This paper presents the design of a solar-biomass hybrid system for air-conditioning。 Three possible overall system configurations were first considered, based on which the most suitable configuration considered for the design。 The principles of component selection of a flat plate solar collector with storage, biomass gasifier with boiler, and a LiBr–H2 O absorption system has been described, and the design criteria for the proposed system elaborated。 The design was to satisfy a cooling load of 4。5 kW, and solar to auxiliary heat ratio of at least 0。7。 Simulation at various solar collector size and storage tank volume for the weather conditions at Bangkok indicate the most suitable design and specifications for the size/capacity of the solar collector, storage tank, set point temperature of the absorption generator and biomass-gasifier boiler。86011

1。Introduction

To address the global warming and energy crisis issues, using renewable energies appear as an interesting alternative。 As the ambient temperature increases, the need for air conditioning will dramatically increase。 To reduce the electricity consumption and CO2 emissions, solar air conditioning systems seems appropriate and vital [1]。

The two main solar air conditioning options are electrical and thermal driven systems。 The electrical systems require the  use of photovoltaic panels; these are still expensive and have low efficiencies。 The thermal driven systems are pided into heat transformation systems and thermo-mechanical processes。 Most thermo-mechanical processes are in laboratory scale and they use engines to drive a compressor instead of an electrical motor。 The heat transformation processes are pided into close and open cycles, and they may use liquid or solid sorbents。 Almost all solar cooling systems are closed cycle liquid sorbent systems。

Solar driven system offers a good model of a clean process for sustainable technology [2]。 The two driving energy sources for the conventional solar cooling systems are without auxiliary heat source and with fossil fuel auxiliary heater。 As solar energy is inter- mittent, the solar cooling system without auxiliary heat    source

∗ Corresponding author。 Tel。: +66 897 672 533; fax: +66 2 549 3432。

E-mail addresses: prasartkaew@yahoo。com, boonrit p@rmutt。ac。th (B。 Prasartkaew)。

cannot be continuously used, especially at night, and so its reli- ability is low。 Almost all solar cooling systems use gas (LPG/CNG) as an auxiliary heater [3]。 Thus, a conventional solar cooling system has three major sub-systems – absorption chiller, solar water heat- ing system and backup/auxiliary heating sub-systems (renewable or fossil fuel based)。

A solar-biomass hybrid cooling system has been proposed, which is a completely renewable energy based system [3,4]。 This paper first identifies the optimal system configuration (among three options), and then presents the design procedure of a solar- biomass hybrid  cooling  system  for  the  chosen  option。 Section 2 describes the possible system configurations of solar-biomass hybrid absorption cooling system (SBAC)。 Section 3 presents the mathematical model and simulation inputs used for the design of the SBAC system。 Section 4 presents the selection of the best sys- tem configuration。 Section 5 presents the design of a solar-biomass hybrid air-conditioning system。 Finally, the conclusions are given in Section 6。

2。Possible system configurations

As demonstrated in Fig。 1, most conventional solar cooling systems use fossil fuel as an auxiliary heat source, and so their oper- ating cost and emissions are high。 This research proposes biomass energy as a cheaper (or free if it is the waste material) auxiliary heat source to address the above issue。 Thus, the main difference of the proposed system as compared to the conventional system is