and cooling.

The company uses flow temperature of 30C in heating mode and in cooling, the traditional need for temperatures of 10C or less is a thing of the past.

The comfort is greater in this building even with a higher (summer) dry bulb internal air temperature.

The human body temperature is around 37C and the heat in the body radiates to the cooler ceilings and floors.

This allows the overall temperature needed for cooling to be higher than usual.

The reverse is true for heating and this keeps the differentials low and helps reduce energy consumption.

The overall effect is one of comfort in a steady condition.

The ventilation requirement for the building is reduced because the air services only need to deliver fresh air to people.

Fully ducted heating and cooling systems typically need more air volume to carry the requisite heating and cooling loads.

Delivering only the required amount of fresh air to the occupants of the building and using a filtered heat recovery system, minimises the amount of energy needed to heat or cool the fresh air.

It also reduces the impact of ductwork in the building (less air volume therefore smaller ductwork), reduces the size of the air plant and, therefore, reduces the ventilation fan's motor sizes and duties.

The system also uses night-time cooling in the summer to purge the building ensuring it starts the day with a fresh and cool internal environment for the employees.

Another benefit is that the building has less static because the fresh air has not had its humidity over reduced.

BSRIA (The Building Services Research and Information Association) will now be monitoring the building and systems within it, once the control systems have been linked to the underfloor heating system, and this will also give Hopkins a chance to introduce more automation into the system.

At the core of the system are two Mitsubishi Electric City Multi water sourced WR2 DX ground sourced heat pumps, two City Multi Air sourced R2 DX heat pumps and four PQFY sanitary water heating systems giving a total of around 110kw delivered active heating or cooling.

The WR2 heat pumps are fed from the pipe coils buried in the car park, in a twin stack, providing around 4,000m of piping.

The geothermal slinky pipe work is able to deliver around 120kW of cooling and 100kW of heating to the building.

This is being used passively during the early and late periods of the cooling season, where the cooling energy in the geothermal pipe work is extracted by using a plate heat exchanger and inverter driven pumps.

The use of both the City Multi WR2 water sourced units and the R2 air sourced units was designed to give Hopkins maximum effective control of the building's conditions based on the outdoor air temperatures and the ground sourced water temperatures, allowing the building to use the energy in its most effective and conservative means.

Further use of energy within the building allows for the absorption of heat gained from the occupants, lighting, computers and printers etc.

This is then circulated around the building.

The underfloor and ceiling panel system provides a more balanced building so that if the sunny side is getting hotter, this heat is moved to the north side of the building to deliver building services working in equilibrium.

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