| Heat Pump is 300% Better Than Boiler / Chiller Combo
Mitsubishi Electric’s ground source heat pump system has proved itself to be over 300% more efficient than a chiller / boiler combination in trials with a closed loop ground source ‘slinky’ coil.
The company, which has created the world’s first inverter-driven VRF ground source heat pump system, has been monitoring a City Multi WY Series water-sourced condensing unit linked to the slinky – a coil of plastic tubing buried horizontally in a 1.8m trench – at its headquarters building in Hatfield since the start of 2006.
The WY system proves itself to be an average of 338% more efficient than a boiler / chiller combination producing an average COP of 5.40, compared to 1.60 for the boiler / chiller. In heating mode the ground source heat pump system does even better delivering a performance that is 515% more efficient than a boiler (COP of 4.89 compared to 0.95).
“However you look at the results the ground source heat pump wins hands down,” explained Philip Ord, Mitsubishi Electric’s City Multi Product Marketing Manager. “WY costs an average of £2.10 per m2 per year compared with £13.10 for a chiller / boiler and produces 857.46 Kg CO2 emissions over the year compared to 2,089.40 Kg for the chiller / boiler system.”
The City Multi WY series, and its sister range, WR2, are the only air conditioning products to have been included on the Government’s 10% Renewable Energy Target list, which many local authorities are now using to review planning applications. The 10% Renewable list also includes solar, wind, photovoltaics and Biomass technologies.
The WY transfers heat to and from the slinky to provide the energy required to heat or cool the refrigerant circuit. The inverter driven system is also incredibly efficient at ensuring the condenser consumes the minimum energy needed to match requirements.
The slinky enables the system to benefit from the geothermal heat stored in the earth and, provided space is available, is a much more cost-effective method than sinking boreholes.
The water-sourced WY units can also transfer heat between the indoor units to further reduce energy consumption, and can also use a building’s sealed water loop to transfer energy between different refrigerant ciruits. As they are water-sourced, the condensing units are sited inside a building and their extended pipe run of 150m allows for greater design flexibility and no limitation on building size.
The R410A PQHY-P200YGM-A WY system installed at Hatfield, delivers a nominal Cooling Capacity of 22.4 kW and 25 kW of Heating and was linked to four PEFY-P50VMM-E ceiling concealed fan coils installed with linear slot diffusers to provide the heating and cooling to a 150m2 open plan office.
The system has been compared with a modern efficient boiler (with a COP of 0.95) and a chiller system that has passed the Enhanced Capital Allowance scheme requirements.
Date : 21-07-2006