12 th IEA Heat Pump Conference May 18 th, 2017, Rotterdam, Netherland Development of Optimum Design Method for the Heat Recovery Ground Source Heat Pump System Takao KATSURA Faculty of Engineering, Graduate School of Hokkaido University
Today s Contents (1) What is the heat recovery ground source heat pump (HR-GSHP) system? 1) Outlines and advantages 2) Applications 1 (2) Design method for the HR-GSHP system by using optimization method 1) Design process of HR-GSHP system and basic concept of the design 2) Determination method of the thermal load of each GSHP unit in the HR-GSHP system by using optimization method (3) Feasibility study of installing the HR-GSHP system using the design method 1) Outlines of subject building and calculation condition 2) Determined thermal load of the HR-GSHP system 3) Temperature variation of heat carrier fluid in the HR-GSHP system 4) Installation effect of the HR-GSHP system
Introduction 2 What is the HR-GSHP system? Outlines- Heating demand Heating demand Cooling demand Supply header Return header GHEX
Introduction 3 What is the HR-GSHP system? Application- Large complex building Restaurant Hotel Hotel Hotel Hotel Hotel Office Office Office Office Office Restaurant Retail store Retail store Retail store Retail store Example of hourly thermal load in annual
Introduction 4 What is the HR-GSHP system? Application- Large complex building
Introduction 5 What is the HR-GSHP system? Application- Food productive process Cold storage Casting Seasoning Drying Vaporing Cooling Packing Heating Sterilization Cooling Shipment Cold water Vapor Cold water Tap water GSHP GSHP Boiler Pre-heated water GSHP GHEX
Introduction 6 What is the HR-GSHP system? Application- Thermal grid system
7 Design method for the HR-GSHP system by using optimization method
Design process of HR-GSHP system and basic concept of the design 8 Concept diagram of HR-GSHP system Basic design concept 1. The GSHP units are operated by priority 2. The GSHP s total heat load are maximized by using the two heat recovery effects
Determination method of the thermal load of each GSHP unit 9 Flow of design method Example of Q ghr, i and Q gcr, j
Determination method of the thermal load of each GSHP unit 10 Flow of design method Example of hourly thermal load (top) and heat extraction (bottom)
Determination method of the thermal load of each GSHP unit 11 Flow of design method Simplifying hourly heat extraction
Determination method of the thermal load of each GSHP unit Optimizing the thermal load of each GSHP unit 12 ) *+, Objective function: J " = )-. Q &'( + )-. Q &'0 Maximized Evaluation variables: Q 234567, Q 284567 Constrains: A. 0 < Q 234567 Q 23456 Constrains by giving the total length Q 23456 = q = 23 L The genetic algorithm (GA) is 2ΔT 2448A 1000 of GHEX, heat extraction rate q applied for the optimization = 23, q B. 0 < Q 284567 Q = and allowable temperatures, 28456 method 28 because the objective Q 28456 = q = 28 L T 2ΔT 24456 1000 function 1inmax and lacked T 1inmin smoothness K *+, + and D KJG IJG Constrains was nonlinear of heat balance according between C. to heat the extraction evaluation and variables heat injection " FG*,I K.E *+, + " FGI,I KJG IJG.E D ) *+, Here, Q 23456 Q 28456 L 2 : Maximum value of GHEX s heat extraction Q pe [kw] : Maximum value of GHEX s heat injection Q pi [kw] q = 23, q= 28 : Heat extraction rate [W/m/K] (Explained later) : Total length of GHEX [m] ΔT 2448A : Maximum temperature variation for heat extraction [ o C] ΔT 24456 : Maximum temperature variation for heat injection [ o C]
Determination method of the thermal load of each GSHP unit Optimizing the thermal load of each GSHP unit Example of changing the evaluation variable and objective function 13 Q 23456 Q 234567 Q 234567 Q 28456 Q 284567 Q 284567 Q &. Q &. > Q 28456 Q &. Q 28456
Determination method of the thermal load of each GSHP unit Calculation of heat extraction rate 14 Example of hourly heat extraction Example of temperature variation of heat carrier fluid Q 23 ΔT 24456 T [ o C] ΔT 2448A Q 28 Elapsed time [h] Elapsed time [h] Heat extraction rate per length and temperature difference q [W/m/K] q = Q 2/L 2 ΔT 24
Determination method of the thermal load of each GSHP unit Calculation of heat extraction rate 15 Example of heat extraction rate per length and temperature difference
16 Feasibility study of installing the HR- GSHP system using the design method
Outlines of subject building and calculation condition Outlines of subject building and thermal load Large complex building 17 Restaurant Hotel Hotel Hotel Hotel Hotel Office Office Office Office Office Restaurant Retail store Retail store Retail store Retail store Example of hourly thermal load in annual
Outlines of subject building and calculation condition Outlines of HR-GSHP system and calculation condition 18 Heating capacity : 2,000 kw Cooling capacity : 1,200 kw Condition of soil property Initial ground temperature : 16.5 o C Heat capacity : 3,000 kj/m 3 /K Effective thermal conductivity : 1.5 W/m/K Single U-tube GHEX Depth: 100 m, 72 boreholes
Determined thermal load of the HR-GSHP system Comparison of thermal loads with the conventional GSHP system Thermal load of the HR-GSHP system Thermal load of the conventional GSHP system 19 Heating load for HR-GSHP system Heating load for HR-GSHP system Heating load for HR-GSHP system Cooling load for HR-GSHP system Cooling load for HR-GSHP system Cooling load for HR-GSHP system Cooling load for HR-GSHP system Total thermal load Heating load : 5,442 MWh Cooling load : 3,955 MWh Total thermal load Heating load : 1,303 MWh Cooling load : 883 MWh 4.3 times
Temperature variation of heat carrier fluid Comparison of temperature variations with the conventional GSHP system 20 Temperature variation of T 1in in the HR-GSHP system Temperature variation of T 1in in the conventional GSHP system
Installation effect of the HR-GSHP system Comparison of thermal loads and COPs with the conventional GSHP system 21
Summary (1) A design method applying the optimization method for the HR-GSHP system was introduced. By applying the design method, the total heating and cooling loads of each GSHP unit in the HR-GSHP system were maximized in response to an arbitrarily set GHEX total length. (2) Assuming that an HR-GSHP system is installed in a large scale complex building, the hourly heating and cooling loads of each GSHP unit were determined using the optimum design method. The results showed that the HR-GSHP could cover approximately 4.3 times of the heat load compared to a conventional GSHP system. (3) The average COPs for the HR-GSHP system were 4.6 for heating and 10.3 for cooling. Therefore, the HR-GSHP system also has the advantage of COP compared to the conventional GSHP system. 22
Thank you for your attention 23
Introduction 24 Ground source heat pump (GSHP) systems have gained attention in Japan since ground thermal energy was defined as one of the renewable energies in 2009. However in Japan there are few examples of large GSHP system with a total heating or cooling capacity of more than 500 kw. Heat recovery ground source heat pump (HR-GSHP) system have the potential to promote the installation of large GSHP system.
Introduction 25 What is the HR-GSHP system? Advantages- Direct heat recovery effect Example of hourly heat thermal extraction load rate Eliminated heat extraction (Blue) Heating load Cooling load Eliminated heat injection (Red)
Introduction 26 What is the HR-GSHP system? Advantages- Indirect heat recovery effect Hourly heat extraction rate (HR-GSHP (Conventional system) GSHP system) Temperature variation of heat carrier fluid (HR-GSHP (Conventional system) GSHP system) T [ o C] Elapsed time [h]
Design process of HR-GSHP system and basic concept of the design 27 Necessity of optimization method for design process Diagram of design process for the conventional GSHP system Diagram of design process for the HR-GSHP system However, Design tool it for is required the GSHP tosystem handle the heat loads of several types of heat pumps. The number of variable increases The optimization method is required to determine the heat loads Introduced HPC2005 Las Vegas
Installation effect of the HR-GSHP system Comparison of electric power consumption with the conventional GSHP system 28 40 %
Design process of HR-GSHP system and basic concept of the design 29 Concept diagram of HR-GSHP system We assume the followings in the modeling 1. Heat gain and heat loss in the piping between the heat pump units and GHEXs 2. The total heat load Q 2,i is covered not only by the GSHP in HR-GSHP system but also by other heat source systems
Modeling of the HR-GSHP system 30 Concept diagram of HR-GSHP system We assume the followings in the modeling 1. Heat gain and heat loss in the piping between the heat pump units and GHEXs 2. The total heat load Q 2,i is covered not only by the GSHP in HR-GSHP system but also by other heat source systems
Modeling of the HR-GSHP system 31 Concept diagram of HR-GSHP system (1) Calculation of total thermal load of GSHP units Heating load Cooling load Q &'( = O Q &'(,8 (If the heat pump unit i=1 supplies heating, the heating load of the heat pump unit i=1 is added to the heating side) Example of hourly Q g2h, Q g2c A 8-. A Q &'0 = O Q &'0,8 8-. Q [kw] Q g2h (Q g2 ) Q g2c (Negative side of Q g2 )
Modeling of the HR-GSHP system 32 Concept diagram of HR-GSHP system Here, (2)Calculation of total heat extraction rate of GSHP units Heat extraction (Heating) Heat Injection (Cooling) Q &.3,8 = Q &'(,8 Q &'(,8 /COP (,8 Q &.8,8 = Q &'0,8 Q &'0,8 /COP 0,8 A Q &.3 = O Q &.3,8 8-. A Q &.8 = O Q &.T,8 8-. Example of hourly Q g1e, Q g1i Q [kw] Q g1e (Q g1 ) Q g1i (Negative side of Q g1 )
Modeling of the HR-GSHP system Concept diagram of HR-GSHP system (3) Calculation of GHEXs heat extraction rate Q 2 = Q &. = Q &.3 Q &.3 33 Example of calculation Q p Q g1e (Eliminated, blue) Q g1 (Green) Q [kw] Q g1i (Eliminated, red) Q [kw] Q p = Q g1
Modeling of the HR-GSHP system 34 Concept diagram of HR-GSHP system (4) Calculation of temperature of heat carrier fluid The temperature variations ΔT pmmin and ΔT pmmax are calculated by applying the simplified following equation ΔT 2448A = Q 23456 1000 ( q = 23 L 2) T 24 = T 28A + T 2UV) 2 Here, ΔT 24456 = Q 28456 1000 ( q = 28 L 2) ΔT 2448A : Maximum temperature variation for heat extraction [ o C] ΔT 24456 : Maximum temperature variation for heat injection [ o C] Q 23456 Q 28456 : Total length of GHEX [m] L 2 : Maximum value of Q pe [kw] (Q pe is positive value of Q p ) : Maximum value of Q pi [kw] (Q pi is negative value of Q p ) q = 23, q= 28 : Heat extraction rate [W/m/K] (Explained later)
Modeling of the HR-GSHP system 35 Concept diagram of HR-GSHP system (4) Calculation of temperature of heat carrier fluid (continuation) The temperature T 1inmin (Minimum value of T 1in ) and T 1inmax (Maximum value of T 1in ) are calculated by the following equation T.8A48A = T [E ΔT 2448A + ΔT. /2 T.8A456 = T [E + ΔT 24456 ΔT. /2 Here, T [E ΔT. : Undisturbed ground temperature [ o C] : Temperature difference between T 1in and T 1out [ o C] (Generally 5 o C) We can predict the temperature variation
Design process of HR-GSHP system and basic concept of the design Basic design concept 36