In table 1 the selected building applications and energy efficiency standards are described.

[7] Coefficient of Performance (COP) = cooling or heating output (kW) divided by

electrical input. The only electrical input is 4 small circulation pumps and internal controls. COP in conventional compressor-based chillers and packaged air conditioning units is usually stated as cooling capacity (kW) divided by compressor electrical input. Since the Millennium MSS air conditioning doesn’t have a refrigeration compressor, COP is stated here as annual cooling/heating energy delivered divided by total electrical input of the pumps and internal controls.

Fig 1. Millennium MSS Air Conditioning system heating and cooling device The example below shows one of the two barrels discharging cooling.

[8] chillii® Solar Cooling System

The analysed solar driven chillii® Solar Cooling System of the Solar Next AG has been set up and installed as a test facility to cool their office building in Rimsting. This system includes a market available 15 kW LiBr absorption chiller (ACM), two 1 m3 hot water storage tanks, one 1 m3 cold storage tank, 37 m2 CS-100F flat plate collectors and 34 m2 TH SLU1500/16 solar vacuum tube collectors all facing south with an inclination of 30°, a 35 kW EWK wet recooling tower (Figure 1). For the distribution of the cooling energy chilled ceilings and fan coils are used with 16°C supply and 18°C return temperature and an automated supply temperature increase for dew point protection. An auxiliary heater is integrated in the system, but not considered in the present analyses.

[10] Introduction

The use of renewable energy in buildings is a very important challenge in order to decrease their primary energy consumption. In South of Europe, most of buildings, especially tertiary ones, need active cooling in summer; thus the set up of the solar cooling technology can often represents an important way to save fossil energy. Solar cooling technologies already exists and have shown their effectiveness at the demonstration stage. Nevertheless, a certain number of technical and economical barriers actually exist and prevent a larger set up of the systems.

[11] From the two groups in Fig. 2 the reverse result is obtained. But this is an effect of the scatter (e. g. the AAtmin value is lower than zero for AtACE=29K, which is physically not possible). The ‘real’ characteristic equation (derived from ideal data without any scatter) should be steeper, leading to positive values of AAtmin and an increased slope.

[12] Conventional AHU, whose layout and thermal cycle are shown in [1].

• Standard open-cycle desiccant system (DEC), according to the layout shown in Figure 1.

• Standard DEC provided with a desuperheater.

• Standard DEC modified with the use of an enthalpy recovery wheel, which operates a pre-dehumidification of the process air by releasing a certain fraction of its vapour content to the exhaust air.

For all the thermal cycles related to the DEC systems, the use of solar energy to assist regeneration will also be investigated (solar assisted DEC): the AHU is the same as in the previous points, but a solar section with a back-up heater is adopted to produce hot water for regeneration purposes. In order to test the sensitivity of the results to the size of the solar section, different values of the collector surface will be considered, corresponding to an annual solar fraction F ranging from 0 to 1. In order to compare the energy and exergy performance of the systems, we have considered a case study represented by the ventilation and the air-conditioning of an enclosed space with a latent

[13] Governing principles and parameters

So as to establish appropriate dimensioning guidelines, we will start by characterizing the governing principles and their link to amplitude-dampening along the pipes. We therefore will base on the simplified and analytically resolved case of a constant airflow subject to sinusoidal temperature input, with explicit treatment of diffusive heat storage into the soil [2], which yields following main insights:

• As long as the soil layer around each pipe is at least that thick, heat charge and discharge

around the pipes naturally extends over a penetration depth 8 which depends on the oscillation period:

[14] Koller, Zetzsche, Brendel, Muller-Steinhagen: Design and Operation of a small Ice Storage, 2nd International Conference Solar Air-Conditioning, Oct. 18th/19th 2007, Ostbayerisches Technologie- Transfer-Institut e. V., Regensburg, Germany, p. 359-364

[15]

[16] y is the response of the phenomena • xi is a factor or parameter influencing the phenomena • a0 is a constant effect,

• ai is the effect of single parameter

• aij is the effect of double interaction,

• aijk is the effect of triple interaction

It is evident that the number of effect to be determined will need the same number of experiments. In order to estimate the effects, each parameter varies between an upper and lower limit, so each parameter has two levels [2]. In our case we have 4 parameters; each one varying between 2 limits which mean we have 24 effects to be determined and 16 combinations (experiments) are then needed.

The following range of the parameters was considered:

• Outside temperature T1: [25, 35] [°C]

• Outside humidity ratio w1: [11, 14.5] [g/kg]

• Regeneration temperature T8 [55, 75] [°C]

• Regeneration humidity ratio w8 [10; 15] [g/kg]

Outside temperature and humidity ranges correspond to the most of the European climates (except some humid Mediterranean climates) and match with the domain of application of desiccant cooling (e. g. moderately hot and moderately humid climates). The upper limit of regeneration temperature domain is consistent with solar application with temperature not exceeding 75°C while