ABSTRACT Economic and energy-saving characteristics of cogeneration systems with microturbine and desiccant airconditioning units are investigated on system operational planning. An optimization approach is adopted to rationally evaluate these characteristics. In this approach, on/off and rated/part load status of operation of equipment and energy flow rates are determined so as to minimize the hourly energy charge subject to satisfaction of energy demand requirements. In this optimization problem, performance characteristics of the microturbine and desiccant air-conditioning units are modeled in consideration of the influence due to ambient air temperature. Moreover, the influence due to ambient air humidity is also considered in the desiccant air-conditioning unit using the psychrometric diagram. The implementation of the numerical analysis method, discussed in this paper, to two cogeneration systems, clearly shows economic and operational benefits of using desiccant air-conditioning. NOMENCLATURE A : coefficient for unit conversion from J to Wh, Wh/J a : latent heat of vaporization of water, kJ/kg B, C : coefficients of proportion, kg/m b : specific heat at constant pressure of air, kJ/(kg·°C) c : specific heat of water, kJ/(kg·°C) E : electricity, kWh/h F : natural gas consumption, m 3 /h h : specific enthalpy, kJ/kg J : hourly energy charge, yen/h m : mass flow rate, kg/h p, q, r, p′, q′, r′ : performance characteristic values of equipment Q : heat flow rate, kWh/h s : sensible heat factor t : temperature, °C u : input energy flow rate of equipment, m 3 /h, kWh/h v : velocity of process air, m/h x : absolute humidity, kg/kg y : output energy flow rate of equipment, kWh/h δ : binary variable expressing on/off status of operation η c : evaporative effectiveness of EC2 η e : effectiveness on regeneration air side of SHW η s : effectiveness on process air side of SHW ϕ : unit cost of energy charge, yen/m 3 , yen/kWh ( ), ( ) : lower and upper limit
