016results_from_measurements_on_the_pvvent_systems_at_sundevedsgade_tondergade.pdf

Results from measurements onthe PV-VENT systems atSundevedsgade/TndergadeSolar Energy Centre DenmarkDanish Technological InstituteSEC-R-15DraftSolar Energy Centre DenmarkDanish Technological Institute SEC-R-15Results from measurements onthe PV-VENT systems atSundevedsgade/TndergadeSren stergaard JensenSolar Energy Centre DenmarkDanish Technological InstituteApril 2001PrefaceThe present report concludes together with(Jensen,2001)Solar Energy Centre Denmarks(Danish Technological Institute)measuring work in the PV-VENT project.The measuringproject was partly financed by EU via the JOULE project“PV-VENT Low cost energy effi-cient PV-ventilation in retrofit housing”,contract no.JOR3-CT97-0160 and partly by theDanish Ministry of Environment and Energy via the project“PV-VENT”,journal no.51181/97-0021.The project group behind the project was:Cenergia Energy Consultants,DKFortum Energy(former NESTE-NAPS),SFAirVex Danmark(former Temovex Denmark),DKFSB,DKDanish Technological Institute,DKEcofys,NLPA-Energy,DKNTNU,NCopenhagen Energy,DKThe following persons have participated in the measuring project:Sren stergaard Jensen.M.Sc.,Solar Energy Centre DenmarkWilliam Otto,laboratory technician,Solar Energy Centre DenmarkOle Larsen,laboratory technician,Solar Energy Centre DenmarkLars Molnit,student(B.Sc.),Solar Energy Centre DenmarkBertel Jensen,B.Sc.,Solar Energy Centre DenmarkUlrik Mehr,M.Sc.,Solar Energy Centre DenmarkHans Olsen.B.Sc.,Ventilation and Environment,Technological Institute of DenmarkJens Heidelbach Andersen,B.Sc.,Cenergia Energy ConsultantsLisbet Michaelsen,B.Sc.,Cenergia Energy ConsultantsResults from measurements on the PV-Vent systems at Sundevedsgade/Tndergade1st printing,1st edition Danish Technological InstituteEnergy divisionISBN:87-7756-614-9ISSN:1600-37802List of content1.Introduction.31.1.The PV-VENT systems.61.1.1.Control of the systems.131.1.2.PV-mixer.152.Measuring system.172.1.Air temperature measurements in the solar wall.172.2.Weather measurements.192.3.Temperature and flow measurements in the ventilation system.192.4.Electrical measurements.202.5.Data collection.232.6.Treatment of measured data.243.Measurements.253.1.Measurements from week 5 and 6,2001.253.1.1.Thermal part of the system.253.1.2.PV-part of the system.273.2.Measurements from specific weeks.383.2.1.Air flows.383.2.2.PV-mixer .383.3.Calculations based on the measurements and more general conclusions.403.3.1.The efficiency of the air to air heat exchanger.403.3.2.Fan power.513.3.3.Temperatures in the solar wall.523.3.4.The PV-mixer.573.4.Obtained and obtainable savings of the system.603.4.1.Obtained savings.603.4.2.Obtainable savings.644.Conclusions.704.1.Aims of the PV-VENT project.704.2.Results from the PV-VENT project.704.2.1.Architectural results.704.2.2.Pre-heating of fresh air cooling of PV-panels.714.2.3.Air to air heat exchanger.724.2.4.Low fan power.724.2.5.Direct coupling of PV-panels and fans.724.2.6.Total systems.734.2.7.General conclusions.735.References.74Appendix A Data sheets for the heat exchangers and fans.75Appendix BData sheets for the PV-panels.7831.IntroductionThe objective of the project was to research,develop and test low cost,high efficiency PV-powered ventilation systems for retrofitting of apartment blocks.Systems where the fans arepowered directly by the PV-panels and where the waste heat from the PV-panels is utilized topre-heat fresh air to the apartments.The present report describes the obtained experience from measurements on the PV-VENTsystems installed in an apartment building in the area Vesterbro of Copenhagen,Denmark.The building is situated Sundevedsgade 14/Tndergade 1.The building is part of the Hede-bygade block a site plan of this block is shown in figure 1.1.The Hedebygade block hasduring the late 90ies been exposed to a major renovation project including extensive utilisa-tion of solar energy.Sundevedsgade 14/Tndergade 1Figure 1.1.The site plan for the Hedebygade block and the location of Sundevedsgade14/Tndergade 1.The five-storied building was erected in 1884 and is typical for that period.The buildingcontains 20 apartments and has a net floor area of 1137 m.Figure 1.2 shows the facades ofthe building facing the streets after the renovation.The original appearance of the facade hasnot been changed.4Figure 1.2.The facades of the building after the renovation.The dwellings had before the renovation no bathrooms or central heating,and the piping sys-tem for domestic water and the sewer system were of a poor quality.The flats were poorlyinsulated and the heating system was old-fashioned e.g.wood-burning stoves,electricheating panels or gas heating furnaces.The windows where not tight and there was no venti-lation system in the building.A renovation of the building was thus badly needed.The renovation contained the following items:-total renovation of the interior including new kitchens and bathrooms,-new piping and pluming,-low-energy windows,-insulation especially against the attic and roof,-new heating system with radiators,-sun spaces in 8 of the dwellings,-balanced ventilation system including the PV-VENT systems with solar walls,-solar air heating system for pre-heating domestic hot water and space heatingFigure 1.3 shows the facades of the building facing the courtyard after the renovation.Theappearance of these facades is changed considerably compared to the facades facing thestreets.The photo shows the solar walls with PV-panels and the sun spaces.5Figure 1.3.The facades facing the courtyard after renovation.A more detailed description of the ideas behind the renovation may be found in(Lien andHestness,1999 and Cenergia,1999).Here will only the PV-VENT systems briefly be de-scribed.61.1.The PV-VENT systemsFigure 1.4 gives a schematically overview of the ventilation system in the building.Type 1Type 1Type 1Type 1Type 1Type 1Type 1Type 1Type 1Type 1Type 1Type 1Type 2Type 2Type 2Type 2Type 2Type 2Type 2Type 2Figure 1.4.Principle of the ventilation system in the building.The ventilation system consists basically of two types of ventilation systems:Type 1:Individual PV-VENT systems with a heat exchanger JoVex 175 and fans type 175(56 V dc)(developed by AirVex as part of the project(Jensen and Pedersen,1999)and appendix A)in each apartment are installed in 12 dwellings:the 8 lowest dwell-ings in Sundevedsgade 14 and the 4 lowest apartment to the right in Tndergade 1.The heat exchangers are located on the outside of the exterior wall behind the glazingof the solar walls the spacing between the exterior walls and the cover of the solarwalls is 40 cm.The area of the solar wall per dwelling is 3 1 m in Tndergade 1and 3 1.25 m in Sundevedsgade 14(height width).In Sundevedsgade 14 two heatexchangers are located site by site at each floor(see figure 1.8),while in Tndergade1 only one heat exchanger is located at each floor(see figure 1.9).The fresh air to theheat exchangers is taken from the solar wall.The fresh air is thus pre-heated by thesolar wall/excess heat from the PV-panels and by the heat loss through the walls ofthe building.The fresh air to the solar wall is drawn in through a grill at the bottomof the solar wall as shown in figure 1.4-5.The cover of the solar wall consist partlyof the PV-panels and partly of opal glazing(as seen in figure 1.3)in order to hide theheat exchangers behind the glazing and still let solar radiation into the solar walls.During warm days the solar walls may be vented by opening dampers in the solarwalls.heat exchangersolar wall7Figure 1.5.The inlet to one of the solar walls.Figures 1.6-7 show drawings of the solar walls and the sun spaces,while figures 1.8-9 show the location of the heat exchangers in the solar walls.Figure 1.10 shows aphoto of one of the heat exchangers in the solar wall and an entrance door to one ofthe solar walls.Figure 1.11 shows the floor plans before and after the renovation.The total ventilation system of Tndergade 1 to the right is shown in figure 2.5.The ventilation system consists of efficient counter flow heat exchangers and DCfans with a very low electricity demand developed within the project by AirVex(Jensen and Pedersen,1999)(see also appendix A).The PV-array for each dwelling consists of three PV-panels of two different sizes(A1 and A2)in the front of the solar walls as shown in figures 1.3,1.12 and Appen-dix B and two other sizes(B1 and B2)in the gable of the solar wall on Sundeveds-gade 14 as seen in figure 1.13(Leppnen,2000).The dimensions of the panels areA1:490 x 723 mm,A2:490 x 1122 mm,B1:907 x 723 mm and B2:907 x 1122mm(see appendix B).The total peak power per three panels(ie per PV-mixer seelater)is either 121 or 242 Wp.The polycrystalline(c-Si)cells of the PV-panels arelocated with an spacing of 3-4 mm with a translucent lamination film in-between thecells allowing solar radiation to penetrate into the solar wall.The PV-panels weredeveloped by Fortum Energy as part of the project(Leppnen,1999).The electricityproduced by the PV-panels is directly used to power the fans.However,the PV-panels are not able to power the fans all 24 hours of the day,so a so-called PV-mixeris installed to mix PV-power with grid power in order to maintain the necessarypower level for the fans.The PV-mixer is further described in section 1.1.2.Three of the top floor apartments are not as shown in figure 1.4 connected to the so-lar air collector at the roof but obtain the fresh air from the solar walls.Apart fromthis the ventilation systems are type 2 as described below.The three apartments are:the two top floor dwellings in Sundevedsgade 14 and the top floor to the right inTndergade 1.8Figure 1.6.Drawing of the solar wall and sun spaces at Sundevedsgade 14.Figure 1.7.Drawing of the solar wall and sun spaces at Tndergade 1.9Figure 1.8.Location of the heat exchangers in the solar wall at Sundevedsgade 14.The solar wall of Sundevedsgade 14 has mainly a westerly orientation(20 from west towardssouth),while the solar wall of Tndergade 1 has an orientation of 20 from south towardseast.heat exchangerPV panel10Figure 1.9.Location of the heat exchangers in the solar wall at Tndergade 1.heat exchangerPV panelOrbesen damperfor overheatingprotectionOrbesen damperfor overheatingprotection11Figure 1.10.Photo of one of the heat exchangers in the solar walls and an entrance door to asolar wall.Figure 1.11.Typical floor plan before(to the left)and after(to the right)the renovation.glazing of thesolar wallheatexchangerentrance doorto the solarwall12Figure 1.12.Close up of the PV-panels for one dwelling.Type 2:The ventilation systems of the remaining 8 dwellings have also individual heat ex-changers JoVex H300 and fans type 175(56 V dc)from AirVex(Jensen and Peder-sen,1999)see also appendix A.These system is not part of the PV-VENT project.The efficiency of the heat exchanger in the type 2 systems has been evaluated in theproject at Lundebjerg(Jensen,2001).The heat exchangers are situated inside thedwellings except for the top floor apartments where the heat exchangers are locatedin the attic.These three dwellings are as earlier mentioned connected to the solarwalls.Solar air collector:A solar air collector of 19 m is located on the roof of Tndergade 1 asseen in figure 1.13.The solar air collector covers via an air to water heat exchangerpart of the domestic hot water and space heating of the building.This system is nor part of the PV-VENT project.Damper for over-heating protection13solar air collectorgridconnectedPV-panelsFigure 1.13.The grid connected PV-panels on the south gable of the solar wall on Sunde-vedsgade 14 and the solar air collector array on the roof of Tndergade 1.1.1.1.Control of the systemsThe occupants of the apartments are able to control their ventilation systems via a controlpanel located in the dwelling figure 1.14 shows a photo of the control panel.According tothe Danish building code the flow rate of exhaust air from a dwelling should be 126 m/h.Thetenants may,however,choose between normal,max and min flow rate and between winterand summer mode as shown in table 1.1.Table 1.1 shows the intended/pre-set air flow ratesin the apartments.The flow rate of exhaust air should always be higher than the flow rate offresh air in order to create a small under pressure in the apartments,which will prevent humidair in being forced into the constructions.It is as shown in table 1.1 possible to run the venti-lation systems as purely exhaust ventilation(summer mode)in order to prevent pre-heated airfrom the solar wall to enter the dwellings diring periods with no heat demand.The max power consumption of the two fans per dwelling is 45 W each.14Figure 1.14.The control panel from which the occupants of the dwellings may control theirventilation systems.ModeWinterSummerExhaustm/hFresh airm/hExhaustm/hFresh airm/hMax1981161980Normal1261161260Min45-85*40-77*45-85*0Table 1.1.Ventilation modes,which can be chosen via the control panel in the apartments.*the minimum ventilation is not identical for the apartments.The systems can during warm periods be run in summer mode which means that no air will bedrawn from the solar walls to the dwellings.The air gap behind the PV-panels may,therefore,overheat which will reduce the electricity production of the PV-panels.So in order to cool thePV-panels during these periods Orbesen dampers driven by wax motors are installed in thetop of each of the two solar walls.One damper is further installed at each floor as seen in fig-ure 1.3,1.9 and 1.12.The dampers start to open at a temperature of 23C and is fully open ata temperature of 27C the dampers starts to close again at a temperature of 24C and areclosed a 21C.When the dampers start to open the PV-panels will be cooled by a buoyancydriven air stream in the air gab.151.1.2.PV-mixerThe dc fans of the ventilation systems are directly connected to the PV-panels.However,thePV-panels are not during the night and during overcast conditions able to run the fans at therequired speed.A so-called PV-mixer has,therefore,been developed as part of the project.The function of the PV-mixer is to ensure that as much electricity from the PV-panels as pos-sible is used for running the fans.If the PV-power is too low to run the fans the PV-mixer topup with electricity from the grid via a transformer.The development of the PV-mixer was unfortunately delayed.The first company chosen forthe development came up with a solution as late as in January 2000.The Danish Technologi-cal Institute obtained one sample for evaluation(Mehr,2000).It was judged that the principlechosen for controlling the power from the PV-panels and the grid didnt give enough credit tothe PV-panels leading to too high power consumption from the grid even if enough powercould be delivered by the PV-panels.The PV-mixers was further of a very poor quality.Thesoldering of the components looked to be made by a plumber rather than by a electrotechni-cian.The PV-mixer was,therefore,rejected and a new firm for developing the PV-mixer wa