Eligibility of a Heat Pump Based on the Primary Energy Factor

Transcription

1 Eligibility of a Heat Pump Based on the Primary Energy Factor Primož Poredoš* a, Boris Vidrih a, Tjaša Duh a, Andrej Kitanovski a, Alojz Poredoš a a Laboratory for Refrigeration and District Energy, University of Ljubljana, Faculty of Mechanical Engineering, Aškerčeva 6, 1000 Ljubljana, Slovenia * primoz.poredos@fs.uni-lj.si

2 Introduction Heat pumps (HPs) competitive technology: Not only in terms of thermo-economics (TE), Also exergetically efficient with (relatively) small primary energy factor (PEF) Both performances depend on different factors Energy market and its prices Seasonal performance factor (SPF) of the HP; heat source and sink variable conditions, ambient conditions, building characteristics, user behaviour, HP manufacturers list measured COP according to EU standard EN Different opinions regarding the eligibility of their applications exist Limiting cases also exist at which HPs are not PEF efficient Aim of the study: to identify the limiting parameters by a comparative analysis of 10 heating systems

3 Seasonal performance factor of heat pumps SPF determination: one-year simulation Three types of HPs: A-W, W-W, G-W One-family residential house Energy used for heating and sanitary hot water (SHW) Considered location: Ljubljana, Slovenia -> TRY Ljubljana Net heating area: 180 m 2 Layout of the residential house: 8 12 m Nominal heating power for all HPs: 8 kw SPF = Q &' W )* (Eq. 1) Q &' - annual produced heat W )* - annual used electric energy of the HP system

4 Seasonal performance factor of heat pumps Temperature [ C] Temperature [ C] Hour [h] -20 Hour [h] Air temperature Water temperature Ground temperature Inlet radiator temperature External air temperature

5 Seasonal performance factor of heat pumps Energy label of the residential house Design temperature regime [ C] Annual energy consumption [kwh/m 2 a] Heating system Sanitary hot water heating 4.5 A B C D E 35/30 35/30 45/35 55/45 65/ Floor heating Floor heating Floor and radiator heating Radiator heating Radiator heating YES YES YES YES YES SPF [/] /55 C - E 55/45 C - D 45/35 C - C 35/30 C - B 35/30 C - A A-W HP W-W HP G-W HP

6 Analysis of the primary energy factor PEF analysis: well-established method to determine the quantity of the primary energy (PE) used for heat production Based on calculation of all PE inputs for extraction, conversion, transport and usage of energy source for electricity and heat production PEF calculation was performed for following heating systems based on: Air-to-water HP Water-to-water HP Ground-to-water HP Oil boiler Naturalgas boiler Wood chips boiler Pellets boiler Wood logs boiler LPG propane boiler District heating using coal fired cogeneration unit

7 PEFs of air, water and ground source HP PEF &' = PEF )* SPF PEF )* - primary energy factor of the electricity (Eq. 2) SPF - seasonal performance factor of a HP PEF el from various sources were considered: EU electricity mix: PEF = 2.49 Nuclear power: PEF = 3.50 Photovoltaics: PEF = 1.14 Hydroelectricity: PEF = 1.08 Wind power: PEF = 1.03 Energy PEF SPF label of the EU mix Renewables average residential house A-W W-W G-W A-W W-W G-W A-W W-W G-W E D C B A

8 PEFs of oil, NG, biomass and LPG propane HS PEF &' = PEF &3 η &3 (Eq. 3) PEF &3 - primary energy factor of heat source η &3 - the efficiency of the heating system Heating system PEF of heat Heating system PEF for heat source [/] efficiency [%] production [/] Oil CB Natural gas CB Firewood Biomass Pellets Wood chips LPG propane CB Note: CB: condensing boiler

9 PEFs of oil, NG, biomass and LPG propane HS compared to PEFS of HPs 4.00 SPF range A-W HP SPF range W-W HP SPF range G-W HP PEF [/] EU mix Nuclear Firewood Pellets Wood chips Natural gas Oil LPG SPF [/] Photovoltaics Hydro Wind Nuclear EU mix Oil Nat. gas LPG Firewood Pellets Wood chips

10 PEFs of DH using coal fired cogeneration unit PEF 36,8&' = PEF 89:* 1 x η => η 89:*,8&' η )*,8&' (Eq. 4) η => - energy efficiency of a DH network system PEF 89:* - primary energy factor of coal x = η )*,8&' η )* (Eq. 5) η 89:*,8&' - the energy efficiency of a CHP unit according to the coal η )*,8&' - energy efficiency of electricity generation of a steam turbine in a cogeneration system η )* - energy efficiency of the electricity generation when operation is related only to the production of electricity PEF coal 1.3 η coal,chp 0.88 η dn at 90/70 C 0.9 η dn at 70/50 C η dn at 50/30 C 0.957

11 PEFs of DH using coal fired cogeneration unit compared to PEFs of HPs PEFs of a steam turbine in a coal fired cogeneration unit at 20% of extracted steam 0.70 PEF range A-W HP PEF range W-W HP PEF [/] /70 C 70/50 C 50/30 C ηel PEF range G-W HP Note: HPs using electricity from renewable sources

12 PEFs of DH using coal fired cogeneration unit compared to PEFs of HPs PEFs of a steam turbine in a coal fired cogeneration unit at 50% of extracted steam 0.70 PEF range A-W HP PEF range W-W HP PEF [/] /70 C 70/50 C 50/30 C ηel PEF range G-W HP Note: HPs using electricity from renewable sources

13 PEFs of DH using coal fired cogeneration unit compared to PEFs of HPs PEFs of a steam turbine in a coal fired cogeneration unit at 100% of extracted steam 0.70 PEF range A-W HP PEF range W-W HP PEF [/] /70 C 70/50 C 50/30 C ηel PEF range G-W HP Note: HPs using electricity from renewable sources

14 Conclusions Method for determination of eligibility of a HP based on the PEF analysis was developed Comparison between HPs PEF with heating systems based on oil, natural gas, biomass, LPG propane and coal fired cogeneration unit based DH When considering residential house (energy label A-E) and electricity from the EU mix, HPs are more PE efficient compared to 6 individual HS excluding DH When considering electricity from the nuclear power plant, only ground source HP is fully eligible compared to 6 individual HS excluding DH HPs are more PE efficient compared to DH if the temperatures of the DH network system are high (90 C and above) Heat should not be generated by heating plants, using coal, gas, biomass, etc. The heat production must be achieved by the cogeneration units in combination with the newer generation of the district heating network systems Heat pumps are suitable source of heat when combined with the district heating systems of 4. generation and in case of using the electricity from renewable sources

15 Thank you!

16 Appendix Other important factors used in the SPF simulation were the following: Air-to-water (A-W) HP: frost formation on the evaporator coils was not considered in the simulation Water-to-water (W-W) HP: depth of the well was considered to be 18 m. The pumping of water was provided by the pump with the nominal power of 800 W. Ground-to-water (G-W) HP: depth of the collector field was considered to be 1.5 m. The pumping of water was provided by the pump with the nominal power of 75 W. Design temperature regimes were chosen according to the energy label of the residential house and the project temperature, which for Ljubljana is -13 C. The inlet temperature of the radiator or floor heating system was variating with the external air temperature.

17 Appendix Q B> = P )* η )* = P )*,8&' η )*,8&' (Eq. 6) P )* = m 36 h F h G (Eq. 7) P )*,8&' = m 36 h F h I + m 36 m 36,=> h I h G (Eq. 8) m 36 = m 36,=> + m 36,)* (Eq. 9) y = m 36,=> m 36 (Eq. 10) η i = 0.7 h 1 (540 C, 180 bar) [kj/kg] x = η )*,8&' η )* = P )*,8&' P )* = h F h I + 1 y h I h G h F h G (Eq. 11) h 2s (0.05 bar) [kj/kg] 1850 h 2 (0.05 bar, η i ) [kj/kg] h 3a (90 C) [kj/kg] 2400 h 3b (70 C) [kj/kg] 2300 h 3c (50 C) [kj/kg] 2220