The Analytical Design Method Of Building Cooling Heating And Power System With Thermal Energy Storage And Study On The Ideal Thermal Storage Material Property

Building Cooling, Heating and Power (BCHP) system, driven by Gas turbine, isencouraged by the government in recent years due to its high energy efficiency, lowcarbon emission and power grid security enhancement, etc. However, systems built inChina have been operated with poor energy-saving performance. The main reason isthat the gas turbines and absorption heat pumps have been working in partial-loadconditions in terms of the variant building thermal load or electricity load, andthesupply and the demand do not match. According to the current research work, it is aneffective way to incorporate Thermal Energy Storage (TES) into BCHP systems tobalance the energy demand and supply. That brings to a series of questions, such as howto design the BCHP systems under TES mode? What is the optimal capacity of thecomponents? Where is the TES equipment placed? What storage material thermalproperty is suitable? Those questions are important, but remain unclear in the researchfield. The capacity design principle of system componets and the analytical designmethod for TES driven by the flue gas are studied in this thesis.Firstly, an analytical design method for BCHP system under TES mode todetermine the optimal gas turbine capacity is put forward with the objective ofachieving the maximum relative energy saving ratioto meet the user load. The optimaldesign principle is either Following Thermal Load (FTL) or Following Electricity Load(FEL). When the gas turbine thermal efficiency is lower than the grid efficiency, theoptimal design principle is FTL.Next, the sensible and latent TES design are analyzed under the constraint oflimited storage period, based on the assumption of a particle model with the infiniteNumber of Transfer Unit (NTU) and infinite coefficient of thermal conductivity. Thekey dimensionless design factors for TES are obtained: the total storage materialthermal capacity, the starting working temperature and the charging/discharging flowratio for sensible TES, while phase-change temperature and the charging/dischargingflow ratio for latent TES. Latent TES shows higher performance compared withsensible TES. And then, with the consideration of limited NTU and limited coefficient of thermalconductivity, latent TES is studied. An analytical method to obtain the optimalphasechange temperature of TES is obtained, with the two constraints of limited storageperiod and variable COP of absorption heat pumps in accordance to the outletdischarging temperature. The results show that the optimal phasechange temperaturedrifts to the higher range by considering the two constraints.In the end, the inverse analytical method is applied to get the optimal gas turbinecapacity and the specific thermal capacity-temperature function of energy storagematerial, with the given the geometric design of TES device and other thermalproperties of storage material. The results show that the optimal specific heat capacitywith the temperature should be a function. It verifies the latent TES with optimalphasechange temperature is the optimal method for TES driven by the flue gas in BCHPsystems from the inverse perspective.This work provides design principles for the gas turbine capacity and TES forBCHP systems with TES model, and supplies theoretical analyses for selecting anddeveloping storage materials with ideal thermal properties.