Building cooling, heating and power (BCHP) system coupled with biomass and solar energy

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1 IAQVEC 2016, 9th International Conference Indoor Air Quality Ventilation & Energy Conservation In Buildings Building cooling, heating and power (BCHP system coupled with biomass and solar energy Xiaofeng Zhang, Hongqiang Li *, Guoqiang Zhang * College of Civil Engineering, National Center for International Research Collaboration in Building Safety and Environment, Hunan University, Changsha, Hunan , China * Corresponding lhq@hnu.edu.cn; gqzhang@188.com ABSTRACT Renewable energy based building cooling, heating and power (BCHP system is considered as a promising way of relieving the energy dilemma and environmental problem. The significant issue is the matching of energy system capacity and the building load, such as electricity, cooling load, heating load and domestic hot water. In the case of known building load, the design of the energy system becomes particularly important. The optimum configuration contributes to increase the energy efficiency and the economic benefits, minimize the environmental risks. In this paper, a building cooling, heating and power system integrated with biomass and solar energy is proposed. The energy fuels are all the renewable energy, which conforms the way of energy utilization in the future. The proposed system is mainly composed by the following parts: fluidized bed biomass gasifier, internal combustion engine, solar collector and LiBr-H2O absorption. The low temperature solar thermal energy is transformed into the internal energy of the vapour in solar collector and then converted into the biogas chemical energy in biomass gasification process, utilizing the sensible heat of biogas to preheat the air and recover the waste heat. The IC engine is driven by the biogas to generate electricity. Then, the exhaust gas is sent to the lithium bromide absorption and heat exchanger subsequently. The jacket water came from internal combustion engine is utilized to provide the heating load. Under the optimization of the proposed system, it can meet the basic energy requirements of the selected building. The studies mainly concern the energetic and environmental performances of the proposed BCHP system by taking into consideration demand sides characteristics. In addition, the primary energy and CO2 emissions reduction are considered as the evaluation indicator to assess the performance of BCHP system for its suitability in supplying electricity, cooling, heating and domestic hot water for building. The results indicate that the overall efficiency of the proposed system under different conditions is more than the 60%. The CO2 emissions reduction is significantly decreased compared with the separated system. It is obvious that the BCHP system integrated with biomass and solar energy is a better choice because of as higher efficiency, reduced emissions and economic benefits. This study presents a novel way for utilization of renewable energy in building energy system. KEYWORDS BCHP system; Renewable energy; System integration; Solar energy; Biomass gasification INTRODUCTION Recently, a series of serious problems have occurred owing to the utilization of fossil fuels, such as CO2 emission, climate change and ecological balance disruption, etc. Therefore, the renewable energy resources are drawing increased attention for their environmental advantages, especially solar energy and biomass energy. These energy resources have been widely used in the world as a result of their unique advantages, such as cleanliness, safety,

2 abundant reserves (Ellabban et al. 2014; Sahoo et al Building cooling, heating and power (BCHP system is considered as an efficient energy way to generate the energetic, environmental and economic benefits (Wang et al. 2010; Wang et al Therefore, the building cooling, heating and power (BCHP system based on solar energy and biomass energy is a promising energy supply system to meet the energy requirements for buildings such as hotel, offices, hospital and schools(jing et al. 2012; Wang et al As for the solar energy, it doesn t deplete natural resources and generate the liquid gaseous or solid waste products. At the same time, the utilization of solar energy contributes to increase the security of energy supply and regional energy independence (Bahadori and Nwaoha, The mid-and-low solar thermal utilization technology obtains the widespread attention for its good thermal performance and economic benefits. As is known, the solar energy can not only be used as heating driving resource, such as evaporation and recuperation processes, but also can be used for chemical processes, like decomposition and reforming. Calise et al. (2015 designed and simulated a novel prototype of a 6 kwe solar power plant, mainly consisting of flat-plate evacuated solar collectors and a small organic rankine cycle to evaluate the energy and economic performance of the system. Besides that, many researchers have investigated the possible of thermo-chemical utilization of solar energy. Luo and Zhang (2012 proposed a solar-assisted methane chemically recuperated gas turbine system, which converted the low temperature solar heat into vapor latent heat and then via the reforming reactions to the syngas chemical energy. Xu et al. (2015 developed a novel combined cooling heating and power system integrated with mid-and-low temperature solar energy thermochemical process and the methanol decomposition, and presented an energy and exergy analysis to investigate the performance of the system. Biomass is the plant material originated from the photosynthesis to produce carbohydrates (Basu, As a renewable and carbon-neutral resource, biomass has some other advantages such as abundant in resources, widely distribution and environment friendly. The annual potential biomass energy in the worldwide approximately reaches to J and the utilization ratio was about 38% in 2004(Parikka, Gasification is one of the most potential technology of biomass utilization, by which biomass can be transformed into biogas. The biogas can be used as a feedstock for the production of chemicals or power (McKendry, 2002; Gerssen-Gondelach et al Prando et al. (2014 investigated the CHP system based on biomass gasification to meet household energy requirement. Baratieri et al. (2009 analyzed and compared different plants using the biomass-derived syngas from the perspective of energy and environmental balances. Because of its high efficiency, low greenhouse gas (GHG emission and high reliability, combined cooling, heating and power (CCHP system has been widely used in the world(wu and Wang, 2006; Jradi and Riffat, Some researchers have studied the combined cooling, heating and power (CCHP system integrated with biomass and solar energy. Karellas and Braimakis (2015 investigated the thermodynamic and economic analysis of a trigeneration system using biomass and solar energy, which consisted of an organic rankine Cycle and a vapor compression cycle. Angrisani et al. (2013 presented a new concept solarbiomass cogeneration system using a Stirling engine for the combined production of the heat and electric power. As a biomass combustion chamber, the fluidized bed simultaneously absorbed the heat concentrated from the solar collector. Tanaka et al. (2015 investigated a hybrid power generation system coupling biomass gasification and concentrated solar collecting processes.

3 In this paper, a small-medium building cooling, heating and power (BCHP system coupled with biomass and solar energy is proposed and discussed. In the proposed system, the solar thermal energy is transformed into the chemical energy of bio-gas by gasification process. The internal combustion engine (ICE is driven by the bio-gas to generate electricity. Then, the flue gas is sent to absorption and heat exchanger subsequently to generate chilled water/hot water and domestic hot water. The energetic and environmental analysis is analyzed to study the performance of the BCHP system. METHODS 1. Description of BCHP system The schematic giagram of the proposed BCHP system is shown in Figure 1. The system consists of three main parts: air-steam biomass gasification and purification subsystem; internal combustion engine power generation subsystem and waste heat recovery subsystem. The biomass material is firstly preheated by high temperature air in preheater, and then fed into a fluidized bed gasifier. As the gasifying agent, the preheated air and steam generated from solar collector are fed into the gasifier. The high temperature bio-gas after removed the ash and char is fed into the heat exchangers (HX-1, HX-2 and HX-3. Utilizing the sensible heat of bio-gas to preheat the air and produce domestic hot water. Moreover, the purified biogas is fed into the internal combustion engine (ICE for electricity generation. The jacket water from the engine is used to provide the heating load for the building. The LiBr-H2O absorption is driven by waste heat from ICE flue gas, in which provides cooling/heating for users. After transferring the heat to domestic hot water in the heat exchanger (HX-5, the exhausted gas is released to the atmosphere at a temperature of 120.

4 Figure 1. Schematic diagram of the BCHP system coupled with biomass and solar energy 2. Energy analysis According to the first law of thermodynamics, the building cooling, heating and power system follows the conservation of energy. The system energy balance equation is expressed as: Qb Qs P Qc Qd (1 where Q b is the input energy capacity of biomass, kw; Q s is the input solar energy, kw; P is the generating electricity of the internal combustion engine, kw; Q c is the cooling capacity of the absorption, kw; Q is domestic hot water of the heat exchangers, kw. d The primary energy efficiency is selected as an indicator of the thermodynamic performance for the BCHP system, which can be defined as: P Qc Qd 100 % Q b Q b b s s W Qc Qd 100 % m LHV Q (2 where m b is the flow rate of biomass, kg/h; LHV b is the lower heating value of biomass, kj/kg.

5 3. Environmental analysis In addition, in order to reveal the advantages of the biomass and solar energy based BCHP system, it is imperative to analyze and compare the proposed system with the conventional separated system in terms of environment performance. Especially, the impact of CO2 emission, CO2 emission reduction ratio is defined as: ( m ( m CO2 ERR ( m CO2 sep CO2 B CO2 sep 100 % ( m CO2 B 1 100% P Qd P Qc ( CO 2 sepw ( CO 2 sep Qd ( CO 2 sep COP sep,c (4 where ( W d CO 2 sep, ( Q c CO 2 sep, ( Q CO 2 sep are the CO 2 conversion factors for the separated system of electricity, heating and cooling, respectively; COP SP,c is the coefficient of performance of electrical refrigerator. 4. System and biomass parameters The typical hotel building is located in Shanghai City, the area of building is about 8000 m 2. The cooling load is 1200kW, the heating load is 1100kW, the heating demand for domestic hot water is 115kW. The electricity demand for the building is 515kW. In addition, selecting the rice husk as the biomass feedstock, the properties of biomass is listed in Table 1. And the parameters of proposed system are shown in Table 2. Table 1. Characteristics of biomass material Character Value (% Character Value (% Ultimate analysis (db Proximate analysis (db Carbon Volatile matter Hydrogen 4.97 Fixed carbon Oxygen Ash Nitrogen 0.46 Moisture Sulfur 0.20 HHV (MJ/kg Table 2.Key parameters of the BCHP system Item Value Item Value Gasification temperature ( 900 Gasification pressure (MPa 0.1 Solar collector temperature ( 400 Solar collector efficiency (% 60 Compression ratio of ICE 9 Exhaust pressure of ICE (MPa 0.12 Exhaust gas temperature ( 450 Jacket water temperature ( 87 Mechanical efficiency of pump (% 99 Isentropic efficiencyof pump (% 75 COP c of LiBr-H 2 O absorption 1.2 COP c of hot water absorption 0.7 COP h of LiBr-H 2 O absorption 0.9 COP h of hot water absorption RESULTS Table 3 shows the performance results of the BCHP system, the BCHP system efficiency can reach more than 60%, in both cooling and heating conditions. For the extra load that the system couldn t afford for the building can be solved by the following solutions: the extra 0.6

6 electricity needed can be transformed by the electricity grid, the extra heating load can be afforded by the bio-gas boiler, and the extra cooling load can be afforded by the electric. These measures can be considered as the supplementary for the BCHP system, which would contribute to increase the performance of the overall system. Table 3.Calculation results of the BCHP system Item Cooling Heating Input Biomass energy (kw Solar heat (kw Output Electricity (kw Domestic hot water (kw Cooling generation (kw Heating generation (kw System performance Overall energy efficiency (% CO 2 emissions reduction ratio (% CONCLUSIONS In this study, a feasible BCHP system coupled with biomass and solar energy is proposed. The overall energy efficiency of the BCHP system is around 60%, and the unique advantages of the proposed system exists the CO2 emissions reduction. Therefore, the efficient utilization of renewable energy has an unique advantage compared with fossil fuels. The proposed system will provide a new idea for the integration with solar energy and biomass energy. ACKNOWLEDGEMENT This study is supported by the National Natural Science Foundation of China (NO and the International Science & Technology Cooperation Program of China (NO. 2014DFE REFERENCES Angrisani G, Bizon K, Chirone R, et al. Development of a new concept solar-biomass cogeneration system. Energy Conversion and Management, 2013; 75: Bahadori A, Nwaoha C. A review on solar energy utilisation in Australia. Renewable & Sustainable Energy Reviews, 2013, 18(2:1-5. Baratieri M, Baggio P, Bosio B, et al. The use of biomass syngas in IC engines and CCGT plants: A comparative analysis. Applied Thermal Engineering, 2009, 29(16: Basu P. Biomass gasification, pyrolysis and torrefaction: practical design and theory. Academic press; Calise F, d Accadia M D, Vicidomini M, et al. Design and simulation of a prototype of a small-scale solar CHP system based on evacuated flat-plate solar collectors and Organic Rankine Cycle. Energy Conversion and Management, 2015; 90: Ellabban O, Abu-Rub H, Blaabjerg F. Renewable energy resources: Current status, future prospects and their enabling technology. Renewable & Sustainable Energy Reviews, 2014; 39: Gerssen-Gondelach S J, Saygin D, Wicke B, et al. Competing uses of biomass: Assessment and comparison of the performance of bio-based heat, power, fuels and materials. Renewable & Sustainable Energy Reviews, 2014; 40: Jing Y Y, Bai H, Wang J J. Multi-objective optimization design and operation strategy analysis of BCHP system based on life cycle assessment. Energy, 2012, 37(1:

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