12th International Symposium on District Heating and Cooling

The <strong>12th</strong> <strong>International</strong> <strong>Symposium</strong> on District Heating and Cooling,September 5 th to September 7 th , 2010, Tallinn, Estoniamax. 22 °C, therefore the condenser and sub coolerare equipped with Titanium tubes.The two compressors Uniturbo 33CX and 28CX arethen working in parallel, in a single stage mode, with asingle stage expansion, producing a cooling capacity ofup to 7MW plus 5MW = 12MW i.e. with 4 units a total of48MW.Depending on the cooling demand, one or the other, orboth compressors can be put in operation.If needed, the part load of each chiller / heat pump canbe controlled down to 10% of its nominal capacity, witha reasonable high efficiency, with the use of inlet guidevanes. The chilled water temperature outlet is keptconstant to 5 °C5.2 Combination of cooling and heating:During Spring, Autumn and Winter, with moderatecooling demand of up to 24MW, but simultaneous needof heating, the waste heat from the condenser issupplied to the district heating network at atemperature outlet of 78 °C and a maximum heatcapacity of 35.6MW.The two compressors Uniturbo 33CX and 28CX arethen working in series in two stage compression mode,with two stage expansion using an economiser afterthe first stage expansion.The compressor Type Uniturbo 33CX with the largervolume flow is working as 1st stage and the TypeUniturbo 28CX with the smaller volume flow as 2ndstage compressor.The control system is controlling the required coolingcapacity; the surplus heat is supplied fully to the districtheating network at a temperature level of up to 78 °C.I.e. this operation mode delivers heat which can besold in addition to the cooling, with a total COP ofabove 5.The cooling only mode and the combination of heatingand cooling mode are explained in the below P&I‘s:CONCLUSIONReliability of technology, future developments andchallengesAbout more than 140 heat pumps, producing hot waterwith temperatures above 70 °C, are installed worldwide since 1980. The heat pump plants described inthis article are only showing a small part of thenowadays available applications.Almost all of the installed heat pumps plants startingfrom the early 1980's are today still in operation, whichis showing the high reliability of this technology.Nimrod single stage operation2 compressors in parallel288Today developments are the extension of the heatpump operation range in temperature and capacity toexploit new heat sources and to extent the field ofapplications.The adaptation of the centrifugal heat pumps to newrefrigerants with GWP close to zero is already on theway.REFERENCESSea waterCooling capacity 12 MWNimrod two stage operation2 compressors in series28Heating water33Heating capacity 9 MWCooling capacity 6 MWText and pictures from Friotherm AG / Switzerland.260