Advanced ground source heat pump systems for heating and cooling in Mediterranean climate Advanced ground source heat pump systems for heating and cooling in Mediterranean climate

Building and UseBuilding and Use Heating & Cooling SystemHeating & Cooling System

EDRASIS HEADQUARTERSEDRASIS HEADQUARTERS

Vassilios Ramoutsakis, Vassilios Ramoutsakis, EDRASIS C. Psalidas SAEDRASIS C. Psalidas SAAngelos Goumas, Dimitrios Mendrinos, Angelos Goumas, Dimitrios Mendrinos, CRESCRES

Heating & Cooling SystemHeating & Cooling System

Borehole Heat ExchangerBorehole Heat Exchanger

Heat PumpHeat Pump

EDRASIS C. Psalidas SA is a public construction company located near the Athens airport. It hosts the corresponding Ground-Med demo site, in order to cover base load heating and cooling needs of its headquarters, which comprise the main hall, offices, conference rooms and lobbies.

Total area of the building : 2860 m2

Heating power demand : 249 kWCooling power demand : 273 kW

photo 3

photo 2

12 Borehole HEXs, PE 100/16 bar, closed loop, Double U, Ø 32 mm, water as working fluid.

GroutingAbove water level: bentonitic cementBelow water level: graded sand or gravel

Borehole Specifications Depth : 110 mDiameter : 165 mmSpacing : 6 m

Soil ParametersGeneral soil profile: clay and limestoneWater level: 30 mThermal conductivity: 2,016 W/m*KVolumetric heat capacity: 2,3 kJ/K*m³

Building location

Building plan

Heating

Cooling (Active)

Cooling (Passive)

BHE field

The heat pump used at the EDRASIS demonstration site is a prototype developed by OCHSNER Wärmepumpen specifically for the Ground-Med project.

It is an improved version of OCHSNER WP model OWWP56S. The machine uses one compressor and R407c as refrigerant.

The improvement focus was on COP optimization. For this purpose tasks carried out by the heat pump manufacturer included:• calculation and optimization of heat exchangers as evaporator and condenser, • design of optimum refrigerant distributor for evaporator with the goal of optimizing refrigerant-impingement for increasing the evaporation pressure on the refrigerant side, • theoretical calculation of the amount of refrigerant for all three refrigeration circuits,• interpretation of refrigerant lines• definition and dimensioning of heat pump components.

The result was a heat pump prototype of superior efficiency with 15% improved COP over the marketed machine.

Heat pump parameters at 10/6//30/35ºC are:

Heating capacity: 57,75 kWHeating capacity: 57,75 kWPower consumption: 9,76 kWPower consumption: 9,76 kWCOP: 5,92COP: 5,92Improvement: 15%Improvement: 15%

The heat pump prototype is water side reversible. This allows counter-current operation at both the evaporator and condenser in all modes, which results in maximum SPF.

Operation reversibility is achieved by 4 three-way valves, as shown in the figures at the right, which allow system operation in three modes: active heating, active cooling and passive cooling. The latter function is introduced in order to maximize system SPF, exploiting the low ground temperatures around the BHE during late spring when mild cooling is needed.

For heating operation the GSHP supplies only the fan coil units on a continuous basis. The total heating load of the fan coils is approximately 65 KW. Whenever the demand is more than 55KW, the existing boiler will be automatically connected by the BMS system.

For cooling operation the GSHP works on a continuous basis connected to the entire system (AHUs and FCUs) up to the its maximum power. When the system requires more than this, the existing chiller is connected to the system, automatically by the BMS.

GROUND SOURCE HEAT PUMPSUPPLIER : OCHNERMODEL: OWWP 56 iDIMENSIONS 695mm x 585mm x 1850mmWEIGHT 238 kgHEATING CAPACITY: 55 kW (40/35°C in heating circuit, 11/7°C in BHE)COOLING CAPACITY: 48 kW (6/10°C in cooling circuit, 30/35°C in BHE)REFRIGERANT: R407CCOMPRESSOR POWER: 9,75 kWe

WATER PUMP: WILO IPL32/160-1.1/2PUMP ELECTRICAL POWER: 1,1KWNOMINAL WATER SUPPLY 2,64 l/s