ENERGY RECOVERY, CALCULATION METHODS

Transcription

1 ENERGY RECOVERY ENERGY RECOVERY, CALCULATION METHODS 19/10/2016 DOCUMENT PETER SUNDELIN

2 Efficiency of a recovery system? Supply air temp. efficiency, for 0C out doors Supply air dry temp. efficiency (0 C) Supply air temp. efficiency according to EN308 Supply air dry temp. eff. equal air flows (Winter dim.) Supply air wet temp. eff. (Winter dim.) Supply air dry temp. eff. (Winter dim.) Supply air temp. efficiency, due to frost protection -27 C -22 C -17 C etz Exhaust air temp. efficiency Entalpy efficiency Humidity efficiency Sensible, latent efficiency Supply air efficiency, summer Annual temp. efficiency Annual energy efficiency Etc efficiencies are too much!! 2

3 What performance of a recovery system is important? Example of a print out: 1) 2) 3) 4) 5) 6) 7) 8) 9) 10) 11) 12) 13) 14) 15) 16) 17) 17 st different efficiencies of the recovery system (RAR in this case) 3

4 Temperature efficiency for dim. Winter, no freezing protection -13 C 100% (1 g/kg) To low exhaust air temp. -20 C (0,5 g/kg) 22 C,30% (5 g/kg) 1 m³/s 16 C 1 m³/s 5 20 C kw Ƞ = 85% Ƞ = t supply t out t extract t out Ƞ = 16 (-20) 22 (-20) Is this realistic?? 4 g/kg of water dissapears? Right calculation crusial for sizing the heating coil. From energy usage point of view, not important, Stockholm -16 C, 0 h per år (MeteoNorm) 4

5 Temperature efficiency for dim. Winter, with frost protection activated -6 C 22 C,30% (5 g/kg) 1 m³/s -20 C (0,5 g/kg) 8 C 1 m³/s Ƞ = t supply t out t extract t out C kw Ƞ = 8 (-20) 22 (-20) Ƞ = 67% not 85% To deliver desired air flow, continiously To deliver desired supply air temp, continiously Calulations/dimensioning for a real conditions, frost protection active if needed. All other statements/calculations are fictive 5

6 Temperature efficiency at lowest winter, frost protection activated 0 C 22 C,30% 1 m³/s +4 C 1 m³/s -20 C Ƞ = t supply t out t extract t out C kw Ƞ = 4 (-20) 22 (-20) Applies for both RAR and PHE systems Ƞ ~ 57% For all indirect recovery systems applies: If extract air is humid, condensation occurs in the recovery system and exhaust air can not be below < 0 C

7 The new high efficient HRS requires an advanced frost protection When we get frost in the heat recovery we get problems!

8 The new high efficient HRS requires an advanced frost protection (cold climates < -10 C) The wheel: no frost protection? The plate heat exchanger: Out door air reg. norm. ~ -7 C GT -7C or Cold corner GT The run around coil system: Liquid temp. 0.5 C GT +5C Traditional frost protection methods are not good enough anymore: Today most HRS are very efficient and the focus on energy savings are of high importance. 8

9 Advanced frost protection AFP 1) Dry conditions 22 C, 10% 2) Humid conditions 22 C, 40% The advanced frost protection activates, depending on the need. Extract air Temperature Humidity Exhaust air Temperature (several) Out door air Temperature 1) -7 C 2) 0 C, 100%

10 For what situation shall I optimize the recovery system? Stockholm Out door air <-10 C = 100 h/a (1,5%) Out door air C = 3400 h/a (50%) Out door air C = 6900 h/a

11 Energy costs? Energy = Power (kwh) x time (h) Winter Heating power: 17 kw (4 times) Tid: 5h 0 C out doors, normal cond. 5 kw 303 h (60 times) Energy/cost: 85 kwh = 17 /a 0 C -16 C Ƞ = 55% 1515 kwh = 303 /a 22 C,30% 1 m³/s +6 C C 1 m³/s kw 22 C,30% 1 m³/s 16 C 5 20 C 1 m³/s kw 0 C Ƞ = 73%

12 What is the optimum heat recovery system? 4,5,6,7,8 C 19 C 0 C Ƞ = t till t ute t från t ute 22 C,30% 18 C 17 C 16 C 15 C ƞ ~ 86 % ƞ ~ 82 % ƞ ~ 77 % ƞ ~ 73 % ƞ ~ 68 % 20 C 19 C 18 C 17 C 16 C /a *) /a +200 /a +100 /a The desired supply air temperature has a huge impact on the choice of the HRS 12 *) Additional cost for 1 m³/s, 8760 h/a, 0,2 /kwh

13 Standard, performance out puts from selection programme Temp. eff. EN308: 67,2% SFPv: 2,11 Annual energy efficiency: Office,Stockholm Ƞ = 89,1 % Customer: For comparance, Yes but is it enough?? Energy consumption? Running costs? Calculation of annual energy efficiency = 100 x Q energy recovery Q total heating energy 13

14 The energy calculation module in Acon / Fläkt Woods Climate data for the whole world (MeteoNorm) Possibility to modify climate data Several user levels, depending on inputs Air temperatures Air flows Energy costs for: Heating, cooling, electricity and reheater CO2 emissions Cost for installed power Energy cost for other equipment (damper/pumps etc.) Water consumption for humidifier LCC (Life cycle costs) Constant/variable pressure Energy calculation CAV Average air flow VAV Night Pressure loss in duct work Curve for supply air temp. Cooling to either temp. or humidity Exhaust air winter/summer, both temp and humidity. Supply air for run. night. Operating time, tender sum, rent etc. Comparison Comparison between FWG solutions Comparison between FWG and external solutions The most complete energy calculation module available on the HVAC market14

15 The energy calculation module in Acon / Fläkt Woods High lights: Climate data for the whole world (MeteoNorm) Possibility to modify climate data Several user levels, depending on inputs Air temperatures Curve for supply air temperature Cooling to either temp. or humidity Exhaust air winter/summer, both temp and humidity. Supply air for run. night. Air flows CAV Average air flow VAV Night Pressure loss in duct work Energy calculation Energy costs for: heating,cooling,electricity and reheater CO2 emissions Cost for installed power Energy cost for other equipment (damper/pumps etc.) Water consumption for humidifier LCC (Life cycle costs) Constant/variable pressure Operating time, tender sum, rent etz Comparison Comparison between FWG solutions Comparison between FWG and external solutions The most complete energy calculation module available on the HVAC market15

16 Running costs: Additional value for the customer Annual energy efficiency, ECONET, RAR According to Swedish Ventilation: 89,1% (EN308: 67,2%) Customer value: Heating energy: Heating costs: 37,5 MWh 3760 /a Fan energy : Electricity costs: 67,9 MWh /a Cooling energy: Cooling costs: 29,8 MWh 1480 /a Other equiment: Costs: 4,0 MWh 600 /a (El: 0,15 /kwh, Heating 0,1 /kwh, Cooling 0,05 /kwh) Total running costs: /a 16

17 Real or project based inputs has a huge impact on the result Energy/running cost calculation by using ACon Climate data, Stockholm, Meteonorm ECONET,RAR (EN308: 67,2%) Case 1: (SWE Vent) Case 2 Case 3 Supply air temperature 18 C 18 C/15 C Exhaust air temperature 22 C 22 C/24 C Add hum/extract air +1 g/kg +1 g/kg Running hours 5 d 06:00-18:00 day 14 h (100% flow) night 6 h (50% flow) 16 C 22 C/24 C +1 g/kg day 10 h (60% flow) Air flow Heating limit Energy costs VAV (60%) No restriction 0,15/0,1/0,05 CAV Out door air < +15C 0,15/0,1/0,05 CAV (2 flow) No restriction 0,2/0,15/0,065 (electr., heating, cooling) 17 /kwh

18 Indata / result case 2 18

19 Real or project based inputs has a huge impact on the result Energy/running cost calculation by using ACon Climate data, Stockholm, Meteonorm ECONET,RAR (EN308: 67,2%) Case 1 Case 2 Case 3 Supply air temperature 18 C 18 C/15 C Exhaust air temperature 22 C 22 C/24 C Add hum/exhaust air +1 g/kg +1 g/kg Running hours 5 d 06:00-18:00 day 14 h (100% flow) night 6 h (50% flow) 16 C 22 C/24 C +1 g/kg day 10 h (60% flow) Air flow Heating limit Energy costs VAV (60%) No restriction 0,15/0,1/0,05 /kwh CAV Out door air < +15C 0,15/0,1/0,05 CAV (2 flows) No restriction 0,2/0,15/0,065 (electr., heating, cooling) Total running costs: Case /a Annual energy efficiency: AHU cost (investment) 89,1% Case /a 90,4% Case /a 96,6%

20 The total costs for an AHU during it s life time (LCC) Energy costs 85% Investment costs 5 10% 20

21 Always ask Flakt Woods first SFPv and temperature efficiency, yes, but.,,,,,, The real truth You get with a LCC calculation