30 May 2005
Waste water with a temperature below 60°C is generally discharged because its temperature is
too low for use as an energy source. If such waste heat can serve as an energy source, it can
dramatically improve energy efficiency. Heating and hot water supply systems in hotels and hospitals
can operate using waste heat, although air conditioning, rather than hot water supply, dominates
energy consumption in administrative buildings. The invention of a new technology for exchanging
low-temperature heat sources into cooling capacity for use in air conditioning is essential to
encouraging the spread of CHP systems.
We are therefore developing a hybrid air-conditioning system driven by low-temperature waste
heat at about 60°C. Specifically, we have established a following technology: low-temperature waste
heat driven absorption system. In detail, a two-stage absorption cycle was selected which satisfied the
target of a refrigeration cycle COP of 0.4 with minimum heat transfer area requirements. To
demonstrate the two-stage absorption cycle driven by 60°C waste heat, the heat transfer area required
by the heat exchangers were calculated using a cycle simulation software program. A
proof-of-concept machine was designed and constructed based upon the results of the calculations.
Operation of the proof-of-concept machine verified that the target cooling capacity and COP can be
achieved utilizing the two-stage absorption cycle under 60°C waste heat conditions.