Recovery of the waste heat by large capacity heat pumps for Riga ...

Recovery of waste heat by large capacity heat pumps for Riga city 5(26)district heating systempump / chiller. That heat is provided by DHP own steam boiler. Total cost for theproject is amounted to 696 665 EUR.Picture No 2. Layout of the heat pump connectionTaking into account the constantly rising prices for natural gas, and implyingits annual consumption savings to the 842,000 m 3 , the project is expected to repayin three years. The payback period will be accelerated by the state implementedexcise tax on the natural gas, which is also expected to rise in coming years. Inaddition to the mentioned above, the project will save annually about 1580 CO 2emission quotas and reduce the consumption of chemically treated water for atleast 30%. The technical solution of heat pump / chiller implementation is specifiedin the picture No2, see abowe.Brief description of the CHPCurrent equipment:- Gas turbine Rolls Royce RB 211-24GT, 31,52 MW el ;- Heat recovery steam generator Transelektro Power 63 T/h, 67 bar;- Steam turbine B+V Industrietechnick MARC 4-H01, 16 MW el ;- Steam boiler Vapor, 12 t/h, 13 bar;- An absorption chiller BROAD BDS183X0.4-65/47-29/55-300-Fb-Mb.The total installed capacity of the CHP equipment is 48 MW el and 48 MW th(without an absorption chiller), and along with working at full capacity chiller is 53MWth.After the CHP erection, during the heating season water boilers operate inparallel with the CHP and in the summer time are in a state of reserve.

Recovery of waste heat by large capacity heat pumps for Riga city 12(26)district heating systemtowers. When the ambient temperatures are below -10°C and there is anincrease in the return water temperature, for the cooling providing it isnecessary to consume a much greater amount of heat energy in the form ofsteam. The number of steam consumed for cooling of the same amount ofenergy at the min and max T2 differs up to 100%.3. The important point is the load condition of the heat pump/chiller. Dependingon the principle of the cogeneration plant, the unit can be designed for workduring the heating season only or also in the summertime with the low heatloads. In the summertime it would be efficiently to use steam extraction fromthe steam turbine. In Latvia the duration of the heating season in average isabout 5200 hours per year. The ability to provide the heat pump working atfull capacity beyond the heating period falls very rarely; usually CHP heatload in the summer period is only about 12% comparing to the loads of theheating season and in result the heat pump’s heat reduces the power outputof the CHP. In our case, the installed heat pump is intended to be usedprimarily in the heating season time.4. Extreme important is to make the correct choice of the critical parameters. Inour case the temperature a cooling loop should to provide is +29°C (theoptimal temperature range of 26-27°C). The capacity of the heat pump/chilleris limited by the maximum heat load, which is defined by the installation ofthe parameters guaranteed. This temperature at the outlet of the heat pumpshould not be lower than the expected maximum T2, otherwise there mightbe a need for the compensation of the insufficient cooling capacity at high T2.5. Steam condensation problem. Usually for the needs of CHP it is used thesteam with the high quality standards; for a boiler house own needs, in turn, itis used the lower quality steam, and the mixing or switching from the onetype of carrier to another could be a problem in result.6. When the heat pump is in the continuous operation mode and in case ofabsence of the heat insulation, the significant heat loses can occur. Carriedout heat pump thermograph had helped to improve significantly its thermalinsulation, thereby increasing equipment efficiency, reduce the roomtemperature and reduce the amount of the heat losses.7. The most sensitive element of the project is the natural gas price. The pricerise faster payback, and in our case, taking into account the current highprices, it is extremely important.Further studiesAs an effective solution to reduce the amount of the consumed steam for thecooling process at ambient temperatures below -10°C and the return networkheating water temperatures above +47°C the boiler’s air heater utilization ispossible.Thus, all the heat energy for the selection of which it is necessary to spend alot of steam, could be used for the air heating with a standard heater. In our casewe will study the possibility to cool the return water or the technological water of theCHP with the standard air heaters in two air ducts of the boiler KVGM-100. Thepicture No 8 shows a conventional air heater, which can be adapted as a districtheating return water cooler to the effective temperature range.

Recovery of waste heat by large capacity heat pumps for Riga citydistrict heating system13(26)Picture № 8. A conventional air heater КPB-12 for the boiler KVGM-100The mentioned above boiler is already equipped with a condensingeconomizer, which enables boiler efficiency increasing higher than 100%(corresponding to the lowest heating value of the natural gas), thus making studyeven more actual.This improvement would provide an opportunity to reduce steam consumptionfor 0,5 t/h at an average and increase the boiler efficiency up to 0,5%, which atmean seasonal load 80-90 MW is quite a remarkable value.In the foreseeable future, the obtained experience is intended to apply in thegeothermal projects implementation, which, in turn, without thorough understandingof the heat pump technology is absolutely impossible.Projects under developmentDuring the project implementation has been evaluated future projects. As the mostattractive locations for coming years have been identified the following locations: Riga Combine Heat Power plant (CHP)-1; Riga CHP 2; Daugavgriva Biological sewage water treatment plant.Both power plants have similarities with the already realized project and biologicalsewage water treatment plant project type has analogues in the nearestneighbouring countries. Due to that the subject has the high priority; Riga TechnicalUniversity engaged students and scientists in the research work. As an outcomecame three bachelor diploma works dedicated for all three subjects, as well aspublication prepared by Latvenergo employees in local technical journal . For moredetailed information see sources ( 9 ; 10; 11; 12) and presented information below.Installation of heat pump in the Riga CHP1Brief description of Riga CHP 1Riga CHP-1 is combined cycle cogeneration power plant with installed netelectric capacity 144 MW and heat capacity 490 MW, including 348 MW from heatonly boilers.

Recovery of waste heat by large capacity heat pumps for Riga city 14(26)district heating systemThe investment decision about reconstruction of Riga CHP-1 was supportedby several pre-feasibility and feasibility studies. The EPC turnkey contract for theimplementation of this project was placed with the Siemens industrial gas turbinebusiness in Sweden “Demag Delaval Industrial Turbomachinery AB” (earlierALSTOM Power Sweden AB) on 30 June 2003. The power plant wascommissioned on 10 November 2005. All the existing CHP units and HOBs weredecommissioned.Capacity of the new CCGT CHP units was chosen in accordance withsummer heating loads. That is why it operates solely in cogeneration mode. Thenew CCGT plant supplies district heating to the Right bank heating networks ofRiga. The main components of the CCGT plant are two natural gas fired (singlefuel) 43 MW GTX-100 gas turbines equipped with dry low NO x combustion systems,two heat recovery steam generators with supplementary gas firing and one 54 MWback pressure district heating steam turbine MP 24. In addition three new HOBsKVGM-100 (produced in Russia), burning natural gas and diesel fuel with total heatcapacity 348 MW are installed.The rehabilitation of Riga CHP-1 allowed reducing significantly theconcentration and emission of harmful substances in the atmosphere in comparisonto the old plant (approximately by two times). Emission of sulphur oxide, vanadiumoxide and solid particles are prevented completely, but NO x emission is significantlylower than the approved normative for Riga CHP-1.Picture № 9. Technological scheme of Riga CHP-1Riga CHP‐1 heat pump projectInstallation of absorption heat pump with gas burner was selected as thefeasible option to improve efficiency of Riga CHP-1, to increase its heat capacity, aswell as availability and flexibility of main generating equipment. Heat pump will usea low potential heat of cogeneration unit’s cooling system to produce heat energyfor district heating system of Riga.Overall heat capacity of the heat pump is considered to be 11.6 MW, whileutilised latent heat of the cooling system of cogeneration unit is estimated to be 4.46MW. According to preliminary calculations, the overall project cost could beapproximately 1.2 million Ls.

Recovery of waste heat by large capacity heat pumps for Riga city 15(26)district heating systemImplementation of the Project would allow to reduced natural gasconsumption, reduce CO 2 emissions and increase the output of the power plant.Parameters of the cooling system of Riga CHP‐1Steam turbine MP24DH of Riga CHP-1 is a backpressure turbine. That iswhy it does not have a condenser and a cooling system with cooling towers. All thelow pressure steam after the turbine is delivered into district heating water heaters.This cogeneration cycle allow to achieve a very high fuel utilisation efficiency of87.7%. But the only heat available for further improvement of cycle efficiency is theheat from closed cooling system of main generation equipment (2 compressors, 2gas turbines (GT), 1 steam turbine (ST), 3 electric generators, 2 heat recoverysteam generators (HRSG) and other auxiliary equipment).It might be feasible to install absorption heat pump to use latent heat from thecooling system of cogeneration unit in Riga CHP-1. The key criteria and limitationfor selection of optimal capacity of heat pump are available low potential heat from acooling agent and necessary high potential heat from external source (steam, hotwater or combustion gases). In case of Riga CHP-1 it is recommended to use anabsorption heat pump with integrated gas burner (as a source of high potentialheat).Input data for calculation of heat pump capacity are input/output parametersand flow rate of cooling agent Temper-30, as well as calculated capacity of acooling circuit for two possible cases: 1 GT+1 HRSG + TT - when the half ofcogeneration unit is in operation and 2 GT+2 HRSG + TT, when all equipment is inoperation.According to the design data, capacity of a cooling circuit is 8.6 MW in caseall the equipment of Riga CHP-1 is in operation and 4.45 MW in case only half ofcogeneration unit is in operation (Table 2).Table 2 Design data of Riga CHP-1 cooling systemTotal heat, MWComponent 2 GT+2 HRSG+TT 1 GT+1 HRSG+TTNatural gas compressor cooler 2.850 1.425Gas turbine GTX 1 generator cooler 0.688 0.688Gas turbine GTX 1 lubrication cooler 1.060 1.060Gas turbine GTX 2 generator cooler 0.688 -Gas turbine GTX 2 lubrication cooler 1.060 -Steam turbine generator cooler 0.740 0.370Steam turbine MP24 lubrication cooler 1.100 0.550Heat recovery steam generators 1 & 2 sample coolers 0.116 0.058Auxiliary equipment coolers 0.300 0.300Total 8.602 4.451Water temperature, °C 37 48Calculations of main parameters of a heat pump are performed based on realdata from Riga CHP-1 control and monitoring system (CMS). Operational statisticfor the October 2010 was used. One gas turbine, one heat recovery boiler andsteam turbine (1 GT+1 HRSG+TT) were in operation at that period. Thetransformation coefficient (COP) for one stage absorption heat pump was assumedζ= 1.6. Calculated parameters are shown in Table 3.

Recovery of waste heat by large capacity heat pumps for Riga citydistrict heating system16(26)Table 3 Calculated parameters of Riga CHP-1 heat pump# Parameters 1 GT+1HRSG +TTPartial load2 GT+2HRSG +TTNominalload1 Inlet temperature of a cooling circuit 27 30 482 Outlet temperature of a cooling circuit 23 23 373 Nominal flow rate of a circulating pump, m 3 /h 813 813Density of cooling agent Temper-3034 at average temperature 25°C, t/m1.17 1.175 Nominal flow rate of a circulating pump, t/h 951 9516 Rotation speed of a circulating pump, % of nominal load 88% 89% 100%7 Flow rate of a circulating pump at partial loads, t/h =(5)*(6)/100) 837 847 957.68 Flow rate of a circulating pump, kg/s (=(7)/3.6 233 235 2669 Specific heat capacity of Tempera-30 (C p ), kJ/(kg*K) 3.15 3.15 3.1510 Necessary cooling capacity, MW (=(9)*(8)*((1)-(2))/1000) 2.93 5.19 8.8211 Latent heat, MW (based on (10)) 3.0 6.0 9.012 Heat input of a heat pump, MW (=latent heat/0.6) 5.0 10.0 15.013 Heat output of a heat pump, MW (=(11)+(12)) 8.0 16.0 24.0Absorption heat pump with integrated gas burnerAbsorption heat pump with integrated gas burner might help to solve theproblem with inefficient operation of cogeneration unit in certain regimes. Usuallysuch regimes are observed in summer, when half of cogeneration unit is inoperation (1 GT+1 HRSG + TT) with nominal capacity (about 64 MW), but heatdemand is increasing, for example for 5 MW. In this case, the operators are forcedto switch on one heat only boiler at its minimum capacity, which is 11 MW. It meansthat cogeneration unit capacity shall be decreased by 6 MW with further losses fromreduction of electricity and heat production in cogeneration mode.Picture № 10. Absorption heat pump with integrated gas burnerFor the absorption heat pump, a latent heat from the cooling circuit of a RigaCHP-1 cogeneration unit is used to produce a useful heat for the district heatingsystem of Riga (Picture 10). Heat pump shall be connected in parallel tocogeneration unit and heat only boilers. The maximum output capacity of a heat

Recovery of waste heat by large capacity heat pumps for Riga city 17(26)district heating systempump is selected to be equal to minimum capacity of a heat only boiler of RigaCHP-1, which is approximately 11 MW.Table 4 Possible operation regimes of the heat pumpCalculatedregime,11.6 MW1 GT+1 HRSG + TTadditional 3.3 MW2 GT+2 HRSG + TTadditional 8.3 MWParametersNatural gas consumption of a heat pumpat LHV Q d z = 8300 kcal/m 3 , m 3 /h 710 200 510District heating (DH) water consumption, m 3 /h 300 87 300Cooling agent consumption, m 3 /h 957 250 705Return DH water temperature, °C 50 40Supply DH water temperature, °C 90 70Temper-30 temperature in the inlet, °C 40 25 30 25 30Temper-30 temperature in the outlet, °C 35 20 25 30 25Loading of heat pump, % from nominal 90 60 100 60 100Additional heat capacity, MW 10.4 2.0 3.3 5 8.3Electricity self consumption, kW 31.0 9.5 21.5For simplification of calculations, let us assume the district heatingparameters (return/supply water temperature) correspondingly 40/70 °C. Dependingon the temperature of a cooling agent in the outlet of the heat pump and assumingthe temperature drop in the heat pump around 5 °C, its capacity could bedetermined. Possible operation regimes of the heat pump and its capacity,depending on the temperature of a cooling agent are shown in the Table 4.One of the key assumptions - the heat pump is able to operate with minimumheat capacity of 1 MW and is flexible in the range from 1 MW to 11 MW. Overallheat capacity is 11.6 MW, while latent heat (heat necessary for the cooling systemof cogeneration unit) is 4.46 MW.Planned performance of the heat pumpEnergy generation program is calculated for two possible options: with andwithout heat pump (HP) installation (Table 5). Comparing these options, it ispossible to conclude: as the result of installation of heat pump, heat production ofheat only boilers will reduce by 38.2 GWh, while output of cogeneration unit willincrease by 12.3 GWh. Consequently, absorption heat pump will produce 26.1 GWhof heat energy.At the same time, electricity production of Riga CHP-1 will increase by 12.1GWh. Installation of heat pump allow to enhance fuel efficiency of Riga CHP-1.Table 5 Energy generation program for two options: with and without heat pumpMWhHeat production Power production Fuel consumptionwithout HP With HP without HP With HP without HP With HPRiga CHP-1 666 590 678 881 656 818 668 906 1 472 199 1 499 195Riga CHP-2 1 852 128 1 851 963 2 402 797 2 402 649 4 932 944 4 932 590Heat only boilers 148 341 110 107 - - 160 634 118 835Heat pump (HP) - 26 127 - - - 17 386Total 2 667 058 2 667 078 3 059 616 3 071 555 6 565 777 6 568 006During the heating season, heat pump starts to operate only at temperaturebelow -8 ºC, when cogeneration units of Riga CHP-1 and CHP-2 are fully loaded atnominal capacity. Practically, heat pump allows to replace 11.6 MW of heat onlyboiler capacity. In comparison to other heat sources, its contribution in heat balanceis not significant. (Picture 11).

Recovery of waste heat by large capacity heat pumps for Riga citydistrict heating system18(26)1200RTEC-2-1 RTEC-1 SS RTEC-2-2 ŪSK1000800MW600400200stundas01 49 97 145 193 241 289 337 385 433 481 529 577 625 673 721Picture № 11. Heat production for the option with installation of the heat pump (January)During the summer period, the heat pump shall partly or entirely replace heatonly boilers, providing better utilisation of cogeneration unit (Picture 12).Consequently, electricity and heat production in cogeneration mode shall increase.120RTEC-1 SS RTEC-2-1 RTEC-2-2 ŪSK10080MW6040200stundas1 49 97 145 193 241 289 337 385 433 481 529 577 625 673 721Picture № 11. Heat production for the option with installation of the heat pump (July)Economic evaluation of the projectInstallation of 11.6 MW absorption heat pump with integrated gas burnerevaluated cost is close to 1.23 million Ls, including equipment, construction andcommissioning cost.According to economic evaluation, installation of heat pump shall pay off in11 years, while the Net Present Value (NPV) for the 10th year of operation shall be672 thousands Ls, but Internal Rate of Return (IRR) 14.4%.

Recovery of waste heat by large capacity heat pumps for Riga citydistrict heating system19(26)Cooling systemLocation of heat pumpPicture № 11. Location of absorption heat pump in Riga CHP-1Comparing to the Imanta DHP, Riga CHP1 and CHP2 are working in thesame DH network, as well as cogeneration penetration level is considerably higher,which in particular case create problem with commercially acceptable repaymentperiod. Project can be feasible if EU co-financing would be available.Potential location of a heat pump in the territory of Riga CHP-1 could benearby to the administration building and control room. The benefit of this location,is that it is free of any construction and communications.Picture № 11. Cooling system of Riga CHP-1

Recovery of waste heat by large capacity heat pumps for Riga city 20(26)district heating systemAll chapter material is based on information and initial visual materials presented insource No 11 and 12.Installation of heat pump in the new power unit of Riga CHP-2Brief description of Riga CHP 2.Riga CHP-2 is the largest combined heat and power plant in Latvia. Its first waterheatingboilers were launched in the period from 1973 to 1992 and four powergeneratingsteam boilers and four steam turbines (CHPP’s power-generatingsection) – from 1975 to 1979. Presently, the installed electrical capacity of TEC-2 is330 MWel and its thermal capacity – 1148 MWth. As planned construction of a newnatural gas full combine cycle power unit at TEC-2 completed at the end of 2008.As a result, TEC-2 became the most advanced electricity and heat power plant inthe Baltic region with increased overall reliability of electricity supply in Latvia.After the construction of the first modern combine cycle power unit, the generationof electricity in cogeneration mode increased from 820 GWh per year on average to2200 GWh per year on average, providing Latvia with approximately 1400 GWh ofadditional electricity per year. Coming to the final end another analogous highcapacitypower unit, commissioning is expected in 2012. As a result, will be possibleto close down completely the existing outdated less efficient power-generatingsection of TEC-2. As a result of this modernization, significant increase in the powerplant’s electrical capacity and electricity generation amount is expected in 2012.Taking in account that combine cycle emits remarkable amount of low grade heat.In 2009, TEC-2 generated 909 GWh of electricity. Riga CHP2 is the biggestpower plant of Riga connected to the Riga right bank district heating network.Riga CHP‐2 heat pump projectProject evaluation has been done in a bachelor diploma work. The main taskof project for installation of heat pump in the new power unit of Riga CHP-2 was toconsider the best possible ways of introducing a heat pump technology with the aimto utilize medium or low grade waste heat on the new power unit CHP-2, which wascomissioned in 2009. Project examines and compares the CHP-2 unit heat pumptechnical and economic efficiency. The main two types of heat pumps: theabsorption and compression has been examined.The aim of the work - creating a cost-effective, energy-efficient heatingsystem model for CHP-2, to ensure compliance with the heating load, usingcogeneration equipment connected heat pumps. The main requirement is to providethe heating needs by utilization of available low-potential heat.Evaluation of the project required deep dig in the basics of heat pump or chilleroperating principles, as well as revue of the plant design. The thermodynamic cyclerequired the calculations to determine the main heat-pump parameters, as well aswas carried out, namely, heat transformation ratio, specific fuel consumption of 1kW of heat and heat pump capacity of basic elements.Thesis includes thermal engineering calculations of the basic design and hydrauliccalculation of the absorption heat pump, as well as held exergy analysis of heatpump installation.

Recovery of waste heat by large capacity heat pumps for Riga citydistrict heating system21(26)Picture No 12 CHP-2 new block heat pump connection schemeAs a source of heat for heat pump generator heating was selected extraction steamfrom combine cycle steam turbine and low grade heat from open type coolingtowers is planned to use as source of energy supplied to the evaporator ofabsorption heat pump. The main heat recovery scheme available in the picture12.Open cooling tower system of CHP2 is presented in the picture 13.Picture No 13 CHP-2 the new combine cycle cooling tower systemThe main conclusions about the reasons to implement heat pump installation forCHP-2 with the aim to reduce emissions and reach extra ecological effects are asfollows:

Recovery of waste heat by large capacity heat pumps for Riga city 22(26)district heating system1. Implementation of project can ensure reduction of chemically treated water for16.502 t/annum due to reduced evaporation in cooling towers.2. Absorption heat pump project 10th year NPV= 1.465 mil Ls with existing pricesfor energy resources. Due to that starting from July 1 st 2011 for natural gas excisetax is applied, project rentability will be accelerated even more. The estimatedrepayment period is 3.3 year.3. The total planned cooling capacity is 2.24 MW, corresponding heating capacity5.2 MW.4. Total reduction of natural gas consumption for production of heat by recoveredheat planned on a level of 1.159 mil m³/annum.5. Project anticipates using only part of low grade heat source. 2.24 recovered MWis only a small part of total 18 MW auxiliary cooling system capacities.6. As a problematic is possibility to have enough steam supply from non-combinecycle steam generation facilities close to heat pump installation.7. The steam extraction from steam turbine reduces electrical efficiency of CHP.8. The heat pump operation in non-heating season and during flooding periods iseconomically not liable.9. The commissioning of 2 nd new CHP block will reduce potential running hours ofheat pump due to full utilization of needed heat supply by cogeneration.More detailed business plan shall be worked out to evaluate the reasonability ofinstallation of single, double or even triple unit with the aim to rise efficiency of plantand reduction of production costs.All chapter material is based on information and initial visual materialspresented in source No 10.Due to that CHP-1 and CHP-2 are able to work in connected RIGA right bankdistrict heating network and in a case of network separation, the less cogenerationpenetration is in the network area of CHP-1, the CHP-1 is more beneficial on aeconomical means.Biological Water treatment plant Daugavgriva ProjectThe first water supply device in Riga was built in 1620. Initially all sewagewas discharged into natural reservoirs adjacent to the territory of Riga or within it.All city wastewater is collected in the treatment plant Daugavgriva. It is treated anddischarged into Riga Bay 3 km off the coast line. The Treatment plant 'Daugavgriva'was put into operation in 1991. The initial designed productivity of the plant was350,000 m3 per day.Picture No 14 The municipal wastewater treatment plant of Riga.

Recovery of waste heat by large capacity heat pumps for Riga city 23(26)district heating systemThe Daugavgriva water biological treatment station (DWBTS) locates on Riga BuļļuIsland Dzintaru str.60 near the Baltic sea. Sewage waters collected from Riga andJurmala are pumped to DWBTS. Totally it serves for 850’000 inhabitants. The watertreatment design capacity of DWBTS is 350 th m³/day; however the real requestedload is 170’000m³/day.The DWBTS potential for heat pump/chillier installation has been elaboratedby RĪGAS ŪDENS Ltd (RU) and RIGA TECHNICAL UNIVERSITY (RTU) scientists.During evaluation process the main three versions had detailed inspection. Versionsdiffer by energy production and heat pump/chillers’ installation. As a source forenergy generation savage water is planned to use.In DWBTS as a source of high potential is planned to use excess heat from localCHP; auxiliary natural gas driven or woodchip steam boiler. All examined versionsdiffer by the auxiliary steam generation. Steam generation is possible by existingboilerhouse steam boilers DE-25-14-GM and DE -10-14-GM or by potentially newbiofuel (woodchips) boilerhouse. Each version more detailed evaluated followsbelow: Version 1: Heat pump installation for plant auxiliary needs, to cover the totalheating capacity (October– April), when the existing CHP capacity do notcover all heating load and natural gas boiler is in operation to cover capacityrequirements. Two subversions possible: Version1a: The heat pump installation in existing boiler house and with theauxiliary steam production by existing natural gas steam boilers. Version 1b: the heat pump located in a new bio fuel (woodchips) firedsteam boiler house. Version is presented in the picture No 15.Picture No 15 DWBTS heat pump installation with bio fuel boilerVersion 2: During the summer period excess heat from CHP to be deliveredto Daugavgriva DH plant network by new pipeline approximately 3.2km long.The main delivery of heat to network is planned mainly in non-heatingseason.Version 3: the installation of two heat pumps with the aim to cover heatingseason load for DWBTS and partial heat supply to Daugavgriva DH network,as well as optimization of existing CHP excess heat delivery to DH network insummer period. The serial connection of heat pumps has been chosen with

Recovery of waste heat by large capacity heat pumps for Riga city 24(26)district heating systemthe aim to lift the DH supply line temperature on an equal level with theDaugavgriva DH plant temperature graph. Two subversions possible: Version 3a: – the both heat pumps located in existing boiler house and usesauxiliary steam from existin steam boilers. Version 3b: the heat pump(s) located in new biofuel boiler house.Detailed economical revue show that in the existing economical conditionsonly versions 1a and 1b have the lowest possible investment, in the result the bestpayback, as well as implementation is simple. Taking in account that evaluation isbased on unchanged price of energy resources, as well as in case 1a investment isless, the version 1a wins. However, used natural gas in version 1a is an additionalcost escalation risk factor. Version 1b has higher initial cost, but unplannedoperational cost escalation would be excluded. The repayment rate differencebetween the versions 1a and 1b are minor and version 1b is advisable as mostsustainable long term solution. In addition advised version is CO 2 neutral andattraction of potential EU funding for such projects can be available comparing with1a.Picture No 16 Temperature of refined water on DWBTS exit pipelineVersions 2; 3a and 3b are technically liable, but high investment costs makethem economically inefficient. Especially 3.2 km DH pipeline cost is too high toafford in particular economical conditions. Version 3b is the most favourable, if thepipeline cost is eliminated. As a driving force for heat pump installation in DWBTS isavailability of high volume (~9000 m³/h) of low grade heat in already cleaned water,even in heating season. In the picture 16 is presented obtained during the projectrefined water temperatures, which shows potential comparing to the earth heatbased heat pumps. Realization of project version 1b is possible as for commercialproject with the discounted repayment period in less than 8 Years, annual savingsof natural gas 841 nm³. Attraction of EU funding could give an addition benefits forthe project implementation. Before the project implementation the detailed businessplan shall be developed. Potential project realization can be in time period 2012-2015.All chapter material is based on information and initial visual materials presented insource No 9.

Recovery of waste heat by large capacity heat pumps for Riga city 25(26)district heating systemFinal conclusionsThis first installation of absorption heat pump/chiller in Imanta DH Power plant is inoperation since November 2010. Operation of installed equipment shows thatexpected discounted payback period of project investment will meet the 3 yearstarget and corresponding annual decreased gas consumption by 842 000 m3/yearis correct , as well as saving in water consumption by 27 000 m3/year is achieved.Monitoring of the process has been permanent until the beginning of November2011 and been based on JSC RIGAS SILTUMS data collecting system. Datacollected by monitoring system had been analysed by Riga Technical universityscientists as well as possible performance improvements has been identified .The results of the project has been presented in the annual Riga EnergyDays 2011 20 October 2011 organized by Riga Energy Agency(http://www.rea.riga.lv/files/Vide_un_Energija_2011_seminars_21-10-2011.pdf).Project outcomes and the best practices also been presented in RIGA TECHNICALUNIVERCITY 52 nd INTERNATIONAL SCIENTIFIC CONFERENCE held in Riga, 13-16 October 2011 and on United Congress of Latvian scientists held in Riga, 24-27October 2011. The international reference of the project (Russian version) isavailable in the magazine "Новости Теплоснабжения" (No.5, May 2011)The main EU project Recovery of the waste heat by large capacity heat pumps forRiga city district heating system conclusions are the following: Heat pumps can be a tool to improve of efficiency of existing natural gascombine cycle power plants; High value of cogeneration penetration reduces feasibility of heat pumpinstallations for CHP auxiliary cooling heat recovery; Heat pumps are efficient systems for using low-enthalpy energy, usingrelatively small amounts of high-grade energy; Large capacity heat pumps are core elements for geothermal technologysuccessful development as a district heating element;Heat pumps can be used for municipal district heating and cooling;Bio fuel boiler in combination with heat pump is liable CO2 emission freesolution;Literature1. Н.Талцис, А.Церс, С.Плискачев, Э.Дзелзитис, Д.Турлайс,Опытутилизации низкопотенциального тепла с изпользованиемабсорбционного теплового насоса,Новости теплоснабжения№5 (129) май, 2011 г.2. Turlais D., Zhigurs A., Cers A., Pliskachev S. “Implementation of the absorptionchiller’s installation project at cogeneration plant of DHP Imanta” („News ofDistrict Heating” journal № 10, 2009, Moscow);3. Zhigurs А., Cers A., Pliskachev S. “The experience of the JSC RIGAS SILTUMSin KVGM-50 und KVGM-100 water boilers reconstruction” („News of DistrictHeating” journal № 8, 2009, Moscow);4. Zhigurs A., Turlais D., Sorochins A., Cers A. “The relationship between theperformance and type of regulation method of the heat load in the district heatingin Riga („News of District Heating” journal № 7, 2009, Moscow);5. Zhigurs А., Cers A., Golunovs J., Turlais D., Pliskachev S. Flue gas heatrecovery at the heat sources in Riga city („News of District Heating” journal № 5,2010, Moscow);6. Keil C., Plura S., Radspieler M., Schweigler C. Customized Absorption HeatPumps for Utilization of Low-Grade Heat Resources;

Recovery of waste heat by large capacity heat pumps for Riga city 26(26)district heating system7. Costa A., Neuhann V., Vaillancourt J., J.Paris Applications of Absorption HeatPumps In The Pulp And Paper IndustryFor Incrased Efficiency And Reduction ofGreenhouse Gas Effect, PAPTAC 90th Annual Meeting, 2004;8. Roos C.J. An Overview of Industrial Waste Heat Recovery Technologies forModerate Temperatures Less Than 1000oF, 09.2009;9. Pēteris Stanka, bakalaura darbs “Bioloģiskās attīrīšanas stacijas „Daugavgrīva“energoefektivitātes uzlabošana izmantojot absorbcijas siltumsūkni. RĪGASTEHNISKĀ UNIVERSITĀTE Transporta un mašīnzinību fakultāte,Siltumenerģētisko sistēmu katedra, 2011.10. Dmitrijs Gorlovičs, Maģistra darbs “SILTUMSŪKŅA UZSTĀDĪŠANA RĪGAS TEC-2 JAUNAJĀ BLOKĀ”. RĪGAS TEHNISKĀ UNIVERSITĀTE Transporta unmašīnzinību fakultāte Siltumenerģētisko sistēmu katedra11. Dmitrijs BUČŅEVS, bakalaura darbs “Rīgas TEC-1 dzesēšanas ūdens siltumautilizācijas ar siltumsūkni”. RĪGAS TEHNISKĀ UNIVERSITĀTE Transporta unmašīnzinību fakultāte, Siltumenerģētisko sistēmu katedra, 2011.12. O. Linkevičs, I. Kaminskis, A. Zviedris, “Absorbcijas siltuma sūknis Rīgas TEC-1efektivitātes paaugstināšanai”, Enerģija un pasaule, 2011.