**8.3. Auxiliary systems**

A first approach to the cost of the entire air-conditioning system is based on the area of solar incident energy. The buildings have large area, but only the roof is useful for installation, but the thermal gain from wall and window is bigger than the size the roof solar-collected energy. Then, the strategy for a quick viability evaluation is to evaluate the available solar roof in square meters and compare it with the value for required air-conditioning expressed in kW. If this value ratio is close to 1, then a detailed analysis for selection of the parts must be followed, if the value is lower than 0.5, then there is no opportunity for this roof technology because the solar loads and wall conduction are bigger than the total energy than a solar roof air condi-

There are some parts in the solar concentrator, which determines the total cost of this part. Installation is the biggest part [58], and it represents 38% of the investment, followed by storage thermal tank with a 24% of the total cost, and just a 14% from the solar thermal collector. The others are the cost from pipes with a 8%, thermal fluid with a 1%, pumping and controller

For the air-conditioning systems, there are just a few certified companies to build these devices. People have lack of information about the uncommercial devices. Considering than a conventional air-conditioning by compression is based on an evaporator, a condenser and a compressor, two of those heat exchangers are the same for an absorption cycle, but the metal is so different. In compression systems, aluminum and copper are used for the cycle. In an absorption cycle, the metal for the heat exchanger is stainless steel to avoid corrosion problems. This is a disadvantage for the cost because the cost of the stainless steel is higher than copper. Nowadays, the SS 304 has an average price about 1.62 USD by pound; aluminum has an almost constant price

about 1.58 USD by pound, and copper has unstable price around 2.87 USD by pound.

tional can exchange.

62 Sustainable Air Conditioning Systems

**8.1. Solar concentrator system cost**

**8.2. Thermodynamic cycle cost**

**Figure 10.** Cost for solar concentrator parts.

8% and fixing and mounting with a 7% (**Figure 10**).

The auxiliary systems are the installation and control between the solar concentrator and the thermodynamic cycle. The cost is based on the electronic device to control the pump as function of temperature, solar irradiation, and the instantaneous load into the building. The design is not commercial today, but it is not expensive because the energy for the operation has shown consumption about 1% of the total system by connection with inversed devices and solid-state circuits. The controller must be designed for the power of the pumps, those into the thermodynamic cycle and a circulator in the solar concentrator on the roof.

Electronic devices are really cheap based on Arduino © experiences, and these represent no more than 300 USD, and installation by a professional technician must be considered and the time for the installation by several hours may be expensive, as function of the building location, security conditions, roof access facilities. Then, in agree with the local cost by specialist cost hour, the auxiliary system may represent even a 30% of the installation device cost.

Finally, the total cost must be under a projected value for the lifetime of the roof air-conditioning system. This means that the cost must be compared with a cost for the actual technology and the total cost, for example, a storage tank of 243 L used by day into the roof air-conditioning system by the next 12 years [59] (**Figure 11**).

In the near future, the air-conditioning must be by solar, from the roof energy from thermal, photovoltaic, or a combination of those [60].

**Figure 11.** Total cost with actual technologies for air-conditioning [59].
